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|Tail of Planet X|
Planet X has been appearing on SOHO and the Stereo Ahead for some months now, in approximately
the 4:30 o'clock position. But sometimes something bright with a tail shows up in other places, above the
Sun, or to the left of the Sun. If this is Planet X, why is it moving around so much?
ZetaTalk Explanation 1/2/2010: When the Winged Globe or the Red Cross appears to the lower
right on the Sun, this is the Planet X corpus. We have explained that the tail is vast, the Moon
swirls swinging to either side of Planet X by 5 million miles, but the tail itself swings further than
that. During the hour of the pole shift, when Planet X is a mere 14 million miles from the Earth,
the tail is whipping the Earth, depositing hail and red dust. The tail itself can catch the light,
reflecting this to Earth, in what appears to be a blaze of light with a tail drifting away. It is
charged, so clings to itself in places, so is thicker in some places than others, just as an electrical
charge can raise the hair on your head. As Planet X turns its charged tail toward the Earth,
increasingly, such sudden appearances will increase, consternating NASA.
SOHO is approximately 1.5 million miles from Earth, stationary, sunside of the Earth which is 93 million
miles from the Sun. Just how far does that tail spread? During the 2002-2003 CCD imaging of Planet X
in the night sky, as it was inbound, light clouds around the body of Planet X were often noted.
- And debris in the tail of Planet X is certainly inbound lately, in the form of fireballs. Fireballs on on the
increase, showing a sharp increase since 2005.
- 2005 -466
2006 - 515
2007 - 587
2008 - 726
Indeed, in this past month alone, the fireballs hitting the press were most certainly not part of the Gemini
meteor show. Fireballs are occurring year-round, screaming across several states or provinces, lately in
California on December 17, Hawaii on December 11, and Minnesota on December 12.
- Picture of the Day - Fireball Above Mojave Desert
December 17, 2009
- Monstrously bright, this fireball meteor lit up the Mojave Desert sky.
- Colored Fireballs Light up Evening Sky
December 11, 2009
- Yoder said he found it hard to believe there has not yet been an explanation for what he
saw, much like the loud noise over Kalaheo reported by residents in May of this year. "I've
seen meteorites all my life," he said. But added that what he saw was much different. "It
was either a gigantic asteroid or one of the biggest meteorites I have ever seen."
- Bright Blue-Green Flash Turns Night into Day
December 12, 2009
- A brilliant bright blue-green flash lit up a huge portion of the sky from western Minnesota
to eastern Wisconsin Friday night -- the event was enough to make the night sky
momentarily seem like daylight. It was almost certainly a fireball meteorite, say
meteorologists and local amateur astronomers. In fact, the earth is currently orbiting into
that portion of space strewn with those extraterrestrial rocks that produce the Geminid
meteor showers every year at this time.
Russia surprised the world by announcing they were planning to send a rocket aloft before 2029, to
deflect a Near Earth Orbit asteroid expected to pass close to the Earth.
- Russia may send spacecraft to knock away asteroid
December 30, 2009
- Russia is considering sending a spacecraft to a large asteroid to knock it off its path and
prevent a possible collision with Earth. Anatoly Perminov said the space agency will hold a
meeting soon to assess a mission to Apophis. It would invite NASA, the European Space
Agency, the Chinese space agency and others to join the project once it is finalized.
"Apophis is just a symbolic example, there are many other dangerous objects we know
little about," he said.
Per the Zetas, there is another agenda afoot.
ZetaTalk Explanation 1/2/2010: This is an attempt to reassure the populace that the establishment
intends to do something about incoming debris. The timing of the release, the article, is an
attempt to get ahead of what the establishment assumes will be increasing fireballs, visible
swarms of debris in the sky. The populace is to say to themselves that help is on the way, the
establishment will address the issue, when in fact nothing can be done. Unless debris is in an
Earth orbit, like the space junk man leaves behind during ISS maintenance or satellite disposal, it
cannot be targeted.
Nevertheless, this subject was all the rage back in the 1990's, when deflecting NEO asteroids was
under serious discussion, such organizations as Spaceguard UK were looking for solutions. The Zetas
were debating astronomers and others on the sci.astro Usenet in 2001. Despite the Zetas telling them
that deflecting an asteroid was not possible, they were interested in the Zetas perspective.
- ZetaTalk and Spaceguard UK
July 21, 2001
- I'd be delighted to have ZetaTalk included! You absolutely have permission to include the existing
ZetaTalk you've included below, as well as the NEW ZetaTalk given in response to your
comments :-). Since these topics are also being addressed on sci.astro, during the current debates
the Zetas are engaged in there, I am assuming it would also be OK to post this to the sci.astro
Jonathan TATE wrote:
> Dear Sir or Madam, Spaceguard UK is the largest independent
> organisation in the world concerned with the NEO impact hazard. We
> have taken the subject to both houses of Parliament in the UK, and
> secured the establishment of the government Task Force that you will
> be aware of. The quarterly edition of "Impact", our magazine is due,
> and I would like to include an item on the article that you have
> published. I would be grateful is you could comment on the notes
> below. Thanks for your time, and I will take a nil response as
> acquiescence to publish the item as it stands.
> Yours J Tate,
> DirectorSpaceguard UK
> The aim is to deflect an object, not to "vaporise"
> it. Firstly that would require enormous amounts of energy - far beyond
> our current capabilities, and secondly, destruction would simply
> convert a cannon ball into a cluster bomb.
> Deflection is possible - see Ahrens and Harris "Deflection and
> Fragmentation of Near-Earth Asteroids" p. 897, Hazards Due to Comets &
> Asteroids ed. T Gehrels 1994 and many other articles in the same
> source document.
> There is a clear misunderstanding of the mechanism of coupling the
> energy from a nuclear explosive and an NEO. The aim is to use the hard
> radiation from the detonation to vapourise material on and below the
> surface of the NEO to then cause outgassing or spalling of
> material. This "jetting" effect will cause an equal and opposite
> reaction slightly modifying the NEO's trajectory.
Jonathan Tate was reacting to the ZetaTalk, below.
ZetaTalk Explanation 7/15/1996: Recently the media and Internet message boards have been
alerting the populace to the presence of what is termed near-miss asteroids. Discussion ensues on
how to deflect them should they threaten to impact the Earth, as though deflection would be
possible. Does mankind now have the means to deflect such large, rapidly moving objects? Such
a deflection would require a precisely placed explosive device of sufficient strength to vaporize
the asteroid. Disintegration would be required because deflection is not possible in space. This
statement will meet with vehement objection, especially from the arm of the establishment which
seeks only to deflect panic in the populace. It is not a collision with an asteroid which will shortly
devastate Earth, it is the passage of the monster Planet X, ever drawing closer. Nor will
deflection of the trash in this giant comet's tail be possible - boulders as large as trucks thumping
to Earth on occasion and the peppering of red dust and gravel. Deflection of these few boulders
is not possible either, as they are shrouded in the swirling dust of the tail, and only visible just
All the sudden upsurge in talk about the dangers asteroids present, and all the talk in the late
1990's about reviving the Star Wars program to address this threat is not because something can
actually be done. Short of making practical plans to survive the coming pole shift while hunkered
down on the surface of the Earth, mankind has no options, and those in the establishment who
talk up asteroid deflection possibilities know this. They are simply buying themselves time by
pushing the point where panic in the populace gets heated as far out as possible. Hopefully, the
panic button won't be hit until those members of the establishment are safely away in their well
stocked enclaves, and then the rest of humanity, who has been reassured that their government
can protect them, be damned.
Near Earth Orbit asteroids are on the increase. Per the Zetas, this is due to the gravity attraction and
magnetic disruption caused by the presence of Planet X.
However, the Zetas say no asteroid will be allowed to impact the Earth, as the Council of Worlds has
decreed that this should be prevented. They have plans for Earth, and their plans do not include its
San Diego Quakes
San Diego is in the center of a bow formed by bending the tip of the Aleutian Island toward the tip of
Mexico. The N American Plate has a flat top and cannot roll to adjust when the Atlantic widens at the
middle, at the Equator. Thus, the bow.
ZetaTalk Explanation 2/10/2006: The giant plates of N America and Eurasia are locked against
each other, unable to rotate against each other due to their shape. This creates a diagonal stress
on the N American continent where New England is pulled to the east while Mexico is pulled to
There were 46 quakes greater than 2.5 between December 30, 2009 and January 1, 2010 in the Baja
east of San Diego. A 5.8 quake occurred east of San Diego on December 31, 2009. The area of the
quakes is on the San Andreas, and therefore right on a fault line, but nonetheless this raises the
possibility of the rip up toward Mammoth Lake, California being in the near future.
ZetaTalk Comment 9/9/2006: We have chimed in with Scallion on suspecting that a rip will occur
from San Diego up toward Yellowstone, as there is a fault line there. Why would this rip, in a
manner that would disrupt Mammoth? As we have stated in detailing the Earth Torque, wherein
New England is pulled toward the East and Mexico toward the West, pulling the N American
continent in a diagonal, fault lines will not be stressed in their traditional ways, but in new ways,
during the coming months. New Madrid is an example. East of the Mississippi, going up, West of
the Mississippi, going down. In a similar manner, the fault line from San Diego to Mammoth, and
on up toward Yellowstone, will find the land South going West, with Mexido, and North staying
with the land above this fault. Thus, should such rupture take place, in stages, evacuate
The original ZetaTalk prediction on this rupture places it in the timeline "some months" before the pole
shift, a clue of sorts to a timeline when this rupture occurs.
ZetaTalk Prediction 2/15/2000: Of course all volcanoes will explode, as this is going to be a very
severe pole shift. What about the months and years preceding the pole shift? It is no secret that
Mammoth Lake and the caldera of Yellowstone are warming up, and the populace has been
prepared for these occurrences by the movie Volcano where there, in the middle of LA, lava is
bubbling up. In fact, there is a fault line running from the approximate San Diego/LA area, up
into the Sierras, and this is liable to rupture rather violently during one of the quakes that
precedes the pole shift by some months. Volcanic eruptions from that area in the Sierras can be
Looking closely at a map of the area, it can be seen that there is a rift running from San Diego directly
north to the Mammoth Lake area. This confirms what the Zetas have said about a hidden fault line.
ZetaTalk Explanation 10/6/2007: We have repeatedly warned that the US southwest was going to
undergo a bowing stress, a situation that would last until the N American continent adjusted by a
diagonal rip along the extended New Madrid Fault line, which includes fracturing from New
England through the Midwest and down into Mexico. Until that adjustment occurs, Mexico is
tugged to the west, causing a bow to form along the West Coast. The bow causes compression at
its center, at the San Andreas Fault line near San Diego, and expansion inland. This bow is what
caused the Utah mine collapse, as we explained at the time. Indirectly, this bow is what caused
the Minneapolis bridge collapse, as it forces the St. Lawrence Seaway to open, causing
adjustments all the way to the Black Hills of S. Dakota.
San Diego is lowlands, as the nearby presence of the Salton Sea shows. This area will compress
more than land to the north, as the rock is now less thick as it has proved to be pliable in the
past, and distended. San Diego is thus due for a grinding action, a tumbling action, as the bow
comes under increasing stress. When the New Madrid Fault line adjusts, the stress on this bow
will relax but another nightmare will emerge - new adjustments along the San Andreas Fault
line. Now the western half of the N American continent is free to jut to the west, at a diagonal, so
slip-slide all along the San Andreas Fault line will occur for some time. We have mentioned that a
rip will occur from San Diego up through Mammoth Lake of California and on up toward
Yellowstone at some point. As one can see from a topographical map, there is a rift along this
path, where ripping has occurred before. This too is awaiting the San Diego area, which will by
that time be an almost unlivable area.
You received this Newsletter because you Subscribed to the ZetaTalk Newsletter service. If undesired, you can quickly | 0.834211 | 3.205029 |
Sh2-112 (near the bottom) and Sh2-115 (upper part of the image) are faint emission nebulae catalogued by S. Sharpless in 1959. They are located in Cygnus, just 1 and 2 degrees northwest of Deneb, the brightest star of this constellation. The brightest parts of the Sharpless nebulae can be glimpsed visually, but it takes a dark sky and a decent rich-field telescope.
Abell 71 is the designation of the small round patch of emission nebulosity near the upper edge of the photo, it actually shows two extensions or "arms". Originally it was classified as one of four planetary nebulae in Cygnus by G. Abell in 1955. Subsequent studies question this because it emits almost no greenish [OIII] light characteristic of a planetary nebula, so it could simply be another HII region, although it is still cataloged as PN in most databases.
Sharpless 112, Sharpless 115 and Abell 71, which this image is part of. | 0.902667 | 3.129624 |
The highest resolution images ever taken of the Sun’s surface were released last week, showing in stunning detail, the planet’s life source.
The National Science Foundation (NSF) published the images on Wednesday, captured by the world’s largest solar telescope, The Daniel K. Inouye Solar Telescope (DKIST).
DKIST director Thomas Rimmele said in a press release that the extraordinary images are just the beginning. “These are the highest-resolution images and movies of the solar surface ever taken. Up to now, we’ve just seen the tip of the iceberg.”
The new DKIST telescope was built on Haleakalā in Maui to study the Sun. So far, the detailed images have superseded expectations, and according to Rimmele, will help to “unravel the Sun’s biggest mysteries.”
The sections of orange seen in the images are convection granules the size of Texas. The release of the images marks the beginnings of a 50-year study covering two of the Sun’s 22-year solar cycles. Despite DKIST’s construction starting in 2012 and that it isn’t fully operational yet, the captured images show promising results for the scientific community.
On January 23, DKIST’s Visible Spectro-polarimeter (VISP), came online. Space.com reported that VISP records precise measurements of light. “VISP splits light into its component colors to provide precise measurements of its characteristics along multiple wavelengths.”
All instruments are expected to be fully operational by mid-2020.
Astronomer Jeff Kuhn from the University of Hawaiʻi at Mānoa’s Institute for Astronomy is hopeful for the future studies of the Sun. “It is literally the greatest leap in humanity’s ability to study the Sun from the ground since Galileo’s time.”
Once fully operational in July, DKIST’s sensitivity to light and high resolution capabilities will allow the Sun’s magnetic field to be probed. The studies will shed light on what drives space weather and the Sun’s release of charged particles that interfere with space technology like satellites and power grids.
“On Earth, we can predict if it is going to rain pretty much anywhere in the world very accurately, and space weather just isn’t there yet,” Matt Mountain of the Association of Universities for Research in Astronomy said.
“Our predictions lag behind terrestrial weather by 50 years, if not more. What we need is to grasp the underlying physics behind space weather, and this starts at the sun, which is what the [NSF] Inouye Solar Telescope will study over the next decades.” | 0.824527 | 3.2911 |
The first living organisms sent into space — some bacteria and the humble fruit fly – returned from their trip to little fanfare and under less than comfortable circumstances. Instead of a relatively nice trip inside a space shuttle, the bacteria and fruit flies were stuffed inside the nose cone of a WWII-era V-2 rocket — the spacecraft of choice in the early days of microgravity research.
We may be a long way from the days when scientific experiments were precariously hurtled through space in the nooks and crannies of repurposed missiles, but science in space has not quite gotten to the level of Arthur C. Clarke’s sweeping vision in 2001: A Space Odyssey. There are no moon bases, nor are diseases cured by some panacea treatment only available in microgravity. Given the advent of computers, cell phones, CRISPR and other advanced technologies during the same timeframe, why does space science seem to be advancing less quickly?
Research: The space exploration gap
Microgravity researcher Dr. Carl Carruthers, who has put his own research payloads into space, believes one reason behind this may be that scientific research in space has largely been treated as an afterthought. For example, Projects Mercury, Gemini and Apollo focused all design efforts on creating a safe spacecraft that could accomplish a set of moon landing goals. Then, if restrictions allowed, science experiments were made to fit into any nooks and crannies that could be found.
The Space Shuttle had storage lockers in the middeck area for the crew’s clothes and personal items, among other things. Seeing that there were empty lockers, NASA decided to use them to accommodate microgravity research, even though the lockers were not originally designed for that. While there were eventually dedicated science missions in pressurized or unpressurized modules located in the Shuttle payload bay, like the Spacelab, they adopted the same locker system found inside the Shuttle — which has since been adopted and utilized on the International Space Station (ISS) even today.
Space stations, on the other hand, have historically been designed with scientific research in mind. Skylab — the only space station that the United States has ever operated exclusively — was a 1970s space vehicle dedicated (mostly) to scientific research. It paved the way for the ISS, the crown jewel of space science. In 2005 the US-portion of the ISS was designated by NASA as a national laboratory. Yet in twenty years, the ISS has seen about 1700 research payloads, of which only 515 were classified as biology or biotechnology research, and most of which were one-offs. Many of those projects could be better classified as what some might consider “promotional” science. The amount of rigorous science that has been done on the ISS remains surprisingly low.
Until recently, the pace of science on the ISS was slow. Beyond the challenge of getting your experiment into space, research design was guided by outdated hardware and old ways of thinking. Instrumentation was very large. Experiments were one-offs, with hardware built specifically for each individual experiment. Repeating experiments, and replicating results, becomes a difficult endeavor in such an environment. Only in January 2019 did humanity even achieve the milestone of growing plant life on another world — via the cotton seeds on China’s Chang’e-4 Lunar far-side payload.
“Imagine being in your lab, and every time you wanted to perform an experiment you had to build a piece of hardware for it,” say Carruthers. As recently as 2011, he remembers his frustration with hardware that was nowhere close to functioning like what he routinely used in his Earth lab. “There are several established standard formats found in Earth lab hardware. Microplates, pipettors and centrifuge tubes, for example. Why hasn’t anybody ever tried to make a space lab that’s more analogous to a lab found on Earth’?” he thought.
It was about this time when Carruthers met Jeff Manber, CEO and Co-Founder of NanoRacks. In NanoRacks, he saw a company that was innovating the way scientific research in space was thought about and conducted.
Creating a space lab analogous to Earth labs
NanoRacks’ plan for standardized hardware and commercial access would more efficiently use space already dedicated for research on the ISS and reduce costs for researchers putting payloads into space. Approaching NASA with their idea, NanoRacks said they would pay for the hardware, the technology, and the safety process. All they needed in return was a trip (or few) to space. NASA agreed. The result? The NanoLab.
The NanoLab is a CubeSat-based plug-and-play research box. Highly volume efficient, NanoLabs were designed to fit into ISS’s EXPRESS Rack locker system, in essence subdividing the available research real estate on the space station. The smallest version of the NanoLab is only 10cm by 10cm by 10cm — the CubeSat 1U standard. The small research space is also more cost effective: the miniaturized electronics necessary for doing research with a NanoLabs are much cheaper than standard-sized electronics needed for typical spaceflight research. There are no radiation hardened computers or electronics for instance—the ISS’s environmental protection takes care of that. With the popularity of such cheap, readily-available microcontrollers such as the Arduino and Raspberry Pi, both about the size of a matchbox, costs are further reduced. This does not even take into account the recent boom in new, extremely small sensors and devices of all capabilities available from companies like Adafruit, Sparkfun, or even Amazon. And, the NanoLab’s plug-and-play nature (thanks to an integrated USB port) saves crewmembers time and facilitates near-real-time data transfer back to Earth.
To facilitate a protein crystal growth experiment, two 1.5U NanoLabs — each holding 6 microplates — were connected together. Photo credit: Carl Carruthers/NanoRacks.
The NanoLab turned out to be a truly transformative idea, yet it wasn’t completely removed from the one-and-done type of experiment that had plagued space science for so long. More standards — standards that researchers were familiar with — were needed to make the space lab more analogous to labs on the ground. And what could be more familiar than microplates?
Because they are a standard piece of earth-lab equipment, NanoRacks requires all their hardware be compatible with microplates, such as this Reactor Microplate, designed and manufactured and optimized by NanoRacks for use in their ISS Plate Reader. Photo credit: NanoRacks.
Building upon the versatility of and familiarity with microplates, NanoRacks decided that their hardware should have some ability to work with microplates. Their very first commercially available piece of equipment, a plate reader (which first arrived on the ISS in 2011 and is now on its second version) easily fit the bill and is itself a standard, familiar piece of equipment found in nearly every research lab on Earth. Next up, a microscope, also formatted for use with microplates, which NanoRacks has now evolved to its third iteration. Both pieces of equipment were a huge step toward providing researchers tools that they were familiar with, eliminating the need to learn new hardware. Both tools are also easy for Space Station crew members to use.
“All the research that you do on the space station is by proxy, either by a machine or a person,” says Carruthers, who ultimately joined as NanoRacks’ chief scientist in 2014. He notes that the person running your experiment “may or may not have any research or science background. And so, to even remove just one bit of that area of unfamiliarity or uncertainty of hardware used on the ISS, by making the research easier to adapt from ground based experiments, or more understandable, or more comfortable — it was a significant step to having … what you have in your lab [on the ground] for the space station.”
Importantly, NanoRacks has opted to keep their standards open source, such as the NanoLab form factor. “We’re into creating a real commercial ecosystem in low-Earth orbit,” says Adrian Mangiuca, NanoRacks’ Commerce Director. “And we don’t do that alone, we don’t do that with one commercial monopoly. We need a vibrant community of buyers, sellers, hardware, and service providers—that’s what makes any market sustainable.” Indeed, this was the root behind Manber’s decision not to patent the initial NanoLab models, and it has paid off on the ISS.
Other companies are finally catching on, and some have even built microgravity research units with form factors nearly identical to the NanoLab. The NanoLab standard developed early on by NanoRacks has taken hold in the broader microgravity research community, with ever more commercial hardware being built to meet researchers’ demands for microplate-ready tools. By remaining open and collaborative, NanoRacks is helping foster a space science community and ecosystem of services and hardware that is finally making gains.
Fruit flies, Boy Scouts, and Chinese payloads in space
NanoRacks’ efforts are paying off in tangible ways. Remember those unfortunate fruit flies crammed into the V-2 rocket nose cone on that first live organism payload flight? Thanks to NanoRacks’ standardized hardware and relationship with NASA, fruit flies — a great research model both on the ground and in space — are making it into space once again (and fortunately for them—back down to Earth as well). One NanoRacks customer, a prolific fruit fly researcher, was able to fly payloads three times in a single year — three times more, she wrote, than in all the years prior to that. She has since been able to build a much more sophisticated fruit fly space research program and regularly sends projects to the ISS.
“We were able to move this microgravity researcher ahead farther and faster than she had been able to before, which underscores the capabilities that we’ve been able to provide investigators, creating something that’s affordable and easily transferable,” remarks Carruthers.
NanoLabs have also housed some incredible science projects for Chicago’s Boy Scout Troop 209, which studied bacterial gene mutation in microgravity. A second troop used spectrometry inside their NanoLab to study how amyloid beta — the peptide responsible for amyloid plaques in the brains of Alzheimer’s patients — folds in microgravity. Both projects could have important implications for human health — both on the ground and in space. And NanoRacks’ support of students doesn’t stop there. Their spin off company, DreamUp, helps students from primary to post-doctorate realize their own microgravity experiments such as the world’s first genome editing experiment in space.
But perhaps the most significant scientific payload NanoRacks has flown is a collaborative project with scientists from the Beijing Institute of Technology. The research team created a microgravity-optimized PCR chip to study mutation in an immune system-specific area of the genome susceptible to damage from ionizing radiation like that experienced by astronauts in space. The result was a miniature thermocycler that is both portable and programmable — and that yielded equivalent or higher amounts of DNA than commercial thermocyclers. The study was published in the journal Acta Astronautica and represents the first commercial Chinese payload in history on the ISS — making NanoRacks the first and only entity, commercial or otherwise – to make this opportunity possible.
The formal handover of the Chinese payload to NanoRacks at the Space Life Sciences Lab in Cape Canaveral, Florida. Photo credit: NanoRacks.
Small effort, big gains
Clearly, a lot of progress has been made toward making the space lab more analogous to the Earth lab in the past few years, and NanoRacks has played no small part in those improvements. Despite the challenges that still remain for microgravity research, some truly significant work has been accomplished. With just a little more investment, Carruthers believes, much larger gains can be made.
“We’re close,” he says. “If we just opened it up a little bit more and we make available things that are even more familiar to the researcher, like automated fluid handling, if we made it only just a little bit easier, imagine how that would change the complexity, quality, and consistency of research done in space. Imagine what researchers could understand and produce – from biology to complex pharmaceuticals. NanoRacks is ready to be a keystone company in these efforts.”
Indeed, NanoRacks is collaborating closely with NASA to explore future commercial pathways to expanding the scope of space science. The Company was selected as one of nine to lead NASA’s LEO Commercialization Study, which yielded critical insights into the pathway toward expanding commercial activity in space. NanoRacks expects that insights gleaned from this endeavor will ultimately result in producing more sustainable, more affordable approaches to space science. With NanoRacks, NASA, and the space industry at large approaching sustainable, useful space science — and bioscience specifically — as a central theme and focus of exploration (rather than an expensive afterthought), those goals will become a reality, forever transforming space science.0 | 0.824145 | 3.371625 |
It’s called a pink super moon, but even though it’s not truly pink, it will be super. It also is called the grass moon or egg moon, and will come within about 221,851 miles of Earth.
The year’s only federally-recognized super moon rises Tuesday, scooting by Earth with a spark 15 percent brighter than an average-size full moon.
April’s full moon, dubbed the pink moon, grass moon or egg moon, closely coincides with its perigee — the nearest it gets to Earth in its monthly orbit — and will come within about 221,851 miles of the planet.
NASA Goddard Space Flight Center counts the closest moon of the year as a super moon. A NASA press release says Tuesday’s moon will be the biggest and brightest lunar display of 2020.
But astronomers have different definitions of super moons. Astrophysicist Fred Espenak gives the lofty title to full moons that come within 90 percent of the closest approach to Earth. That means the lunar swells of February, March and May are also considered super, according to Espenak.
And not everyone’s convinced the appearance of the moon as larger will be evident to most people.
"The angular diameter of a super moon appears about 7 percent bigger than that of an average-size full moon, and about 14 percent bigger than the angular diameter of a micro-moon or mini-moon (the year’s most distant and smallest full moon), perhaps not enough to be noticeable to most of us using the eye alone," wrote Bruce McClure in his column for EarthSky.org.
McClure does believe the average observer will notice a brighter moon.
"The increase in brightness is because the size is larger," said Noah Petro, a NASA research scientist. "Think of moving a flashlight closer to your eye, or a mirror. The increase in apparent size results in the brighter moon."
Moonrise in West Palm Beach on Tuesday is at 7:27 p.m. Wednesday’s moonrise is at 8:35 p.m.
The forecast for Tuesday in South Florida is for mostly sunny skies turning to partly cloudy Tuesday night. Wednesday should be also be mostly sunny with a clear night sky to watch the show.
While super moons can trigger higher-than normal tides that lead to coastal flooding, the National Weather Service in Miami is not expecting significant tidal flooding this week in southeast Florida.
It’s the alignment between the sun, Earth and moon that can increase the gravitational pull on the tides. Tides typically run higher in the fall, which is why full moon tides can cause flooding September through December.
"We may see some very minor impacts along the coast," said meteorologist Robert Garcia. "It is certainly something we will keep an eye on."
Of course April’s pink moon won’t actually be pink.
According to The Old Farmer’s Almanac, moons were given nicknames to correspond to the seasons. April’s moon comes at time when early spring blooms of the wildflower phlox occur. | 0.837279 | 3.261659 |
Ceres is the most prominent object found in the asteroid belt that lies between Mars and Jupiter. It has a diameter of 945 km and, due to its dimensions, it has been classified as a dwarf planet, and it is the 33rd-largest object in our solar system. Ceres is made up mainly from ice and rock, and it is the only body in the asteroid belt that is rounded by its own gravity. The dwarf planet was discovered in 1801, by Giuseppe Piazzi, at Palermo Astronomical Observatory.
Dwarf planet Ceres is geologically active
Recently, a new study published in the journal Nature Geoscience offers new information that helps astronomers solve one of the solar system’s mysteries. The team of researchers that conducted the study analyzed the tallest mountain on Ceres, Ahuna Mons, and discovered that Ceres is geologically active, and its surface experiences eruptions.
According to scientists, this new information suggests that part of the dwarf planet’s surface was formed by erupting liquid water. NASA discovered the Ahuna Mons mountain in 2015 and immediately became a point of interest due to its strange appearance. Its height reaches 4000 km, and it has smooth contours that are different from other structures on the planet.
Scientists studied the formation of Ceres’ Ahuna Mons
The researchers used data gathered by NASA’s Dawn spacecraft to form a better understanding of the circumstances under which Ahona Mons was formed. They found that a large concentration of mass lies underneath the mountain. To observe Ahona Mons’ structure better, the scientists used computer models to examine the bizarre material below. The results explain the origin of the Ahona Mons mountain.
The mass was made up of salt and rocky mud originating from deep under the surface and going through the dwarf planet’s icy crust to form the strangely-structured mountain. To further see Ahuna Mon’s structure, they used computer modeling to see the materials below. Results provided the researchers with a surprising explanation for the origin of the strange mountain. | 0.86946 | 3.498663 |
The black hole and what it means for Namibia
Following the first image of a black hole being captured, the next step is building a radio telescope in Namibia – the Africa Millimetre Telescope.
28 April 2019 | International
The photo shows the black hole at the centre of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole is 55 million light-years from earth and is 6.5 billion times the mass of the Sun.
Interlinking eight telescopes has resulted in unprecedented sensitivity and resolution. Time after time, independent observations with the EHT, using different imaging techniques, have revealed a circular-type structure, with a dark area in the middle, a shadow of the black hole in M87.
“Scientists from all over the world worked together,” said Prof Anton Zensus of the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn and chair of the EHT management.
The director of the EHT Project, Sheperd Doeleman of the American Harvard/Smithsonian Centre for Astrophysics, said that this milestone in astronomy, was achieved thanks to a team of over 200 researchers from 18 countries.
In the beginning
Heino Falcke, Professor of Astroparticle Physics and Radio Astronomy at Radboud University, is the chair of the EHT Science Council and was there when the idea to photograph a black hole using a network of telescopes was first proposed.
“If the black hole exists in a bright area, such as a disc of glowing gas, we expect that it will create a very dark area, comparable to a shadow. We have also compared the photo with supercomputer simulations of different black-hole models. These simulations match up surprisingly well with the observations and make it possible to determine the characteristics of the black hole.”
The shadow is created by deflection of the light caused by the curvature of space and by the absorption of light in the so-called event horizon of the black hole. The horizon is the edge of the area from which nothing, not even light, can escape from the black hole.
Falcke: “Shape and size of the shadow perfectly match our expectations based on Einstein's general theory of relativity and the existence of an event horizon.”
Black holes are exotic cosmic objects which have enormous mass, but are small in size. A black hole exerts extreme influence on its environment. It curves spacetime and heats surrounding matter to super-high temperatures.
“The size of the shadow is related to the mass of a black hole and we managed to actually measure the enormous mass of the black hole in M87,” says Sera Markoff, professor of Astrophysics in Amsterdam.
With the EHT, scientists have a new instrument to study the most extreme objects in the universe, which were predicted by Einstein. The result comes exactly 100 years after the experiment that first proved Einstein's theory.
Falcke is looking forward to achieving clearer imaging after upgrades in the network. “It is the beginning of a new era in which the ultimate limit of space and time is no longer an abstract concept, but a measurable reality. To increase the sensitivity, we want to expand the EHT network and build a millimetre telescope in Africa. We are fortunate to already have the first supports in place, from different parties and even businesses.”
The Africa Millimetre Telescope
The mentioned Africa Millimetre Telescope (AMT) project is co-led by two teams at the Radboud University Nijmegen and the University of Namibia and aims at realising a 15m single-dish radio telescope on the Gamsberg in Namibia.
The AMT will be the only radio telescope in the mm-wavelength regime in Africa, and as such provides unique science opportunities for Namibia. The AMT project is envisioned as a highly visible and unique enabler of science, education & outreach, capacity enriching, sustainable energy and social-economic development in Namibia.
The explanation to the question why this extra telescope in Africa is needed is three-fold: quantity, location and connection.
The effectiveness of the EHT network depends on the length and orientation of the lines connecting each possible pair of telescopes: The more connections the better the image quality, the longer the separation, the better the resolution. The number of connections increases almost quadratically with the number of telescopes; hence even a single new telescope adds many new connections and improves the image quality by a critical margin.
A telescope placed in southern Africa will have additional benefits.
First of all, the centre of the Milky Way is right overhead at that location, providing the longest and least disturbed view of the black hole. In addition, it is centrally located between the big telescopes in Europe, Latin America and America and hence is of great importance for the entire experiment.
The AMT requires skilled personnel for the installation, maintenance and operations of the telescope and associated facilities. It is the goal of the AMT project to involve local industry partners for this, in combination with both Namibian Universities. This way, the AMT project can serve as a showcase for expertise of Namibian industry and the training and education of engineering capacity.
Furthermore, astronomy is one of the most extreme examples of Big Data, and is thus the ideal showcase for the Namibian ICT industry to present their expertise, paired with training opportunities at the local universities.
Beyond the actual project, the AMT team is developing an education and outreach programme. The goals are to motivate and inspire young students to pursue a career in science or engineering, and to make the general audience aware and proud of their Namibian scientists and engineers.
The AMT is currently in its telescope and infrastructure design phase. Next, the preliminary technical design of the AMT will be worked out, studies for the access to the site, on environmental impact and local infrastructure will be conducted as well as funds for the project shall be raised.
Only after this has been accomplished, the actual building and later commissioning and science phases can begin.
However, if all goes well, the AMT could be observing the supermassive black hole in the centre of our Milky Way as part of the EHT as of 2021. | 0.828453 | 3.683811 |
Crescent ♋ Cancer
Moon phase on 22 May 2061 Sunday is Waxing Crescent, 3 days young Moon is in Cancer.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 3 days on 19 May 2061 at 11:03.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠15° of ♋ Cancer tropical zodiac sector.
Lunar disc appears visually 2.7% wider than solar disc. Moon and Sun apparent angular diameters are ∠1946" and ∠1895".
Next Full Moon is the Strawberry Moon of June 2061 after 11 days on 3 June 2061 at 06:09.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 3 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 759 of Meeus index or 1712 from Brown series.
Length of current 759 lunation is 29 days, 7 hours and 1 minute. This is the year's shortest synodic month of 2061. It is 7 minutes shorter than next lunation 760 length.
Length of current synodic month is 5 hours and 44 minutes shorter than the mean length of synodic month, but it is still 25 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠358.7°. At beginning of next synodic month true anomaly will be ∠13.9°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
2 days after point of perigee on 19 May 2061 at 12:47 in ♊ Gemini. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 10 days, until it get to the point of next apogee on 2 June 2061 at 04:48 in ♐ Sagittarius.
Moon is 368 343 km (228 878 mi) away from Earth on this date. Moon moves farther next 10 days until apogee, when Earth-Moon distance will reach 406 301 km (252 464 mi).
5 days after its ascending node on 16 May 2061 at 19:55 in ♈ Aries, the Moon is following the northern part of its orbit for the next 7 days, until it will cross the ecliptic from North to South in descending node on 29 May 2061 at 16:23 in ♎ Libra.
5 days after beginning of current draconic month in ♈ Aries, the Moon is moving from the beginning to the first part of it.
1 day after previous North standstill on 21 May 2061 at 17:45 in ♊ Gemini, when Moon has reached northern declination of ∠28.328°. Next 13 days the lunar orbit moves southward to face South declination of ∠-28.272° in the next southern standstill on 4 June 2061 at 22:36 in ♐ Sagittarius.
After 11 days on 3 June 2061 at 06:09 in ♐ Sagittarius, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.07062 |
A comprehensive analysis of distorted galaxies from the most ambitious cosmic survey ever undertaken by the Hubble Space Telescope has confirmed the mysterious cosmic acceleration. It has also provided the equivalent of a 3D map of part of the Universe.
A group of astronomers, led by Tim Schrabback of Leiden Observatory, conducted an intensive study of more than 446 000 galaxies within the Cosmological Evolution Survey (COSMOS) field. COSMOS is the largest survey conducted with Hubble, which photographed 575 slightly overlapping views of the same part of the Universe using its Advanced Camera for Surveys. In total, the survey took nearly 1000 hours of observations.
In addition to the Hubble data, the researchers used ground-based observations to assign distances to 194 000 of the galaxies. "The sheer number of galaxies included in this type of analysis is unprecedented, but more important is the wealth of information we could obtain about the invisible structures in the Universe from this exceptional dataset," says team member Patrick Simon from Edinburgh University.
According to theory, the invisible Universe consists of dark matter and dark energy. It is not known what either component is; yet astronomers believe that they exist because of their effects on the motion of celestial objects. Dark matter contributes more gravity to the Universe on smaller scales, while dark energy resists gravity on the larger scales.
In the new analysis, the astronomers ‘weighed’ the large-scale matter distribution in space. This information is encoded in the distorted shapes of distant galaxies, a phenomenon referred to as ‘weak gravitational lensing’. The team’s new algorithms improve the standard method and measures galaxy shapes to an unprecedented precision.
The meticulous detail and scale of this study has confirmed that the Universe is accelerated by an additional, mysterious component: the dark energy. Only a handful of other such independent confirmations exist. "Dark energy affects our measurements for two reasons. First, when it is present, galaxy clusters grow more slowly. Secondly, it changes the way the Universe expands, leading to more distant galaxies that are more efficiently lensed. Our analysis is sensitive to both effects," says team member Benjamin Joachimi, University of Bonn.
This study is leading to a clearer map of this part of the Universe. "With more accurate information about the distances to the galaxies, we can measure the distribution of the matter between them and us more accurately," says team member Jan Hartlap, University of Bonn.
"Before, most of the studies were done in 2D, like taking a chest X-ray. Our study is more like a 3D reconstruction of the skeleton from a CT scan," says William High from Harvard University, another team member.
The astronomers specifically chose the COSMOS survey because it is thought to be a representative sample of the Universe. The results of the study will be published in an upcoming issue of Astronomy and Astrophysics. Astronomers will one day be able to apply these techniques to wider areas of the sky, forming a clearer picture of what is truly out there.
Notes for editors:
The Hubble Space Telescope is a project of international co-operation between ESA and NASA.
Tim Schrabback of Leiden University led the international team of astronomers in this study. Other collaborators included: J. Hartlap (University of Bonn), B. Joachimi (University of Bonn), M. Kilbinger (IAP), P. Simon (University of Edinburgh), K. Benabed (IAP), M. Bradac (UCDavis), T. Eifler (University of Bonn), T. Erben (University of Bonn), C. Fassnacht (University of California, Davis), F.W. High (Harvard), S. Hilbert (MPA), H. Hildebrandt (Leiden Observatory), H. Hoekstra (Leiden Observatory), K. Kuijken (Leiden Observatory), P. Marshall (KIPAC), Y. Mellier (IAP), E. Morganson (KIPAC), P. Schneider (University of Bonn), E. Semboloni (University of Bonn), L. Van Waerbeke (UBC) and M. Velander (Leiden Observatory).
View an image of the COSMOS field.
Tel: +31 71 527 5877
Email: schrabback @ strw.leidenuniv.nl
Tel: +49 89 3200 6306
Cell: +49 151 153 73591
Email: csharkey @ eso.org | 0.871898 | 4.123179 |
When scientists recently announced that they had discovered a new planet orbiting our closest stellar neighbor, Proxima Centuri, they also released an artist's conception of the planet.
The picture of a craggy canyon, illuminated by a reddish-orange sunset, looked like an image that could have been taken on Mars by one of NASA's rovers. But the alien scene was actually completely made-up.
It's part of an ever-increasing gallery of images depicting real planets beyond our solar system that, in fact, no one has ever seen.
Astronomers detect these planets by looking for how a planet's gravity tugs on its star, or how a planet blocks a star's light. Over the last two decades, they've used these techniques to detect thousands of planets.
Creating popular images to show what the planets might look like has become something of a cottage industry. The artists say this work can drive home the idea that these planets truly exist — but, still, some people worry that the public might get the wrong idea.
"It's tricky with computer graphics," says Ray Villard, news director for the Space Telescope Science Institute. "You can make stuff in such extraordinary detail, people might think it's real. People might think we've actually seen these features — canyons, all kinds of lakes and rivers."
"The point of these illustrations is to create excitement, to grab the general public's attention. But there is a danger that many people sometimes do mistake some of these illustrations for real photos," agrees Luis Calçada, an artist with the European Southern Observatory's education and public outreach department.
"Many, many astronomers actually do see this danger on this kind of illustration," he says, "because it might create false images on people's minds."
It's up to writers and captions to explain what the image really is, Calçada says.
"For us, it's quite the biggest compliment if people do confuse our illustrations for a real image," he jokes.
Artists collaborate with scientists, who share what is and isn't known about far-off planets, says Tim Pyle, a graphic artist who used to work for Hollywood and now works at NASA's Spitzer Science Center at Caltech.
Just by looking at a star, he says, "we're actually able to extrapolate quite a bit of information about, say, the number of planets that might be around it, their distance from the star, their size."
Scientists also usually know a lot about the star itself, and an artist can incorporate all of that into the image.
But there are still a lot of details that have to be filled in to create a plausible picture of what the planet might look like — and that can get tricky.
"If, you know, we find a planet that potentially has liquid water on its surface," Pyle says, "and, let's say, that's pretty rare. You're going to make sure that whatever your artist's concept is, you're focusing on that water in some way."
Depicting water isn't such a simple task. Take a planet called Kepler 186f, for example. It's a rocky planet that might have liquid water — or maybe not.
"We didn't want the general public to see this artist's concept and walk away thinking: 'Wow, they've found another Earth!' " recalls Pyle, who tweaked the color of the water again and again. He and his colleagues finally settled on a kind of muddy brown, instead of blue, so the water wouldn't look too inviting.
Then there was the time he illustrated Kepler 452b. Scientists couldn't agree on whether this planet could have water; it might have lost it all in what's called a runaway greenhouse effect. So Pyle created a planet with lots of volcanoes that was just beginning to lose its water.
"You could see lakes and rivers that had dried up and left behind salty residue along their shores," says Pyle, "and it was kind of a green, ugly water."
Images like this get a lot of press attention — Pyle's vision of 452b appeared on the cover of USA Today, for example.
"My mom actually saved a copy," he laughs.
In the early days of planet-hunting, scientists mostly spotted giant planets that are hot and gassy. Artists struggled to make each of them look unique.
"After you've done 10 'hot Jupiters,' they all sort of start to look the same," says Robert Hurt, an astronomer-turned-artist who works with Pyle.
Now that astronomers are finding smaller, potentially rocky planets, things are getting more interesting. Calçada recalls illustrating a rocky world that's so close to its star, it is probably covered in lava.
"This was a very exciting one to do," he says. "I quite liked to imagine all these lava features on the surface of the planet. It was not technically challenging, but it was one of the ones that I quite liked."
One thing should be taboo when illustrating a planet for a big public announcement by scientists, says Hurt: "We have never put anything indicating the possibility of life, or anything that you'd look at and say, 'Oh yeah, that's definitely a living organism.' "
Even trees or algae would be going too far, in his view.
"If you put one tree in that picture, that's the first thing that people are going to see, and that's their take-away," says Hurt. "You really have to be conscious, I think, of what people are going to pull out of that picture — what is going to be the piece of information they will most remember from that. You want to make sure that piece of information isn't something that is completely unknown or wrong."
These artists are part of a long tradition; illustrators were creating visions of planets in our own solar system long before any probe ever photographed them.
And, in fact, back in the 1960s, famed space artist Chesley Bonestell published a book called Beyond the Solar System that included artwork depicting planets beyond other stars. No such planets had been discovered at that point, but that didn't stop him from envisioning them. Villard says he found this book hugely inspiring when he was a kid.
"My favorite one of the planets had a pyramid," Villard says. "So they were implying that somebody might be living there — and they made pyramids, too."
Another planet had double shadows, he says, "because there were two stars in the sky. So they would cast different shadows of different colors."
Villard still prefers this kind of impressionistic artwork — which is the kind featured in a book he wrote called Infinite Worlds: An Illustrated Voyage to Planets Beyond Our Sun.
"It can be evocative without showing every little rock and stone and cliff that's on the planet," he says.
Still, he doesn't want to knock the computer-generated ones, because he understands the need to excite and inspire the public.
And, given the technical challenges, Villard thinks it will be well into the next century before we can take a real photograph of a planet beyond our solar system that comes anywhere close to what a space artist can imagine now.
You won’t find a paywall here. Come as often as you like — we’re not counting. You’ve found a like-minded tribe that cherishes what a free press stands for. If you can spend another couple of minutes making a pledge of as little as $5, you’ll feel like a superhero defending democracy for less than the cost of a month of Netflix. | 0.861437 | 3.479553 |
NASA’s Wide Field Infrared Survey Telescope (WFIRST), planned for launch in the mid-2020s, will create enormous cosmic panoramas. Using them, astronomers will explore everything from our solar system to the edge of the observable universe, including planets throughout our galaxy and the nature of dark energy.
Though it’s often compared to the Hubble Space Telescope, which turns 30 years old this week, WFIRST will study the cosmos in a unique and complementary way.
“WFIRST will enable incredible scientific progress on a broad range of topics, from stellar populations and distant planets to dark energy and the structure of galaxies,” said Ken Carpenter, the WFIRST ground system project scientist and Hubble operations project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Hubble contributed tremendously to our understanding in these areas, but WFIRST will propel us forward by studying far more objects in the sky.”
Thirty years after its launch, Hubble continues to provide us with stunning, detailed images of the universe. When WFIRST opens its eyes to the cosmos, it will generate much larger images while matching Hubble’s crisp infrared resolution.
Hubble adds to our picture of the universe in ways WFIRST can’t by using ultraviolet vision that captures the high-resolution details, and by providing more specialized features for in-depth study of the light emitted by individual objects. WFIRST provides a more general capability in covering wide areas at visible and infrared wavelengths.
Each WFIRST image will capture a patch of the sky bigger than the apparent size of a full Moon. Hubble’s widest exposures, taken with its Advanced Camera for Surveys, are nearly 100 times smaller. Over the first five years of observations, WFIRST will image over 50 times as much sky as Hubble has covered so far in 30 years.
Since the quality will be the same, WFIRST will function like a fleet of 100 Hubbles operating in sync. Its large field of view will enable WFIRST to conduct sweeping cosmic surveys that would take hundreds of years using Hubble. Scientists will use these surveys to study some of the most compelling mysteries in the universe, including dark energy — a strange force that is accelerating the expansion of the universe.
Hubble played a major role in discovering dark energy. In 1998, astronomers measured how fast the universe is expanding by using ground-based telescopes to study relatively nearby exploding stars, called supernovae. They made the surprising discovery that the expansion of the universe is speeding up. Astronomers using Hubble confirmed this result by measuring supernovae over a longer period of time. The data demonstrated that while the expansion of the universe was slowing down as expected over most of cosmic history, it began speeding up a few billion years ago.
Scientists have since determined that whatever is causing this acceleration currently makes up about 68% of the total matter and energy in the universe, but so far we don’t know much more about it. Uncovering the nature and role of dark energy will be one of WFIRST’s primary goals. Scientists will use three surveys to examine the dark energy puzzle from different angles, including a survey of one key type of supernova, building on the observations that led to dark energy’s discovery. The mission’s two large area surveys will measure the shapes of hundreds of millions of galaxies and find the distances to tens of millions. This will turn WFIRST’s wide-field images into 3D maps that measure the expansion of the universe and the growth of galaxies within it.
WFIRST will help us understand how dark energy has affected the expansion of the universe in the past, which will shed light on how it may influence the future of the cosmos.
A new set of eyes on the universe
While Hubble views the cosmos in infrared, visible and ultraviolet light, WFIRST will be tuned to see a slightly wider range of infrared light than Hubble can observe. Detecting more of the spectrum of light allows Hubble to create a more comprehensive picture of many processes at work in individual objects in the cosmos. WFIRST is designed to expand on Hubble’s infrared observations specifically, because conducting enormous surveys of the infrared universe will let us see vast numbers of cosmic objects and subtler processes in regions of space that would otherwise be difficult or impossible to view.
WFIRST will help unravel mysteries surrounding dark energy and the evolution of galaxies by peering across enormous stretches of the universe — even farther than Hubble is capable of seeing. These studies require precise infrared observations because light shifts into longer wavelengths, from ultraviolet and visible into infrared, as it travels across vast astronomical distances due to the expansion of space.
WFIRST’s infrared capabilities will also provide a new view into objects that are closer to home. The heart of our Milky Way galaxy is densely populated with rich targets, but shrouded in dust that obscures visible light. As an infrared telescope, WFIRST will essentially use heat-vision goggles to peer right through the dust, giving us a new view into the inner workings of the galaxy.
These observations will allow astronomers to study stellar evolution — the births, lives and deaths of stars. WFIRST will also expand our inventory of exoplanets — planets outside our solar system — by revealing thousands of worlds that astronomers expect will be very different from most of the 4,100 now known. Most of the currently known exoplanets are either very close to their host stars, or large planets orbiting farther away. Hubble has observed some of these planets directly using coronagraphs, which block the glare from stars. WFIRST will build upon that technology to make an active coronagraph that is much better at suppressing starlight — a demonstration of technology that, when further advanced, will enable future space telescopes to image Earth-size exoplanets.
Homing in on cosmic rarities
Scientists will also use WFIRST’s cosmic surveys to obtain enormous samples of some of the most extreme objects in the universe, including quasars — active galaxies with super-bright centers. Pinpointing their locations will allow Hubble and other telescopes to follow up for detailed observations. These investigations will enable astronomers to piece together the history of galaxy growth and the evolution of the universe.
To make these studies possible, WFIRST will operate much farther away from Earth than Hubble does. While Hubble orbits about 340 miles above us, WFIRST will be located about 930,000 miles (1.5 million km) away from Earth in the direction opposite the Sun. At this special place in space, called the second Sun-Earth Lagrange point, or L2, gravitational forces from the Sun and Earth balance to keep spacecraft in relatively stable orbits.
Near L2, WFIRST will orbit the Sun in sync with Earth, using a sunshield to block sunlight and keep the spacecraft cool. Since infrared light is heat radiation, if WFIRST is warmed by radiation from Earth, the Sun or even its own instruments, it will overwhelm the infrared sensors. From this vantage point, WFIRST can view large swaths of sky smoothly over long periods of time.
WFIRST is managed at Goddard, with participation by NASA's Jet Propulsion Laboratory and Caltech/IPAC in Pasadena, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from research institutions across the United States. | 0.87225 | 3.975368 |
Growing up, my sister played video games and I read books. Now that she has a one-year-old daughter we constantly argue over how her little girl should spend her time. Should she read books in order to increase her vocabulary and stretch her imagination? Or should she play video games in order to strengthen her hand-eye coordination and train her mind to find patterns?
I like to believe that I did so well in school because of my initial unadorned love for books. But I might be about to lose that argument as gamers prove their value in science and more specifically astronomy.
Take a quick look through Zooniverse and you’ll be amazed by the number of Citizen Science projects. You can explore the surface of the moon in Moon Zoo, determine how galaxies form in Galaxy Zoo and search for Earth-like planets in Planet Hunters.
In 2011 two citizen scientists made big news when they discovered two exoplanet candidates — demonstrating that human pattern recognition can easily compliment the powerful computer algorithms created by the Kepler team.
But now we’re introducing yet another Citizen Science project: Disk Detective.
Planets form and grow within dusty circling planes of gas that surround young stars. However, there are many outstanding questions and details within this process that still elude us. The best way to better understand how planets form is to directly image nearby planetary nurseries. But first we have to find them.
“Through Disk Detective, volunteers will help the astronomical community discover new planetary nurseries that will become future targets for NASA’s Hubble Space Telescope and its successor, the James Webb Space Telescope,” said the chief scientist for NASA Goddard’s Sciences and Exploration Directorate, James Garvin, in a press release.
NASA’s Wide-field Infrared Survey Explorer (WISE) scanned the entire sky at infrared wavelengths for a year. It took detailed measurements of more than 745 million objects.
Astronomers have used complex computer algorithms to search this vast amount of data for objects that glow bright in the infrared. But now they’re calling on your help. Not only do planetary nurseries glow in the infrared but so do galaxies, interstellar dust clouds and asteroids.
While there’s likely to be thousands of planetary nurseries glowing bright in the data, we have to separate them from everything else. And the only way to do this is to inspect every single image by eye — a monumental challenge for any astronomer — hence the invention of Disk Detective.
Brief animations allow the user to help classify the object based on relatively simple criteria, such as whether or not the object is round or if there are multiple objects.
“Disk Detective’s simple and engaging interface allows volunteers from all over the world to participate in cutting-edge astronomy research that wouldn’t even be possible without their efforts,” said Laura Whyte, director of Citizen Science at the Adler Planetarium in Chicago, Ill.
The project is hoping to find two types of developing planetary environments, distinguished by their age. The first, known as a young stellar object disk is, well, young. It’s less than 5 million years old and contains large quantities of gas. The second, known as a debris disk, is older than 5 million years. It contains no gas but instead belts of rocky or icy debris similar to our very own asteroid and Kupier belts.
So what are you waiting for? Head to Disk Detective and help astronomers understand how complex worlds form in dusty disks of gas. The book will be there when you get back.
The original press release may be found here. | 0.933536 | 3.494293 |
Hubble Turns 30: Story of a Problem Child
It was never the world’s biggest telescope, and it can’t see as far as some. But for the public, the Hubble Space Telescope is undoubtedly the most famous astronomical instrument ever.
True, most people couldn’t tell you the first thing about Edwin Hubble. But all have seen the spectacular photos made with his optical namesake. It’s plausible to claim that this orbiting spyglass has done as much to spur interest in science as to reveal the secrets of the cosmos.
Still, the now-famous telescope’s first months were inauspicious. On April 26, 1990 it was gently set into orbit from the cargo bay of the space shuttle Discovery. For the next few weeks, it underwent equipment checks and efforts to refine the focus. By late May, preliminary photos showed that the imagery was about twice as sharp as any ground-based telescopes. That may sound cheery, but in fact fell far short of expectations.
Something was wrong. For days HST scientists futzed around trying to sharpen the pictures made by the 300-mile high instrument. Then one morning as I sat at a desk at the State University of Groningen, a fellow astronomer charged into the office shouting “Hubble is [expletive]!”
Bad news, and soon the astronomical community realized that the 95-inch primary mirror had an optical defect known as spherical aberration – the surface was wrongly shaped. Of course, you couldn’t tell by looking at it: The error amounted to two percent the width of a human hair.
Overnight, NASA’s premier astronomical instrument, decades in the making, became an embarrassment and a joke. In the satiric 1991 movie "Naked Gun 2-1/2," a photo of the HST could be seen hanging on the wall of the “Loser’s Bar” alongside pictures of the Edsel, the airship Hindenburg, and other notable debacles. A low point.
By the end of 1993, space shuttle astronauts taking part in the first Hubble servicing mission had installed a device made by the Ball Aerospace Corporation called COSTAR (a shorter way to say Corrective Optics Space Telescope Axial Replacement.) It was described at the time as “contact lenses” for the Hubble. In addition, a separate instrument, the Wide Field Planetary Camera 2, was installed. There was no simple contact lens fix for this, Hubble’s principal imaging device. The shuttle astronauts replaced it with a new model the size of a workbench, quickly constructed at the Jet Propulsion Laboratory.
SETI Institute astronomer Bill Sparks was part of the team waiting to see what WFPC2 would do as 1994 began. Staring at screens in HST’s Baltimore headquarters, he and the crowd held its collective breath as the first image from the refitted telescope came up.
“It had nothing in it,” recalls Sparks. “My mind was racing: ‘I checked that a thousand times’ I thought. But before I fainted away, the correct image appeared on the screen, and it was one of those OMG moments. It was sharp and detailed.”
“In the blink of an eye, the world changed, and we knew this was special. That picture was on the cover of Time magazine, and since then Hubble images have become part of everyday life.” Most of the famous ones were made with the replacement WFPC.
The HST was intended to do cosmology research; to measure how fast the universe is expanding and investigate how galaxies form. It did that work of course, but as with all new astronomical instruments its greatest triumphs were discovering the unexpected – such as evidence that the cosmos is suffused with dark energy.
The drumbeat of Hubble’s triumphs has been incessant, not because the telescope is large, but because – despite its unlucky beginnings – it’s sharp. Earth’s turbulent atmosphere inevitably blurs the images made with any instrument on the ground, even if that ground is high up on a mountain. Hubble’s vision is typically ten times better than its terrestrial brethren. What it lacks in aperture, it makes up in location.
Thirty years later, Hubble, slightly hamstrung by the aging gyroscopes that stabilize its pointing, is still doing top-drawer science. It’s likely to continue to delight astronomers and the public for another decade or two. But a year from now, its successor – the James Webb Space Telescope – will be boosted into high orbit. Unlike Hubble, the JWST will operate at infrared wavelengths. This will permit it to more effectively look to greater distance (the expansion of the universe shifts all light and radio to longer wavelengths) and probe the universe’s early history.
Yes, JWST will be more sensitive and in many ways more ambitious than its forebear. But Hubble will always have the right of progenitor. It is one of science’s immortals.
Dr. Seth Shostak is a Senior Astronomer and SETI Institute Fellow | 0.80239 | 3.209611 |
Since asteroids have mass, they have gravity. And if you’ve got gravity, you can have moons. Several asteroids have been discovered in the outer Solar System with smaller asteroidlets circling them. But now the Arecibo radio telescope in Puerto Rico has turned up the closest example – a triple system just a mere 11 million km (7 million miles) from Earth.
Asteroid 2001 SN263 was revealed to be a triple system by Cornell astronomer Michael C. Nolan. The asteroid itself had been discovered back in 2001 as part of an automated survey. He and his colleagues captured radio images of the space rocks on February 11. By studying the images, they realized that they actually had a system of three objects.
The main central asteroid is roughly 2 km (1.5 miles) across. The larger “moon” is about half that size, and the smallest is about 300 metres (1,000 feet) across.
Asteroid systems like this have been seen in the Asteroid Belt, between Mars and Jupiter, but never so close. This allows scientists to image it with unprecedented detail.
As researchers find more and more near-Earth asteroids, they’re starting to realize that binary systems are actually quite common. According to Nolan, one in six near-Earth asteroids is a binary. Although, this is the first near-Earth triple system seen.
Multiple asteroid systems are very useful for astronomers; they provide the mass calculation. In a multiple object system like this, you can calculate the mass of each object by knowing the various periods (the time they take to complete an orbit). Researchers can then compare the mass of the binary objects to the brightness of single asteroids to estimate their masses as well.
One of the big unanswered questions: did the three objects form together, or were they captured later on? By watching the system over time, Nolan and his team will get a better sense if they’re orbiting on the exact same plane (like our Solar System). This will be evidence they formed together billions of years ago.
Arecibo is one of the best asteroid hunting tools available to astronomers; unfortunately, budget cuts in the United States has put the future of the facility in jeopardy.
Original Source: Cornell News Release | 0.817861 | 3.686066 |
[title_box title=”Professor discusses Earth-like world of Saturn moon”]
At the March 4 Quest Science Forum, UT professor Devon Burr spoke about the “surprisingly earth-like world” of Titan, Saturn’s largest moon.
Even though it is in the outer solar system, Titan shares many similarities with Earth and other terrestrial planets. For example, like Earth, Titan’s atmosphere is predominately made of nitrogen. This fact was confirmed by the Voyager Spacecraft in 1980, though Burr said it is highly unusual for an Outer Solar System planet to even have an atmosphere.
This thick atmosphere makes it difficult for scientists to see down to the surface of Titan. Burr compared the moon’s atmosphere to Los Angeles smog— yellow and hazy. Seeing through the atmosphere requires looking at radar images to study the surface features.
With radar and mapping technologies, scientists have learned that Titan’s surface has many dry river channels that move in patterns similar to those of Earth’s river systems. Scientists believe that Titan has subsurface oceans, meaning that the rock below the surface is extremely saturated with water.
The radar also picks up images of sand dunes on Titan, which are about 100 meters high and cover about 20 percent of the surface. Burr said these dunes are made up of particles similar to those found in the atmosphere, leading them to believe that the dunes are created by aerosols that rain down from above.
Titan’s extreme distance from the sun causes it to receive only one-hundredths of the energy from the sun that Earth does. In 1997, the Cassini-Huygens mission was sent to Titan as one of NASA’s last billion dollar missions.
“Because the spacecraft was so far away from the sun, it wasn’t possible to use solar energy like we would with an inner solar system mission,” Burr said. “So we basically used nuclear energy.”
In the next decade, Burr said, NASA is prioritizing going to Venus, the moon, the Trojan Asteroids and Uranus. She also noted missions launching to the Asteroid Belt next year and Mars in 2020.
The science forum will not be held for the next three Fridays, but will begin again on April 1 with a discussion on Pluto.
Featured image by Ryan McGill
Edited by Courtney Anderson | 0.866461 | 3.392529 |
By Dr David Whitehouse
BBC News Online science editor
The Hubble Space Telescope (HST) has detected the smallest objects ever seen orbiting beyond the distant planet Neptune.
Small, distant and cold
The three objects, which are just a few tens of miles across, are relics from the formation of the Solar System.
The icy bodies become comets if they approach the Sun where its heat turns their ice into a billowing tail of gas.
But astronomers are puzzled as there seem too few distant chunks of ice and rock to account for the number of comets seen orbiting the Sun today.
Born of ice and dust
The planets formed over four billion years ago from a cloud of gas and dust that surrounded the nascent Sun.
Tugged by gravity, the fragments of ice and dust stuck together to form lumps that grew from pebbles to boulders to city- or continent-sized so-called planetesimals.
Around 1950, astronomers Gerard Kuiper and Kenneth Edgeworth proposed that in the region beyond Neptune there are no planets capable of dispersing leftover planetesimals.
They postulated that there should be a zone - now called the Kuiper Belt - filled with small, icy bodies.
Despite many years of searching, the first such object was not found until 1992. Since then, astronomers have discovered nearly 1,000 from ground-based telescopes.
Astronomers estimate that if collected together into a single planet, the resulting mass would only be a few times bigger than Pluto, the Solar System's tiny outermost world.
'Difficult to understand'
The most recent search detected three small objects named 2003 BF91, 2003 BG91, and 2003 BH91, which range in size from 15-28 miles (25-45 km) across.
The study's big surprise is that so few Kuiper Belt objects were discovered. Given Hubble's abilities, astronomers had expected to find at least 60 Kuiper Belt members as small as 10 miles (15 km) in diameter - but only three were discovered.
"Discovering many fewer Kuiper Belt objects than was predicted makes it difficult to understand how so many comets appear near Earth, since many comets were thought to originate in the Kuiper Belt," says Gary Bernstein of the University of Pennsylvania, US.
"This is a sign that perhaps the smaller planetesimals have been shattered into dust by colliding with each other over the past few billion years."
The new Hubble observations, combined with ground-based Kuiper Belt surveys, reinforce the view that Pluto and its moon Charon are just large Kuiper Belt members.
Why the Kuiper Belt planetesimals did not form a larger planet, and why there are fewer small planetesimals than expected, are questions that will be addressed by future studies. | 0.800649 | 3.769213 |
Click the name of a planet to learn more about its visibility in June 2020.
Venus – the brightest planet – is lost in the sun’s glare for the first week or two in June 2020. Venus swings in front of the sun (at inferior conjunction) on June 3, 2020, to transition out of the evening sky and into the morning sky. Look for Venus to reappear in the eastern dawn by around mid-June.
Around the world, Venus pretty much rises and sets with the sun in early June 2020.
At mid-northern latitudes, Venus rises about an hour before the sun in mid-June, increasing to about 2 hours by the month’s end.
At and near the equator, Venus rises about 1 1/4 hours before the sun in mid-June, increasing to about 2 1/3 hours near the month’s end.
At temperate latitudes in the Southern Hemisphere, Venus rises about 1 1/3 hours before the sun in mid-June, increasing to about 2 2/3 hours by the month’s end.
After Venus swings over into the morning sky in early June, Venus in its faster orbit around the sun will be going farther and farther away from Earth. As viewed through the telescope, Venus’ waxing crescent phase will widen, yet its overall disk size will shrink. Venus’ disk is 0% illuminated on June 3, and about 18% illuminated by the month’s end; Venus’ angular diameter, on the other hand, will shrink to 3/4th the size by the month’s end.
All the same, Venus will brighten throughout the month and into July. Look for Venus to beam at its brightest in the morning sky on or around July 10, 2020, when Venus displays its greatest illuminated extent on the sky’s dome. Venus always beams at its brightest best when its disk is about one-quarter illuminated by sunshine.
Look for the waning crescent moon in the vicinity of Venus for several days, starting on or near June 17. In fact, if you live at the right spot on Earth, you can watch the moon occult (cover over) Venus on June 19, 2020.
Mercury reaches its greatest eastern (evening) elongation from the setting sun on June 4, 2020. Have binoculars handy, however, for Mercury has to compete with the glow of evening twilight. Given an unobstructed horizon in the direction of sunset, you have a reasonably good chance of catching Mercury during the first week of June. This world is dimming daily, though, and by mid-June, Mercury will be about four times fainter. In other words, early June presents your best shot for catching Mercury after sunset.
At mid-northern latitudes, Mercury sets about 1 5/6 hours after the sun in early June, tapering to 1 1/4 hours by mid-month.
At or near the equator, Mercury sets about 1 2/3 hours after the sun in early June, tapering to 1 1/3 hours by mid-month.
At temperate latitudes in the Southern Hemisphere, Mercury sets about 1 1/2 hours after sunset throughout the the first half of June.
Mercury transitions out of the evening sky and into the morning sky on July 1, and then reaches its greatest elongation in the morning sky on July 22, 2020.
Jupiter and Saturn are near one another on the sky’s dome, with Saturn following Jupiter westward across the sky from mid-to-late evening till dawn. Look first for brilliant Jupiter and you’ll find Saturn a short hop to the east of the king planet. Remember, east is in the direction of sunrise. Although Saturn is easily as bright as a 1st-magnitude star, the ringed planet pales next the the king planet Jupiter, which outshines Saturn by some 15 times.
At mid-northern latitudes, Jupiter and nearby Saturn rise at late evening in early June and by the month’s end at nightfall.
At temperate latitudes in the Southern Hemisphere, Jupiter and Saturn rise at mid-evening in early June, and by nightfall at the month’s end.
Mars, which is a bit brighter than Saturn, more or less aligns with Jupiter and Saturn in the predawn/dawn sky. However, standoffish Mars is a long jump to the east of Jupiter and Saturn. Saturn shines between Jupiter and Mars, though much closer to Jupiter.
Watch for the moon in the vicinity of Jupiter and Saturn for several days, centered on or near June 8.
Mars is the last of the three bright morning planets to rise in June 2020. Jupiter rises first, closely followed by Saturn, and then a few to several hours later by Mars. Whereas Jupiter and Saturn almost rise in tandem, Mars is off by itself in a rather dim section of sky.
At mid-northern latitudes, Mars rises about an hour after midnight in early June, and near the midnight hour by the month’s end. By midnight, we mean midway between sunset and sunrise.
At temperate latitudes in the Southern Hemisphere, Mars comes up at or near the midnight hour throughout the month.
Let the waning crescent moon help guide your eye to Mars for several mornings, centered around June 13.
In June 2020 … you’ll find Mars respectably bright – easily as brilliant as a 1st-magnitude star – before dawn. Earth will be rushing along in its smaller, faster orbit, gaining on Mars, the fourth planet outward from the sun. Throughout the next several months, watch for Mars to brighten dramatically as Earth closes in on Mars. The red planet will appear brightest in our sky and fiery red – around the time of its opposition – when Earth passes between Mars and the sun on October 13, 2020. At that wondrous time, Mars will actually supplant Jupiter as the sky’s fourth-brightest celestial body, after the sun, moon, and the planet Venus, respectively.
What do we mean by bright planet? By bright planet, we mean any solar system planet that is easily visible without an optical aid and that has been watched by our ancestors since time immemorial. In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These planets actually do appear bright in our sky. They are typically as bright as – or brighter than – the brightest stars. Plus, these relatively nearby worlds tend to shine with a steadier light than the distant, twinkling stars. You can spot them, and come to know them as faithful friends, if you try.
Bottom line: June 2020 presents all 5 bright solar system planets. Catch Mercury at dusk in early June, and Venus at dawn in the second half of the month. Jupiter and Saturn are rising earlier in the evening each day, and may be up before bedtime by mid-month. Look for Mars in the predawn/dawn sky, a long way to the east of Jupiter and Saturn.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York. | 0.89892 | 3.56615 |
In recent years, scientists have suggested that images from the Hubble telescope show plumes of icy water spewing from the surface of Jupiter’s moon Europa. Others have doubted the claim—which is fair enough, because the images are kind of fuzzy and the satellite’s instrument couldn’t always capture them.
But intrigued by Hubble’s images from 2014 and 2016, the University of Michigan’s Xianzhe Jia recently went back to the data taken by the Galileo spacecraft that flew past Europa in December 1997. Today, he and other scientists presented more evidence that the Jovian moon is spewing out big fountains of water from its icy surface. Now, the hope is that scientists can grab some of it and check for life—and in fact, NASA is already working on it.
During a three-minute datastream during the 1997 flyby, Galileo’s plasma wave instrument showed unusual emissions of charged particles. An on-board magnetometer registered a shift in the magnetic field that envelopes Europa from nearby Jupiter. To Jia, associate professor of space and planetary science at the University of Michigan, these two anomalies indicated an atmospheric disturbance very much like a geyser of salty ice water coming from a volcanic “hot spot” on the surface below. The water energized atmospheric particles, and Galileo detected their signature as it flew through.
To prove his theory, Jia and colleagues ran the data through a modeling program that compared the Galileo observations with what scientists might expect to see from a plume of the same size as imaged by Hubble. “When we tested the plume models, we found one with a good match for observations [from Galileo],” Jia said during a NASA press conference Monday to coincide with the work’s publication in Nature Astronomy.
This clever scientific detective work has boosted Europa’s fortunes as a potential home for extraterrestrial life. If a moon has liquid water spewing from its surface, maybe there’s something really interesting living below. Last year, NASA’s Cassini mission found hydrogen spewing from Saturn’s moon Enceladus, giving rise to speculation about the possibility of life-giving hydrothermal vents below its icy surface.
That’s where Charles Hibbits comes in. He’s a research scientist at Johns Hopkins University’s Applied Physics Laboratory in Laurel, Maryland, and a team leader on the Europa Clipper mission that is scheduled to launch in 2020. NASA and APL are designing the spacecraft to circle Europa 44 times, swooping down just 15 miles above the frozen surface.
Hibbits is designing and building an instrument called the Mapping Imaging Spectrometer for Europa that can actually detect the plume directly, and perhaps tell whether some life form is hitching a ride. Using light signatures, MISE will also scan the moon’s surface to map the distribution of organics, salts, acid hydrates, water ice phases, and other materials that can give hints about Europa’s potential ability to support life.
Europa is covered by a crust of ice that protects an ocean below, and the plume could provide a key to understanding what lives below the surface without having land a spacecraft and drill. “The real good stuff would be down below, perhaps dormant life in the ice,” Hibbits said in an interview with WIRED. “But life requires mobility and active chemistry, and as far as we know, it requires active water. All that is in the subsurface of Europa.”
Another instrument aboard the Europa Clipper—there will be nine total—will use radar to probe through surface to look at the depth and density of the crust and the liquid water below it. If Europa Clipper detects the chemistry needed for life, or something tantalizingly close, it will make it easier to figure out where to land a future robotic mission on Europa, drill through its crust, and perhaps swim through its icy sea. That scenario played out in the 2013 sci-fi thriller “Europa Report”—though it didn’t end so well for the mission’s six human astronauts.
For his part, Hibbits is both cautious and excited about the hunt for life on Europa. “Scientists are always dubious,” Hibbits says. “We would go in hoping for the best but planning for the worst. The surprise is that it is going to be an active plume. But maybe it’s just dust.” | 0.854165 | 3.83995 |
If a space rock were to hit the Earth at just the right location in the oceans, it could cause massive waves that could inundate U.S. coastlines, a new computer simulation suggests.
For instance, if an asteroid were to hit the continental shelf off the Maryland coast, it could produce 23-foot-high (7 meters) waves, causing flooding from New York to Georgia that would take hours to recede. A similar impact off the coast of California could flood major power plants along the coast, the research also suggests.
But not everyone is worried. Many simulations use unrealistic models for how waves break in the ocean, and major ocean impacts in the past haven't caused tsunamis, said H. Jay Melosh, a planetary scientist at Purdue University in Indiana who studies impacts but was not involved in the new study.
Asteroid impacts like the one that struck in what's now Chicxulub, Mexico, 65 million years ago — which is believed to have caused the extinction of the dinosaurs — occur very rarely. But smaller space rocks, such as the meteor explosion that blasted through the atmosphere in Chelyabinsk, Russia, in 2013, can cause major property damage and batter the Earth every few decades.
To evaluate the threat of such smaller impacts to U.S. coastlines, Souheil Ezzedine, an applied mathematician at Lawrence Livermore National Laboratory in California, and his colleagues used a computer simulation to mimic how asteroids of about 165 feet (50 meters) in diameter crashing into the ocean would affect waves.
In a separate simulation, Ezzedine also modeled the effects of similar impacts on the West Coast. He found that impacts at certain points in the ocean could lead to waves up to 10 feet (3 meters) high.
"That's not good news. A lot of power plants of PG&E are pretty much on the shore," Ezzedine told Live Science.
In fact, a 2012 report by the California Energy Commission suggests that a 5-foot (1.4-meter) rise in sea levels — which is predicted to occur by 2100, due to climate change — could flood many power plants. Therefore, the even-higher waves that could come from an asteroid impact would likely flood the power plants as well, Ezzedine said.
But many experts think the risk of an asteroid-caused tsunami has been overhyped.
An upcoming study which will be published in the journal Earth and Planetary Sciences found that the Eltanin impact, which left a huge crater in the ocean floor off the coast of Chile 2.1 million years ago, didn't cause a tsunami. The asteroid that caused this impact was likely 0.9 to 1.2 miles (1.5 to 2 kilometers) in diameter — far larger than the relatively small rocks Ezzedine's team has modeled. If such a massive rock didn't cause problems, it seems even less likely that a relatively meager one could, Melosh said.
In addition, past models that found monster wave heights were based on flawed assumptions about how waves break in the ocean. These models predict wave heights that exceed the depth of the ocean at that point — a physical impossibility, Melosh said.
Instead, what would actually happen would be that "a big wave gets made by the impact and it's a very turbulent wave, and it breaks immediately, right next to the impact," Melosh told Live Science. "Very little energy is actually radiated away."
There are other risks, besides tsunamis, that could come from relatively small space rocks like the Chelyabinsk meteor impact. In the Chelyabinsk impact, the space rock burned up in the atmosphere, but air blasts caused significant property damage, Melosh said. | 0.804553 | 3.538923 |
Today, September 15, 2017, at 7:57 am, Eastern Standard time, the Cassini–Huygens spacecraft, known to friends as “Cassini,” slipped quietly into the atmosphere of Saturn and died a violent and beautiful death as it burned up in the gaseous layers of the sixth planet from our sun.
Cassini is survived by cousin Juno, currently orbiting Jupiter, and much more distant cousin New Horizons who is currently at a distance of 39.04 AU and is headed out past Pluto toward the edged of the solar system. Cassini is preceded in death by such great relatives as Galileo, Magellan, and V’ger.
Cassini was launched on October 15, 1997 in Cape Canaveral, Florida, by both proud parents, NASA and the European Space Agency. It was a simpler time of Presidential scandals and space travel. Cassini graduated from two Venus gravitational assists in 1999 and an additional Earth gravitational assist in 1999 with a degree of trajectory that pushed it past the Asteroid belt and a Jupiter fly-by. Cassini married itself to the gravitational pull of Saturn, the second largest planet in our solar system -and a heck of a violin player- on July 1, 2004, exchanging both F and G Rings.
After moving to a stationary orbit, Cassini began working its initial four-year mission to explore the Saturnian System, which included examining not just the planet and its weather patterns, but its multiple moons system, and of course, its breathtaking rings. Cassini even helped test aspects of Einstein’s Theory of General Relativity. Its mission was extended twice, due in no small part to its plutonium powered engine, and healthy lifestyle. During its thirteen year mission it has taken thousands of breathtaking shots of the gas planet, its moons, its rings, and even Earth.
Cassini soon welcomed its only child to the Saturnian System, the Huygens probe, which landed on the moon Titan. Huygens relayed hundreds of images of Titan’s icy surface, but an unfortunate data error meant that the young probe only transmitted half the amount of data it was meant to. Yet, its memory still lives on as the first spacecraft to ever land on Titan, and as the first spacecraft to complete the furthest landing from Earth ever made.
Cassini was an accomplished explorer and an amateur photographer. It was a dedicated and hard working probe who loved its work and was passionate about educating us on the wonders of Saturn and its mysterious moons. Cassini was an active and dedicated member of NASA’s Planetary Science Division, and often volunteered at the local Rotary Club.
A memorial service was held today at the NASA JPL Live Stream, with a small reception to follow at wherever people typically eat lunch every day. All were welcome to attend and celebrate the life of the Cassini–Huygens spacecraft. In lieu of flowers, please send letters to your local congressional representatives and senators to tell them why the mission of NASA is so important, and why it deserves more funding than it currently receives. Condolences and congratulations can be sent to www.nasa. gov. The family would like to thank all those who have been watching and enjoying the data and pictures of Cassini, and for all their years of support and wonder.
So long, Cassini, and thanks for all the memories. Rest in peace. | 0.811868 | 3.467018 |
The New Horizons spacecraft, which has now visited Pluto and the Kuiper belt, is not the only spacecraft to mark a major milestone on New Year’s Eve. NASA’s OSIRIS-REx set a new record as it entered near orbit around the asteroid Bennu. This marks the closest orbit of a spacecraft from Earth around such a small object in space.
NASA’s OSIRIS-REx embarked on its journey to Bennu in 2016 and reached it in December. The spacecraft surveyed the asteroid for a time as scientists calculated the best method to approach it and begin studying it up close. The asteroid Bennu is located 70 million miles from Earth. Scientists believe it’s important to study carbon-rich asteroids like it because they may have brought the building blocks of life to Earth millions of years ago.
NASA announced the important milestone in space exploration on New Year’s Eve, adding that it took only an eight-second burn on the spacecraft’s thrusters for it to enter close orbit. OSIRIS-REx set a new record because this is the closest any spacecraft has ever orbited its object of study in space. At only “5-millionths” the strength of Earth’s gravitational pull, Bennu’s gravity force is so small that it’s barely enough to sustain a stable orbit for the spacecraft.
NASA’s OSIRIS-REx probe is orbiting the asteroid Bennu just one mile from its center; the space agency describes the spacecraft’s orbit as occurring “at a snail’s pace.” It will take 62 hours for the probe to complete one orbit around the asteroid.
The close orbit will enable NASA’s OSIRIS-REx to capture detailed, accurate images which scientists will use to study the asteroid’s surface, which the space agency describes as a “rubble pile of primordial debris.” The spacecraft has already sent several images back to Earth. It also discovered signs of water in hydroxyl groups.
However, this is not where the mission ends; the space agency will need to make adjustments to the probe’s orbit to keep it stable. Those adjustments include so-called “’trim’ maneuvers,” which are used to counter the small forces between the two bodies so that the spacecraft can maintain its orbit.
If things go wrong and NASA’s OSIRIS-REx loses its balance while in orbit, it is programmed to fly away and avoid an accidental impact with the space rock. Then when the probe reaches a safe distance again, NASA’s team will try to put the spacecraft back into orbit.
After it set a new record, the spacecraft will go through multiple phases on its data- and image-collecting mission. After it completes all of its planned orbits and finishes gathering data, the spacecraft is expected to land on the asteroid briefly and collect a sample, which is scheduled to arrive back at Earth in a return capsule some time in September 2023. | 0.824668 | 3.554743 |
Tuesday, 6 November 2012
Dark matter filament illuminated
An invisible web thought to span the cosmos has now revealed one of its strands.
That thread is spun of dark matter and connects two titanic clusters of galaxies, some of the most massive objects in the universe. Its discovery supports the idea that galaxy clusters grow at the intersections of such filaments, and its heft backs the claim that filaments hide more than half of all matter.
“Filaments of dark matter have never been seen before,” says Jörg Dietrich, an astronomer at the University Observatory Munich in Germany, whose team reports the finding online July 4 in Nature. “For the first time, we successfully mapped one.”
As the name suggests, dark matter is difficult to detect because it gives off no light or other radiation. The material’s presence is typically inferred by measuring how its gravitational pull changes the motions of stars and galaxies.
But look closely, and the shy matter can provide more direct evidence of its presence. Its gravity warps the fabric of spacetime and bends light passing nearby, so that more distant galaxies beyond the intervening dark matter appear distorted.
This lensing has already revealed dense clouds of dark matter kicked out of colliding galaxies. (SN Online: 3/06/12; SN: 8/26/06, p. 131) Filaments should likewise produce the fun house–like distortion. But since the dark matter in such structures isn’t as dense as the clouds ejected by galactic smashups, the effect is much weaker.
“With current telescopes … it’s very difficult to detect a filament,” says Lindsay King, an astrophysicist at the University of Texas at Dallas.
To improve the odds of seeing one, Dietrich and colleagues focused on Abell 222/223, a pair of galaxy clusters that are close together and thus should be connected by a relatively massive filament. X-ray observations had already revealed a ribbon of hot gas between the clusters — the first hint of a dark matter link. Using the Subaru telescope in Hawaii, the researchers looked at light from distant galaxies passing through the space between the clusters.
Sure enough, the distorted shapes of the galaxies revealed a thick cord of matter with a mass comparable to that of a small galaxy cluster. Gas can account for only about 9 percent of that mass. Dark matter seems to make up the rest.
The new study won’t resolve the ongoing debate over the composition of dark matter; several candidate ingredients have been proposed. But understanding the structure of filaments could help to reveal their role in building galaxy clusters by funneling in gas or whole galaxies.
“We’re starting to connect the dots,” says Meghan Gray, an astronomer at the University of Nottingham in England who wasn’t involved in the study. “In the future I expect we will extend this and see more of these filaments.” | 0.861416 | 4.03604 |
November nights are long and sometimes rainy, and each year they tend to sap our spirits. But in 2016, if you peer through holes in the clouds, you’ll glimpse a very special full moon, a few planets, and even some springtime constellations.
A supermoon worth seeing
Whenever a full moon occurs when the Moon’s elliptical orbit carries it closest to the Earth, it appears slightly larger than normal, and up to 30% brighter. During the night of November 13 to 14, the Moon will be full just a few hours past perigee, giving rise to a “supermoon”— the largest since 1948! Try to take full advantage of this opportunity, because the next perigean full moon, this size, won’t happen again until 2013.
A final glimpse of the rings
Saturn’s period of visibility nears an end. During the first few days of the month, it can be seen in the fading twilight, right before it sets. On November 2, 45 minutes before sunset, take advantage of a thin crescent moon, low in the southwest, to spot the planet 3 degrees below the lunar crescent. Dazzling Venus will complete a triangle just to the left of the duo.
For observers with a clear south-western horizon, Venus captures more and more attention, especially during the second half of the month, as it gains altitude with each passing day. Others will need some patience! In December, the dazzling planet will rise above any obscuring trees and buildings.
Mars is still visible this November. Throughout the month, the distinct reddish dot shines steadily in the south-western twilight and sets around 10:00 p.m. During the first week, Mars is to the left of the “teapot” in Sagittarius, but on the 8th, the Red Planet enters Capricornus and will be easy to identify among the constellation’s faint stars.
At night’s end, Jupiter rises in turn and is easy to spot in the constellation of Virgo, near Spica. At dawn, on November 25, the waning lunar crescent will be 4 degrees away.
Between summer nostalgia and dreams of green
At the heart of autumn, November nights offer a wide palette of constellations from all four seasons; while we reminiscence about summer and look forward to spring, the long nights are not all dreary.
As evening descends, several summer constellations can be observed in the west. The “Summer Triangle”, a misnomer, is actually visible until about 9:30 p.m. at the end of November. The Milky Way runs through the famous triangle; use it to scan our galaxy with binoculars or a telescope.
In the evening, the autumn constellations begin high in the sky, but they descend westward as the hours pass, giving way to the winter constellations, which steal the show during the latter half of the night. And after 2:00 a.m., night owls (or early risers) can easily see Leo rising in the east. A mid-November meteor shower, the Leonids, appears to radiate from this springtime constellation, but you’ll need some luck and dark skies to see any. In fact, even during the shower’s sparse maximum (10 to 20 meteors per hour), during the night of November 17, the glare of a waning gibbous moon will hamper the show.
Please refer to our seasonal sky map to identify the constellations that are visible during the evening. | 0.867849 | 3.576444 |
Researchers announced this week (January 9, 2019) at the 233rd meeting of the American Astronomical Society in Seattle, Washington, that they’ve discovered the brightest quasar yet known, detected from the period when the universe was just beginning to make luminous objects, such as stars and galaxies. Quasars are thought to be the bright cores of early active galaxies, powered by central, supermassive black holes. The extreme brightness of quasars – so bright that we can see them across a distance corresponding to most of the history of the universe – is believed to come from hot material falling into black holes. The newly discovered super-bright quasar is catalogued as J043947.08+163415.7. It shines with light equivalent to 600 trillion suns, from a distance 12.8 billion light-years from Earth.
It now holds the record for being the brightest quasar in the early universe, and, astronomers say, it might hold this record for some years to come. Astronomer Xiaohui Fan at the University of Arizona’s Steward Observatory led the team that made the discovery. He commented:
We don’t expect to find many quasars brighter than that in the whole observable universe.
This bright and remote quasar is rare. Astronomers say they searched for 20 years for such a distant quasar before finding this one. They found it via a lucky alignment; a dim galaxy is located between us and the quasar. The light of the intervening galaxy bends the light from the quasar and makes the quasar appear three times as large and 50 times as bright as it would be without this gravitational lensing effect.
Astronomer Fabio Pacucci at Yale – who co-led the discovery, plus led an analysis of its theoretical implications – commented:
For decades we thought that lensed quasars should be very common in the faraway universe, but this is the first source of this kind that we have found.
Pacucci used the term phantom quasar to describe this object, and said J043947.08+163415.7 should provide insight on how to find more such objects. He said:
These sources are difficult to detect, as our observations are misled by the presence of the lensing object, in between the faraway quasar and the Earth.
If they do exist, ‘phantom quasars’ could revolutionize our idea of the most ancient history of the universe.
Pacucci and Fan worked with an international team of astronomers to make the discovery, making use of multiple Hawaii-based observatories in their work, including Gemini Observatory, the James Clerk Maxwell Telescope, United Kingdom Infra-Red Telescope (UKIRT), the W.M. Keck Observatory, and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1). They also used the Hubble Space Telescope, which issued its own statement about the finding, saying:
Quasars similar to J043947.08+163415.7 existed during the period of reionization of the young universe, when radiation from young galaxies and quasars reheated the obscuring hydrogen that had cooled off just 400,000 years after the Big Bang; the universe reverted from being neutral to once again being an ionized plasma. However, it is still not known for certain which objects provided the reionizing photons. Energetic objects such as this newly discovered quasar could help to solve this mystery.
For that reason the team is gathering as much data on J043947.08+163415.7 as possible. Currently they are analysing a detailed 20-hour spectrum from the European Southern Observatory’s Very Large Telescope, which will allow them to identify the chemical composition and temperatures of intergalactic gas in the early universe. The team is also using the Atacama Large Millimeter/submillimeter Array, and hopes to also observe the quasar with the upcoming NASA/ESA/CSA James Webb Space Telescope.
With these telescopes they will be able to look in the vicinity of the supermassive black hole and directly measure the influence of its gravity on the surrounding gas and star formation.
Bottom line: Astronomers have discovered a quasar – labeled J043947.08+163415.7 – that they say is the brightest one yet. The quasar shines with light equivalent to 600 trillion suns, across a distance of 12.8 billion light-years.
Via Yale and SpaceTelescope.org
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says. | 0.871594 | 3.942806 |
You may have heard that astronomers spotted the largest solar system seen so far in the universe. It's actually more accurate to call it the widest solar system ever seen, thanks to a wispy waif of a ghostly gas giant planet orbiting its star at the remarkable distance of 1 trillion kilometers (approximately 621 billion miles).
Until recently, the object known as 2MASS J2126 was thought to be a free-floating lonely planet drifting through interstellar space untethered by the gravitational pull of a nearby star. But a team of American, Australian and British researchers report in the latest Monthly Notices of the Royal Astronomical Society that the planet is actually orbiting an equally lonely star at a distance about 7,000 times wider than the distance between Earth and the sun.
For further comparison, that's about seven times farther out from its star than even the hypothetical Planet 9 some think could be circling our own sun far beyond Neptune.
"This is the widest planet system found so far and both the members of it have been known for eight years," lead author Niall Deacon of the University of Hertfordshire in a release. "But nobody had made the link between the objects before. The planet is not quite as lonely as we first thought, but it's certainly in a very long distance relationship."
Gas giants, like Jupiter and Saturn, tend to be larger and made up of layers of gases surrounding a typically small rocky or metallic core. While 2MASS J2126 is a large gas giant, it's lightweight for its size and not very dense, lending it a sort of ghostly quality as it wanders around the star TYC 9486-927-1, which itself is rather lonely as it is not known to be part of any other grouping of stars.
The whole arrangement reminds me of an early job I had working in a remote radio station in Alaska. I would sit in the station by myself and broadcast news and really old Hank Williams tunes out into the wilderness. I happened to know that at the very edge of our AM signal's range there were a few trappers living in isolated cabins reachable only by boat. Like the distant pull of that star's gravity on 2MASS J2126, their only tether to civilization was that radio signal.
Those trappers would come visit me in person at the station perhaps once or twice a year to meet the voice that helped keep them sane. I know it's not quite the same thing, but if we can think of an orbit as coming home or at least returning regularly to a familiar location, then the roughly 50 orbits (each taking 900,000 years to complete) that 2MASS J2126 will make in its lifetime aren't unlike the number of visits those trappers might make to my old station in their lifetime.
More than anything, the discovery of this longest-distance relationship ever just puts space into perspective yet again. No matter how isolated an object seems to be, the odds seem to be in favor of eventually discovering that it's somehow connected to something else, no matter how distant.
It's kind of a nice thought, but not nice enough that I'm signing up to move to a remote cabin in the Arctic wilderness or undertake a mission to 2MASS J2126 anytime soon.
If you could stand on the surface of that planet, co-author Simon Murphy of the Australian National University says, the connection to your solar system's star would be tough to detect. It would probably appear just as bright as any other star in the sky, likely making any inhabitants feel just as alone in the universe as they appear to us from our own vantage point. | 0.859825 | 3.704603 |
The oxygen in Martian air is changing in a way that can't currently be explained by known chemical processes.
|Curiosity has been exploring Gale Crater, which once hosted a body of liquid water|
That's the claim of scientists working on the Curiosity rover mission, who have been taking measurements of the gas.
They discovered that the amount of oxygen in Martian "air" rose by 30% in spring and summer.
The pattern remains a mystery, but researchers are beginning to narrow the possibilities.
While the changes are most likely to be geological in nature, planetary scientists can't completely rule out an explanation involving microbial life.
The results come from nearly six Earth years' (three Martian years') worth of data from the Sample Analysis at Mars (Sam) instrument, a portable chemistry lab in the belly of the Curiosity rover.
The scientists measured seasonal changes in gases that fill the air directly above the surface of Gale Crater on Mars, where Curiosity landed. They have published their findings in the journal JGR-Planets.
The Martian atmosphere is overwhelmingly composed of carbon dioxide (CO2), with smaller amounts of other gases such as molecular nitrogen (N2), argon (Ar), molecular oxygen (O2) and methane (CH4).
Nitrogen and argon followed a predictable seasonal pattern, changing according to how much CO2 was in the air (which is in turn linked to changes in air pressure). They expected oxygen to follow this pattern too, but it didn't.
Oxygen rose during each northern hemisphere spring and then fell in the autumn.
They considered the possibility that CO2 or water (H2O) molecules released oxygen when they broke apart in the atmosphere, leading to a short-lived rise. But it would take five times more water than there actually is to produce the additional oxygen, and CO2 breaks up too slowly to generate it over such a short time.
"We know oxygen is created and destroyed on Mars through the energy provided by sunlight breaking down CO2 and H2O, both of which are observed in the atmosphere of Mars. The thing that doesn't make sense is the size of the variation - it doesn't match what we expect to see," Dr Manish Patel, from the Open University - who was not involved with the study, told BBC News.
"Given that Curiosity makes measurements at the surface of Mars, it is tempting to think that this is coming from the surface - but we have no evidence for that. Geologically-speaking, it seems unlikely - I can't think of a process that would fit."
Dr Timothy McConnochie, from the University of Maryland in College Park, who is one of the authors on the JGR-Planets paper, told the BBC: "You can measure the water vapour molecules in the Martian atmosphere and you can measure the change in oxygen... There just aren't enough water molecules.
"Mars in general has a pretty small amount of water vapour, and there's several times more oxygen atoms that mysteriously appear than there is in the water vapour on the entire planet."
They also considered why the oxygen dropped back to levels predicted by known chemistry in the autumn. One idea was that solar radiation could break up oxygen molecules into two atoms, which then escaped into space. But after running the numbers, scientists concluded it would take at least 10 years for the oxygen to disappear in this way.
In addition, the seasonal rises aren't perfectly repeatable; the amount of oxygen varies between years. The results imply that something is producing the gas and then taking it away.
Dr McConnochie thinks the evidence suggests a source of oxygen in the near-surface. "I think it points to a reservoir (of oxygen) in the soil that interchanges with the atmosphere," he said.
"To exchange (with the atmosphere) fairly rapidly on a seasonal timescale it has to be close to the surface. If it's deeper, any process is going to be slower," he told BBC News.
Some supporting evidence for this comes from Nasa's Viking landers, which touched down on the Red Planet in the 1970s. Results from the Viking Gas Exchange Experiment (GEX) showed that when the humidity was increased in a chamber containing a sample of Martian soil, it led to a release of oxygen.
However, says Dr McConnochie, the temperature in the Viking spacecraft chamber was much warmer than it would be outside, even during spring and summer. This complicates any attempt to apply the results to the Martian environment: "It's a tantalising clue, but it's not helping us solve the problem directly," he explained.
Mars does become more humid during spring and summer. Water-ice gets deposited on the poles during the winter. Then, throughout the summer, there is a release of water vapour in the polar regions.
There could be a link between the humidification of the entire planet at this time and the release of oxygen.
Intriguingly, the changes in oxygen are similar to those seen for methane, which increases in abundance by about 60% in summer for inexplicable reasons. It's unclear whether there's any connection though.
The methane mystery has attracted much attention over the years because most of Earth's methane is produced by living organisms. Though there are several ways that methane could be released by geological processes on Mars, the production of this gas by microbes living deep beneath the surface remains a tantalising possibility.
Oxygen, too, can be produced by microorganisms. The possibility that biology is behind the changing levels of the gas in the Martian atmosphere can't be ruled out. But the scientific bar on such claims is set very high indeed.
It's a very remote possibility, but we still don't understand enough about the behaviour of oxygen to use it as an indicator for life.
In addition, the near sub-surface of Mars is a very difficult place to live because of the high levels of radiation that leak through the Martian atmosphere, large variations in temperature and limited availability of water.
"With current instruments on Mars spacecraft, we have no way of knowing whether biology is producing the springtime rise in oxygen. Abiotic processes look very promising, so we'll need to firmly rule them out first before pursuing microbial contribution," Prof Sushil Atreya, from the University of Michigan, who is a co-author on the study, told BBC News.
But he added that future missions would make interrelated measurements that could shed light on Martian habitability.
Dr Patel said: "Whilst I believe biological activity in the Martian sub-surface at some point in Mars' history is a real possibility, there is no way to explain this through oxygen-producing microbes - we are missing the copious other indicators that would come along with that.
"Maybe it's all hidden, but as a scientist, I can only comment on what we observe - and an extraordinary claim requires an extraordinary observation."
The notion of oxygen being locked up in some chemical form in the Martian soil remains much more likely.
"One phenomenon that applies to most gas molecules is they stick to surfaces... especially anything with a lot of surface area. That sticking, that adsorption, changes on the basis of temperature," Tim McConnochie explained.
"Oxygen is a very active molecule, so it changes to some other form and then sticks and then changes back. The tricky thing is the forms of oxygen we know about in the Martian soil are the ones that are pretty stable."
One of these stable molecules is a compound called perchlorate, which is widespread in Martian soil. It doesn't give up its oxygen easily, but it's possible that exposure to high energy radiation - cosmic rays, for example - could make some of it break down, leaving by-products.
One potential by-product is hypochlorite - found in bleach - which is less stable and thus more prone to releasing its oxygen.
"I feel we're closer to an idea of how to release it from the soil than we are to an idea of how to sequester it back into the soil," said Tim McConnochie. But he explained: "Presumably there is some cycle that sequesters it."
Prof Atreya explained: "There are at least three potential abiotic reservoirs of oxygen in the surface/subsurface of Mars - oxidant, in the form of perchlorates; oxidant in the form of hydrogen peroxide; and oxidised rocks or hydrated minerals.
"Water-rock reactions in the past, or even today if liquid water exists beneath the surface or as brines, were most likely responsible for the third reservoir."
Dr Patel believes it may not be possible to apply the result from Gale Crater to the whole of Mars. "This has been highlighted by the recent methane measurement, where Curiosity measured a huge amount of methane, but it wasn't detectable by the NOMAD and ACS instruments on the ExoMars Trace Gas Orbiter, which makes measurements of these things at a global-scale and at higher sensitivity."
The authors of the study in JGR-Planets say they are throwing out the problem to scientists in the field, in a bid to harness expertise from across the community.
We've learned huge amounts about the Red Planet over the last few decades, but it's clear from this there are still lots of puzzles to crack. BBC | 0.841874 | 3.984469 |
Dec 13, 2019
Sediment samples indicate that there is a layer of nickel-rich ash covering the bottom of all the world’s oceans. Could cosmic plasma discharges be responsible?
The bottom of the ocean is assumed to be a dark, cold and relatively stable environment. Barring the effects of occasional earthquakes, little activity occurs and it remains in a kind of stasis, with a constant “rain” of organic detritus and inorganic minerals falling through its depths. How, then, can we explain the discovery of high nickel concentrations in the abyssal clays? Nickel is not considered a component of seawater since its concentrations are so low, and it is rare even on land.
In 1949, Professor Hans Pettersson led the first Swedish deep-sea expedition on board The Albatross. Equipped with instruments equivalent to any university’s laboratory, Pettersson and his crew extracted long cores of ocean sediments and examined their contents. What they found contradicted the theoretical assumptions of meteoric nickel drifting to Earth.
Since nickel is a component of most terrestrial meteorites, the amount being deposited on Earth can be determined by counting the meteors flaring in the night sky and estimating the mass of each object as it burns up in the atmosphere. Scientists of Pettersson’s day computed the average nickel content to be around two percent per meteor. However, when compared with the Professor’s core samples, the estimate turned out to be a thousand times too low. He wrote:
“Recent figures, published in Watson’s excellent book, Between the Planets, show that down to the faintest meteors so far studied, over ten thousand million per day enter the atmosphere, and even this figure must be taken as a minimum for the total number…None of them reaches the Earth’s surface. Instead they are converted into meteoric dust…about five metric tons or 5000 kilograms per day.”
Pettersson’s samples indicated a value closer to 10,000 metric tons per day, a figure that he considered “most enigmatic” because it implied that sometime in the past the Earth encountered a short-duration torrent of meteors. In fact, several far-ranging masses of nickel-iron may have bombarded our planet.
Since the oceans were (and are) thought to be hundreds of millions of years old, the accumulation of meteoric ash is conventionally considered to have taken place over a long period. According to Pettersson, since the fall of space debris presumably happened in days rather than millennia, he considered that his estimate of a thousand-time increase should rather be an “astronomical figure.” His conclusion was based on determining the age of the oceans, a factor that, almost 60 years later, has not yet been established.
In 1958, Lamar Worzel of Columbia University set sail on The Verma to investigate the seafloor. He discovered that a meteoric dust layer, or ash, was evenly distributed over the entire ocean bottom. The glassified substance was spread in a layer of “remarkable uniformity” and could not have been from a volcanic eruption, except the eruption of volcanoes all over the world in a simultaneous paroxysm. The other possibility was that the ash blanket came from outer space; perhaps the collision of a large comet with Earth.
Spectrographic analysis of The Verma Expedition deep sea cores
Modern theories of astrophysics portray comets as left overs from the very beginning of the Solar System. They are described as “dirty snowballs” and are said to number in the trillions, occupying a deep space halo called the Oort Cloud. However, recent information from the Stardust spacecraft reveals that the makeup of Comet Wild 2 is similar to that of rocky planets and asteroids.
In previous Thunderbolts Picture of the Day articles about comets, we predicted that they are not the icy slush and primordial elements that conventional science describes, but are recent denizens of the Solar System. As we have further suggested, comets could be debris that was hoisted into space by the electrostatic force of interplanetary plasma discharges.
Such a violent catastrophe might also have stripped millions of tons of rock from the surface of another planet, such as Mars. The electrical activity could then have projected a stream of ionized dust along the axes of gigantic Birkeland currents toward the closest node in the circuit, whereupon it would have been deposited in a process akin to cathode sputtering. That second node in the circuit was Earth, according to some Electric Universe theorists.
In conclusion, it may be that Pettersson, Worzel and the Stardust mission team are describing pieces of an event that changed the very nature of our planet and the Solar System. That event was the close encounter of Earth with another charged planetary body or bodies. The resulting exchanges of electrical energy excavated craters, scorched entire hemispheres, cut miles-deep canyons and transferred megatons of material from one body to another. The Worzel ash layer is probably a remnant of that transfer.
The Thunderbolts Picture of the Day is generously supported by the Mainwaring Archive Foundation. | 0.922973 | 3.765618 |
Many processes can cause climate to change. These include changes in the amount of energy the Sun produces over years; the positions of the continents over millions of years; in the tilt of Earth’s axis; orbit over thousands of years; that are sudden and dramatic because of random catastrophic events, such as a large asteroid impact; in greenhouse gases in the atmosphere, caused naturally or by human activities.
Plate tectonic movements can alter climate. Over millions of years as seas open and close, ocean currents may distribute heat differently. For example, when all the continents are joined into one supercontinent (such as Pangaea), nearly all locations experience a continental climate. When the continents separate, heat is more evenly distributed.Plate tectonic movements may help start an ice age. When continents are located near the poles, ice can accumulate, which may increase albedo and lower global temperature. Low enough temperatures may start a global ice age.
Plate motions trigger volcanic eruptions, which release dust and CO2 into the atmosphere. Ordinary eruptions, even large ones, have only a short-term effect on weather. Massive eruptions of the fluid lavas that create lava plateaus release much more gas and dust, and can change climate for many years. This type of eruption is exceedingly rare; none has occurred since humans have lived on Earth.
The most extreme climate of recent Earth history was the Pleistocene. Scientists attribute a series of ice ages to variation in the Earth’s position relative to the Sun, known as Milankovitch cycles. The Earth goes through regular variations in its position relative to the Sun:
The shape of the Earth’s orbit changes slightly as it goes around the Sun. The orbit varies from more circular to more elliptical in a cycle lasting between 90,000 and 100,000 years. When the orbit is more elliptical, there is a greater difference in solar radiation between winter and summer.
The planet wobbles on its axis of rotation. At one extreme of this 27,000 year cycle, the Northern Hemisphere points toward the Sun when the Earth is closest to the Sun. Summers are much warmer and winters are much colder than now. At the opposite extreme, the Northern Hemisphere points toward the Sun when it is farthest from the Sun. This results in chilly summers and warmer winters.The planet’s tilt on its axis varies between 22.1 degrees and 24.5 degrees. Seasons are caused by the tilt of Earth’s axis of rotation, which is at a 23.5o angle now. When the tilt angle is smaller, summers and winters differ less in temperature. This cycle lasts 41,000 years.
When these three variations are charted out, a climate pattern of about 100,000 years emerges. Ice ages correspond closely with Milankovitch cycles. Since glaciers can form only over land, ice ages only occur when landmasses cover the polar regions. Therefore, Milankovitch cycles are also connected to plate tectonics.
The amount of energy the Sun radiates is variable. Sunspots are magnetic storms on the Sun’s surface that increase and decrease over an eleven-year cycle. When the number of sunspots is high, solar radiation is also relatively high. But the entire variation in solar radiation is tiny relative to the total amount of solar radiation that there is and there is no known eleven-year cycle in climate variability.
The Little Ice Age corresponded to a time when there were no sunspots on the Sun.
Changes in Atmospheric Greenhouse Gas Levels
Since greenhouse gases trap the heat that radiates off the planet’s surfaces what would happen to global temperatures if atmospheric greenhouse gas levels decreased? What if greenhouse gases increased? A decrease in greenhouse gas levels decreases global temperature and an increase raises air temperature.
Greenhouse gas levels have varied throughout Earth history. For example, CO2 has been present at concentrations less than 200 parts per million (ppm) and more than 5,000 ppm. But for at least 650,000 years, CO2 has never risen above 300 ppm, during either glacial or interglacial periods. Natural processes add (volcanic eruptions and the decay or burning of organic matter) and remove absorption by plants, animal tissue, and the ocean) CO2 from the atmosphere. When plants are turned into fossil fuels the CO2 in their tissue is stored with them. So CO2 is removed from the atmosphere. What does this do to Earth’s average temperature?
Fossil fuel use has skyrocketed in the past few decades more people want more cars and industrial products. This has released CO2 into the atmosphere.
Burning tropical rainforests, to clear land for agriculture, a practice called slash-and-burn agriculture, also increases atmospheric CO2. By cutting down trees, they can no longer remove CO2 from the atmosphere. Burning the trees releases all the CO2 stored in the trees into the atmosphere.
There is now nearly 40 percent more CO2 in the atmosphere than there was 200 years ago, before the Industrial Revolution. About 65 percent of that increase has occurred since the first CO2 measurements were made on Mauna Loa Volcano, Hawaii, in 1958. CO2 is the most important greenhouse gas that human activities affect because it is so abundant. But other greenhouse gases are increasing as well. A few are:
- Methane: released from raising livestock, rice production, and the incomplete burning of rainforest plants.
- Chlorofluorocarbons (CFCs): human-made chemicals that were invented and used widely in the twentieth century.
- Tropospheric ozone: from vehicle exhaust, it has more than doubled since 1976. | 0.83933 | 3.716344 |
In part one of this article, I ended it with the Sun and its part related to Earth, sunrise and sunset. Now we will take a flight towards space, starting from our Sun. In order to understand this article properly (wavelength and stuff), you must first read part one.
As we transition from Earth’s atmosphere to Space we see that the Sun appears white, for the reasons that I mentioned in the last article. Our Sun produces light because of the nuclear fusion reaction going at it. Fusion, the one that produces melodies in music and here in the Sun, it produces light. Hydrogen combines to form helium and in this process, there is a release of energy. That energy comes out in the form of heat and light (photons). It is not an easy journey for a photon. It takes thousands of years for it to reach from the core to the Sun’s surface. It can take even 100 times more than the normal time and it is not possible to exactly pinpoint that how much time it takes as it varies but yes, it takes really long time. The density is high inside, so there are collisions and absorption and re-release of a photon by other atoms present there. This is the way by which all the stars produce light, Sun is a star after all. Then why do we see stars as yellow, red or blue depends on the temperature of a star. Hotter ones are blue and the ones that are cool are red. It’s the game of wavelength, stars that give out the light of shorter wavelength are blue and the ones that give out longer wavelength light are red.
The division of stars written below with respect to temperature shows how the color is related to the temperature (source – outerspaceuniverse.org)
3,000° – 6,000° Fahrenheit (1,649° – 3,316° Celsius): Type M
6,000° – 8,500° Fahrenheit (3,316° – 4,704° Celsius): Type K
8,500° – 10,500° Fahrenheit (4,704° – 5,816° Celsius): Type G
10,500° – 13,000° Fahrenheit (5,816° – 7,204° Celsius): Type F
13,000° – 17,500° Fahrenheit (7,204° – 9,704° Celsius): Type A
17,500° – 50,000° Fahrenheit (9,704° – 27,760° Celsius): Type B
50,000° – 100,000° Fahrenheit (27,760° – 55,538° Celsius): Type O
Type M stars: Red
Type K stars: Orange
Type G stars: Yellow-White
Type F stars: White
Type A stars: White
Type B stars: Blue-White
Type O stars: Blue
Talking about our Moon and the rest of the planets in our solar system, they just reflect Sun’s light and what they reflect depends on what they are made up of or what they contain, the atmosphere, elements etc.
Phases of Moon are because of the sunlight falling on it from different directions.If we see crescent Moon we will also notice that its non-illuminated part shows a particular amount of glow,not so bright, but visible.That is when the Sun’s light is reflected from Earth towards Moon.That glow over the unlit part of a crescent moon is called Earthshine.It is a beautiful phenomenon.In astronomy, a crescent is a shape of the lit side of a spherical body (most notably the Moon) that appears to be less than half illuminated by the Sun as seen by the viewer.
Below is an amazing picture of Earthshine.
Space is dark, but why? We see the light when it is reflected back towards us by anything or we see it coming from a source that produces it. But in the void of space, there is nothing. But here the things get interesting. There is dark matter, where we see nothing, the reason being it can’t be detected yet. What is the point if we are able to “see” it? Then it would become just like the matter that we are able to see. It is still a mystery, we are so sure about its presence because the stars are moving around faster than what would have been possible with gravity alone. There is something else that is affecting their motion, something not visible and thus, we call it dark matter.
(This image from the Dark Universe shows the distribution of dark matter in the universe, as simulated with a novel, high-resolution algorithm at the Kavli Institute of Particle Astrophysics & Cosmology at Stanford University and SLAC National Accelerator Laboratory.
Credit: © AMNH)
We see many other wonders of light in space. Talk about galaxies, their light is the light of their constituents, i.e. stars and a few other objects like the marvelous nebula. A nebula is a cloud of gas and dust, which glows with beautiful colors caused by different elements in or around them. Collectively, we call them Nebulae. I have never seen anything wonderful than these.
Now, these are of different kinds and such are their colors. These can be categorized as Emission nebulae, Reflection nebulae, Planetary nebulae, Dark nebulae and Supernova remnants.
An emission nebula is a cloud of gas and dust, which glows because the atoms are charged by the energy of a star and when these atoms lose energy they lose it in the form of emission of red light. They are red because hydrogen is in abundance; red is the dominating color, though they can have traces of other colors too. The Orion nebula is an example.
Reflection nebula, as the name suggests, reflects light from a nearby star or group of stars unlike emission nebula (which produces its own light). These are mostly blue because blue light is reflected more. An example is the Trifid nebula.
A planetary nebula is a shell of gas produced by a star when it is near its end. It is illuminated by the star present at its center. These are called planetary nebulae because they just look like one.(Example – The Ring nebula)
A dark nebula is a cloud of gas and dust that blocks the light of a star because of its position with respect to that star. These are usually seen together with emission and reflection nebulae. Horsehead nebula in the Orion nebula is the best example.
Supernova remnants, as the name suggests, are the leftover of a supernova explosion (death of a star). As the star blasts its expelled material forms cloud around its remains. This glows with the remains of the star that exploded. (Crab nebula)
Type “space images” into Google and you will mostly see images of Nebulae.
There are also other objects like pulsars, but these are not visible in optical telescopes as they emit radio waves, not visible to naked eyes. These are highly magnetized neutron stars.
A black hole is the most amazing thing that has ever been known or more precisely, Hypothesized. They have powerful gravity, which doesn’t allow even light to escape!! The reason nothing can escape a black hole is because within the event horizon (it is defined as “the point of no return”, i.e., the point at which the gravitational pull becomes so great as to make escape impossible), space is curved to the point where all directions are actually pointing inside.
Yes, I know, a Black hole deserves a special article and thus that would be my next article. I will also be writing articles about other marvelous celestial objects which we see through the eyes that we have made like Radio telescopes etc.
The beautiful featured image at the top;
The South American artist and musician, Pablo Carlos Budassi, captured in his universe map the outer rings of the Milky Way, the neighboring Andromeda galaxy and other star formations, then encircled these star clusters with a ring of plasma left over from the Big Bang.(www.rt.com)
See the full resolution image here,you will be stunned I bet and don’t forget to zoom in after downloading it.
“It is because of the flight of light
We know the Universe
From minutes to million years
Having wings of time
Call it a bird”
Article and poem by
- Jaskaran Singh | 0.842984 | 3.661495 |
If, in 2009, you asked 18-year-old me to name an exoplanet, then Gliese 581d would have been it. Discovered by an American team of astronomers in 2007, it was, for a long time, the poster child for exoplanetary science. Not only was the first rocky world ever found in the habitable zone of its star where life-friendly temperatures are found, it was also relatively nearby (for astronomy standards) at only 20 light years.
Astronomers used the radial velocity technique to find the first planet around Gliese 581 as far back as 2005. This method relies on the gravitational pull that a planet has on a star as it orbits. This wobble is detectable in the spectra of the starlight, which gets doppler shifted as the star moves back-and-forth, allowing the period and mass of an orbiting planet to be determined. While the first planet, ‘b’, orbited close to the star with a period of only 5.4 days, it was joined by two cooler (and more habitable) planets, ‘c’ and ‘d’ in 2007. This was soon followed in 2009 by Gliese 581e, the smallest planet in the system on an even shorter (3.1d) orbit.
Things started to get even more confusing in 2010 when observers at the Keck observatory announced two more planets (‘f’ and ‘g’) orbiting at 433 and 37 days respectively. This would put ‘g’ between ‘c’ and ‘d’ and right in the middle of the star’s habitable zone. However, new observations of the star with a Swiss telescope showed no such signal. Was there a problem with the data, or could something else be mimicking these planets?
One problem comes when we consider the star itself. Just like our own sun, most stars are active, with starspots skimming across the surface and convection currents in the photosphere causing noise in our measurements. These active regions can often mimic a planet, suppressing the light from one side of the rotating star and shifting the spectra as if the star itself were moving back-and-forth. Add to that the fact that, like planets, activity comes and goes on regular timescales and that cool stars such as Gliese 581 are even more dynamic than our pot-marked sun, and the problem becomes apparent.
The first planet to bite the interstellar dust was ‘f’. At 433 days, its orbit closely matches an alias of the star’s 4.5-year activity cycle, and it was quickly retracted in 2010. Similar analyses with more data also suggested Gliese 581g was also likely to be an imposter, but the original team stuck by this discovery. For the last 3 years, this controversy has simmered, until last month all the data available for Glises-581 was re-analysed by Paul Robertson at Penn State. This showed that not only is Gliese 581g not a planet, but that the poster child itself, Gliese 581d, was also an imposter.
To do this, the team took all 239 spectra of GJ581 and analysed not just the apparent shift in velocity, but the atomic absorption lines themselves. Using the strength of the Hα absorption line as an indicator for the star’s activity, they compared this to the residual radial velocity (after removing the signal from planet b). This showed that there was a relatively strong correlation between activity and RV, especially over three observing seasons when the star was in a more active phase. They also found that this activity indicator varied on a 130 day timescale.
When the team removed the signal from stellar activity, they found that planets ‘c’ and ‘e’ were even more obvious than in previous searches. However the signal for planet ‘d’ dropped by more than 60%, way below the threshold needed to confirm a planet. Even more remarkably, ‘g’ does not appear at all. So what exactly caused this ghostly signal. The planet’s orbital period of 66 days gives us a clue -it is almost exactly half that of the star’s 130 day rotation cycle, so with a few fleeting starspots and the right orientation, a strong planet-like signal at 66 days results.
This case of mistaken identity is a sad one, but thanks to the incredible progress of our field in the last 5 years, their loss barely makes a dent in the number of potentially habitable exoplanets known. Instead, it acts as a warning for planet-hunters: sometimes not all that glitters is gold. | 0.940382 | 4.003096 |
Target: Rings and Moons
"Since its arrival to Saturn, the Cassini-Huygens satellite has been observing various celestial bodies and helped unravel many different mysteries about the solar system. Nevertheless, it has not fully analyzed the rings and moons of Saturn, specifically Enceladus and Tethys. Since these particular moons and rings will soon be in alignment, allowing the Cassini-Huygens satellite to analyze them simultaneously, NASA should prioritize targeting this section of Saturn.
Saturn's rings have many interesting yet still not well understood characteristics which deserve closer analysis using the Cassini-Huygens satellite. Even though its rings are Saturn's most distinctive characteristic, scientists remain oblivious to the complicated functions and specific compositions of the rings. In fact, it has only been very recently discovered that the rings have an atmosphere that interact with the surface of Saturn and actually produces rain. These speculations could be verified through the closer analysis of Saturn's rings using the Cassini-Huygens satellite. These further observations will broaden our understanding of both the rings and their interaction with Saturn.
Moreover, observing the moons of Saturn will allow us to have a greater understanding of their geology and their potential to contain extraterrestrial life. Scientists will be able to examine Enceladus, the sixth-largest and most interesting moon of Saturn, by analyzing this target. It is particularly significant because it is considered by many scientists to be the most likely place for extraterrestrial life to exist in the solar system. In fact, Enceladus has cyrogeysers that actually shoot water vapor into the atmosphere, even occasionally reaching past its atmosphere and into space. There are also a number of different elements there that are conducive to the possible development of life, such as a large internal water ocean.
Furthermore, this observation will enable further research on another moon of Saturn, the mysterious Tethys. Very little is known about this moon, other than the fact that it contains a large amount of water ice. The large amount of water ice that exists there could have potentially been liquid in the past and thereby making the chances of life existing there at some point actually possible. In addition, scientists do not know what other elements exist on the planet and the potential composition of those substances as well. By further analyzing this mysterious moon, scientists can answer these unsolved mysteries and learn about the various elements and possible life forms that may have existed there.
The Cassini Project would be best served by analyzing Saturn's rings and its surrounding moons. They contain the most promising candidates for further study because of its relatively higher chances of containing life and the mysterious nature of the different targets in the area. Using the Cassini-Huygens satellite to explore this particular area over others is essential towards enhancing our understanding of the solar system in general." | 0.800964 | 3.634386 |
For objects that have been extremely close to Earth on astronomical scales long before humans walked on the planet, there is still quite a large amount of information that is unknown about asteroids. According to one study, “…astronomers did not consider asteroids as subjects worthy of study in their own right…until the latter half of this century.”
Now it seems that not only are people learning that there is a wealth of information to be derived from these space vagabonds in regards to mineralogy and planetary dynamics, but they also realize that some asteroids may be potential threats to Earth; should an asteroid large enough be headed for a collision with it.
Facts about Asteroids
- Asteroids are rocky objects that orbit the Sun, with diameters of less than 1000 kilometers at their widest point.
- There are two major types of asteroids when classified by composition: Carbonaceous (C) and Silicaceous (S) types. They can further be subdivided into other groups from these two major types.
- These phenomena can also be classified by their location in the solar system. Several groups are much closer to the Sun than the main belt, such as the Aten and Apollo groups. Others, like the Trojan and Centaur groups, lie further than the main belt.
What are Asteroids?
Asteroids can be defined as rocky masses that orbit the Sun, with sizes that measure from small dust particles to a maximum of 1000 kilometers wide at their longest width. Most people know of asteroids as the giant ‘belt’ of space rocks that lies between the planet Mars and the planet Jupiter. This is absolutely a true description – but there are more of these space phenomena that lie elsewhere in Earth’s solar system, including a group called the Centaur Group that extend from Jupiter’s orbit to distances as far as Pluto.
One of the prevailing theories regarding the origin of the main asteroid belt between Mars and Jupiter, is that the asteroids would have formed another planet at the same time the other planets of solar system were forming, but Jupiter’s (and possibly the other gas giants’) gravitational pull was so massive that it prevented this additional planet from ever forming.
Classifications of Asteroids
Multiple asteroid classification systems have been developed over the last 40 years. As technology has become more advanced, and individuals have become better able to observe and identify additional features of asteroids, the classification systems have adapted and become more sophisticated. Initially, asteroids were identified by the light they were reflecting from the sun, and were classified only by variations in the visual spectrum. Later, as equipment and processes became more advanced, classification systems began to add the near-infrared part of the spectrum to the already existent visual spectrum classes.
The first classification was developed in 1975, by Clark Chapman, David Morrison, and Ben Zellner. This classification system separated asteroids into 3 classes, a “C” class, for carbonaceous asteroids, an “S” class for silicaceous asteroids, and a “U” class for asteroids which did not fall into either the “C” class or the “S” class. The next major classification system developed was the Tholen classification system, developed by David J. Tholen in 1984. The Tholen classification system
divided the 3 groups defined in the initial classification system into subgroups, and added 6 additional classes; A-type, D-type, T-type, Q-type, R-type, and V-type asteroids. In 2002, Schelte J. Bus and Richard P. Binzel, using data from MIT’s Small Main-belt Asteroid Spectroscopic Survey (SMASS) taken at the Kitt Peak Observatory, created a more advanced classification system. This classification system consisted of 26 classes, and was based on slope values over various sections of the spectral curve
Asteroid Classification by Composition
|C||B||Asteroids with low hydrous amounts|
|C||Typical carbonaceous asteroids|
|Cb, Cg, Cgh, Ch||Transitional carbonaceous|
|S||A||Silicaceous, rich in Olivine|
|Q||Olivine and Pyroxene are present|
|R||Rich in Olivine and Pyroxene|
|K||Moderate red spectrum less than .75 um|
|L||Strong red spectrum less than .75 um|
|S||Typical silicaceous asteroids|
|Sr, Sq, Sa, Sv||Transitional silicaceous|
In 2007, members of that group, along with Francesca E. DeMeo, a student at MIT, developed the Bus-DeMeo classification system (Figure 1) to include asteroids which appeared in the near-infrared part of the spectrum. This is the most recent classification system, but most likely it will not be the last. It is important to note that throughout the last 40 years there have been additional classifications systems to the ones listed in this paper (the one listed in the book is by Hartmann in 2005), however, the classification systems described above serve as landmark classification systems.
Carbonaceous Asteroids (B and C-types)
B and C-type asteroids fall under the category of “carbonaceous asteroids”. Obtaining spectra from carbonaceous chondrites can be challenging, due to the low reflectivity of their surface elements. These asteroids often show absorption lines near 3 um which shows a presence of hydrous minerals such as phyllosilicates. There are variations in the strength or intensity of the absorption lines, which is a main reason for the division of the two classes. Spectral analysis of B-type asteroids shows that surface elements may include anhydrous silicates, hydrated clay minerals and other elements. The albedo of B-type asteroids is generally higher than C-type asteroids, but the albedos of both groups are relatively small compared to other groups of asteroids.
Two examples within these two groups, Ceres and Pallas, were once classified together as C-type asteroids, but are now classified as Cg and B-type asteroids, respectively, due to the strengths of their absorption lines around 3 um. To be specific, Pallas has a much lower 3 um absorption line than Ceres, showing a lower amount of hydrous materials on Pallas.
In the Tholen (1984) classification system, the C class was split into B, C, G and F classes. In the Bus-DeMeo system, G-type asteroids are again classified as sub-types of C-type asteroids, as the categories labeled Cg and Cgh-types. The F class and B class cannot be differentiated in the new Bus system so they are grouped together under the B-type class. The C-type class of asteroids is currently the largest class of identified asteroids, with the B types being less common. C-types may actually comprise a larger percentage of the entire asteroid population than is currently thought, but due to the low albedo of the class discovery is more difficult than other classes. C-type asteroids are located throughout the main belt and outer belt.
Silicaceous Asteroids (S, A, Q, R and K-types)
S-type asteroids are often referred to as typical S-group asteroids. The “S” stands for silicaceous, which means stony. Scientists are not yet entirely sure of the total compositions of S-type asteroids; however, they are classified as being silicates. Some S-type asteroids are stony-irons, while others may be composed mostly of silicaceous materials. Chapman describes the S-class of asteroids as a “…grab bag of silicate-bearing objects, whatever the final proportions may turn out to be.” In the Bus-DeMeo classification system, Sa, Sl, Sk, and S-type asteroids have been condensed into 2 classes; the S and Sv classes. The Sq and Sr classes have been expanded into 3 classes; the Sr, Sq and Sa classes. In general, silicaceous asteroids have much higher albedos than the previously discussed Carbonaceous Asteroids.
Eros is a well known S-type asteroid. It was the first Near-Earth Asteroid (NEA) discovered and is one of the largest asteroids discovered to date. In 2001, the NEAR Shoemaker probe orbited, photographed, and then landed on Eros’ surface. Some theories state that millions of tones of aluminum, gold and platinum are lodged in Eros.
A-type asteroids are most often located in the main asteroid belt. A-type asteroids are classified as asteroids that are rich in the mineral Olivene (4), showing an asymmetric absorption band with a minimum near 1 um (1). Olivene is a material that is often found at the bottom of magma chambers (4), which may be a clue to the origin of A-type asteroids. A-type asteroids represent a very small percentage of the total asteroid belt. To date, very few asteroids have been classified as being an A-type asteroid. One of those is Asteroid (1951) Lick, discovered by C.A. Wirtanen in 1949.
As of 2004, only 4 asteroids have been classified as R-type asteroids. R-type asteroids are spectrally similar to V-type asteroids, with absorption lines around 1 and 2 um (1), and reflectance around .75 – .92 um (8). R-type asteroids are likely rich in olivine and pyroxene.
K-type asteroids are also rare. They have a moderately red spectrum less than .75 um (12). K-type asteroids have a shallow absorption feature at 1 um and no absorption feature at 2 um (12).
Little is currently known about the compositions of X-type Asteroids. The X-type Asteroid class consists of 3 different classes defined by Tholen in 1984, the E class, the P class, and the M class, now grouped together in the Bus-DeMeo system. X-type asteroids are defined as “indistinguishable on the basis of their visible-wavelength spectral properties as found in principle components analysis of the Eight Color Asteroid Survey data of 589 asteroids.” (10) One of the defining characteristics that separates these classes is their albedo. E class asteroids are high-albedo objects, P-types are low-albedo objects, and M-types are intermediate-albedo objects (10). E-type asteroids possibly have Enstatite achondrite surfaces (15), and are most prominent in the inner belt. Enstatite achondrites are theorized to possibly be fragments of larger, highly differentiated asteroids.
Xe, Xc, and Xk-type Asteroids
Essentially, the Xe, Xc and Xk classifications are based entirely on spectral features. Xe asteroids have an absorption feature at .49 um. Xc objects have a broad, convex curvature from .55 – .80 um. Xk asteroids have similar curvatures, with the difference being a slope of greater than .26 from .55 – .70 um (10). The labels Xc, Xk and Xe describe potential relationships with asteroids from the related classes (e.g. Xc would have similarities with asteroids from the C-type class of asteroids).
Kuiper Belt and Oort Cloud objects
In 1992, the Kuiper Belt was discovered by David Dewitt and Jane Luu when they found a small planetesimal lying beyond the known solar system. Many more objects in this outer region have since been discovered, but their composition is still somewhat of a mystery. It is entirely possible that these objects are composed of more ice than rock, and as asteroids are defined as ‘rocky’ objects, it is difficult to know if KBOs (Kuiper Belt Objects) are to be considered ‘asteroids’ or something else.
Similarly, even less is known about the Oort Cloud, a region that lies beyond the Kuiper Belt and is theorized to envelope the solar system in a ‘sphere’ of icy objects. These objects may eventually be classified as comets or again, something else entirely. | 0.863396 | 3.814296 |
Mars has an active surface, with omnipresent small dust particles and larger debris. With an ambient pressure below 10 mbar, which is less than 1% of the surface pressure on Earth, its CO2 atmosphere is rather tenuous. Aeolian processes on the surface such as drifting dunes, dust storms and dust devils are nevertheless still active1,2,3. The transport of volatiles below the surface, that is, through the porous soil, is unseen but needs to be known for balancing mass flows4,5. Here, we describe a mechanism of forced convection within porous soils. At an average ambient gas pressure of 6 mbar, gas flow through the porous ground of Mars by thermal creep is possible and the soil acts as a (Knudsen) pump. Temperature gradients provided by local and temporal variations in solar insolation lead to systematic gas flows. Our measurements show that the flow rates can outnumber diffusion rates. Mars is the only body in the Solar System on which this can occur naturally. Our laboratory experiments reveal that the surface of Mars is efficient in cycling gas through layers at least centimetres above and below the soil with a turnover time of only seconds to minutes.
As a terrestrial planet, Mars shares many geological and physical processes with Earth6. However, the martian environment is unique with respect to at least one point. It is the only Solar System body with an atmosphere of significant but low surface pressure of on average 6 mbar. Consisting mostly of CO2, this surface pressure corresponds to a mean free path of the gas molecules of 10 μm at a temperature of 218 K. Of central importance is that this mean free path is comparable to the size of the dust particles and to the pore size within the martian soil7. A concept from the early days of rarefied gas physics is that under these conditions—mean free path comparable to or larger than the size of a structure—a pore can act as an efficient pump, purely by applying a temperature difference to its ends8. In other words, if one side of a thin channel is warmer than the other side, this channel transports gas from the cold to the warm side along its walls8,9,10. This effect is called thermal creep, which can be understood as follows. Let there be a closed reservoir of gas at a temperature T. If a small hole is provided, the gas flow rate (number of particles per time and area) through this opening is proportional to the thermal velocity of the gas molecules multiplied with the density (vtherm × n). Assuming an ideal gas, this is proportional to the pressure over the square root of the temperature . The lower the temperature at a given pressure, the higher the gas flow. If two reservoirs of the same pressure but at different temperatures are now connected, a net flow from the cold to the warm reservoir results. This argument applies only if the connection between the two reservoirs is smaller or comparable to the mean free path of the molecules and no interaction between gas molecules occurs within. On the basis of this effect, in 1909 Knudsen8 measured a compression ratio in gas pressure of about a factor of 10 between the two ends of a series of small channels with a diameter of 0.6 mm at sub-millibar pressure. If the pore or the channel is too large compared with the mean free path, a backflow of gas in the centre of the channel inhibits the efficient transport along the channel9,11. Therefore, for a dusty soil with micrometre particles, this effect is seen only at millibar pressure. This enables thermal creep through the porous soil of Mars with its low-pressure atmosphere to act as an efficient pump if temperature gradients are present. Thermal creep is similar to, but not to be confused with thermophoresis of gas molecules in a temperature gradient. This has also been considered for transport in soil as thermodiffusion, but has been estimated to be very inefficient on Mars12. Gas flow in martian soil also occurs owing to the expansion and contraction during diurnal temperature variation. This also occurs between the two reservoirs at two different temperatures as considered above, but these are one-time equilibrations. In contrast, thermal creep occurs continuously along a temperature gradient. It should be noted that pumping on Mars usually refers to net vertical transport of H2O in diurnal temperature cycles13. The thermal creep soil pump considered here has to be distinguished from this.
The gas mass flow rate M through channels due to thermal creep has been quantitatively described as11
where pavg and Tavg are the average ambient pressure and temperature, r is the channel radius and l is its length. ΔT is the temperature difference between the channel ends, kB is the Boltzmann constant and m is the mean molecular mass of the ambient gas. Q is a factor depending on the Knudsen number. It specifies the balance between thermal creep and pressure-induced backflow. It is Q∼0 at high pressure where the mean free path is much smaller than the pore size as, for example, on Earth.
Under gravity the dominant gas flow above an illuminated and hence heated dust bed is the thermal convection. This motion is restricted to the space above the soil. A component due to gas flow through the soil by means of thermal creep is not easily discerned under gravity in the face of thermal convection. We therefore carried out experiments with an illuminated dust bed at the drop tower in Bremen (Germany) where residual gravity is below 10−6 g for approximately 9 s (Methods). We used basalt with a broad size distribution up to 125 μm and a gas atmosphere with a 4 mbar ambient air pressure. In the work reported here we analyse the gas flow by observing the motion of tracer dust particles. We use particle eruptions similar to those discussed in refs 14 and 15 to generate tracer particles to study the gas flow through the porous dust bed on illumination.
Without gravity thermal convection does not exist and gas flow due to thermal creep can be observed unbiasedly. An absence of convective eddies can be demonstrated in the experiments for an illuminated solid surface. The tracer particles move only within the illuminated spot owing to photophoresis—a particle motion by light-induced temperature differences over the dust particles. No motion is visible for dust particles if not illuminated directly. This translates to no significant gas flow being present.
This changes once the basaltic dust bed is exposed to the light source. A convective flow pattern becomes visible (Fig. 1a). We note again that the experiments are carried out without gravity and the convection is not a thermal convection. The tracer particles follow the gas streamlines and enter the dust bed in the non-illuminated part tracing a gas flow into the soil (Fig. 1).
At a radiation flux of 13 kW m−2 the upward velocity is about 10 cm s−1 within the illuminated spot and downward velocities outside the illuminated spot are about 1 cm s−1 (Fig. 2). The inflow of gas extends to the outer end of the dust bed. The fact that gas also enters the soil at the outer extension 1.5 cm away from the spot indicates that the flow within the soil is reaching down to the bottom of the dust bed 2 cm below the surface. This is consistent with a model of forced flow through the porous medium as seen in Figs 1b and 3.
As the experimental conditions compare well to the martian environment (detailed below), the results can readily be applied to Mars and reveal the following picture: if the martian soil is heated by solar insolation, gas will be pumped from the colder soil layers beneath the heated layers towards the surface.
At shadowed places on the surface, gas will efficiently be soaked up into the soil, traverse the underground and will be pumped up again to the heated (insolated) surface as shown in Fig. 4. Therefore, the resulting gas flow below the surface is a mixture of a vertical and a horizontal flow. In this simple picture, shadowed regions are needed as a continuous (atmospheric) reservoir of gas. As pores in soil act like micro-channels and as dust particles and pores exist in the micrometre range, the low atmospheric pressure on Mars is ideally suited to provide its soil with the ability for natural thermal creep pumping. The capability of gas flowing through heated or insolated dust layers can also lead to a significant pressure increase. It can even be sufficient to levitate large dust aggregates or to eruptively eject particles from the surface, which has been shown in ground-based laboratory experiments10,14,15,16,17.
To evaluate the gas mass flow in the drop tower experiments we use equation (1), with pavg = 4 mbar and Tavg = 300 K. For a length of l = 2 cm (depth of the dust bed) and basaltic powder with a thermal conductivity of 0.01 W K−1 m−1 (ref. 18), we get ΔT = 300 K (ref. 15). In a simple model of hexagonally packed spheres, the radius of a capillary is about 20% of the sphere radius; therefore, we assume r = 0.2rparticle with rparticle = 50 μm. The molecular mass of the air is m = 28.96 AMU and kB = 1.37 × 10−23 J K−1. The mean free path of air in the experiments is λ = 17.5 μm. This results in a Knudsen number K n = (λ/2r) = 0.875. For this Knudsen number, we take the Q-value from ref. 11 of Q = 0.36. This leads to a gas mass flow of 10−14 kg s−1. Divided by the cross-section of one capillary A = 10−10 m2 and the density of air at 4 mbar ambient pressure ρ = 4.8 × 10−3 kg m−3, we get a mean gas velocity of 9 cm s−1, which is consistent with the velocities measured in the experiment.
Scaling this to martian conditions we have to consider CO2 instead of air, which has a molecular mass of = 44 AMU. With a geometric radius of 4.63 × 10−10 m (ref. 19) the molecule has a cross-section of σ = 1.6 × 10−19 m2. At p = 6 mbar, T = 218 K and a particle density n = p/kBT, the mean free path of CO2 is . According to this mean free path, the Knudsen number is 1.05 and hence Q = 0.31 (ref. 11). Owing to the lower insolation of about 700 W m−2, a smaller temperature difference than in the experiment is obtained. As a first estimate, we assume the typical diurnal surface temperature variation as ΔT = 50 K. Assuming the same thermal conductivity of 0.01 W K−1 m−1, a length of 2 cm and an average particle radius of 50 μm, the CO2 gas mass flow is the same as the air mass flow in the experiments with 10−14 kg s−1. Divided by the cross-section A∼10−10 m2 and the density of CO2 at 6 mbar ambient pressure ρ = 14.6 × 10−3 kg m−3, the result is a mean gas velocity of 1.6 cm s−1 on Mars.
The details of the martian gas pump will depend on the local light flux, which varies with daytime and shadow-casting landmarks. It also depends on the detailed soil characteristics such as pore size, albedo and thermal inertia.
Mars is known to have buried ice within its subsurface20 and water vapour can be transported by diffusion to the surface12. Ref. 21 estimated the diffusion constant of water vapour in a martian simulant (JSC Mars-1 Dust) at 6 mbar ambient pressure to 1.5 cm2 s−1. Diffusive flow might roughly be estimated to 0.3 cm s−1 for a 5 cm layer then. This is below the pump velocity found in the experiments scaled to martian conditions. The thermal creep gas flow hitherto unconsidered might therefore be a dominant transport mechanism for water vapour in large parts of the martian soil as it is dragged along with the CO2.
Basalt dust beds were studied here, which we regard as a suitable analogue to martian dust22. However, essentially all light-absorbing dust samples show effects of thermal creep in ground-based laboratory experiments on illumination (Methods).
The natural soil pump on Mars is probably leaky, acting locally in many different ways. This natural, potentially planet-wide pump is tied to the ambient pressure and has no analogue on Earth or any other planet known in the Solar System. It certainly has an influence on the gas cycle and the soil atmosphere interaction on Mars. As the directed CO2 gas flow carries along the other gas species as well, it also has to be considered for water transport through the soil.
The experiments were carried out at the drop tower in Bremen (Germany) in a catapult mode. A sketch of the experiment is shown in Fig. 5.
A basaltic dust sample is placed inside a vacuum chamber. This chamber is evacuated after preparation to a preset value of 4 mbar.
During the launch the dust bed is covered by a lid to prevent particle loss during tension release. After 300 ms in microgravity the lid is opened. The dust sample is illuminated by means of a red laser (655 nm) with a spot diameter of 8 mm. The light flux is varied between 13, 9 and 6 kW m−2. The laser is turned on 4 s before the launch. The light flux is chosen as high so that once the lid is opened, particle eruptions due to a solid-state greenhouse effect and photophoresis occur10,14,16: the solid-state greenhouse effect is mostly known for transparent bodies such as dirty ice23. Visible radiation enters the medium and the absorption heats it within. As thermal radiation cannot escape because ice is opaque at this wavelength, the ice heats up below and is cooler at the surface (greenhouse effect). The same can occur for dust samples as visible light enters through the pores or forward scattering and thermal radiation cannot leave the same way17,24. In this study, this is a minute detail, as it influences only the top dust layer of about 100 μm and does not change the coarser temperature structure of the sample. However, the temperature gradient is sufficient to lead to an upward-directed photophoretic force on particles in the top layer that can eject particles from the surface at high light flux24.
At 4 mbar, a 50 μm size particle couples to the gas flow on a timescale of 50 ms. Therefore, in accordance with the observations, they rapidly slow down and then essentially trace the gas flow. A photophoretic motion is superimposed on the particle motion. This is visible when the dust bed is closed again by the lid 1 s before hitting the ground and returning to laboratory gravity. Particle motion by photophoresis can be stronger than the gas flow. Such particles are, for example, seen moving towards the dust bed rapidly within the laser beam. In any case, particles outside the direct light beam are not subject to photophoresis but are visible within the stray light. They move along with the gas and trace the streamlines.
We used three different dust bed samples: black spherical particles (150–250 μm in size), basalt with a broad size distribution up to 125 μm and a mixture of basalt and transparent glass spheres of 150–250 μm size. All basalt samples were heated for 48 h at 200 °C to remove any water. Neither sublimation nor expansion led to an inflow of gas into the dust bed and to a directed convection through free-floating aggregates (also observed but not shown here). Earlier levitation experiments with basalt and other samples showed that gas flow and compression are not tied to water10,25. In fact, the earlier levitation experiments with basalt were carried out on a 500 °C hot surface and we rule out that water plays a role here. Most experiments were carried out with pure basalt but the other samples showed the same gas flow patterns.
Model of dust bed gas flow.
To support the measurements we carried out a numerical calculation according to the experimental setting. For this we simulated a gas flow within the experiments.
The problem was solved using COMSOL to simulate the flow within the dust bed and in the space above. To drive the gas flow, we placed a volume force within which the light beam enters the dust bed and it was adjusted to obtain the measured mass flow rates. Everything else, that is, the convective pattern and the depth of the gas flow, is then determined self-consistently. The simulation is carried out to compare the general circulation to the experiments and to see the part below the surface not accessible by the observations. The simulated flow matches the general flow pattern as well as the measured inflow velocities. The simulations show that gas flow at least down to 1 cm is still larger than 1 mm s−1 but this strongly depends on the spatial extent of the dust bed and illumination. A spatially scaled up version of the simulation shows that also the depth of the gas flow increases. Therefore, gas flow for the illuminated surface of Mars might reach larger depths.
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This project is supported by DLR Space Management with funds provided by the Federal Ministry of Economics and Technology (BMWi) under grant number DLR 50 WM 1242. T.J. and M.K. are supported by the DFG. Access to earlier microgravity experiments on parabolic flights leading to the development of the experiment was granted by DLR and ESA.
The authors declare no competing financial interests.
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de Beule, C., Wurm, G., Kelling, T. et al. The martian soil as a planetary gas pump. Nature Phys 10, 17–20 (2014). https://doi.org/10.1038/nphys2821
Planetary and Space Science (2019)
Planetary and Space Science (2019) | 0.82142 | 4.017977 |
The sun is revealing itself in dramatic detail and shedding light on how other stars may form and behave throughout the universe – all thanks to NASA’s Parker Solar Probe.
NASA's Parker spacecraft is enduring scorching temperatures to gather data, which are being shared for the first time in four new papers that illuminate previously unknown and only-theorised characteristics of our volatile celestial neighbour.
The information Parker has uncovered about how the sun constantly ejects material and energy will help scientists rewrite the models they use to understand and predict the space weather around our planet, and understand the process by which stars are created and evolve.
Thomas Zurbuchen, associate administrator for science at NASA Headquarters in Washington, said, "This first data from Parker reveals our star, the sun, in new and surprising ways."
This information will be vital to protecting astronauts and technology in space – an important part of NASA’s Artemis program, which will send the first woman and the next man to the moon by 2024 and, eventually, on to Mars.
"Observing the sun up close rather than from a much greater distance is giving us an unprecedented view into important solar phenomena and how they affect us on Earth, and gives us new insights relevant to the understanding of active stars across galaxies. It’s just the beginning of an incredibly exciting time for heliophysics with Parker at the vanguard of new discoveries," Zurbuchen added.
Among the findings are new understandings of how the sun's constant outflow of solar wind behaves. Seen near Earth, the solar wind plasma appears to be a relatively uniform flow – one that can interact with our planet's natural magnetic field and cause space weather effects that interfere with technology.
Instead of that flow, near the sun, Parker's observations reveal a dynamic and highly structured system, similar to that of an estuary that serves as a transition zone as a river flows into the ocean.
For the first time, scientists are able to study the solar wind from its source, the sun's corona, similar to how one might observe the stream that serves as the source of a river. This provides a much different perspective as compared with studying the solar wind where its flow impacts Earth.
Nicola Fox, director of the heliophysics division at NASA Headquarters, explained, "The sun is the only star we can examine this closely. Getting data at the source already is revolutionising our understanding of our own star and stars across the universe. Our little spacecraft is soldiering through brutal conditions to send home startling and exciting revelations."
Parker Solar Probe is part of NASA’s Living with a Star program to explore aspects of the sun-Earth system that directly affect life and society.
The Living with a Star program is managed by the agency’s Goddard Space Flight Centre in Greenbelt, Maryland, for NASA’s Science Mission Directorate in Washington. Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built and operates the spacecraft.
Receive the latest developments and updates on Australia’s space industry direct to your inbox. Subscribe today to Space Connect here. | 0.834667 | 3.928388 |
Saturn is the second largest planet and sixth from the sun. Like the other outer planets (Jupiter,Uranus,Neptune) it's a gas giant, meaning it has no solid surface like Earth does.
It is the only planet less dense than water. that means that if you could drop Saturn in a large ocean it would actually float.
Orbiting the sun in about 29.5 Earth years, its days are only about 10.5 hours long. Spinning so fast that it flattens out at the top and bottom near the poles, and bulges in the middle. Most celestial objects do this to some degree, but Saturn and Jupiter have the largest bulges. The planet has a magnetic field, which is 1,000 times as strong as that of Earth.
When stargazing, the planet is visible with the naked eye. Though you won't be able to see the rings or any of the moons. It has an apparent magnitude of 0.43 compared to that of the Moon at -12.74.
When you see it, it will appear as a bright golden star.
With a pair of large aperture binoculars mounted on a tripod you may be able to see the disk and possibly a ring outline but don't expect it.
Telescopes on the other hand can bring the rings into clear view.
Discovered by Galileo Galilei in 1610 using a telescope, he was not able to clearly see the rings and thought that there were“ handles” on its sides.
Seven rings labeled from A-G surround the planet.
The rings are labeled in order of discovery.
They appear in a strange order. Often what was thought to be 1 ring has turned out to be 2 or more as we are better able to see them. From the planet outward they are: D,C,B,A,F,G,E.
Between the B and A rings is the large Cassini Division.
In small scopes of less than 150mm(6in) aperture if conditions are good for viewing you may see the rings and the moon Titan.
Telescopes of 150mm(6in) or larger aperture will reveal quite a lot.
The rings, the Cassini Division , and possibly 7 of the moons.
Look for the gold and brown cloud bands surrounding the planet. You may only be able to distinguish a white-beige region about the equator and the dark polar regions.
At certain times viewing the rings becomes nearly impossible as the planet tilts on its axis and orbits. Sometimes the view from Earth is edge on to the rings and they seem to almost disappear.
Eight of the moons are visible in telescopes.Celestial Solar System › PLANETS › Saturn | 0.87203 | 3.693208 |
Follow a sunset on a clear day against a distant horizon and you might glimpse green just as the Sun disappears from view. The green flash is caused by refraction of light rays traveling to the eye over a long path through the atmosphere. Shorter wavelengths refract more strongly than longer redder wavelengths and the separation of colors lends a green hue to the last visible vestige of the solar disk. It’s harder to see a green flash from the Moon, not to mention the diminutive disks of Venus and Mercury. But a telescope or telephoto lens and camera can help catch this tantalizing result of atmospheric refraction when the celestial bodies are near the horizon. From Sicily, the top panels were recorded on March 18, 2019 for the Sun and May 8, 2020 for the Moon. Also from the Mediterranean island, the bottom panels were shot during the twilight apparition of Venus and Mercury near the western horizon on May 24.
That’s not a bright star and crescent Moon caught between branches of a eucalyptus tree. It’s Venus in a crescent phase and Mercury. Near the western horizon after sunset, the two inner planets closely shared this telescopic field of view on May 22, seen from a balcony in Civitavecchia, Italy. Venus, the very bright celestial beacon, is wandering lower into the evening twilight. It grows larger in apparent size and shows a thinner crescent as it heads toward its inferior conjunction, positioned between Earth and Sun on June 3. Mercury, in a fuller phase, is climbing in the western sky though, reaching its maximum angular distance from the Sun on June 4 Still, this remarkably close pairing with brilliant Venus made Mercury, usually lost in bright twilight skies, easier to spot from planet Earth. Gallery: Notable Venus & Mercury Conjunction 2020 Images submitted to APOD
Still bathed in sunlight, the International Space Station arced through the evening sky over lake Wulfsahl-Gusborn in northern Germany, just after sunset on March 25. The familiar constellation of Orion can be seen left of the trail of the orbital station’s bright passage. On the right, Venus is the brilliant evening star above the western horizon. With the camera fixed to a tripod, this scene was captured in a series of five exposures. How can you tell? The short time delay between the end of one exposure and the beginning of the next leaves small gaps in the ISS light trail. Look closely and you’ll also see that the sky that appears to be above the horizon is actually a reflection though. The final image has been vertically inverted and the night skyscape recorded in the mirror-like waters of the small lake. | 0.871137 | 3.6167 |
On August 12th, a Delta IV Heavy rocket launched NASA's Parker Solar Probe onto a trajectory through the Sun's upper atmosphere, or corona. Over the next seven years, the probe will make 24 orbits around the Sun, using 7 gravity assists from Venus to gradually fly closer and closer to our home star.
Parker Solar Probe is humanity's first spacecraft to directly sample a star. The probe will make its first close approach this November and continue measuring the Sun and its corona for the next six years. Cover image and animation credit NASA.
The Parker Solar Probe is on a mission to touch the Sun. That sounds a little misleading since the Sun is a fiery ball of plasma, but it's true- the probe will be the first to fly through the Sun's upper atmosphere, or corona, and take measurements from within it. A suite of instruments on board will take samples of the energized coronal particles to investigate their energies, quantities, and other properties that can't be directly measured by remote observatories.
For example, the corona reaches temperatures on the order of millions of degrees Fahrenheit, while the surface (the point beneath which the Sun becomes opaque) only heats up to tens of thousands of degrees F. Scientists suspect the reason for this difference of multiple orders of magnitude in temperature has something to do with magnetic interactions in the corona, but it's difficult to theorize mechanics without data on what's happening there. This is where the Parker Solar Probe comes in.
Eugene Parker's Solar Wind
On August 31, 2012 a long filament of solar material that had been hovering in the sun's atmosphere, the corona, erupted out into space at 4:36 p.m. EDT. The coronal mass ejection, or CME, traveled at over 900 miles per second. Credit: NASA/GSFC/SDO
The corona is the Sun's atmosphere that extends more than 18 million miles from the surface. These particles don't just stop, though. The solar wind, as its known, is a stream of particles emanating from the Sun at high energies and continue through interstellar space. This constant stream of magnetized solar material flows outward at 800,000-5,000,000 miles per hour, and can have high energies that are dangerous to life and satellites alike. Huge bursts of particles periodically spew into the solar system all at once through Coronal Mass Ejections (CMEs) and can cause all kinds of damage to satellites, electronics, and organisms here on Earth.
Coronal Mass Ejections are explosions of energized particles from the Sun. To learn more about CMEs and solar observatories in space, listen to our interview with Terry Kucera about her work with STEREO, a pair of solar observatories that study these mechanisms of the Sun.
The Sun's corona has puzzled physicists and astronomers with every solar eclipse for more than 150 years. Through the early 20th century, observations of magnetic field activity on Earth and studies of the Sun led physicists to postulate that electrons and positive ions were emanating from the Sun. Later in the 1930s, astronomers estimated the corona's temperature to be millions of degrees, which we have now confirmed to be true. In the 1950s, studies of comets pointed out that comet tails always point away from the Sun.
The science history of studying the Sun's corona is fascinating. It's full of mystery, twists, turns, and a healthy dose of physics. Read NASA's article for the whole story.
It wasn't until 1958 that Eugene Parker put the pieces of this puzzle together. But when Parker, the probe's namesake, proposed his theory that the heat flowing from the Sun, energized particles, and comet tails were the result of the same phenomenon, his idea for the "solar wind" was largely dismissed by the scientific community. He was finally proven correct when Mariner II, the first successful interplanetary mission, collected data on its way to Venus.
Now 60 years later, the Parker Solar Probe (PSP) will investigate the mechanisms that create Parker's solar wind. By taking measurements from within, scientists hope to gain a better understanding of the fundamental processes of solar weather, and perhaps discover new electromagnetic dynamics at work. Moreover, these processes inform our concepts of what happens inside all stars, and the Sun is the only star we can study up close.
Today we have a large body of observational data on the corona, but it has all been collected from a safe distance, around 93 million miles away. Parker Solar Probe will get up close and personal, making high speed passes straight through the hot corona.
Parker Solar Probe will inch its way closer to the Sun over its 24 orbits and seven year mission life. By NASA, via Wikimedia Commons.
Parker Solar Probe will make seven close passes with Venus during it's seven year mission life, using the planet's gravitational pull to slow it down. With each pass, the probe's perihelion (closest approach to the Sun) gets closer and closer to the solar surface. The probe will fly within 15.4 million miles of the Sun the first time by this November, a little over half the distance between our star and Mercury. By 2024 Parker's perihelion will drop to a little over 4.26 million miles, where it will continue to orbit the Sun for the rest of its life.
NASA Goddard has released a whole slew of mesmerizing animations for each phase of the mission. Watch them here.
NASA says Parker Solar Probe will touch the sun, but I like to think that the Parker Solar Probe is tasting the Sun, too. It's using all five senses in fact--hearing (FIELDS), sight (WISPR), Taste (SWEAP, low sensitivity composition), Smell (IS☉IS, high sensitivity composition), and Touch (the spacecraft feels the heat!).
Hearing: Fields Experiment (FIELDS) - Space Sciences Lab at UC Berkeley
FIELDS uses a suite of electromagnetic sensors to measure waves and turbulence in the solar wind. Image credit NASA/APL.
WHAT: Measures waves and turbulence in the inner heliosphere with high temporal resolution.
HOW: Four electric field antennas are mounted near the edge of the heat shield. A voltage sensor, two fluxgate magnetometers, and a search coil magnetometer are mounted on the magnetometer boom. The fluxgate magnetometers are specialized for measuring large-scale features further away from the sun, while the search coil magnetometer samples with high time resolution (2MHz) when the probe is closest to the Sun.
WHY: The corona, like any atmosphere, is a fluid. We usually think there's no sound in space, but that's not entirely true. There's no sound in a vacuum, but inside the corona sound, or pressure waves are able to propagate. Since the corona is composed of charged particles, it is heavily influenced by the Sun's magnetic field, which can accelerate the fluid to supersonic speeds. FIELDS aims to understand how pressure waves, shocks from supersonic flow and the electromagnetic fields that lead to the stunning coronal loops that form as solar plasma follows the contours of the Sun's magnetic field.
Sight: Wide Field Imager for Parker Solar PRobe (WISPR) - Solar and Heliophysics Branch at Naval Research Lab
WISPR is the only imaging instrument on the spacecraft. Its data will be used to map 3D coronal structures that other instruments will sample as the probe passes through them. NASA Goddard has some excellent visualizations to better understand how it works. Image credit NASA/APL.
WHAT: Images large scale coronal features before probe passes through them to derive the 3D structure of the solar corona.
HOW: Radiation-hardened 2k-by-2k pixel CMOS imaging sensors are placed behind two nested telescopes.
WHY: Having images from the craft itself helps correlate large scale coronal structure to detailed in-situ measurements from other instruments. While other observatories on Earth or in orbit are capable of observing the Sun, WISPR will image the solar wind, shocks and other structures in the corona and inner heliosphere as they approach and pass the spacecraft.
Taste: Solar Wind Electrons Alphas and Photons Investigation (SWEAP) Investigation - Smithsonian Astrophysical Observatory, Space Sciences Lab at UC Berkeley
The Solar Probe Analyzers (SPAN) are placed in the shade of the heat shield and are rotated such that their combined field of view covers the entire sky except what is obscured by the heat shield. The Solar Probe Cup (SPC) is exposed to view the sun directly. Image credit Kasper, J.C., Abiad, R., Austin, G. et al.
WHAT: Counts electrons, protons, and helium ions in the solar wind and measures their velocity, density and temperature.
HOW: SWEAP consists of a suite of instruments. The Solar Probe Cup (SPC) is a Faraday cup that is exposed directly to the Sun and measures ion and electron fluxes and flow angles as a function of energy. The Solar Probe Analyzers (SPAN) are electron electrostatic analyzers that sort collected particles based on mass and charge ratios to identify different ion species.
WHY: SWEAP will produce velocity distributions with high energy and angular resolutions, enabling observations of coronal structures such as shocks and reconnection events.
Smell: Integrated Science Investigation of the Sun (IS☉IS) - Johns Hopkins Applied Physics Lab, Caltech, SwRI, NASA Goddard
The 83 telescopes between EPI-Lo and EPI-Hi collimate energetic particles into narrow pathways, which allows their speed and energy to be measured while also registering which aperture they passed through. Image credit McComas, D.J., Alexander, N., Angold, N. et al..
WHAT: Measures electrons, protons and ions over a range of energies across a wide field of view.
HOW: Two Energetic Particle Instruments (EPIs) measure the energy and species of ions and electrons across a wide range of energies. EPI-Lo measures low energy particles using 80 tiny telescope apertures that have a combined field of view of almost a complete hemisphere. EPI-Hi measures high energy particles using a combination of three telescopes that together make five large field of view apertures. IS☉IS resides at the back of the spacecraft, shielded from direct sunlight.
WHY: By observing a large field of view, IS☉IS will provide insights to where these energetic particles originate, how shocks and turbulence affect accelerations of these particles, and how the electrons and ions propagate from the corona.
Touch: Solar Panels and Thermal Management
One obvious question to consider with this mission is "why won't Parker Solar Probe melt?" The answer is simpler than you might think.
Temperature is a metric to explain how much energy is in something. Heat is the metric to explain how that energy is transferred, and this is the what worries spacecraft engineers. Although the corona can reach temperatures of several millions of degrees, its density is very low so a small fraction of the heat is transferred to the probe. The surface of Parker Solar Probe's heat shield on closest approach will reach 2500F, which is cooler than 5 million but still hotter than lava, which only gets up to 2200F.
It is still a major challenge to keep the instruments and other spacecraft components at temperatures where they are happy (~85F). To accomplish this, PSP uses a heat shield called the Thermal Protection System (TPS) to shade the rest of the spacecraft. The heat shield is a carbon plate-carbon composite foam-carbon plate sandwich coated in white ceramic paint. The white paint does some of the work by reflecting as much of the heat as possible, reducing the amount of heat that is absorbed and transmitted through the TPS. The carbon composite sandwich is made of regular carbon fiber plates on either end, filled by 4.5 inches of carbon composite foam. The foam core is 97% hollow, which greatly increases its thermal resistance and has a side benefit of being very light. The 8 ft diameter TPS only weighs 160 lbs.
The angle of the small solar array "tabs" on the end is autonomously controlled by the spacecraft to optimize power and cooling capacity. According to Mary Kae Lockwood, a spacecraft system engineer for Parker Solar Probe from APL, a one degree change in the array angle of one wing would require 35 percent more cooling capacity. Image credit NASA/APL.
As one might expect, the Parker Solar Probe is powered by solar arrays. An interesting problem arises because of this: solar panels are designed to harvest energy by absorbing light (and therefore heat). But, as always, NASA engineers have this one figured out.
The spacecraft's solar panels retract into the shade of the heat shield on close approach, leaving all but a little tab of the arrays exposed to the Sun, but the solar panels still absorb a lot of heat. To keep temperatures manageable, the arrays are water-cooled as well. About a gallon of water is piped across the back side of the panels then the heat is rejected with two radiators. The water tank is heated to keep it from freezing, and pressurized to raise the boiling point up by about 25%. At nominal capacity, the cooling system is able to reject 6,000W of heat.
Getting the science back to Earth
Once Parker Solar Probe collects all this data, it has to get it back to Earth. The communications system has two functions--transmitting science data, and speaking to mission controllers (receiving commands and sending health updates or telemetry). All communication between ground stations and the spacecraft will be managed by NASA's Deep Space Network.
After making a close pass with the Sun, the probe will send home the measurement data using a 0.6 meter high gain antenna mounted to the body of the spacecraft. During the science downlink period, high rate transmissions will send science data daily for 10-24 hours per day until all data is sent.
The probe will keep ground control informed of the spacecraft's status with less frequent downlinks of real-time health and telemetry data sent from two fan-beam antennas or a two low gain antennas in contingency situations. During the cruise phase of its orbit, these downlinks will occur three times per week. During a solar encounter phase, the probe will send out a beacon tone three time per week indicating health and status (but not full telemetry).
Vourlidas, A., Howard, R.A., Plunkett, S.P. et al. "The Wide-Field Imager for Solar Probe Plus (WISPR)" Space Science Reviews (2016) 204: 83. ↩︎
Kasper, J.C., Abiad, R., Austin, G. et al. "Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus," Space Science Reviews (2016) 204: 131. ↩︎
McComas, D.J., Alexander, N., Angold, N. et al. "Integrated Science Investigation of the Sun (ISIS): Design of the Energetic Particle Investigation," Space Science Reviews (2016) 204: 187. ↩︎ | 0.810368 | 3.971564 |
NASA’s OSIRIS-REx is getting closer, physically and temporally, to its primary goal. The spacecraft arrived at Bennu at the end of 2018, and for just over a year it’s been studying the asteroid, searching for a suitable sampling site.
To do that, it’s getting closer and closer.
OSIRIS-REx stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer. The heart of the mission is the sample it’ll collect from asteroid Bennu. That sample will eventually make its way back to Earth for study.
The OSIRIS-REx team selected a sampling site very carefully. When the spacecraft arrived at asteroid Bennu, NASA found that the surface of the asteroid was more challenging than they thought. Though the surface contains an abundance of the right sized material for the spacecraft’s sampling mechanism, there are plenty of hazards to be avoided.
Eventually, the OSIRIS-REx team came up with a list of four potential sampling sites. They then did more fly-overs of the four, to take an even closer look.
From there, they chose two sampling sites: a primary site and a secondary site. All four of the sites received avian-themed names, and at the end of the process, NASA chose Nightingale as the primary site, and Osprey as the backup site.
Throughout the site selection process, OSIRIS-REx reconned Bennu in three phases: Recon A, B, and C. During each phase, it got progressively closer to the surface, gathering more detail on each site.
Now, in recon phase C, the spacecraft has performed its closest flyover yet. On March 3rd, it flew over Nightingale at an altitude of only 250 meters (820 ft).
The spacecraft’s safe-orbit height is one km (0.6 miles), but for about five hours, OSIRIS-REx left that safety behind. The Nightingale site is in a crater, and it’s about 16 meters (52 feet) wide. During the maneuver, all of the science instruments were aimed at the sampling site.
While all of the science instruments were operating, this flyover is mostly about the spacecraft’s PolyCam imager. PolyCam is a 20.3-cm (8-inch) telescope, and the closer it gets to Bennu, the higher resolution images it acquires.
After the flyover OSIRIS-REx returned to its safe home orbit, but in the opposite direction. Now it’s ready for its next big maneuver, the sampling rehearsal.
There’ll be two sampling rehearsals, and the first one is scheduled for April 15. The spacecraft will make its closest approach then, coming to within 125 meters (410 feet) of Bennu’s surface. But it’s not done there.
At that altitude it’ll perform what’s called the Checkpoint maneuver. It’ll descend even closer to the Nightingale site, and after descending for about 10 minutes, it’ll stop its descent at 50 meters (164 feet) and begin backing away from the asteroid.
Then in June OSIRIS-REx will perform its second rehearsal. But this time, it’ll get just a little closer, to between 25 to 40 meters (82 to 131 feet) before backing away.
As OSIRIS-REx performs each approach, it’ll be gathering more data on the sampling site. It’ll also be “training” its Natural Feature Tracking (NFT) system. The NFT uses images of Bennu’s surface to guide itself, comparing onboard images with real-time camera input to avoid hazards and nail its sampling operation.
The actual sampling maneuver is scheduled for late August 2020. At that time, OSIRIS-REx will come close enough that its sampling mechanism touches the surface. Then it’ll fire a charge of nitrogen gas to kick-up some regolith, and capture some of it. Then it’ll back away.
Mission operators won’t be surprised if the spacecraft’s NFT system cancels the sampling attempt. The system has a built-in fail-safe. OSIRIS-REx can perform multiple sampling attempts, so there’s no need to commit to a maneuver that is deemed unsafe by the spacecraft’s automated systems.
If the first attempt at Nightingale doesn’t work, OSIRIS-REx can either try and collect from Nightingale again, or move to the backup site, Osprey.
Eventually, if all goes well, OSIRIS-REx will return to Earth and release the Sample Return Capsule (SRC) into Earth’s atmosphere, where it will deploy a parachute and float down to the surface. It’s expected to land at the Utah Testing and Training Range, where it will be retrieved. | 0.821916 | 3.639852 |
This story was updated at 6:15 pm ET.
A new Japanese space probe is poised to launch toward Venus tohelp solve the enduring mysteries of the hellish, cloud-covered world, whichhas been often described as Earth's twin. But the ambitious spacecraft willhave to wait for better weather on Earth.
The Venus Climate Orbiter Akatsuki, which means "Dawn" inJapanese, was slated to launch from Tanegashima Space Center in Japan today ona 2-year mission to study the weather and surface of Venusin unprecedented detail. But low clouds and foul weather prevented its plannedliftoff at 5:44 p.m. EDT today, though it was early Tuesday morning local timeat the launch site. A new launch target was not immediately available.
"Oncewe can explain the structure of Venus, we will be able to better understandEarth," said Akatsuki project scientist Takeshi Imamura in a statementreleased by the Japan Aerospace Exploration Agency (JAXA). "For example,we may discover the reasons that only Earth has been able to sustain oceans,and why only Earth is abundant in life."
Imamurahas called Akatsuki"the world's first interplanetary probe that deserves to be called ameteorological satellite."
The probe carries five different cameras to study Venus' clouds aswell as map the planet's weather and peer through its thick atmosphere to viewthe surface. It will join Europe's Venus Express already in orbit around theplanet, and has scientists on that mission eager as well.
"Venus somehow transformed from a more Earth-like place tothe alien place it is today, and what's fascinating about the world is figuringout how it diverges from the Earth and the history behind why thathappened," said David Grinspoon, curator of astrobiology at the DenverMuseum of Nature and Science and an interdisciplinary scientist on the VenusExpress mission. "It could help us understand how things here mightchange."
Akatsuki will launch atop a Japanese H-2A rocket and won't bealone during blastoff. JAXA is launching several smaller satellite experimentswith the mission, including an ambitious solar sail designed to tag along onthe trip to Venus. [More on Japan'ssolar sail mission.]
Secretof Venus' super-rotation
Oneof Akatsuki's main goals is to understand what may be the biggest mystery ofVenus — the "super-rotation" of its atmosphere, where violent windsdrive storms and clouds around that planet at speeds of more than 220 mph (360kph), some 60 times faster than the planet itself rotates.
"There's no consistent model of Venus's climate that canreproduce this super-rotation," Grinspoon explained. "We've beentaking general circulation models from Earth and tweaking them for Venus, andthey don't work. By understanding better how climate works on Venus, it willmake us better understand how climate change on Earth works."
Akatsukiwill monitor Venus in the infrared to learn more about the atmosphere andsurface under the murky clouds, hopefully revealing what mechanism is drivingthis super-rotation.
ButImamura has said his team is fully prepared to be surprised by unexpectedfindings which may uncover more questions than answers.
"Wemay be pleasantly surprised by the emergence of a greater mystery than super-rotation,"he said.
The Venus Express spacecraft the European Space Agency launched in2005 intriguingly found evidence of lightningon the planet, even though none should exist.
"What creates lightning on Earth is water droplets and icecrystals in clouds, which leads to the separation of electric charges thatlightning needs, and you don't have that kind of weather on Venus,"Grinspoon said.
But Venus is covered with thick clouds of sulfuric acid.
"Maybethere's a kind of weather we haven't seen yet on Venus that causes thislightning, or maybe how we're wrong about the kinds of conditions needed tomake lightning," he added.
Akatsukishould help capture vital clues about this lightning with a camera dedicated tophotographing it.
Weirdstripes on Venus
Thereare unusual stripes in the upper clouds of Venus dubbed "blueabsorbers" because they strongly absorb light in the blue and ultraviolet wavelengths.These are soaking up a huge amount of energy — nearly half of the total solarenergy the planet absorbs. As such, they seem to play a major role in keepingVenus as hellish as it is, with surface temperatures of more than 860 degrees F(460 degrees C).
"We don't know what they are," Grinspoon said."They're probably some kind of sulfur compound, but we haven't been ableto nail it down yet."
Akatsuki's ultraviolet imager will focus on inspecting theseenigmas.
A bright mystery, and volcanoes?
In2007, two-thirds of the Venus?s southern hemisphere was suddenly covered in abright haze that disappeared a few days later. It remains uncertain whatstarted this amazing transformation.
"Wethink it's some kind of dynamic overturning of the atmosphere that injectedsulfur dioxide above the clouds briefly, but we're not sure," Grinspoonsaid.
The clouds may be fueled from sulfur spewed up by volcanoeson Venus, as Grinspoon and his colleagues ran calculations that suggest thesulfur seen in the atmosphere should dissipate after 10 to 30 million years ifnot otherwise refueled. However, Venus's clouds are so thick that no one hasactually seen any volcanoes yet.
"Venus guards her secrets rather tightly, and underforbidding conditions," he said. The scientists behind Akatsuki hope itscameras might be able to spot active volcanoes under her veil.
When Akatsuki reaches Venus in December, it will find VenusExpress there as a partner in orbit, complementing it in a number of ways.
For instance, they will take different orbits over the planet —while Venus Express has an orbit that takes it over both poles, enabling it tosee virtually the entire world, Akatsuki will fly an elliptical orbitaround the equator, allowing it to concentrate on parts of the atmosphere forhours at a time. The orbit will bring Akatsuki as close as 186 miles (300 km)to Venus and as far away as 49,709 miles (80,000 km).
"VenusExpress and Akatsuki are like sister satellites, and a very good cooperativerelationship has been built as we have progressed in our missions,"Imamura said.
Imamura said that while Venus Express primarily studies thechemical composition of Venus' atmosphere, Akatsuki will focus on the fluidmotion of the planet's weather. Together, the two spacecraft should reveal acomprehensive picture of how the planet works.
"If there's one thing we've been learning about Venus, it'sthat it's a really dynamic planet that's very changeable, so we need as muchlong-term data as we can to build up an understanding of how things change overtime," Grinspoon said. "Having Akatsuki there should help capturemore vital clues to understanding Venus's mysteries."
- Gallery - Beneath the Clouds of Venus
- Top 10 Extreme Planet Facts
- Japanese Solar Sail Headed for Venus and Beyond | 0.820138 | 3.134133 |
Red and glowing
This little pellet can power a spacecraft. Another hint: It's somewhat related to the stuff involved in the Chernobyl nuclear disaster, 25 years ago today.
That should be enough clues for an approximate guess. So …
The image shows a pellet of plutonium used to power the radioisotope thermoelectric generator (RTG) in either the Cassini mission to Saturn or the Galileo mission to Jupiter (we're not told which — top secret stuff, perhaps). Plutonium was also used to power equipment during Apollo moon landings.
The pellet glows red hot because of radioactive decay, which means energy is released in the form of ionizing particles. In a spacecraft, plutonium-238 — what you see above — is at the heart of a long-lived nuclear battery that converts heat from the decay into electricity to power the spacecraft instruments.
Another tricky one.
Look closely and make your guess before reading on …
It's a giant jellyfish unlike most you might ever have seen. Instead of long tentacles, this creature has fleshy arms that capture food. See the full image below.
This jelly can be as big as a washing machine. See on the next slide.
This giant red-hued jellyfish called Tiburonia granrojo was described by American and Japanese researchers in 2003. It grows up to 3.3 feet (1 meter) in diameter and lives at depths of 2,000 to 4,800 feet (650 to 1,500 meters) in the ocean. First seen during submarine dives in 1993, the jellyfish is distinct in that it uses four to seven fleshy arms to capture food, rather than fine tentacles like other jellyfish.
Yes it slithers …
It slithers …
If you didn't figure out it's the skin of a snake, go ahead and smack yourself on the forehead now (and be careful if you go out in the woods).
You get two points if you guessed "rattlesnake." Check out the full image, with rattle, on the next slide.
To create that spine-chilling noise, a rattlesnake's rattle moves back and forth about 60 times a second. The rattle's segments are formed more than once a year, each time the snake sheds its skin. And they sometimes break off. So it's a myth that you can tell a rattlesnake's age by the number of segments in its rattle.
If you're one who feels that chill just at the thought of snakes, you're not alone. Many people fear snakes, and scientists think humans may have evolved an innate tendency to sense snakes — and spiders — and to learn to fear them, because in fact they can be dangerous.
Did you know rattlesnakes can survive months without food, and they'll even grow while starving?
This might have looked like alien etchings, or maybe cave art, and to some it might tickle a memory that just can't be pinned down. You can see the full image on the next slide.
First, a hint … here's what Carl Sagan said about the subject of this image: "The spacecraft will be encountered and the record played only if there are advanced spacefaring civilizations in interstellar space. But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet."
It is the lower-left portion of what's known as the Golden Record, one of the two phonograph records aboard NASA's Voyager 1 and Voyager 2 spacecraft. In fact, after 35 years Voyager 1 left the solar system in August 2012, researchers reported, taking its first steps in interstellar space. Each gold-plated copper disk holds images and sounds portraying the life and culture on Earth, plus music new and old from around the world.
The visible inscriptions on the record serve as a welcome and a guide. The etching that served as the teaser (in the lower left of the record) shows the location of our solar system with respect to 14 stars known as pulsars, and the period of rapid rotation of those stars is noted, to help aliens identify them. In the upper left of the record is a drawing of the record and the stylus carried with it, with instructions on how to play it.
This is a fun one. If you need a hint, try this: You're seeing just the top of something, and a full-size person is standing within it.
Hint No. 2: It's 2 million years old. See the full image on the next slide.
It's billed as the world's largest shark jaw, measuring 9 feet (2.7 meters) tall and 11 feet (3.4 m) across. The giant jaw is made from 182 fossilized from the extinct Carcharocles megalodon. Vito Bertucci, a jeweler-turned-fossil hunter, is behind the project. | 0.866358 | 3.458251 |
From: Goddard Space Flight Center
Posted: Monday, September 19, 2005
Comet Tempel-1 may have been born in the region of the solar system occupied by Uranus and Neptune today, according to one possibility from an analysis of the comet's debris blasted into space by NASA's Deep Impact mission. If correct, the observation supports a wild scenario for the solar system's youth, where the planets Uranus and Neptune may have traded places and scattered comets to deep space.
"Our observation is a definitive investigation revealing the composition of comet Tempel-1," said Dr. Michael Mumma of NASA's Goddard Space Flight Center, Greenbelt, Md. Mumma and his team used the powerful Keck telescope on top of Mauna Kea, Hawaii, to analyze in great detail light emitted by Tempel-1 gas ejected by the impact. Because each type of atom and molecule emits light at unique colors (frequencies), the team was able to determine the comet's chemical composition by separating its light into its component colors with an instrument called a spectrometer. Mumma is lead author of a paper on this research that appeared in Science on September 15.
Comets are chunks of ice and dust that zoom around the solar system in elongated orbits. This "dirty snowball" is the nucleus of the comet. Comet nuclei are thought to be cosmic leftovers, condensed remains of the gas and dust cloud that formed the solar system. As a comet gets close to the sun, solar heat liberates gas and dust from the nucleus, forming the coma, which is an extensive, bright cloud around the nucleus, and one or more tails.
Repeated solar heating can remove materials that have low freezing temperatures from the surface, giving the comet a crust that's different chemically from its interior. This makes it hard to discover a comet's true composition by simply looking at gas that's evaporating from the surface. NASA's Deep Impact mission crashed into comet Tempel-1 July 4, 2005, allowing scientists to test whether material ejected from its protected interior was closer to pristine.
By observing Tempel-1 before, during, and after impact, the team was able to distinguish surface gas from the impact debris, and they discovered that the interior does indeed have a different chemistry. "The amount of ethane (C2H6) in the cloud around the comet was significantly higher after impact than before," said Mumma.
There are two possible explanations for this. In the first, the surface crust is different from the interior due to solar heating. The interior, however, is all the same. In the second, the interior is a mix of regions with different compositions because the nucleus is actually composed of smaller "mini-comets" (cometesimals), each with a different chemistry. Deep Impact could have just so happened to hit one of these cometesimals, while the gas seen before impact might have came from a different region on the comet with different chemistry. Multiple impacts in different regions of the comet are necessary to determine which scenario is correct, according to the team.
If the first scenario is correct, the comet could have formed in the region now bounded by the orbits of Uranus and Neptune, based on its interior chemistry. Different chemicals get frozen into a comet depending on its location. A comet that forms farther from the sun will have greater amounts of ices with low freezing temperatures, like ethane, than a comet that forms closer to the sun. By measuring the relative amounts of each chemical, astronomers can estimate where a comet formed.
Formation in this location supports a theory that the gas giant planets Uranus and Neptune formed closer to the sun than their current locations. The theory, proposed by Dr. Alessandro Morbidelli of the Observatoire de la Cote d'Azur, Nice, France, and his team, says that gravitational interaction between the gas giant planets and numerous small planets left over from the solar system's formation (planetesimals) brought the giant planets into an unstable orbital configuration. Neptune and Uranus were tossed outward and could have exchanged orbits. As they migrated outward, their gravity disrupted a large disk of comets that had formed in the region where Uranus and Neptune currently reside. Some were scattered into deep space, to a roughly spherical region called the "Oort cloud" that surrounds our solar system at about 10,000 times the earth-sun distance. Others were directed to the Kuiper belt, a region beyond Neptune that extends to several hundred times the Earth-sun distance.
If some Kuiper belt comets have similar chemistry to some Oort cloud comets, it would support this model of the solar system's rowdy early days by showing that certain comets had a common origin despite very different final destinations. Tempel-1 shares certain orbital characteristics with the "ecliptic" comets, a group that likely comes from the "scattered" Kuiper belt. "The amount of ethane in Tempel-1, however, is similar to the amount in the dominant group of comets that come from the Oort cloud region," said Mumma. Its chemical similarity to Oort cloud comets supports the idea that some Kuiper belt and Oort cloud comets formed in the same place. This research was funded by NASA, the National Science Foundation and the National Research Council. For an image, please visit:
// end // | 0.85527 | 3.95388 |
The Kepler spacecraft is scheduled to spend 3-1/2 years looking at more than 100,000 stars similar to our sun, seeking evidence of planets similar in size and composition to Earth.
Kepler is scheduled to blast off from Cape Canaveral Air Force Station in Florida aboard a Delta II rocket on March 5, the US space agency said. Colorado-based Ball Aerospace and Technologies, a subsidiary of Ball Corp, built it.
People long have pondered whether life exists elsewhere in the universe or whether Earth alone hosts living beings.
"Kepler will push back the boundaries of the unknown in our patch of the Milky Way galaxy. And its discoveries may fundamentally alter humanity's view of itself," Jon Morse, director of Nasa's astrophysics division, told reporters.
About 300 planets orbiting stars other than our sun have been discovered since 1995, but most are large gas planets that are not likely to be hospitable to life.
This mission is intended to find rocky planets orbiting in the "habitable zone" around a star where they are not so close as to be scorched and not so far away as to be frozen.
"What we're interested in finding are planets that are not too hot and not to cold, but just right," said William Borucki of Nasa's Ames Research Center at Moffett Field in California.
"We're looking for planets where the temperature is just about right for liquid water on the surface of the planet. And that's the area we think might be conducive to life," he said.
Water is considered an essential ingredient for life.
Borucki estimated the Kepler spacecraft may detect perhaps 50 such planets, but nothing is guaranteed.
"If we find that many, it certainly will mean that life may well be common throughout our galaxy – that there is an opportunity for life to have a place to evolve," he said.
If none or only a few of these planets are found, it might suggest that habitable planets like Earth are very rare and Earth may be a lonely outpost for life, Borucki added.
"They may be water worlds without plate tectonics that force the land mass up above the ocean. These could be worlds that in fact have life like our oceans, but perhaps not sending radio signals to us," said planet hunter Debra Fischer of San Francisco State University in California.
Some star systems are oriented in a manner in which planets in orbit cross in front of the stars, as seen from the vantage point of Earth. The Kepler telescope, with the largest camera ever launched into space, is designed to detect the dimming of these faraway stars as planets pass in front of them.
The spacecraft is named for Johannes Kepler, the German astronomer who lived from 1571 to 1630 and studied planetary motion. Nasa said the mission will cost $591 million (Dh2.2 billion).
Follow Emirates 24|7 on Google News. | 0.876957 | 3.372156 |
Ozone is likely to be depleted more rapidly than ever in the next few
years, say two researchers in the US. From past observations of ozone concentrations
in the atmosphere, they calculate that ozone is depleted fastest when the
Sun is least active and more slowly when it is most active – and the Sun’s
activity is now declining.
This is not the first time it has been suggested that solar activity
might influence the loss of ozone above Antarctica. But previous suggestions
were based on theories of the way in which particles from the Sun influence
the chemistry of the upper atmosphere. The particles should stimulate reactions
that favour the production of ozone.
Now Lon Hood and John McCormack from the Lunar and Planetary Laboratory
of the University of Arizona have carried out a mathematical analysis based
on a statistical study of the measured changes in ozone concentration since
1979. They used data from the Total Ozone Mapping Spectrometer (TOMS)
on the satellite Nimbus 7.
According to Hood and McCormack, the two-yearly variation in ozone depletion
is correlated with a well-known climatic variation called the quasibiennial
oscillation. But when this effect is allowed for, the worsening depletion
of Antarctic ozone in the months from September to October (that is, the
amount by which the depletion gets worse in succeeding years) has slowed
in the past few years. This is depite the fact that ozone depletion has
got worse from year to year during the 1980s (Geophysical Research Letters,
vol 19, p 2309). The Sun’s activity rose to a maximum in the early 1990s.
The Sun’s cycle of activity is about 11 years long from peak to peak.
During this period, there are marked changes in the number of sunspots on
the surface and in other magnetic phenomena. The Arizona team compared ozone
variations with the changing level of solar activity as measured by radio
emission at a wavelength of 10.7 centimetres. They find that this in turn
is correlated with sunspot numbers – the conventional indicator of solar
Sunspot numbers are now decreasing, and will continue to do so until
about 1997. Hood and McCormack conclude that ‘in its present form, the model
predicts that a return to more rapid depletions should occur during the
next four years as solar minimum is approached’, although they caution that
there may be a saturation effect because virtually all of the ozone at
certain altitudes already disappears in the southern spring. | 0.804715 | 3.679504 |
Caltech-Led Astronomers Discover Galaxies Near Cosmic Dawn
Researchers conduct first census of the most primitive and distant galaxies seen
THE HUBBLE ULTRA DEEP FIELD 2012
Credit: NASA/ESA/Caltech-R. Ellis/UDF2012 Team
PASADENA, Calif.—A team of astronomers led by the California Institute of Technology (Caltech) has used NASA's
Hubble Space Telescope to discover seven of the most primitive and distant galaxies ever seen.
One of the galaxies, the astronomers say, might be the all-time record holder—the galaxy as observed existed when the universe
was merely 380 million years old. All of the newly discovered galaxies formed more than 13 billion years ago, when the universe
was just about 4 percent of its present age, a period astronomers call the "cosmic dawn," when the first galaxies were born.
The universe is now 13.7 billion years old.
The new observations span a period between 350 million and 600 million years after the Big Bang and represent the first reliable
census of galaxies at such an early time in cosmic history, the team says. The astronomers found that the number of galaxies
steadily increased as time went on, supporting the idea that the first galaxies didn't form in a sudden burst but gradually
assembled their stars.
Because it takes light billions of years to travel such vast distances, astronomical images show how the universe looked during
the period, billions of years ago, when that light first embarked on its journey. The farther away astronomers peer into space,
the further back in time they are looking.
In the new study, which was recently accepted for publication in the Astrophysical Journal Letters, the team has explored the
deepest reaches of the cosmos—and therefore the most distant past—that has ever been studied with Hubble.
"We've made the longest exposure that Hubble has ever taken, capturing some of the faintest and most distant galaxies,"
says Richard Ellis, the Steele Family Professor of Astronomy at Caltech and the first author of the paper. "The added depth
and our carefully designed observing strategy have been the key features of our campaign to reliably probe this early period
of cosmic history."
THE COLORED SQUARES IN THE MAIN IMAGE OUTLINE THE LOCATIONS OF THE NEWLY DISCOVERED GALAXIES.
ENLARGED VIEWS OF EACH GALAXY ARE SHOWN IN THE BLACK-AND-WHITE IMAGES. EACH GALAXY IS LABELED WITH THE REDSHIFT (Z),
WHICH MEASURES HOW MUCH A GALAXY'S LIGHT HAS BEEN STRETCHED BY THE UNIVERSE'S EXPANSION. THE GALAXY OBSERVED AT A REDSHIFT
OF 11.9 MAY BE THE DISTANCE-RECORD BREAKER, SEEN AS IT APPEARED 380 MILLION YEARS AFTER THE BIG BANG.
Credit: NASA/ESA/Caltech-R. Ellis/UDF2012 Team
The results are the first from a new Hubble survey that focused on a small patch of sky known as the
Hubble Ultra Deep Field (HUDF), which was first studied nine years ago. The astronomers used Hubble's Wide Field Camera 3 (WFC3)
to observe the HUDF in near-infrared light over a period of six weeks during August and September 2012.
To determine the distances to these galaxies, the team measured their colors using four filters that allow Hubble to capture
near-infrared light at specific wavelengths. "We employed a filter that has not been used in deep imaging before, and undertook
much deeper exposures in some filters than in earlier work, in order to convincingly reject the possibility that some of our
galaxies might be foreground objects," says team member James Dunlop of the Institute for Astronomy at the University of Edinburgh.
The carefully chosen filters allowed the astronomers to measure the light that was absorbed by neutral hydrogen, which filled the
universe beginning about 400,000 years after the Big Bang. Stars and galaxies started to form roughly 200 million years after the
Big Bang. As they did, they bathed the cosmos with ultraviolet light, which ionized the neutral hydrogen by stripping an electron
from each hydrogen atom. This so-called "epoch of reionization" lasted until the universe was about a billion years old.
If everything in the universe were stationary, astronomers would see that only a specific wavelength of light was absorbed by
neutral hydrogen. But the universe is expanding, and this stretches the wavelengths of light coming from galaxies. The amount
that the light is stretched—called the redshift—depends on distance: the farther away a galaxy is, the greater the redshift.
As a result of this cosmic expansion, astronomers observe that the absorption of light by neutral hydrogen occurs at longer
wavelengths for more distant galaxies. The filters enabled the researchers to determine at which wavelength the light was absorbed;
this revealed the distance to the galaxy—and therefore the period in cosmic history when it is being formed. Using this technique
to penetrate further and further back in time, the team found a steadily decreasing number of galaxies.
"Our data confirms that reionization is a drawn-out process occurring over several hundred million years with galaxies slowly
building up their stars and chemical elements," says coauthor Brant Robertson of the University of Arizona in Tucson.
"There wasn't a single dramatic moment when galaxies formed; it's a gradual process."
THIS TIMELINE SHOWS THE EVOLUTION OF THE UNIVERSE SINCE THE BIG BANG. THE NEW OBSERVATIONS, LABELED "HUBBLE 2012,"
EXPLORED THE DEEPEST REACHES OF THE COSMOS THAT HAS EVER BEEN STUDIED WITH HUBBLE, GOING BACK ABOUT 13.4 BILLION YEARS.
PREVIOUSLY, THE UNIVERSE WAS IN THE SO-CALLED DARK AGES, BEFORE THERE WERE ANY STARS TO LIGHT UP THE COSMOS. THE DASHED
LINE LABELED HUBBLE 2009 REPRESENTS THE LAST SET OF OBSERVATIONS OF HUDF. (FULL IMAGE)
The new observations—which pushed Hubble to its technical limits—hint at what is to come with next-generation infrared
space telescopes, the researchers say. To probe even further back in time to see ever more primitive galaxies, astronomers
will need to observe in wavelengths longer than those that can be detected by Hubble. That's because cosmic expansion has stretched
the light from the most distant galaxies so much that they glow predominantly in the infrared. The upcoming James Webb
Space Telescope, slated for launch in a few years, will target those galaxies.
"Although we may have reached back as far as Hubble will see, Hubble has, in a sense, set the stage for Webb,"
says team member Anton Koekemoer of the Space Telescope Science Institute in Baltimore. "Our work indicates there is a rich field
of even earlier galaxies that Webb will be able to study."
The title of the Astrophysical Journal Letters paper is, "The Abundance of Star-Forming Galaxies in the Redshift Range 8.5 to 12:
New Results from the 2012 Hubble Ultra Deep Field Campaign." In addition to Ellis, Dunlop, Robertson, and Koekemoer, the other
authors on the Astrophysical Journal Letters paper are Matthew Schenker of Caltech; Ross McLure, Rebecca Bowler, Alexander Rogers,
Emma Curtis-Lake, and Michele Cirasuolo of the Institute for Astronomy at the University of Edinburgh; Yoshiaki Ono and Masami
Ouchi of the University of Tokyo; Evan Schneider of the University of Arizona; Daniel Stark of the University of Cambridge;
Stéphane Charlot of the Institut d'Astrophysique de Paris; and Steven Furlanetto of UCLA. The research was supported by the
Space Telescope Science Institute, the European Research Council, the Royal Society, and the Leverhulme Trust. | 0.883368 | 3.95234 |
13 June 2008 | Lost in space
Nothing like looking at highly-detailed images of another planet to make me feel infinitesimally tiny…but in a very good way.
The web site for the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter currently has 6,137 high-resolution images of the Martian surface available for exploration. According to the Planetary Data System (did you know we had one of those?), HiRISE has released over 26 terabytes of data. The images below are from some of the observations taking place between 20 March and 24 April 2008.
To say that this is a small sampling is an understatement of planetary proportions. These snippets are from the June release of images and I only have looked at the first twenty-three of fifty pages.
Below, they were looking for “change due to mass wasting on scarps of different slopes”. I didn’t know what a scarp was before today, even though I have seen them (here on Earth).
Did you know that a barchan was a crescent-shaped dune? One of the things I love about the HiRISE pages is that many have very detailed descriptions. Click though on the image below for more information on the barchan and,
I am guessing, its smaller relatives, the barchanoids.
Update/correction: Turns out that a barchnoid is not the smaller relative of a barchan, but rather is a transitional form between barchans and dunes…the nuances that come from specializations. “The transition is much more gradual…from barchans to barchanoids, to barchanoids with increasing slipface lengths, to dunes with barchanoid characteristics like crescentic slipfaces and tails, to dunes with irregular slipfaces, to more or less two-dimensional dunes.” [Source] Also, there is an article (PDF) on the geology of sand dunes by John Mangimeli that has some nice illustrations.
Each of the images above is linked directly to its HiRISE page where you can find specific information about the observation and download various versions of the data. I gravitate to the RGB color, non-mapped versions, as shown here.
[Update (26 May 2012): I did not mention in the original post that the images you can download are ridiculously-high resolution and extraordinarily-detailed. I’m just sayin’.]
As a technical note, many of the images are stored in the JPEG2000 format and are very high resolution. During my time lost in the Library of Congress earlier in the week, I came across LizardTech’s ExpressView browser plug-in/viewing application. It handles both MrSID and JPEG2000 files. The plug-in and application come in the same download (as least for Mac OS X). [Update (26 May 2012): LizardTech no longer supports Mac OS X.]
For a final bit of perspective, an observation from 3 October 2007:
That’s our home and our moon seen from the orbit of another planet.
Source for all images: NASA/JPL/University of Arizona HiRISE | 0.857258 | 3.125973 |
By Luca Pasquini, European Southern Observatory
What incredible times we are living in — searching for an Earth around another star! Not much more than 20 years ago, I looked at the few astronomers hunting for planets, and I shook my head and thought “they are crazy”. Similar to many other occasions throughout my life, I was to be proven wrong.
Nature, of course, helped those early planet hunters quite a lot, by making Hot Jupiters. These are systems inducing radial velocity variations 10 times larger, and with much shorter periods, than the giant planets of the Solar System, which were the only ones known at that time. I believe that the influence of the discovery of the first confirmed exoplanet 51 Pegasi b by Mayor and Queloz, will be very long lasting indeed. By proving the existence of what was before then only considered likely to some of us, or an obvious hypothesis for others, their work unleashed a wealth of energy to the subject that had been unthinkable before. We are now able to analyse exoplanet atmospheres, and to search for small mass exoplanets in the habitable zones of other stars, planets that can harbour life in the way we know it.
Such a tremendous explosion of results has only been possible because fundamental technological advancements have taken place in the past 20 years, advancements that now allow us to search for solar systems and Earth analogues.
Previous expert opinions have shown us that, in order to detect the planetary radial velocity signals, a lot of effort is needed to filter the stellar ‘noise’ (activity, oscillation, variability), and in order to best do that, one needs very precise spectroscopy and long observing campaigns. This requires proper instrumentation and dedicated telescopes. Several observatories such as the European Southern Observatory (ESO) are well equipped with both.
Precision is the key word. The radial velocity signal induced by an Earth orbiting around a solar mass star with a period of 1 year, is less than 10 cm s-1. Just to provide some comparison, this implies that we must be able to measure the periodic shift of the stellar radial velocity in the focal plane of a typical high-resolution spectrograph for several orbital periods, over several years with a peak shift of just 2 nanometers (10-9 meters or 0.000000001 meters). In addition to requiring the utmost care in stabilising the instruments in temperature and pressure, reaching such a precision requires a very precise ruler, and for this reason several groups in the world have been engaged for almost a decade in work developing the perfect ruler. Currently the most precise rulers are based on Laser Frequency Combs (LFCs), a technique that led to the Nobel Prize for physics being awarded to T. Hänsch and J. Hall in 2005. The LFC can create a series of precisely equally spaced and stable emission lines for spectrograph calibration, whose frequency is known with high accuracy. The worldwide leader instrument in radial velocity precision is probably HARPS at ESO’s La Silla Observatory in Chile. Up to now it has been using the emission line Thorium-Argon lamps as a ruler, but it has been recently equipped with a prototype Laser Frequency Comb system. The short-term tests of this system indicate that a precision of better than 2 cm s-1 can be reached. Advances in understanding optical fibres and their technology, and getting bigger and better optical detectors have also been vital in obtaining the best performance. Optical CCDs are now very clean devices that can be accurately calibrated.
Great expectations are placed on ESPRESSO, the ‘big brother’ instrument to HARPS, that will be hosted at the ESO Very Large Telescope at Paranal before the end of the year. This instrument will boost the original HARPS precision by one order of magnitude and, in addition, will be used by any of the VLT telescopes, or by the four 8-metre Unit Telescopes together, with a 16 metre telescope equivalent diameter. Often the stars observed are relatively bright, so one could question why large telescopes are needed, but we must realise that high precision requires also a lot of stellar photons, or particles of light, hence the quest for large telescopes. A further step in precision is expected from the high-resolution spectrograph at the 39-meter E-ELT. The CODEX concept was originally conceived to measure Doppler shifts so precise such that we would be able to directly observe the expansion of the Universe and Earth-like planets around solar type stars in their habitable zones. The 25-metre Giant Magellan Telescope is planned to have a similar instrument for its first light.
Planets are cool compared to stars, and emit most of their light as infrared (IR) radiation, which is invisible to the human eye. Expanding observations to this spectral range is therefore essential, and the development of large IR detectors played a fundamental role: progressing in a few years from arrays of a few thousand pixels, to the most recent 16 million pixel devices, which enabled the construction of efficient high resolution infrared (IR) spectrographs. These spectrographs, such as CRIRES at the VLT, have been used to hunt for planets and to observe exoplanet atmospheres. In addition, the radial velocity signal produced by the rotation of inhomogeneities on the stellar surface can mimic the RV periodic variations induced by a planet, but , while the variations induced by the planet are the same for any measured wavelength of light, they are different in the optical and in the IR for the stellar spots that rotate around the star’s surface. That is why the newest generation of spectrographs have a great interest in the IR, and NIRPS, which will be hosted at the ESO 3.6-metre telescope at La Silla, CARMENES at the Calar Alto Observatory, Spirou at CHFT, and the high resolution spectrograph for the E-ELT, will all have an IR arm.
Even if this contribution focuses on radial velocities and spectroscopy, we should not underestimate the power of imaging. NACO at the VLT has imaged the first exoplanet around a very low mass star, similar to Proxima Centauri, and it is beyond any doubt that images, like the one shown below, have been transformational. More powerful high contrast imagers recently became available, imagers such as SPHERE at the VLT and GPI at GEMINI. These create superb images of planets and proto-planetary discs and are able to detect objects more than one million times fainter than the host star. And the next generation of instruments that will be able to exploit the tremendous potential of the ELTs is already taking shape.
Large surveys are now carried out and images of exoplanets are becoming more and more common. The enabling technology has been adaptive optics, a technique that deforms mirrors to compensate for the atmospheric turbulence and therefore recovers the cleanest image of the telescope, as if it was in space, observing with no turbulent atmosphere to look through. Deformable mirrors with more than 1000 actuators, applying corrections faster than 1000 times per second are needed, and they have been developed either of small size, for instance for SPHERE and GPI, or of large size, and these are directly replacing the secondary mirrors of the telescopes, as has happened at the Large Binocular Telescope and soon will occur at the VLT.
In a nutshell, thanks to all these great instruments, exoplanet science has a bright present, and even more promising future.
About the author. Luca Pasquini is an astronomer, working at ESO, Garching, and since 2013 he has been managing the Paranal Instrumentation Programme. After completing his studies in Firenze (Italy), he moved to become an ESA postdoc at MPE (Germany) in 1986, and then went on to ESO La Silla (Chile), where he was in charge of high resolution spectroscopy and of the 3.6m telescope upgrade. In 1997 he moved to ESO Garching, to work in the instrumentation group there. Before his present position, he has been instrument scientist for the FEROS, HARPS, FLAMES, MUSE, and ESPRESSO spectrographs. His scientific work and interests range from stellar activity and stellar abundances, to search for planets around giant stars and around stars in open clusters, as well as to different applications of precision spectroscopy. | 0.89536 | 3.938617 |
Mystery deepens around dark core in cosmic collision
Five years ago, San Francisco State researcher Andisheh Mahdavi and his colleagues observed an unexpected dark core at the center of Abell 520, a cosmic "train wreck" of galaxy clusters. With new space-based telescope observations, they have confirmed that the core really does exist. But they are no closer to explaining why it is there.
When galaxy clusters crash into each other, the bright matter of galaxies sticks together with the mysterious substance called dark matter, leaving behind hot gases. Or at least that is what astronomers have observed in similar cosmic wrecks like the Bullet Cluster. But Myungkook James Jee of the University of California, Davis, Mahdavi and their colleagues say Abell 520 has a definite -- but bewildering -- dark matter core that is completely separated from its usual bright partners.
"We tried to come up with models that would explain this, but there were not any good models," said Mahdavi, an assistant professor in the Department of Physics and Astronomy. "There is no way that you could have cold dark matter piling up like this in a region with so few galaxies."
The researchers first identified the dark core in 2007 using a technique called gravitational lensing. Even though the dark core isn't visible, astronomers can get an idea of its location and size by observing how light from galaxies behind it is distorted by the core's gravitational pull.
"We cannot see dark matter because it does not radiate. What we see is the 'effect' of dark matter," Jee explained. "It's similar to how we cannot see wind directly, but we can tell the presence of wind by looking at the vibration of leaves on a tree."
In this case, the galaxies behind the dark core are the tree leaves. But the 2007 observations came in part from ground-based telescopes, which can detect only a few of the galaxies lurking behind Abell 520. The Earth's atmosphere also distorts the view from the ground, "like looking at a tree inside a house through a frosty window," Jee said.
The researchers decided that they needed further observations from the space-based Hubble Telescope to confirm the dark core's presence. "For every ten galaxies that we were able to see from the ground, we can see 100 from space with the Hubble," they noted, "for a total of about 4000 galaxies from space versus 400 from the ground."
The 2007 study was "a result that basically everyone wished would go away," Mahdavi said, but the new observations published in the Astrophysical Journal show "without a doubt that there is a dark matter concentration in that piece of the sky."
Their results do not put the mystery to rest, however, since the researchers also note in their study that there are no plausible scenarios yet to explain the existence of the dark core. In all other known collisions, bright galaxy matter and dark matter stay together.
Why is Abell 520 so different? It may be that our understanding of how galaxies grow and collide is incomplete, Mahdavi suggests. Alternatively, a new theory of dark matter interaction could be necessary to explain the mysterious core.
Mahdavi thinks that the first scenario is more likely, and that perhaps there are "some sort of freak initial conditions that would create this amount of dark matter."
"But the only way we understand how galaxies grow up is with supercomputer simulations," he noted. The simulations--which would include recreating galaxy cluster collisions under a variety of conditions -- help to calculate how likely it would be to spot an oddball like Abell 520. "My colleagues tell me the likelihood is nil, but now we have the responsibility to go and do the hard work to check the simulations," he said.
If the simulations don't turn up anything to show that Abell 520 is possible, Mahdavi said the mystery might be best left in the hands of particle physicists to revisit their theories about the nature and interactions of dark matter.
"I'm just as perplexed as I was back in 2007," he said. "It's a pretty disturbing observation to have out there. | 0.9096 | 4.035738 |
LOS ANGELES - Astronomers and sky watchers will be ready for a rare celestial event taking place Monday, November 11th. That's when Mercury, our innermost planet, passes directly between Earth and the sun.
This event only happens 13 times every 100 years. These transits are so rare because of Mercury's unusual orbit and how it meshes with Earth's orbit. Mercury's distance from the sun can vary quite a bit, and its orbit has an incline of 7 degrees compared to Earth's orbit. That makes it hard to get the three celestial objects to line up.
The last transit took place in 2016, and the next one won't happen until 2032. Those in the United States though will have to wait even longer when the next Mercury transit occurs in 2049.
The only two planets we can see transitting the sun are Mercury and Venus, since their orbits are inside Earth's orbit. The last Venus transit was in 2012, and the next one won't be until 2117.
The transit will take place Monday morning from 4:35 a.m. to 10:04 a.m. PST. The entire event will last about 5 1/2 hours.
The best places to view the transit includes the east coast of North America, all of South America, western Europe and far-western Africa. For those in most of North America, the transit will already be in progress, since the sun rises at 6:22 a.m. PST. Viewers in most of Africa, eastern Europe and most of Asia will see the transit as the sun sets. Sorry Australia, you're out of luck this time around.
This map shows where and when the transit will be visible on November 11. Image credit: NASA/JPL-Caltech
When Mercury transits, it will appear as a tiny black dot against the sun.
One fascinating observation of any transit is the "black drop effect", an optical illusion that happens when the planet either just enters or starts to leave the sun’s disk. When Mercury’s leading edge first touches the sun, the planet will appear to grow a narrow neck connecting it to the edge of the sun, making the silhouette look like a teardrop. This strange apparition happens again just as Mercury becomes engulfed by the sun’s disk.
The transit of Mercury on Nov. 11, 2019, begins at 4:35 a.m. PST (7:35 a.m. EST), but it won’t be visible to West Coast viewers until after sunrise. Luckily, viewers will have several more hours to take in the stellar show, which lasts until 10:04 a.
"Because Mercury is so small from our perspective on Earth, you'll need binoculars or a telescope with a Sun filter to see it," NASA wrote on it's website.
If you plan on viewing the transit:
• Do not stare directly at the sun with the naked eye.
• Do not look at the sun through binoculars or a telescope while wearing solar eclipse glasses.
• Do not place your solar eclipse glasses over your binoculars or telescope, either.
To save your eyes from potential blindness, the best way to view the Mercury transit is to use a telescope with a compatible solar filter.
And let's all hope for clear skies, too.
Since Monday is a holiday (Veteran's Day), Griffith Observatory in Los Angeles will not have a public event, but you can view the transit live online through Griffith Observatory's live stream. The Virtual Telescope Project will also host an online viewing event, and astrononmy streaming service Slooh will provide a live stream on YouTube. | 0.888548 | 3.357933 |
Patek Philippe 6102R
When you’re travelling from one celestial body to another within the 100 billion or so stars that make up our galaxy, which itself is one of 100 billion galaxies within the observable universe, it’s nice to have something to remember your place amongst it all. Interstellar hitchhiker Arthur Dent had his towel to remind him of home; perhaps if he’d had £220,000 to spend, he could have had this instead: the Patek Philippe 6102R.
“Far out in the uncharted backwaters of the unfashionable end of the western spiral arm of the galaxy lies a small unregarded yellow sun. Orbiting this at a distance of roughly ninety-two million miles is an utterly insignificant little blue-green planet whose ape-descended life forms are so amazingly primitive that they still think digital watches are a pretty neat idea.” Douglas Adams’ The Hitchhiker’s Guide to the Galaxy presents such an incredibly succinct reminder of just how small we are in this universe that it rather nicely sets the scene for what the Patek Philippe 6102R is all about.
That’s because the view on the dial of the 6102R is from that very same insignificant little blue-green planet, looking out over the western spiral arm of our home galaxy we call the Milky Way. Seen on the blackest of nights as a smear across the sky, it was as early as 500 BC that Greek philosopher Anaxagoras pondered if it might be made up of a collective of distant stars. He was right, but to grasp what that really meant was just too great for the thinkers that followed.
Just take a moment to understand what this means; we look up at night and see stars, discrete points of light blotting the sky, and we understand to a degree that these are objects that are very far away. But the Milky Way, the fuzz that stains the sky, looks that way because it too is made of discreet points of light, but in their hundreds of billions, so distant that they blur into one. The mind simply cannot comprehend such a staggering thought, and so a millennium had passed before the idea was even contemplated again, with the prevailing belief that it was a cloud in the Earth’s upper atmosphere.
And it was yet another millennium before Galileo Galilei saw through a telescope that the Milky Way was indeed a collection of distant stars, with Immanuel Kant theorising a century later that the galaxy was a rotating disk held together by gravity. With a low estimate of 100 billion stars—400 billion if you’re feeling optimistic—and a 100 billion planets, all travelling at some 600km per second, it’s no wonder that humanity took as long as it did to accept the truth.
Once again, Douglas Adams summarises this in The Hitchhiker’s Guide to the Galaxy with the Total Perspective Vortex, a device built with the sole purpose of showing a person the entire scale of the universe and their insignificance compared. It would send them mad, and rightly so; if it is so difficult to comprehend the existence of a mass of 100 billion stars, being forced to perceive a further 100 billion of those masses of a 100 billion stars is a sheer impossibility.
But the head-scratching doesn’t end there, because what we observe in our galaxy only makes up a tiny five percent of what’s actually there. The remaining ninety-five percent is made up of dark matter—stuff that has gravity but can’t be seen—and dark energy—stuff that’s causing the expansion of the universe to accelerate that also can’t be seen. Imagine what the dial of this Patek Philippe 6102R might look like if we could.
It’s this vision of the sky that makes the Patek Philippe 6102R so incredible. That’s because if you were to take a look up at the stars from Geneva, what’s shown on the dial here is what you’d see. The 6102R doesn’t just portray a representation of the Milky Way, it shows you exactly what it looks like.
You’ll notice the white ellipse surrounded by compass directions on this celestial image; that’s the horizon line, a window up into the universe as it would be seen for real. Look to the south and stars you’d see just above the Earth’s edge would be the same skimming the horizon line, and that’s true of every direction you might care to try. Thanks to a 356-tooth sapphire disk just two tenths of a millimetre thick, the view of the galaxy can rotate in real time to keep the dial accurate.
A lunar display, also printed on sapphire, joins the distant stars negotiating the night sky—but what’s even more impressive is that an additional window and an additional disk give the lunar display the capability to represent the phases of the moon as well.
It was through searching over 25 billion gear ratios for the planetary system in the hand-finished calibre 240 LU CL C that Patek Philippe was able to maintain an accuracy for the celestial display of just 0.08 seconds per day, and for the lunar complication an even more impressive 0.05 seconds per day. Despite the complexity of the 315 parts, the calibre remains just 6.81mm thick, the watch itself a whisker over 10mm altogether.
Twin crowns adjust the time and the celestial complications, with a further hidden pusher for the surrounding date, and a fine scale around the dial aids with accurate setting. But the real pleasure is in just looking at the 6102R, to peer through the lens and into the infinite depths of the universe, to the core of our galaxy within which a supermassive black hole consumes matter at an astronomical rate.
It’s a cosmological journey Patek Philippe owners have been able to take since the 1927 ‘Packard’, a grand complication pocket watch—Patek Philippe’s first—custom-made for the American industrialist James Ward Packard. Whilst the front of the Packard was emblazoned with incredible complications like a perpetual calendar, and sunrise and sunset, it was under the rear cover that the magic lay. Lift the gold lid and an astronomical display, just like this one, was revealed.
The celestial complication continues to be one of Patek Philippe’s most prestigious and beautiful, tapping into not just a human fascination with engineering and art, but also with the exploration of the cosmos. Just as a lucky few will get to explore beyond our Earth’s atmosphere, only a lucky few will be able to enjoy Patek Philippe’s view of it.
It’s hardly surprising to see a complication of this magnitude in a Patek Philippe, but that doesn’t make it any less astonishing to behold. By modern standards, this is primitive technology, yet it can accurately describe our view of the stars with a discrepancy of less than an hour per century. And it depicts not only a celestial map, but also a view that has entranced humans since the very first time we looked up and understood the sheer scale of what we were seeing. To quote Douglas Adams once more: “Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.”
Looking for a Patek Philippe watch? Click here to shop now | 0.858691 | 3.694146 |
March 10, 2016 – The engineers huddled around a telemetry screen, and the mood was tense. They were watching streams of data from a crippled spacecraft more than 50 million miles away – so far that even at the speed of light, it took nearly nine minutes for a signal to travel to the spacecraft and back.
It was late August 2013, and the group of about five employees at Ball Aerospace in Boulder, Colorado, was waiting for NASA’s Kepler space telescope to reveal whether it would live or die. A severe malfunction had robbed the planet-hunting Kepler of its ability to stay pointed at a target without drifting off course.
The engineers had devised a remarkable solution: using the pressure of sunlight to stabilize the spacecraft so it could continue to do science. Now, there was nothing more they could do but wait for the spacecraft to reveal its fate.
“You’re not watching it unfold in real time,” said Dustin Putnam, Ball’s attitude control lead for Kepler. “You’re watching it as it unfolded a few minutes ago, because of the time the data takes to get back from the spacecraft.”
Finally, the team received the confirmation from the spacecraft they had been waiting for. The room broke out in cheers. The fix worked! Kepler, with a new lease on life, was given a new mission as K2. But the biggest surprise was yet to come. A space telescope with a distinguished history of discovering distant exoplanets – planets orbiting other stars – was about to outdo even itself, racking up hundreds more discoveries and helping to usher in entirely new opportunities in astrophysics research.
“Many of us believed that the spacecraft would be saved, but this was perhaps more blind faith than insight,” said Tom Barclay, senior research scientist and director of the Kepler and K2 guest observer office at NASA’s Ames Research Center in California’s Silicon Valley. “The Ball team devised an ingenious solution allowing the Kepler space telescope to shine again.”
The Discoveries Roll In
A little more than two years after the tense moment for the Ball engineers, K2 has delivered on its promise with a breadth of discoveries. Continuing the exoplanet-hunting legacy, K2 has discovered more than three dozen exoplanets and with more than 250 candidates awaiting confirmation. A handful of these worlds are near-Earth-sized and orbit stars that are bright and relatively nearby compared with Kepler discoveries, allowing scientists to perform follow-up studies. In fact, these exoplanets are likely future targets for the Hubble Space Telescope and the forthcoming James Webb Space Telescope (JWST), with the potential to study these planets’ atmospheres in search of signatures indicative of life.
K2 also has astronomers rethinking long-held planetary formation theory, and the commonly understood lonely “hot Jupiter” paradigm. The unexpected discovery of a star with a close-in Jupiter-sized planet sandwiched between two smaller companion planets now has theorists back at their computers reworking the models, and has sent astronomers back to their telescopes in search of other hot Jupiter companions.
“It remains a mystery how a giant planet can form far out and migrate inward leaving havoc in its wake and still have nearby planetary companions,” said Barclay.
Like its predecessor, K2 searches for planetary transits – the tiny, telltale dip in the brightness of a star as a planet crosses in front – and for the first time caught the rubble from a destroyed exoplanet transiting across the remains of a dead star known as a white dwarf. Exoplanets have long been thought to orbit these remnant stars, but not until K2 has the theory been confirmed.
K2 has fixed its gaze on regions of the sky with densely packed clusters of stars which has revealed the first transiting exoplanet in such an area, popularly known as the Hyades star cluster. Clusters are exciting places to find exoplanets because stars in a cluster all form around the same time, giving them all the same “born-on” date. This helps scientists understand the evolution of planetary systems.
The repurposed spacecraft boasts discoveries beyond the realm of exoplanets. Mature stars – about the age of our sun and older – largely populated the original single Kepler field of view. In contrast, many K2 fields see stars still in the process of forming. In these early days, planets also are assembled and by looking at the timescales of star formation, scientists gain insight into how our own planet formed.
Studies of one star-forming region, called Upper Scorpius, compared the size of young stars observed by K2 with computational models. The result demonstrated fundamental imperfections in the models. While the reason for these discrepancies is still under debate, it likely shows that magnetic fields in stars do not arise as researchers expect.
Looking in the ecliptic – the orbital path traveled around the sun by the planets of our solar system and the location of the zodiac – K2 also is well equipped to observe small bodies within our own solar system such as comets, asteroids, dwarf planets, ice giants and moons. Last year, for instance, K2 observed Neptune in a dance with its two moons, Triton and Nereid. This was followed by observations of Pluto and Uranus.
“K2 can’t help but observe the dynamics of our planetary system, ” said Barclay. “We all know that planets follow laws of motion but with K2 we can see it happen.”
These initial accomplishments have come in the first year and a half since K2 began in May 2014, and have been carried off without a hitch. The spacecraft continues to perform nominally.
Searching For Far Out Worlds
In April, K2 will take part in a global experiment in exoplanet observation with a special observing period or campaign, Campaign 9. In this campaign, both K2 and astronomers at ground-based observatories on five continents will simultaneously monitor the same region of sky towards the center of our galaxy to search for small planets, such as the size of Earth, orbiting very far from their host star or, in some cases, orbiting no star at all.
For this experiment, scientists will use gravitational microlensing – the phenomenon that occurs when the gravity of a foreground object, such as a planet, focuses and magnifies the light from a distant background star. This detection method will allow scientists to find and determine the mass of planets that orbit at great distances, like Jupiter and Neptune do our sun.
Design By Community
What could turn out to be one of the most important legacies of K2 has little to do with the mechanics of the telescope, now operating on two wheels and with an assist from the sun.
The Kepler mission was organized along traditional lines of scientific discovery: a targeted set of objectives carefully chosen by the science team to answer a specific question on behalf of NASA – how common or rare are “Earths” around other suns?
K2’s modified mission involves a whole new approach– engaging the scientific community at large and opening up the spacecraft’s capabilities to a broader audience.
“The new approach of letting the community decide the most compelling science targets we’re going to look at has been one of the most exciting aspects,” said Steve Howell, the Kepler and K2 project scientist at Ames. “Because of that, the breadth of our science is vast, including star clusters, young stars, supernovae, white dwarfs, very bright stars, active galaxies and, of course, exoplanets.”
In the new paradigm, the K2 team laid out some broad scientific objectives for the mission and planned to operate the spacecraft on behalf of the community.
Kepler’s field of view surveyed just one patch of sky in the northern hemisphere. The K2 ecliptic field of view provides greater opportunities for Earth-based observatories in both the northern and southern hemispheres, allowing the whole world to participate.
With more than two years of fuel remaining, the spacecraft’s scientific future continues to look unexpectedly bright.
Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA’s Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. | 0.901787 | 3.107516 |
This week brings a video reconstructed from images of the Philae lander's approach to a comet, and a major new analysis of data from the Cassini mission that bolsters the case for a global, not just local, ocean beneath the icy crust of Enceladus.
When the European Space Agency's small lander Philae attempted to set down on the nucleus of comet 67P/C-G back in November 2014 it had a rough time, ultimately bouncing and ending up wedged in unfortunate circumstances on the surface.
But during its slow descent it did manage to send a series of 7 images from between 67 and 9 meters above the landing site. Now these images have been carefully assembled and interpolated to produce a video that simulates what Philae was actually experiencing during that time. You can watch it here.
Perhaps the most striking aspect of this movie is just how cautious the approach was. From the range data it's apparent that Philae was drifting in at not much more than a meter a second - yet it bounced big time. A cometary nucleus this size has a truly pitiful gravitational field, which makes it very hard to hit and stick.
And for a different type of water rich object, the ice-shrouded Saturnian moon Enceladus, hundreds of millions of miles further away, comes the tour de force of a fascinating new analysis of seven years' worth of image data from NASA's Cassini mission.
By tagging distinct features on Enceladus's surface, such as craters, scientists have been able to build a quantitative picture of how this small moon wobbles as it orbits Saturn.
Like most astrophysical objects, Enceladus may look perfectly spherical, but it isn't really. As a consequence, while Enceladus moves through its slightly elliptical orbit, Saturn's gravitational field rocks the moon back and forth - or 'librates' it by tiny amounts.
The position of features in hundreds of Cassini images has allowed the researchers to track these librations. They've discovered that the back and forth wobbles of this moon (about 0.12 degrees in amplitude) are much larger than they should be if most of the interior were solid ice or rock.
Good evidence already exists for some kind of liquid water 'pocket' towards Enceladus's south pole - where it regularly erupts with plumes of water ice and other compounds that suggest a deeper hydrothermal system - but the excess wobble of the whole moon now indicates that there is in fact a global ocean.
This body of liquid, likely composed of salt-rich water, helps disconnect the icy crust from the core of the moon, and allows for the big librations seen in the measurements. It could be some 30-40 kilometers in depth, starting perhaps 10 or 20 kilometers below the surface.
It's a very exciting result, an extra feather in the cap for Enceladus as a prime target to search for life in the solar system. It also raises an intriguing puzzle as to how this ocean is kept warm.
In one of the mission's final flourishes, on October 28th, Cassini will make its closest ever flyby of the active icy plumes - plunging through their territory a mere 49 kilometers above the surface of Enceladus. We'll have to wait and see if this little moon has any more surprises in store for us from that encounter. | 0.877503 | 3.995695 |
Since it established orbit around Jupiter in July of 2016, the Juno mission has been sending back vital information about the gas giant’s atmosphere, magnetic field and weather patterns. With every passing orbit – known as perijoves, which take place every 53 days – the probe has revealed more interesting things about Jupiter, which scientists will rely on to learn more about its formation and evolution.
During its latest pass, the probe managed to provide the most detailed look to date of the planet’s interior. In so doing, it learned that Jupiter’s powerful magnetic field is askew, with different patterns in it’s northern and southern hemispheres. These findings were shared on Wednesday. Oct. 18th, at the 48th Meeting of the American Astronomical Society’s Division of Planetary Sciencejs in Provo, Utah.
Ever since astronomers began observing Jupiter with powerful telescopes, they have been aware of its swirling, banded appearance. These colorful stripes of orange, brown and white are the result of Jupiter’s atmospheric composition, which is largely made up of hydrogen and helium but also contains ammonia crystals and compounds that change color when exposed to sunlight (aka. chromofores).
Until now, researchers have been unclear as to whether or not these bands are confined to a shallow layer of the atmosphere or reach deep into the interior of the planet. Answering this question is one of the main goals of the Juno mission, which has been studying Jupiter’s magnetic field to see how it’s interior atmosphere works. Based on the latest results, the Juno team has concluded that hydrogen-rich gas is flowing asymmetrically deep in the planet.
These findings were also presented in a study titled Comparing Jupiter interior structure models to Juno gravity measurements and the role of a dilute core, which appeared in the May 28th issue of Geophysical Research Letters. The study was led by Sean Wahl, a grad student from UC Berkeley, and included members from the Weizmann Institute of Science, the Southwest Research Institute (SwRI), NASA’s Goddard Space Flight Center and the Jet Propulsion Laboratory.
Another interesting find was that Jupiter’s gravity field varies with depth, which indicated that material is flowing as far down as 3,000 km (1,864 mi). Combined with information obtained during previous perijoves, this latest data suggests that Jupiter’s core is small and poorly defined. This flies in the face of previous models of Jupiter, which held that the outer layers are gaseous while the interior ones are made up of metallic hydrogen and a rocky core.
As Tristan Guillot – a planetary scientist at the Observatory of the Côte d’Azur in Nice, France, and a co-author on the study – indicated during the meeting, “This is something that was not expected. We were not sure at all whether we would be able to see that… It’s clear that giant planets have a lot of secrets.”
But of course, more passes and data are needed in order to pinpoint how strong the flow of gases are at various depths, which could resolve the question of how Jupiter’s interior is structured. In the meantime, the Juno scientists are pouring over the probe’s gravity data hoping to see what else it can teach them. For instance, they also want to know how far the Great Red Spot extends into the amotpshere.
This anticyclonic storm, which was first spotted in the 17th century, is Jupiter’s most famous feature. In addition to being large enough to swallow Earth whole – measuring some 16,000 kilometers (10,000 miles) in diameter – wind speeds can reach up to 120 meters per second (432 km/h; 286 mph) at its edges. Already the JunoCam has snapped some very impressive pictures of this storm, and other data has indicated that the storm could run deep.
In fact, on July 10th, 2017, the Juno probe passed withing 9,000 km (5,600 mi) of the Great Red Spot, which took place during its sixth orbit (perijove six) of Jupiter. With it’s suite of eight scientific instruments directed at the storm, the probe obtained readings that indicated that the Great Red Spot could also extend hundreds of kilometers into the interior, or possibly even deeper.
As David Stevenson, a planetary scientist at the California Institute of Technology and a co-author on the study, said during the meeting, “It’s not yet clear that it is so deep it will show up in gravity data. But we’re trying”.
Other big surprises which Juno has revealed since it entered orbit around Jupiter include the clusters of cyclones located at each pole. These were visible to the probe’s instruments in both the visible and infrared wavelengths as it made its first maneuver around the planet, passing from pole to pole. Since Juno is the first space probe in history to orbit the planet this way, these storms were previously unknown to scientists.
In total, Juno spotted eight cyclonic storms around the north pole and five around the south pole. Scientists were especially surprised to see these, since computer modelling suggests that such small storms would not be stable around the poles due to the planet’s swirling polar winds. The answer to this, as indicated during the presentation, may have to do with a concept known as vortex crystals.
As Fachreddin Tabataba-Vakili – a planetary scientist at NASA’s Jet Propulsion Laboratory and a co-author on the study – explained, such crystals are created when small vortices form and persist as the material in which they are embedded continues to flow. This phenomenon has been seen on Earth in the form of rotating superfluids, and Jupiter’s swirling poles may possess similar dynamics.
In the short time that Juno has been operating around Jupiter, it has revealed much about the planet’s atmosphere, interior, magnetic field and internal dynamics. Long after the mission is complete – which will take place in February of 2018 when the probe is crashed into Jupiter’s atmosphere – scientists are likely to be sifting through all the data it obtained, hoping to solve any remaining mysteries from the Solar System’s largest and most massive planet.
Further Reading: Nature | 0.875725 | 3.918208 |
This busy image is a treasure trove of wonders. Bright stars from the Milky Way sparkle in the foreground, the magnificent swirls of several spiral galaxies are visible across the frame, and a glowing assortment of objects at the centre make up a massive galaxy cluster. Such clusters are the biggest objects in the Universe that are held together by gravity, and can contain thousands of galaxies of all shapes and sizes. Typically, they have a mass of about one million billion times the mass of the Sun — unimaginably huge!
Their incredible mass makes clusters very useful natural tools to test theories in astronomy, such as Einstein’s theory of general relativity. This tells us that objects with mass warp the fabric of spacetime around them; the more massive the object, the greater the distortion. An enormous galaxy cluster like this one therefore has a huge influence on the spacetime around it, even distorting the light from more distant galaxies to change a galaxy’s apparent shape, creating multiple images, and amplifying the galaxy’s light — a phenomenon called gravitational lensing.
This image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3 as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study. | 0.833748 | 3.382949 |
This spring, astronomers at the Arecibo Observatory in Puerto Rico were sorting through data from recent observations when they found something strange. The radio telescope had detected what they describe as “some very peculiar signals” coming from a nearby star, unlike anything they had ever observed before.
The star in question is Ross 128, a red dwarf located about 11 light-years from Earth in the constellation Virgo. Red dwarfs are the smallest and most common types of stars in the universe. They’re far dimmer than stars like our sun, and can’t be seen with the naked eye. For about 10 minutes on May 12, a radio transmission came from the direction of Ross 128. Stars can emit various wavelengths of electromagnetic radiation, including radio waves. But the pulses that came from Ross 128 were at a frequency astronomers haven’t detected before in red dwarfs.
The Arecibo astronomers reported the mystery detection in an online post last week, but they don’t yet know its origins.
There are several possible explanations, all of which have some limitations. Scientists have known for decades that red dwarfs can emit flares, intense eruptions of electromagnetic radiation, like the kind that occur on our own sun. But the flares that have been observed on red dwarfs occur at much lower frequencies and travel in different directions than what was seen around Ross 128. If the cause is indeed a solar flare, it would be a new classification of flares astronomers have never observed before.
The radio signals could be coming from another object in the telescope’s field of view of Ross 128, but astronomers haven’t observed many other celestial bodies there.
They could have been emitted by a passing satellite, a common occurrence in stellar observations. But the astronomers say they have never seen satellites release signals of this nature.
The signals could be the product of some kind of interaction between the star and an orbiting planet. The Arecibo Observatory astronomers believe the interplay between closely orbiting planets and the star’s magnetic field could produce tiny changes in its radio emissions. The Arecibo Observatory actively studies seven red dwarfs, two of which have known planets. But so far, no planets have been discovered around Ross 128.
The signals could be the result of radio frequency interference, a common culprit in the search for extraterrestrial life. The source could be something as small as a cell phone. “There are lots and lots of ways for our technology here on Earth to leak into our radio telescope observations,” says Andrew Siemion, the director of the Berkeley SETI Research Center who leads the center’s Breakthrough Listen Initiative, a project aimed at finding evidence of extraterrestrial civilizations.
But the Arecibo astronomers don’t think that’s it. “We believe that the signals are not local radio frequency interferences since they are unique to Ross 128 and observations of other stars immediately before and after did not show anything similar,” Abel Méndez, the director of the Planetary Habitability Laboratory at the Arecibo Observatory, wrote last week.
Which brings us, finally, to what astronomers believe is the least likely explanation: aliens. “That’s a remote possibility,” Siemion said. “But at this point, it is indeed a possibility.”
Astronomers must first rule out the aforementioned theories, all of which they say are far more plausible. “The recurrent aliens hypothesis is at the bottom of [the list of] many other better explanations,” Méndez wrote in his post.
So, what’s next? Astronomers must spend more time observing Ross 128. The Arecibo Observatory scanned the star again on Sunday, and will announce any new findings this week. The Breakthrough Listen team, acting on the Arecibo astronomers’ request for help, observed Ross 128 on Sunday using the Green Bank radio telescope in West Virginia. Siemion said there was no evidence of the emission Arecibo found back in May, but added that their findings are not conclusive.
Astronomers could try to come up with a theoretical model that could replicate the mysterious radio signals, or attempt to observe Ross 128 with optical telescopes.
Red dwarfs like Ross 128 are particularly interesting targets in the search for extraterrestrial life. Their small size and luminosity make it easier for telescopes to spot objects that could be planets as they pass in front of them. Data from the Kepler Space Telescope, the premiere exoplanet-hunting mission, suggest many red dwarfs may have planets, some of which could be orbiting in the habitable zone, where temperatures are just right for liquid water to pool on the surface. Last year, astronomers discovered a planet orbiting in the habitable zone of Proxima Centauri, a red dwarf and the closest star to Earth, located about four light-years away.
For now, astronomers are just as in the dark as the rest of us about Ross 128. On Monday, Méndez tweeted a link to a survey that asked users to pick which source they believe explains the mysterious phenomenon.
We want to hear what you think about this article. Submit a letter to the editor or write to [email protected]. | 0.869191 | 3.99318 |
Dawn’s approach and trajectory as it begins its orbital “dance” with Ceres. As you watch, note the timeline at upper right.
Dawn made it! After a 14-month tour of the asteroid Vesta and 2 1/2 years en route to Ceres, the spacecraft felt the gentle tug of Ceres gravity and slipped into orbit around the dwarf planet at 6:39 a.m. (CST) Friday morning.
“We feel exhilarated,” said lead researcher Chris Russell at the University of California, Los Angeles, after Dawn radioed back the good news.
Not only is this humankind’s first probe to orbit a dwarf planet, Dawn is the only spacecraft to fly missions to two different planetary bodies. Dawn’s initial orbit places it 38,000 miles (61,000 km) from Ceres with a view of the opposite side of Ceres from the Sun. That’s why we’ll be seeing photos of the dwarf planet as a crescent for the time being. If you watch the video, you’ll notice that Dawn won’t see Ceres’ fully sunlit hemisphere until early-mid April.
The spacecraft will spend the next month gradually spiraling down to Ceres to reach its “survey orbit” of 2,730 miles in April. From there it will train its science camera and visible and infrared mapping spectrometer to gather pictures and data. The leisurely pace of the orbit will allow Dawn to spend more than 37 hours examining Ceres’ dayside per revolution. NASA will continue to lower the spacecraft throughout the year until it reaches its minimum altitude of 235 miles.
“Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet,” said Marc Rayman, Dawn chief engineer and mission director at JPL. “Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres, home.”
More about Dawn’s incredible accomplishment can be found in the excellent Dawn Journal, written by Dawn chief engineer and mission director Marc Rayman. | 0.830065 | 3.02463 |
We are at a special moment in our journey to understand the universe and the physical laws that govern it. More than ever before astronomical discoveries are driving the frontiers of elementary particle physics, and more than ever before our knowledge of the elementary particles is driving progress in understanding the universe and its contents. The Committee on the Physics of the Universe was convened in recognition of the deep connections that exist between quarks and the cosmos.
Both disciplines—physics and astronomy—have seen stunning progress within their own realms of study in the past two decades. The advances made by physicists in understanding the deepest inner workings of matter, space, and time and by astronomers in understanding the universe as a whole as well as the objects within it have brought these scientists together in new ways. The questions now being asked about the universe at its two extremes—the very large and the very small—are inextricably intertwined, both in the asking and in the answering, and astronomers and physicists have been brought together to address questions that capture everyone’s imagination.
The answers to these questions strain the limits of human ingenuity, but the questions themselves are crystalline in their clarity and simplicity. In framing this report, the committee has seized on 11 particularly direct questions that encapsulate most of the physics and astrophysics discussed here. They do not cover all of these fields but focus instead on the interface between them. They are also questions that we have a good chance of answering in the next decade, or should be thinking about answering in
following decades. Among them are the most profound questions that human beings have ever posed about the cosmos. The fact that they are ripe now, or soon will be, further highlights how exciting the possibilities of this moment are. The 11 questions are these:
What Is Dark Matter?
Astronomers have shown that the objects in the universe, from galaxies a million times smaller than ours to the largest clusters of galaxies, are held together by a form of matter different from what we are made of and that gives off no light. This matter probably consists of one or more as-yet-undiscovered elementary particles, and aggregations of it produce the gravitational pull leading to the formation of galaxies and large-scale structures in the universe. At the same time these particles may be streaming through our Earth-bound laboratories.
What Is the Nature of Dark Energy?
Recent measurements indicate that the expansion of the universe is speeding up rather than slowing down. This discovery contradicts the fundamental idea that gravity is always attractive. It calls for the presence of a form of energy, dubbed “dark energy,” whose gravity is repulsive and whose nature determines the destiny of our universe.
How Did the Universe Begin?
There is evidence that during its earliest moments the universe underwent a tremendous burst of expansion, known as inflation, so that the largest objects in the universe had their origins in subatomic quantum fuzz. The underlying physical cause of this inflation is a mystery.
Did Einstein Have the Last Word on Gravity?
Black holes are ubiquitous in the universe, and their intense gravity can be explored. The effects of strong gravity in the early universe have observable consequences. Einstein’s theory should work as well in these situations as it does in the solar system. A complete theory of gravity should incorporate quantum effects—Einstein’s theory of gravity does not—or explain why they are not relevant.
What Are the Masses of the Neutrinos, and How Have They Shaped the Evolution of the Universe?
Cosmology tells us that neutrinos must be abundantly present in the universe today. Physicists have found evidence that they have a small mass, which implies that cosmic neutrinos account for as much mass as do stars. The pattern of neutrino masses can reveal much about how nature’s forces are unified, how the elements in the periodic table were made, and possibly even the origin of ordinary matter.
How Do Cosmic Accelerators Work and What Are They Accelerating?
Physicists have detected an amazing variety of energetic phenomena in the universe, including beams of particles of unexpectedly high energy but of unknown origin. In laboratory accelerators, we can produce beams of energetic particles, but the energy of these cosmic beams far exceeds any energies produced on Earth.
Are Protons Unstable?
The matter of which we are made is the tiny residue of the annihilation of matter and antimatter that emerged from the earliest universe in not-quite-equal amounts. The existence of this tiny imbalance may be tied to a hypothesized instability of protons, the simplest form of matter, and to a slight preference for the formation of matter over antimatter built into the laws of physics.
What Are the New States of Matter at Exceedingly High Density and Temperature?
The theory of how protons and neutrons form the atomic nuclei of the chemical elements is well developed. At higher densities, neutrons and protons may dissolve into an undifferentiated soup of quarks and gluons, which can be probed in heavy-ion accelerators. Densities beyond nuclear densities occur and can be probed in neutron stars, and still higher densities and temperatures existed in the early universe.
Are There Additional Space-Time Dimensions?
In trying to extend Einstein’s theory and to understand the quantum nature of gravity, particle physicists have posited the existence of space-
time dimensions beyond those that we know. Their existence could have implications for the birth and evolution of the universe, could affect the interactions of the fundamental particles, and could alter the force of gravity at short distances.
How Were the Elements from Iron to Uranium Made?
Scientists’ understanding of the production of elements up to iron in stars and supernovae is fairly complete. Important details concerning the production of the elements from iron to uranium remain puzzling.
Is a New Theory of Matter and Light Needed at the Highest Energies?
Matter and radiation in the laboratory appear to be extraordinarily well described by the laws of quantum mechanics, electromagnetism, and their unification as quantum electrodynamics. The universe presents us with places and objects, such as neutron stars and the sources of gamma ray bursts, where the conditions are far more extreme than anything we can reproduce on Earth that can be used to test these basic theories.
Each question reveals the interdependence between discovering the physical laws that govern the universe and understanding its birth and evolution and the objects within it. The whole of each question is greater than the sum of the astronomy part and the physics part of which it is made. Viewed from a perspective that includes both astronomy and physics, these questions take on a greater urgency and importance.
Taken as a whole, the questions address an emerging model of the universe that connects physics at the most microscopic scales to the properties of the universe and its contents on the largest physical scales. This bold construction relies on extrapolating physics tested today in the laboratory and within the solar system to the most exotic astronomical objects and to the first moments of the universe. Is this ambitious extrapolation correct? Do we have a coherent model? Is it consistent? By measuring the basic properties of the universe, of black holes, and of elementary particles in very different ways, we can either falsify this ambitious vision of the universe or establish it as a central part of our scientific view.
The science, remarkable in its richness, cuts across the traditional boundaries of astronomy and physics. It brings together the frontier in the
quest for an understanding of the very nature of space and time with the frontier in the quest for an understanding of the origin and earliest evolution of the universe and of the most exotic objects within it.
Realizing the extraordinary opportunities at hand will require a new, crosscutting approach that goes beyond viewing this science as astronomy or physics and that brings to bear the techniques of both astronomy and physics, telescopes and accelerators, and ground- and space-based instruments. The goal then is to create a new strategy. The obstacles are sometimes disciplinary and sometimes institutional, because the science lies at the interface of two mature disciplines and crosses the boundaries of three U.S. funding agencies: the Department of Energy (DOE), the National Aeronautics and Space Administration (NASA), and the National Science Foundation (NSF). If a cross-disciplinary, cross-agency approach can be mounted, the committee believes that a great leap can be made in understanding the universe and the laws that govern it.
The second part of the charge to the committee was to recommend a plan of action for NASA, NSF, and DOE. In Chapter 7, it does so. First, the committee reviewed the projects in both astronomy and physics that have been started (or are slated to start) and are especially relevant to realizing the science opportunities that have been identified. Next, it turned its attention to new initiatives that will help to answer the 11 questions. The committee summarizes its strategy in the seven recommendations described below.
Within these recommendations the committee discusses six future projects that are critical to realizing the great opportunities before us. Three of them—the Large Synoptic Survey Telescope, the Laser Interferometer Space Antenna, and the Constellation-X Observatory—were previously identified and recommended for priority by the 2001 National Research Council decadal survey of astronomy, Astronomy and Astrophysics in the New Millennium, on the basis of their ability to address important problems in astronomy. The committee adds its support, on the basis of the ability of the projects to also address science at the intersection of astronomy and physics. The other three projects—a wide-field telescope in space; a deep underground laboratory; and a cosmic microwave background polarization experiment—are truly new initiatives that have not been previously recommended by other NRC reports. The committee hopes that these new projects will be carried out or at least started on the same time scale as the projects discussed in the astronomy decadal survey, i.e., over the next 10 years or so.
The initiative outlined by the committee’s recommendations can realize many of the special scientific opportunities for advancing our understand
ing of the universe and the laws that govern it, but not within the budgets of the three agencies as they stand. The answer is not simply to trim the existing programs in physics and astronomy to make room for these new projects, because many of these existing programs—created to address exciting and timely questions squarely within physics or astronomy—are also critical to answering the 11 questions at the interface of the two disciplines. New funds will be needed to realize the grand opportunities before us. These opportunities are so compelling that some projects have already attracted international partners and others are likely to do so.
Listed below are the committee’s seven recommendations for research and research coordination needed to address the 11 science questions.
Measure the polarization of the cosmic microwave background with the goal of detecting the signature of inflation. The committee recommends that NASA, NSF, and DOE undertake research and development to bring the needed experiments to fruition.
Cosmic inflation holds that all the structures we see in the universe today—galaxies, clusters of galaxies, voids, and the great walls of galaxies—originated from subatomic quantum fluctuations that were stretched to astrophysical size during a tremendous spurt of expansion (inflation). Quantum fluctuations in the fabric of space-time itself lead to a cosmic sea of gravitational waves that can be detected by their polarization signature in the cosmic microwave background radiation.
Determine the properties of dark energy. The committee supports the Large Synoptic Survey Telescope project, which has significant promise for shedding light on the dark energy. The committee further recommends that NASA and DOE work together to construct a wide-field telescope in space to determine the expansion history of the universe and fully probe the nature of dark energy.
The discovery that the expansion of the universe is speeding up and not slowing down through the study of distant supernovae has revealed the presence of a mysterious new energy form that accounts for two-thirds of all the matter and energy in the universe. Because of its diffuse nature, this energy can only be probed through its effect on the expansion of the universe. The NRC’s most recent astronomy decadal survey recommended
building the Large Synoptic Survey Telescope to study transient phenomena in the universe; the telescope will also have significant ability to probe dark energy. To fully characterize the expansion history and probe the dark energy will require a wide-field telescope in space (such as the Supernova/ Acceleration Probe) to discover and precisely measure the light from very distant supernovae.
Determine the neutrino masses, the constituents of the dark matter, and the lifetime of the proton. The committee recommends that DOE and NSF work together to plan for and to fund a new generation of experiments to achieve these goals. It further recommends that an underground laboratory with sufficient infrastructure and depth be built to house and operate the needed experiments.
Neutrino mass, new stable forms of matter, and the instability of the proton are all predictions of theories that unify the forces of nature. Fully addressing all three questions requires a laboratory that is well shielded from the cosmic-ray particles that constantly bombard the surface of Earth.
Use space to probe the basic laws of physics. The committee supports the Constellation-X and Laser Interferometer Space Antenna missions, which hold great promise for studying black holes and for testing Einstein’s theory in new regimes. The committee further recommends that the agencies proceed with an advanced technology program to develop instruments capable of detecting gravitational waves from the early universe.
The universe provides a laboratory for exploring the laws of physics in regimes that are beyond the reach of terrestrial laboratories. The NRC’s most recent astronomy decadal survey recommended the Constellation-X Observatory and the Laser Interferometer Space Antenna on the basis of their great potential for astronomical discovery. These missions will be able to uniquely test Einstein’s theory in regimes where gravity is very strong: near the event horizons of black holes and near the surfaces of neutron stars. For this reason, the committee adds its support for the recommendations of the astronomy decadal survey.
Determine the origin of the highest-energy gamma rays, neutrinos, and cosmic rays. The committee supports the broad approach already in place and recommends that the United States ensure the timely completion and operation of the Southern Auger array.
The highest-energy particles accessible to us are produced by natural accelerators throughout the universe and arrive on Earth as high-energy gamma rays, neutrinos, and cosmic rays. A full understanding of how these particles are produced and accelerated could shed light on the unification of nature’s forces. The Southern Auger array in Argentina is crucial to solving the mystery of the highest-energy cosmic rays.
Discern the physical principles that govern extreme astrophysical environments through the laboratory study of high-energy-density physics. The committee recommends that the agencies cooperate in bringing together the different scientific communities that can foster this rapidly developing field.
Unique laboratory facilities such as high-power lasers, high-energy accelerators, and plasma confinement devices can be used to explore physics in extreme environments as well as to simulate the conditions needed to understand some of the most interesting objects in the universe, including gamma-ray bursts. The field of high-energy-density physics is in its infancy, and to fulfill its potential, it must draw on expertise from astrophysics, laser physics, magnetic confinement and particle beam research, numerical simulation, and atomic physics.
Realize the scientific opportunities at the intersection of physics and astronomy. The committee recommends establishment of an interagency initiative on the physics of the universe, with the participation of DOE, NASA, and NSF. This initiative should provide structures for joint planning and mechanisms for joint implementation of cross-agency projects.
The scientific opportunities the committee identified cut across the disciplines of physics and astronomy as well as the boundaries of DOE, NASA, and NSF. No agency has complete ownership of the science. The unique capabilities of all three, as well as cooperation and coordination between them, will be required to realize these special opportunities.
The Committee on the Physics of the Universe believes that recent discoveries and technological developments make the time ripe to greatly advance our understanding of the origin and fate of the universe and of the laws that govern it. Its 11 questions convey the magnitude of the opportunity before us. The committee believes that implementing these seven recommendations will greatly advance our understanding of the universe and perhaps even our place within it. | 0.822753 | 4.053085 |
Apart from two wandering rovers, there's not much going on the martian surface these days. In fact, scientists believe the planet has been relatively dead for the past 3.5 billion years. But new research suggests that in at least one place, water gushed over Mars's surface less than 1 billion years ago. The finding increases the likelihood that life may have existed relatively recently there.
In 2004, the twin Mars rovers, Spirit and Opportunity, confirmed scientists' suspicions that water covered much of the martian surface from about 4.5 to 3.75 billion years ago, when it was a much warmer planet (ScienceNOW, 16 December 2004). After that time, Mars cooled down and dried up. Scientists have found evidence of flowing water, as revealed by gullies that formed over the past few million years (ScienceNOW, 22 June 2000), but the amount of water has been relatively small, and where the water came from is still unknown. Now researchers have evidence that rivers, tens of kilometers in length and about 250 meters across, carved valleys up to 20 meters deep across the martian landscape.
Planetary geologist Jay Dickson of Brown University and colleagues looked at a 7000-meter-deep depression in the martian surface known as the Lyot crater. Situated at about the same latitude as southern Canada in Mars's northern hemisphere, the crater contains buried glaciers and has a current average temperature of –16°C. But its location in the mid-latitudes could have seen temperatures up to 15°C during times when Mars was tilted more toward the sun than it is today, Dickson says. And because the crater is so deep, the atmospheric pressure is high enough to allow ice to melt, instead of turning into a vapor as it typically does over the rest of the planet.
Using high-resolution images from the Mars Reconnaissance Orbiter, a spacecraft that orbits the planet, Dickson's group zoomed in on the eastern half of the crater and discovered about 20 winding valleys and a number of deposited materials typically found at the end of rivers. Counting the number of impact craters on the surface (the older the surface, the more impact craters it will have), the researchers managed to date the surface to about 1 billion years old. That means that the rivers must have formed after this time, the team reports in the last issue of Geophysical Research Letters.
kewl. No time again. | 0.862424 | 3.70975 |
α Centauri B, a mere 4 lightyears away has a terrestrial planet orbiting it.
The most interesting aspect of the discovery may be the inferences we can make rather than the planet itself.
The discovery by the Geneva Observatory team using the
HARPS spectrograph is a wonderful example of precision high cadence spectroscopy and the ability of observers to find planets wherever they may be. The precision of the measurment is 0.5 m/sec, which is astonishing.
The discovery will be published in Nature (X. Dumusque et al. Nature 17 Oct 2012) thursday, and was due to be announced wednesday at 1 pm, but some idiot broke the embargo and ran the story early, so it is now coming out in pieces.
This particularly annoying, because I teach my exoplanets class at 1:25 wednesday and was planning to surprise them with a change of topic... bloomin' journalists!
The planet has a mass of at least 1.1 Earth masses, with the true mass being 1.1/sin(i) where i is the unknown inclination to the line of sight. It could plausible be as high as 6 earth masses, but is more likely to be in the 1-2 Earth mass range.
Its orbital period is 3.2 days, around the K1V secondary star of the Alpha Centauri system, the primary, α Cen A, being a G star slightly more massive than the Sun. The third star, Proxima Centauri, is a low mass M5 dwarf about 15,000 AU from the inner binary.
The system is a first magnitude star, the closest to the Sun, visible in the southern hemisphere.
At 0.04 AU circular orbital radius the planet has a mean temperature of about 1,200-1,500 K, and is almost certainly tidally locked, with one hemisphere facing the star.
The system is a triple, with α Cen B orbiting the primary with a semi-major axis of about 17 AU, orbiting every 80 years or so, and eccentricity of about 0.5
α Cen A is cannonballing to within 8 AU or α Cen B every century or so.
At closest approach the stars come as close as Saturn is from the Sun, and then recede to almost the distance Neptune is from the Sun.
That doesn't leave a lot of room for planets.
It is very impressive that there is one hiding in there.
Alpha Centauri has been a priority target for the HARPS team, and the competition from Debra Fischer at Yale has been doing high precision, high cadence observations of the system for several years, and we knew already that there were most certainly no giant planets or large ice giants like Neptune orbiting anywhere in the system.
The interesting thing is that the presence of the one planet cuddled up against its parent star is almost certainly the signpost for another planet or two further out, and since we haven't seen them yet, they must have comparable masses of Earth mass or few.
We don't think terrestrial planets can form this close to their parent stars. So something moved the planet from its birth location further out.
It is possible α Cen A pushed it in, through the Kozai Mechanism, but only if the planet's orbit is highly inclined to that of the star, which is somewhat unlikely. It is more likely the orbits are near coplanar (which incidentally implies the planets true mass is near its observed minimum mass).
It take a planet to move a planet.
As a toy scenario, imagine the planet formed a respectable 0.2 AU from α Cen B. A kick up to an eccentricity of 0.9 or so would lead to the planet circularizing to its current orbit.
But, to provide the kick there must have been at least one other comparable mass planet in the system. Two others would be better, at orbital radii in the range 0.25 - 2 AU or so.
It is not unlikely the other planet or planets are still there. They could have been kicked out far enough for α Cen A to knock them out of the system, but that is not very likely.
So there may well be a 1-3 Earth mass planet with a semi-major axis of about 1 AU, and eccentricity of maybe 0.8 or so in the system.
Or two planets, with moderate eccentricities.
Further, if there was a protoplanetary disk around α Cen B which lasted long enough to make terrestrial planets, it seems very likely there was also a disk around α Cen A, and it too must have made terrestrial planets, safely inside 2 AU, but maybe none kicked in as close as the one we just detected.
There are almost certainly several more planets to be discovered there, around both α Cen B and α Cen A!
In principle they may include Earth mass planets orbiting close to the habitable zone of either planet, though at least for α Cen B any planet there is likely to in an uncomfortably eccentric orbit.
This is quite wonderful! And, frankly, kind of unexpected to me -- I'd always thought that the science-fiction scenarios of an Earth-like planet at Alpha Centauri to be exceedingly optimistic simply on the basis that it's our nearest neighbor.
As you say, this one isn't habitable but it indicates a realistic possibility of one that is. I still can't really imagine anything so fortunate for us, but then this sort of underscores how far we've come from the days when almost everyone assumed that small, rocky planets were rare, those in the habitable zone even more so, and therefore anything at all like a terrestrial planet with life was so improbable as to be absurd. We don't live in those times anymore. I recall when the very idea of any kind of extraterrestrial life, anywhere, was thought to be self-evidently nuts. Things have changed so much and sometimes I find myself amazed by it.
So, well, it might be the case that terrestrial-massed planets in the habitable zone could be common, rather than rare. If there is one at Alpha Centauri, then that's a strong indication that this is the case. But then, we were being rather anthropocentrically exceptionalist in assuming that local conditions were nearly unique and not common.
I read the paper last night and I'm impressed by the number of corrections and adjustments applied to the RV data before the planetary signal is extracted. I see that there is still quite a bit of scatter in the RV measurements which remain.
Although it would be a nice story to find such a small planet around one of the components of alpha Cen, I'm not convinced that the planet is really there. Would you be willing to wager a bottle of your favorite beverage on its existence?
I am told the outer limit for a stable orbit around either star is about 1 AU, but during the brief formation period a circumstellar disc may have extended further out. Even so, if this is one of several planets they have probably *all* spiralled close to the star, leaving the outermost close enough to be fried.
Never mind, any expedition out there will be made by AIs and robots, and they may be comfortable in the extreme cold of the planet's permanent night zone, providing superconductivity at ambient gtemperatures.
So for a star-faring supercivilisation that has left the wet gunk substrate behind, this tidally locked world is actually better than Earth. | 0.84953 | 3.577575 |
This Week’s OOTW features Budgieye’s OOTD posted on the 1st of April 2011.
These two objects, called CFBDSIR J1458+101 A and B, lurk 75 light years away in the constellation Bootes just below Arcturus; a star marking one of the constellation’s knee. Both objects – called Brown Dwarfs – are locked in orbit with each other, with the distance between them about 2.6 AU or 388, 954, 800 Kilometres.
Brown Dwarfs are often known as ‘failed stars’. They’re objects not much bigger than a gas giant, with the smaller dwarfs weighing in at 13 times the mass of Jupiter and the largest just below 0.08 solar masses; the mass of the smallest main sequence stars. They aren’t planets however, as, unlike planets, they form just like any other star – out of the interstellar medium, but because of their low mass they can never undergo any sustainable fusion.
The object of interest in Budgie’s OOTD is the dimmest object of the pair. With a meagre temperature of 370 K (about 96 Centigrade) it’s as hot as a fresh cup of tea, making it the coolest brown dwarf on record!
The paper on the discovery of this dwarf is here.
This week’s OOTW features an OOTD posted by Lightbulb500 on the 22nd of February 2011.
In the words of Lightbulb:
The galaxies are located around 60 megaparsecs from Earth (or 196 million light years).
Both were once normal spiral galaxies, but are now in the midst of a high speed collision that has already stripped them of most of their hydrogen gas.
The pair will likely merge together at some point in the future.
What earns this pair their ‘Taffy’ designation is quite unusual. There is a bridge of hydrogen gas linking the two galaxies that is emitting large quantities of radio waves and is also producing at least a few stars. It is the presence of this intergalatic gas bridge that makes these Taffy galaxies.
While searching around for info I came across an interesting paper on this galaxy pair by J Braine et al (PDF here); it’s well worth a read. According to the paper, the galaxies collided more or less head on 20 million years ago, creating that widening bridge composed of anything between 2-9 x 10^9 solar masses of interstellar gas! The green tint in between the galaxies would be from H-alpha emissions, showing where the bridge is churning out newborn stars, or, where the collision sent out shockwaves, ionizing parts of the bridge.
This week’s OOTW features an OOTD by Alice, which was posted on the 27th of January 2011.
Today’s OOTW is a lovely silly one; here’s a screenshot:
Most of the images came from the pure art thread, a place full of fun pictures made from images from the SDSS!
Alice also mentioned a survey of our experiences on the Zooniverse for us all to do. It’s a citizen science research project by Peter Darch! There’s more info here 🙂
And also a congratulations to Half65, who through his work in the overlapping galaxies project is now a co-author of a galaxy zoo paper!
This week’s OOTW features an OOTD by Jules, posted on the 7th of January 2011.
Jules, at the end of 2009, had the idea of an ‘Astrophotography 365’ challenge, where at least one astronomically themed image gets posted on the Galaxy Zoo forum each day in 2010. And it went down extremely well, with just over a thousand images posted!
In the words of Jules:
The level of interest in the thread was unexpected and the contributions came thick and fast. On cloudy nights we had photos of astronomy themed gadgets, toys, books and jewellery! There were several photos posted for each day and the project grew bigger than I had anticipated. I had originally intended to put all the photos into a montage at the end of the year but we had so many contributions that I opted for monthly montages instead in order to make the final one manageable.
The 365 is now complete. We more than met the challenge and here is the result:
We had pictures of deep sky treasures such as star clusters, nebulae and galaxies as well as comets stars, planets and the Sun (including its spectrum) and the Moon. Equipment ranged from mobile phones to DSLRs and webcams to remotely controlled scopes like SLOOH and SARA-S. Some contributors had never taken an astrophoto before and produced some amazing results. We also braved all weathers to meet the challenge. I hope we kept people entertained – the thread has had over 42,000 views.
Thanks to everyone who took part. It was huge fun. Maybe we can have a year off and do it all over again! Meanwhile let’s resurrect Alexandre’s old thread and keep clicking in 2011!
This week’s OOTW features Alice’s OOTD posted on the 30th of December 2010.
Lenticular galaxies are a bit like spiral galaxies in the fact that the main part of the galaxy is a flattened disk of stars, but like an elliptical galaxy they have no arms. The star forming material in lenticulars is mostly used up, so these galaxies mostly consist of old stars rather than new ones.
NGC 5866, unlike most of the galaxies that share its morphology, has a dust line stretching through its galactic plane – its disk – and as the dust lane is perfect for churning out stars, it has a string of hot, young, blue stars accompanying it.
Happy New year! 🙂
This week’s OOTW features my OOTD ‘A Dark Secret in Virgo‘ posted on the 11th of December 2010.
On the 17th of March 1781, Pierre Méchain discovered this beautiful galaxy. NGC4254 lurks 50 million light years away in the constellation Coma Berenices. It’s a disturbed spiral, with its right arm jutting out further than the other. So what’s caused this? Let’s zoom out…
Is it a black hole? No. Is it a gigantic cloaked alien ship that tugs galaxies?! Nope. It is in fact VIRGOHI21; a HI region 50 million light years away that was first detected by the Lovell telescope. A HI region is a mass of neutral hydrogen, and in this case it has hardly any or no stars. But there’s something more to this object than meets the eye…
This is a screenshot of an animation (my attempts at posting the animation here failed!) which shows a map of VIRGOHI21. According to this website here the larger brighter mass is NGC 4254, and you can see the cloud is cascading down from the disturbed spiral arm in a stream of neutral hydrogen to the centre of the image. Astronomers have calculated that the total mass of this HI region is 2×10^8 Mʘ (solar masses), but the velocity and spin of this object indicates that there is more mass than we can detect and so the object actually has a mass of 10^11 Mʘ! So where does the rest of the mass come from…?
Dark matter! It is currently thought that VIRGOHI21 is a dark galaxy, which is a starless galaxy made up of mostly dark matter with little else apart from dust and hydrogen. This dark galaxy is interacting with NGC 4254 like any other normal galaxy would!
VIRGOHI21 is currently the best dark galaxy candidate out there, but others include HE0450-2958 which is a quasar that appears to be galaxy-less! Usually quasars have a host galaxy, but this one doesn’t appear to have one that we can see, so it has been proposed that the Quasar is actually part of a dark galaxy.
A survey called AGES uses the Arecibo observatory to find HI regions that are in connection with dark galaxies: http://www.naic.edu/~ages/
This week’s OOTW features Lightbulb500’s OOTD posted on the 4th of December 2010.
This star, with a mass of around half of that of our own star and a temperature many degrees cooler; is a red dwarf. They are the most common stars in the universe, 85% of our galaxy’s stellar population is composed of red dwarfs and it was thought that there was 1×10^23 (or 100 sextillion) in the universe. They are also the longest lived with a lifespan of up to ten trillion years!
The number of red dwarfs in the universe has been recently changed to a much higher number, as Lightbulb500 writes:
[…] New data that confirms the presence of red dwarfs in eight elliptical galaxies between 50,000 and 3 million light years distant. As well as confirming their presence the number of red dwarfs per galaxy has been calculated and reveals that these elliptical galaxies contain 20 times the number of red dwarfs as the Milky Way!
Such a large jump in the number of red dwarfs in elliptical galaxies has necessitated a ‘slight’ revision to the number of stars inhabiting our universe.
The figure has been revised from 100 sextillion or (if I may have an infant moment) 100,000,000,000,000,000,000,000, or 1×10^23 if you like standard form to 300 sextillion – It has been tripled!
Such an increase has other knock on effects – more stars means more ‘normal’ matter so the universe would ‘need’ less dark matter to ‘work’.
It could also have an effect on how dark matter is concentrated around galaxies.
This week’s OOTW features Alice’s OOTD posted on the 25th of November 2010.
This beauty is NGC 3169. It’s a spiral galaxy 55.3 million light years away in the constellation Sextans. It’s part of a group of two other spiral galaxies: NGC 3166 and NGC 3165. The nearest galaxy to it – NGC 3166 – is tugging at it, causing its spiral arms to distort.
NGC 3169 also happens to be a nomination for this:
“Today’s Object of the Day is not an object, but a request for some. Zookeeper Rob is looking for an “Object of the Day” for a Zoo Advent Calendar, which should be interesting (open up this pocket of space and – oops, a black hole! ). Want to help?
From now until Monday, please post your favourite galaxy, either from Hubble Zoo or from SDSS. On Monday we will have a poll, closing on Tuesday night.”
(Post the galaxies in Alice’s OOTD)
Also, Happy Birthday Zookeeper Chris!
This OOTW features Budgieye’s OOTD posted on the 18th of November 2010.
This is NGC 7252, or the Atoms-For-Peace galaxy. This beautiful merger lurks in the constellation Aquarius 220 million light years away. It’s a beautiful example of a galaxy interacting with another, with both galaxies twisting round each other as they are caught up in each others gravitational pull. As this happens over a course of millions and billions of years tidal tails are thrown out, creating streamers of stars stretching for thousands of light years. As well as beautiful streamers the collision has created hundreds of new stars from the disruption, and many new star clusters only 50-500 million years old are now spread out across the galaxy.
And what of the name?
The galaxy – which looks rather like a diagram of an atom – was named after a lecture called Atoms for Peace, which was given by the US president Dwight D. Eisenhower in 1953. In his lecture, he called for nuclear power to be used for peaceful rather than destructive purposes.
There’s more info on the galaxy at ESO!
This week’s OOTW features Jean Tate’s OOTD posted on the 10th of November 2010.
On the 27th of November 1880, the Mathematician and astronomer Truman Henry Stafford discovered this beautiful spiral galaxy:
It lies 151 million light years away in the constellation Cetus. It’s a spiral galaxy with its arms tightly wound so that they complete the rings you see above making it a ringed galaxy, rather than being a ring galaxy where another smaller galaxy passes through the centre, creating a ring of star formation surrounding a core much like the famous Hoag’s Object shown below.
I love the contrast between the red inner rings of older stars and the outer ring bubbling with new stars!
More information on Truman Henry Stafford here! | 0.804985 | 3.746015 |
Most of our satellites orbit the Earth – either in Low Earth Orbit, LEO, Medium Earth Orbit, or in Geostationary Orbit, GEO. The closer to the Earth a satellite is the shorter its period. So – What if the satellite is even further away than the geostationary satellites? Why would you place satellites that far from the Earth?
There are satellites that aren’t orbiting the Earth, not exactly the Sun either. They are rotating with the system in points called Lagrangian points, after the Italian/French mathematician, Joseph-Louis Lagrange, 1736-1813. Where ever you find two bodies in space, where a smaller body is orbiting the larger one, you’ll find these five points. You find them in the Earth-Moon-system as well as in the Sun-Earth-system. Here we’ll concentrate on the Sun-Earth-system.
Lagrangian points 1 – 3 lies in a straight line with the Sun and the Earth. L1 is between the Earth and the Sun. If you do the math you’ll find that the point where the Sun’s gravitation equals the Earth’s would be just over a quarter of a million kilometers from the Earth’s center. That if the system wasn’t rotating. But now it is. The Earth’s orbital speed is about 29800km/s which means we have to calculate with a certain inertia. In L1, if the satellites would keep the same orbital speed as the Earth, they would normally start a spiral formed journey to the Sun. Speeding up would mean that the inertia kept the satellites in steady orbit, but they would, of course, leave the Earth behind. Though including the Earths gravity to the equation L1 becomes quite stable at its distance about 1/100 of the Sun-Earth distance away from the Earth.
In L2, on the far side of the Earth, seen from the Sun, without the gravity of both the Sun and the Earth satellites would have a lower orbital speed and would be left behind. See animations here.
L3 is difficult to use due to the difficulties in communicating with satellites on the other side of the Sun. L4 and L5 would be excellent due to their stability. Place a satellite there and it would be like placing a cueball in a bath tube. It wouldn’t leave. Unfortunately, the same thing goes for dust, and small rocks in space. Satellites wouldn’t stay clean, nor safe. Lagrangian points four and five in the Sun-Jupiter-system exemplifies the problem.
L1 is an excellent place when it comes to monitoring the Sun and the solar wind. SOHO, Solar and Heliospheric Observatory, ACE, Advanced Composition Explorer, and DISCOVR, Deep Space Climate Observatory, are satellites orbiting L1. Far from the Eart’s heat radiation, and at the night side of the planet, L2 is a good home to satellites looking out into deep space. Here you find Herschel, Planck, and GAIA.
The Lagrangian points are still more than viewpoints. December 3d, 2015 the LISA Pathfinder is been launched from Europe’s spaceport in Kourou to reach L1 in late January 2016. It’s delicate mission is to test the technology for measuring gravitational waves. L1 is a balanced choice.
Now read this: About orbits
Jan teaches mathematics and interdisciplinary science to pupils 13-16 years of age at Sursik School, Pedersöre, Finland. Space-related science often gives some sort of answer to the question “Why?”, a question quite common in math class. It also triggers curiosity, one key component in progress. | 0.848083 | 3.672881 |
- Published on 30 November -0001
In section 10. Planets and planetary systems
The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present
The habitability of Proxima Centauri b. II. Possible climates and Observability
The discovery of a planet orbiting around Proxima Centauri, our closest neighbor, is in itself a significant breakthrough. The fact that the planet has a minimum mass of only 1.3 times that of our Earth and is at approximately the right distance from its star for water to be liquid at the surface makes it even more special. In two papers, Ribas et al. and Turbet et al. examine the conditions for so-called “habitability" of this planet: could liquid water be present on its surface?
In the first paper, Ribas et al. show that the planet, Proxima b, should be either synchronously rotating, or in a 3:2 resonance between its spin and orbit as Mercury is. They also show that it should have lost less than an Earth's ocean worth of hydrogen by atmospheric escape: Thus, depending on the initial water content of the planet, it may still possess water on its surface.
In the second paper, Turbet et al. use a 3D global climate model to simulate Proxima’s b climate and water cycle. They find that a broad range of compositions allow surface liquid water, and they present reflection and emission spectra, and phase curves for the simulated climates. The observation of thermal phase curves can be attempted with JWST. They conclude that within a decade we should know whether Proxima is indeed habitable. | 0.853859 | 3.552292 |
For thousands of years, people have been puzzling over the milky strip that extends across the entire firmament. In the modern era, Galileo Galilei discovered that this Milky Way consists of countless stars. However, it was not until the 20th century that astronomers succeeded in deciphering its form and its true nature.
“My third observation relates to the nature of the Milky Way (…) No matter which part of it one targets with the telescope, one finds a huge number of stars, several of which are quite large and very striking; yet, the number of small stars is absolutely unfathomable.”
These words were written in 1610 by a man who with his self-constructed telescope studied unknown lands that were not of this world. It was this work that earned him a place in history: Galileo Galilei.
The land that he described is literally out of this world, and the document bears the title Sidereus Nuncius (“Starry Messenger”). In it, the Italian mathematician and astronomer presents his observations of the satellites of Jupiter, the Earth’s moon, and also the Milky Way. Until then, their nature had remained a mystery and had above all been the subject of mythology.
The Greek natural philosopher Democritus had already claimed in the 5th century B.C. that the diffusely glowing strip in the sky — known by the African !Kung bushmen as the “backbone of the night” — consisted of countless weak stars.
Grindstone in the firmament
After the discovery made by Galilei, however, nearly 150 years would pass before this celestial structure would again become the subject of scientific study. Thomas Wright of County Durham believed that stars were arranged in a flat region similar to a grindstone, which extended over the entire sky. For him, the Milky Way was nothing other than the projection of this grindstone.
The German philosopher Immanuel Kant seized on this theory — and came very close to discovering the truth. In his General Natural History and Theory of the Heavens, published in 1755, he explained the Milky Way as an extended and very diluted layer of stars. The Sun, the Earth, and all the other planets were part of this layer — but not at its center.
Depending on the line of sight, along the plane of the layer or vertically out of it, we would see different numbers of stars. But how were the astronomers to find out whether the apparent view of the Milky Way in the sky reflected its actual spatial structure? Stellar statistics devised at the end of the 18th century by Friedrich Wilhelm Herschel promised a solution: Herschel recorded the coordinates and brightness of all the stars that he could see through his telescope.
However, the undertaking failed. Apart from the unreliability of these measurements — for example, although it was possible to determine the apparent brightness of the stars, it was impossible to determine their absolute luminosity and hence their distance — there was also a fundamental problem: The Milky Way is filled with interstellar matter, gas, and dust clouds that absorb light from the stars.
This obscures the view of the central region and makes it impossible to see the overarching structure. For this reason, stellar statistics can never encompass the system as a whole, but only the region around the Sun up to a radius of about 10,000 light-years. The breakthrough did not come until the middle of the 20th century, when astronomers learned to look at the sky with different eyes using radio telescopes.
A look through curtains of dust
Hydrogen is the most common element in the universe. As part of interstellar matter, neutral hydrogen (H1) fills the space between the stars, and thus also fills the Milky Way. This means that the distribution of clouds of hydrogen gas trace the shape of the whole system, similar to the way in which bones shape the human body.
But how can these cosmic “bones” be made visible? The answer is provided by the nano universe: In the ground state of hydrogen, the direction of spin of the atomic nucleus and the electron that orbits around it are antiparallel. If two hydrogen atoms collide, the direction of spin of the nucleus and the electron may be flipped to end up parallel to each other — and after a certain time, they return to their basic antiparallel state.
This process releases energy, which is radiated as an electromagnetic wave. This line lies in the radio range of the electromagnetic spectrum. Despite the extremely low density of interstellar matter, atoms are constantly colliding, causing the H1 areas to glow in the light of this hydrogen line.
This radiation penetrates the dust curtains almost unobstructed and can be picked up by radio telescopes. Thanks to this new window into the universe, astronomers have been able to discover the spiral structure of the Milky Way. However, in the 1970s, researchers found that hydrogen alone was not sufficient as an indicator of the galaxy’s morphology because, for example, it is less concentrated in the spiral arms than expected. The search began anew.
Arms in motion
The most important indicator turned out to be clouds of interstellar molecules — they emit radiation in the light of carbon monoxide (CO). Now, it was gradually becoming possible to refine the portrait of the Milky Way. Accordingly, the galaxy (from the Greek word gala: milk) is a bent wheel, 100,000 light-years in diameter and with a thickness of just 5,000 light-years.
The wheel hub with its black hole is surrounded by a spherical bulge of stars with an embedded cigar-shaped structure – a kind of bar. Around 15,000 light years from the center, a ring extends that also consists of dust and gas clouds, as well as stars.
The galaxy is characterized by several arms. Most of them bear the names of the stellar constellations in which we observe them: the Sagittarius and Perseus Arms, the Norma and Scutum-Crux Arms, the 3-Kiloparsec Arms, and the Cygnus Arm.
Our solar system is located in the Orion Arm, 26,000 light-years from the center and almost on the main plane. The system, which contains around 200 billion suns, is surrounded by a spherical halo containing thousands of globular star clusters and a spherical region consisting of very thin hydrogen plasma.
The entire galaxy rotates, with objects closer to the center rotating faster, and those further from the center rotating more slowly. The curve of this differential rotation shows irregularities that cannot be explained by visible mass alone.
Here, it is likely that invisible dark matter plays a role. And the astronomers face yet another problem: Despite the rotation, the spiral arms do not unwind, but have maintained their shape for billions of years. One explanation for this is shockwaves that propagate throughout the whole system and compact the matter in the spiral arms like a traffic jam on the motorway. Researchers are still puzzling over what causes these density waves.
Provided by: Max Planck Society [Note: Materials may be edited for content and length.]
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Phobos, the largest — yet at just 16 miles wide still quite tiny — moon of Mars is getting ripped apart by the gravitational pull of its parent planet… and it bears the scars to show it, scientists have determined.
Long parallel grooves that wrap around the surface of Phobos are thought to be stress fractures — surface evidence of the tidal forces that will one day cause the moon to break apart entirely. This fate is not surprising to scientists, but that we’re seeing it in action is fascinating.
“We think that Phobos has already started to fail, and the first sign of this failure is the production of these grooves,” said Terry Hurford of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
As a planetary satellite Phobos really is an oddity. Besides its small size and irregular shape, it also orbits Mars at an extremely low altitude — only 3,721 miles (compare that to our own Moon’s 248,000-mile distance.) It thus needs to travel at a very high speed just to stay in orbit. It is actually traveling around Mars three times faster than Mars rotates (about 2,237 mph) and so Phobos rises in Mars’ western sky (but isn’t even visible from high-latitude polar regions.)
Even at that speed, though, Phobos can’t maintain its altitude. Every hundred years or so it falls 6.6 feet closer to Mars. After another 30 to 50 million years it will reach its Roche limit and, unable to support its structure under an uneven pull of gravity across its form, will completely crumble apart over Mars.
This scenario was actually first hypothesized after the Viking 1 orbiter imaged Phobos in June 1977, but at the time it was thought that the interior of the moon was fairly solid. Now, with more data in hand about Phobos’ composition and density, it’s thought to be more of a loose rubble pile with an elastic outer “skin” of powdery material…which allows Phobos to stretch but will ultimately lead to its structural collapse. | 0.884532 | 3.69175 |
Maven: a probe to discover the secrets of Mars’ atmosphere
Launched November 18th will tell us why the red planet has become barren and dry, and if a time it was really a living planet.
What happened to the atmosphere of Mars? There was a time, between three and four billion years ago, when the red planet was shrouded by clouds and dense gas as terrestrial ones, which allowed water to flow over its surface in large rivers and streams. Then something changed: the air has become more and more rarefied, to prevent water to exist in liquid form, thus turning the red planet, potential twin of Earth, in the cold and desolate expanse of rocks and stones we see today thanks to the images sent by the Rover.
To find out how this happened and why, was launched from Cape Canaveral on Monday the probe MAVEN, which stands for Mars Atmosphere and Volatile Evolution. The name already reveals its objectives: to determine the loss of volatile elements in the Martian atmosphere over time and to estimate the current rate of escape of molecules in space.
An hour after launch, just split off from the Atlas V rocket that brought in space, the spacecraft deployed its solar panels and is now on its way to Mars, which will reach in ten months in September 2014, going to support the already large fleet of satellites that are orbiting (in October India has also launched its own probe). Then it’s inserted into the upper atmosphere of the planet in order to study the phenomenology thanks to sophisticated electronic equipment.
Although composed almost entirely of carbon dioxide, the atmosphere is so tenuous that does not allow greenhouse gases (though probably present in the distant past) making the Martian climate to be hostile to life (barely reach the maximum and minimum spring temperatures are under one hundred degrees). The lack of ozone cannot offer protection from cosmic rays, sterilizing everything to the ground. Furthermore, the pressure is about sixty times lower than on land, so the water can remain only in the form of ice (the poles) or liquid, but in the bowels of the underground.
All conditions to study and understand well, in view of a future human mission, are scheduled for 2030 on paper. Meanwhile, MAVEN, which will remain in orbit until 2016, will collect data on the properties of the ionosphere, the composition of the gas, its magnetic field, the composition of the solar wind particles and their interactions with the weather.
Yeah, because scientists have any idea if they are made: between the various theoretical models developed, there is also what he sees as the solar radiation responsible for the loss of atmosphere (as shown in this video). Over millions of years, super photon energy emitted from the Sun would have ionized the atmospheric molecules, creating free electrons. These particles collide with the gas; they would split the bonds and provided enough energy to shoot it into deep space. If things went really well, MAVEN will confirm this in under a year. | 0.857783 | 3.92734 |
A 4.6 billion-year-old meteorite landed in Algeria in 1990, the remnant of a larger asteroid born during the dawn of our solar system.
New analysis of the meteorite, called Acfer 049, has revealed ice fossils trapped inside, making it the first direct evidence of frozen water as a building block of early asteroids.
Given the meteorite's age, it also preserves material that created our solar system, providing a unique look at our corner of the universe and how it formed.
The new findings published this month in the journal Science Advances.
Scientists know that it was possible for asteroids to include ice as an ingredient in their structure, mainly due to the way water altered minerals in the asteroids.
But they wanted to understand more about the amount of water, its distribution throughout the asteroid structure, called a matrix, and when it melted.
Acfer 049 preserved tiny pockets that once contained the ice before it melted and researchers call these microscopic holes ice fossils.Like other solar systems, ours began with the formation of a star.
The sun formed from a cloud of dust and gas and the leftover materials not used to create the star became the ingredients for the planets in our solar system.
Then gas and elements formed into a flat planetary disk around the sun and that included hydrogen, ice, iron and silicates.
Over time, the dust and elements stuck together, forming planets and other bodies, including asteroids.
This is why asteroids and comets are considered to be the leftovers of material that formed the solar system.Ice, which could be found beyond the snow line of the planetary disk where solid water ice can form, was also included in the mix.
The snow line existed in the disk at a distance from the star where its heat couldn't maintain liquid water.
"This is starting material from which all the planets, including Earth, came from," said Epifanio Vaccaro, study author and Curator of Petrology at London's Natural History Museum.
"The matrix of these meteorites is therefore thought to be the starting material from which all the planets formed."
The rocky bits of dust and ice that became asteroids retained a pristine record of the ingredients that created them.
But the planets formed by rearranging their ingredients through heat -- metals melted to form the core while silicates created a mantle and crust.
This means that rocks found on Earth are quite different than the material found in asteroids.
"When this happens, all the starting material that we had in the protoplanetary disk is gone as it went through the process of melting and recrystallisation," Epifanio said.
"This means that if we want to understand what the dust was like as the solar system formed, we need to go back and grab some of the material that didn't go through this differentiation process. In some meteorites, we have that starting material preserved."
While dust and ice doesn't sound like the solid foundation for a rocky asteroid, its matrix is tightly constructed because of how its materials came together.
"The matrix itself is very fine-grained material that holds everything in the meteorite together," Epifanio said.
But the matrix itself made the meteorite difficult to study because they didn't have the technology to peer through the fine grains until now.
The researchers used microscopes with high spatial resolution, which allowed them to finally see the tiny pockets that once contained ice.
These microscopes could be used to look at other meteorites and possibly find more evidence of ice fossils, the researchers said.
"Based on this finding of asteroidial ice, we made a model that tells us how the asteroid grew and how the planets formed," Epifanio said.
"We think that fluffy ice and dust particles came together into bigger bodies beyond the snow line, and then migrated inwards. As they did so, the ice started melting, leaving the fossils in its place." | 0.873492 | 4.033263 |
Anunexpected and powerful new kind of star explosion has been discoveredin theheavens ? a so-called gamma-ray nova that radiates the most energeticform oflight in the universe.
Anova is a massive thermonuclear explosion from a whitedwarf star fueled by mass from a companion star. Unlike supernovas,novasdo not result in the destruction of their stars. Researchers hadexpected andseen X-rays from the resulting waves of expanding gas in prior novas.Butunlike with supernovas, they had not seen gamma-rays emitted by novas.
Nowresearchers have discovered a nova that shed gamma rays, which are evenmore powerfulthan X-rays, by using the Fermi Large Area Telescope in orbit aroundthe Earth,the most sensitive gamma-ray space telescope ever flown. [Photoof thegamma-ray nova.]
"Thisis the first gamma-ray nova seen," said researcher Teddy Cheung, anastrophysicist at the Naval Research Laboratory in Washington.
Thegamma rays in question emerged from the binary system known as V407Cygni some8,800 light-years away, which consists of a white dwarf and a pulsatingredgiant star. They came after a nova spotted by amateurJapanese astronomersin March, which at its peak was just below the level of naked-eyevisibility,brighter than at any other point in the nearly 75 years scientists hadwatchedthe system.
Theresearchers suggest the gamma rays were generated when the blast wavesfrom thenova collided with the very dense winds from the red giant.
"Asthe blast wave propagates outward, it acts like a snowplow, sweeping upmaterial from the stellar wind, and a shock front forms," explainedresearcherAdam Hill, an astrophysicist at the University of JosephFourier-Grenoble inFrance.
Protonsand electrons get accelerated to very high energies at this shockfront. Inturn, they produce gamma rays.
Inmany novas, the white dwarf's companion is a normal main sequence star,and assuch has a much less dense stellar wind compared to the red giant inV407Cygni, for less material to generate gamma rays with. Very few binarysystemsare expected to combine the kind of whitedwarf stars that burst with novas with red giant companions,and as suchthe researchers expect gamma-ray novae to be quite rare.
"Itis always exciting to discover something new and unanticipated," Hillsaid. "It is occasions such as this which is why I enjoy being ascientist."
Theresearchers at the Fermi-LAT Collaboration detailed their findings intheAugust 13 issue of the journal Science.
- Top10 Star Mysteries
- TheStrangest Things in Space
- AstronomersHunt for Ticking Time Bombs | 0.878357 | 3.995286 |
Earth's volcanoes occur because its crust is broken into 17 major, rigid tectonic plates that float on a hotter, softer layer in its mantle. Therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging, and most are found underwater. For example, a mid-oceanic ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, e.g., in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "plate hypothesis" volcanism. Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core–mantle boundary, 3,000 km deep in the Earth. Volcanoes are usually not created where two tectonic plates slide past one another.
Large eruptions can affect ambient temperature as ash and droplets of sulfuric acid obscure the sun and cool the Earth's troposphere; historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines.
The word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology. The study of volcanoes is called volcanology, sometimes spelled vulcanology.
Divergent plate boundaries
At the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock. Because the crust is very thin at these ridges due to the pull of the tectonic plates, the release of pressure leads to adiabatic expansion (without transfer of heat or matter) and the partial melting of the mantle, causing volcanism and creating new oceanic crust. Most divergent plate boundaries are at the bottom of the oceans; therefore, most volcanic activity on the Earth is submarine, forming new seafloor. Black smokers (also known as deep sea vents) are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed; for example, Iceland.
Convergent plate boundaries
Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the oceanic plate subducts, or submerges, under the continental plate, forming a deep ocean trench just offshore. In a process called flux melting, water released from the subducting plate lowers the melting temperature of the overlying mantle wedge, thus creating magma. This magma tends to be extremely viscous because of its high silica content, so it often does not attain the surface but cools and solidifies at depth. When it does reach the surface, however, a volcano is formed. Typical examples are Mount Etna and the volcanoes in the Pacific Ring of Fire.
Hotspots are volcanic areas believed to be formed by mantle plumes, which are hypothesized to be columns of hot material rising from the core-mantle boundary in a fixed space that causes large-volume melting. Because tectonic plates move across them, each volcano becomes dormant and is eventually re-formed as the plate advances over the postulated plume. The Hawaiian Islands are said to have been formed in such a manner; so has the Snake River Plain, with the Yellowstone Caldera being the part of the North American plate above the hot spot. This theory, however, has been doubted.
The most common perception of a volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit; however, this describes just one of the many types of volcano. The features of volcanoes are much more complicated and their structure and behavior depends on a number of factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have landscape features such as massive plateaus. Vents that issue volcanic material (including lava and ash) and gases (mainly steam and magmatic gases) can develop anywhere on the landform and may give rise to smaller cones such as Puʻu ʻŌʻō on a flank of Hawaii's Kīlauea. Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter, Saturn, and Neptune; and mud volcanoes, which are formations often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes except when the mud volcano is actually a vent of an igneous volcano.
Volcanic fissure vents are flat, linear fractures through which lava emerges.
Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically. Since low-viscosity magma is typically low in silica, shield volcanoes are more common in oceanic than continental settings. The Hawaiian volcanic chain is a series of shield cones, and they are common in Iceland, as well.
Lava domes are built by slow eruptions of highly viscous lava. They are sometimes formed within the crater of a previous volcanic eruption, as in the case of Mount Saint Helens, but can also form independently, as in the case of Lassen Peak. Like stratovolcanoes, they can produce violent, explosive eruptions, but their lava generally does not flow far from the originating vent.
Cryptodomes are formed when viscous lava is forced upward causing the surface to bulge. The 1980 eruption of Mount St. Helens was an example; lava beneath the surface of the mountain created an upward bulge which slid down the north side of the mountain.
Volcanic cones (cinder cones)
Volcanic cones or cinder cones result from eruptions of mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 meters high. Most cinder cones erupt only once. Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Parícutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. In New Mexico, Caja del Rio is a volcanic field of over 60 cinder cones.
Stratovolcanoes (composite volcanoes)
Stratovolcanoes or composite volcanoes are tall conical mountains composed of lava flows and other ejecta in alternate layers, the strata that gives rise to the name. Stratovolcanoes are also known as composite volcanoes because they are created from multiple structures during different kinds of eruptions. Strato/composite volcanoes are made of cinders, ash, and lava. Cinders and ash pile on top of each other, lava flows on top of the ash, where it cools and hardens, and then the process repeats. Classic examples include Mount Fuji in Japan, Mayon Volcano in the Philippines, and Mount Vesuvius and Stromboli in Italy.
Throughout recorded history, ash produced by the explosive eruption of stratovolcanoes has posed the greatest volcanic hazard to civilizations. Not only do stratovolcanoes have greater pressure buildup from the underlying lava flow than shield volcanoes, but their fissure vents and monogenetic volcanic fields (volcanic cones) also have more powerful eruptions because they are often under extension. They are also steeper than shield volcanoes, with slopes of 30–35° compared to slopes of generally 5–10°, and their loose tephra are material for dangerous lahars. Large pieces of tephra are called volcanic bombs. Big bombs can measure more than 4 feet(1.2 meters) across and weigh several tons.
A supervolcano usually has a large caldera and can produce devastation on an enormous, sometimes continental, scale. Such volcanoes are able to severely cool global temperatures for many years after the eruption due to the huge volumes of sulfur and ash released into the atmosphere. They are the most dangerous type of volcano. Examples include Yellowstone Caldera in Yellowstone National Park and Valles Caldera in New Mexico (both western United States); Lake Taupo in New Zealand; Lake Toba in Sumatra, Indonesia; and Ngorongoro Crater in Tanzania. Because of the enormous area they may cover, supervolcanoes are hard to identify centuries after an eruption. Similarly, large igneous provinces are also considered supervolcanoes because of the vast amount of basalt lava erupted (even though the lava flow is non-explosive).
Submarine volcanoes are common features of the ocean floor. In shallow water, active volcanoes disclose their presence by blasting steam and rocky debris high above the ocean's surface. In the ocean's deep, the tremendous weight of the water above prevents the explosive release of steam and gases; however, they can be detected by hydrophones and discoloration of water because of volcanic gases. Pillow lava is a common eruptive product of submarine volcanoes and is characterized by thick sequences of discontinuous pillow-shaped masses which form under water. Even large submarine eruptions may not disturb the ocean surface due to the rapid cooling effect and increased buoyancy of water (as compared to air) which often causes volcanic vents to form steep pillars on the ocean floor. Hydrothermal vents are common near these volcanoes, and some support peculiar ecosystems based on dissolved minerals. Over time, the formations created by submarine volcanoes may become so large that they break the ocean surface as new islands or floating pumice rafts.
In 2018, a multitude of seismic signals were detected by earthquake monitoring agencies all over the world in May and June. They created a weird humming sound and some of the signals detected in November of that year had a duration of up to 20 minutes. An oceanographic campaign in May 2019 showed that the previously mysterious humming noises were caused by the formation of an underwater volcano off the coast of Mayotte.
Subglacial volcanoes develop underneath icecaps. They are made up of flat lava which flows at the top of extensive pillow lavas and palagonite. When the icecap melts, the lava on top collapses, leaving a flat-topped mountain. These volcanoes are also called table mountains, tuyas, or (uncommonly) mobergs. Very good examples of this type of volcano can be seen in Iceland, however, there are also tuyas in British Columbia. The origin of the term comes from Tuya Butte, which is one of the several tuyas in the area of the Tuya River and Tuya Range in northern British Columbia. Tuya Butte was the first such landform analyzed and so its name has entered the geological literature for this kind of volcanic formation. The Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near the boundary with the Yukon Territory.
Mud volcanoes or mud domes are formations created by geo-excreted liquids and gases, although there are several processes which may cause such activity. The largest structures are 10 kilometers in diameter and reach 700 meters high.
Another way of classifying volcanoes is by the composition of material erupted (lava), since this affects the shape of the volcano. Lava can be broadly classified into four different compositions:
- If the erupted magma contains a high percentage (>63%) of silica, the lava is called felsic.
- Felsic lavas (dacites or rhyolites) tend to be highly viscous (not very fluid) and are erupted as domes or short, stubby flows. Viscous lavas tend to form stratovolcanoes or lava domes. Lassen Peak in California is an example of a volcano formed from felsic lava and is actually a large lava dome.
- Because siliceous magmas are so viscous, they tend to trap volatiles (gases) that are present, which cause the magma to erupt catastrophically, eventually forming stratovolcanoes. Pyroclastic flows (ignimbrites) are highly hazardous products of such volcanoes, since they are composed of molten volcanic ash too heavy to go up into the atmosphere, so they hug the volcano's slopes and travel far from their vents during large eruptions. Temperatures as high as 1,200 °C are known to occur in pyroclastic flows, which will incinerate everything flammable in their path and thick layers of hot pyroclastic flow deposits can be laid down, often up to many meters thick. Alaska's Valley of Ten Thousand Smokes, formed by the eruption of Novarupta near Katmai in 1912, is an example of a thick pyroclastic flow or ignimbrite deposit. Volcanic ash that is light enough to be erupted high into the Earth's atmosphere may travel many kilometres before it falls back to ground as a tuff.
- If the erupted magma contains 52–63% silica, the lava is of intermediate composition.
- These "andesitic" volcanoes generally only occur above subduction zones (e.g. Mount Merapi in Indonesia).
- Andesitic lava is typically formed at convergent boundary margins of tectonic plates, by several processes:
- If the erupted magma contains <52% and >45% silica, the lava is called mafic (because it contains higher percentages of magnesium (Mg) and iron (Fe)) or basaltic. These lavas are usually much less viscous than rhyolitic lavas, depending on their eruption temperature; they also tend to be hotter than felsic lavas. Mafic lavas occur in a wide range of settings:
- Some erupted magmas contain <=45% silica and produce ultramafic lava. Ultramafic flows, also known as komatiites, are very rare; indeed, very few have been erupted at the Earth's surface since the Proterozoic, when the planet's heat flow was higher. They are (or were) the hottest lavas, and probably more fluid than common mafic lavas.
Two types of lava are named according to the surface texture: ʻAʻa (pronounced [ˈʔaʔa]) and pāhoehoe ([paːˈho.eˈho.e]), both Hawaiian words. ʻAʻa is characterized by a rough, clinkery surface and is the typical texture of viscous lava flows. However, even basaltic or mafic flows can be erupted as ʻaʻa flows, particularly if the eruption rate is high and the slope is steep.
Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Usually, only mafic flows will erupt as pāhoehoe, since they often erupt at higher temperatures or have the proper chemical make-up to allow them to flow with greater fluidity.
Popular classification of volcanoes
A popular way of classifying magmatic volcanoes is by their frequency of eruption[according to whom?], with those that erupt regularly called active, those that have erupted in historical times but are now quiet called dormant or inactive, and those that have not erupted in historical times called extinct. However, these popular classifications—extinct in particular—are practically meaningless to scientists. They use classifications which refer to a particular volcano's formative and eruptive processes and resulting shapes.
There is no consensus among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes meaningless when compared to the lifespans of humans or even civilizations. For example, many of Earth's volcanoes have erupted dozens of times in the past few thousand years but are not currently showing signs of eruption. Given the long lifespan of such volcanoes, they are very active. By human lifespans, however, they are not.
Scientists usually consider a volcano to be erupting or likely to erupt if it is currently erupting, or showing signs of unrest such as unusual earthquake activity or significant new gas emissions. Most scientists consider a volcano active if it has erupted in the last 10,000 years (Holocene times)—the Smithsonian Global Volcanism Program uses this definition of active. Most volcanoes are situated on the Pacific Ring of Fire. An estimated 500 million people live near active volcanoes.
Historical time (or recorded history) is another timeframe for active. The Catalogue of the Active Volcanoes of the World, published by the International Association of Volcanology, uses this definition, by which there are more than 500 active volcanoes. However, the span of recorded history differs from region to region. In China and the Mediterranean, it reaches back nearly 3,000 years, but in the Pacific Northwest of the United States and Canada, it reaches back less than 300 years, and in Hawaii and New Zealand, only around 200 years.
As of 2013, the following are considered Earth's most active volcanoes:
- Kīlauea, the famous Hawaiian volcano, was in nearly continuous, effusive eruption (in which lava steadily flows onto the ground) between 1983 through 2018, and had the longest-observed lava lake.
- Mount Etna and nearby Stromboli, two Mediterranean volcanoes in "almost continuous eruption"[vague] since antiquity.[clarification needed]
- Piton de la Fournaise, in Réunion, erupts frequently enough to be a tourist attraction.
- Mount Yasur, 111 years
- Mount Etna, 109 years
- Stromboli, 108 years
- Santa María, 101 years
- Sangay, 94 years
Other very active volcanoes include:
- Mount Nyiragongo and its neighbor, Nyamuragira, are Africa's most active volcanoes
- Erta Ale, in the Afar Triangle, has maintained a lava lake since at least 1906.
- Mount Erebus, in Antarctica, has maintained a lava lake since at least 1972.
- Mount Merapi
- Whakaari / White Island, has been in a continuous state of releasing volcanic gas since before European observation in 1769.
- Ol Doinyo Lengai
- Arenal Volcano
- Klyuchevskaya Sopka
Extinct volcanoes are those that scientists consider unlikely to erupt again because the volcano no longer has a magma supply. Examples of extinct volcanoes are many volcanoes on the Hawaiian – Emperor seamount chain in the Pacific Ocean (although some volcanoes at the eastern end of the chain are active), Hohentwiel in Germany, Shiprock in New Mexico, Zuidwal volcano in the Netherlands and many volcanoes in Italy like Monte Vulture. Edinburgh Castle in Scotland is famously located atop an extinct volcano. Otherwise, whether a volcano is truly extinct is often difficult to determine. Since "supervolcano" calderas can have eruptive lifespans sometimes measured in millions of years, a caldera that has not produced an eruption in tens of thousands of years is likely to be considered dormant instead of extinct. Some volcanologists refer to extinct volcanoes as inactive, though the term is now more commonly used for dormant volcanoes once thought to be extinct.
Dormant and reactivated
It is difficult to distinguish an extinct volcano from a dormant (inactive) one. Dormant volcanoes are those that have not erupted for thousands of years, but are likely to erupt again in the future. Volcanoes are often considered to be extinct if there are no written records of its activity. Nevertheless, volcanoes may remain dormant for a long period of time. For example, Yellowstone has a repose/recharge period of around 700,000 years, and Toba of around 380,000 years. Vesuvius was described by Roman writers as having been covered with gardens and vineyards before its eruption of 79 CE, which destroyed the towns of Herculaneum and Pompeii. Before its catastrophic eruption of 1991, Pinatubo was an inconspicuous volcano, unknown to most people in the surrounding areas. Two other examples are the long-dormant Soufrière Hills volcano on the island of Montserrat, thought to be extinct before activity resumed in 1995, and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE and had long been thought to be extinct.
Technical classification of volcanoes
The three common popular classifications of volcanoes can be subjective and some volcanoes thought to have been extinct have erupted again. To help prevent people from falsely believing they are not at risk when living on or near a volcano, countries have adopted new classifications to describe the various levels and stages of volcanic activity. Some alert systems use different numbers or colors to designate the different stages. Other systems use colors and words. Some systems use a combination of both.
Volcano warning schemes of the United States
The United States Geological Survey (USGS) has adopted a common system nationwide for characterizing the level of unrest and eruptive activity at volcanoes. The new volcano alert-level system classifies volcanoes now as being in a normal, advisory, watch or warning stage. Additionally, colors are used to denote the amount of ash produced.
The Decade Volcanoes are 16 volcanoes identified by the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) as being worthy of particular study in light of their history of large, destructive eruptions and proximity to populated areas. They are named Decade Volcanoes because the project was initiated as part of the United Nations-sponsored International Decade for Natural Disaster Reduction (the 1990s). The 16 current Decade Volcanoes are
The Deep Earth Carbon Degassing Project, an initiative of the Deep Carbon Observatory, monitors nine volcanoes, two of which are Decade volcanoes. The focus of the Deep Earth Carbon Degassing Project is to use Multi-Component Gas Analyzer System instruments to measure CO2/SO2 ratios in real-time and in high-resolution to allow detection of the pre-eruptive degassing of rising magmas, improving prediction of volcanic activity.
Effects of volcanoes
There are many different types of volcanic eruptions and associated activity: phreatic eruptions (steam-generated eruptions), explosive eruption of high-silica lava (e.g., rhyolite), effusive eruption of low-silica lava (e.g., basalt), pyroclastic flows, lahars (debris flow) and carbon dioxide emission. All of these activities can pose a hazard to humans. Earthquakes, hot springs, fumaroles, mud pots and geysers often accompany volcanic activity.
The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen, carbon monoxide, halocarbons, organic compounds, and volatile metal chlorides.
Large, explosive volcanic eruptions inject water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), hydrogen chloride (HCl), hydrogen fluoride (HF) and ash (pulverized rock and pumice) into the stratosphere to heights of 16–32 kilometres (10–20 mi) above the Earth's surface. The most significant impacts from these injections come from the conversion of sulfur dioxide to sulfuric acid (H2SO4), which condenses rapidly in the stratosphere to form fine sulfate aerosols. The SO2 emissions alone of two different eruptions are sufficient to compare their potential climatic impact. The aerosols increase the Earth's albedo—its reflection of radiation from the Sun back into space—and thus cool the Earth's lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth, thereby warming the stratosphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface of up to half a degree (Fahrenheit scale) for periods of one to three years; sulfur dioxide from the eruption of Huaynaputina probably caused the Russian famine of 1601–1603.
A volcanic winter is thought to have taken place around 70,000 years ago after the supereruption of Lake Toba on Sumatra island in Indonesia. According to the Toba catastrophe theory to which some anthropologists and archeologists subscribe, it had global consequences, killing most humans then alive and creating a population bottleneck that affected the genetic inheritance of all humans today.
It has been suggested that volcanic activity caused or contributed to the End-Ordovician, Permian-Triassic, Late Devonian mass extinctions, and possibly others. The massive eruptive event which formed the Siberian Traps, one of the largest known volcanic events of the last 500 million years of Earth's geological history, continued for a million years and is considered to be the likely cause of the "Great Dying" about 250 million years ago, which is estimated to have killed 90% of species existing at the time.
The 1815 eruption of Mount Tambora created global climate anomalies that became known as the "Year Without a Summer" because of the effect on North American and European weather. Agricultural crops failed and livestock died in much of the Northern Hemisphere, resulting in one of the worst famines of the 19th century.
Sulfate aerosols promote complex chemical reactions on their surfaces that alter chlorine and nitrogen chemical species in the stratosphere. This effect, together with increased stratospheric chlorine levels from chlorofluorocarbon pollution, generates chlorine monoxide (ClO), which destroys ozone (O3). As the aerosols grow and coagulate, they settle down into the upper troposphere where they serve as nuclei for cirrus clouds and further modify the Earth's radiation balance. Most of the hydrogen chloride (HCl) and hydrogen fluoride (HF) are dissolved in water droplets in the eruption cloud and quickly fall to the ground as acid rain. The injected ash also falls rapidly from the stratosphere; most of it is removed within several days to a few weeks. Finally, explosive volcanic eruptions release the greenhouse gas carbon dioxide and thus provide a deep source of carbon for biogeochemical cycles.
Gas emissions from volcanoes are a natural contributor to acid rain. Volcanic activity releases about 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year. Volcanic eruptions may inject aerosols into the Earth's atmosphere. Large injections may cause visual effects such as unusually colorful sunsets and affect global climate mainly by cooling it. Volcanic eruptions also provide the benefit of adding nutrients to soil through the weathering process of volcanic rocks. These fertile soils assist the growth of plants and various crops. Volcanic eruptions can also create new islands, as the magma cools and solidifies upon contact with the water.
Ash thrown into the air by eruptions can present a hazard to aircraft, especially jet aircraft where the particles can be melted by the high operating temperature; the melted particles then adhere to the turbine blades and alter their shape, disrupting the operation of the turbine. Dangerous encounters in 1982 after the eruption of Galunggung in Indonesia, and 1989 after the eruption of Mount Redoubt in Alaska raised awareness of this phenomenon. Nine Volcanic Ash Advisory Centers were established by the International Civil Aviation Organization to monitor ash clouds and advise pilots accordingly. The 2010 eruptions of Eyjafjallajökull caused major disruptions to air travel in Europe.
Volcanoes on other celestial bodies
The Earth's Moon has no large volcanoes and no current volcanic activity, although recent evidence suggests it may still possess a partially molten core. However, the Moon does have many volcanic features such as maria (the darker patches seen on the moon), rilles and domes.
The planet Venus has a surface that is 90% basalt, indicating that volcanism played a major role in shaping its surface. The planet may have had a major global resurfacing event about 500 million years ago, from what scientists can tell from the density of impact craters on the surface. Lava flows are widespread and forms of volcanism not present on Earth occur as well. Changes in the planet's atmosphere and observations of lightning have been attributed to ongoing volcanic eruptions, although there is no confirmation of whether or not Venus is still volcanically active. However, radar sounding by the Magellan probe revealed evidence for comparatively recent volcanic activity at Venus's highest volcano Maat Mons, in the form of ash flows near the summit and on the northern flank.
There are several extinct volcanoes on Mars, four of which are vast shield volcanoes far bigger than any on Earth. They include Arsia Mons, Ascraeus Mons, Hecates Tholus, Olympus Mons, and Pavonis Mons. These volcanoes have been extinct for many millions of years, but the European Mars Express spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent past as well.
Jupiter's moon Io is the most volcanically active object in the solar system because of tidal interaction with Jupiter. It is covered with volcanoes that erupt sulfur, sulfur dioxide and silicate rock, and as a result, Io is constantly being resurfaced. Its lavas are the hottest known anywhere in the solar system, with temperatures exceeding 1,800 K (1,500 °C). In February 2001, the largest recorded volcanic eruptions in the solar system occurred on Io. Europa, the smallest of Jupiter's Galilean moons, also appears to have an active volcanic system, except that its volcanic activity is entirely in the form of water, which freezes into ice on the frigid surface. This process is known as cryovolcanism, and is apparently most common on the moons of the outer planets of the solar system.
In 1989, the Voyager 2 spacecraft observed cryovolcanoes (ice volcanoes) on Triton, a moon of Neptune, and in 2005 the Cassini–Huygens probe photographed fountains of frozen particles erupting from Enceladus, a moon of Saturn. The ejecta may be composed of water, liquid nitrogen, ammonia, dust, or methane compounds. Cassini–Huygens also found evidence of a methane-spewing cryovolcano on the Saturnian moon Titan, which is believed to be a significant source of the methane found in its atmosphere. It is theorized that cryovolcanism may also be present on the Kuiper Belt Object Quaoar.
A 2010 study of the exoplanet COROT-7b, which was detected by transit in 2009, suggested that tidal heating from the host star very close to the planet and neighboring planets could generate intense volcanic activity similar to that found on Io.
Traditional beliefs about volcanoes
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Many ancient accounts ascribe volcanic eruptions to supernatural causes, such as the actions of gods or demigods. To the ancient Greeks, volcanoes' capricious power could only be explained as acts of the gods, while 16th/17th-century German astronomer Johannes Kepler believed they were ducts for the Earth's tears. One early idea counter to this was proposed by Jesuit Athanasius Kircher (1602–1680), who witnessed eruptions of Mount Etna and Stromboli, then visited the crater of Vesuvius and published his view of an Earth with a central fire connected to numerous others caused by the burning of sulfur, bitumen and coal.
Various explanations were proposed for volcano behavior before the modern understanding of the Earth's mantle structure as a semisolid material was developed. For decades after awareness that compression and radioactive materials may be heat sources, their contributions were specifically discounted. Volcanic action was often attributed to chemical reactions and a thin layer of molten rock near the surface.
- Global Volcanism Program – American research program
- List of extraterrestrial volcanoes
- Maritime impacts of volcanic eruptions
- Prediction of volcanic activity
- Timeline of volcanism on Earth
- Volcanic Explosivity Index – qualitative scale indicating the explosive intensity of volcanic eruptions
- Volcano Number
- Volcano observatory
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- Volcanoes in human history: the far-reaching effects of major eruptions. Jelle Zeilinga de Boer, Donald Theodore Sanders (2002). Princeton University Press. p. 155. ISBN 0-691-05081-3
- Oppenheimer, Clive (2003). "Climatic, environmental and human consequences of the largest known historic eruption: Tambora volcano (Indonesia) 1815". Progress in Physical Geography. 27 (2): 230–259. doi:10.1191/0309133303pp379ra.
- Ó Gráda, Cormac (February 6, 2009). "Famine: A Short History". Princeton University Press. Archived from the original on January 12, 2016.
- McGee, Kenneth A.; Doukas, Michael P.; Kessler, Richard; Gerlach, Terrence M. (May 1997). "Impacts of Volcanic Gases on Climate, the Environment, and People". United States Geological Survey. Retrieved August 9, 2014. This article incorporates text from this source, which is in the public domain.
- "Volcanic Gases and Their Effects". U.S. Geological Survey. Retrieved June 16, 2007.
- Wieczorek, Mark A.; Jolliff, Bradley L.; Khan, Amir; Pritchard, Matthew E.; Weiss, Benjamin P.; Williams, James G.; Hood, Lon L.; Righter, Kevin; Neal, Clive R.; Shearer, Charles K.; McCallum, I. Stewart; Tompkins, Stephanie; Hawke, B. Ray; Peterson, Chris; Gillis, Jeffrey J.; Bussey, Ben (January 1, 2006). "The constitution and structure of the lunar interior". Reviews in Mineralogy and Geochemistry. 60 (1): 221–364. Bibcode:2006RvMG...60..221W. doi:10.2138/rmg.2006.60.3.
- Bindschadler, D.L. (1995). "Magellan: A new view of Venus' geology and geophysics". Reviews of Geophysics. 33 (S1): 459. Bibcode:1995RvGeo..33S.459B. doi:10.1029/95RG00281.
- "Glacial, volcanic and fluvial activity on Mars: latest images". European Space Agency. February 25, 2005. Retrieved August 17, 2006.
- "Exceptionally bright eruption on Io rivals largest in solar system". W.M. Keck Observatory. November 13, 2002.
- "Cassini Finds an Atmosphere on Saturn's Moon Enceladus". PPARC. March 16, 2005. Archived from the original on March 10, 2007. Retrieved July 4, 2014.
- Smith, Yvette (March 15, 2012). "Enceladus, Saturn's Moon". Image of the Day Gallery. NASA. Retrieved July 4, 2014.
- "Hydrocarbon volcano discovered on Titan". Newscientist.com. June 8, 2005. Retrieved October 24, 2010.
- Jaggard, Victoria (February 5, 2010). ""Super Earth" May Really Be New Planet Type: Super-Io". National Geographic web site daily news. National Geographic Society. Retrieved March 11, 2010.
- Williams, Micheal (November 2007). "Hearts of fire". Morning Calm (11–2007): 6.
- Macdonald, Gordon; Abbott, Agatin (1970). Volcanoes in the Sea: The Geology of Hawaii. University of Hawaii Press. ISBN 978-0-870-22495-9.
- Marti, Joan & Ernst, Gerald. (2005). Volcanoes and the Environment. Cambridge University Press. ISBN 978-0-521-59254-3.
- Ollier, Cliff (1969). Volcanoes. Australian National University Press. ISBN 978-0-7081-0532-0.
- Sigurðsson, Haraldur, ed. (2015). The Encyclopedia of Volcanoes (2 ed.). Academic Press. ISBN 978-0-12-385938-9. This is a reference aimed at geologists, but many articles are accessible to non-professionals.
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|Wikivoyage has a travel guide for Volcanoes.| | 0.913424 | 3.565104 |
Life from Space Fred Hoyle and Chandra Wickramasinghe look for Life from Space
PROOF and MORE PROOF
By kind permission of the Master and Fellows of St John's College. Photographer Unknown
In 2001 the ISRO stratospheric sampling of the stratosphere found evidence of bacteria of presumed cometary origin.
Between 2001 and 2006 comet missions continued to provide amazing consistency with the Hoyle-Wickramasinghe model.
Between 2001-2010 the role of viruses in evolution of life became generally accepted after the completion of the Human Genome Project. Viral fingerprints everywhere in our genes, exactly as Hoyle-Wickramasinghe predicted.
The unravelling of the human genome as well as the genomes of our nearest ancestors from 2001 onwards has led to many surprises. The number of useful genes in our genome has been reckoned close to 25,000, and over 8% of our total genome has been found to be comprised of gene sequences derived from viruses. These virus-related sequences are also present in our nearest evolutionary neighbours including chimpanzees. The picture now emerging is of our ancestral line being struck at regular intervals by devastating pandemics of viral disease. At each such pandemic all but a small immune breeding group were killed leaving the survivors carrying a residue of the virus in their genes.
Between 2004 and 2014 the discovery of habitable exoplanets have made panspermia - the transfer of life between planetary systems - inevitable. The current total in the galaxy exceeds 100 billion and there will be no stopping of life-exchanges between planetary systems. We live in one connected biosphere on a super galactic scale.
Between 2000 and 2015 the oldest evidence of life on Earth has moved back in time from 3.5 billion years ago to 3.83 billion years to 4.1 billion years. Fred suggested in late 1998 4.5 billion years (in a yet unpublished work). The oldest evidence currently accepted places this moment so far back that the primordial soup theory is virtually squeezed out of the geological record.
During 2014 to 2016 the Rosetta Mission to comet 67P/C-G has provided evidence that can most easily be explained by microbiology beneath a frozen crust. Space probes of Pluto, Enceladus and Ceres also show tantalising evidence of ongoing microbiology. | 0.893172 | 3.034192 |
Magnetic reconnection is a phenomenon of nature in which magnetic field lines change their topology in plasma and convert magnetic energy to particles by acceleration and heating. It is one of the most fundamental processes at work in laboratory and astrophysical plasmas. Magnetic reconnection occurs everywhere: in solar flares; coronal mass ejections; the earth’s magnetosphere; in the star forming galaxies; and in plasma fusion devices.
A field of physics that is growing in interest worldwide that tackles such astrophysical phenomena as the source of violent space weather and the formation of stars.
One of the most fundamental tenets of astrophysical plasma physics is that magnetic fields can be stretched and amplified by flowing plasmas. In the right geometry, this can even lead to the self-generation of magnetic fields from flow through the dynamo process, a positive feedback instability where seed magnetic fields are stretched and amplified by flow in such a way as to reinforce the initial seed. This happens only when plasma is highly conducting, fast flowing, and when the magnetic field is weak. Laboratory plasmas exploring this parameter regime are surprisingly rare.
In 2005 a novel imaging spectro-polarimeter, the Coronal Multi-channel Polarimeter (CoMP), was deployed to the Evans Facility in Sunspot, NM to measure the solar corona’s magnetic field. The design of the instrument permitted it to capture something quite unexpected – the ubiquitous Alfvénic motion of the coronal plasma. Shortly thereafter the NASA/JAXA Hinode mission observed the roots of the Alfvénic motion in the complex chromospheric boundary region between the Sun’s surface and the corona.
11th International Workshop on the Interrelationship between Plasma Experiments in Laboratory and Space (IPELS)
Three teams led by scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have won major blocks of time on two of the world’s most powerful supercomputers. Two of the projects seek to advance the development of nuclear fusion as a clean and abundant source of energy by improving understanding of the superhot, electrically charged plasma gas that fuels fusion reactions.
The physics of condensed matter provides a unique perspective on materials and systems of environmental relevance. I discuss three ways in which concepts and methods of condensed matter physics bear upon the quest for a sustainable future. Electronic devices made from metal oxides may enable new approaches to renewable energy, such as diodes that operate at optical frequencies to directly convert the electromagnetic field of sunlight to current.
Thirty-five years after their launches in 1977, the twin Voyager spacecraft have completed the Grand Tour of the outer planets and are now exploring the outer regions of the heliosphere. Soon they will be the first man-made objects to enter and explore interstellar space. Voyager 1 crossed the termination shock of the solar wind on December 16 2004 and Voyager 2 crossed the same structure on August 30 2007. The next destination is the heliopause, the boundary between plasma and magnetic fields from the Sun and plasma and magnetic fields from our galaxy.
Hantao Ji is a professor of Astrophysical Sciences at Princeton University and a Distinguished Research Fellow at PPPL. For more than 20 years he has been interested in the growing fields of plasma physics and astrophysics, and has dedicated his career to bringing them closer together.
Looking backwards, using fossil evidence from nearby galaxies provides a plausible picture of how galaxies have formed over cosmic time. Also, going forwards, the present quite definite cosmological model, shows how perturbations grew from low amplitude fluctuations via standard physical processes to the present world. Finally, we can employ large telescopes as a time-machines – directly observing the past history of our light-cone. While none of these approaches gives results accurate to more than 5-10%, a plausible picture emerges. Massive galaxies form in two phases.
Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.
© 2020 Princeton Plasma Physics Laboratory. All rights reserved. | 0.914249 | 3.937326 |
Last Wednesday, at 3:45 pm, scientists from the Breakthrough Listen project trained the Green Bank Telescope in West Virginia on 'Oumuamua—the mysterious, oblong space-rock which last month became the first known object to enter our solar system from elsewhere in the universe—and scanned it for signs of intelligent life.
For six hours, astronomers interrogated the interstellar asteroid. Green Bank swept across four radio bands and billions of individual channels, searching for transmissions as weak as the signal from your cell phone. Signals that could indicate 'Oumuamua is not just a rock but a spacecraft, with aliens—or alien technology—aboard.
By Thursday, astronomers had reported that their initial observations had turned up nothing. (Surprise!) If 'Oumuamua is harboring extraterrestrial stowaways, they're not producing a continuous signal across the frequencies Breakthrough Listen's researchers have monitored thus far. But Listen's scientists may have been onto something: Whether there's life aboard or not, 'Oumuamua kind of has the makings of an interstellar space vehicle.
Today in the journal Nature Astronomy, astronomers report observations that suggest 'Oumuamua is encased in a dry, carbon-rich crust that could have protected a water-ice core from being vaporized as it made a close pass of our sun earlier this year. You can almost think of it as the hull of a spaceship.
Or, if you prefer another analogy: "Basically you have a really nice baked Alaska," says Queen's University astronomer Alan Fitzsimmons, who led the investigation. "A flaming baked Alaska of an object with a rather warm exterior, but with a gooey, icy mixture in the middle."
Now, the researchers can't say definitively that there is ice in 'Oumuamua's middle (let alone extraterrestrial life), but spectral observations performed by Fitzsimmons' team suggest the object could have been icy long, long ago.
Different materials reflect light in different ways. By analyzing the spectrum that an object reflects, astronomers can see how the relative amount of light changes, and search for signatures of certain materials, like metals, rock, and ice.
Fitzsimmons’ team found that 'Oumuamua’s material composition seems to resemble that of objects at the outer edges of our own solar system. Astronomers hypothesize that beyond Jupiter, objects are far enough from the sun to contain a lot of ice—including on their surfaces. Billions of years ago, when the biggest, outer planets were forming, many of those objects were flung outward. Some still orbit our sun at the fringes of our solar system, in a thick bubble of icy debris called the Oort Cloud. Others were probably ejected from our solar system entirely.
If other solar systems formed like ours, it stands to reason that any object flung from such a system would be icy, too. "That's why we think it's more likely to see an interstellar object formed from ice, not rock," Fitzsimmons says. But when ‘Oumuamua passed by our sun, it didn’t behave like an object made of ice. | 0.899611 | 3.857673 |
The Milky Way: One of the Many Galaxies
The idea that each star is a sun, many with their own solar systems, is a powerful reminder of the immense scale of the cosmos. However, the distances to stars in our galaxy are tiny in comparison to distances to other galaxies.
Since antiquity, observers have noted the existence of nebulous stars; diffuse smudgy or cloudy looking stars. Some of them turned out to be what we now know as nebulae, the places where stars form. Many turned out to be something else entirely. It wasn't until the 1920s when it was confirmed that many of these nebulous stars were in fact completely different galaxies, whole other sets of billions of stars like the Milky Way, far beyond our own.
We now know the Milky Way is but one of the billions of galaxies in the universe. Looking back at how astronomy developed this concept over time one can see how philosophers and scientists struggled with comprehending the nature of galaxies, and thus the enormity of our universe.
The Milky Way Resolves into More Stars
To the naked eye it is unclear exactly what the Milky Way is. In ancient Greece, the atomist philosopher Democritus had proposed that the bright band of light might consist of distant stars. The atomists' views were eclipsed by Aristotle's perspectives on the universe.
In Aristotelian Cosmology, the Milky Way was understood to be the point where the celestial spheres came into contact with the terrestrial spheres. One of the important observations Galileo noted in his 1610 Sidereus Nuncius was that, under the view of a telescope, parts of the Milky Way resolved into a cluster of many stars. Once again a weakness in Aristotelian Cosmology was found - the Milky Way wasn't the result of interactions between the terrestrial and celestial spheres. Galileo's observations demonstrated the Milky Way was a massive grouping of individual stars, planets and other nebulous elements.
Island Universes and External Creations
In 1750, English astronomer Thomas Wright, published An original theory or new hypothesis of the Universe. In this book, Wright speculated that the Milky Way was a flat layer of stars, a part of which which was our solar system.
Beyond this he suggested that many of the very faint nebulae "in all likelihood may be external creation, bordering upon the known one, too remote for even our telescopes to reach." The idea that the faint nebulae could be their own "external creations" suggested the universe was much large than previously imagined. In 1755, philosopher Immanuel Kant elaborated on Wright's ideas and referred to these faint nebulae as "island universes." Both the notions of external creations and island universes struggled to capture the implications of this new larger scale of the universe. Beyond the fact that our sun was a star, could nebulae be their own universes or completely separate creations?
Surveying the Milky Way
In the 1780s William Herschel surveyed the stars in a range of different directions. He found that the stars were much denser on one side of the sky than those of the other side.
His son John Herschel conducted a similar study of the sky in the southern hemisphere and found the same pattern. What they were seeing was the core of the Milky Way galaxy, where there is a much greater density of stars.
Herschel had placed our sun nearly at the center of the Milky Way; it wouldn't be until the 1920's when Harlow Shapley's demonstrated that our sun was far from the center of the Milky Way.
Andromeda and Other Nebulae
Nebulous stars have been observed for thousands of years. In 964 Islamic astronomer Al-Sufi had observed and recorded what he called "a small cloud" in an illustration of the constellation Andromeda. We now understand this description as the Andromeda galaxy. Only with the advent and refinement of the telescope was it possible to start to document different kinds of nebulous stars.
As already mentioned, Thomas Wright and Immanuel Kant had published their speculations that faint nebulous stars like this were in fact independent entities like the Milky Way. In the late 18th century Charles Messier compiled a catalog of the 109 brightest nebulae, which was followed by a William Herschel's much larger catalog of over 5,000. Even while documenting all of these nebulae it remained unclear as to exactly what they were.
Finding and Interpreting Red Shift
Studying the light spectrum of nebulae like Andromeda would ultimately provide the information about what exactly these objects were. A range of astronomers worked on this issue in the early 20th century. In 1912 astronomer Vesto Slipher studied the light spectra of some of the brightest nebulae. He was interested in determining if they were made of the kinds of chemicals one would expect to find in a planetary system.
Slipher found something very interesting - it is possible to calculate the relative speed and distance of a star or nebulae is moving by examining the light spectrum it gives off and seeing how much the indicators for elements have shifted into the blue or red color spectrum. Objects shifted blue are moving closer to us and red shifted objects are moving away from us. In Slipher's analysis, the spectrums for the nebula were shifted so far into the red that these nebulae must be moving away from the earth at speeds beyond the escape velocity of the Milky Way. Along with this evidence, in 1917 Herber Curtis observed a nova, the brightening of an exploding star, inside the Andromeda Nebula. Looking back over photographs of the Nebula he was able to document 11 more novae that were on average 10 times fainter than those of the Milky Way. The evidence was mounting to suggest that these nebulae were well outside the Milky Way.
In 1920, Harlow Shapley and Heber Curtis debated the nature of the Milky Way, nebulae and the scale of the universe. Using the 100 inch telescope at Mt. Wilson, Edwin Hubble was able to resolve the edges of some spiral nebulae to identify they were in fact collections of stars, some of which matched standard patterns that enable astronomers to calculate that the stars were too distant to be part of the Milky Way. Thus, the idea of the Milky Way as just one of many galaxies came to be the dominant scientific perspective.
Where the Earth was once understood to be the center of a relatively small universe we have come to understand it as one world orbiting one of the 300 billion stars in our galaxy which is itself just one of more than a hundred billion of galaxies in the observable universe. Even today it remains difficult to grasp just how tiny and small our planet is in the vastness of the observable universe. | 0.871387 | 3.834521 |
In the Martian north, summer brings a nightly dusting of snow.
This surprising scene comes courtesy of new simulations of flip-flopping layers in the Martian atmosphere, which mix more vigorously than expected and produce stormy weather.
Though still virtual, the snow shower fits quite well with an observation made by a robot placed on Mars in 2008—and it may offer an explanation for how a very different type of snow falls out of the red planet’s polar skies.
If the simulations are correct, the summertime snow on Mars happens in bursts that can last for several hours, scientists report in a study describing the find published today in the journal Nature Geoscience. Flakes of water ice fall from clouds high in the planet’s atmosphere, sometimes failing to reach the ground, but perhaps occasionally leaving a frosty fingerprint that greets the dawn.
“There’s not enough to build a snowman,” says study coauthor Aymeric Spiga, a planetary scientist at the French National Center for Scientific Research. Still, the snow is probably a substantial player in the planet’s water cycle.
“The snowfall, the downbursts, that’s all very novel, very neat,” says John Wilson of NASA’s Ames Research Center. “That probably is what’s taking place in the real Mars atmosphere, and it’s bound to have an impact on how water gets distributed.”
Dry Ice Storms
The case for snow falling on Mars has been building for some time. For starters, we know the red planet has clouds and subsurface water ice.
NASA’s Phoenix lander, which set itself down near the Martian north pole in 2008, spotted wispy structures high overhead that looked a lot like virga streaks on Earth. Here, these streaks are formed when precipitation doesn’t quite reach the ground, so scientists concluded that Phoenix had seen a high-altitude snowstorm of water ice.
Fast forward to 2012, when scientists announced that NASA’s Mars Reconnaissance Orbiter observed what looked like a cloud of carbon dioxide snowflakes over the southern pole.
It’s the only time such dry-ice snow has been spotted falling anywhere in the solar system. Unlike the delicate virga in the north, it not only reaches the ground, but also contributes significantly to the planet’s seasonal carbon dioxide ice caps, says Paul Hayne of NASA’s Jet Propulsion Laboratory.
“The CO2 storms are much more intense,” Hayne says. In terms of its contribution to the caps, “we estimated up to 20 percent of the seasonal accumulation, which is several meters in total.”
To figure out how the planet’s water ice clouds contribute to Martian meteorology, Spiga and his colleagues set up a high-resolution computer model and watched what happened in their patch of digital Martian atmosphere.
Over the Martian night, water-ice clouds radiate infrared light that cools the surrounding atmosphere. This causes blobs of very cold air to settle on top of warmer air. Those cool blobs then sink, producing strong currents and tempestuous winds that weren’t anticipated to occur in Martian clouds.
The icy particles in the clouds get pushed around by the convective currents and ultimately shoved toward the surface in bursts of precipitation.
Hayne says the clouds’ self-promotional snowfall is one of the key findings of the simulation.
“By radiating energy, the clouds cause the surrounding air to cool more rapidly, which leads to more cloud growth and ultimately snowfall,” he says, although he isn’t sure whether the same mechanism might explain the more dramatic dry ice snowstorms he observed.
Still, it’s a nice result that fits in neatly with the Phoenix observations, Wilson says. A former meteorologist at NOAA, Wilson is now working on simulating Martian climate at NASA. He says these are the kinds of observations that could become important ingredients in the complex global models used to understand Mars.
Ultimately, scientists would like to use these models to rewind time and glimpse the planet’s watery past—but such things can’t be done confidently until the models accurately replicate its current climate.
“Ten years ago, the water-ice clouds were thought to have little impact on Mars climate,” Wilson says. “Now, we realize they have a big impact … and so things become richer and more complex and interesting than we suspected.” | 0.830061 | 3.945546 |
HONOLULU, Hawaii — The Earth and sun sit right next to a wavy rope of gas. It’s got lots of stars being born in it. But astronomers never noticed it before.
“Perhaps the oddest feature is how close it is to the sun, and we didn’t know about it,” said Alyssa Goodman. She is an astrophysicist at Harvard University in Cambridge, Mass. She described the newfound gas at a news conference on January 7. It took place at a meeting, here, of the American Astronomical Society. The finding also was published the same day in Nature.
Stars are born in gas clouds known as stellar nurseries. There are lots of these nurseries nearby, such as the Orion Nebula. And, it turns out, most are actually stretched along one continuous thread of gas. That gas thread stretches roughly 9,000 light-years, Goodman’s team now reports.
The thread resembles a wave. And the wave soars above and below the disk of our galaxy by about 500 light-years. At one point, it comes within 1,000 light-years of our solar system.
The team dubbed the newly found structure the Radcliffe Wave. Goodman said the team chose this name in honor of the institute where much of the work was done. It was also named for the early 20th century female astronomers from Radcliffe College. The college was a female liberal arts school that eventually became part of Harvard University.
Despite how close the wave is to us, astronomers noticed it only now. And they only noticed it now because of recent advances in the ability to pinpoint distances to known star-forming gas clouds. To nail down those distances, Goodman and her colleagues looked at stars behind the clouds. The team then figured out how dust within those clouds altered the colors of the stars.
The researchers then combined the measurements with distances to those stars. Those data were provided by the European Space Agency’s Gaia satellite. The results allowed the team to map in 3-D the locations of the clouds with newfound precision. And that map showed the gas clouds line up along the wave.
“These kinds of waves have been seen in external galaxies,” says Lynn Matthews. She was not involved with this study. An astrophysicist, she works at the MIT Haystack Observatory in Westford, Mass. The new finding “gives us an opportunity to tie together phenomena that have been observed in several galaxies,” she says. It also helps offer “a unifying picture of what might cause these sorts of features,” she adds.
There’s one take-home message from the study. Another involves a structure called Gould’s Belt. Since 1879, astronomers thought this belt was a nearby ring of stars and gas. But its origin has long been debated. The new study shows it never existed. The ring was just an illusion. It was a 2-D projection of the newly discovered wave onto the sky.
“It’s a very careful study,” says Jay Lockman. He is an astrophysicist at Green Bank Observatory in West Virginia. He, too, was not involved with the new research. “What’s interesting about this [new finding],” he says, “is it ties together a lot of very familiar things in the sky that previously had a very different model.”
How the wave formed is unknown. So is what it means for understanding the Milky Way. The wave “could have been from a collision, something falling down on the Milky Way,” Goodman said. Matthews has another idea. She and her colleagues saw something similar in a spiral galaxy known as IC 2233. As a result, she thinks such gas waves might arise from gravitational disturbances. She thinks that such waves could come the interactions of structures within the galaxy.
“The main point is it’s something internal to the galaxy,” Matthews says. If that’s the case, then there’s no need to have a dwarf galaxy or something else colliding with the Milky Way to make such a wave.
Regardless of how it formed, this gas thread might have interacted with the sun before. The astronomers traced the motion of the sun through space backward in time. This revealed that our solar system likely passed right through Radcliffe’s Wave roughly 13 million years ago. And when it did, it would have made the night sky look amazing. It would have been full of bright, beautiful gas clouds, Matthews said. They “would have been a lot closer and a lot easier to see — and possibly all around us.” | 0.870073 | 3.820832 |
The planet, called Kepler-22b, joins a list of more than 500 planets found to orbit stars beyond our solar system. It is the smallest and the best positioned to have liquid water on its surface -- among the ingredients necessary for life on Earth.
"We are homing in on the true Earth-sized, habitable planets," said San Jose State University astronomer Natalie Batalha, deputy science team lead for NASA's Kepler Space Telescope that discovered the star.
The telescope, which was launched three years ago, is staring at about 150,000 stars in the constellations Cygnus and Lyra, looking for faint and periodic dimming as any circling planets pass by, relative to Kepler's line of sight.
Results will be extrapolated to determine the percentage of stars in the Milky Way galaxy that harbor potentially habitable, Earth-size planets.
This is the first detection of a potentially habitable world orbiting a Sun-like star, scientists reported in findings to be published in The Astrophysical Journal.
Kepler-22b is 600 light years away. A light year is the distance light travels in a year, about 6 trillion miles (10 trillion km).
Planets about the same distance from their parent stars as Earth take roughly a year to complete an orbit. Scientists want to see at least three transits to be able to rule out other explanations for fluctuations in a star's light, such as small companion stars. Results also are verified by ground and other space telescopes.
Kepler-22b, which is about 2.4 times the radius of Earth, sits squarely in its star's so-called "habitable zone," the region where liquid water could exist on the surface. Follow-up studies are under way to determine if the planet is solid, like Earth, or more gaseous like Neptune.
"We don't know anything about the planets between Earth-size and Neptune-size because in our solar system we have no examples of such planets. We don't know what fraction are going to be rocky, what fraction are going to be water worlds, what fraction are ice worlds. We have no idea until we measure one and see," Batalha said at a news conference at NASA Ames Research Center in Moffet Field, California.
If Kepler-22b has a surface and a cushion of atmosphere similar to Earth's, it would be about 72 degrees Fahrenheit (22 C), about the same as a spring day in Earth's temperate zone.
Among the 2,326 candidate planets found by the Kepler team, 10 are roughly Earth-size and reside in their host stars' habitable zones.
Another team of privately funded astronomers is scanning the target stars for non-naturally occurring radio signals, part of a project known as SETI, or the Search for Extraterrestrial Intelligence.
"As soon as we find a different, a separate, an independent example of life somewhere else, we're going to know that it's ubiquitous throughout the universe," said astronomer Jill Tarter, director of the SETI Institute in Mountain View.
The Kepler team is meeting for its first science conference this week. | 0.848987 | 3.911151 |
Moon* ♍ Virgo
Moon phase on 20 September 2055 Monday is New Moon, 1 day young Moon is in Virgo.Share this page: twitter facebook linkedin
Moon rises at sunrise and sets at sunset. It's part facing the Earth is completely in shadow.
Moon is passing about ∠19° of ♍ Virgo tropical zodiac sector.
Lunar disc is not visible from Earth. Moon and Sun apparent angular diameters are ∠1966" and ∠1911".
Next Full Moon is the Hunter Moon of October 2055 after 15 days on 5 October 2055 at 18:38.
There is high New Moon ocean tide on this date. Combined Sun and Moon gravitational tidal force working on Earth is strong, because of the Sun-Moon-Earth syzygy alignment.
At 18:15 on this date the Moon completes the old and enters a new synodic month with lunation 688 of Meeus index or 1641 from Brown series.
29 days, 8 hours and 5 minutes is the length of new lunation 688. This is the year's shortest synodic month of 2055. It is 25 minutes shorter than next lunation 689 length.
Length of current synodic month is 4 hours and 39 minutes shorter than the mean length of synodic month, but it is still 1 hour and 30 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠336.4°. At the beginning of next synodic month true anomaly will be ∠352.8°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
11 days after point of apogee on 8 September 2055 at 13:59 in ♈ Aries. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next day, until it get to the point of next perigee on 21 September 2055 at 12:32 in ♎ Libra.
Moon is 364 522 km (226 503 mi) away from Earth on this date. Moon moves closer next day until perigee, when Earth-Moon distance will reach 357 315 km (222 025 mi).
2 days after its ascending node on 17 September 2055 at 19:18 in ♌ Leo, the Moon is following the northern part of its orbit for the next 9 days, until it will cross the ecliptic from North to South in descending node on 30 September 2055 at 10:30 in ♒ Aquarius.
2 days after beginning of current draconic month in ♌ Leo, the Moon is moving from the beginning to the first part of it.
4 days after previous North standstill on 15 September 2055 at 17:00 in ♋ Cancer, when Moon has reached northern declination of ∠20.530°. Next 7 days the lunar orbit moves southward to face South declination of ∠-20.612° in the next southern standstill on 28 September 2055 at 05:09 in ♑ Capricorn.
The Moon is in New Moon geocentric conjunction with the Sun on this date and this alignment forms Sun-Moon-Earth syzygy. | 0.837327 | 3.11325 |
Extreme trans-Neptunian object
An extreme trans-Neptunian object (ETNO) is a minor planet and trans-Neptunian object, orbiting the Sun well beyond Neptune (30 AU) in the outermost region of the Solar System. An ETNO has a large semi-major axis of at least 150–250 AU. Its orbit is much less affected by the known giant planets than all other known trans-Neptunian objects. They may, however, be influenced by gravitational interactions with a hypothetical Planet Nine, shepherding these objects into similar types of orbits.
ETNOs can be divided into three different subgroups. The scattered ETNOs (or extreme scattered disc objects, ESDOs) have perihelia around 38–45 AU and an exceptionally high eccentricity of more than 0.85. As with the regular scattered disc objects, they were likely formed as result of gravitational scattering by Neptune and still interact with the giant planets. The detached ETNOs (or extreme detached disc objects, EDDOs), with perihelia approximately between 40–45 and 50–60 AU, are less affected by Neptune than the scattered ETNOS, but are still relatively close to Neptune. The sednoid or inner Oort cloud objects, with perihelia beyond 50–60 AU, are too far from Neptune to be strongly influenced by it.
Among the extreme trans-Neptunian objects are the sednoids, three objects with an outstandingly high perihelion: Sedna, 2012 VP113 ("Biden"), and 2015 TG387 ("Goblin"). Sedna and 2012 VP113 are distant detached objects with perihelia greater than 70 AU. Their high perihelia keep them at a sufficient distance to avoid significant gravitational perturbations from Neptune. Previous explanations for the high perihelion of Sedna include a close encounter with an unknown planet on a distant orbit and a distant encounter with a random star or a member of the Sun's birth cluster that passed near the Solar System.
Most distant objects from the Sun
Trujillo and Sheppard discoveries
- 2013 FT28, Longitude of perihelion aligned with Planet Nine, but well within the proposed orbit of Planet Nine, where computer modeling suggests it would be safe from gravitational kicks.
- 2014 SR349, appears to be anti-aligned with Planet Nine.
- 2014 FE72, an object with an orbit so extreme that it reaches about 3,000 AU from the Sun in a massively-elongated ellipse – at this distance its orbit is influenced by the galactic tide and other stars.
Outer Solar System Origins Survey
- 2013 SY99, which has a lower inclination than many of the objects, and which was discussed by Michele Bannister at a March 2016 lecture hosted by the SETI Institute and later at an October 2016 AAS conference.
- 2015 KG163, which has an orientation similar to 2013 FT28 but has a larger semi-major axis that may result in its orbit crossing Planet Nine's.
- 2015 RX245, which fits with the other anti-aligned objects.
- 2015 GT50, which is in neither the anti-aligned nor the aligned groups; instead, its orbit's orientation is at a right angle to that of the proposed Planet Nine. Its argument of perihelion is also outside the cluster of arguments of perihelion.
Since early 2016, ten more extreme trans-Neptunian objects have been discovered with orbits that have a perihelion greater than 30 AU and a semi-major axis greater than 250 AU bringing the total to sixteen (see table below for a complete list). Most eTNOs have perihelia significantly beyond Neptune, which orbits 30 AU from the Sun. Generally, TNOs with perihelia smaller than 36 AU experience strong encounters with Neptune. Most of the eTNOs are relatively small, but currently relatively bright because they are near their closest distance to the Sun in their elliptical orbits. These are also included in the orbital diagrams and tables below.
☊ or Ω (°)
|2013 FT28||Metastable||5,050||295||43.60||546||57.0||0.86||40.2||17.3||217.8||258.0 (*)||6.7||24.4||200|
|2013 SL102||?||5,590||315||38.1||592||39.1||0.88||265.3||6.5||94.6||359.9 (*)||7.0||23.1||140|
|2014 WB556||?||4,900||290||42.71||536||46.5||0.85||235.3||24.2||115.0||350.3 (*)||7.3||24.1||150|
|2015 GT50||Unstable||5,510||310||38.45||580||41.7||0.89||129.2||8.8||46.1||175.3 (*)||8.5||24.9||80|
|2015 KG163||Unstable||17,730||680||40.51||1,320||40.8||0.95||32.0||14.0||219.1||251.1 (*)||8.1||24.3||100|
|2018 VM35||?||4,500||270||44.69||504||54.9||0.84||303.5||8.5||192.4||135.9 (*)||7.7||25.0||140|
- (*) longitude of perihelion, ϖ, outside expected range;
- are the objects included in the original study by Trujillo and Sheppard (2014).
- has been added in the 2016 study by Brown and Batygin.
- All other objects have been announced later.
The most extreme case is that of 2015 BP519, nicknamed Caju, which has both the highest inclination and the farthest nodal distance; these properties make it a probable outlier within this population.
- Given the orbital eccentricity of these objects, different epochs can generate quite different heliocentric unperturbed two-body best-fit solutions to the semi-major axis and orbital period. For objects at such high eccentricity, the Sun's barycenter is more stable than heliocentric values. Barycentric values better account for the changing position of Jupiter over Jupiter's 12 year orbit. As an example, 2007 TG422 has an epoch 2012 heliocentric period of ~13,500 years, yet an epoch 2017 heliocentric period of ~10,400 years. The barycentric solution is a much more stable ~11,300 years.
- Brown, Michael E.; Trujillo, Chadwick; Rabinowitz, David (2018). "A New High Perihelion Inner Oort Cloud Object". arXiv:1810.00013 [astro-ph.EP].
- de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (12 September 2018). "A Fruit of a Different Kind: 2015 BP519 as an Outlier among the Extreme Trans-Neptunian Objects". Research Notes of the AAS. 2 (3): 167. arXiv:1809.02571. Bibcode:2018RNAAS...2c.167D. doi:10.3847/2515-5172/aadfec.
- Wall, Mike (24 August 2011). "A Conversation With Pluto's Killer: Q & A With Astronomer Mike Brown". Space.com. Retrieved 7 February 2016.
- Brown, Michael E.; Trujillo, Chadwick; Rabinowitz, David (2004). "Discovery of a Candidate Inner Oort Cloud Planetoid". The Astrophysical Journal. 617 (1): 645–649. arXiv:astro-ph/0404456. Bibcode:2004ApJ...617..645B. doi:10.1086/422095.
- Brown, Michael E. (28 October 2010). "There's something out there – part 2". Mike Brown's Planets. Retrieved 18 July 2016.
- "Objects beyond Neptune provide fresh evidence for Planet Nine". 2016-10-25.
The new evidence leaves astronomer Scott Sheppard of the Carnegie Institution for Science in Washington, D.C., "probably 90% sure there's a planet out there." But others say the clues are sparse and unconvincing. "I give it about a 1% chance of turning out to be real," says astronomer JJ Kavelaars, of the Dominion Astrophysical Observatory in Victoria, Canada.
- "PLANET 9 SEARCH TURNING UP WEALTH OF NEW OBJECTS". 2016-08-30.
- "Extreme New Objects Found At The Edge of The Solar System".
- "The Search for Planet Nine: New Finds Boost Case for Distant World".
- "HUNT FOR NINTH PLANET REVEALS NEW EXTREMELY DISTANT SOLAR SYSTEM OBJECTS". 2016-08-29.
- Shankman, Cory; et al. (2017). "OSSOS VI. Striking Biases in the detection of large semimajor axis Trans-Neptunian Objects". The Astronomical Journal. 154 (4): 50. arXiv:1706.05348. Bibcode:2017AJ....154...50S. doi:10.3847/1538-3881/aa7aed. hdl:10150/625487.
- SETI Institute (18 March 2016). "Exploring the outer Solar System: now in vivid colour - Michele Bannister (SETI Talks)". YouTube. 28:17. Retrieved 18 July 2016.
- Bannister, Michele T.; et al. (2016). "A new high-perihelion a ~700 AU object in the distant Solar System". American Astronomical Society, DPS Meeting #48, Id. 113.08. 48: 113.08. Bibcode:2016DPS....4811308B.
- Hand, Eric (20 January 2016). "Astronomers say a Neptune-sized planet lurks beyond Pluto". Science. doi:10.1126/science.aae0237. Retrieved 20 January 2016.
- Grush, Loren (20 January 2016). "Our solar system may have a ninth planet after all — but not all evidence is in (We still haven't seen it yet)". The Verge. Retrieved 18 July 2016.
The statistics do sound promising, at first. The researchers say there's a 1 in 15,000 chance that the movements of these objects are coincidental and don't indicate a planetary presence at all. ... 'When we usually consider something as clinched and air tight, it usually has odds with a much lower probability of failure than what they have,' says Sara Seager, a planetary scientist at MIT. For a study to be a slam dunk, the odds of failure are usually 1 in 1,744,278 . ... But researchers often publish before they get the slam-dunk odds, in order to avoid getting scooped by a competing team, Seager says. Most outside experts agree that the researchers' models are strong. And Neptune was originally detected in a similar fashion — by researching observed anomalies in the movement of Uranus. Additionally, the idea of a large planet at such a distance from the Sun isn't actually that unlikely, according to Bruce Macintosh, a planetary scientist at Stanford University.
- Batygin, Konstantin; Brown, Michael E. (2016). "Evidence for a distant giant planet in the Solar system". The Astronomical Journal. 151 (2): 22. arXiv:1601.05438. Bibcode:2016AJ....151...22B. doi:10.3847/0004-6256/151/2/22.
- Koponyás, Barbara (10 April 2010). "Near-Earth asteroids and the Kozai mechanism" (PDF). 5th Austrian-Hungarian Workshop in Vienna. Retrieved 18 July 2016.
- Horizons output. "Barycentric Osculating Orbital Elements". Retrieved 4 February 2020. (Solution using the Solar System Barycenter and barycentric coordinates. (Type the target body's name, then select Ephemeris Type:Elements and Center:@0) In the second pane "PR=" can be found, which gives the orbital period in days (For Sedna as an example, the value 4.16E+06 is displayed, which is ~11400 Julian years).
- "MPC list of q > 30 and a > 250". Minor Planet Center. Retrieved 5 February 2020.
- Relative to hypothetical Planet Nine, Batygin, Konstantin; Adams, Fred C.; Brown, Michael E.; Becker, Juliette C. "The Planet Nine Hypothesis". arXiv:1902.10103. Cite journal requires
- "JPL Small-Body Database Browser". 13 December 2012. Archived from the original on 13 December 2012.
- Chamberlin, Alan. "JPL Small-Body Database Browser". ssd.jpl.nasa.gov.
- Becker, Juliette (2017). Evaluating the Dynamical Stability of Outer Solar System Objects in the Presence of Planet Nine. DPS49. American Astronomical Society. Retrieved 14 March 2018.
- Lovett, Richard A. (16 December 2017). "The hidden hand - Could a bizarre hidden planet be manipulating the solar system". New Scientist International. No. 3156. p. 41. Retrieved 14 March 2018.
- Bannister, Michelle T.; et al. (2018). "OSSOS. VII. 800+ Trans-Neptunian Objects — The complete data release". The Astrophysical Journal Supplement Series. 236 (1): 18. arXiv:1805.11740. Bibcode:2018ApJS..236...18B. doi:10.3847/1538-4365/aab77a. hdl:10150/628551.
- Trujillo, Chadwick A.; Sheppard, Scott S. (2014). "A Sedna-like body with a perihelion of 80 astronomical units" (PDF). Nature. 507 (7493): 471–474. Bibcode:2014Natur.507..471T. doi:10.1038/nature13156. PMID 24670765. Archived from the original (PDF) on 2014-12-16. Retrieved 2018-12-12.
- "Where is Planet Nine?". The Search for Planet Nine (Blog). 20 January 2016. Archived from the original on 30 January 2016.
- Witze, Alexandra (2016). "Evidence grows for giant planet on fringes of Solar System". Nature. 529 (7586): 266–7. Bibcode:2016Natur.529..266W. doi:10.1038/529266a. PMID 26791699.
- Becker, J. C.; et al. (DES Collaboration) (2018). "Discovery and Dynamical Analysis of an Extreme Trans-Neptunian Object with a High Orbital Inclination". The Astronomical Journal. 156 (2): 81. arXiv:1805.05355. Bibcode:2018AJ....156...81B. doi:10.3847/1538-3881/aad042.
- Known extreme outer solar system objects, Scott Sheppard, Carnegie Science Center
- Hunt for Ninth Planet Reveals New Extremely Distant Solar System Objects, Scott Sheppard, Carnegie Science Center
- List of Known Trans-Neptunian Objects (including ESDOs and EDDOs), Robert Jonston, Johnstson's Archive | 0.872006 | 3.950297 |
Nuclei lie at the center of every atom in the universe, provide 99.98% of its mass, and form the core of all matter. Learning how these tiny systems work teaches us about the hidden forces in nature that are only found inside nuclei, but provide almost all the energy that power the sun and stars, and which provides life and energy on earth. Nuclei play a crucial role in the history of our universe through element formation. One hundred years after the discovery of the nucleus, new experiments, new detector technologies, and new accelerators are being built to synthesize and study thousands of new totally unknown isotopes and deepen the universality of our understanding. Our group has programs in measuring and calculating the lightest nuclei from first principles, as well as in exploring the balance of forces that dictate what the heaviest nuclei might be, and how to synthesize them. We measure properties of nuclei far from stability, both on the neutron-rich side from fission-fragments as well as on the proton-rich side along the proton "drip-line" to understand stellar nucleosynthesis processes.
The understanding of nuclear structure is undergoing a period of renaissance, fueled by ab-initio approaches based on realistic nuclear forces. Currently, computational limitations restrict these calculations to the very lightest nuclei. However, insights gained from light nuclei have influence nuclear modeling across the nuclear chart. These include effects of three-body and higher correlations to describe the origin, mass and isospin dependence of the spin-orbit force, and on incorporating tensor forces that are now seen as essential to describe nuclei across the mass table. It is these “residual forces” which determine the shell-gaps across the nuclear landscape, and in turn, it is the shell bunching and gaps that dictate the observable properties of all heavier nuclei. The “new” magic numbers away from stability, the demise of traditional shell gaps, changes in pairing, and “islands of inversion” are all consequences of the isospin dependence of the residual forces. Understanding these effects is the core of the physics program for the Facility for Rare Isotope Beams (FRIB). The new approaches are tested and improved though benchmarking against precise nuclear data, specifically against data on the lightest nuclei. Precisely re-measuring some key transition rates in light nuclei, at the few percent level, is one of the goals of our proposed research. Experiments are carried out at Argonne and NSCL.
At the other end of the nuclear landscape, in very heavy nuclei, the situation is quite different. The nuclei are more classical in nature with higher level densities and liquid-drop-like properties strongly influenced by the ever-increasing Coulomb energy. However, the level densities are far from that of a Fermi gas, and gaps and bunching in the sequence of quantum states still modulate all observables. Information on the sequence and spacing of levels near the Fermi surface is sparse, especially in the domain of very heavy nuclei with Z > 100. However, this information is essential for understanding binding energies, decay rates, shapes, and pairing of the very heaviest systems. It is a convenient trick of nature that allows us to use deformation and rotation in Z ~ 100 nuclei, where production cross-sections are quite large, in order to populate some of the highest quantum states known in nuclei and then predict shell gaps in the true “Super Heavy” domain with Z > 120. Locating and identifying these states, and learning about correlations in these very heavy systems is the second thrust of our work. We have pioneered using actinide targets and multi-nucleon transfers to reach key states of interest. We have been using high-K isomer investigations and nucleon alignment techniques to learn about the deformed Nilsson states and their crossings. A key current issue is the influence of the shell gaps on pairing correlations which are very important, ill-understood, and far from constant across the region.
Decay properties of very neutron rich nuclei are of interest for nuclear structure, nuclear astrophysics, and for “applied” research in the nuclear energy domain. This research was originally motivated by the opportunities promised by the Californium Rare Isotope Breeder Unit (CARIBU) ion-source facility at Argonne National Laboratory, and in the longer term by the beams at FRIB. We have built a “Decay Beamline” at CARIBU and led the effort to design, build and operate the “X-Array” clover array system and the "SATURN" array of beta-decay and tape transport systems. We conduct experiments to study the beta and gamma decays of long-lived isomers in neutron-rich nuclei produced from the fission of the strong 252Cf source at CARIBU, and in “Decay Heat” and beta-delayed neutron studies of nuclei relevant to next-generation fuel cycles. We have also developed a novel scintillator array for detecting neutrons that is being tested for measuring beta-delayed neutrons emitted from neutron-rich nuclei in these experiments.
This research focuses on the study of neutron-deficient nuclei at the limits of nuclear stability, and the role they play in both unlocking the fundamental inner workings of the nucleus,as well as understanding nuclear processes that occur in extreme astrophysical environments. Although exotic isotopes live only for fractions of a second, their properties are critical for our understanding of processes that create the heavy elements in stars, in supernova explosions and in Type I X-ray bursts on the surface of neutron stars. Much of the work is centered on learning about the rapid proton-capture process, thought to take place during X-ray bursts. These periodic bursts can occur on timescales between 10 and 1,000 seconds and are highly energetic events. The characteristic shapes and intensities of their observed light curves are dictated by the properties of very neutron-deficient nuclei. Critical to this process are “waiting- point" nuclei, where a decrease in the proton capture rate is coupled with a long beta-decay half-life. Measuring the properties of key nuclides near the waiting points is one of the main goals of this research, primarily conducted at NSCL at present, and planned for FRIB in the future, where we will be able to produce and study exotic nuclei that are currently difficult or impossible to access, but are key to our understanding of the cosmos. | 0.880254 | 4.019682 |
While your computer is running idle, it could be finding new pulsars and black holes in deep space.
Three volunteers running the distributed computing program Einstein@Home have discovered a new pulsar in the data from the Arecibo Observatory radio telescope. Their computers, one in Iowa (owned by two people) and one in Germany, downloaded and processed the data that found the pulsar, which is in the Milky Way, approximately 17,000 light years from Earth in constellation Vulpecula.
"The way that we found the pulsar using distributed computing with volunteers is a new paradigm that we're going to make better use of in astronomy as time goes on," said astronomer Jim Cordes of Cornell University. "This really has legs."
About 250,000 volunteers run Einstein@Home, on average donating about 250 teraflops of computing power – equivalent to a quarter of the capacity of the largest supercomputer in the world, says program developer David Anderson of University of California at Berkeley's Space Sciences Laboratory, co-author of the Aug. 12 discovery announcement in Science.
Einstein@Home has been searching for gravitational waves in the data from the US LIGO Observatory since 2005, and since March 2009 has dedicated one-third of its power to searching for radio pulsars and black holes in the Arecibo data. As of this week, it will start dedicating half of its processing power to data from Arecibo, the world's largest and most sensitive radio telescope, physicist Bruce Allen of the Max Plank Institute for Gravitational Physics in Germany and co-author of the study announced a press conference Aug. 12.
The new pulsar, dubbed PSR J2007+2722, is a neutron star rotating 41 times per second. Pulsars are birthed when stars five to 10 times as massive as our sun explode into a supernova and then collapse into stars composed almost entirely of neutrons.
The data from Arecibo was processed on the computer in Iowa June 11, and then also processed on a computer in Germany June 14 for validation. The finding was part of a larger search that returned results on July 10, which was the first time a human being was aware of the discovery.
The person who looked at the results notified Greenbank Observatory in West Virginia, which immediately pointed their telescope at the new pulsar to verify it. Within hours, Arecibo Observatory in Puerto Rico also pointed their telescope at it.
"This is the first time I've worked closely with radio astronomers making a discovery," said Allen. "It was like watching 5-year-olds tearing Christmas presents. Or like watching someone throw chunks of meat at starving sharks."
Pulsars are named after the pulsing signals they send to Earth. The pulse comes from the spin and the magnetic field of the neutron star being on two different axes, which acts like an electric generator and creates a beamed signal that rotates like a lighthouse. Cordes says theoretical predictions are that only about 20 percent of the pulsars in the galaxy are detectable on Earth because the beam needs to point directly at us to be detected.
Often, pulsars have a companion star or neutron star that was originally born in the same cloud of gas. But this new pulsar doesn't and is likely a disrupted recycled pulsar. This means the pulsar once had a companion star that it sucked matter from as the star swelled up into a red giant, which caused the pulsar to cycle faster (recycle). The red giant star then exploded into a supernova and blasted the pulsar away, leaving it alone in space (disrupted).
The new pulsar is one of around 2000 pulsars that have been discovered using radio telescopes in the past 43 years, said Cordes. He estimates there are20,000 pulsars in the Milky Way that could be detected.
"I see this as a long-term effort where we're going to find really interesting objects," said Cordes. "We'd like to find a pulsar orbiting a black hole, or a pulsar orbiting another neutron star so that we can test some of Einstein's predictions of the general theory of relativity"
You can become part of the effort by downloading BOINC. The program has been used to create 70 different distributed computing projects (almost every one in existence except Folding@Home), and you can decide what fraction of your spare computing power you want to dedicate to each of the 70 projects.
In case you need more incentive, Cordes announced that a second pulsar has been already been discovered in the last month by Einstein@Home users in the United Kingdom and Russia. He's keeping details to himself for now.
"We have a very large data set," Cordes added at the press conference. "We just need to cull through it, and Einstein@Home lets us use a much finer comb."
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Images: 1) Screen shot of Einstein@Home/B. Knispel, Albert Einstein Institute. 2) Copyright Cornell University. | 0.82385 | 3.363612 |
In 1995, astronomer Bob Williams wanted to point the Hubble Space Telescope at a patch of sky filled with absolutely nothing remarkable. For 100 hours.
It was a terrible idea, his colleagues told him, and a waste of valuable telescope time. People would kill for that amount of time with the sharpest tool in the shed, they said, and besides — no way would the distant galaxies Williams hoped to see be bright enough for Hubble to detect.
Plus, another Hubble failure would be a public relations nightmare. Perceptions of the project, which had already cost multiple billions of dollars, were pretty dismal. Not much earlier, astronauts had dragged Hubble into the cargo bay of the space shuttle Endeavour and corrected a disastrous flaw in the prized telescope’s vision. After the fix, the previously blind eye in the sky could finally see stars as more than blurred points of light. And now, finally, it was time to start erasing the frustrations of Hubble’s early years.
Except that staring at nothing and coming up empty didn’t seem like the best way to do that.
But Williams was undeterred. And, to be honest, it didn’t really matter how much his colleagues protested. As director of the Space Telescope Science Institute, he had a certain amount of Hubble’s time at his personal disposal. “The telescope allocation committee would never have approved such a long, risky project,” he explains. “But as director, I had 10 percent of the telescope time, and I could do what I wanted.”
Wiliams suspected the billion light-year stare might capture eons of galactic evolution in a single frame and uncover some of the faintest, farthest galaxies ever seen. And to him, the potential observations were so important and so fundamental for understanding how the universe evolved that the experiment was a no-brainer, consequences be damned.
“Scientific discovery requires risk,” Williams says. “And I was at a point in my career where I said, “If it’s that bad, I’ll resign. I‘ll fall on my sword.’”
So, with his job perhaps on the line, Williams went off, put together a small team of post-docs, and did exactly as he’d planned. For 100 hours, between Dec. 18 and 28, Hubble stared at a patch of sky near the Big Dipper’s handle that was only about 1/30th as wide as the full moon. In total, the telescope took 342 pictures of the region, each of which was exposed for between 25 and 45 minutes. The images were processed and combined, then colored, and 17 days later, released to the public.
It turned out that “nothing” was actually stuffed with of galaxies. More than 3,000 of them came spilling out, some roughly 12 billion years old. Spiral, elliptical, irregular – red, white, blue, and yellow – the smudges of light that leapt from the final composite image cracked the universe in ways scientists never could have imagined.
“With this achievement, the estimated number of galaxies in the universe had multiplied enormously — to 50 billion, five times more than previously expected,” wrote John Noble Wilford in The New York Timesin The New York Times. And some of the older galaxies – those distant, faint ones that were supposedly impossible for Hubble to see – looked really, really different.
“When the galaxies were young, they were very irregular — they were having collisions, they were erupting, they were having adolescent outbursts,” says Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics. He was among the scientists who initially thought the deep field was a bad idea. “Bob was right, I was wrong. The use of that discretionary time was a courageous thing,” he says.
But there was more. Williams had gotten in touch with astronomers at the Keck telescopes in Hawaii ahead of time and asked them to point their Earth-based guns at the same patch of sky. Together, the observations helped astronomers develop something of a shortcut for determining cosmological distances to these galaxies, unlocking large portions of the universe.
As for public relations? The image now known as the Hubble Deep Field captivated pretty much everyone. To say it was a triumph would be an understatement. “The nerve that it took to say, ‘We’re going to point where there isn’t anything,’ was interesting,” says John Mather, a Nobel Laureate and senior project scientist for the James Webb Space Telescope. “And Bob Williams got a lot of nice recognition for that leadership.”
Not long after, Williams’ experiment was repeated in a different patch of sky in the southern constellation Tucana, and came to be called the Hubble Deep Field South. In 2004, a million-second exposure of nothing produced the Hubble Ultra Deep Field, filled with even more galaxies than the original. And in 2012, combining 10 years of Ultra Deep Field exposures produced the Hubble eXtreme Deep Field.
These images have offered “a glimpse of the hundreds of billions of galaxies that fill the universe,” says Hubble senior scientist Jennifer Wiseman, of NASA’s Goddard Space Flight Center. “That gives me and many people pause to be quiet and contemplate this majestic universe we live in, and be grateful we have a chance to look at it.”
Jason Kalirai, project scientist with the Webb telescope, goes and step further and places the Hubble Deep Field in a rather impressive historical context. “One of the questions that even the earliest civilizations probably asked themselves is, ‘What is our place in the universe?'” There have been a few times in our history when the prevailing answer to that question has been overthrown, he says. Once was when Galileo turned his telescope to Jupiter and its moons and helped show that not everything revolves around the Earth; another was when the astronomer Edwin Hubble showed, in the early 1900s, that not every speck of light in the sky belongs to our own galaxy.
A third is the Hubble Deep Field. “It showed that the universe is teeming with these galaxies, and if you do a census of how many galaxies you see, and think about how many more are in the night sky, you can conclude that there are as many galaxies as there are stars in the Milky Way,” Kalirai says.
As for Williams? Well, he sums up the experience in a characteristically understated way: “It turned out to be a neat image. Really.” | 0.815092 | 3.496143 |
That the Moon formed and Earth’s geochemistry was reset by our planet’s collision with another, now vanished world, has become pretty much part of the geoscientific canon. It was but one of some unimaginably catastrophic events that possibly characterised the early Solar System and those around other stars. Since the mantle geochemistry of the Earth’s precursor was fundamentally transformed to that which underpinned all later geological events, notwithstanding the formation of the protoEarth about 4.57 Ga ago, I now think of the Moon-forming event as our homeworld’s ‘Year Zero’. It was the ‘beginning’ of which James Hutton reckoned there was ‘no vestige’. Any modern geochemist might comment, ‘Well, there must be some kind of signature!’, but what that might be and when it happened are elusive, to say the least. One way of looking for answers is, as with so many thorny issues these days, to make a mathematical model. James Connelly and Martin Bizzarro of the University of Copenhagen, Denmark, have designed one based on the fact that one of the volatile elements that must have been partially ‘blown off’ by such a collision is lead and, of course, that is an element with several isotopes that are daughters of long-term decay of radioactive uranium and thorium (Connelly, J.N. & Bizzarro, M. 2016. Lead isotope evidence for a young formation age of the Earth–Moon system. Earth and Planetary Science Letters, v. 452, p. 36-43. doi:10.1016/j.epsl.2016.07.010).
Loss of volatile daughter isotopes of Pb produced by the decay schemes of highly refractory isotopes of U and Th would have reset the U-Pb and Th-Pb isotopic systems and therefore the radiogenic ‘clocks’ that depend on them in the same way as melting or high-temperature metamorphism resets the simpler 87Rb-87Sr decay scheme. Each radioactive U isotope has a different decay rate that produces a different Pb isotope daughter (235U Þ 207Pb; 238U Þ 206Pb, so it is possible to devise means of using present-day values of ratios between Pb isotopes, such as 207Pb/206Pb, 206Pb/204Pb and 207Pb/204Pb, to work back to such a ‘closure’ time. In short, that is the approach used by Connelly and Bizzarro. The most complicated bit of that geochemical ruse is estimating values of the ratios for the Earth’s modern mantle and for the Solar system in general – a procedure based on what we can actually measure: lots of mantle-derived basalts and lots of meteorites. Cutting out some important caveats, the result of their model is quite a surprise: ‘Year Zero’ on their account was between 4426 and 4417 Ma years ago, which is astonishingly precise. And it is pretty close to the measured age of the of lunar Highland anorthosites – products of fractional crystallisation of the Moon’s early magma ocean – and also to that of the oldest zircons on Earth. But is also about 60 Ma later than previous estimates
The Connelly and Bizzarro paper follows hard on the heels of another with much the same objective (Snape, J.F. and 8 others 2016. Lunar basalt chronology, mantle differentiation and implications for determining the age of the Moon. Earth and Planetary Science Letters, v. 451, p. 149-158. doi.org/10.1016/j.epsl.2016.07.026). Once again omitting a great deal of argument, Snape and colleagues end up with an age for the isotopic resetting of the lunar mantle of 4376 Ma to the nearest 18 Ma; i.e. an age significantly different from that arrived at by Connelly and Bizzarro. So the answer to the question, ‘When was there a vestige of a beginning?’ is, ‘It depends on the model’… Thankfully, neither estimate for ‘Year Zero’ has much bearing on the big, practical questions, such as, ‘When did life form?’, ‘Has there always been plate tectonics?’ | 0.826522 | 3.693163 |
So said researchers in their 2015 study which had that title. Then a third planet was seen.
In the abstract they say:
Methods. Our search through two separate pipelines led to the independent discovery of K2-19b and c, a two-planet system of Neptune-sized objects (4.2 and 7.2 R⊕), orbiting a K dwarf extremely close to the 3:2 mean motion resonance. The two planets each show transits, sometimes simultaneously owing to their proximity to resonance and the alignment of conjunctions.
A third planet ‘d’ even nearer to the star was later discovered, and since the data had a general update published only a few days ago (see exoplanet.eu) we can give their observations these new orbit numbers:
19 d = 47.6539 days
6 b = 47.5332
4 c = 47.5972
Translating to conjunctions:
6 – 4 = 2 b-c
19 – 6 = 13 d-b
19 – 4 = 15 d-c
2 and 13 are Fibonacci numbers , with 15 being the sum of the two ‘neighbour’ pairs, as it has to be.
K2-19 b, the middle planet in terms of distance from the star, is the heaviest having ~3 times (2.997) the mass of c and slightly more than 3 times that of d, so b:c ratios are 3:1 mass and 3:2 orbits.
The 3:2 resonance referred to in the study is discussed in section 7.3: Hill stability.
In their caption to Figure 9 the authors say:
the 3:2 MMR* might act as a crucial protection mechanism to ensure the system’s long-term stability on the main sequence. [*mean motion resonance]
– – –
Astronomy & Astrophysics: One of the closest exoplanet pairs to the 3:2 mean motion resonance: K2-19b and c [2015 research article]
via Tallbloke’s Talkshop
November 2, 2019 at 09:34AM | 0.809232 | 3.22756 |
There's a puzzling mystery going on in the universe. Measurements of the rate of cosmic expansion using different methods keep turning up disagreeing results. The situation has been called a "crisis."
The problem centers on what's known as the Hubble constant. Named for American astronomer Edwin Hubble, this unit describes how fast the universe is expanding at different distances from Earth. Using data from the European Space Agency's (ESA) Planck satellite, scientists estimate the rate to be 46,200 mph per million light-years (or, using cosmologists' units, 67.4 kilometers/second per megaparsec). But calculations using pulsating stars called Cepheids suggest it is 50,400 mph per million light-years (73.4 km/s/Mpc).
If the first number is right, it means scientists have been measuring distances to faraway objects in the universe wrong for many decades. But if the second is correct, then researchers might have to accept the existence of exotic, new physics. Astronomers, understandably, are pretty worked up about this discrepancy.
What is a layperson supposed to make of this situation? And just how important is this difference, which to outsiders looks minor? In order to get to the bottom of the clash, Live Science called in Barry Madore, an astronomer at the University of Chicago and a member of one of the teams undertaking measurements of the Hubble constant.
The trouble starts with Edwin Hubble himself. Back in 1929, he noticed that more-distant galaxies were moving away from Earth faster than their closer-in counterparts. He found a linear relationship between the distance an object was from our planet and the speed at which it was receding.
"That means something spooky is going on," Madore told Live Science. "Why would we be the center of the universe? The answer, which is not intuitive, is that [distant objects are] not moving. There's more and more space being created between everything."
Hubble realized that the universe was expanding, and it seemed to be doing so at a constant rate — hence, the Hubble constant. He measured the value to be about 342,000 miles per hour per million light years (501 km/s/Mpc) — almost 10 times larger than what is currently measured. Over the years, researchers have refined that rate.
Things got weirder in the late 1990s, when two teams of astronomers noticed that distant supernovas were dimmer, and therefore farther away, than expected, said Madore. This indicated that not only was the universe expanding, but it was also accelerating in its expansion. Astronomers named the cause of this mysterious phenomenon dark energy.
Having accepted that the universe was doing something strange, cosmologists turned to the next obvious task: measuring the acceleration as accurately as possible. By doing this, they hoped to retrace the history and evolution of the cosmos from start to finish.
Madore likened this task to walking into a racetrack and getting a single glimpse of the horses running around the field. From just that bit of information, could somebody deduce where all the horses started and which one of them would win?
That kind of question may sound impossible to answer, but that hasn't stopped scientists from trying. For the last 10 years, the Planck satellite has been measuring the cosmic microwave background, a distant echo of the Big Bang, which provides a snapshot of the infant universe 13 billion years ago. Using the observatory's data, cosmologists could ascertain a number for the Hubble constant with an extraordinarily small degree of uncertainty.
"It's beautiful," Madore said. But, "it contradicts what people have been doing for the last 30 years," said Madore.
Over those three decades, astronomers have also been using telescopes to look at distant Cepheids and calculate the Hubble constant. These stars flicker at a constant rate depending on their brightness, so researchers can tell exactly how bright a Cepheid should be based on its pulsations. By looking at how dim the stars actually are, astronomers can calculate a distance to them. But estimates of the Hubble constant using Cepheids don't match the one from Planck.
The discrepancy might look fairly small, but each data point is quite precise and there is no overlap between their uncertainties. The differing sides have pointed fingers at one another, saying that their opponents have included errors throwing off their results, said Madore.
But, he added, each result also depends on large numbers of assumptions. Going back to the horse-race analogy, Madore likened it to trying to figure out the winner while having to infer which horse will get tired first, which will gain a sudden burst of energy at the end, which will slip a bit on the wet patch of grass from yesterday's rain and many other difficult-to-determine variables.
If the Cepheids teams are wrong, that means astronomers have been measuring distances in the universe incorrectly this whole time, Madore said. But if Planck is wrong, then it's possible that new and exotic physics would have to be introduced into cosmologists' models of the universe, he added. These models include different dials, such as the number of types of subatomic particles known as neutrinos in existence, and they are used to interpret the satellite's data of the cosmic microwave background. To reconcile the Planck value for the Hubble constant with existing models, some of the dials would have to be tweaked, Madore said, but most physicists aren’t quite willing to do so yet.
Hoping to provide another data point that could mediate between the two sides, Madore and his colleagues recently looked at the light of red giant stars. These objects reach the same peak brightness at the end of their lives, meaning that, like with the Cepheids, astronomers can look at how dim they appear from Earth to get a good estimate of their distance and, therefore, calculate the Hubble constant.
The results, released in July, provided a number squarely between the two prior measurements: 47,300 mph per million light-years (69.8 km/s/Mpc). And the uncertainty contained enough overlap to potentially agree with Planck's results.
But researchers aren't popping their champagne corks yet, said Madore. "We wanted to make a tie breaker," he said. "But it didn't say this side or that side is right. It said there was a lot more slop than everybody thought before."
Other teams have weighed in. A group called H0 Lenses in COSMOGRAIL's Wellspring (H0LICOW) is looking at distant bright objects in the early universe called quasars whose light has been gravitationally lensed by massive objects in between us and them. By studying these quasars, the group recently came up with an estimate closer to the astronomers' side. Information from the Laser Interferometer Gravitational-Wave Observatory (LIGO), which looks at gravitational waves from crashing neutron stars, could provide another independent data point. But such calculations are still in their early stages, said Madore, and have yet to reach full maturity.
For his part, Madore said he thinks the middle number between Planck and the astronomers' value will eventually prevail, though he wouldn't wager too much on that possibility at the moment. But until some conclusion is found, he would like to see researchers' attitudes toned down a bit.
"A lot of froth has been put on top of this by people who insist they're right," he said. "It's sufficiently important that it needs to be resolved, but it's going to take time."
- The 12 Strangest Objects in the Universe
- From Big Bang to Present: Snapshots of Our Universe Through Time.
- The 11 Biggest Unanswered Questions About Dark Matter
Originally published on Live Science. | 0.836046 | 3.910099 |
As you may have heard, exoplaneteers Michel Mayor and Didier Queloz shared this year’s Nobel Prize in Physics for the first discovery of an extrasolar planet around a Sun-like star.
These discoveries are now so commonplace, with thousands of exoplanets now known, it’s hard to remember back when each individual discovery was groundbreaking. So to reflect on how far we’ve come, we went back to Mayor and Queloz’s original 51 Peg b discovery paper at our research group meeting on Friday.
Even after decades of exoplanet discoveries, their paper is a gem, with bold scientific claims buttressed by meticulous observational data. As a gas giant circling its host star every 4 days, 51 Peg b presented a clear challenge to our notions of planet formation which said gas planets like Jupiter can only form very far from their host stars. Even so, Mayor and Queloz built a nearly bullet-proof argument for their discovery, and their results were confirmed within a week of their announcement.
But re-reading the paper this week, I was especially struck by how much our understanding of exoplanetary systems has changed and how many of their arguments, perfectly plausible at the dawn of exoplanet science, have been turned on their head — literally.
A Wobbly Rainbow
To find 51 Peg b, Mayor and Queloz used what has now become a standard exoplanet discovery technique, radial velocity measurements. The animation above shows how this works: as a planet circles its host star, the star also revolves around the planet. If the planet’s orbit is not too far from edge-on as seen from Earth, the Doppler effect will raise or lower the pitch (i.e., color) of the star’s spectral features as the star pirouettes toward and away from Earth.
With this technique, Mayor and Queloz detected the teeny gravitational tug of 51 Peg b on its host star to find the planet and estimate its mass (about half Jupiter’s).
As powerful as this technique is, though, if the planet’s orbit is not exactly edge-on as seen from Earth, the mass inferred is smaller than the actual mass. And so when Mayor and Queloz detected 51 Peg’s gravitational gumboot, they couldn’t be sure whether they had detected a gas giant in an orbit nearly edge-on or a small star in an orbit nearly face-on.
To address this uncertainty, Mayor and Queloz measured the star’s rotation and found the equator was nearly edge-on to Earth. Since the orbits for solar system planets are all nearly aligned with the Sun’s equator, it seemed obvious that 51 Peg b’s was as well.
So the inferred radial velocity mass must be close to the actual mass, and spectral oscillations were caused by a planet.
Later observations of 51 Peg b confirmed this alignment assumption. But we now know that many exoplanet orbits are severely misaligned compared to their stars’ equators. In some cases, the planets actually orbit at a right angle or even in the opposite direction to their stars’ rotation.
The reasons for these misalignments are not clear — in some cases, the stars might undergo an early phase of chaotic rotational evolution. In other cases, the planets might start out in well-aligned orbits, but gravitational interactions among planets or with a distant star can produce misalignment.
It Could (and Did) Happen Here
Even though 51 Peg b seems not to have experienced this misalignment, its discovery forced astronomers to reconsider the canonical wisdom of planet formation and think outside of the box about where we might find planets. Once it became clear that Jupiter-sized planets could occupy very short-period orbits, radial velocity observers sifted their data again and found dozens of planetary signals hiding where no one had thought to look before.
And the dramatic orbital evolution later invoked to explain 51 Peg b’s very small orbit prompted astronomers to re-visit previously puzzling aspects of our own solar system. Now we think the same kinds of prepubescent shake-ups that occur regularly in extrasolar systems probably also happened here, perhaps explaining why Mars is so much smaller than Earth and unlikely arrangements of orbits in the Kuiper Belt.
51 Peg b’s Legacy
51 Peg b is sometimes mistakenly called the first exoplanet discovered, but, in fact, the first confirmed exoplanet system was discovered in 1992 orbiting the pulsar PSR B1257+12. However, as the first planet orbiting a Sun-like star, 51 Peg b definitively demonstrated the existence of planetary systems resembling our own.
And here, 25 years after its discovery, we know planetary systems are common, with on average at least one planet for every star in our galaxy. The awarding of the Nobel Prize to Mayor and Queloz (as flawed as the Nobel awards are) is a rightful recognition of the profound importance of their work. Indeed, the discovery of 51 Peg b was not just a stunning testament to human achievement — it’s a response to the age-old question, “Are we alone in the Universe?”. Each exoplanet discovery since then whispers the answer, “No, we are not.“ | 0.918211 | 3.931592 |
¡SkyCaramba! Weekly astronomy blog for the week ending July 27, 2013
During the next two weeks or so, you may see up to 20 bright yellow meteors per hour that trace back to a point near a star named Skat. These are the Delta Aquarid meteors. The star Skat is also called δ Aquarii.
This meteor shower peaks on or about July 29. That’s when Earth passes closest to or through the dust trail responsible for it. Astronomers think that’s Comet 96P/Machholz. David Machholz discovered the comet in 1986. In the years since, scientists who analyzed its orbit have come to suspect Comet Machholz is the parent of the Delta Aquarids.
Comet Machholz orbits the sun every five years, going closer to the sun than Mercury and farther from it than Jupiter during that time. The comet was closest to the sun a year ago and will be again in October 2017. If the Delta Aquarids come from the 96P/Machholz trail, this could be a good year for them.
This is a good southern hemisphere meteor shower. It’s pretty well observed in the northern hemisphere too. Look from midnight to dawn. If you see a meteor, try to determine if the track it makes would extend all the way back to the star Skat. Skat is close to a more well known star named Fomalhaut. It’s also somewhat close to the Great Square of Pegasus.
Less than 10% of Delta Aquarids leave persistent, or glowing, trails. Those that glow for a second or two are easier to use for determining where they seem to radiate from. Since most won’t be so accommodating, you’ll have to observe carefully.
A last quarter moon will make it hard to see most of these meteors on the peak date this year. But you may still see plenty of them in early August while the moon wanes and enters new moon phase.
Links to more information about the Delta Aquarid meteor shower. | 0.828598 | 3.092044 |
MARS ATMOSPHERE & STORMS
Irene Baron: www.irenebaron.com
In September of 2015, the Mars Atmosphere and Volatile Evolution mission (MAVEN) discovered high-altitude dust surrounding the planet Mars. According to an 18 April 2015 Science News article by Christopher Crockett, planetary scientist Bruce Jakosky (of the University of Colorado at Boulder and working with the MAVEN project) was quoted as saying “This was completely unexpected.“
My question is, “Why would that be unexpected?”
In my early astronomy instruction I was taught that atmosphere had been described as “that gaseous envelope of matter that surrounds the Sun and in which the planets are imbedded.” It would be logical to think that planets with greater gravity would have thicker atmospheres. Mars has gravity less than Earth. Because of less gravitational attraction to objects, it seems logical that nano-particles suspended within the Martian atmosphere would not be pulled to the planet as quickly as the particles suspended within Earth’s atmosphere.
Over the years, equipment used to study objects in outer space have become more efficient and better constructed. Many years ago I read a science journal article, most likely about a Mariner craft, which discussed a Martian planet-wide dust storm with high velocity winds obscuring the surface. Due to the rate at which the storm covered the planet, the article stated the winds were estimated to be over 600-miles per hour. You can see from the Hubble photograph below a picture of Mars with and without a global wind/dust storm. The wind speed fact impacted on my memory as I compared that wind speed with those of Earth hurricanes and tornadoes.
Note the picture of Mars experiencing a dust storm and with clear skies as found at: http://science.nasa.gov/science-news/science-at-nasa/2001/ast11oct_2/. The Hubble Space Telescope took these pictures on 26 June 2001 and 4 September 2001 which illustrate how the planet could become enshrouded with dust. To think that all of it would quickly fall to the surface would be rather short sighted. Take for example the 7-cubic miles of dust and an estimated 20-million tons of sulfur which was shot into the Earth’s atmosphere by the 1883 volcano Krakatau located in Indonesia. That material made the sunsets blood red for over eight years. There are probably remnants of that eruption still orbiting Earth in the upper atmosphere.
The fastest tornado wind speed on Earth was clocked at ONLY 318-miles per hour in 1999. http://usatoday30.usatoday.com/weather/tornado/wtwur318.htm. Short lived Earth tornados have only half the velocity of a violent Martian wind storm. NASA reports that Viking Landers in the 1970’s (http://quest.nasa.gov/aero/planetary/mars.html ) recorded average wind speeds of 20-miles per hour with a maximum of 60-miles per hour. If the earlier wind speed of 600-miles per hour was correct, NASA must plan for them, even if they are “100-year storms.” Such sustained storm winds would destroy most human habitats constructed on the surface of that planet. So, where would humans live?
I realize that early data obtained from outer space measurements may not have been as accurate as data of today with currently used better equipment and telescopes. If such an extreme storm does occasionally occur and is planet-wide, humans could not safely live on Mars unless their habitat was constructed in an area protected by the wind or underground. On Earth hurricanes and tornadoes causing death and destruction are short in duration. A normal storm on Mars with lower wind speeds would be survivable but not the extreme storm with sustained winds hundreds of miles per hour lasting several months.
It would be interesting to have deep Martian core samples to analyze past sedimentation from storms. It is possible that nano-sized debris particles blown into the atmosphere during Martian storms may be suspended there for centuries. The gravity of Mars, as mentioned earlier, would allow the particle suspension over a much longer time than those in Earth’s atmosphere.
The larger atmospheric dust particles will have fallen out to create sediment layers planet wide. By analyzing a deep Martian core sample perhaps geologists could determine frequency, severity and longevity of Martian storms. The surface of the planet with its constant and prevailing winds would not show the true measure of dust accumulation from storms. Perhaps it would be best to extract core samples located within a meteor crater where the dust falling from the atmosphere would be more protected.
My first thought was to drill for core samples of Hellas Planitia or a smaller meteor crater. Not only would you obtain more accurate core samples from an area not experiencing the prevailing Martian winds, but humans may be able to better survive extreme storms if protected by crater walls. If you travel down into the depths of Earth’s Grand Canyon you find the temperature increases. The Martian crater basins may also create warmer temperatures for humans to enjoy on the cold planetary surface. Perhaps build the habitat along a protected edge of the 4-mile deep and 1,300-mile wide Hellas basin.
To determine the history of such dust storms scientists may want to obtain some drill cores within Hellas crater. The different wind storms would leave deposits of dust material within the 4-mile deep crater. Such core samples may provide evidence on the sedimentation from airborne material. From that data the frequency of severe storms on the Martian surface may be determined. With that data they may provide a hypothesis as to how often the most severe storms occur.
The only wind patterns I’ve seen within Hellas during winter in that hemisphere showed a high pressure area in the center with winds moving outward to the high walls. Below is the DSO/NASA Astrophysics data diagram by Antoniadi of counterclockwise wind directions in the Martian southern hemisphere. Note that winds in the northern hemisphere are primarily clockwise. There is a high pressure area centered in Hellas crater with air being pushed outward toward the edges.
With analysis of Hellas there may be areas of large enough rock masses to create shelter from Martian winds. Hellas is rugged and deep, but it is so large there will be microclimates within it. I would like to see more climatological data from within Hellas. It may be that the edges of Hellas crater may be more protected from horizontal storm winds from the land above it. Yet there may be more severe downdrafts.
The Martian atmosphere may be similar to that of Earth when discussing optical clarity. When Earth's atmosphere and the particles it contains is discussed I think back to one of the early NASA flights. There was one astronaut on board the rocket leaving Florida. It could easily be seen by spectators and by cameras. The rocket looked beautiful from Earth. When a NASA engineer asked the astronaut to describe how the NASA site looked to him, he replied it couldn't be seen due to the cloud cover. The engineers were confounded as they saw no clouds from Earth. That's when they discovered the one-way optical clarity of the high altitude, cirro-stratus clouds made from ice crystals. From Earth if there are no cirro-stratus clouds the sky will appear to be a dark blue. It is rare to see such deep blue, clear skies. Jim Wark, an internationally famous aerial photographer ( http://airphotona.com ) once commiserated with me that haze and smog free days in the United States are rare. He refers to haze as wildfire smoke, dust, moisture, ozone, pet dander and "all that other atmospheric stuff." He said haze and smog free days occurred in the 1970s & 80s 5-6 times per year and were later reduced to only 2-3 days per year. When they did occur, he took opportunities to fly his airplane around the United States taking rare CLEAR pictures of our beautiful country. Besides being an excellent pilot and photographer, he's a true gentleman. Check out his site to enjoy the United States from his perspective.
To help readers learn more about Mars formations I have included the cut out below. Copy it to a word document and enlarge it to work with more easily. Enjoy! It was obtained from the United States Geological Survey. | 0.907162 | 3.649249 |
In July of 2020, NASA will place an unnamed rover (currently known as Mars 2020) on top an Atlas V rocket in Cape Canaveral, Florida. This car sized rover will be blasted off Earth and shot towards our neighbouring planet, Mars. It will travel through deep space for six months before arriving at the red planet. It will break through Mars’ thin atmosphere and land in a region known as Jeziro crater in February 2021. Mars 2020 will join a suite of spacecraft already at Mars including its predecessor Curiosity and six orbiting satellites. In recent years, Mars has been a favourable target for exploration, with discoveries of seasonal water flows and spikes of methane piquing scientists’ interest in the search for life beyond Earth. This neighbouring world has captivated our imagination for millennia, and we are now closer than ever to answering whether life once existed on Mars…or potentially even exists there today.
Mars was once thought to be an Earth-like world before the first spacecraft provided us with a close-up view. Observations by astronomers in the 1800s reportedly showed ‘canals’ on Mars, believed to have been constructed by life forms to transport water across the planet for irrigation and agriculture. Newspapers at the time even went as far as speculating about Martian life as if it has been proven. This idea was the inspiration behind H.G. Wells novel War of the Worlds, telling of an invasion of Earth by aliens who were fleeing Mars. The idea bordered on fantasy, but it quickly fell out of favour when further examination of the planet in 1909 during a planetary opposition with Earth showed that there were no canals to be seen anywhere on the planet; it was merely an optical illusion of different surface features. After the space race in the 1960s, both the USA and then Soviet Union quickly turned their gaze towards Mars. Both began sending probes to fly-by the red planet, with many failures in the beginning. The American Mariner 4 probe conducted the first successful fly-by in 1965, beaming back the first ever close-up images of the Martian surface. It showed us Mars was a heavily cratered, dry, and seemingly dead world. This confirmed what many scientists had begun speculating over the years; life on Mars was seemingly impossible.
Although the first images did not depict a lush, water-laden world as scientists had once hoped, many missions continued to be sent to Mars as we began to discover more about this foreign world. The first surface missions like Viking were stationary landers that did not move and were confined to studying the area directly around them. Sojourner became the first successful rover after landing in 1997. Although a proof of concept that did not travel far, this mission showed us that rovers were a viable means of exploration, meaning we could explore larger areas and direct rovers to specific areas of interest for scientists. The hugely successful Spirit and Opportunity rovers followed, both landing in 2004. These twin rovers far outlived their designed lifespans and gave us a wealth of new information on Mars. Opportunity lasted an incredible 14 years despite being designed to last three months and travelled over 45km across the Martian surface. NASA’s latest rover to the red planet is Curiosity, which landed in 2012. It too has outlived its expected life span of two years as it continues to explore to this day. Curiosity is the most complex rover ever sent to Mars with a suite of scientific instruments including 17 cameras and a laser used to vaporise rock. In recent years, Curiosity has detected peaks of methane in the Martian air, alluding to the possibility that this could be caused by organic and biological processes like here on Earth. We know that Mars today is not the water-world we hoped it was, but decades of successful Mars missions have shown us it was once very Earth-like with oceans of liquid water. This makes it the most likely candidate to find evidence of past or present life in our Solar System.
The new rover
The design of Mars 2020 is based largely on the already successful design of Curiosity. It will use the same EDL systems (Entry, Descent, Landing) that Curiosity did in 2012, as well as looking visually very similar. Mars 2020 is designed to specifically search for astrobiology and signs of past habitability on Mars and will carry more complex instruments to search for signs of possible life. One instrument called Mars Oxygen ISRU Experiment (or MOXIE) is a technology demonstration that will produce oxygen on the Martian surface for the first time. This is essential for the eventual humans who will soon follow. Mars 2020 will also carry a small helicopter known as MHS. This will be the first ever helicopter to fly on another world, and it will scout out areas for the rover to explore in advance.
Landing any spacecraft on another planet is no easy task, and the engineers who worked on this mission will be watching nervously as Mars 2020 begins the process of landing in 2021. Tens of thousands of people watched with excitement when Curiosity landed in 2012, and it’s no doubt that Mars 2020 will bring in even more anticipation as we send off our latest robotic pioneer to its new home.
Spacecraft play a vital role in our exploration of cosmos in our search for life beyond Earth. These robots do the hard work for us by scouting out the conditions, finding clues about past life, and pointing us in the right direction. We are closer than ever before in answering the question of whether we are alone or not. The Mars 2020 rover may not be able answer the question point blank, but it will tell us where to look when we finally take our first steps on another planet ourselves in the near future.
Images: TOP: Curiosity watches a sunset on Mars while exploring Gale crater; ABOVE LEFT: The Curiosity rover and its parachute seen descending towards Mars, taken from the orbiter MRO; ABOVE RIGHT: Mars 2020 carries a suite of complex scientific instruments including the first ever helicopter to fly on another world.
Josh Kirkley, Astronomy Educator | 0.862296 | 3.345303 |
NASA’s Chandra Xray telescope, orbiting the Earth at a speed of 1.7 kilometers per second, has been pointed at an exoplanet for the first time, giving astronomers their first glimpse of another world at Xray wavelengths. They not only found that the Jupiter sized world has a thick atmosphere, but also discovered a previously undiscovered star orbiting in the same system.
The planet in star system HD 189733 was first discovered in 2005 by using the radial velocity method. Unusually, the planet’s orbit lines up neatly with our own line of sight, so that it passes in front of its star when viewed from Earth. Although these transits had been seen before, a team of astronomers led by Katja Poppenhaeger of Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusets used Chandra and historical data from the European Space Agency’s XMM Newton telescope to watch them in the Xray spectrum. They not only discovered a previously hidden second star in the system, but found that the planet appeared some three times larger in Xray than in visible light.
HD 189733 is found 63 light years away from the Sun,in the constellation Vulpecula (the fox). HD 189733b (the planet) is a “Hot Jupiter”, meaning that while it’s size is comparable to Jupiter, it orbits so close to the star that its year is only a few days long and it’s atmosphere is superheated to the point of boiling away into space. Scientists estimate that the planet loses between 100 and 600 million kilograms of mass each second, and that it is this factor that scientists suspect is causing the apparent size of the planet to vary according between different types of observation. “The extended atmosphere of this planet makes it a bigger target for high-energy radiation from its star, so more evaporation occurs,” said team member Scott Wolk
“The X-ray data suggest there are extended layers of the planet’s atmosphere that are transparent to optical light but opaque to X-rays,” says Jurgen Schmitt of Hamburger Sternwarte in Hamburg, Germany. “However, we need more data to confirm this idea.” The idea is that the atmosphere of the planet is rich in heavy elements like carbon, nitrogen, oxygen and iron (what astronomers call ‘metals’), and the gaseous forms of these metals block the passage of Xrays. The size estimate is based on how much the light of the star dims during a transit, so if the atmosphere is more opaque in Xrays than in visible light, the planet will appear larger to an Xray telescope than to an optical telescope.
The other discovery, of a companion star, presents its own mysteries. This new star is small, dim and red, and would have formed from the same gas cloud as the primary star, at the same time. However, its spectrum suggests that it’s some 3 to 3.5 billion years younger, because it spins faster, is more magnetic, and is extremely bright in Xrays.
“This star is not acting its age, and having a big planet as a companion may be the explanation,” said Poppenhaeger. “It’s possible this hot Jupiter is keeping the star’s rotation and magnetic activity high because of tidal forces, making it behave in some ways like a much younger star.”
The paper is available online at: http://arxiv.org/abs/1306.2311 | 0.868399 | 4.028086 |
Rehearsal time for NASA's asteroid sampling spacecraft
In August, a robotic spacecraft will make NASA's first-ever attempt to descend to the surface of an asteroid, collect a sample, and ultimately bring it safely back to Earth. In order to achieve this challenging feat, the OSIRIS-REx mission team devised new techniques to operate in asteroid Bennu's microgravity environment—but they still need experience flying the spacecraft in close proximity to the asteroid in order to test them. So, before touching down at sample site Nightingale this summer, OSIRIS-REx will first rehearse the activities leading up to the event.
On Apr. 14, the mission will pursue its first practice run—officially known as "Checkpoint" rehearsal—which will also place the spacecraft the closest it's ever been to Bennu. This rehearsal is a chance for the OSIRIS-REx team and spacecraft to test the first steps of the robotic sample collection event.
During the full touchdown sequence, the spacecraft uses three separate thruster firings to make its way to the asteroid's surface. After an orbit departure burn, the spacecraft executes the Checkpoint maneuver at 410 ft (125 m) above Bennu, which adjusts the spacecraft's position and speed down toward the point of the third burn. This third maneuver, called "Matchpoint," occurs at approximately 164 ft (50 m) from the asteroid's surface and places the spacecraft on a trajectory that matches the rotation of Bennu as it further descends toward the targeted touchdown spot.
The Checkpoint rehearsal allows the team to practice navigating the spacecraft through both the orbit departure and Checkpoint maneuvers, and ensures that the spacecraft's imaging, navigation and ranging systems operate as expected during the first part of the descent sequence. Checkpoint rehearsal also gives the team a chance to confirm that OSIRIS-REx's Natural Feature Tracking (NFT) guidance system accurately updates the spacecraft's position and velocity relative to Bennu as it descends towards the surface.
Checkpoint rehearsal, a four-hour event, begins with the spacecraft leaving its safe-home orbit, 0.6 miles (1 km) above the asteroid. The spacecraft then extends its robotic sampling arm—the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) – from its folded, parked position out to the sample collection configuration. Immediately following, the spacecraft slews, or rotates, into position to begin collecting navigation images for NFT guidance. NFT allows the spacecraft to autonomously guide itself to Bennu's surface by comparing an onboard image catalog with the real-time navigation images taken during descent. As the spacecraft descends to the surface, the NFT system updates the spacecraft's predicted point of contact depending on OSIRIS-REx's position in relation to Bennu's landmarks.
Before reaching the 410-ft (125-m) Checkpoint altitude, the spacecraft's solar arrays move into a "Y-wing" configuration that safely positions them away from the asteroid's surface. This configuration also places the spacecraft's center of gravity directly over the TAGSAM collector head, which is the only part of the spacecraft that will contact Bennu's surface during the sample collection event.
In the midst of these activities, the spacecraft continues capturing images of Bennu's surface for the NFT navigation system. The spacecraft will then perform the Checkpoint burn and descend toward Bennu's surface for another nine minutes, placing the spacecraft around 243 ft (75 m) from the asteroid—the closest it has ever been.
Upon reaching this targeted point, the spacecraft will execute a back-away burn, then return its solar arrays to their original position and reconfigure the TAGSAM arm back to the parked position. Once the mission team determines that the spacecraft successfully completed the entire rehearsal sequence, they will command the spacecraft to return to its safe-home orbit around Bennu.
Following the Checkpoint rehearsal, the team will verify the flight system's performance during the descent, and that the Checkpoint burn accurately adjusted the descent trajectory for the subsequent Matchpoint burn.
The mission team has maximized remote work over the last month of preparations for the checkpoint rehearsal, as part of the COVID-19 response. On the day of rehearsal, a limited number of personnel will command the spacecraft from Lockheed Martin Space's facility, taking appropriate safety precautions, while the rest of the team performs their roles remotely.
The mission is scheduled to perform a second rehearsal on Jun. 23, taking the spacecraft through the Matchpoint burn and down to an approximate altitude of 82 ft (25 m). OSIRIS-REx's first sample collection attempt is scheduled for Aug. 25. | 0.808902 | 3.303259 |
Scientific experiments are designed to determine facts about our world. But in complicated analyses, there’s a risk that researchers will unintentionally skew their results to match what they were expecting to find. To reduce or eliminate this potential bias, scientists apply a method known as “blind analysis.”
Blind studies are probably best known from their use in clinical drug trials, in which patients are kept in the dark about—or blind to—whether they’re receiving an actual drug or a placebo. This approach helps researchers judge whether their results stem from the treatment itself or from the patients’ belief that they are receiving it.
Particle physicists and astrophysicists do blind studies, too. The approach is particularly valuable when scientists search for extremely small effects hidden among background noise that point to the existence of something new, not accounted for in the current model. Examples include the much-publicized discoveries of the Higgs boson by experiments at CERN’s Large Hadron Collider and of gravitational waves by the Advanced LIGO detector.
“Scientific analyses are iterative processes, in which we make a series of small adjustments to theoretical models until the models accurately describe the experimental data,” says Elisabeth Krause, a postdoc at the Kavli Institute for Particle Astrophysics and Cosmology, which is jointly operated by Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory. “At each step of an analysis, there is the danger that prior knowledge guides the way we make adjustments. Blind analyses help us make independent and better decisions.”
Krause was the main organizer of a recent workshop at KIPAC that looked into how blind analyses could be incorporated into next-generation astronomical surveys that aim to determine more precisely than ever what the universe is made of and how its components have driven cosmic evolution.
Black boxes and salt
One outcome of the workshop was a finding that there is no one-size-fits-all approach, says KIPAC postdoc Kyle Story, one of the event organizers. “Blind analyses need to be designed individually for each experiment.”
The way the blinding is done needs to leave researchers with enough information to allow a meaningful analysis, and it depends on the type of data coming out of a specific experiment.
A common approach is to base the analysis on only some of the data, excluding the part in which an anomaly is thought to be hiding. The excluded data is said to be in a “black box” or “hidden signal box.”
Take the search for the Higgs boson. Using data collected with the Large Hadron Collider until the end of 2011, researchers saw hints of a bump as a potential sign of a new particle with a mass of about 125 gigaelectronvolts. So when they looked at new data, they deliberately quarantined the mass range around this bump and focused on the remaining data instead.
They used that data to make sure they were working with a sufficiently accurate model. Then they “opened the box” and applied that same model to the untouched region. The bump turned out to be the long-sought Higgs particle.
That worked well for the Higgs researchers. However, as scientists involved with the Large Underground Xenon experiment reported at the workshop, the “black box” method of blind analysis can cause problems if the data you’re expressly not looking at contains rare events crucial to figuring out your model in the first place.
LUX has recently completed one of the world’s most sensitive searches for WIMPs—hypothetical particles of dark matter, an invisible form of matter that is five times more prevalent than regular matter. LUX scientists have done a lot of work to guard LUX against background particles—building the detector in a cleanroom, filling it with thoroughly purified liquid, surrounding it with shielding and installing it under a mile of rock. But a few stray particles make it through nonetheless, and the scientists need to look at all of their data to find and eliminate them.
For that reason, LUX researchers chose a different blinding approach for their analyses. Instead of using a “black box,” they use a process called “salting.”
LUX scientists not involved in the most recent LUX analysis added fake events to the data—simulated signals that just look like real ones. Just like the patients in a blind drug trial, the LUX scientists didn’t know whether they were analyzing real or placebo data. Once they completed their analysis, the scientists that did the “salting” revealed which events were false.
A similar technique was used by LIGO scientists, who eventually made the first detection of extremely tiny ripples in space-time called gravitational waves.
High-stakes astronomical surveys
The Blind Analysis workshop at KIPAC focused on future sky surveys that will make unprecedented measurements of dark energy and the Cosmic Microwave Background—observations that will help cosmologists better understand the evolution of our universe.
Dark energy is thought to be a force that is causing the universe to expand faster and faster as time goes by. The CMB is a faint microwave glow spread out over the entire sky. It is the oldest light in the universe, left over from the time the cosmos was only 380,000 years old.
To shed light on the mysterious properties of dark energy, the Dark Energy Science Collaboration is preparing to use data from the Large Synoptic Survey Telescope, which is under construction in Chile. With its unique 3.2-gigapixel camera, LSST will image billions of galaxies, the distribution of which is thought to be strongly influenced by dark energy.
“Blinding will help us look at the properties of galaxies picked for this analysis independent of the well-known cosmological implications of preceding studies,” DESC member Krause says. One way the collaboration plans on blinding its members to this prior knowledge is to distort the images of galaxies before they enter the analysis pipeline.
Not everyone in the scientific community is convinced that blinding is necessary. Blind analyses are more complicated to design than non-blind analyses and take more time to complete. Some scientists participating in blind analyses inevitably spend time looking at fake data, which can feel like a waste.
Yet others strongly advocate for going blind. KIPAC researcher Aaron Roodman, a particle-physicist-turned-astrophysicist, has been using blinding methods for the past 20 years.
“Blind analyses have already become pretty standard in the particle physics world,” he says. “They’ll be also crucial for taking bias out of next-generation cosmological surveys, particularly when the stakes are high. We’ll only build one LSST, for example, to provide us with unprecedented views of the sky.” | 0.82286 | 3.382088 |
Today, we think of Mars as having a cold, dry, and desolate environment (because it does).
But that was not always the case. Four billion years ago, while our Sun was still in its infancy, Mars was covered with water.
Back then, it had a much thicker atmosphere, which kept the planet warm enough for water to exist in its liquid form. Some estimates say that at one point, up to 1640 ft (about half a kilometer) of water covered the whole planet.
NASA will launch its Mars Atmosphere and Volatile EvolutioN (MAVEN) on November 18. MAVEN’s job is to determine exactly what happened to Mars’ atmosphere during those four billion years.
In the meantime, they had their Goddard Conceptual Image Lab create a video showing what Mars might’ve looked like four billion years ago and how it changed as the atmosphere thinned out over time:
There are a number of theories as to why Mars’ atmosphere disappeared, including a major asteroid impact and the loss of its magnetic field as a result of solar winds.
NASA hopes that the data collected by MAVEN will help them solve the issue once and for all.
(h/t IFL Science) | 0.833939 | 3.129342 |
The calendar spaces leap years to make the average year 365.2425 days long, approximating the 365.2422-day tropical year that is determined by the Earth's revolution around the Sun. The rule for leap years is:
Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the years 1600 and 2000 are.
The calendar was a revision of the Julian calendar,[Note 1] and had two aspects. Firstly, it shortened the average year by 0.0075 days to stop the drift of the calendar with respect to the equinoxes. Secondly, to deal with the drift since the Julian calendar was fixed[Note 2] the date was advanced 10 days, so that Thursday 4 October 1582 was followed by Friday 15 October 1582. There was no discontinuity in the cycle of weekdays or of the Anno Domini calendar era.[Note 3] The reform also altered the lunar cycle used by the Church to calculate the date for Easter (computus), restoring it to the time of the year as originally celebrated by the early Church.
The reform was adopted initially by the Catholic countries of Europe and their overseas possessions. Over the next three centuries, the Protestant and Eastern Orthodox countries also moved to what they called the Improved calendar, with Greece being the last European country to adopt the calendar in 1923. To unambiguously specify a date during the transition period (or in history texts), dual dating is sometimes used to specify both Old Style and New Style dates (abbreviated as O.S and N.S. respectively). Due to globalization in the 20th century, the calendar has also been adopted by most non-Western countries for civil purposes. The calendar era carries the alternative secular name of "Common Era".
|No.||Name||Length in days|
|2||February||28 (29 in leap years)|
The Gregorian calendar is a solar calendar with 12 months of 28–31 days each. A regular Gregorian year consists of 365 days, but in certain years known as leap years, a leap day is added to February. Gregorian years are identified by consecutive year numbers. A calendar date is fully specified by the year (numbered according to a calendar era, in this case Anno Domini or Common Era), the month (identified by name or number), and the day of the month (numbered sequentially starting from 1). Although the calendar year currently runs from 1 January to 31 December, at previous times year numbers were based on a different starting point within the calendar (see the "beginning of the year" section below).
In the Julian calendar, a leap year occurred every 4 years, and the leap day was inserted by doubling 24 February. The Gregorian reform omitted a leap day in three of every 400 years and left the leap day unchanged. However, it has become customary in the modern period to number the days sequentially with no gaps, and 29 February is typically considered as the leap day. Before the 1969 revision of the Roman Calendar, the Roman Catholic Church delayed February feasts after the 23rd by one day in leap years; Masses celebrated according to the previous calendar still reflect this delay.
Calendar cycles repeat completely every 400 years, which equals 146,097 days.[Note 4][Note 5] Of these 400 years, 303 are regular years of 365 days and 97 are leap years of 366 days. A mean calendar year is 365+97/ days = 365.2425 days, or 365 days, 5 hours, 49 minutes and 12 seconds.[Note 6]
Christopher Clavius (1538–1612), one of the main authors of the reform
Pope Gregory XIII, portrait by Lavinia Fontana, 16C.
First page of the papal bull Inter gravissimas
Detail of the pope's tomb by Camillo Rusconi (completed 1723); Antonio Lilio is genuflecting before the pope, presenting his printed calendar.
The Gregorian calendar was a reform of the Julian calendar. It was instituted by papal bull Inter gravissimas dated 24 February 1582 by Pope Gregory XIII, after whom the calendar is named. The motivation for the adjustment was to bring the date for the celebration of Easter to the time of year in which it was celebrated when it was introduced by the early Church. The error in the Julian calendar (its assumption that there are exactly 365.25 days in a year) had led to the date of the equinox according to the calendar drifting from the observed reality, and thus an error had been introduced into the calculation of the date of Easter. Although a recommendation of the First Council of Nicaea in 325 specified that all Christians should celebrate Easter on the same day, it took almost five centuries before virtually all Christians achieved that objective by adopting the rules of the Church of Alexandria (see Easter for the issues which arose).[Note 7]
Because the date of Easter is a function – the computus – of the date of the (northern hemisphere) spring equinox, the Catholic Church considered unacceptable the increasing divergence between the canonical date of the equinox and observed reality. Easter is celebrated on the Sunday after the ecclesiastical full moon on or after 21 March, which was adopted as approximation to the March equinox. European scholars had been well aware of the calendar drift since the early medieval period.
Bede, writing in the 8th century, showed that the accumulated error in his time was more than three days. Roger Bacon in c. 1200 estimated the error at seven or eight days. Dante, writing c. 1300, was aware of the need of a calendar reform. The first attempt to go forward with such a reform was undertaken by Pope Sixtus IV, who in 1475 invited Regiomontanus to the Vatican for this purpose. However, the project was interrupted by the death of Regiomontanus shortly after his arrival in Rome. The increase of astronomical knowledge and the precision of observations towards the end of the 15th century made the question more pressing. Numerous publications over the following decades called for a calendar reform, among them two papers sent to the Vatican by the University of Salamanca in 1515 and 1578, but the project was not taken up again until the 1540s, and implemented only under Pope Gregory XIII (r. 1572–1585).
In 1545, the Council of Trent authorised Pope Paul III to reform the calendar, requiring that the date of the vernal equinox be restored to that which it held at the time of the First Council of Nicaea in 325 and that an alteration to the calendar be designed to prevent future drift. This would allow for a more consistent and accurate scheduling of the feast of Easter.
In 1577, a Compendium was sent to expert mathematicians outside the reform commission for comments. Some of these experts, including Giambattista Benedetti and Giuseppe Moleto, believed Easter should be computed from the true motions of the Sun and Moon, rather than using a tabular method, but these recommendations were not adopted. The reform adopted was a modification of a proposal made by the Calabrian doctor Aloysius Lilius (or Lilio).
Lilius's proposal included reducing the number of leap years in four centuries from 100 to 97, by making three out of four centurial years common instead of leap years. He also produced an original and practical scheme for adjusting the epacts of the Moon when calculating the annual date of Easter, solving a long-standing obstacle to calendar reform.
Ancient tables provided the Sun's mean longitude. The German mathematician Christopher Clavius, the architect of the Gregorian calendar, noted that the tables agreed neither on the time when the Sun passed through the vernal equinox nor on the length of the mean tropical year. Tycho Brahe also noticed discrepancies. The Gregorian leap year rule (97 leap years in 400 years) was put forward by Petrus Pitatus of Verona in 1560. He noted that it is consistent with the tropical year of the Alfonsine tables and with the mean tropical year of Copernicus (De revolutionibus) and Erasmus Reinhold (Prutenic tables). The three mean tropical years in Babylonian sexagesimals as the excess over 365 days (the way they would have been extracted from the tables of mean longitude) were 0;14,33,9,57 (Alfonsine), 0;14,33,11,12 (Copernicus) and 0;14,33,9,24 (Reinhold). In decimal notation, these are equal to 0.24254606, 0.24255185, and 0.24254352, respectively. All values are the same to two sexagesimal places (0;14,33, equal to decimal 0.2425) and this is also the mean length of the Gregorian year. Thus Pitatus' solution would have commended itself to the astronomers.
Lilius's proposals had two components. First, he proposed a correction to the length of the year. The mean tropical year is 365.24219 days long. A commonly used value in Lilius's time, from the Alfonsine tables, is 365.2425463 days. As the average length of a Julian year is 365.25 days, the Julian year is almost 11 minutes longer than the mean tropical year. The discrepancy results in a drift of about three days every 400 years. Lilius's proposal resulted in an average year of 365.2425 days (see Accuracy). At the time of Gregory's reform there had already been a drift of 10 days since the Council of Nicaea, resulting in the vernal equinox falling on 10 or 11 March instead of the ecclesiastically fixed date of 21 March, and if unreformed it would have drifted further. Lilius proposed that the 10-day drift should be corrected by deleting the Julian leap day on each of its ten occurrences over a period of forty years, thereby providing for a gradual return of the equinox to 21 March.
Lilius's work was expanded upon by Christopher Clavius in a closely argued, 800-page volume. He would later defend his and Lilius's work against detractors. Clavius's opinion was that the correction should take place in one move, and it was this advice which prevailed with Gregory.
The second component consisted of an approximation which would provide an accurate yet simple, rule-based calendar. Lilius's formula was a 10-day correction to revert the drift since the Council of Nicaea, and the imposition of a leap day in only 97 years in 400 rather than in 1 year in 4. The proposed rule was that years divisible by 100 would be leap years only if they were divisible by 400 as well.
The 19-year cycle used for the lunar calendar was also to be corrected by one day every 300 or 400 years (8 times in 2500 years) along with corrections for the years that are no longer leap years (i.e. 1700, 1800, 1900, 2100, etc.) In fact, a new method for computing the date of Easter was introduced.
When the new calendar was put in use, the error accumulated in the 13 centuries since the Council of Nicaea was corrected by a deletion of 10 days. The Julian calendar day Thursday, 4 October 1582 was followed by the first day of the Gregorian calendar, Friday, 15 October 1582 (the cycle of weekdays was not affected).
First printed Gregorian calendar
A month after having decreed the reform, the pope (with a brief of 3 April 1582) granted to one Antoni Lilio the exclusive right to publish the calendar for a period of ten years. The Lunario Novo secondo la nuova riforma[a] was printed by Vincenzo Accolti, one of the first calendars printed in Rome after the reform, notes at the bottom that it was signed with papal authorization and by Lilio (Con licentia delli Superiori... et permissu Ant(onii) Lilij). The papal brief was revoked on 20 September 1582, because Antonio Lilio proved unable to keep up with the demand for copies.
Although Gregory's reform was enacted in the most solemn of forms available to the Church, the bull had no authority beyond the Catholic Church and the Papal States. The changes that he was proposing were changes to the civil calendar, over which he had no authority. They required adoption by the civil authorities in each country to have legal effect.
The bull Inter gravissimas became the law of the Catholic Church in 1582, but it was not recognised by Protestant Churches, Eastern Orthodox Churches, Oriental Orthodox Churches, and a few others. Consequently, the days on which Easter and related holidays were celebrated by different Christian Churches again diverged.
On 29 September 1582, Philip II of Spain decreed the change from the Julian to the Gregorian calendar. This affected much of Roman Catholic Europe, as Philip was at the time ruler over Spain and Portugal as well as much of Italy. In these territories, as well as in the Polish–Lithuanian Commonwealth (ruled by Anna Jagiellon) and in the Papal States, the new calendar was implemented on the date specified by the bull, with Julian Thursday, 4 October 1582, being followed by Gregorian Friday, 15 October 1582. The Spanish and Portuguese colonies followed somewhat later de facto because of delay in communication.
Many Protestant countries initially objected to adopting a Catholic innovation; some Protestants feared the new calendar was part of a plot to return them to the Catholic fold. For example, the British could not bring themselves to adopt the Catholic system explicitly: the Annexe to their Calendar (New Style) Act 1750 established a computation for the date of Easter that achieved the same result as Gregory's rules, without actually referring to him.
Prior to 1917, Turkey used the lunar Islamic calendar with the Hegira era for general purposes and the Julian calendar for fiscal purposes. The start of the fiscal year was eventually fixed at 1 March and the year number was roughly equivalent to the Hegira year (see Rumi calendar). As the solar year is longer than the lunar year this originally entailed the use of "escape years" every so often when the number of the fiscal year would jump. From 1 March 1917 the fiscal year became Gregorian, rather than Julian. On 1 January 1926 the use of the Gregorian calendar was extended to include use for general purposes and the number of the year became the same as in most other countries.
Adoption of the Gregorian Calendar
|1582||Spain, Portugal, France, Poland, Italy, Catholic Low Countries, Luxemburg, and colonies|
|1584||Kingdom of Bohemia|
|1700||'Germany',[Note 8] Swiss Cantons, Protestant Low Countries, Norway, Denmark|
|1752||Great Britain and colonies|
|1753||Sweden and Finland|
|1919||Romania, Yugoslavia[Note 9]|
Difference between Gregorian and Julian calendar dates
|Gregorian range||Julian range||Difference|
|From 15 October 1582
to 28 February 1700
|From 5 October 1582
to 18 February 1700
|From 1 March 1700
to 28 February 1800
|From 19 February 1700
to 17 February 1800
|From 1 March 1800
to 28 February 1900
|From 18 February 1800
to 16 February 1900
|From 1 March 1900
to 28 February 2100
|From 17 February 1900
to 15 February 2100
|From 1 March 2100
to 28 February 2200
|From 16 February 2100
to 14 February 2200
This section always places the intercalary day on 29 February even though it was always obtained by doubling 24 February (the bissextum (twice sixth) or bissextile day) until the late Middle Ages. The Gregorian calendar is proleptic before 1582 (assumed to exist before 1582), and the difference between Gregorian and Julian calendar dates increases by three days every four centuries (all date ranges are inclusive).
The following equation gives the number of days (actually, dates) that the Gregorian calendar is ahead of the Julian calendar, called the secular difference between the two calendars. A negative difference means the Julian calendar is ahead of the Gregorian calendar.
where is the secular difference and is the year using astronomical year numbering, that is, use (year BC) − 1 for BC years. means that if the result of the division is not an integer it is rounded down to the nearest integer. Thus during the 1900s, 1900/400 = 4, while during the −500s, −500/400 = −2.
The general rule, in years which are leap years in the Julian calendar but not the Gregorian, is:
Up to 28 February in the calendar being converted from, add one day less or subtract one day more than the calculated value. Give February the appropriate number of days for the calendar being converted into. When subtracting days to calculate the Gregorian equivalent of 29 February (Julian), 29 February is discounted. Thus if the calculated value is −4 the Gregorian equivalent of this date is 24 February.
Beginning of the year
|Country||Start numbered year
on 1 January
|Denmark||Gradual change from
13th to 16th centuries
|Holy Roman Empire (Catholic states)||1544||1583|
|Spain, Poland, Portugal||1556||1582|
|Holy Roman Empire (Protestant states)||1559||1700[Note 8]|
|Great Britain and the British Empire
The year used in dates during the Roman Republic and the Roman Empire was the consular year, which began on the day when consuls first entered office—probably 1 May before 222 BC, 15 March from 222 BC and 1 January from 153 BC. The Julian calendar, which began in 45 BC, continued to use 1 January as the first day of the new year. Even though the year used for dates changed, the civil year always displayed its months in the order January to December from the Roman Republican period until the present.
During the Middle Ages, under the influence of the Catholic Church, many Western European countries moved the start of the year to one of several important Christian festivals—25 December (supposed Nativity of Jesus), 25 March (Annunciation), or Easter (France), while the Byzantine Empire began its year on 1 September and Russia did so on 1 March until 1492 when the new year was moved to 1 September.
In common usage, 1 January was regarded as New Year's Day and celebrated as such, but from the 12th century until 1751 the legal year in England began on 25 March (Lady Day). So, for example, the Parliamentary record lists the execution of Charles I on 30 January as occurring in 1648 (as the year did not end until 24 March), although later histories adjust the start of the year to 1 January and record the execution as occurring in 1649.
Most Western European countries changed the start of the year to 1 January before they adopted the Gregorian calendar. For example, Scotland changed the start of the Scottish New Year to 1 January in 1600 (this means that 1599 was a short year). England, Ireland and the British colonies changed the start of the year to 1 January in 1752 (so 1751 was a short year with only 282 days) though in England the start of the tax year remained at 25 March (O.S.), 5 April (N.S.) until 1800, when it moved to 6 April. Later in 1752 in September the Gregorian calendar was introduced throughout Britain and the British colonies (see the section Adoption). These two reforms were implemented by the Calendar (New Style) Act 1750.
In some countries, an official decree or law specified that the start of the year should be 1 January. For such countries a specific year when a 1 January-year became the norm can be identified. In other countries the customs varied, and the start of the year moved back and forth as fashion and influence from other countries dictated various customs.
Neither the papal bull nor its attached canons explicitly fix such a date, though it is implied by two tables of saint's days, one labelled 1582 which ends on 31 December, and another for any full year that begins on 1 January. It also specifies its epact relative to 1 January, in contrast with the Julian calendar, which specified it relative to 22 March. The old date was derived from the Greek system: the earlier Supputatio Romana specified it relative to 1 January.
- In 1793 France abandoned the Gregorian calendar in favour of the French Republican Calendar. This change was reverted in 1805.
During the period between 1582, when the first countries adopted the Gregorian calendar, and 1923, when the last European country adopted it, it was often necessary to indicate the date of some event in both the Julian calendar and in the Gregorian calendar, for example, "10/21 February 1750/51", where the dual year accounts for some countries already beginning their numbered year on 1 January while others were still using some other date. Even before 1582, the year sometimes had to be double dated because of the different beginnings of the year in various countries. Woolley, writing in his biography of John Dee (1527–1608/9), notes that immediately after 1582 English letter writers "customarily" used "two dates" on their letters, one OS and one NS.
Old Style and New Style dates
"Old Style" (OS) and "New Style" (NS) are sometimes added to dates to identify which calendar reference system is used for the date given. In Britain and its colonies, where the Calendar Act of 1750 altered the start of the year,[Note 11] and also aligned the British calendar with the Gregorian calendar, there is some confusion as to what these terms mean. They can indicate that the start of the Julian year has been adjusted to start on 1 January (NS) even though contemporary documents use a different start of year (OS); or to indicate that a date conforms to the Julian calendar (OS), formerly in use in many countries, rather than the Gregorian calendar (NS).
Proleptic Gregorian calendar
Extending the Gregorian calendar backwards to dates preceding its official introduction produces a proleptic calendar, which should be used with some caution. For ordinary purposes, the dates of events occurring prior to 15 October 1582 are generally shown as they appeared in the Julian calendar, with the year starting on 1 January, and no conversion to their Gregorian equivalents. For example, the Battle of Agincourt is universally considered to have been fought on 25 October 1415 which is Saint Crispin's Day.
Usually, the mapping of new dates onto old dates with a start of year adjustment works well with little confusion for events that happened before the introduction of the Gregorian calendar. But for the period between the first introduction of the Gregorian calendar on 15 October 1582 and its introduction in Britain on 14 September 1752, there can be considerable confusion between events in continental western Europe and in British domains in English language histories.
Events in continental western Europe are usually reported in English language histories as happening under the Gregorian calendar. For example, the Battle of Blenheim is always given as 13 August 1704. Confusion occurs when an event affects both. For example, William III of England set sail from the Netherlands on 11 November 1688 (Gregorian calendar) and arrived at Brixham in England on 5 November 1688 (Julian calendar).
Shakespeare and Cervantes seemingly died on exactly the same date (23 April 1616), but Cervantes predeceased Shakespeare by ten days in real time (as Spain used the Gregorian calendar, but Britain used the Julian calendar). This coincidence encouraged UNESCO to make 23 April the World Book and Copyright Day.
Astronomers avoid this ambiguity by the use of the Julian day number.
For dates before the year 1, unlike the proleptic Gregorian calendar used in the international standard ISO 8601, the traditional proleptic Gregorian calendar (like the Julian calendar) does not have a year 0 and instead uses the ordinal numbers 1, 2, ... both for years AD and BC. Thus the traditional time line is 2 BC, 1 BC, AD 1, and AD 2. ISO 8601 uses astronomical year numbering which includes a year 0 and negative numbers before it. Thus the ISO 8601 time line is −0001, 0000, 0001, and 0002.
- January (31 days), from Latin mēnsis Iānuārius, "Month of Janus", the Roman god of gates, doorways, beginnings and endings
- February (28 days in common and 29 in leap years), from Latin mēnsis Februārius, "Month of the Februa", the Roman festival of purgation and purification, cognate with fever, the Etruscan death god Februus ("Purifier"), and the Proto-Indo-European word for sulfur
- March (31 days), from Latin mēnsis Mārtius, "Month of Mars", the Roman war god
- April (30 days), from Latin mēnsis Aprīlis, of uncertain meaning but usually derived from some form of the verb aperire ("to open") or the name of the goddess Aphrodite
- May (31 days), from Latin mēnsis Māius, "Month of Maia", a Roman vegetation goddess whose name is cognate with Latin magnus ("great") and English major
- June (30 days), from Latin mēnsis Iūnius, "Month of Juno", the Roman goddess of marriage, childbirth, and rule
- July (31 days), from Latin mēnsis Iūlius, "Month of Julius Caesar", the month of Caesar's birth, instituted in 44 BC as part of his calendrical reforms
- August (31 days), from Latin mēnsis Augustus, "Month of Augustus", instituted by Augustus in 8 BC in agreement with July and from the occurrence during the month of several important events during his rise to power
- September (30 days), from Latin mēnsis september, "seventh month", of the ten-month Roman year of Romulus c. 750 BC
- October (31 days), from Latin mēnsis octōber, "eighth month", of the ten-month Roman year of Romulus c. 750 BC
- November (30 days), from Latin mēnsis november, "ninth month", of the ten-month Roman year of Romulus c. 750 BC
- December (31 days), from Latin mēnsis december, "tenth month", of the ten-month Roman year of Romulus c. 750 BC
Europeans sometimes attempt to remember the number of days in each month by memorizing some form of the traditional verse "Thirty Days Hath September". It appears in Latin, Italian, and French, and belongs to a broad oral tradition but the earliest currently attested form of the poem is the English marginalia inserted into a calendar of saints c. 1425:
Thirti dayes hath novembir
Thirty days have November,
Variations appeared in Mother Goose and continue to be taught at schools. The unhelpfulness of such involved mnemonics has been parodied as "Thirty days hath September / But all the rest I can't remember" but it has also been called "probably the only sixteenth-century poem most ordinary citizens know by heart". A common nonverbal alternative is the knuckle mnemonic, considering the knuckles of one's hands as months with 31 days and the lower spaces between them as the months with fewer days. Using two hands, one may start from either pinkie knuckle as January and count across, omitting the space between the index knuckles (July and August). The same procedure can be done using the knuckles of a single hand, returning from the last (July) to the first (August) and continuing through. A similar mnemonic is to move up a piano keyboard in semitones from an F key, taking the white keys as the longer months and the black keys as the shorter ones.
In conjunction with the system of months there is a system of weeks. A physical or electronic calendar provides conversion from a given date to the weekday, and shows multiple dates for a given weekday and month. Calculating the day of the week is not very simple, because of the irregularities in the Gregorian system. When the Gregorian calendar was adopted by each country, the weekly cycle continued uninterrupted. For example, in the case of the few countries that adopted the reformed calendar on the date proposed by Gregory XIII for the calendar's adoption, Friday, 15 October 1582, the preceding date was Thursday, 4 October 1582 (Julian calendar).
Opinions vary about the numbering of the days of the week. ISO 8601, in common use worldwide, starts with Monday=1; printed monthly calendar grids often list Mondays in the first (left) column of dates and Sundays in the last. In North America, the week typically begins on Sunday and ends on Saturday.
The Gregorian calendar improves the approximation made by the Julian calendar by skipping three Julian leap days in every 400 years, giving an average year of 365.2425 mean solar days long. This approximation has an error of about one day per 3,030 years with respect to the current value of the mean tropical year. However, because of the precession of the equinoxes, which is not constant, and the movement of the perihelion (which affects the Earth's orbital speed) the error with respect to the astronomical vernal equinox is variable; using the average interval between vernal equinoxes near 2000 of 365.24237 days implies an error closer to 1 day every 7,700 years. By any criterion, the Gregorian calendar is substantially more accurate than the 1 day in 128 years error of the Julian calendar (average year 365.25 days).
In the 19th century, Sir John Herschel proposed a modification to the Gregorian calendar with 969 leap days every 4000 years, instead of 970 leap days that the Gregorian calendar would insert over the same period. This would reduce the average year to 365.24225 days. Herschel's proposal would make the year 4000, and multiples thereof, common instead of leap. While this modification has often been proposed since, it has never been officially adopted.
On time scales of thousands of years, the Gregorian calendar falls behind the astronomical seasons. This is because the Earth's speed of rotation is gradually slowing down, which makes each day slightly longer over time (see tidal acceleration and leap second) while the year maintains a more uniform duration.
Calendar seasonal error
This image shows the difference between the Gregorian calendar and the astronomical seasons.
The y-axis is the date in June and the x-axis is Gregorian calendar years.
Each point is the date and time of the June solstice in that particular year. The error shifts by about a quarter of a day per year. Centurial years are ordinary years, unless they are divisible by 400, in which case they are leap years. This causes a correction in the years 1700, 1800, 1900, 2100, 2200, and 2300.
For instance, these corrections cause 23 December 1903 to be the latest December solstice, and 20 December 2096 to be the earliest solstice—about 2.35 days of variation compared with the seasonal event.
The following are proposed reforms of the Gregorian calendar:
- Calendar (New Style) Act 1750
- Calendar reform
- Conversion between Julian and Gregorian calendars
- Doomsday rule
- French revolutionary calendar
- Hebrew calendar
- Dionysius Exiguus
- Inter gravissimas in English – Wikisource
- Julian day
- History of calendars
- ISO 8601, an international standard for the representation of dates and times, which uses the Gregorian calendar (see Section 3.2.1).
- List of adoption dates of the Gregorian calendar per country
- List of calendars
- Old Calendarists
- Revised Julian calendar (Milanković) – used in Eastern Orthodoxy
Precursors of the Gregorian reform
- "New Almanac according to the new reform".
- The Julian calendar assumed incorrectly that the average year is exactly 365.25 days long.
- Since the First Council of Nicaea and first Easter of AD 325, instead of 45 BC when Julian calendar was adopted.
- Two era names occur within the bull Inter gravissimas itself, anno Incarnationis dominicæ ("in the year of the Incarnation of the Lord") for the year it was signed, and anno à Nativitate Domini nostri Jesu Christi ("in the year from the Nativity of our Lord Jesus Christ") for the year it was printed.
- The cycle described applies to the solar, or civil, calendar. If one also considers the ecclesiastical lunar rules, the lunisolar Easter computus cycle repeats only after 5,700,000 years of 2,081,882,250 days in 70,499,183 lunar months, based on an assumed mean lunar month of 29 days 12 hours 44 minutes 2+49928114/ seconds. (Seidelmann (1992), p. 582) [To properly function as an Easter computus, this lunisolar cycle must have the same mean year as the Gregorian solar cycle, and indeed that is exactly the case.]
- The extreme length of the Gregorian Easter computus is due to its being the product of the 19-year Metonic cycle, the thirty different possible values of the epact, and the least common multiple (10,000) of the 400-year and 2,500-year solar and lunar correction cycles.
- The same result is obtained by summing the fractional parts implied by the rule: 365 + 1/ − 1/ + 1/ = 365 + 0.25 − 0.01 + 0.0025 = 365.2425
- The last major Christian region to accept the Alexandrian rules was the Carolingian Empire (most of Western Europe) during 780–800. The last monastery in England to accept the Alexandrian rules did so in 931, and a few churches in southwest Asia beyond the eastern border of the Byzantine Empire continued to use rules that differed slightly, causing four dates for Easter to differ every 532 years.
- Protestant states in Germany used an astronomical Easter from 1700 to 1774, based on Kepler's Rudolphine Tables, differing from the Gregorian Easter twice, one week early in 1724 and 1744.
- 1919 in the regions comprising the former Kingdoms of Serbia and Montenegro (present-day Kosovo, Montenegro, Serbia and North Macedonia). The western and northern regions of what became Yugoslavia were already using the Gregorian calendar. For example, most of Slovenia adopted the Gregorian calendar at the same time as Austria in 1583. Coastal Croatia, which was at the time ruled by Venice, adopted the Gregorian calendar in 1582. Inland Croatia, ruled by the Habsburgs, adopted it in 1587 along with Hungary. The Gregorian calendar was used in Bosnia and Herzegovina since the 16th century by the Catholic population and was formally adopted for government use in 1878 following occupation by Austria-Hungary.
- Lorraine reverted to Julian in 1735 and adopted Gregorian again in 1760
- In Scotland the legal start of year had been moved to 1 January in 1600 (Mike Spathaky. Old Style New Style dates and the change to the Gregorian calendar).
- Dershowitz & Reingold 2008, p. 45. "The calendar in use today in most of the world is the Gregorian or new-style calendar designed by a commission assembled by Pope Gregory XIII in the sixteenth century."
- Introduction to Calendars. (15 May 2013). United States Naval Observatory.
- See Wikisource English translation of the (Latin) 1582 papal bull Inter gravissimas.
- Les canons of Les textes fondateurs du calendrier grégorien (in Latin and French)
- Blegen n.d.
- Clause 3.2.1 ISO 8601
- Richards 1998, p. 101
- Walker (1945), p.218.
- Richards 2013, p. 599.
- Ari Ben-Menahem, Historical Encyclopedia of Natural and Mathematical Sciences vol. 1 (2009), p. 863.
- Carabias Torres, 2012, p. 241
- Ziggelaar (1983), pp. 211, 214.
- Moyer 1983.
- See, for example,Tabule illustrissimi principis regis alfonsii, Prague 1401−4 (Latin). A full set of Alphonsine Tables (including tables for mean motions, conjunctions of Sun and Moon, equation of time, spherical astronomy, longitudes and latitudes of cities, star tables, eclipse tables).
- For an example of the information provided see Jacques Cassini, Tables astronomiques du soleil, de la lune, des planètes, des étoiles fixes, et des satellites de Jupiter et de Saturne, Paris 1740, available at (go forward ten pages to Table III on p. 10).
- Dreyer, J L E (2014). Tycho Brahe. Cambridge. p. 52. ISBN 978-1-108-06871-0.
He remarks that both the Alphonsine and the Prutenic Tables are several hours wrong with regard to the time of the equinoxes and solstices.
- North, J (1989). The Universal frame: historical essays in astronomy, natural philosophy and scientific method. London. p. 29. ISBN 978-0-907628-95-8.
He noted on one occasion that the Alphonsine tables differed from the Prutenic by nineteen hours as to the time of the vernal equinox of 1588.
- Dreyer, J L E (2014). Tycho Brahe. Cambridge. p. 52. ISBN 978-1-108-06871-0.
- Swerdlow (1986).
- Meeus and Savoie (1992).
- Moyer (1983). p.
- Mezzi, E., and Vizza, F., Luigi Lilio Medico Astronomo e Matematico di Cirò, Laruffa Editore, Reggio Calabria, 2010, p. 14; p. 52, citing as primary references: Biblioteca Nazionale Centrale die Firenze, Magl. 5.10.5/a, ASV A.A., Arm. I‑XVIII, 5506, f. 362r.
- Kamen, Henry (1998). Philip of Spain. Yale University Press. p. 248. ISBN 978-0300078008.
- "Pragmatica" on the Ten Days of the Year World Digital Library, the first known South American imprint, produced in 1584 by Antonio Ricardo, of a four-page edict issued by King Philip II of Spain in 1582, decreeing the change from the Julian to the Gregorian calendar.
- 24 Geo. II Ch. 23, § 3.
- A more extensive list is available at Conversion between Julian and Gregorian calendars
- Blackburn & Holford-Strevens (1999), p. 788.
- Herluf Nielsen: Kronologi (2nd ed., Dansk Historisk Fællesforening, Copenhagen 1967), pp. 48–50.
- Lamont, Roscoe (1920), "The reform of the Julian calendar", Popular Astronomy, 28: 18–32
- Le calendrier grégorien en France (in French)
- Per decree of 16 June 1575. Hermann Grotefend, "Osteranfang" (Easter beginning), Zeitrechnung de Deutschen Mittelalters und der Neuzeit (Chronology of the German Middle Ages and modern times) (1891–1898)
- Blackburn & Holford-Strevens (1999), p. 784.
- John James Bond, Handy-book of rules and tables for verifying dates with the Christian era Scottish decree on pp. xvii–xviii.
- Roscoe Lamont, The reform of the Julian calendar, Popular Astronomy 28 (1920) 18–32. Decree of Peter the Great is on pp. 23–24.
- Lorenzo Cattini, Legislazione toscana raccolta e illustrata, vol. 10, p. 208.
- Fora Febraro.
- "Roman Dates: Eponymous Years". Tyndalehouse.com. Retrieved 14 September 2010.
- Mike Spathaky Old Style and New Style Dates and the change to the Gregorian Calendar: A summary for genealogists
- S. I. Seleschnikow: Wieviel Monde hat ein Jahr? (Aulis-Verlag, Leipzig/Jena/Berlin 1981, p. 149), which is a German translation of С. И. Селешников: История календаря и хронология (Издательство "Наука", Moscow 1977). The relevant chapter is available online here: История календаря в России и в СССР (Calendar history in Russia and the USSR). Anno Mundi 7000 lasted from 1 March 1492 to 31 August 1492. (in Russian)
- Tuesday 31 December 1661, The Diary of Samuel Pepys "I sat down to end my journell for this year, ..."
- Nørby, Toke. The Perpetual Calendar: What about England Version 29 February 2000
- "House of Commons Journal Volume 8, 9 June 1660 (Regicides)". British History Online. Retrieved 18 March 2007.
- Death warrant of Charles I web page of the UK National Archives. A demonstration of New Style meaning Julian calendar with a start of year adjustment.
- Nørby, Toke. The Perpetual Calendar
- Benjamin Woolley, The Queen's Conjurer: The science and magic of Dr. John Dee, adviser to Queen Elizabeth I (New York: Henry Holt, 2001) p. 173
- Spathaky, Mike Old Style New Style dates and the change to the Gregorian calendar. "increasingly parish registers, in addition to a new year heading after 24th March showing, for example '1733', had another heading at the end of the following December indicating '1733/4'. This showed where the New Style 1734 started even though the Old Style 1733 continued until 24th March. ... We as historians have no excuse for creating ambiguity and must keep to the notation described above in one of its forms. It is no good writing simply 20th January 1745, for a reader is left wondering whether we have used the Old or the New Style reckoning. The date should either be written 20th January 1745 OS (if indeed it was Old Style) or as 20th January 1745/6. The hyphen (1745-6) is best avoided as it can be interpreted as indicating a period of time."
- The October (November) Revolution Britannica encyclopaedia, A demonstration of New Style meaning the Gregorian calendar.
- Stockton, J.R. Date Miscellany I: The Old and New Styles "The terms 'Old Style' and 'New Style' are now commonly used for both the 'Start of Year' and 'Leap Year' [(Gregorian calendar)] changes (England & Wales: both in 1752; Scotland: 1600, 1752). I believe that, properly and historically, the 'Styles' really refer only to the 'Start of Year' change (from March 25th to January 1st); and that the 'Leap Year' change should be described as the change from Julian to Gregorian."
- "January, n.", Oxford English Dictionary, Oxford: Oxford University Press.
- "February, n.", Oxford English Dictionary.
- Liberman, Anatoly (7 March 2007), "On a Self-Congratulatory Note", Oxford Etymologist Archives, Oxford: Oxford University Press.
- "March, n.", Oxford English Dictionary.
- "April, n.", Oxford English Dictionary.
- It's not unusual for month names to be based on natural descriptions but this etymology is sometimes doubted since no other Roman months have such names.
- Plutarch, Life of Numa, Ch. xix.
- Scullard, Festivals and Ceremonies of the Roman Republic, p. 96.
- Forsythe, Time in Roman Religion, p. 10.
- This derivation was apparently a popular one in ancient Rome, given by Plutarch but rejected by Varro and Cincius.[where?]
- "May, n.", Oxford English Dictionary.
- "June, n.", Oxford English Dictionary.
- "July, n.", Oxford English Dictionary.
- "August, n.", Oxford English Dictionary.
- "September, n.", Oxford English Dictionary.
- "October, n.", Oxford English Dictionary.
- "November, n.", Oxford English Dictionary.
- "December, n.", Oxford English Dictionary.
- Onofri, Francesca Romana; et al. (2012), Italian for Dummies, Berlitz, pp. 101–2, ISBN 9781118258767.
- Bond, Otto Ferdinand; et al. (1918), Military Manual of Elementary French, Austin: E.L. Steck, p. 11.
- Bryan, Roger (30 October 2011), "The Oldest Rhyme in the Book", The Times, London: Times Newspapers.
- Misstear, Rachael (16 January 2012), "Welsh Author Digs Deep to Find Medieval Origins of Thirty Days Hath Verse", Wales Online, Media Wales.
- "Memorable Mnemonics", Today, London: BBC Radio 4, 30 November 2011.
- The Cincinnati Enquirer, Cincinnati, 20 September 1924, p. 6.
- Holland, Norman N. (1992), The Critical I, New York: Columbia University Press, p. 64–5, ISBN 9780231076517.
- Seidelmann (1992), pp. 580–581.
- Using value from Richards (2013, p. 587) for tropical year in mean solar days, the calculation is 1/(365.2425-365.24217)
- Meeus and Savoie (1992), p. 42
- John Herschel, Outlines of Astronomy, 1849, p. 629.
- Steel, Duncan (2000). Marking Time: The Epic Quest to Invent the Perfect Calendar. John Wiley & Sons. p. 185. ISBN 978-0-471-29827-4.
- Barsoum, Ignatius A. (2003). The Scattered Pearls. Piscataway: Georgias Press.
- Blackburn, B. & Holford-Strevens, L. (1999). The Oxford Companion to the Year. Oxford University Press. ISBN 0-19-214231-3.
- Blackburn, B. & Holford-Strevens, L. (2003). The Oxford Companion to the Year: An exploration of calendar customs and time-reckoning, Oxford University Press.
- Blegen, Carl W. (n.d.). "An Odd Christmas". Posted with an introduction by Natalia Vogeikoff-Brogan on 25 December 2013. From the Archivist's Notebook retrieved 1 April 2018.
- Borkowski, K. M., (1991). "The tropical calendar and solar year", J. Royal Astronomical Soc. of Canada 85(3): 121–130.
- Carabias Torres, A. M. (2012). Salamanca y la medida del tiempo. Salamanca: Ediciones Universidad de Salamanca.
- Coyne, G. V., Hoskin, M. A., Pedersen, O. (Eds.) (1983). Gregorian Reform of the Calendar: Proceedings of the Vatican Conference to Commemorate its 400th Anniversary, 1582–1982. Vatican City: Pontifical Academy of Sciences, Vatican Observatory (Pontificia Academia Scientarum, Specola Vaticana).
- Dershowitz, D., Reingold, E. M. (2008). Calendrical Calculations, 3rd ed. Cambridge University Press.
- Duncan, D. E. (1999). Calendar: Humanity's Epic Struggle To Determine A True And Accurate Year. HarperCollins. ISBN 9780380793242.
- Gregory XIII. (2002 ). Inter Gravissimas(subscription required) (W. Spenser & R. T. Crowley, Trans.). International Organization for Standardization.
- Meeus, J. & Savoie, D. (1992). The history of the tropical year. Journal of the British Astronomical Association, 102(1): 40–42.
- Morrison, L. V. & Stephenson, F. R. (2004). Historical values of the Earth's clock error ΔT and the calculation of eclipses. Journal for the History of Astronomy Vol. 35, Part 3, No. 120, pp. 327–336.
- Moyer, Gordon (May 1982). "The Gregorian Calendar". Scientific American, pp. 144–152.
- Moyer, Gordon (1983). "Aloisius Lilius and the Compendium Novae Rationis Restituendi Kalendarium". In Coyne, Hoskin, Pedersen (1983), pp. 171–188.
- Pattie, T.S. (1976) "An unexpected effect of the change in calendar in 1752". British Library Journal.
- Pedersen, O. (1983). "The Ecclesiastical Calendar and the Life of the Church". In Coyne, Hoskin, Pedersen (eds), Gregorian Reform of the Calendar: Proceedings of the Vatican Conference to Commemorate its 400th Anniversary. Vatican City: Pontifical Academy of Sciences, Specolo Vaticano, pp. 17–74.
- Richards, E. G. (1998). Mapping Time: The Calendar and its History. Oxford U. Press.
- Richards, E. G. (2013). "Calendars". In S. E. Urban and P. K. Seidelmann (eds.), Explanatory Supplement to the Astronomical Almanac 3rd ed. (pp. 585–624). Mill Valley CA: University Science Books. ISBN 978-1-891389-85-6
- Seidelmann, P. K. (Ed.) (1992). Explanatory Supplement to the Astronomical Almanac. 2nd ed. Sausalito, CA: University Science Books.
- Swerdlow, N. M. (1986). The Length of the Year in the Original Proposal for the Gregorian Calendar. Journal for the History of Astronomy Vol. 17, No. 49, pp. 109–118.
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- Gregorian calendar on In Our Time at the BBC
- Calendar Converter
- Inter Gravissimas (Latin and French plus English)
- History of Gregorian Calendar
- The Perpetual Calendar Gregorian Calendar adoption dates for many countries.
- World records for mentally calculating the day of the week in the Gregorian Calendar
- The Calendar FAQ – Frequently Asked Questions about Calendars
- Today's date (Gregorian) in over 800 more-or-less obscure foreign languages | 0.856021 | 3.286193 |
This is more of a question for the Physics stack, but I'll give it a shot, since it's fairly basic.
You need to understand something before we begin. The theoretical framework we have to gauge and answer this sort of thing is called General Relativity, which was proposed by Einstein in 1915. It describes things such as gravity, black holes, or just about any phenomena where large densities of mass or energy are involved.
There's another chapter in Physics called Quantum Mechanics. This describes, usually, what happens at very small scales - things that are super-tiny.
Both GR and QM are fine in their own way. Both are tested against reality and work very well. But they are not compatible with each other. Meaning: you cannot describe a phenomenon from a GR and a QM perspective, both at once. Or meaning: we don't have a coherent set of equations that we could write down, and then "extract" out of them either a GR-like view of reality, or a QM-like view.
The problem is, the center of a black hole is both very high mass density and very high gravity (and therefore right in the field of GR), and very small (and therefore "quantum-like"). To properly deal with it, we'd have to reconcile GR and QM and work with both at once. This is not possible with current physics.
We pretty much have to stick to GR only for now, when talking about black holes. This basically means that anything we say about the center of a black hole is probably incomplete, and subject to further revision.
A star dies, collapses into a black hole, what is at the center? The
star's mass compacted into the size of the plank length or something
similarly small? Is there really nothing at the center of a black
hole?, surely the core collapsed into something, just really small
According to General Relativity, it collapses all the way down to nothing. Not just "very small", but smaller and smaller until it's exactly zero in size. Density becomes infinite.
You can't say "Plank length" because, remember, we can't combine GR and QM, we just don't know how. All we have here is GR, and GR says it goes all the way down.
It is quite possible that the singularity is not physical, but just mathematical - in other words, whatever is at the center is not actually zero size. Quantum mechanics in particular would be offended by zero-size things. But we can't say for sure because our knowledge here is incomplete.
I'm using words such as "size" (which implies space) and "becomes" (which implies time). But both space and time in the context of a black hole are very seriously warped. The "becoming" of a black hole all the way down to the zero-size dot is a reality only for the unlucky observer that gets caught in it. But for a distant, external observer, this process is slowed and extended all the way to plus infinity (it's only complete after an infinitely long time). Both observers are correct, BTW.
So, when we are saying "density is infinite and size is zero at the singularity", this language applies to the unfortunate observer being dragged down in the middle of the initial collapse of the star.
But from the perspective of the distant observer, a black hole is still a chunk of mass (the original star) in a non-zero volume (the event horizon of the BH). To this observer, the density of that object is finite, and its size is definitely not zero. From this perspective, anything falling into the BH never quite finishes falling, but just slows down more and more.
Both observers are correct. So, keep in mind, when I talk about "infinite density", that's the inside observer point of view.
What is a singularity? Is it just the warping of space time that makes
it this way?
You get a singularity whenever there's a division by zero in the equations, or when the equations misbehave somehow at that point. There are many different kinds of singularities in science.
In the context of a black hole, the center is said to be a gravitational singularity, because density and gravity are suggested to become infinite, according to the GR equations.
GR says: when you have a lump of matter that's big enough, it starts to collapse into itself so hard, there's nothing to stop it. It keeps falling and falling into itself, with no limit whatsoever. Extrapolate this process, and it's easy to see that the size of it tends to zero, and density tends to an infinite value.
Put another way - if density becomes large enough, gravity is so huge, no other force is strong enough to resist it. It just crushes all barriers that matter raises to oppose further crushing. That lump of matter simply crushes itself, its own gravity pulls it together smaller and smaller... and smaller... and so on. According to current theories, there's nothing to stop it (QM might stop it, but we cannot prove it, because we don't have the math). So it just spirals down in a vicious cycle of ever-increasing gravity that increases itself.
Space and time are really pathologic inside the event horizon. If you are already inside, there's no way out. This is not because you can't move out fast enough, but because there's really no way out. No matter which way you turn, you're looking towards the central singularity - in both space and time. There is no conceivable trajectory that you could draw, starting from the inside of the event horizon, that leads outside. All trajectories point at the singularity. All your possible futures, if you're inside the event horizon, end at the central singularity.
So, why the center of a black hole is called a "singularity"? Because all sorts of discontinuities and divisions by zero jump out of the equations, when you push math to the limit, trying to describe the very center of a black hole, within a GR frame.
Speaking in general, physicists don't like singularities. In most cases, this is an indication that the mathematical apparatus has broken down, and some other calculations are necessary at that point. Or it might indicate that new physics are taking place there, superseding the old physics.
One last thing: just because we don't have a combined GR/QM theory to fully describe the center of black holes, that doesn't mean a pure GR research in this area is "wrong" or "useless". It doesn't mean one could imagine some arbitrary fantasy taking place inside a black hole.
Astronomers these days are starting to observe cosmic objects that are very much like black holes, and their observed properties are in very close accord with what GR predicts for such things. So research in this field must continue, because it's clearly on the right track, at least in the ways we can verify today in astronomy. | 0.835352 | 3.64466 |
June 5th, 2012 was the most recent Transit of Venus. The last Transit of Venus occurred June 8th, 2004. The next Transit of Venus occurs December 11th, 2117. The frequency of transits is no doubt interesting but the more proximate interest I have is how Venus was used to determine the size and scale of our Solar System.
An important geographical question is “how far is it?” Well, the answer to the question depends, depends on what “it” is. How far is it to your house? How far is it to the donut shop? How far is it to the beach? How far is it to the Sun? How far is it to Venus? The last two questions are necessary for determining the size and therefore scale of our Solar System. If we can determine distance to Venus we can then determine the distance to the Sun and thus we will have established our position among the inner most planets and we will have a new unit of measurement, the Astronomical Unit (AU).
The process of using two locations to measure the distance to a single point is called parallax. We use parallax every day to determine distance. Our eyes are a positioned a few centimeters apart. The distance between our eyes coupled with the images our retinas capture provide our brains enough information for most of us to infer properties about the objects around us, the speed of a car, the distance to a stop sign, or the height of a building. The illustration (left) is from the notes of Daniel Fischer, University of Germany – Bonn (link). I found his explanation of the Transit of Venus precisely in tune with the level of understanding I wanted to communicate.
His geometric description of parallax requires little more than a high school appreciation of geometry or freshman level trigonometry course. By following his directions, one can determine the Astronomical Unit (AU), the distance of the earth from the sun and thus have a basic understanding of planetary distance relationships.
One of fantastic side-effects of understanding the process outlined in Dr. Fischer notes deals with exoplanets. Exoplanets are those planets which orbit distant suns (stars). By determining the distance of an exoplanet from its sun we can figure out if the planet exists in the “Goldilocks Zone,” the zone not too hot and not too cold for life.
Another benefit of the method described in Fischer notes is our ability to use the idea of parallax to chart the distance to nearby stars. If we consider 1/2 the planetary orbit of the earth around the Sun as our baseline – the base of our triangle – and we collect two sitings 6 months apart, we can sort of calculate a distance. I say “sort of” since our measurement will not be entirely accurate. The Sun is moving through space and the target star is moving through space over the course of those six months, thus the geometry is changing.
I read recently in a cosmology textbook (“Your Cosmic Context”) the error inherent in the calculations is minimal due to the shear distance involved. With NPR running two stories (here) and (here) regarding the use of parallax to determine the distance of the earth to the Sun I’ve been reading more about the use of parallax to measure all sorts of cosmic distances. Some astronomers and cosmologists point out very small changes in angles, merely being off a few arc seconds can create substantial errors in calculations.
I’m neither cosmologist nor astronomer but I do tell my geography students to pay attention to the latitude and longitude calculations as rounding digits can shift the points measured with a GPS significantly. If you have ever looked through a pair of powerful binoculars and noticed how fast your field of view can swiftly change with small movements of your head then you get the idea.
Back in the “day” explorers used parallax to determine distance to far away objects, lighthouses, islands, points, coves, all sorts of places. Navigators had to be really good at angles, distances, direction, and speed – otherwise known as “course.” Tools like the astrolabe and secants were used to gauge position and if a series of positions were known then velocity could be calculated. Once velocity and positions were known then distances to places could be calculated. Navigators were very valuable people; they had to be smart. Early maps were developed by cartographers who were given information derived from parallax measurements. As our tools became better, magnetic compasses and precision chronometers introduced, better and more detailed maps were authored.
The fact cosmic distances are so large should give us some pause. First, parallax only works well for close objects. Right now, the best tool for measuring these distances is the satellite Hipparcos, launched in 1989. Hipparcos can measures distances using parallax to only 1,600 light-years. In 2013, the European Space Agency’s Gaia Mission (link) will be able to measure distances in the range of 10,000+ light-years using the parallax method. Astronomers and Astrophysicists and Cosmologist are constantly working out methods to accurately map out our solar system, our stellar neighbor, and our position within the cosmos. They can use radiation from different portions of the electromagnetic spectrum. They can use known properties of electromagnetic radiation to discern distances.
In fact, most cosmic objects cannot be measured using the parallax method simply because the objects are so very distant the parallax method won’t work. We can see many extremely distance objects simply standing outside on a clear night. On a clear night, if one knows where to look, 100+ galaxies are visible to the naked eye. Galaxies, not stars in our own Milky Way galaxy but other galaxies outside our own galaxy. Boggling!!!
Now, imagine looking at any one of those galaxies. The light emanating from the galaxy had to cross intergalactic space to reach your eye. That galaxy is not hundreds of light-years away, nor thousands, nor hundreds of thousands of light-years – er…actually, depending on which one you picked it could be a couple of hundred thousand light-years away – but, if you elected to pick out the stunning Andromeda Galaxy, the light from Andromeda took over 2-1/2 million years to reach your eye.
On a more earthly note, knowing these distances is very humbling. Not only humbling, but also challenging to those with very strong conservation religious beliefs. Many Southerners with whom I am familiar hold dearly to the Biblical notion the earth is only slightly older than the personalities of people detailed in Genesis. According to Creationists, the earth is a little over 6,000 years old. If the age of the earth was merely 6,000 years we would only be able to see those objects in the cosmos 6,000 light-years away or closer. Judging by the shear number of objects and type of objects we see, 6,000 years is simply absurd and insulting to any intelligent person.
Make no mistake, I am not bashing faith or spiritual beliefs, I am bashing religion-based presuppositional nonsense, especially those viewpoints which purport the Bible to be a first-hand eyewitness account of Creation.
I suppose God could have “staged” everything, like a surprise party, decorating and getting all the galaxies and black holes and nebulas in place and stringing all the light rays into place and 6,000 years ago God turned on the lights and yelled, “Surprise!! Look what I did!”
I don’t think so.
That’s fiction of the Tolkien world-building fantasy milieu.
And, oh yeah, there were living people walking the earth more than 6,poo years ago, too. They did not have dinosaurs as pets, though. The Dinotopia world Creationists dream about didn’t exist, either. I have to admit the idea is fun to think about in a purely speculative fiction sort of way. | 0.876531 | 3.811455 |
Briefing Materials: NASA Missions Explore Record-Setting Cosmic Blast
Released on November 21, 2013
On Thursday, Nov. 21, 2013, NASA held a media teleconference to discuss new findings related to a brilliant gamma-ray burst detected on April 27. Audio of the teleconference is available for download here.
These maps, both centered on the north galactic pole, show how the sky looks at gamma-ray energies above 100 million electron volts (MeV). Left: The sky during a three-hour interval prior to the detection of GRB 130427A. Right: A three-hour interval starting 2.5 hours before the burst and ending 30 minutes into the event, illustrating its brightness relative to the rest of the gamma-ray sky. GRB 130427A was located in the constellation Leo near its border with Ursa Major, whose brightest stars form the familiar Big Dipper. For reference, this image includes the stars and outlines of both constellations. Labeled.
Gamma-ray bursts are the most luminous explosions in the cosmos. Astronomers think most occur when the core of a massive star runs out of nuclear fuel, collapses under its own weight, and forms a black hole. The black hole then drives jets of particles that drill all the way through the collapsing star at nearly the speed of light. Artist's rendering.
Theorists believe that GRB jets produce gamma rays by two processes involving shock waves. Shells of material within the jet move at different speeds and collide, generating internal shock waves that result in low-energy (million electron volt, or MeV) gamma rays. As the leading edge of the jet interacts with its environment, it generates an external shock wave that results in the production of high-energy (billion electron volt, or GeV) gamma rays. Artist's rendering.
This illustration shows the ingredients of the most common type of gamma-ray burst. The core of a massive star (left) has collapsed, forming a black hole that sends a jet moving through the collapsing star and out into space at near the speed of light. Radiation across the spectrum arises from hot ionized gas (plasma) in the vicinity of the newborn black hole, collisions among shells of fast-moving gas within the jet (internal shock waves), and from the leading edge of the jet as it sweeps up and interacts with its surroundings (external shock).
RAPTOR-T is one of several robotic observatories making up the the Rapid Telescopes for Optical Response (RAPTOR) project operated by Los Alamos National Laboratory. The instrument consists of four co-aligned 0.4-meter telescopes, each with a different color filter (the "T" stands for technicolor). RAPTOR-T is designed to detect color changes in the optical flash accompanying a gamma-ray burst, which can yield information on the explosion's dynamics, environment and distance.
This movie shows GRB 130427A as viewed by the RAPTOR telescopes located near Los Alamos, N.M, and on Mount Haleakala on the island of Maui, Hawaii. The movie opens with wide-field images acquired by a RAPTOR All-Sky Monitor, one of the three identical systems to first detect the burst's optical flash. The movie then switches to observations from RAPTOR-T, which autonomously turned toward the burst after receiving an alert from NASA's Swift. The telescope imaged the burst for 2 hours and captured simultaneous images in four different colors.
Better known as NuSTAR, the Nuclear Spectroscopic Telescope Array is the first orbiting observatory able to focus high-energy X-rays. The instrument consists of two co-aligned grazing incidence telescopes with advanced optics and detectors that extend its sensitivity to higher energies (3,000 to 79,000 electron volts) than previous X-ray missions.
Instruments aboard three NASA missions and the ground-based RAPTOR telescope provide the most detailed multi-energy look at changing emissions of GRB 130427A. The early pulse of gamma rays detected by Fermi's GBM exhibits behaviors confounding all models that explain the emission based on colliding shells. Visible light measured by RAPTOR closely tracks the high-energy gamma rays detected by Fermi LAT, an unexpected relationship. Data from Swift's BAT, XRT and UVOT instruments, in concert with measurements from ground telescopes, capture the evolution of the GRB over weeks and show that it shares properties with much more distant bursts. Observations by NuSTAR and Fermi LAT challenge a 12-year-old prediction of how the emission components in a GRB spectrum should change with time. The ground-based measurements shown here come from the Faulkes Telescope North, located at Haleakala Observatory in Hawaii, the Liverpool Telescope on the island of La Palma, Spain, and the MITSuME Telescopes in Japan. For clarity, this chart omits error bars for all measurements.
This movie shows the jet associated with a gamma-ray burst as it emerges from a collapsing star and drives into space at nearly the speed of light. The frames are part of a high-resolution 3-D hydrodynamical simulation by Davide Lazzati at North Carolina State University and Brian Morsony at the University of Wisconsin, Madison, using the Pleiades supercomputer at NASA's Ames Research Center. The movie covers the first 8 seconds following the jet's emergence from the star.
Credit: Davide Lazzati (NCSU) and Brian Morsony (Univ. of Wisconsin)
NASA Swift's UVOT instrument captured the fading light of GRB 130427A using images acquired through its w1 and w2 filters, which correspond to energies of 4.7 and 6.1 electron volts, respectively. The movie begins about 6 minutes after the burst triggered Fermi's GBM instrument and lasts 10.3 days. Angular width of the movie is 100 arcseconds.
These maps, both centered on the north galactic pole, show how the sky looks at gamma-ray energies above 100 million electron volts (MeV). The first frame shows the sky during a three-hour interval prior to GRB 130427A. The second frame shows a three-hour interval starting 2.5 hours before the burst, and ending 30 minutes into the event. The Fermi team chose this interval to demonstrate how bright the burst was relative to the rest of the gamma-ray sky. This burst was bright enough that Fermi autonomously left its normal surveying mode to give the LAT instrument a better view, so the three-hour exposure following the burst does not cover the whole sky in the usual way.
This image illustrates the ingredients of the most common type of gamma-ray burst. The core of a massive star (left) has collapsed, forming a black hole that sends a jet moving through the collapsing star and out into space at near the speed of light. Radiation across the spectrum arises from hot ionized gas (plasma) in the vicinity of the newborn black hole, collisions among shells of fast-moving gas within the jet (internal shock waves), and from the leading edge of the jet as it sweeps up and interacts with its surroundings (external shock).
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 22.214.171.124.0 | 0.856639 | 3.932637 |
You’ve probably seen or heard many unfamiliar terms while researching telescopes. We’ve included the definitions of some of the most commonly used words in astronomy as a quick and easy reference.
A type of telescope mount that moves up and down (altitude), and side to side (azimuth) similar to a camera tripod.
Altitude and Azimuth
The two positions in the horizontal coordinate system. Altitude refers to the angle between the observer’s horizon and the object. Azimuth refers to the angle of the object along the horizon measured from north to east.
Aperture is the diameter of the telescope’s light-gathering lens or mirror. The larger the aperture, the more light will be collected resulting in brighter and sharper images. Aperture is typically measured in millimetres or inches.
Apparent Field of View
The angular diameter (in degrees) of the image viewed through the eyepiece. It is a property of the eyepiece.
A number that is the measure of the brightness of a celestial object to the naked eye. The lower the value, the brighter the object appears.
A minor planet orbiting the Sun with a diameter greater than one metre and mainly composed of minerals and rock.
A type of optical aberration where light does not come to focus on a single plane. Most telescope designs do not suffer from noticeable astigmatism.
Astronomical Unit (AU)
The average distance between the Earth and the Sun used to measure distances within our Solar System. One AU is about 93 million miles or 150 million kilometres.
The study of celestial objects and phenomena.
Taking photographs of celestial objects and phenomena.
A natural light display in the sky produced by the interaction of charged particles when solar wind disturbs the magnetosphere. Known as Aurora Borealis in the Northern Hemisphere and Aurora Australis in the Southern Hemisphere.
Viewing an object by looking slightly off to its side and not directly at it. This allows fainter details to appear.
A lens used along with an eyepiece that increases the telescope’s focal length and the magnification of the eyepiece. A 2x Barlow would double the eyepiece’s magnification.
A system of two stars that orbit around their common center of mass. Also known as double stars.
An optical device with a lens for each eye used to view distant objects.
Also known as a compound telescope. Uses a hybrid design with a combination of lenses and mirrors in a sealed tube which fold the optical path to form an image. This provides a focal length much longer than the length of the compact optical tube. They are more commonly known by the two popular designs: Schmidt-Cassegrain and Maksutov-Cassegrain.
A natural object that exists in the Universe and is located outside of Earth’s atmosphere.
An imaginary sphere with a large radius and the Earth located at its center. An observer can view celestial objects as though they are projected on to the inner surface of the celestial sphere.
A type of optical aberration present in some refractor telescopes. When light passes through the objective lens, each wavelength of light is refracted by a different amount and the colors fail to converge at the same focal point. Think of the rainbow effect of light passing through a glass prism. Chromatic aberration is typically seen as color fringing around bright objects, like a purple halo around planets and stars.
The process of manually adjusting the mirrors of a telescope when they are out of alignment.
A type of optical aberration (comatic) present in Newtonian reflector telescopes. With coma, stars appear distorted near the edge of the field of view while stars in the center of the field of view are unaffected.
A large ball of ice and rock that orbits the Sun. When a comet passes close to the Sun, it releases gas forming a coma (gas cloud) and a tail. Comets can range in size from hundreds of metres to tens of kilometres in diameter.
See ‘Catadioptric Telescope’
A telescope on a GoTo mount with a small motor drive, built-in computer and hand-held controller which allows you to look up celestial objects in a database. The GoTo will automatically locate the specific object and track its movement across the sky.
When two planets or celestial objects are aligned so that they have the same right ascension and appear to be close together as observed from Earth. It is caused by the perspective of the observer as the two objects involved are not actually close to each other in space.
A recognizable grouping of stars that form a pattern. There are 88 constellations which are typically named after animals, mythological characters or objects.
Cooldown Time (Thermal Stabilization)
The time required for a telescope’s optics to be brought to ambient temperature for optimal viewing.
The adjustment of the eyes to darkness or low light conditions. Dark adaptation is necessary to see faint objects.
One of two angles used to locate a point on the celestial sphere. It is comparable to geographic latitude.
Deep-Sky Objects (DSO)
Celestial objects that are not individual stars and are outside of our Solar System such as star clusters, nebulae and galaxies.
A simplified altazimuth mount for Newtonian reflectors. The mount sits on the ground, swivels 360 degrees and moves up and down.
See ‘Binary Star’
When a celestial object like a moon or planet temporarily moves into the shadow of another celestial object. A Lunar Eclipse occurs when the Earth blocks the sun and the Earth casts a shadow on the moon. A Solar Eclipse occurs when the moon blocks the sun and the moon casts a shadow on the Earth.
The circular path on the celestial sphere that the Sun appears to follow over the course of a year.
Equatorial Mount (EQ)
A type of telescope mount that is more precise than an altazimuth mount and better for astrophotography. Aligning one axis with Polaris allows you to adjust only the polar axis to track an object as the Earth rotates.
One of two times per year when the Sun crosses the plane of the Earth’s equator causing day and night to be of equal length.
The width of the cone of light that exits the eyepiece at the exact eye relief distance.
The part of the telescope that you look into. They are typically 1.25″ or 2″ in diameter. To change the telescope’s magnification, you can switch eyepieces with different focal lengths.
The distance between the eyepiece lens and the observer’s eye while still being able to see the entire field of view. Outside of this distance, the observer will see a reduced field of view.
Field of View (FOV)
See ‘Apparent Field of View’ and ‘True Field of View’
An accessory that attaches to the bottom of an eyepiece to enhance details of celestial objects. Neutral density or polarizing filters can reduce glare from bright objects like the moon. Color filters can enhance specific planetary details by blocking certain wavelengths of light.
An optical device attached to a telescope used to locate a celestial object and aim the telescope in its direction.
The distance from the objective lens or mirror to the focal point.
The point where parallel rays of light meet after passing through a lens or reflecting off of a mirror.
Focal Ratio (f/ratio)
Equal to the focal length of a telescope divided by its aperture size. A telescope with a focal length of 1200mm and an 8″ (203mm) aperture would have a focal ratio of f/5.9.
A device attached to the telescope into which an eyepiece is inserted. It can be adjusted to bring the image viewed through the telescope into focus. Types of focusers include helical, rack and pinion, and Crayford.
A system of stars, gas, dust, and dark matter that is gravitationally bound.
A spherical collection of stars that is tightly bound by gravity and has a high stellar density towards its center. They are found orbiting in the outer regions of a galaxy. Globular Clusters are much older and contain more stars than Open Clusters.
See ‘Computerized Telescope’
The angle between a reference plane and the orbital plane of an orbiting object.
Brightening of the sky caused by artificial light which can significantly reduce the ability to observe celestial objects.
The distance that light travels in one year, used to express astronomical distances. Equal to about 5.9 trillion miles or 9.5 trillion kilometres.
Equal to the focal length of a telescope divided by the focal length of an eyepiece. For example, a telescope with a focal length of 1200mm and an eyepiece with a focal length of 10mm would provide a magnification of 120x. Also known as power.
A type of catadioptric telescope design that uses a combination of a spherical mirror and a full aperture meniscus lens to correct for spherical aberration. Also known as a Mak.
A catalog of 110 deep-sky objects including nebulae, open clusters, globular clusters and galaxies. The initial list was created in 1771 by French astronomer Charles Messier.
A streak of light caused by a meteoroid, comet or astroid entering the Earth’s atmosphere at rapid speed causing it to heat up. Also known as a shooting star.
A small rocky or metallic body in outer space ranging in size from a small grain to a width of 1 metre.
A number of meteors appearing to originate from the same point in the sky. They occur at particular dates each year when the Earth passes through streams of cosmic debris.
The galaxy that contains our Solar System.
A mechanical structure that supports a telescope which allows it to point in the direction of celestial objects. The two types of telescope mounts are Altazimuth and Equatorial.
A cloud of gas and dust in outer space. Nebulae (plural) are visible as bright patches in the night sky or as opaque clouds that block light from luminous objects behind them (dark nebula).
A telescope’s main light-gathering lens or mirror.
A loose grouping of stars found in the disk of a galaxy. They can contain up to a few thousand stars. Open Clusters are younger and less dense than Globular Clusters.
Optical Tube Assembly (OTA)
The main tube of a telescope which contains the optics (objective lens or primary mirror). It does not include the mount.
The Universe beyond Earth’s atmosphere.
A reflective surface with a concave shape designed to bring light to focus at a single point.
A circular star map that can be adjusted to show the stars and constellations as they would appear at a specific date and time.
The brightest star in the constellation Ursa Minor. It is very close to the celestial north pole which is why it is commonly referred to as the North Star. It is used for navigation as it appears to remain stationary as the Earth rotates.
The main light-gathering mirror of a reflector telescope.
A form of computerized telescope with a hand-held controller which allows you to look up a celestial object in a database. After selecting your desired object, the controller will provide directional arrows for you to move the telescope by hand until it is in the correct position. Unlike a GoTo, a PushTo requires manual tracking.
Red Dot Finder
A reflex sight finder that doesn’t provide any magnification. Look through the red dot finder’s viewing window and align the red LED dot with the celestial object you wish to observe by moving the telescope.
A type of telescope that is open at one end and uses a concave primary mirror to collect and focus incoming light onto a flat diagonal secondary mirror which reflects the image to an eyepiece on the side of the optical tube.
A type of telescope that has a convex objective lens at the front end of a sealed tube and an eyepiece at the rear end. Refractors were the first telescopes and the image most people have when thinking of the word “telescope”.
The angular distance measured eastward along the celestial equator. It is the celestial equivalent of geographic longitude.
A type of catadioptric telescope design that uses a combination of a spherical primary mirror, a convex secondary mirror and a corrector plate (aspheric lens). Also known as an SCT.
A filter placed at the front of a telescope when viewing the Sun to block most its light. They are typically made from glass or plastic film. Failure to use a solar filter when your telescope is pointed at the Sun can cause severe eye damage and blindness.
The system of eight planets and their moons as well as dwarf planets, comets, asteroids and meteoroids that orbit the Sun.
The two times of the year when the Sun is at its most northerly or southerly point in the sky.
A type of optical aberration where a spherical mirror is unable to focus light to a single point. It can be eliminated by using a parabolic mirror.
A type of galaxy structure that has spiral arms extending from the galaxy’s center.
A luminous sphere of gas held together by its own gravity. Thermonuclear fusion of helium and hydrogen in its core produces energy. The Sun is the closest star to Earth.
A grouping of stars which are gravitationally bound. See ‘Globular Cluster’ and ‘Open Cluster’.
An accessory consisting of an angled mirror or prism that fits in the telescope’s focuser and accepts an eyepiece. It allows a more comfortable viewing angle especially when the telescope is pointed at or near the zenith.
A technique for locating faint celestial objects by using bright stars as a reference and a star chart.
A temporary dark spot that appears on the surface of the Sun. A sunspot has a reduced surface temperature compared to its surroundings. Sunspots can be viewed with a telescope using a proper solar filter.
Occurs when a full moon is also at its closest distance to Earth along its orbit.
A dying star that experiences a massive explosion which expels most of its mass. It appears as a very bright star before it fades away.
A reflex sight finder that doesn’t provide any magnification. It projects three red LED concentric circles onto the viewing window. This helps when star hopping as the circles aid in judging the angular distances between objects.
Moving the telescope in small increments as the earth rotates to keep the celestial object within the field of view.
When a celestial object appears to move across the surface of another celestial object, blocking a small part of it. Typically seen as Mercury or Venus transiting the Sun.
True Field of View
The angular size (in degrees) of the amount of sky that can be seen through an eyepiece when used with a telescope.
The imaginary point in the sky directly above the observer.
The area of the sky centered on the ecliptic along which the Sun, moon and most of the planets move over the course of a year. It is divided into 12 parts with each part named for a nearby constellation. | 0.886624 | 3.436867 |
Cosmic collision produces neutrino
The volatile particle collected by the IceCube detector probably comes from the turbulent centre of a faraway galaxy
It was quite a sensation in July 2018 when scientists reported that they had detected a highly energetic neutrino from a remote galaxy at the IceCube observatory at the South Pole about a year previously. It is said to come from an object designated as TXS 0506+056 – a very active faraway galaxy. An international team led by Silke Britzen from the Max Planck Institute for Radio Astronomy has now examined detailed radio observations of TXS 0506+056 from the years 2009 to 2018 and found an explanation for the neutrino activity. The cause is said to be a cosmic collision within the galaxy.
Conditions in objects such as TXS 0506+056 are turbulent. These active galactic nuclei (AGNs) are in actual fact the biggest sources of energy in the universe. Matter falls into central, supermassive black holes, whereby particle beams and plasma streams – so-called jets – are projected into intergalactic space.
The blazars, which send the jet directly towards the Earth and in so doing make the object appear particularly bright, form a special category of these AGNs. The neutrino event “IceCube-170922A” in September 2017 supposedly originated in this kind of blazar, designated as TXS 0506+056. It is approximately 3.8 billion light years away from Earth.
“It was somewhat of a mystery why it was possible to identify this particular galaxy as the source of the neutrino,” says Silke Britzen of the Max Planck Institute for Radio Astronomy in Bonn, who is also lead author of the recently published study. “That’s why we wanted to find out what makes TXS 0506+056 so special.” For this reason, the researchers investigated a time series of very detailed radio images of the galactic jet.
Surprisingly, an unexpected interaction appeared in the jet material coming from TXS 0506+056. While the plasma in the jet normally flows steadily in a kind of channel, in this galaxy the situation appears to be different. The increased neutrino activity during a neutrino eruption in 2014 and 2015 can evidently be traced back to a cosmic collision within the galaxy, as can the individual neutrino IceCube-170922A which was detected in 2017.
According to a scenario proposed by the astronomers, newly-created jet material comes into contact with an old jet, an assumption which appears to be supported by the strongly curved structure of the jet which has been observed. A second possible explanation is the collision of two jets in the same source. In any case, it results from a major collision.
“This collision of jetted material is currently the only viable mechanism which can explain the neutrino detection from this source,” says Markus Böttcher, a scientist at the North West University in Potchefstroom, South Africa. What does such a galactic jet consist of, however? Electrons and positrons? Or material which also contains protons? Or a combination of both? “Protons must at least be present in the material, otherwise we would not have detected the neutrino,” says Böttcher.
Collisions between entire galaxies appear to occur quite frequently in space. Based on the assumption that two galaxies colliding with each other is evidence of a supermassive black hole in the middle, the collision of these galaxies produces a pair of black holes, which circle each other at shorter and shorter distances and eventually merge into each other.
For a long time, astronomers have been looking for active galactic nuclei with two black holes at a relatively short distance from each other of just a few light years. However, they evidently occurred only very rarely and were also difficult to identify. In the case of TXS 0506+056, however, the researchers succeeded in doing so after finding signs of a procession of the central jet, meaning the jet changes its axis like a spinning top.
“This precession can be explained either by the presence of a supermassive black hole binary or the Lense-Thirring effect, as predicted by Einstein's theory of general relativity,” says Michal Zajaček from the Centre for Theoretical Physics in Warsaw, one of the authors of the study. The Lense-Thirring effect could in turn have been triggered by a second massive black hole at a greater distance in the centre of the galaxy.
Christian Fendt from the Max Planck Institute for Astronomy in Heidelberg is astonished. “The closer we get to the origin of the jet, the more complicated its inner structure and dynamic becomes. And the binary black holes mean that the material ejected from them must also have a complex structure.
In any case, for the first time, it appears to have been possible for the first time to confirm a collision between two jets in the heart of a galaxy just a few light years apart and to associate this with a cosmic neutrino.
HOR / NJ | 0.851943 | 4.074729 |
The new science fiction film "Passengers" takes viewers on a journey to the future, when glitzy interstellar starships can transport thousands of hibernating passengers to planets in neighboring star systems. While aspects of its story line may seem like pies in the sky to skeptics, creators of the futuristic space thriller certainly outdid its predecessors "Gravity" and "Interstellar" in the physics department.
"Passengers" is the story of two space travelers (played by Chris Pratt and Jennifer Lawrence) on an interstellar spaceship who wake up from an induced state of hibernation, or stasis, 90 years ahead of schedule. Unable to put themselves back into hypersleep, the two must come to terms with the knowledge that they will die on the spaceship before ever reaching their destination.
While the story is set way ahead of the current time and features technology that either doesn't exist yet or seems entirely out of reach, the makers of "Passengers" clearly took their science seriously. ['Passengers': An Interstellar Space Film in Pictures]
An 'Interstellar' journey
Rather than speeding through wormholes — theoretical tunnels that provide shortcuts through space and time — to hop from planet to planet like the astronauts do in the 2014 film "Interstellar," the sleeping astronauts aboard the spaceship Avalon in "Passengers" are traveling at one-half the speed of light. They're on a 120-year journey to an Earth-like planet called Homestead II that's located in a neighboring star system.
It's impossible to build spaceships that fast with today's technology, but the idea is more practical than the wormhole voyages depicted in "Interstellar." While scientists have yet to find evidence that such tunnels exist, traveling at a fraction of the speed of light is physically possible — at least theoretically.
But humanity has a long way to go before spacecraft will be able to travel as fast as one-half light speed. Light travels at over 670 million mph (1 billion km/h). The fastest machine humans have ever built was NASA's Juno spacecraft, and its top speed hit about 165,000 mph (265,000 km/h) relative to Earth.
The production designer for "Passengers," Guy Hendrix Dyas, came up with an original design for the fictional Starship Avalon that's based on the old concept of a vessel that rotates to create artificial gravity.
"I took the concept of the rotating wheel and stretched it out into an elongated shape, which naturally led to these wonderful, twisted blades," Dyas said in a statement. "When you look at the spacecraft from the front, it looks like this classic rotating wheel — but the moment you turn, it becomes a three-dimensional object of extraordinary length."
Spacecraft featured in "Gravity" and "Interstellar" certainly look more like those that exist today. "Gravity" showed NASA's space shuttle, the International Space Station, Russia's Soyuz spacecraft and China's Tiangong-1 space station. Astronauts in "Interstellar" ride a rocket that closely resembles NASA's Space Launch System (SLS). Even though the spaceship in "Passengers" seems totally out of this world in comparison, its design is still based on real, albeit incredibly futuristic, science.
It seems as though the makers of "Passengers" took note of some of the most commonly criticized scientific fallacies in "Gravity" and learned from those past mistakes to make their own film more accurate. You don't have to be a science-minded movie critic to rue the famous "Gravity" scene in which the character played by George Clooney (unnecessarily) falls to his death while breaking the laws physics in low-Earth orbit.
In that scene, George Clooney's character is dangling from a broken tether outside the International Space Station as Sandra Bullock's character holds onto the other end. Clooney's character insists that Bullock's let go of the tether to save her own life at the expense of his. In reality, she could have pulled him to safety in the zero-gravity environment by exerting hardly any effort. Instead, Clooney's character lets go and is flung into space by some mysterious unscientific force.
"Passengers" does not make the same mistake of sloppy tethering physics. When the characters, portrayed by actors Chris Pratt and Jennifer Lawrence, exit the ship in their spacesuits and float with their tethers in zero gravity, they don't appear to break any of Newton's laws of motion. The two tug on their tethers with ease while experiencing weightlessness.
In one scene, the two float together in space while connected by a long tether. When they drift apart, the tether straightens out entirely before jerking them back together. There is no tension on the tether, because there is no external force pulling them apart. "Gravity" got this basic physics concept totally wrong, so science-minded viewers should be glad that "Passengers" is setting the science straight.
While you might think that crying in weightlessness would send teardrops floating around inside an astronaut's helmet, that wouldn't happen. "Gravity" received some criticism for Bullock's floating teardrops, and "Passengers" does not repeat that mistake.
The problem with Bullock's tears in "Gravity" has little to do with a gravitational force. Rather, the producers did not take into account that water molecules stick together because of surface tension. In the case of an astronaut crying in space, surface tension would keep those tears stuck to the astronaut's cheeks. When Chris Pratt sheds tears during a zero-gravity scene in "Passengers," his tears stay stuck to his face — as they should.
These are but a few of the big scientific qualms that "Passengers" got right after Hollywood got it wrong in previous films. Critics will probably find other scientific points to nitpick in the film, but at the very least, it seems the makers of "Passengers" learned from the mistakes of other big Hollywood filmmakers. | 0.819824 | 3.165724 |
Now here’s a grand idea for a book: describe propulsion systems that can propel spacecraft with little or no fuel onboard. That’s just what Greg Matloff and NASA’s Les Johnson are doing with their new title Living Off the Land in Space (Copernicus & Praxis), which should be available come January. Matloff (New York City College of Technology) is well known in these pages as the co-author of The Starflight Handbook: A Pioneer’s Guide to Interstellar Travel (Wiley, 1989). It’s the seminal text, the one interstellar buffs return to again and again for the broad view of the kinds of technologies that might eventually get us to the stars.
Matloff produced The Starflight Handbook with the late Eugene Mallove and went on to write Deep Space Probes (Springer/Praxis 2000), now in its second edition. His new book with Johnson grows out of their work together in Huntsville at NASA’s In-Space Propulsion Technology Program, where mission concepts include everything from solar sails to solar electric, nuclear electric and other propulsion options. Can we one day make sails big enough to carry generation ships to other stars? Perhaps, but for now space trials of sail designs are what we shoot for, and even those are at least a decade off. That doesn’t stop the work from continuing.
If you’ve read The Starflight Handbook, you’ve seen the fine illustrations created by Greg’s wife C Bangs. Her work is exhibited on four continents as well as online, and she has appeared in numerous publications as well as doing work for a variety of NASA reports and workshop proceedings. I remember a wonderful dinner in Princeton with Greg and C where the discussion ranged from solar sails to the fascinating work going on at Princeton’s Engineering Anomalies Research program, where C had spent the afternoon.
For this is an artist whose fascination with the physics of consciousness propels her work. Her collaboration with the late Evan Harris Walker on quantum consciousness led her to incorporate his equations into many of her paintings, blending mythology with technology in absorbing ways. But this artist looks outwards as well as in. Her technology demonstrator of a rainbow hologram message plaque is a case in point. It could one day fly on an interstellar solar sail (think of the plaque on Pioneer), using images of the human form, a diagram of the Solar System and various equations describing the sail’s mission. That one grew out of a 2004 NASA grant.
Bangs’s “Dying/Evolved Star” paintings were recently exhibited in Brooklyn. And if you make the trip to Huntsville, you can view her holographic designs on display at Marshall Space Flight Center, where Les Johnson has the pleasure of seeing them every day. I like what Matloff says about his relationship with Bangs: “We sometimes edit each other’s writing, and that can add sparks — but in this case they’re good ones. We’re generally working from different hemispheres: C is very much tapped into the left and I, the right.”
That seems like a solid combination to me. You should hear these two in conversation — the ideas are electric.
As to Matloff’s current work, he’s active with both NASA and the Italian space program and continues research on solar sail technologies. And talk about living ‘off the land’ — Matloff and Johnson have kicked around concepts for using large solar sails embedded with electrodynamic tethers to propel spacecraft deep into the Solar System, drawing on the magnetic fields around the destination planets to capture them into orbit. That’s living with little fuel indeed, and less is more when it comes to deep space, where minimizing your fuel consumption pays off in bigger and better payloads.
Image credit: Michele Forsten for NYC College of Technology. | 0.826826 | 3.119047 |
Thanks to Camilo Urban for the following post.
Leif Holmlid just got published an open access article that proposes theory from experimental results to explain Dark Matter as being formed by ultra dense hydrogen, and provide experimental basis for a reinterpretation of red shift and cosmic background noise that put the Big Bang idea to rest.
In certain ways is parallel to Mills hydrinos, and besides the monumental cosmological implications it also has monumental energy production implications.
50 experimental publications exist on ultra-dense hydrogen H(0) from our laboratory. A review of these results was published recently (L. Holmlid and S. Zeiner-Gundersen in Phys. Scr. 74(7), 2019, https://doi.org/10.1088/1402-4896/ab1276). The importance of this quantum material in space is accentuated by a few recent publications: The so called extended red emission (ERE) spectra in space agree well (L. Holmlid in Astrophys. J. 866:107, 2018a) with rotational spectra measured from H(0) in the laboratory, supporting the notion that H(0) is a major part of the dark matter in the Universe. The proton solar wind was shown to agree well with the protons ejected by Coulomb explosions in p(0), thus finally providing a convincing detailed energy mechanism for the solar wind protons (L. Holmlid in J. Geophys. Res. 122:7956–7962, 2017c). The very high corona temperature in the Sun is also directly explained (L. Holmlid in J. Geophys. Res. 122:7956–7962, 2017c) as caused by well-studied nuclear reactions in H(0). H(0) is the lowest energy form of hydrogen and H(0) is thus expected to exist everywhere where hydrogen exists in the Universe. The so called cosmological red-shifts have earlier been shown to agree quantitatively with stimulated Raman processes in ordinary Rydberg matter. H(0) easily transforms to ordinary Rydberg matter and can also form the largest length scale of matter, with highly excited electrons just a few K from the ionization limit. Such electronic states provide the small excitations needed in the condensed matter H(0) for a thermal emission at a few K temperature corresponding to the CMB, the so called cosmic microwave background radiation. These excitations can be observed directly by ordinary Raman spectroscopy (L. Holmlid in J. Raman Spectrosc. 39:1364–1374, 2008b). A purely thermal distribution from H(0) and also from ordinary Rydberg Matter at 2.7 K is the simplest explanation of the CMB. The coupling of electronic and vibrational degrees of freedom observed as in experiments with H(0) gives almost continuous energy excitations which can create a smooth thermal CMB emission spectrum as observed. Thus, both cosmological red-shifts and CMB are now proposed to partially be due to easily studied microscopic processes in ultradense hydrogen H(0) and the other related types of hydrogen matter at the two other length scales. These processes can be repeated at will in any laboratory. These microscopic formation processes are much simpler than the earlier proposed large-scale non-repeatable processes related to Big Bang. | 0.83491 | 3.950234 |
A Galactic Center Excess in the Andromeda Galaxy M31 Seen with the Fermi -LAT
2017 December 12
The Fermi Large Area Telescope (LAT) has opened the way for comparative studies of cosmic-ray populations and high-energy sources in the Milky Way (MW) and in other external star-forming galaxies. Using more than seven years of LAT Pass 8 data in the energy range 0.1 − 100 GeV, M31 is detected at nearly 10σ and is observed to be extended at 4σ. Its spectrum is consistent with a power law and its spatial distribution is consistent with a uniform brightness disk over the plane of the sky and no offset from the center of M31. The emission appears confined to the inner regions of the galaxy and does not fill the disk of the galaxy. The non-correlation with regions rich in gas or star-formation activity suggests that the emission is not interstellar in origin, unless the energetic particles radiating in gamma rays do not originate in recent star formation. Alternative interpretations include a population of unresolved millisecond pulsars in the galaxy center or dark matter annihilation or decay, similar to what has been proposed to account for the Galactic center excess found in LAT observations of the MW. | 0.84634 | 3.647676 |
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