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A few years ago, the Hubble Space Telescope did something amazing: over the course of 841 orbits and hundreds of exposures, it imaged a tiny region of space in the constellation of Fornax, peeling back the layers of time by 13 billion years, to just a few hundred million years after the Big Bang.
It's called the Hubble Ultra-Deep Field 2014 (HUDF), and it's one of the most breathtaking mosaics the telescope has produced. In it, around 10,000 galaxies gleam - a feast for astronomers exploring the early Universe.
Now a team of astronomers has made the image even better. Over the course of three years, scientists at the Instituto de Astrofísica de Canarias (IAC) developed and applied an image processing technique designed to draw out the unseen light in the HUDF.
They called this complex technique ABYSS, and with it they have recovered the dim light from the outer edges of the largest galaxies in the image.
"What we have done," explained IAC astrophysicist Alejandro S. Borlaff, "is to go back to the archive of the original images, directly as observed by the HST, and improve the process of combination, aiming at the best image quality not only for the more distant smaller galaxies but also for the extended regions of the largest galaxies."
So far, the results have revealed that at least some of these galaxies are much bigger than thought, with diameters up to twice as large as previous estimates.
But the paper published by the team wasn't for the purpose of making these discoveries, but describing how ABYSS works.
The have published the enhanced images they generated, and have plans to publish the calibration files and the ABYSS pipeline so that the community can use the tools themselves, and help develop further refinements. | 0.824902 | 3.642802 |
Pluto was discovered in 1930 by Clyde Tombaugh, and first visited by the New Horizons spacecraft in 2015. We originally thought the Solar System only had two zones: the inner rocky planets and the outer gas and ice giants, Pluto didn’t fit. Pluto and the other small icy bodies discovered afterwards define what we now know as the Solar System’s third zone, called the Kuiper Belt. New Horizons showed us that Pluto has tall mountains made of water ice, very bright areas, and dark reddish areas. Sputnik Planitia* is a big low plain of frozen Nitrogen, and Nitrogen glaciers flow into it from the east. Charon’s water ice surface expanded long ago, stretching apart to leave big cracks and cliffs.
Description of Pluto and Charon
- Body type: double planet (Pluto and Charon) and irregular moons
- Body composition: icy
- Atmosphere: Pluto: thin, blue, mostly nitrogen, Charon: none
- Endogenic features: long and deep fractures
- Exogenic features: Pluto: ice plains (different ices mixed: nitrogen, methane, CO), glaciers, glacial valleys, pits. Charon: none
- Cosmogenic features: Impact craters. Charon: red tholin “cap” may be sourced from Pluto
- Common features: craters, cracks, ices
- Rare features: valleys, nitrogen glaciers, water ice icebergs
- Life limiting parameter: too cold
- Nomenclature*: The names on Pluto and Charon are informal, and include characters, creatures, and places from the underworld; explorers that crossed ‘new horizons’ in their own ways; scientists and engineers that have studied Pluto; fictional explorers, vessels, and places; and artists and authors associated with space exploration.
- Age: cratered terrains on both Pluto and Charon are 4 Gyr old, but smooth ice plains on Pluto are very young.
- Highest point: to be determined. Sputnik Planitia is a deep and very smooth surface. Large cracks on Charon had >10 km high steep slopes. Water ice, the material of rocks, is granite hard at these very low temperatures.
Pluto-Charon map: (Illustrator: Adrienn Gyöngyösi). The map uses the theme of Halloween that is the closest to the Greek underworlds myths. Unlike other maps, this map depicts only one hemisphere of two bodies because only one hemisphere was photographed in detail when New Horizons flew by the system. The sizes of Pluto and Charon are to scale. The southern polar areas were in darkness so it is completely unknown. The four other, small and irregular moons are also shown on the map with the mythological character they were named for. The surface of Pluto and Charon is both composed of water ice rocks, and in places a reddish brown material is covering it. This material is called tholin and is produced in the atmosphere as the Sun’s radiation interacts with atmospheric molecules. The left “lobe” of the large “heart” shaped bright feature is partially a large, deep, ancient, elliptical impact basin filled with ice. There are four kinds of ices on Pluto: nitrogen, methane and carbon-monoxide ices in addition to the bedrock, which is water ice. In the past, the extent of ice cover was different. Pluto has a very elliptical orbit around the Sun so some of its ices may sublimate when it’s closest to the Sun. Pluto and Charon are tidally locked to each other so they turn the same side towards each other and they orbit around their common center of mass, an invisible point between Pluto and Charon. The small satellites are affected by both Pluto’s and Charon’s gravity (depending on when they are closer to which) so their orbit and rotation is somewhat irregular.
Main text written by Ross Beyer. | 0.844391 | 3.681604 |
Advancing Basic Science for Humanity
12/09/2019 - Weather Forecast in Galaxy Clusters: Little Chance for Starmaking
By Adam Hadhazy
Scientists want to explain the patterns of star formation we observe in the universe. Our nearest star, the sun, seen here by NASA’s Solar Dynamics Observatory is emitting a dazzling solar flare.
The recipe for making stars out in space is about as uncomplicated as cooking up a batch of ramen noodles here on Earth. Simply take some gas, mostly hydrogen and helium, add in a pinch of heavier elements if you like, cool it all down, and then let gravity go to work. As the gas clumps together under gravity's attraction, it grows denser and warmer. The center of the congealing gas-knot eventually grows hot enough for the gas atoms to collide and fuse, releasing energy and light that counteract the gravitational collapse. Presto, you've got a star—a stable, glowing orb that will blaze forth (in most cases) for billions of years.
Seeing how straightforward it is to make stars, you'd be correct in assuming the universe produces loads of them. Indeed—galaxies, which themselves number in the hundreds of billions, usually minimally contain millions of stars, and in some instances up to a trillion.
Yet a relatively gas-rich place where stars seemingly ought to form, in the regions between galaxies that populate galaxy clusters, is pretty much a starless wasteland. New research by Kavli Institute for Cosmology, Cambridge (KICC) scientists is helping to solve this mystery, with tie-ins to how galaxies overall assume their distinctive shapes.
The gas outside of galaxies that is associated with the galaxies' resident cluster is known as the intracluster medium, or ICM for short. In general, it exists as a hot, energized gas called a plasma, which is what stars are made out of, but is the opposite of the cool gas needed to make stars in the first place. Still, one would expect the ICM to chill out over time, especially toward the denser environment of a galaxy cluster's core. Yet any starmaking that happens in galaxy clusters is confined to the galaxies themselves.
Something, then, is keeping the ICM hot and bothered. That something is thought to be supermassive black holes, found at the centers of most galaxies. As these powerful objects devour matter, they send out intense jets of energy that run clear out of the galaxy and into the ICM. Hot lobes of gas form at the ends of these jets. Yet in ways heretofore unclear, the heat in those lobes must distribute throughout the ICM to keep the whole of it unsuitably toasty for crafting stars.
"What people have been trying to figure out is how exactly this heating process works," says Martin Bourne, lead author of a recent study and a postdoctoral research associate at the Institute of Astronomy (IoA) at the University of Cambridge and a member of KICC.
Along with senior paper author Debora Sijacki, an astrophysicist and cosmologist at KICC and IoA, as well as a former KICC colleague, Bourne ran high-powered computer simulations modeling the black hole jets' lobes. The model simulated the sort of observable X-ray signatures the lobes would be expected to produce as they interact with the ICM. The researchers knew they'd gotten it right when the simulations matched up well with real observations of galaxy clusters.
From there, the team put together a plausible explanation for how the heat in the lobes spreads out amongst the ICM. It turns out that terrestrial weather offers a good analogy. The galaxies in a cluster are always in motion about each other. The ICM itself, being a turbulent gas, also does not stay still. Together, these motions stir the hot lobes, mixing their heated material in with the otherwise-cooling regions of the ICM. As a result, the ambient ICM gas remains too warm to settle down into stars. The process is akin to the generation of wind, and in the case of the cluster environment, gales of material blow about at over 1000 kilometers per second.
"The key thing that we have found is that it is not just about injecting a lot of energy," says Bourne. "We also need the cluster to help release and redistribute this energy, which is where the cluster weather comes in."
Notably, this extragalactic result fits squarely with the increasingly well-developed paradigm of how supermassive black holes' energetic outpourings quench star formation inside galaxies as well. A basic dividing line between galaxies is that separating young, starforming, more-bluish-in-color types from old, quiescent, more-reddish-in-color types. (Regions of fresh star formation produce bright blue stars, while older stars are generally reddish in color.) The activity of a galaxy's central black hole is a major determinant of whether a galaxy stays young or transitions into old age.
"Feedback from supermassive black holes is believed to be one of the key ingredients to understand cosmic structure formation and more specifically the evolution of galaxies," says Sijacki.
Researchers are keen to nail down the apparently colossal impact black holes have on their host galaxies, their cluster environments, and extending from there, to the whole of cosmic structure and organization. Accordingly, expect much more research in this vein, Sijacki says.
"Over the last four years of intense research, we have developed new computational methods to simulate supermassive black hole jets with unprecedented resolution and fidelity," she says. "Our goal is to push cosmic structure simulation to the next level of realism and re-assess the current paradigm of how galaxies form and evolve."
When it comes to comprehending galactic phenomena, Sijacki offers another analogy to frame the advances recently made in the field of supercomputing: "It's a bit like transitioning from a Beetle to a Ferrari in our race to understand the physics behind this all." | 0.868707 | 3.858108 |
Astronomers using ESO telescopes and other facilities have found clear evidence of a planet orbiting the nearest star to our own Sun, Proxima Centauri. The long-sought world, designated Proxima b, orbits its cool red parent star every 11 days and has a temperature possibly suitable for liquid water to exist on its surface. This rocky world is a little more massive than the Earth and is the closest exoplanet to us — and it may also be the closest possible abode for life outside the Solar System. A paper describing this milestone finding will be published in the journal Nature on 25 August 2016.
Just over four light-years from the Solar System lies the red dwarf star named Proxima Centauri as it is the closest star to Earth apart from the Sun. This cool star, in the southern hemisphere constellation of Centaurus, is too faint to be seen with the unaided eye and lies near to the much brighter pair of stars known as Alpha Centauri AB.
During the first half of 2016 Proxima Centauri was regularly observed with the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile and simultaneously monitored by other telescopes around the world. This was the Pale Red Dot Campaign, in which a team of astronomers led by Guillem Anglada-Escudé, from Queen Mary University of London, was looking for the tiny back and forth wobble of the star that would be caused by the gravitational pull of a possible orbiting planet.
As this was a topic with very wide public interest, the progress of the campaign between mid-January and April 2016 was shared publicly as it happened on the Pale Red Dot website and via social media. The reports were accompanied by numerous outreach articles written by specialists around the world.
Guillem Anglada-Escudé explains the background to this unique search: “The first hints of a possible planet were spotted back in 2013, but the detection was not convincing. Since then we have worked hard to get further observations off the ground with help from ESO and others. The recent Pale Red Dot campaign has been about two years in the planning.”
The Pale Red Dot data, when combined with earlier observations made at ESO observatories and elsewhere, revealed the clear signal of a truly exciting result.
At times Proxima Centauri is approaching Earth at about five kilometers per hour — normal human walking pace — and at times receding at the same speed. This regular pattern of changing radial velocities repeats with a period of 11.2 days. Careful analysis of the resulting tiny Doppler shifts showed that they indicated the presence of a planet with a mass at least 1.3 times that of the Earth, orbiting about seven million kilometers from Proxima Centauri — only five percent of the Earth-Sun distance.
Guillem Anglada-Escudé comments on the excitement of the last few months: “I kept checking the consistency of the signal every single day during the 60 nights of the Pale Red Dot Campaign. The first 10 were promising, the first 20 were consistent with expectations, and at 30 days the result was pretty much definitive, so we started drafting the paper!”
Red dwarfs like Proxima Centauri are active stars and can vary in ways that would mimic the presence of a planet. To exclude this possibility the team also monitored the changing brightness of the star very carefully during the campaign using the ASH2 telescope at the San Pedro de Atacama Celestial Explorations Observatory in Chile and the Las Cumbres Observatory telescope network. Radial velocity data taken when the star was flaring were excluded from the final analysis.
Although Proxima b orbits much closer to its star than Mercury does to the Sun in the Solar System, the star itself is far fainter than the Sun. As a result Proxima b lies well within the habitable zone around the star and has an estimated surface temperature that would allow the presence of liquid water. Despite the temperate orbit of Proxima b, the conditions on the surface may be strongly affected by the ultraviolet and X-ray flares from the star — far more intense than the Earth experiences from the Sun.
Two separate papers discuss the habitability of Proxima b and its climate. They find that the existence of liquid water on the planet today cannot be ruled out and, in such case, it may be present over the surface of the planet only in the sunniest regions, either in an area in the hemisphere of the planet facing the star (synchronous rotation) or in a tropical belt (3:2 resonance rotation). Proxima b’s rotation, the strong radiation from its star and the formation history of the planet makes its climate quite different from that of the Earth, and it is unlikely that Proxima b has seasons.
This discovery will be the beginning of extensive further observations, both with current instruments and with the next generation of giant telescopes such as the European Extremely Large Telescope (E-ELT). Proxima b will be a prime target for the hunt for evidence of life elsewhere in the Universe. Indeed, the Alpha Centauri system is also the target of humankind’s first attempt to travel to another star system, the StarShot project.
Guillem Anglada-Escudé concludes: “Many exoplanets have been found and many more will be found, but searching for the closest potential Earth-analog and succeeding has been the experience of a lifetime for all of us. Many people’s stories and efforts have converged on this discovery. The result is also a tribute to all of them. The search for life on Proxima b comes next…” | 0.90723 | 3.821311 |
One Night Only, a New Meteor Shower that May Be Spectacular?
Ladies and Gentleman, Boys and Girls: One night only, May 23/24, the challenger -- Comet 209P/LINEAR dusty debris vs. the champion--planet Earth, smackdown! Be there!
Alright, it won’t be much of a fight since all the comet debris will burn up high in the Earth’s atmosphere, but as it does so, it still could make for a spectacular event to watch. A new meteor shower, the Camelopardalids, will be peaking Friday night/Saturday morning (May 23/24, 2014) just after midnight Pacific time. If you are in the U.S. or southern Canada, you are likely well positioned to see what may (or may not) be a spectacular show. In either case, scientists will learn about a comet’s history and you can have a fun night looking at the sky.
Meteor showers happen when Earth passes through the debris shed from a comet. When that debris (usually dust and sand sized) hits the Earth’s atmosphere at tens of kilometers per second, it heats up due to friction and glows, making a streak across the sky we call a meteor.
The debris comes from Comet 209P/LINEAR which was discovered in 2004. Esko Lyytinen and Peter Jenniskens looked at the comet’s orbit and expected orbital evolution and predicted this week’s shower. Their orbital predictions have been confirmed by others as well, including Jeremie Vaubaillon who calculated that all dust trails of the comet created between 1803 through 1924 will be in Earth's path for the 2014 encounter. What no one knows for sure, because we don’t have the data needed to predict, is how many meteors will there be per hour: a few, tens, hundreds, or even thousands, which would qualify it as a meteor “storm.”
The Tale of a Comet
“Keep your expectations low…but don’t miss it.”
I talked to co-predictor of the shower Peter Jenniskens from the SETI Institute, and he had the following sage advice about the shower, “Keep your expectations low…but don’t miss it.” From him, I learned many other interesting things about this unusual celestial show, including the following:
This meteor shower is unusual. This will be the first time Earth will pass through that comet’s orbit at this time of year, AND this will be the only time we are predicted to pass through dense debris clouds near the comet itself. The comet itself will pass through this same region on May 29. Debris clouds, since they come from material shed from the comet itself, tend to concentrate near the comet in its orbit and gradually spread out. Since this debris cloud represents material shed in about the last two hundred years of passes in towards the Sun, it has not spread out much and may remain quite dense. The comet’s orbit evolves naturally over time, bringing Earth through this comet orbit for the first time this year. We will continue to pass through this comet and debris orbit until 2044 when they evolve out beyond Earth’s orbit. However, only in 2014 will we pass so close to the comet and thus so close to the debris cloud that makes for many happy meteors. So…don’t miss it. In future years, there will likely be only a wee bit to no shower. More broadly, this type of pass from a member of this family of comets doesn’t happen often…
This comet is a Jupiter family comet, meaning it goes out to near the orbit of Jupiter on the outer part of its orbit. Thus, Jupiter family comets have orbital periods of only a few to many years – 5.1 years in the case of this comet. That means they come towards the Sun every few years, and that means their ices sublimate (turn from ice to gas) regularly under the increased heat. And, that means they end up not very productive in terms of additional gas and associated dust output, which could be a bad sign for our meteor shower potential. No matter what, Peter says that the results will provide good science, providing insight into the dust output of this comet over the last couple hundred years and from that, insight into the nature of the Jupiter family of comets.
Because they have such frequent visits to the inner solar system, Jupiter family comets actually provide 85% of the material in the ‘zodiacal cloud,’ not a terrifying undead swarm as it may sound, but instead a pancake shaped cloud of dust in the inner solar system that can be seen from dark sites as a faint diffuse glow along the ecliptic (path of the Earth’s orbit) in the night sky. This makes what we learn from our friend Comet 209P/LINEAR even more significant.
Because we are passing through the debris of the last couple hundred years that, as mentioned, hasn’t had time to spread out much, the peak of the meteor shower will be much shorter (a couple hours?) than ones we are usually familiar with (often spread over days due to more debris over longer time in more stable orbits).
Even if there are not a lot of meteors, the meteors there are may be particularly beautiful due to two factors. The one we are certain of is the relative speed at which they will hit the atmosphere: 19.4 km/s, which, though amazingly fast by human standards, is slow by meteor shower standards, meaning the meteors will appear to glide rather than streak across the sky, to use rather non-technical terms. Secondly, which is more uncertain, Quanzhi Ye (who as an 18 year old was a Planetary Society Shoemaker NEO Grant winner) and Paul A. Wiegert looked at the activity of the comet on its last orbit and found that some of the particles ejected are relatively large, which still means pretty small particles that will burn up high in the atmosphere, but the increase in size means they will look brighter doing it.
The estimated size of this comet just went up considerably in the last couple weeks due to the better observing geometry allowing for better observations. The comet is now estimated to be between 1.9 and 4.9 km, which, Peter says, makes it a garden variety Jupiter family comet.
Another note: the comet pass by Earth will be the 9th closest comet pass on record (counting only those with reliable orbits), but still more than 21 Earth-Moon distances. However, due to its low output of dust and gas making for a small coma/tail, the comet itself is predicted to be very dim, requiring a good amateur telescope to be able to see it.
When and From Where to Look
The meteor shower peak is predicted to be about 07:20 UT (00:20 PDT) on Saturday May 24, so shortly after midnight Pacific time on the night that starts on Friday May 23. If you are going to devote only a small amount of time to this endeavor, your best bet is to focus on the time around that peak time, perhaps an hour before and after if you have the time and patience. More time will increase your chances, particularly due to uncertainties. Because of the timing, the expected sharpness of the peak, and the meteors coming from roughly the north, the United States and some of Canada are the favored locations for observing. The Moon is not up until later in the night, making for incredibly lucky dark sky conditions.
The Camel Leopard: Where to Look in the Sky
Meteor showers are named after the constellation that contains the radiant of the shower. The radiant is where the meteors appear to emanate from: if you draw a line back along the meteors, all of the lines will meet at a point. It is an effect of us (Earth) moving through a discrete cloud of stuff. This shower’s radiant will be in a rather dim constellation that makes up for it with a really long name, Camelopardalis, which is not too far from the North Star, the Big Dipper, and rest of the gang up by the North celestial pole. (Random Space Fact: Camelopardalis comes from Latin derived from Greek for giraffe, which was a compound of camel leopard, so named because the giraffe had the long neck of a camel and the spots of a leopard.) What this location means for the North America observers that are favored by the time of the event is that you can look most anywhere in the sky. Ideal is often said to be 45 degrees away from the radiant, but probably more important is to find the darkest place you can, don’t have a light in your eyes, and look at the darkest patch of sky you can.
How Good Will the Shower Be?
In terms of science, the shower should be great. In terms of how many meteors people will see, it is uncertain because of how little we know about how much dusty stuff got kicked off the comet in the last couple hundred years. Predictions range from tens to thousands per hour, with most in the 50 to 200 per hour range from a dark site. For comparison, the best “normal” meteor shower of the year is usually the Geminids with a peak of about 100 per hour from a dark site.
We’ve got a dark sky due to lack of moonlight and a pass through a hopefully high density debris relatively near the comet itself, weighed against the Jupiter family comets being notoriously low producers of dust (we think). The only way to find out the answer to how many meteors will there be will be to watch the event itself, or find out from someone else, but that is not nearly as fun. If you can’t watch your own sky due to location or clouds, some groups are broadcasting live web feeds including Planetary Society Shoemaker NEO Grant winner Gianluca Masi. He has teamed with several observers in the U.S. and Canada to have images online at his Virtual Telescope page. Several sites will also post near real time updates on the shower in the hours around the peak including the SETI Institute Meteor Showers page and links therein. | 0.864074 | 3.575315 |
Unravelling the mysteries of extragalactic jets
University of Leeds researchers have mathematically examined plasma jets from supermassive black holes to determine why certain types of jets disintegrate into huge plumes.
Their study, published in Nature Astronomy, has found that these jets can be susceptible to an instability never before considered as important to the jet’s flow and is similar to an instability that often develops in water flowing inside a curved pipe or a rotating cylindrical vessel.
Dr Kostas Gourgouliatos conducted this research while based in the School of Mathematics at Leeds. He is now based at Durham University. He said: “These jets have a narrow oval shape which gives them a curved boundary. It is this shape that creates a weak point in the jet.
“Instability starts at the curved boundary, travels upstream on the jet and then converges at one point — what we refer to as the ‘reconfinement point’. Below this point the jet stays tidy and tight but everything above will be destroyed and creates a large cosmic plume.
“When the jet disintegrates into a plume it releases heat, making them easier to spot on telescopes. The jets and their plumes are so bright that sometimes they outshine their host galaxies and are always more easily spotted than black holes, which are inferred indirectly, in space observations.”
The study explains why the extragalactic jets, which at first appear remarkably stable, may become suddenly disrupted and produce plume-like structures.
Study co-author Professor Serguei Komissarov, also from the School of Mathematics, said: “We did expect instability associated with velocity shear to develop at the jet reconfinement but not as fast.
“Moreover, the observed instability exhibited some rather unexpected features. In turned out that it was related to the centrifugal force acting on the fluid elements travelling along curved streamlines. This centrifugal instability is well studied but nobody expected it to be important for the jet dynamics.”
The research paper, Reconfinement and Loss of Stability in Jets from Active Galactic Nuclei, is published on Nature Astronomy 11 December 2017. (DOI: 10.1038/s41550-017-0338)
For additional information and to request interviews please contact Anna Harrison, Press Officer at the University of Leeds, on +44 (0)113 34 34196 or [email protected]
The authors acknowledge Science and Technology Facilities Council grant ST/N000676/1. Simulations were performed on the Science and Technology Facilities Council-funded DiRAC/UK Magnetohydrodynamics Science Consortia machine, hosted as part of and enabled through the Advanced Research Computing high-performance computing resources and support team at the University of Leeds.
Image: By NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA) (http://www.spacetelescope.org/images/opo1247a/) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons | 0.862555 | 3.830787 |
A while back, I wrote about a very exciting if baffling new space propulsion system: the EmDrive. It’s a space propulsion system that doesn’t appear to use any propellant, maybe violates the known laws of physics, but somehow seems—according to a number of tests—to actually work. Physicist M.E. McCulloch released a possible explanation, but it just brings up more questions.
When I say that it brings up more questions, I mean that to me it brings up dog-like head tilts as my feeble brain tries to process the complex explanation.
The EmDrive is a new form of spacecraft propulsion technology that would run on solar power, uses essentially no fuel, and allows for speeds that could get us to Mars in about 10 weeks, significantly faster than the current transit time of about 260 days.
That all sounds great! But maybe too great. The problem is the drive seems to violate accepted rules of physics. The EmDrive works by bouncing microwaves around an enclosed chamber, and not the usual action/reaction method of chemical thrusters or even ion engines. It’d be like being able to drive by pushing really hard on the steering wheel. It just doesn’t seem to make sense.
And yet, several teams, building their own copies of the EmDrive, have been able to measure thrust. We don’t have a peer-reviewed paper yet, but something is being measured, and right now nobody’s sure what’s going on.
But there is that new theory I mentioned above.
Thankfully, to explain what this new theory is explaining, we don’t have to rely on my factory-remaindered brain; we have access to the brain (and associated bodily housing) of our tame physicist, Dr. Stephen Granade.
I asked Dr. Granade if he could help us evaluate how MIT Technology Review is explaining McCullough’s theory of how the EmDrive could work, and the strange connection they’re making with the so-called “Pioneer Anomoly.” The explanation MIT gives is interesting, but, as you’ll see here, it conflicts with a lot of what’s known about relativity, and sort of makes Einstein into a filthy liar. Sort of.
Other outlets are talking about MIT’s explanation and theories, but I think it’s compelling enough for us to try and take a deep look at what may be happening.
I do hope eventually this thing is proven to work, but until then, here’s what someone smarter than me can tell us about it.
Essentially, what Dr. Granade has deduced is that McCulloch’s theory relies on an obscure form or radiation and, and here’s the big part, that gravitational and intertial mass are not the same. Right now, for the accepted general relativity to work, they would need to be the same.
If inertial mass is less than gravitational mass, as is suggested here, you’d need less force to overcome inertia and get the body in motion. So, the EmDrive might sort of be acting as an intertial-mass reduction device, which could produce thrust via the pressure of that obscure radiation? I think?
Read what the good doctor has to say for yourself:
Dr. Mike McCulloch has a theory that he claims can explain why the EmDrive could be producing thrust when so many people say it can’t. However, instead of solving the EmDrive puzzle, for me his claims only raise even more questions that need to be answered.
To explain why, I’m going to have to dive into his theory and explain as best I can what he says is going on. Once I’ve done that, I can talk about the consequences of his theory and why I’m cautiously skeptical about his claims. If you don’t have time for my full explanation, here’s my summary:
I’ve got a lot of unanswered questions about McCulloch’s theory, not least of all because his theory would break a lot of existing physics theories without fully extending them the way that general relativity extended Newtonian mechanics. And besides, we’re still waiting on good confirmation that the EmDrive’s thrust truly exists.
All right, still with me? Cool. Let’s do this.
McCulloch’s theory is called “quantized inertia,” or more formally, “Modified inertia by a Hubble-scale Casimir effect.” To explain his theory, I need to talk about quantization.
Take a guitar string and put your finger on it just above one of the frets. Strum the string. The two ends of the string can’t move, because you’ve got your finger on one end and the other end’s fixed by the guitar’s bridge. That limits how the string can vibrate. It can vibrate so that its middle moves back and forth the most, with the two ends not moving. (The non-moving points are called nodes.) Or it can vibrate so that the points that are 1/6, 3/6, and 5/6 along the string move back and forth the most, while the two ends and the points that are 2/6 and 4/6 along the string don’t move. The string can vibrate any way...as long as the two ends of the string don’t move and remain a node. That requirement means that the string can only vibrate with no node in between the ends, or a node at 1/2 the way along the string, or nodes at 2/6 and 4/6 along the string, or nodes at 2/8, 4/8, and 6/8 along the string...
The ways the guitar string can vibrate are quantized. There’s a limited and regularly-spaced set of modes the wave can take. McCulloch’s theory involves a similar kind of quantization, except he’s talking about quantized waves inside a cavity. And instead of vibrating guitar strings, he’s talking about waves of electromagnetic radiation that only appear when you’re speeding up, thanks to something called the Unruh effect.
If you accelerate in space, where there’s no atmosphere or other particles around, then you’ll see space around you appear to get warmer. You’ll be heated up by particles that, if you weren’t speeding up, you wouldn’t experience. In other words, if you strapped a thermometer to a rocket and let it blast through space, it’d record a warmer temperature than one that wasn’t blasting through space. It’s a weird consequence of quantum mechanics, but it’s a well-accepted one.
Here’s where McCulloch’s theory comes in. McCulloch claims that something being accelerated will encounter more Unruh radiation coming at it head-on than it will from behind, pushing back against its acceleration1.
This, McCulloch claims, is where inertia comes from. He also claims that, when an object’s only accelerating a little bit, the Unruh radiation coming at the object head on decreases, so it doesn’t experience as much inertia as normal.
If this is true, then general relativity is broken. For general relativity to work, inertial mass and gravitational mass have to be the same.
“Wait,” you may be saying, “there are different kinds of mass?” Yep! A bathroom scale measures gravitational mass: how much the Earth pulls on an object compared to an object whose mass is known, like the standard kilogram. Inertial mass is a measure of how much an object resists being accelerated by a force. An object with more inertial mass will be accelerated less by a force than an object with less inertial mass.
General relativity claims that the two are exactly equivalent. According to general relativity, if I put you in a closed elevator, you can’t tell if you’re being accelerating through space at 9.8 meters per second squared, or if I’ve put the elevator on the surface of the Earth where gravity is accelerating you by 9.8 meters per second squared.
McCulloch’s theory claims that gravitational mass and inertial mass can be different. Your inertial mass depends on how fast you’re accelerating. At low accelerations, your inertial mass is supposedly less.
Experimenters have tested to see if the gravitational and inertial masses are the same lots of times. We’ve even looked for a the difference by effectively dropping the Earth and the Moon towards the Sun As far as we can tell, gravitational mass and inertial mass are the same to a ridiculously high precision.
Even worse, McCulloch’s theory can only explain the EmDrive effect if you assume that photons, the particles that make up light and other electromagnetic waves, have mass when they’re not moving. If photons have this kind of mass, then according to general relativity, they can’t move at the speed of light. We’ve measured how close to zero the photon’s mass is and the answer so far is “very, very, very close to zero if not exactly zero.”
It’s always possible that McCulloch is right, assuming that the EmDrive’s anomalous thrust actually exists. But right now we have no good confirmation of the EmDrive’s thrust. Since I last talked about the EmDrive at Jalopnik, Paul Marsh of NASA’s Eagleworks has posted on a forum that an updated peer-reviewed paper is coming. But until that paper comes out, we don’t know much more than we did back then, and the EmDrive’s thrust remains speculative.
To me, McCulloch’s attempt to explain the EmDrive feels similar to how, in the wake of the discovery that the Pioneer space probes were being slowed down by a constant deceleration, scientists came up with all kinds of possible explanations for the Pioneer anomaly. But when researchers recovered a lot more data from the probes, they found that the deceleration wasn’t constant like they’d originally thought. Eventually they found that thermal effects from the spacecraft’s power sources and internal battery were the most likely explanation for the slow-down.
The EmDrive could really be producing thrust, and Mike McCulloch’s theory could truly explain that thrust. I hope they’re both true! New physics is great!
But without more solid proof, I’m not ready to accept either of them just yet.
McCulloch’s reasoning has to do with something called the Rindler horizon. When you’re constantly accelerating, there’s a boundary behind you in a combination of space and time where nothing, not even light, can catch up to you. McCulloch claims that the radiation will be quantized between you and the Rindler horizon behind you, and it’ll be separately quantized between you and the Hubble horizon in front of you. Because the Rindler horizon’s a lot closer to you than the Hubble horizon (which is near the edge of the observable universe), you can’t fit as many different quantized modes of radiation between you and the Rindler horizon behind you than you can between you and the Hubble horizon ahead of you. In the guitar example, it’s the difference between holding a fret near the body versus far out on the neck.
I’m extremely skeptical about this, because it’s not clear at all why you’d act like a finger on the guitar string. If anything, I’d expect the waves would only be quantized between the Rindler horizon behind you and the Hubble horizon in front of you, without you being involved at all.
Because the universe is expanding, you can draw a boundary around us in space called the Hubble horizon. Inside that horizon, galaxies are moving away from us slower than the speed of light. Outside that horizon, galaxies are moving away from us faster than the speed of light. This doesn’t actually violate general relativity, though if you want to really understand why, I’d suggest reading Vanessa Janek’s explanation of why.
So, at this point, I’m still not sure that this new explanation really manages to clear anything up, and I’m still sort of leaning on the side of this would be nice, but it feels impossible.
I’m hopeful, though—soon we’ll have that real, peer-reviewed study, and hopefully we’ll know what’s going on. This is either an interesting dead end, something genuinely new, or, I suppose, some grand mystery. | 0.842592 | 3.528646 |
The 2019 Nobel Prize in Physics goes to three scientists who have provided deep insights into all of these questions.
James Peebles, an emeritus professor of physics at Princeton University, won half the prize for a body of work he completed since the 1960s, when he and a team of physicists at Princeton attempted to detect the remnant radiation of the dense, hot ball of gas at the beginning of the universe: the Bang Bang.
The other half went to Michel Mayor, an emeritus professor of physics from the University of Geneva, together with Didier Queloz, also a Swiss astrophysicist at the University of Geneva and the University of Cambridge. Both made breakthroughs with the discovery of the first planets orbiting other stars, also known as exoplanets, beyond our solar system.
I am an astrophysicist and was delighted to hear of this year’s Nobel recipients, who had a profound impact on scientists’ understanding of the universe. A lot of my own work on exploding stars is guided by theories describing the structure of the universe that James Peebles himself laid down.
In fact, one might say that Peebles, of all this year’s Nobel winners, is the biggest star of the real “Big Bang Theory.”
The real Big Bang Theory
As Peebles and his Princeton team rushed to complete their discovery in 1964, they were scooped by two young scientists at nearby Bell Labs, Arno Penzias and Robert Wilson. The remaining radiation from the Big Bang was predicted to be microwave energy, in much the same form used by countertop ovens.
It was a serendipitous finding because Penzias and Wilson had constructed an antenna to detect this microwave radiation which was used in satellite communications. But they were mystified by a persistent source of noise in their measurements, like the fuzz of a radio tuned between stations.
Penzias and Wilson talked to Peebles and his colleagues and learned that this static they were hearing was the radiation left over from the Big Bang itself. Penzias and Wilson won the Nobel Prize in 1978 for their discovery, though Peebles and his team provided the crucial interpretation.
Peebles has also made decades of pivotal contributions to the study of the matter which pervades the cosmos but is invisible to telescopes, known as dark matter, and the equally mysterious energy of empty space, known as dark energy. He has done foundational work on the formation of galaxies, as well as to how the Big Bang gave rise to the first elements – hydrogen, helium, lithium – on the periodic table.
Finding planets beyond our solar system
For their Nobel Prize-winning work, Mayor and Queloz carried out a survey of nearby stars using a custom-built instrument. Using this instrument, they could detect the wobble of a star – a sign that it is being tugged by the gravity of an orbiting exoplanet.
In 1995, in a landmark discovery published in the journal Nature, they found a star in the constellation Pegasus rapidly wobbling across the sky, in response to an unseen planet with half the mass of Jupiter. This exoplanet, dubbed 51 Pegasi b, orbits close to its central star, well within the orbit of Mercury in our own solar system, and completes one full orbit in just four days.
This surprising discovery of a “hot Jupiter,” quite unlike any planet in our own solar system, excited the astrophysical community and inspired many other research groups, including the Kepler space telescope team, to search for exoplanets.
These groups are using both the same wobble detection method as well as new methods, such as looking for light dips caused by exoplanets passing over nearby stars. Thanks to these research efforts, more than 4,000 exoplanets have now been discovered.
The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts. | 0.893842 | 3.911143 |
Want to look inside a deep, dark pit on Mars? Scientists and engineers using the HiRISE Camera on board NASA’s Mars Reconnaissance Orbiter have done just that.
From its orbit about 260 km (160 miles) above the surface, HiRISE can spot something as small as a dinner table, about a meter in size. But can it look inside a cave-like feature on the Red Planet and actually resolve any details inside this pit?
On October 19th, 2016, the NASA/ESA ExoMars mission arrived at the Red Planet to begin its study of the surface and atmosphere. While the Trace Gas Orbiter (TGO) successfully established orbit around Mars, the Schiaparelli Lander crashed on its way to the surface. At the time, the Mars Reconnaissance Orbiter (MRO) acquired images of the crash site using its High Resolution Imaging Science Experiment (HiRISE) camera.
In March and December of 2019, the HiRISE camera captured images of this region once again to see what the crash site looked like roughly three years later. The two images show the impact crater that resulted from the crash, which was partially-obscured by dust clouds created by the recent planet-wide dust storm. This storm lasted throughout the summer of 2019 and coincided with Spring in Mars’ northern hemisphere.
NASA’s Mars Reconnaissance Orbiter (MRO) has been in orbit around Mars for almost 14 years. It carries a variety of instruments with it, including the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument. That instrument has collected thousands of images of Mars.
We live in a time when our spacecraft orbiting Mars at an altitude of about 300 km. can snap photos of a dust devil and transmit them back to us so we can share them on the internet. Not only that, but we have rovers wandering around on the surface taking pictures of the dust storms, too. Big deal, you say? So what, you say?
When robotic missions first began to land on the surface of Mars in the 1970s, they revealed a harsh, cold and desiccated landscape. This effectively put an end generations of speculation about “Martian canals” and the possibility of life on Mars. But as our efforts to explore the Red Planet have continued, scientists have found ample evidence that the planet once had flowing water on its surface.
In addition, scientists have been encouraged by the appearance of Recurring Slope Lineae (RSL), which were believed to be signs of seasonal water flows. Unfortunately, a new study by researchers from the U.S. Geological Survey indicates that these features may be the result of dry, granular flows. These findings are another indication that the environment could be too dry for microorganisms to survive.
For the sake of their study, the team consulted data from the High Resolution Image Science Experiment (HiRISE) camera aboard the NASA Mars Reconnaissance Orbiter (MRO). This same instrument was responsible for the 2011 discovery of RSL, which were found in the middle latitudes of Mars’ southern hemisphere. These features were also observed to appear on Martian slopes during late spring through summer and then fade away in winter.
The seasonal nature of these flows was seen as a strong indication that they were the result of flowing salt-water, which was indicated by the detection of hydrated salt at the sites. However, after re-examining the HiRISE data, Dundas and his team concluded that RSLs only occur on slopes that are steep enough for dry grains to descend – in much the same way that they would on the faces of active dunes.
“We’ve thought of RSL as possible liquid water flows, but the slopes are more like what we expect for dry sand. This new understanding of RSL supports other evidence that shows that Mars today is very dry.”
Using pairs of images from HiRISE, Dundas and his colleagues constructed a series of 3-D models of slope steepness. These models incorporated 151 RSL features identified by the MRO at 10 different sites. In almost all cases, they found that the RSL were restricted to slopes that were steeper than 27° and each flow ended on a slope that matched the patterns seen in slumping dry sand dunes on Mars and Earth.
Basically, sand flows end where a steep angle gives way to a less-steep “angle of repose”, whereas liquid water flows are known to extend along less steep slopes. As Alfred McEwen, HiRISE’s Principal Investigator at the University of Arizona and a co-author of the study, indicated, “The RSL don’t flow onto shallower slopes, and the lengths of these are so closely correlated with the dynamic angle of repose, it can’t be a coincidence.”
These observations is something of a letdown, since the presence of liquid water in Mars’ equatorial region was seen as a possible indication of microbial life. However, compared to seasonal brine flows, the present of granular flows is a far better fit with what is known of Mars’ modern environment. Given that Mars’ atmosphere is very thin and cold, it was difficult to ascertain how liquid water could survive on its surface.
Nevertheless, these latest findings do not resolve all of the mystery surrounding RSLs. For example, there remains the question of how exactly these numerous flows begin and gradually grow, not to mention their seasonal appearance and the way they rapidly fade when inactive. On top of that, there is the matter of hydrated salts, which have been confirmed to contain traces of water.
To this, the authors of the study offer some possible explanations. For example, they indicate that salts can become hydrated by pulling water vapor from the atmosphere, which might explain why patches along the slopes experience changes in color. They also suggest that seasonal changes in hydration might result in some trigger mechanism for RSL grainflows, where water is absorbed and release, causing the slope to collapse.
If atmospheric water vapor is a trigger, then it raises another important question – i.e. why do RSLs appear on some slopes and not others? As Alfred McEwen – HiRISE’s Principal Investigator and a co-author on the study – explained, this could indicate that RSLs on Mars and the mechanisms behind their formation may not be entirely similar to what we see here on Earth.
“RSL probably form by some mechanism that is unique to the environment of Mars,” he said, “so they represent an opportunity to learn about how Mars behaves, which is important for future surface exploration.” Rich Zurek, the MRO Project Scientist of NASA’s Jet Propulsion Laboratory, agrees. As he explained,
“Full understanding of RSL is likely to depend upon on-site investigation of these features. While the new report suggests that RSL are not wet enough to favor microbial life, it is likely that on-site investigation of these sites will still require special procedures to guard against introducing microbes from Earth, at least until they are definitively characterized. In particular, a full explanation of how these enigmatic features darken and fade still eludes us. Remote sensing at different times of day could provide important clues.”
In the coming years, NASA plans to carry out the exploration of several sites on the Martian surface using the Mars 2020 rover, which includes a planned sample-return mission. These samples, after being collected and stored by the rover, are expected to be retrieved by a crewed mission mounted sometime in the 2030s, and then returned to Earth for analysis.
The days when we are finally able to study the Mars’ modern environment up close are fast approaching, and is expected to reveal some pretty Earth-shattering things!
During late summer in the Southern hemisphere on Mars, the angle of the sunlight as it strikes the surface brings out some subtle details on the planet’s surface.
In this image, the HiRISE camera on board NASA’s Mars Reconnaissance Orbiter (MRO) captured an area of frozen carbon dioxide on the surface. Some of the carbon dioxide ice has melted, giving it a swiss-cheese appearance. But there is also an unusual hole or crater on the right side of the image, with some of the carbon dioxide ice clearly visible in the bottom of the pit.
NASA scientists are uncertain what exactly caused the unusual pit. It could be an impact crater, or it could be a collapsed pit caused by melting or sublimation of sub-surface carbon dioxide ice.
MRO has been in orbit around Mars for over 10 years, and has completed over 50,000 orbits. The MRO has two cameras. The CTX camera is lower resolution, and has imaged over 99% of the Martian surface. HiRISE is the high-resolution camera that is used to closely examine areas and objects of interest, like the unusual surface pit in this image.
We’ve posted several ‘flyover’ videos of Mars that use data from spacecraft. But this video might be the most spectacular and realistic. Created by filmmaker Jan Fröjdman from Finland, “A Fictive Flight Above Real Mars” uses actual data from the venerable HiRISE camera on board the Mars Reconnaissance Orbiter, and takes you on a 3-D tour over steep cliffs, high buttes, amazing craters, polygons and other remarkable land forms. But Fröjdman also adds a few features reminiscent of the landing videos taken by the Apollo astronauts. Complete with crosshatches and thruster firings, this video puts you on final approach to land on (and then take off from) Mars’ surface.
(Hit ‘fullscreen’ for the best viewing)
To create the video, Fröjdman used 3-D anaglyph images from HiRISE (High Resolution Science Imaging Experiment), which contain information about the topography of Mars surface and then processed the images into panning video clips.
Fröjdman told Universe Today he worked on this video for about three months.
“The most time consuming was to manually pick the more than 33,000 reference points in the anaglyph images,” he said via email. “Now when I count how many steps there were in total in the process, I come to seven and I needed at least 6 different kinds of software.”
Fröjdman, a landscape photographer and audiovisual expert, said he wanted to create a video that gives you the feeling “that you are flying above Mars looking down watching interesting locations on the planet,” he wrote on Vimeo. “And there are really great places on Mars! I would love to see images taken by a landscape photographer on Mars, especially from the polar regions. But I’m afraid I won’t see that kind of images during my lifetime.”
Between HiRISE and the Curiosity rover images, we have the next best thing to a human on Mars. But maybe one day…
For a supposedly dead world, Mars sure provides a lot of eye candy. The High Resolution Imaging Science Experiment (HiRise) aboard NASA’s Mars Reconnaissance Orbiter (MRO) is our candy store for stunning images of Mars. Recently, HiRise gave us this stunning image (above) of colorful, layered bedrock on the surface of Mars. Notice the dunes in the center. The colors are enhanced, which makes the images more useful scientifically, but it’s still amazing.
HiRise has done it before, of course. It’s keen vision has fed us a steady stream of downright jaw-dropping images of Elon Musk’s favorite planet. Check out this image of Gale Crater taken by HiRise to celebrate its 10 year anniversary orbiting Mars. This image was captured in March 2016.
The MRO is approaching its 11 year anniversary around Mars. It has completed over 45,000 orbits and has taken over 216,000 images. The next image is of a fresh impact crater on the Martian surface that struck the planet sometime between July 2010 and May 2012. The impact was in a dusty area, and in this color-enhanced image the fresh crater looks blue because the impact removed the red dust.
These landforms on the surface of Mars are still a bit of a mystery. It’s possible that they formed in the presence of an ancient Martian ocean, or perhaps glaciers. Whatever the case, they are mesmerizing to look at.
Many images of the Martian surface have confounded scientists, and some of them still do. But some, though they look puzzling and difficult to explain, have more prosaic explanations. The image below is a large area of intersecting sand dunes.
The surface of Mars is peppered with craters, and HiRise has imaged many of them. This double crater was caused by a meteorite that split in two before hitting the surface.
The image below shows gullies and dunes at the Russell Crater. In this image, the field of dunes is about 30 km long. This image was taken during the southern winter, when the carbon dioxide is frozen. You can see the frozen CO2 as white on the shaded side of the ridges. Scientists think that the gullies are formed when the CO2 melts in the summer.
The next image is also the Russell Crater. It’s an area of study for the HiRise team, which means more Russell eye candy for us. This images shows the dunes, CO2 frost, and dust devil tracks that punctuate the area.
One of the main geological features on Mars is the Valles Marineris, the massive canyon system that dwarfs the Grand Canyon here on Earth. HiRise captured this image of delicate dune features inside Valles Marineris.
The Mars Reconnaissance Orbiter is still going strong. In fact, it continues to act as a communications relay for surface rovers. The HiRise camera is along for the ride, and if the past is any indication, it will continue to provide astounding images of Mars.
Researcher Dr. Mary Bourke from Trinity College Dublin have discovered a patch of land in an ancient valley in Mars’ Lucaya Crater that appears to have held water in the not-too-distant past, making it a prime target to search for past life forms on the Red Planet. Signs of water past and present pop up everywhere on Mars from now-dry, wriggly riverbeds snaking across arid plains to water ice exposed at the poles during the Martian summer.
On Earth, Bourke had done previous studies of dunes in the Namib Desert near Walvis Bay, Namibia and noted “arctuate striations” — crusty arcs of sand cemented by water and minerals — on the surfaces of migrating sand dunes using photos taken by satellite. She subsequently assembled a team to check them out on the ground and discovered that the striations resulted when dune materials had been chemically cemented by salts left behind by evaporating groundwater.
“On Earth, desert dune fields are periodically flooded by water in areas of fluctuating groundwater, and where lakes, rivers and coasts are found in proximity,” said Bourke. These periodic floods leave tell-tale patterns behind them.” Once the material had been cemented, it hardens and remains behind as the dunes continue to migrate downwind.
Next, Bourke and colleague Prof. Heather Viles, from the University of Oxford, examined close up images of Mars taken with the Mars Reconnaissance Orbiter (MRO) and experienced a flash of insight: “You can imagine our excitement when we scanned satellite images of an area on Mars and saw this same patterned calling card, suggesting that water had been present in the relatively recent past.”
Bourke examined similar arcuate striations exposed on the surface between dunes, indications of fluctuating levels of salty groundwater during a time when dunes were actively migrating down the valley.
So where did the water come from to create the striations in the crater valley? Bourke and Viles propose that water may have been released by the impact that formed Lucaya Crater especially if the target area was rich in ice.
Extreme temperatures during the impact would have vaporized water but also possibly melted other ice to flow for a time as liquid water. Alternatively, the impact may have jump-started hydrothermal activity as hot springs-style underground flows.
Flowing water would have created the valley and saturated the soils there with salty water. In dry periods, erosion from the wind would have picked away the water-eroded sands to create the striking pattern of repeating dunes we see to this day.
Carbonate rocks, which require liquid water to form are dissolved by the same, have been detected in the valley using spectroscopy and could have served as the cement to solidify sands between the moving dunes. That in concert with alternating dry and wet periods would create the striations seen in the MRO photos.
“These findings are hugely significant,” said Bourke. “Firstly, the Martian sand dunes show evidence that water may have been active near Mars’ equator — potentially in the not-too-distant past. And secondly, this location is now a potential geological target for detecting past life forms on the Red Planet, which is important to those involved in selecting sites for future missions.”
By day, Kevin Gill is a software engineer at the Jet Propulsion Laboratory. But on nights and weekends he takes data from spacecraft and turns them into scenes that can transport you directly to the surface of Mars.
Gill is one of many so-called “amateur” image editing enthusiasts that take real, high-resolution data from spacecraft and create views that can make you feel like you are standing on the surface of Mars, or out flying around the Solar System.
Some of the best data around for these purposes come from the HiRISE camera on board the Mars Reconnaissance Orbiter. Data known as Digital Terrain Model (DTM) files, the HiRISE DTMs are made from two or more images of the same area of a region on Mars, taken from different angles. This data isn’t just for making stunning images or amazing movies. For scientists, DTMs are very powerful research tools, used to take measurements such a elevation information and model geological processes.
So, just how do you go from this DTM image from HiRISE:
To this amazing image?
I’m going to let Kevin explain it:
To prep the data, I use Photoshop (to convert the JP2 file to a TIFF), and then standard GIS tools like gdal (Geospatial Data Abstraction Library) to create textures for 3D modeling. Using Autodesk Maya, I input those into a material as a color texture (orthoimagery) or displacement map (the DTM data).
I connect that material to a NURBS plane (sort of like a polygon mesh) that is scaled similarly to the physical properties of the data. I set up a camera at a nice angle (it takes a number of low-resolution test renders to get an angle I like) and let it render.
Then I just pull that render into Photoshop where I have a series of monochromatic color tints which gives the image it’s Martian feel. For the sky, I use either a sky from a MSL MastCam image or one that I took outside with my cell phone. If I’m using a sky I took with my cell phone, I’ll adjust the colors to make it look more like it would on Mars. If the colors in the image are still boring at this point, I may run a HDR adjustment on it in Photoshop.
What all this means is that you can create all these amazing view, plus incredible flyover videos, like this one Kevin put together of Endeavour Crater:
Or you can have some fun and visualize where the Curiosity rover is sitting:
We’ve written about this type of image editing previously, with the work of the people at UnmannedSpaceflight.com and others. Of course, the image editing software keeps improving, along with all the techniques.
Kevin also wanted to point out the work of other image editing enthusiast, Sean Doran.
“Sean’s work is resulting in views similar to mine,” Kevin said via email. “I know he’s using a process very different from mine, but we are thinking along the same lines in what we want out of the end product. His are quite impressive.”
For example, here is a flyover video of the Opportunity rover sitting along the rim of Endeavour Crater: | 0.841251 | 3.726634 |
This section contains some basic stargazing information which can be accessed by reading and scrolling, or by jumping to a particular section by clicking on the desired section listed below.
As even casual stargazers know, some stars are brighter than others. Many are so faint they are barely detectable while some are so bright they can be seen from light-polluted cities. One star in particular--our Sun--is blindingly bright. To make sense of these variations, astronomers use a measurement scale called visual magnitudes. It's a reverse scale where the brighter the object, the lower the magnitude number. In 120 BCE, long before the invention of the telescope, the Greek astronomer Hipparchus devised the first scale by which he ranked stars into six levels of brightness. (Our Sun wasn't recognized as a star then.) The brightest stars he considered "first magnitude." Those barely visible were "sixth magnitude." The rest were equally ranked in between. Although imprecise and cumbersome, his scale has been used ever since. Modern astronomers have made the scale more precise, and have expanded it to measure the full range of brightnesses, from our Sun to objects fainter than the Greeks could imagine. The scale includes fractions to account for subtle differences in brightness. For example, a star's visual magnitude might be +3.6. The scale also now dips into negative numbers for very bright objects and goes well beyond +6 for objects fainter than the naked eye can see. The difference in brightness between magnitude values is two and one-half times. For example, Virgo's Spica with a magnitude of +1 is two and one-half times brighter than Polaris (the North Star) with a magnitude of +2. The apparent brightness of stars -- how bright they appear from Earth -- depends primarily upon two factors: luminosity (their absolute brightness, i.e., the actual amount of light they give off) and distance. Our Sun, a star of average brightness, appears so bright because of its nearness. Its visual magnitude is measured at -27. By contrast, Orion's supergiant Rigel is 50,000 times brighter than our sun, but at a distance of 900 light years, its visual magnitude is 0. Even at that distance it is still the 7th brightest star in our night sky. Viewed from Rigel's distance, our Sun wouldn't even be visible to the naked eye. Polaris, the North Star, at 650 light years away, is magnitude +2. Venus, which only reflects sunlight but is much nearer than the stars, appears much brighter with a magnitude of -4. From urban areas where light pollution is a problem, the naked eye can only see objects down to 3rd magnitude or so whereas from rural areas, objects of 5th and even 6th magnitude can be seen. Thus, naked-eye urban stargazers see a few as dozens, and at most a few hundred, stars, whereas the rural stargazer can see upwards of a couple of thousand. Typical 7X50 binoculars can reveal objects down to about 8th magnitude, and even fainter under excellent viewing conditions. The Hubble Space Telescope has taken photos of incredibly faint objects at magnitude +30, which, it has been said, is comparable to seeing a candle flame several thousand miles away.
Factors Affecting Stargazing
While it takes eyes a while to dark-adapt, they un-adapt very quickly -- pupils close more quickly than they open. The headlights of a passing auto or a few seconds looking at a star map with a white flashlight is all it takes to spoil viewing for several minutes. For this reason white lights are not used or welcomed at star parties. This doesn't mean we can't use any light when stargazing. We still need to see things like star maps, planispheres, eyepieces and the like. Fortunately, the use of soft red light maintains relatively good dark adaptation. (See Red Flashlights.) If you stargaze from your yard, it's a good idea to plan ahead so you won't keep running back into your lighted house. Light pollution. Light pollution has become a serious problem for stargazing, and in most places, it is getting worse. Still it is a factor over which we can have some control. Ideally, we could do all our observing from remote locations far from civilization, but rarely is this possible. Nevertheless, unless you live in one of the mega-cities, just driving 15-25 miles into the country can make a big difference. From there, viewing is generally much better in all directions except back toward the city. Since much of the sky's action takes place in the southern half of the sky, it's good to try to find a viewing location south of your city. There are things even an urban backyard stargazer can do to improve viewing like finding a spot shielded from direct street lights, porch lights, passing cars, and the like. Also, keep in mind that views of the Moon and planets are generally much less affected by light pollution. So if your home viewing site is seriously light polluted, use it for lunar and planetary viewing and save those deep sky beauties for your excursions into the country. This is a good place to plug the International Dark-Sky Association (see Links page), an organization dedicated to combating light pollution in constructive ways. Much polluting light is wasted light shining directly into the sky rather than on the intended earthly objects. Reducing light pollution would save energy and money, as well as preserve the beauty and wonder of the night sky for future generations. Stargazers, arise against light pollution and join IDA! Moonlight. The Moon, when it is up, floods the sky with light. With anything more than a thin crescent Moon above the horizon, it is difficult to see anything more than the major planets and brightest stars. The Moon even obscures meteor showers. Having the Moon out is essentially like viewing from a heavily light polluted location. So to have some control over this factor, you'll need to understand the Moon's phases. The Moon orbits Earth every 29 1/2 days, or about every month (moonth), so each of the four phases lasts about one week. The following chart summarizes good and poor viewing times related to the Moon's phases.
During new Moon the Moon can't even be seen as it is too close to the Sun. As the Sun goes down, the Moon goes with it, leaving dark skies all night long. A few days after new Moon, the situation begins to deteriorate for evening stargazing. Each night the waxing crescent Moon grows larger and stays in the evening sky longer. In about a week, the Moon will have moved a quarter of the way around Earth, producing the 1st quarter Moon -- when the right half of the surface facing Earth is illuminated. During this phase, the Moon rises around noon, it high in the sky in the evening and sets around midnight. 1st quarter Moon, therefore, is bad for evening stargazing but good for morning viewing. After 1st quarter, the waxing gibbous Moon becomes even larger and stays in the sky longer each night. After about a week, it reach full. It is now on the opposite side of Earth from the Sun and fully illuminated -- the worst possible time for stargazing. When full, the Moon is at its largest, rises as the Sun is setting, stays in the sky all night, and doesn't set until sunrise. This might be a good time of the month to read about stargazing as you won't see much in the sky. Finally, after full Moon, the situation gets better each night for evening viewing. The waning gibbous Moon rises nearly an hour later each night and gets smaller. By 3rd quarter, the Moon is three-quarters of the way around on its monthly journey and the left half of the surface facing Earth is illuminated. It doesn't rise until around midnight -- great for evening viewing, but not for morning. Following 3rd quarter, the waning crescent Moon continues to get smaller and rise later each day until it once again aligns with the Sun in the next new Moon. A brief note: During most months, the new Moon doesn't exactly align with the Sun -- it passes slightly above or below the Sun. An exact alignment produces a solar eclipse. Another note: To avoid interfering moonlight, astronomy clubs usually hold their star parties between the 3rd quarter and new Moon. Averted Vision. One final trick employed for seeing very faint objects utilizes "averted vision." The anatomy of the human eye is such that the cones in the center of the retina are not as sensitive to faint light as the rods which surround the center. Therefore, this trick entails focusing one's eyes slightly to one side (either side will do) of the faint object while continuing to concentrate attention on the object itself. The image of the faint object then focuses on the more sensitive rods, rather than the central cones, and actually appears slightly brighter than when looked at directly.
STARGAZING AND MOON PHASES
MOON PHASE EVENING VIEWING MORNING VIEWING New good good 1st Quarter poor good Full poor poor 3rd Quarter good poor
One can practice this trick during the day. Focus on any object, then shift your attention, but not your eyes, to another object a little to one side of the first object. While still focused on the first object, notice that you can see and describe the second object without looking directly at it. You are seeing the second object with averted vision. Try it.
Sky Maps and Planispheres
Suggested Star Party Check-List
* red flashlight
* white flashlight
* planisphere/star maps
* paper and pencil
* reclining lawn chair
* cell phone
* insect repellent (seasonal)
* warm clothing (seasonal)
Star Party Etiquette
- Lights: Dark adapted eyes are important when stargazing, so use RED flashlights, not white flashlights (except in the case of an emergency, of course). Don't shine light -- even red light -- in people's eyes or face.
- Telescope viewing: Except when being used for a special project (such as astrophotography), telescopes are there for viewing so it is usually OK to move from scope to scope to look through all of them if you wish. They will probably be showing different things. Don't mob the scopes -- get in line to look through them. Try not to bump or move the scope. If you don't see anything, say so -- the object may have moved out of the FOV, the scope may have been bumped, or you might need some tips on how to look into an eyepiece.
- Asking questions and talking: It's quite OK to talk and ask questions. Just try not to get so loud others can't hear. (Loud music is NOT welcome at star parties.)
- Refreshments, etc.: It's OK to bring food and drinks (and sharing is OK, too!). Finally, it's a good idea to go the bathroom before going to a star party -- there usually are no bathrooms there.
Last updated: February 28, 2002 | 0.900259 | 3.909731 |
In a stunning scientific discovery, researchers have found water clouds inside Jupiter’s Great Red Spot, raising the prospect that life may exist on the planet.
Jupiter’s Great Red Spot, a storm that has been continuously observed since 1830, still remains a mystery to NASA and much of the scientific community, but the discovery of water clouds may lead to a greater understanding of the planet, its atmosphere and whether it ever held life, Clemson University astrophysicist Máté Ádámkovics said.
“Water may play a critical role in Jupiter’s dynamic weather patterns, so this will help advance our understanding of what makes the planet’s atmosphere so turbulent,” Ádámkovics said in a statement.
Ádámkovics was quick to caution that, while the presence of water on the solar system’s largest planet is promising, it does not mean it is a precursor for life. “And, finally, where there’s the potential for liquid water, the possibility of life cannot be completely ruled out. So, though it appears very unlikely, life on Jupiter is not beyond the range of our imaginations,” he added.
In the past, NASA has said that the planet’s “environment is probably not conducive to life as we know it,” but did add that one of its larger moons, Europa, is “one of the likeliest places to find life elsewhere in our solar system.”
The research team used the iSHELL on the NASA Infrared Telescope Facility and the Near Infrared Spectograph on the Keck 2 telescope to find the water, utilizing radiation data collected from the instruments.
The level of water on the planet is somewhat surprising, though perhaps not overly, considering the size of Jupiter. Ádámkovics noted that “Jupiter is a gas giant that contains more than twice the mass of all of our other planets combined,” so when combined with the fact its atmosphere is a mixture of hydrogen and helium, it has “many times more water than we have here on Earth.”
In addition, Jupiter has 79 moons mostly comprised of ice, including the aforementioned Europa and Ganymede, where scientists recently discovered “extraordinary” electromagnetic waves, known as “chorus waves,” emanating from the satellite.
Eventually, researchers hope to learn how much water is on the planet and what role it plays, outside of the potential for being crucial to life.
“Water may play a critical role in Jupiter’s dynamic weather patterns, so this will help advance our understanding of what makes the planet’s atmosphere so turbulent,” Ádámkovics added.
The team at Clemson used specially designed software to take the data they were being given, said undergraduate student Rachel Conway, who is involved in the university’s Creative Inquiry program.
“When I initially began, I started by running the data through. The code was already written and I was just plugging in new data sets and generating output files,” said. “But then I began fixing errors and learning more about what was actually going on. I’m interested in everything and anything that’s out there, so learning more about what we don’t know is always cool.”
In the fall, the project will move from analyzing just the Great Red Spot – large enough to contain two or three Earths – and move on to the entire planet, Ádámkovics said. | 0.818579 | 3.716396 |
Ripples in space key to understanding cosmic rays
In a new study researchers at the Swedish Institute of Space Physics have used measurements from NASA's MMS (Magnetospheric MultiScale) satellites to reveal that there are ripples, or surface waves, moving along the surface of shocks in space. Such ripples in shocks can affect how plasma is heated and are potential sites of particle acceleration. These results have been published in the latest issue of Physical Review Letters.
Most visible matter in the Universe consists of ionized gas known as plasma. Shock waves in plasmas form around planets, stars and supernovas. Shocks in space plasma are efficient particle accelerators. Shocks in supernova explosions are thought to be the main source of cosmic rays – very high energy charged particles from space.
The details on how particles are accelerated and how plasma is heated at shocks in space plasmas are still unclear. The shock waves are usually considered planar surfaces but numerical simulations have previously showed that ripples can form on the surface of shock waves. The elusive ripples have been hard to study in space due to their small size and high speed.
A new study, by researchers at the Swedish Institute of Space Physics (IRF) in Uppsala, shows that these ripples do in fact exist in the Earth's bow shock. The study uses the newly launched MMS mission to study the shock in unprecedented detail.
"With the new MMS spacecraft we can, for the first time, resolve the structure of the bow shock at these small scales," says Andreas Johlander, PhD student at IRF, who led the study.
The results are of importance to the broader field of astrophysics where these ripples are thought to play an important role in accelerating particles to very high energies. The structure of the shock wave also determine how plasma is deflected and heated at shocks.
"These direct observations of shock ripples in a space plasma allow us to characterize the physical properties of the ripples. This brings us one step closer to understanding how shocks can produce cosmic rays," says Andreas Johlander. | 0.895636 | 3.943172 |
Earlier today the names of the recipients of the prestigious international Shaw Prize were announced!Â
The 2020 Prize in Astronomy goes to the British astrophysicist Roger David Blandford “for his foundational contributions to theoretical Astrophysics, especially concerning the fundamental understanding of active galactic nuclei, the relativistic jets, the energy extraction mechanism from black holes and the acceleration of particles in shocks and their relevant radiation mechanisms”.
Our hearty congratulations to Professor Blandford!Â
The Shaw Prize
The $ 1.2 million Shaw Prize is awarded for the distinguished achievements in three disciplines: Astronomy, Mathematical Sciences and Life Science and Medicine. The Prize was established in 2002 by Sir Run Run Shaw, the legendary Hong Kong media mogul. Since Shaw’s passing away in 2014, the Prize is managed by the Shaw Foundation. Among the recipients of the Shaw Prize in Astronomy are many Nobel Prize laureates, including Kip Thorne, Rainer Weiss, Saul Perlmutter, Adam Riess, Brian Schmidt, James Peebles and Michael Mayor.
Sadly, due to the ongoing Covid-19 pandemic, this year’s award presentation ceremony will be postponed to 2021.
Roger David Blandford
Roger D Blandford is a Luke Blossom Professor in the School of Humanities and Sciences, and Professor of Physics and of Particle Physics and Astrophysics at Stanford University. Before joining Stanford in 2003, Professor Blandford worked at Caltech and Cambridge Universities. Blandford is well known for this research on black holes and gravitational lensing. He studied processes associated with Active Galactic Nuclei (AGN). AGN are supermassive black holes in the centers of galaxies. These Black Holes are actively feeding, i.e. accepting material. As a result they shine brighter than the rest of their host galaxies.
Here are just a few of Roger Blandford’s most recognized achievementsÂ
This mechanism explains how energy can be extracted from a rotating black hole. It was first proposed and described by Blandford and his colleague in the seminal 1977 paper Electromagnetic extraction of energy from Kerr black holes. Astronomers think that this is the main mechanism that drives relativistic jets, that is powerful beams of particles that dash out of the black holes at nearly the speed of light.
Roger Blandford is also a co-developer of the reverberation, or “echo” mapping technique, which is a way to probe the structure of the Active Galactic Nuclei. This method uses the fact that AGN are highly variable. The variations in the signal we see coming from the region around the supermassive black hole (accretion disc) are later echoed in the signal we observe from the neighboring region (broad line region). By looking at the delay in the “variability arrival” we can estimate the size of these regions. And, by extend, the size and mass of the black hole itself. If you want to learn more about this method, see the paper AGN Reverberation Mapping.
Prof. Blandford is an author and co-author of hundreds of scientific papers. His book “Modern Classical Physics”, written in collaboration with Kip Thorne and published in 2017, is an excellent reference textbook for physics students and researchers.
We would like to extend our congratulations to the recipients of the two other Shaw Prizes 2020,Â
- Alexander Beilinson and David Kazhdan, who will receive the Shaw Prize in Mathematical Sciences for their contribution to representation theory and other areas of Mathematics
- Gero Miesenbock, Peter Hegemann and Georg Nagel, who will receive the Shaw Prize in Life Science and Medicine for the development of Optogenics.
More about Astronomy awards
Questions? Comments? Let our star dome team know! | 0.831931 | 3.432271 |
The full moon of April, called the Pink Moon, will occur on Tuesday (April 7) at 10:35 p.m. EDT (0235 GMT on April 8), about 8 hours after reaching perigee, the nearest point from Earth in its orbit. This will create a "supermoon," a full moon that appears slightly larger than average.
The smaller distance between Earth and the full moon makes the supermoon appear about 7% larger than the average full moon and 14% larger than a full moon at apogee, or its farthest distance from Earth — also known as a "minimoon." A supermoon also appears up to 30% brighter than a full moon at apogee.
Skywatchers in the U.S. can see the "Super Pink Moon" rise into the evening sky as the sun sets on Tuesday. In New York City, for example, moonrise is at 7:05 p.m. local time on the evening of April 7, and moonset is the next morning at 7:05 a.m., according to timeanddate.com. The sun sets the evening of April 7 at 7:26 p.m.
Being in the constellation Virgo, the moon will be to the northeast of Spica, the brightest star in Virgo and the 16th-brightest star in the night sky. The moon will be in the constellation Virgo, and it have an angular diameter of 0.56 degrees, just slightly larger than its average of 0.52 degrees across, so the difference in size won't be noticeable to most people.
The moon reaches perigee, or its closest point to Earth, at 2:08 p.m. EDT (1808 GMT), according to NASA's SkyCal. The moon reaches perigee about once every 28 days, because its orbit isn't a perfect circle. However, we don't have a supermoon every month because the moon's perigee typically doesn't coincide with a full moon. During its perigee on April 7, the moon will be 221,905 miles (357,122 kilometers) from the Earth, versus an average distance of 240,000 miles (384,400 km).
When the full moon coincides with perigee, it is sometimes called a "supermoon" — but "supermoon" isn't an official term used by astronomers. Whether a full moon counts as "super" depends on how close to the official full moon the user of the word thinks perigee should be. Some astronomers define a "supermoon" as the one full moon in a calendar year that most closely coincides with the moon's perigee, while others use the term more loosely, calling any full moon that occurs within a day or so of perigee "super."
The full moon occurs when the moon is exactly on the opposite side of the Earth from the sun. Most of the time the moon is illuminated by the sun's light, but occasionally the moon's orbit carries it within the shadow of the Earth, resulting in a solar eclipse. The April full moon will "miss" the Earth's shadow, because the moon's orbit is inclined 5 degrees with respect to the plane of the Earth's orbit, and therefore the Earth won't be directly between the sun and the moon this time.
Through binoculars or a small telescope the full moon appears so bright it can be hard to see details, because there are no shadows to give any contrast. From a lunar observer's perspective the sun would be directly overhead — it would be noontime. Moon filters are available that can make some features stand out, but waiting a few days after the full moon or observing a few days before, shadows bring out more detail.
Planets on parade
On April 9, two days after the full moon, the planet Jupiter, which is prominent in the predawn sky, will be in conjunction with Pluto, meaning the two objects share the same celestial longitude and will make a close approach in the night sky.
The dwarf planet Pluto is beyond the reach of most amateur telescopes, as its visual magnitude is 15. (Magnitude is a scale astronomers use to denote an object's brightness, with smaller numbers indicating brighter objects. The dimmest objects visible with the naked eye are typically of magnitude 6.5.)
A telescope with a 10-inch (25 centimeters) aperture or more is necessary to see Pluto, and the object itself doesn't look any different from stars through the eyepiece. But Jupiter is naked-eye visible and an easy "catch" for a telescope. The conjunction occurs at 3:02 a.m. EDT (0702 GMT), according to In-The-Sky.org. Both Jupiter and Pluto will be in the constellation Sagittarius.
Other planets visible on the night of April 7-8 are Mars and Saturn, which will be close to Jupiter in the early morning hours before sunrise. As the full moon is in the west on the morning of April 8 the three planets will be in a rough line in the east-southeastern sky. By 4:30 a.m. local time in mid-northern latitudes on April 8, Mars will be about 9 degrees above the horizon, with Saturn slightly higher to the right and Jupiter to the right of that (from the point of view of an observer). For reference, your clenched first held at arm's length measures about 10 degrees wide.
The Pink Moon isn't really pink.
Despite its moniker, the Pink Moon isn't actually pink. The name "Pink Moon" comes from the bloom of ground phlox, a pink flower common in North America, according to The Old Farmer's Almanac. It has also been called the Sprouting Grass Moon, the Egg Moon and the Fish Moon.
Related: Full moon names (and more) for 2020
According to the Ontario Native Literacy Coalition, the Ojibwe peoples indigenous to North America called it the Sucker Moon after the common fish species known as suckerfish. This fish, also known as the remora, is one of the animals that the Ojibwe saw as a messenger between the spirit world and ours. In the same region, the Cree called April's full moon the Goose Moon, as April was the month when geese returned to the north after migrating south for the winter.
The Tlingit of the Pacific Northwest call the April full moon "X'eigaa Kayaaní Dís," meaning "Budding moon of plants and shrubs," according to the Tlingit Moon and Tide Teaching Resource published by the University of Alaska at Fairbanks.
In New Zealand, the Māori people had much different traditions for their April full moons, because in the Southern Hemisphere, April arrives in autumn. The Māori called the April moon "Paenga-whāwhā," describing the month as a time when "all straw is now stacked at the borders of the plantations," according to The Encyclopedia of New Zealand.
For the Jewish people, April 9 marks the beginning of the holiday of Passover (the 15th day of the lunar month of Nisan), which celebrates the escape from Egypt and has been popularized by films such as "The Ten Commandments" and Disney's "The Prince of Egypt."
Editor's note: If you have an amazing skywatching photo you'd like to share for a possible story or image gallery, you can send images and comments in to [email protected].
- Supermoon and pink sky: Full moon rises against 'Belt of Venus'
- 'Supermoon' photos: The closest full moon until 2034 in pictures
- How to photograph the supermoon: NASA pro shares his tips | 0.884954 | 3.543342 |
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Under the right conditions, Paul Doherty (physicist, rock climber, and coauthor of this column) can bicycle at near-light speed.
Incredible, you say? Being a science fiction reader, you probably know that light crosses the vacuum of space at 300 million meters or 186,000 miles per second. You probably also know that Einstein's theory of special relativity indicates that the speed of light in a vacuum is a constant--light always travels at 186,000 miles per second. (As the favorite t-shirt of one Exploratorium staffer says: "186,000 miles per second: Not just a good idea. It's the law!")
So, as a knowledgeable science fiction reader you ask a sensible question: If Paul can pedal at near-light speed, why hasn't he won every bicycle race around? Well, if you reread our first sentence, you'll note that we mentioned that our statement was true only "under the right conditions." You see, under very specific conditions, Dr. Lene Hau, a researcher at the Rowland Institute, recently managed to slow light down to a speed of 17 meters per second, which is slightly faster than Paul can bicycle on the level.
What does Einstein have to say about that? And what does all this have to do with science fiction? We'll get to that soon. First, we need to consider the nature of light, and discuss the speed of light. Then we'll tell you how Dr. Hau managed to slow light down to Paul's bicycling speed and connect all this to Bob Shaw's classic story "Light of Other Days."
Make your own electromagnetic wave
Light is tricky stuff. Back in the 1870s, the equations of Scottish physicist James Clerk Maxwell indicated that light is an electromagnetic wave. (At least, that's one way to look at light. We'll save quantum mechanics for another column. In this one, we'll just talk about light as a wave.)
Back when Maxwell was working on his wave equations, physicists figured that light traveled through aether, an undetectable substance that permeated all matter and space. Pat admits a certain fondness for the theory of aether. It seems like the physicists' equivalent of ghosts. You can't see them, but you know that they are there. Paul describes the theory this way: Physicists knew that sound waves travelled faster through stiffer material. Light was so fast that they figured the aether had to be really stiff-yet this aether which was everywhere didn't seem to exert any drag forces on planets as they moved about in their orbits.
In the nineteenth century, physicists assumed that if light traveled as a wave, it had to be a wave in something. Later experiments by Michelson and Morley contradicted the predictions of the aether theory and it was abandoned. But that still left the problem: what exactly is light a wave in?
Before we tackle that question, here's an experiment that will help you get a feel for the nature of light. All you need are four pieces of scotch magic tape about as long as your fist is wide and a table or desk. (Since some tables can be marred by having tape stuck to them, we suggest you use a battered old one, like the desks at the Exploratorium, rather than your Aunt Minnie's favorite antique.) Stick two pieces of tape to the table, side by side. Stick two more pieces on top of them. Yank both top pieces off the bottom pieces.
Bring the two pieces of tape close together, and they'll repel each other, moving apart as you try to bring them together. Even though there is nothing connecting the two pieces of tape, they exert a force on each other at a distance. Magic? Nope, it's an electric force acting over a distance.
Tape, like most things, is made up of positively charged protons and negatively charged electrons (along with some neutrons). The tape starts out electrically neutral, with equal numbers of positive and negative charges. When you pull one piece of tape off another, each piece of tape gains or loses some charged particles and gains an electrical charge. Since you peeled both pieces of tape off the same surface, they have the same charge--either positive or negative, it doesn't really matter. Since similar (or, as physicists say) like charges repel each other, one piece of tape repels the other.
You can think of the interaction between the two pieces of tape in two parts: The charge on one tape creates an electric field which in turn exerts forces on the other tape. The electric field can cross empty space.
What does all this have to do with light? Well, when you wiggle one piece of tape, you're changing the electric field in the space surrounding that tape. The side-to-side changes in the electric field propagate from one tape to the other as a wave travelling at the speed of light. A wave in an electric field creates an accompanying wave in a magnetic field. The combination of changing electric and magnetic fields is called an electromagnetic wave. When you wiggle the tape, you make a wave that travels to the other tape and makes it wiggle. The electromagnetic wave you are creating by wiggling your tapes is an ELF. (No, not that kind of elf. This is a science column, after all.) ELF stands for Extremely Low Frequency radio wave.
Light is also an electromagnetic wave. To understand light, you need to remember that it starts with a moving electric charge. When you squint because sunlight gets in your eyes, you are responding to an electromagnetic wave that was created when an electric charge in the surface of the sun accelerated That wave travelled 93 million miles across the vacuum of space to reach your eye 8.3 minutes later. The light made electrons in chemicals that are in the rods and cones in your eye's retina wiggle--and that made you see light.
The electromagnetic wave that you make by moving your charged tape also has to travel. It may seem to you like the second tape moves the instant you move the first one, but there is a time delay. Since the wave propagates at the speed of light, it's a mighty short delay. The speed of light is one foot per nanosecond, so if the tapes were a foot apart, the delay would be a nanosecond, a billionth of a second.
The speed of light in a vacuum was first measured by Ole Roemer in 1676. While studying eclipses of the moons of Jupiter, Roemer noticed that the eclipses were seen 8 minutes earlier than average when the earth was on the side of its orbit nearest Jupiter. When the earth was on the far side of its orbit, eclipses were 8 minutes later than average. This disparity could be explained by assuming that light took 16 minutes to cross the diameter of the earth's orbit. Knowing the diameter of the earth's orbit gave Roemer the speed of light: in modern units, 300 million meters per second or 186,000 miles per second.
Slowing Light Down
That's how fast light travels in a vacuum. But what happens when light shines through something clear, like water or glass? In 1862 Jean Foucault measured the speed of light in glass and found out that it was slower than in vacuum. Light travels about 2/3 as fast through glass as it does through a vacuum.
When a light beam passes from one medium into another (from air into glass or glass into air) and slows down, it also bends. Light of different frequencies bends by different amounts, which is why prisms and raindrops separate white light into its component frequencies or colors. We're not going to dwell on the colorful aspects of bending light. For that, check out our column "Watch the Skies" back in December 1997. If you don't believe that light actually bends at a boundary, check out the experiment on page 00. Here, we're going to talk about why light slows down, rather than why it bends.
Here is a model of how light slows in a material. Step back to 1900 when Maxwell's equations were the last word on what light was, and when physicists knew that atoms contained electrons. Maxwell pictured light as a wave and he knew what light was a wave in. It was a wave in the electric field. (It is also a wave in the magnetic field but we can ignore that here.)
Electric fields exert forces on electric charges. So when an electric field wave passes by an atom, it exerts forces on the electrons in each atom. Now the electrons in glass are bound to their atoms. Yet they accelerate up and down under the electric forces from the passing light. Because they are bound to their atoms, these electrons lag a bit behind the electric field wave's ups and downs.
The moving electrons remove some energy from the light. The oscillating electrons then re-emit the light. But the re-emission is slightly delayed. After the light has gone far enough into the glass, almost all of the energy of the original light had been absorbed and re-emitted many times. The net effect of these continuous delays is the slowing of the light wave as it moves through the material.
Each atom has its own characteristic delay time. Light travels at a different speed through air, through different kinds of glass, through water. In between the atoms of all these materials, light travels at the same speed that it travels through a vacuum. But all those delays mean that its net travel time is longer.
Slowing Light Way Down
To slow light down to the speed of a bicycling physicist, Dr. Lene Hau worked with light of a specific frequency. Drive around almost any big city at night and you will see yellow street lights. These are sodium lights, in which electrically excited sodium metal vapor emits light in the yellow part of the spectrum.
The sodium atoms have a strong interaction for a narrow range of yellow light frequencies. If you shine yellow light into sodium vapor, the sodium atoms absorb the light. (They re-emit the light in another direction so it doesn't reach you.) So sodium vapor is opaque to yellow light.
Dr. Hau experimented with this. When she shone a yellow laser light at the sodium atoms, they absorbed that wavelength almost as well as a block of lead would have. However, Dr. Hau then shone another wavelength of laser light onto the sodium. This second laser beam made it so that the sodium could not absorb the original beam of yellow light, via a process known as laser-induced transparency. But the sodium atoms still interacted strongly with the yellow light, slowing it down without actually absorbing it! (In her experiment about 1/3 of the yellow photons made it through the sodium cloud.)
Dr. Hau then proceeded to cool the sodium atoms down to one of the coldest temperatures ever achieved in a laboratory anywhere- 50 nanokelvins, just 50 billionths of a degree above absolute zero! As the atoms cooled they slowed down.
All atoms obey Heisenberg's uncertainty principle. As the atoms slowed, their momentum became closer and closer to zero with less and less uncertainty. Heisenberg assures us that this means that their location in space then must become uncertain. The location became so uncertain that the sodium atoms began to overlap. All of the sodium atoms began to behave like one quantum mechanically coupled object. When changing their quantum state by absorbing energy, they all had to change their quantum state together. This quantum coupled system is known as a Bose-Einstein Condensate, or BEC, after Bose and Einstein who predicted it in 1924. (Okay--we are talking about quantum mechanics, but we aren't treating light quantum mechanically here; we're treating atoms. If you want to know more about BECs, we suggest you check out http://www.colorado.edu/physics/2000/bec/index.html.)
It was in this BEC of sodium atoms that Lene Hau managed to slow light. She fired in a pulse of light and timed how long it took to cross the cigar shaped region of the BEC. Using the first equation Paul ever learned in fourth grade-velocity equals distance divided by time-she calculated the speed of light through the condensate and found it to be slowed to 17 m/s.
The Science Fiction Connection
Lene Hau succeeded in slowing the speed of light to 17 meters per second. in 1998. As usual, a science fiction author was way ahead of the scientists.
Back in 1966, Bob Shaw was nominated for the Nebula Award for a short story titled "Light of Other Days." This story, like most good science fiction, uses a technological development to get at some basic emotional truths. The technological development is "slow glass," a material that slows light down. Light shining into a piece of slow glass that's 6 millimeters thick comes out the other side ten years later. A piece of slow glass in a window frame lets city dwellers replace their view of a dingy city with a beautiful natural scene that changes with the seasons. A troubled couple, considering the purchase of a pane of slow glass, discovers some things about love and loss and what really matters.
After reading Bob Shaw's short story, Paul immediately wanted to "do the numbers." Rounding off to show that he is indeed a physicist and not a mathematician, Paul found that the light in the slow glass traveled about 1/2 a millimeter a year. That means that the light travels about 5 x 10-4 m in 3 x 107 s or about 2 x 10-11 m/s. That's about one atomic diameter in 5 seconds! That's slow!
One difference between Bob Shaw's slow glass and Lene Hau's sodium BEC is that Bob Shaw's works across the entire visible spectrum and so recreates scenes in full color, while Dr. Hau's works only at one precise frequency. Other wavelengths or frequencies of light speed through the sodium at nearly the speed of light in a vacuum.
Dr. Hau hopes to be able to improve her result soon slowing light even more to a few centimeters per second. But she still has a long way to go to catch up to the vision of Bob Shaw.
Note: For more about Pat Murphy's and Paul Doherty's work, check out their web sites at: www.brazenhussies.net/murphy and www.exo.net/~pauld.
Water slows light down--and can bend it in the process.
You'll need: a penny, a shallow bowl, a pitcher of water, and a helper.
Put the penny in the bowl. Close one eye and stoop down or step back until the rim of the bowl just blocks your view of the penny.
Have your helper pour water into the bowl. Ask him or her to pour the water slowly so that the penny doesn't move. When the water is deep enough, the penny will reappear.
You see the penny because light bouncing off the coin gets into your eye and makes an image. The water bends the light that's reflecting from the penny so that it gets over the rim of the bowl into your eyes.
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Copyright © 1998–2020 Fantasy & Science Fiction All Rights Reserved Worldwide | 0.801413 | 3.079795 |
X-ray detection sheds light on Pluto
Scientists using NASA’s Chandra X-ray Observatory have made the first detections of X-rays from Pluto. These observations offer new insight into the space environment surrounding the largest and best-known object in the solar system’s outermost regions.
While NASA’s New Horizons spacecraft was speeding toward and beyond Pluto, Chandra was aimed several times on the dwarf planet and its moons, gathering data on Pluto that the missions could compare after the flyby. Each time Chandra pointed at Pluto – four times in all, from February 2014 through August 2015 – it detected low-energy X-rays from the small planet.
Pluto is the largest object in the Kuiper Belt, a ring or belt containing a vast population of small bodies orbiting the Sun beyond Neptune. The Kuiper belt extends from the orbit of Neptune, at 30 times the distance of Earth from the Sun, to about 50 times the Earth-Sun distance. Pluto’s orbit ranges over the same span as the overall Kupier Belt.
"We've just detected, for the first time, X-rays coming from an object in our Kuiper Belt, and learned that Pluto is interacting with the solar wind in an unexpected and energetic fashion,” said Carey Lisse, an astrophysicist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, who led the Chandra observation team with APL colleague and New Horizons Co-Investigator Ralph McNutt. “We can expect other large Kuiper Belt objects to be doing the same."
The team recently published its findings online in the journal Icarus. The report details what Lisse says was a somewhat surprising detection given that Pluto – being cold, rocky and without a magnetic field – has no natural mechanism for emitting X-rays.
But Lisse, having also led the team that made the first X-ray detections from a comet two decades ago, knew the interaction between the gases surrounding such planetary bodies and the solar wind – the constant streams of charged particles from the sun that speed throughout the solar system – can create X-rays.
New Horizons scientists were particularly interested in learning more about the interaction between the gases in Pluto’s atmosphere and the solar wind. The spacecraft itself carries an instrument designed to measure that activity up-close – the aptly named Solar Wind Around Pluto (SWAP) – and scientists are using that data to craft a picture of Pluto that contains a very mild, close-in bowshock, where the solar wind first “meets” Pluto (similar to a shock wave that forms ahead of a supersonic aircraft) and a small wake or tail behind the planet.
The immediate mystery is that Chandra’s readings on the brightness of the X-rays are much higher than expected from the solar wind interacting with Pluto’s atmosphere.
“Before our observations, scientists thought it was highly unlikely that we’d detect X-rays from Pluto, causing a strong debate as to whether Chandra should observe it at all,” said co-author Scott Wolk, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
“Prior to Pluto, the most distant solar system body with detected X-ray emission was Saturn's rings and disk."
The Chandra detection is especially surprising since New Horizons discovered Pluto’s atmosphere was much more stable than the rapidly escaping, “comet-like” atmosphere that many scientists expected before the spacecraft flew past in July 2015.
In fact, New Horizons found that Pluto’s interaction with the solar wind is much more like the interaction of the solar wind with Mars, than with a comet. However, although Pluto is releasing enough gas from its atmosphere to make the observed X-rays, in simple models for the intensity of the solar wind at the distance of Pluto, there isn't enough solar wind flowing directly at Pluto to make them.
Lisse and his colleagues – who also include SWAP co-investigators David McComas from Princeton University and Heather Elliott from Southwest Research Institute – suggest several possibilities for the enhanced X-ray emission from Pluto.
These include a much wider and longer tail of gases trailing Pluto than New Horizons detected using its SWAP instrument. Other possibilities are that interplanetary magnetic fields are focusing more particles than expected from the solar wind into the region around Pluto, or the low density of the solar wind in the outer solar system at the distance of Pluto could allow for the formation of a doughnut, or torus, of neutral gas centered around Pluto's orbit.
That the Chandra measurements don’t quite match up with New Horizons up-close observations is the benefit – and beauty – of an opportunity like the New Horizons flyby. “When you have a chance at a once in a lifetime flyby like New Horizons at Pluto, you want to point every piece of glass – every telescope on and around Earth – at the target,” McNutt says. “The measurements come together and give you a much more complete picture you couldn’t get at any other time, from anywhere else.”
New Horizons has an opportunity to test these findings and shed even more light on this distant region – billions of miles from Earth – as part of its recently approved extended mission to survey the Kuiper Belt and encounter another smaller Kuiper Belt object, 2014 MU69, on Jan. 1, 2019.
It is unlikely to be feasible to detect X-rays from MU69, but Chandra might detect X-rays from other larger and closer objects that New Horizons will observe as it flies through the Kuiper Belt towards MU69.
The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft and manages the mission for NASA’s Science Mission Directorate. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate.
The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. | 0.861773 | 3.987275 |
The universe doesn't do medium. In terms of what turns heads, you're either very, very big (think galactic clusters) or very, very small (think neutrinos and bosons). That's long been assumed to be the rule for black holes too. For 30 years, astronomers have been looking for evidence of a theorized class of black hole that would be sort of a cosmic middle child, falling somewhere between the well-established smaller ones which are "only" 30 times the mass of our sun and the supermassive types that are the equivalent of millions of solar masses.
There's more than just a taste for cosmic tidiness behind the hunt. These so-called intermediate-mass black holes could provide an important link in the life cycle of all black holes, suggesting that the mini and jumbo models are not two completely different species but rather members of a single species at different stages of maturation. Now there is evidence that medium-size black holes might indeed exist courtesy of an X-ray blast from a mysterious body 290 million light-years from Earth.
It was three years ago that astrophysicists discovered the object they straightforwardly dubbed Hyper-Luminous X-ray source-1 (HLX-1), so named because it emits 260 million times the X-ray brightness of our sun. But the nature of the object was a head scratcher mostly because it was invisible. It couldn't be a foreground star or a background galaxy. That meant it was probably though not definitely a black hole, since the gasses and other material being pulled into the body would produce X-rays as a byproduct. The intensity of the emissions put the black hole's size at 500 times the sun's mass, which would place it in the long-sought intermediate range.
But while potent X-rays are characteristic of black holes, they're only half of a two-part signature. In the vicinity of other black holes, astronomers witness a violent reaction to so much incoming gas: the region belches plasma jets, visible from Earth in the form of radio-wave emissions that erupt a few hours or days afterward. Now, in a paper published in the July 6 issue of Science, Natalie Webb of the Université de Toulouse in France has announced that she and her research team have detected those radio emissions at HLX-1 too, strongly suggesting that the object is indeed a not-too-big, not-too-small black hole.
"When my group initially found HLX-1 in 2009 using a simple approach, I was extremely skeptical," Webb says. "However, we have observed it in all different wavelengths, and so far it is the first intermediate-mass black-hole candidate that has stood up to so many tests."
The most elegant part of the new study is how the researchers used the mere presence of the plasma jets to calculate the black hole's size far more precisely than with the X-rays alone. X-ray intensity correlates to the amount of matter falling into the hole, while radio emissions correlate to the strength of the exiting jets and both appear to have a constant, scaled relationship to the mass of a black hole. If you know that constant and it's a pretty standard equation in the astrophysicist's toolbox you can calculate the mass of the body. While the X-ray readings put the black hole at the very low end of the medium range, the plasma jets boosted it higher from just 500 solar masses to somewhere between 9,000 and 90,000. That's a big range, but for a first discovery, it's not too shabby. Indeed, says Webb, her calculations represent "the most refined estimate of the mass of HLX-1 and indeed any intermediate-mass black hole proposed to date."
The existence of a body in this mass range opens the door to new theories about just what it is that determines a black hole's size. Though all black holes grow by feeding off nearby matter, the source of that matter varies. Small, stellar black holes form as the result of the supernova collapse of a single star. Intermediate black holes may form inside older, glistening star swarms known as globular star clusters. The supermassive varieties are located in the high-density, high-velocity center of galaxies.
No matter the size, there is a mathematical constant at work here too: studies suggest that black holes usually represent about 0.5% of the mass of the galaxy or stellar environment they inhabit, regardless of size. It's possible that a small black hole swells to middleweight size as it both collides with and consumes other objects within the confines of a globular cluster. Supermassive black holes could later form through mergers of several intermediate black holes. "Confirming that HLX-1 is an intermediate-mass black hole helps to substantiate the argument that supermassive black holes are formed from intermediate-mass black holes," Webb says. "Without observational proof of their existence, the theory was only speculative."
Though HLX-1 is getting all the attention at the moment, researchers are investigating other potential medium-size black holes, including objects within globular clusters in the constellation Pegasus and the Andromeda galaxy. Astrophysicists are also focusing on low-mass "dwarf galaxies" that have had very little interaction with other galaxies, hoping to find intermediate-mass black holes hidden somewhere inside like treats in a cereal box.
In the meantime, studies of HLX-1 will continue. "I am very excited that we have finally found the observational evidence to substantiate these theoretically proposed objects," Webb says. It seems HLX-1 is one middle child that will not be neglected. | 0.88615 | 4.035955 |
Boron is a chemical element with the symbol B and atomic number 5. Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in the Solar system and in the Earth’s crust. Boron is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals. These are mined industrially as evaporites, such as borax and kernite. The largest known boron deposits are in Turkey, the largest producer of boron minerals.
Elemental boron is a metalloid that is found in small amounts in meteoroids but chemically uncombined boron is not otherwise found naturally on Earth. Industrially, very pure boron is produced with difficulty because of refractory contamination by carbon or other elements. Several allotropes of boron exist: amorphous boron is a brown powder; crystalline boron is silvery to black, extremely hard (about 9.5 on the Mohs scale), and a poor electrical conductor at room temperature. The primary use of elemental boron is as boron filaments with applications similar to carbon fibers in some high-strength materials.
Boron is primarily used in chemical compounds. About half of all boron consumed globally is an additive in fiberglass for insulation and structural materials. The next leading use is in polymers and ceramics in high-strength, lightweight structural and refractory materials. Borosilicate glass is desired for its greater strength and thermal shock resistance than ordinary soda lime glass. Boron as sodium perborate is used as a bleach. A small amount of boron is used as a dopant in semiconductors, and reagent intermediates in the synthesis of organic fine chemicals. A few boron-containing organic pharmaceuticals are used or are in study. Natural boron is composed of two stable isotopes, one of which (boron-10) has a number of uses as a neutron-capturing agent.
In biology, borates have low toxicity in mammals (similar to table salt), but are more toxic to arthropods and are used as insecticides. Boric acid is mildly antimicrobial, and several natural boron-containing organic antibiotics are known. Boron is an essential plant nutrient and boron compounds such as borax and boric acid are used as fertilizers in agriculture, although it’s only required in small amounts, with excess being toxic. Boron compounds play a strengthening role in the cell walls of all plants. There is no consensus on whether boron is an essential nutrient for mammals, including humans, although there is some evidence it supports bone health.
The word boron was coined from borax, the mineral from which it was isolated, by analogy with carbon, which boron resembles chemically.
Borax, its mineral form then known as tincal, glazes were used in China from AD 300, and some crude borax reached the West, where the Perso-Arab alchemist Jābir ibn Hayyān apparently mentioned it in AD 700. Marco Polo brought some glazes back to Italy in the 13th century. Agricola, around 1600, reports the use of borax as a flux in metallurgy. In 1777, boric acid was recognized in the hot springs (soffioni) near Florence, Italy, and became known as sal sedativum, with primarily medical uses. The rare mineral is called sassolite, which is found at Sasso, Italy. Sasso was the main source of European borax from 1827 to 1872, when American sources replaced it. Boron compounds were relatively rarely used until the late 1800s when Francis Marion Smith’s Pacific Coast Borax Company first popularized and produced them in volume at low cost.
Boron was not recognized as an element until it was isolated by Sir Humphry Davy and by Joseph Louis Gay-Lussac and Louis Jacques Thénard. In 1808 Davy observed that electric current sent through a solution of borates produced a brown precipitate on one of the electrodes. In his subsequent experiments, he used potassium to reduce boric acid instead of electrolysis. He produced enough boron to confirm a new element and named the element boracium. Gay-Lussac and Thénard used iron to reduce boric acid at high temperatures. By oxidizing boron with air, they showed that boric acid is an oxidation product of boron. Jöns Jacob Berzelius identified boron as an element in 1824. Pure boron was arguably first produced by the American chemist Ezekiel Weintraub in 1909.
Boron is rare in the Universe and solar system due to trace formation in the Big Bang and in stars. It is formed in minor amounts in cosmic ray spallation nucleosynthesis and may be found uncombined in cosmic dust and meteoroid materials.
In the high oxygen environment of Earth, boron is always found fully oxidized to borate. Boron does not appear on Earth in elemental form. Extremely small traces of elemental boron were detected in Lunar regolith.
Although boron is a relatively rare element in the Earth’s crust, representing only 0.001% of the crust mass, it can be highly concentrated by the action of water, in which many borates are soluble. It is found naturally combined in compounds such as borax and boric acid (sometimes found in volcanic spring waters). About a hundred borate minerals are known.
On September 5, 2017, scientists reported that the Curiosity rover detected boron, an essential ingredient for life on Earth, on the planet Mars. Such a finding, along with previous discoveries that water may have been present on ancient Mars, further supports the possible early habitability of Gale Crater on Mars.
Economically important sources of boron are the minerals colemanite, rasorite (kernite), ulexite and tincal. Together these constitute 90% of mined boron-containing ore. The largest global borax deposits known, many still untapped, are in Central and Western Turkey, including the provinces of Eskişehir, Kütahya and Balıkesir. Global proven boron mineral mining reserves exceed one billion metric tonnes, against a yearly production of about four million tonnes.
Turkey and the United States are the largest producers of boron products. Turkey produces about half of the global yearly demand, through Eti Mine Works (Turkish: Eti Maden İşletmeleri) a Turkish state-owned mining and chemicals company focusing on boron products. It holds a government monopoly on the mining of borate minerals in Turkey, which possesses 72% of the world’s known deposits. In 2012, it held a 47% share of production of global borate minerals, ahead of its main competitor, Rio Tinto Group.
Almost a quarter (23%) of global boron production comes from the single Rio Tinto Borax Mine (also known as the U.S. Borax Boron Mine) 35°2′34.447″N 117°40′45.412″W near Boron, California.
The average cost of crystalline boron is $5/g. Free boron is chiefly used in making boron fibers, where it is deposited by chemical vapor deposition on a tungsten core (see below). Boron fibers are used in lightweight composite applications, such as high strength tapes. This use is a very small fraction of total boron use. Boron is introduced into semiconductors as boron compounds, by ion implantation.
Estimated global consumption of boron (almost entirely as boron compounds) was about 4 million tonnes of B2O3 in 2012. Boron mining and refining capacities are considered to be adequate to meet expected levels of growth through the next decade.
The form in which boron is consumed has changed in recent years. The use of ores like colemanite has declined following concerns over arsenic content. Consumers have moved toward the use of refined borates and boric acid that have a lower pollutant content.
Increasing demand for boric acid has led a number of producers to invest in additional capacity. Turkey’s state-owned Eti Mine Works opened a new boric acid plant with the production capacity of 100,000 tonnes per year at Emet in 2003. Rio Tinto Group increased the capacity of its boron plant from 260,000 tonnes per year in 2003 to 310,000 tonnes per year by May 2005, with plans to grow this to 366,000 tonnes per year in 2006. Chinese boron producers have been unable to meet rapidly growing demand for high quality borates. This has led to imports of sodium tetraborate (borax) growing by a hundredfold between 2000 and 2005 and boric acid imports increasing by 28% per year over the same period.
The rise in global demand has been driven by high growth rates in glass fiber, fiberglass and borosilicate glassware production. A rapid increase in the manufacture of reinforcement-grade boron-containing fiberglass in Asia, has offset the development of boron-free reinforcement-grade fiberglass in Europe and the US. The recent rises in energy prices may lead to greater use of insulation-grade fiberglass, with consequent growth in the boron consumption. Roskill Consulting Group forecasts that world demand for boron will grow by 3.4% per year to reach 21 million tonnes by 2010. The highest growth in demand is expected to be in Asia where demand could rise by an average 5.7% per year.
Nearly all boron ore extracted from the Earth is destined for refinement into boric acid and sodium tetraborate pentahydrate. In the United States, 70% of the boron is used for the production of glass and ceramics. The major global industrial-scale use of boron compounds (about 46% of end-use) is in production of glass fiber for boron-containing insulating and structural fiberglasses, especially in Asia. Boron is added to the glass as borax pentahydrate or boron oxide, to influence the strength or fluxing qualities of the glass fibers. Another 10% of global boron production is for borosilicate glass as used in high strength glassware. About 15% of global boron is used in boron ceramics, including super-hard materials discussed below. Agriculture consumes 11% of global boron production, and bleaches and detergents about 6%.
Elemental boron fiber
Boron fibers (boron filaments) are high-strength, lightweight materials that are used chiefly for advanced aerospace structures as a component of composite materials, as well as limited production consumer and sporting goods such as golf clubs and fishing rods. The fibers can be produced by chemical vapor deposition of boron on a tungsten filament.
Boron fibers and sub-millimeter sized crystalline boron springs are produced by laser-assisted chemical vapor deposition. Translation of the focused laser beam allows production of even complex helical structures. Such structures show good mechanical properties (elastic modulus 450 GPa, fracture strain 3.7%, fracture stress 17 GPa) and can be applied as reinforcement of ceramics or in micromechanical systems.
Fiberglass is a fiber reinforced polymer made of plastic reinforced by glass fibers, commonly woven into a mat. The glass fibers used in the material are made of various types of glass depending upon the fiberglass use. These glasses all contain silica or silicate, with varying amounts of oxides of calcium, magnesium, and sometimes boron. The boron is present as borosilicate, borax, or boron oxide, and is added to increase the strength of the glass, or as a fluxing agent to decrease the melting temperature of silica, which is too high to be easily worked in its pure form to make glass fibers.
The highly boronated glasses used in fiberglass are E-glass (named for “Electrical” use, but now the most common fiberglass for general use). E-glass is alumino-borosilicate glass with less than 1% w/w alkali oxides, mainly used for glass-reinforced plastics. Other common high-boron glasses include C-glass, an alkali-lime glass with high boron oxide content, used for glass staple fibers and insulation, and D-glass, a borosilicate glass, named for its low Dielectric constant).
Not all fiberglasses contain boron, but on a global scale, most of the fiberglass used does contain it. Because the ubiquitous use of fiberglass in construction and insulation, boron-containing fiberglasses consume half the global production of boron, and are the single largest commercial boron market.
Borosilicate glass, which is typically 12–15% B2O3, 80% SiO2, and 2% Al2O3, has a low coefficient of thermal expansion, giving it a good resistance to thermal shock. Schott AG’s “Duran” and Owens-Corning’s trademarked Pyrex are two major brand names for this glass, used both in laboratory glassware and in consumer cookware and bakeware, chiefly for this resistance. Boron carbide ceramic
Several boron compounds are known for their extreme hardness and toughness. Boron carbide is a ceramic material which is obtained by decomposing B2O3 with carbon in an electric furnace:
2 B2O3 + 7 C → B4C + 6 CO
Boron carbide’s structure is only approximately B4C, and it shows a clear depletion of carbon from this suggested stoichiometric ratio. This is due to its very complex structure. The substance can be seen with empirical formula B12C3 (i.e., with B12 dodecahedra being a motif), but with less carbon, as the suggested C3 units are replaced with C-B-C chains, and some smaller (B6) octahedra are present as well (see the boron carbide article for structural analysis). The repeating polymer plus semi-crystalline structure of boron carbide gives it great structural strength per weight. It is used in tank armor, bulletproof vests, and numerous other structural applications.
Boron carbide’s ability to absorb neutrons without forming long-lived radionuclides (especially when doped with extra boron-10) makes the material attractive as an absorbent for neutron radiation arising in nuclear power plants. Nuclear applications of boron carbide include shielding, control rods and shut-down pellets. Within control rods, boron carbide is often powdered, to increase its surface area.
Boron is added to boron steels at the level of a few parts per million to increase hardenability. Higher percentages are added to steels used in the nuclear industry due to boron’s neutron absorption ability.
Boron can also increase the surface hardness of steels and alloys through boriding. Additionally metal borides are used for coating tools through chemical vapor deposition or physical vapor deposition. Implantation of boron ions into metals and alloys, through ion implantation or ion beam deposition, results in a spectacular increase in surface resistance and microhardness. Laser alloying has also been successfully used for the same purpose. These borides are an alternative to diamond coated tools, and their (treated) surfaces have similar properties to those of the bulk boride.
For example, rhenium diboride can be produced at ambient pressures, but is rather expensive because of rhenium. The hardness of ReB2 exhibits considerable anisotropy because of its hexagonal layered structure. Its value is comparable to that of tungsten carbide, silicon carbide, titanium diboride or zirconium diboride. Similarly, AlMgB14 + TiB2 composites possess high hardness and wear resistance and are used in either bulk form or as coatings for components exposed to high temperatures and wear loads.
Detergent formulations and bleaching agents
Borax is used in various household laundry and cleaning products, including the “20 Mule Team Borax” laundry booster and “Boraxo” powdered hand soap. It is also present in some tooth bleaching formulas.
Sodium perborate serves as a source of active oxygen in many detergents, laundry detergents, cleaning products, and laundry bleaches. However, despite its name, “Borateem” laundry bleach no longer contains any boron compounds, using sodium percarbonate instead as a bleaching agent. Insecticides
Boric acid is used as an insecticide, notably against ants, fleas, and cockroaches.
Boron is a useful dopant for such semiconductors as silicon, germanium, and silicon carbide. Having one fewer valence electron than the host atom, it donates a hole resulting in p-type conductivity. Traditional method of introducing boron into semiconductors is via its atomic diffusion at high temperatures. This process uses either solid (B2O3), liquid (BBr3), or gaseous boron sources (B2H6 or BF3). However, after the 1970s, it was mostly replaced by ion implantation, which relies mostly on BF3 as a boron source. Boron trichloride gas is also an important chemical in semiconductor industry, however not for doping but rather for plasma etching of metals and their oxides. Triethylborane is also injected into vapor deposition reactors as a boron source. Examples are the plasma deposition of boron-containing hard carbon films, silicon nitride-boron nitride films, and for doping of diamond film with boron.
Boron is a component of neodymium magnets (Nd2Fe14B), which are among the strongest type of permanent magnet. These magnets are found in a variety of electromechanical and electronic devices, such as magnetic resonance imaging (MRI) medical imaging systems, in compact and relatively small motors and actuators. As examples, computer HDDs (hard disk drives), CD (compact disk) and DVD (digital versatile disk) players rely on neodymium magnet motors to deliver intense rotary power in a remarkably compact package. In mobile phones ‘Neo’ magnets provide the magnetic field which allows tiny speakers to deliver appreciable audio power. Shielding and neutron absorber in nuclear reactors
Boron shielding is used as a control for nuclear reactors, taking advantage of its high cross-section for neutron capture.
In pressurized water reactors a variable concentration of boronic acid in the cooling water is used as a neutron poison to compensate the variable reactivity of the fuel. When new rods are inserted the concentration of boronic acid is maximal, and is reduced during the lifetime.
Other nonmedical uses
- Because of its distinctive green flame, amorphous boron is used in pyrotechnic flares.
- Starch and casein-based adhesives contain sodium tetraborate decahydrate (Na2B4O7·10 H2O)
- Some anti-corrosion systems contain borax.
- Sodium borates are used as a flux for soldering silver and gold and with ammonium chloride for welding ferrous metals. They are also fire retarding additives to plastics and rubber articles.
- Boric acid (also known as orthoboric acid) H3BO3 is used in the production of textile fiberglass and flat panel displays and in many PVAc- and PVOH-based adhesives.
- Triethylborane is a substance which ignites the JP-7 fuel of the Pratt & Whitney J58 turbojet/ramjet engines powering the Lockheed SR-71 Blackbird. It was also used to ignite the F-1 Engines on the Saturn V Rocket utilized by NASA’s Apollo and Skylab programs from 1967 until 1973. Today SpaceX uses it to ignite the engines on their Falcon 9 rocket. Triethylborane is suitable for this because of its pyrophoric properties, especially the fact that it burns with a very high temperature. Triethylborane is an industrial initiator in radical reactions, where it is effective even at low temperatures.
- Borates are used as environmentally benign wood preservatives.
Pharmaceutical and biological applications
Boric acid has antiseptic, antifungal, and antiviral properties and for these reasons is applied as a water clarifier in swimming pool water treatment. Mild solutions of boric acid have been used as eye antiseptics.
Bortezomib (marketed as Velcade and Cytomib). Boron appears as an active element in its first-approved organic pharmaceutical in the pharmaceutical bortezomib, a new class of drug called the proteasome inhibitors, which are active in myeloma and one form of lymphoma (it is in currently in experimental trials against other types of lymphoma). The boron atom in bortezomib binds the catalytic site of the 26S proteasome with high affinity and specificity.
- A number of potential boronated pharmaceuticals using boron-10, have been prepared for use in boron neutron capture therapy (BNCT).
- Some boron compounds show promise in treating arthritis, though none have as yet been generally approved for the purpose.
Tavaborole (marketed as Kerydin) is an Aminoacyl tRNA synthetase inhibitor which is used to treat toenail fungus. It gained FDA approval in July 2014.
Dioxaborolane chemistry enables radioactive fluoride (18F) labeling of antibodies or red blood cells, which allows for positron emission tomography (PET) imaging of cancer and hemorrhages, respectively. A Human-Derived, Genetic, Positron-emitting and Fluorescent (HD-GPF) reporter system uses a human protein, PSMA and non-immunogenic, and a small molecule that is positron-emitting (boron bound 18F) and fluorescent for dual modality PET and fluorescence imaging of genome modified cells, e.g. cancer, CRISPR/Cas9, or CAR T-cells, in an entire mouse.
Boron is an essential plant nutrient, required primarily for maintaining the integrity of cell walls. However, high soil concentrations of greater than 1.0 ppm lead to marginal and tip necrosis in leaves as well as poor overall growth performance. Levels as low as 0.8 ppm produce these same symptoms in plants that are particularly sensitive to boron in the soil. Nearly all plants, even those somewhat tolerant of soil boron, will show at least some symptoms of boron toxicity when soil boron content is greater than 1.8 ppm. When this content exceeds 2.0 ppm, few plants will perform well and some may not survive.
It is thought that boron plays several essential roles in animals, including humans, but the exact physiological role is poorly understood. A small human trial published in 1987 reported on postmenopausal women first made boron deficient and then repleted with 3 mg/day. Boron supplementation markedly reduced urinary calcium excretion and elevated the serum concentrations of 17 beta-estradiol and testosterone.
The U.S. Institute of Medicine has not confirmed that boron is an essential nutrient for humans, so neither a Recommended Dietary Allowance (RDA) nor an Adequate Intake have been established. Adult dietary intake is estimated at 0.9 to 1.4 mg/day, with about 90% absorbed. What is absorbed is mostly excreted in urine. The Tolerable Upper Intake Level for adults is 20 mg/day.
In 2013, a hypothesis suggested it was possible that boron and molybdenum catalyzed the production of RNA on Mars with life being transported to Earth via a meteorite around 3 billion years ago.
There exist several known boron-containing natural antibiotics. The first one found was boromycin, isolated from streptomyces.
Congenital endothelial dystrophy type 2, a rare form of corneal dystrophy, is linked to mutations in SLC4A11 gene that encodes a transporter reportedly regulating the intracellular concentration of boron.
For determination of boron content in food or materials, the colorimetric curcumin method is used. Boron is converted to boric acid or borates and on reaction with curcumin in acidic solution, a red colored boron-chelate complex, rosocyanine, is formed.
Elemental boron, boron oxide, boric acid, borates, and many organoboron compounds are relatively nontoxic to humans and animals (with toxicity similar to that of table salt). The LD50 (dose at which there is 50% mortality) for animals is about 6 g per kg of body weight. Substances with LD50 above 2 g are considered nontoxic. An intake of 4 g/day of boric acid was reported without incident, but more than this is considered toxic in more than a few doses. Intakes of more than 0.5 grams per day for 50 days cause minor digestive and other problems suggestive of toxicity. Dietary supplementation of boron may be helpful for bone growth, wound healing, and antioxidant activity, and insufficient amount of boron in diet may result in boron deficiency.
Single medical doses of 20 g of boric acid for neutron capture therapy have been used without undue toxicity.
Boric acid is more toxic to insects than to mammals, and is routinely used as an insecticide.
The boranes (boron hydrogen compounds) and similar gaseous compounds are quite poisonous. As usual, it is not an element that is intrinsically poisonous, but their toxicity depends on structure. The boranes are also highly flammable and require special care when handling. Sodium borohydride presents a fire hazard owing to its reducing nature and the liberation of hydrogen on contact with acid. Boron halides are corrosive.
Boron is necessary for plant growth, but an excess of boron is toxic to plants, and occurs particularly in acidic soil. It presents as a yellowing from the tip inwards of the oldest leaves and black spots in barley leaves, but it can be confused with other stresses such as magnesium deficiency in other plants. | 0.863732 | 3.074792 |
“Billions and billions of stars.” Carl Sagan’s awestruck if indeterminate census of the universe became a comic catchphrase in the wake of his 1980s PBS series Cosmos. Johnny Carson would intone the line, exaggerating the astrophysicist’s sing-songish repetition of billions and we’d laugh. Not because Sagan’s estimate was so low (estimates currently put the figure at between 10 sextillion and 1 septillion), but in part because the mere idea of billions of suns and consequent solar systems like our own is a patently impossible notion to comprehend. Contemplating god (as a bearded chap on a throne or some vague organizing “force) is water off a duck compared to the mental rearrangements required by the proposition that everyone alive and who has ever lived amounts to nothing more than a mote of cosmic dust. Now that’s hilarious.
In the early 1950s astronomers at the Palomar Observatory in California, including Edward Hubble, embarked on an ambitious project — to create a complete photographic survey of the sky a nine year effort that was funded — given its longstanding interest in cartography — by The National Geographic Society. The original glass plates represented the most advanced photographic technology of the time; they were exposed for long periods in order to capture objects well outside the range of human vision. Prints made from the negative plates (they show the sky as white space and stars as black pinpoints), which are currently on view at Apexart, look nothing like the nighttime sky. Instead, it’s the empyrean perhaps as seen on another planet where either the sky is the color of snow or the resident life forms process photons differently.
Writer and filmmaker Greg Allen, who sought out the images, has tightly packed an entire wall of gallery with the plates, assembling them to evoke a sense of vastness. Only a small portion of the more than 900 images that were produced for The Palomar Observatory Sky Survey are on display, but the overall effect is still overwhelming. Billions of stars (surely not septillions) can be only hinted at; peering closely at any one print reveals uncountable black points. Stepping back to take in the entire wall — floor to ceiling — gives the viewer a bracing sense of what facing down even a piece of the universe might be like. A smudge is a galaxy. Each microscopic speck is a sun, one probably larger than ours, its own populous family of planets wheeling around it; whole worlds — mythologies, evolutions, geologies, monarchies, and languages — about which we know nothing more than this atom-like freckle. And, to those beings perusing some sky atlas light years away, vice versa.
This grandeur of such insignificance is, I suppose, as close as I can get these days to spiritual sentiment. As a child I stared up at the ceiling of my church, a vaulted blue expanse decorated with gold stars, and felt securely situated in an ornately rendered cosmos. God hovered up there over all of us and we knelt below; we had a role in a comprehensible story and were contained within a universe that was geographically legible and soothingly finite. The sky atlas suggests no such arrangement. These photos provide no evidence of hierarchy or narrative; instead there are stars. More than any mind can fully see or imagine; more, I’m sure, than any god might create. The immensity of it all inspires slack-jawed wonderment and my own less-ness in its midst is indeed cause for an almost holy kind of laughter. | 0.862724 | 3.551884 |
The biggest volcano on the Jupiter moon Io should erupt any day now.
Loki Patera, a 125-mile-wide (200 kilometers) lava lake on the most volcanically active body in the solar system, has had fairly regular activity over the past few decades. And it’s due for an outburst very soon.
“If this behavior remains the same, Loki should erupt in September 2019, around the same time as the EPSC-DPS meeting in Geneva,” Julie Rathbun, a senior scientist at the Planetary Science Institute in Tucson, Arizona, said in a statement yesterday (Sept. 17). “We correctly predicted that the last eruption would occur in May of 2018.“
What Drives Io Largest Volcano Eruption?
Scientists aren’t sure what drives Loki Patera’s outbursts, but the leading explanation posits a process very different than what’s behind typical volcanic eruptions here on Earth: The top layer of Loki Patera solidifies, then falls into the still-liquid portion below.
And the intrigue surrounding Loki Patera doesn’t stop there: the periodicity of the lake’s eruptions has changed over the decades as well. The outbursts occurred every 540 Earth days or so in the 1990s. The periodic behavior seemed to stop in the early 2000s but reappeared around 2013, with eruptions now happening roughly every 475 days.
Given all these shifts and uncertainties, Rathbun isn’t exactly betting the farm on a Loki Patera flare-up in the next few days.
“Volcanoes are so difficult to predict because they are so complicated. Many things influence volcanic eruptions, including the rate of magma supply, the composition of the magma — particularly the presence of bubbles in the magma, the type of rock the volcano sits in, the fracture state of the rock and many other issues,” Rathbun said in the same statement.
“We think that Loki could be predictable because it is so large,” she added. “Because of its size, basic physics are likely to dominate when it erupts, so the small complications that affect smaller volcanoes are likely to not affect Loki as much. However, you have to be careful because Loki is named after a trickster god [in Norse mythology], and the volcano has not been known to behave itself.“
Loki Patera’s activity cycle is far too lengthy to be tied to Io’s orbit around Jupiter, which is supertight; the moon completes one lap every 1.77 Earth days. So, researchers think that gravitational interactions among Io and some of its fellow moons may be responsible for the (semi) regularity.
Jupiter’s powerful gravity is the root cause of Io’s volcanism overall, however. The planet’s constant tug stretches Io’s innards, melting moon rock into magma via tidal heating. (Reminder: Lava is just magma that has reached the surface of a planet or moon.)
I think when the largest volcano on Io will erupt, we will name it a Giga-Mega-Eruption… Well just enormous in comparison to our earthy supervolcanoes. Source link | 0.895635 | 3.59358 |
“Ninety-six clusters of stars in the sky…. Ninety-six clusters of stars… You take one down and pass it around…” Do you need ninety-six new reasons to love astronomy? Then you’re going to want to hear about all the new discoveries the VISTA infrared survey telescope at ESO’s Paranal Observatory has made. Read on…
An international team of astronomers has taken observations to the next level with their discovery of 96 new star clusters which have been hidden behind the dusty cloak of interstellar matter. By utilizing sensitive infrared detectors and the world’s largest survey telescope, the intrepid crew set a new record for finding so many faint and small clusters at one time.
“This discovery highlights the potential of VISTA and the VVV survey for finding star clusters, especially those hiding in dusty star-forming regions in the Milky Way’s disc. VVV goes much deeper than other surveys,” says Jura Borissova, lead author of the study.
As astronomy enthusiasts well know, there’s more to a galactic cluster than just a pretty grouping of stars. Age, relation and motion all play a role. Some are loose groupings – held together by mutual gravitational attraction. Others are torn apart through interactions. Still others are in the process of formation, caught in the act with their gases showing. Yet all share a common denominator: they are around few hundred million years old and they are the by-product of a galaxy with active star formation.
“In order to trace the youngest star cluster formation we concentrated our search towards known star-forming areas. In regions that looked empty in previous visible-light surveys, the sensitive VISTA infrared detectors uncovered many new objects,” adds Dante Minniti, lead scientist of the VVV survey.
Once the grouping has been discovered, classification comes next. Through the use of specialized computer software, the team was able to separate foreground stars from genuine cluster components. Observation then came into play as stellar members were counted, sizes estimated, distances computed and extinction taken into consideration.
“We found that most of the clusters are very small and only have about 10–20 stars. Compared to typical open clusters, these are very faint and compact objects — the dust in front of these clusters makes them appear 10,000 to 100 million times fainter in visible light. It’s no wonder they were hidden,” explains Radostin Kurtev, another member of the team.
Since antiquity only 2500 open clusters have been found in the Milky Way, but astronomers estimate there might be as many as 30,000 still hiding behind the dust and gas. That means these new 96 open clusters could be only the very beginning of a host of new discoveries. “We’ve just started to use more sophisticated automatic software to search for less concentrated and older clusters. I am confident that many more are coming soon,” adds Borissova.
Until then we’ll just “Take one down and pass it around… 29,999 clusters of stars in the sky.”
Original Story Source: ESO Press Release. | 0.917135 | 3.81544 |
On September 5, 1977, NASA launched the Voyager 1 space probe to study the Jovian planets Jupiter and Saturn, and their moons, and the interstellar medium, the gigantic chasm between various star-systems in the universe. It’s been 35 years and 9 months, and Voyager has kept on, recently entering the boundary between our System and the Milky Way.
In 2012, however, when nine times farther from the Sun than is Neptune, the probe entered into a part of space completely unknown to astronomers.
On June 27, three papers were published in Science discussing what Voyager 1 had encountered, a region at the outermost edge of the Solar System they’re calling the ‘heliosheath depletion region’. They think it’s a feature of the heliosphere, the imagined bubble in space beyond whose borders the Sun has no influence.
“The principal result of the magnetic field observations made by our instrument on Voyager is that the heliosheath depletion region is a previously undetected part of the heliosphere,” said Dr. Leonard Burlaga, an astrophysicist at the NASA-Goddard Space Flight Centre, Maryland, and an author of one of the papers.
“If it were the region beyond the heliosphere, the interstellar medium, we would have expected a change in the magnetic field direction when we crossed the boundary of the region. No change was observed.”
More analysis of the magnetic field observations showed that the heliosheath depletion region has a weak magnetic field – of 0.1 nano-Tesla (nT), 0.6 million times weaker than Earth’s – oriented in such a direction that it could only have arisen because of the Sun. Even so, this weak field was twice as strong as what lay outside it in its vicinity. Astronomers would’ve known why, Burlaga clarifies, if it weren’t for the necessary instrument on the probe being long out of function.
When the probe crossed over into the region, this spike in strength was recorded within a day. Moreover, Burlaga and others have found that the spike happened thrice and a drop in strength twice, leaving Voyager 1 within the region at the time of their analysis. In fact, after August 25, 2012, no drops have been recorded. The implication is that it is not a smooth region.
“It is possible that the depletion region has a filamentary character, and we entered three different filaments. However, it is more likely that the boundary of the depletion region was moving toward and away from the sun,” Burlaga said.
The magnetic field and its movement through space are not the only oddities characterising the heliosheath depletion region. Low-energy ions blown outward by the Sun constantly emerge out of the heliosphere, but they were markedly absent within the depletion region. Burlaga was plainly surprised: “It was not predicted or even suggested.”
Analysis by Dr. Stamatios Krimigis, the NASA principal investigator for the Low-Energy Charged Particle (LECP) experiment aboard Voyager 1 and an author of the second paper, also found that cosmic rays, which are highly energised charged particles produced by various sources outside the System through unknown mechanisms, weren’t striking Voyager’s detectors equally from all directions. Instead, more hits were being recorded in certain directions inside the heliosheath depletion region.
Burlaga commented, “The sharp increase in the cosmic rays indicate that cosmic rays were able to enter the heliosphere more readily along the magnetic fields of the depletion region.”
Even though Voyager 1 was out there, Krimigis feels that humankind is blind: astronomers’ models were, are, clearly inadequate, and there is no roadmap of what lies ahead. “I feel like Columbus who thought he had gotten to West India, when in fact he had gone to America,” Krimigis contemplates. “We find that nature is much more imaginative than we are.”
With no idea of how the strange region originated or whence, we’ll just have to wait and see what additional measurements tell us. Until then, the probe will continue approaching the gateway to the Galaxy.
This blog post, as written by me, first appeared in The Hindu‘s science blog on June 29, 2013. | 0.843583 | 3.927192 |
March 6, 2015 – NASA’s Dawn spacecraft has become the first mission to achieve orbit around a dwarf planet. The spacecraft was approximately 38,000 miles (61,000) kilometers from Ceres when it was captured by the dwarf planet’s gravity at about 4:39 a.m. PST (7:39 a.m. EST) Friday. Located in the main asteroid belt between Mars and Jupiter, Ceres is the largest unexplored world of the inner solar system.
Dawn, designed and built by Orbital ATK, accomplished this feat with the innovative use of solar electric ion propulsion, the world’s most advanced and efficient space propulsion technology.
Mission controllers at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California received a signal from the spacecraft at 5:36 a.m. PST (8:36 a.m. EST) that Dawn was healthy and thrusting with its ion engine, the indicator Dawn had entered orbit as planned.
“We feel exhilarated,” said Chris Russell, principal investigator of the Dawn mission at the University of California, Los Angeles (UCLA). “We have much to do over the next year and a half, but we are now on station with ample reserves, and a robust plan to obtain our science objectives.”
Now in its eighth year of a nearly nine-year-long mission, Dawn has already advanced human understanding of planetary formation by giant leaps with the data it has returned over the last four years.
“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.”
Beginning in January, Dawn has returned increasingly sharper images of Ceres, showing a heavily cratered surface with multiple intriguing, bright features. Dawn’s image quality now substantially exceeds the best available from the ground-based W.M. Keck Observatory and NASA’s Hubble Space Telescope.
By later this year, in its closest orbit around Ceres, Dawn will return images more than 800 times the resolution of Hubble. The images will provide mission scientists with a treasure trove of data to understand how Ceres evolved so differently from Vesta.
The most recent images received from the spacecraft, taken on March 1 show Ceres as a crescent, mostly in shadow because the spacecraft’s trajectory put it on a side of Ceres that faces away from the sun until mid-April. When Dawn emerges from Ceres’ dark side, it will deliver ever-sharper images as it spirals to lower orbits around the planet.
In addition to being the first spacecraft to visit a dwarf planet, Dawn also has the distinction of being the first mission to orbit two extraterrestrial targets. From 2011 to 2012, the spacecraft explored the giant asteroid Vesta, the second most massive object in the main asteroid belt and the first destination on this two-stop planetary mission. The spacecraft spent nearly 14 months orbiting and mapping Vesta, returning more than 30,000 images and other measurements of the protoplanet.
Dawn’s mission is managed by JPL for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. | 0.882054 | 3.525728 |
Astronomers using the NASA/ESA Hubble Space telescope have taken a series of spectacular images featuring the fluttering auroras at the north pole of Saturn. The observations were taken in ultraviolet light and the resulting images provide astronomers with the most comprehensive picture so far of Saturn’s northern aurora.
In 2017, over a period of seven months, the NASA/ESA Hubble Space Telescope took images of auroras above Saturn’s north pole region using the Space Telescope Imaging Spectrograph. The observations were taken before and after the Saturnian northern summer solstice. These conditions provided the best achievable viewing of the northern auroral region for Hubble.
On Earth, auroras are mainly created by particles originally emitted by the Sun in the form of solar wind. When this stream of electrically charged particles gets close to our planet, it interacts with the magnetic field, which acts as a gigantic shield. While it protects Earth’s environment from solar wind particles, it can also trap a small fraction of them. Particles trapped within the magnetosphere — the region of space surrounding Earth in which charged particles are affected by its magnetic field — can be energised and then follow the magnetic field lines down to the magnetic poles. There, they interact with oxygen and nitrogen atoms in the upper layers of the atmosphere, creating the flickering, colourful lights visible in the polar regions here on Earth .
However, these auroras are not unique to Earth. Other planets in our Solar System have been found to have similar auroras. Among them are the four gas giants Jupiter, Saturn, Uranus and Neptune. Because the atmosphere of each of the four outer planets in the Solar System is — unlike the Earth — dominated by hydrogen, Saturn’s auroras can only be seen in ultraviolet wavelengths; a part of the electromagnetic spectrum which can only be studied from space.
Hubble allowed researchers to monitor the behaviour of the auroras at Saturn’s north pole over an extended period of time. The Hubble observations were coordinated with the “Grand Finale” of the Cassini spacecraft, when the spacecraft simultaneously probed the auroral regions of Saturn . The Hubble data allowed astronomers to learn more about Saturn’s magnetosphere, which is the largest of any planet in the Solar System other than Jupiter.
The images show a rich variety of emissions with highly variable localised features. The variability of the auroras is influenced by both the solar wind and the rapid rotation of Saturn, which lasts only about 11 hours. On top of this, the northern aurora displays two distinct peaks in brightness — at dawn and just before midnight. The latter peak, unreported before, seems specific to the interaction of the solar wind with the magnetosphere at Saturn’s solstice.
The main image presented here is a composite of observations made of Saturn in early 2018 in the optical and of the auroras on Saturn’s north pole region, made in 2017, demonstrating the size of the auroras along with the beautiful colours of Saturn.
Hubble has studied Saturn’s auroras in the past. In 2004, it studied the southern auroras shortly after the southern solstice (heic0504) and in 2009 it took advantage of a rare opportunity to record Saturn when its rings were edge-on (heic1003). This allowed Hubble to observe both poles and their auroras simultaneously.
Notes The auroras here on Earth have different names depending on which pole they occur at. Aurora Borealis, or the northern lights, is the name given to auroras around the north pole and Aurora Australis, or the southern lights, is the name given for auroras around the south pole. Cassini was a collaboration between NASA, ESA and the Italian Space Agency. It spent 13 years orbiting Saturn, gathering information and giving astronomers a great insight into the inner workings of Saturn. Cassini took more risks at the end of its mission, travelling through the gap between Saturn and its rings. No spacecraft had previously done this, and Cassini gathered spectacular images of Saturn as well as new data for scientists to work with. On 15 September 2017 Cassini was sent on a controlled crash into Saturn. | 0.844945 | 4.009092 |
eso9522 — Photo Release
The Spectacular Jet in Comet Hale-Bopp
1 September 1995
A new image of comet Hale-Bopp, taken at ESO's observatory in La Silla, sheds new light on the structure of this peculiar comet.
This false-colour image of the large jet now observed in bright comet Hale-Bopp is a computer-enhanced version of a near-IR CCD-frame. It was obtained on August 31 with the multi-mode DFOSC instrument at the Danish 1.5-m telescope on La Silla by Emilio Molinari from Osservatorio di Brera, Milano-Merate, Italy. On this photo, North is up and East is to the left. One pixel measures 0.5 arcsec and the circular field has a diameter of 65 arcsec. The intensity scale is indicated with the colour bar at the bottom; the intensity increases towards the right.
The exposure lasted 5 minutes and was made through a gunn-i filter, recording the reflected sunlight from the dusty coma of the comet at a wavelength of about 9000 A (900 nm). The observing conditions were excellent (seeing 0.8 arcsec).
The frame was transmitted over the satellite link to the ESO Headquarters in Garching (Germany) where it was processed on the MIDAS system by Hans Ulrich Kaeufl (ESO). In order to isolate the light from the jet, the stars were partially removed and the symmetrical part of the coma was subtracted. In this way, only the asymmetrical structures in the frame, including the image of the jet, are left. The brightest part of the coma, in which the comet's nucleus is located, is seen as a white spot at the centre.
The image shows that the jet emerges at a distance of about 3 arcsec North-West from the centre, curves towards North and then abruptly bends 90 deg towards North-East. The same structure is seen on another image, obtained on September 1 with the same instrumentation. Thus, no clear signs of rotation of the nucleus can be perceived from these observations. | 0.832412 | 3.424978 |
“You can spend too much time wondering which of identical twins is the more alike.” -Robert Brault
Earlier today, NASA announced the "most Earth-like exoplanet yet," a planet just 60% larger in radius than our own, orbiting a star of the same spectral class as our Sun and with an almost identical orbital period: 385 days.
But is this really the most Earth-like planet we've discovered? It's significantly larger and five times as massive, and may actually be more like Neptune than like Earth. In fact, other properties may be much more important if we truly want to find a "twin" to Earth: a rocky planet teeming with advanced chemical-based life.
What do we have versus what did we find? Come discover it all on today's Throwback Thursday!
Is earth’s twin out there?
Heck, the earth probably has BILLIONS of twins (and so do you), in that bit of fiction, that curious time and space which we call…
The Twilight Zone
(a.k.a. the “multiverse.”).
On Space.com in quick 1 minutes, 16 second video they put together for the announcement, they have a graph in the middle of the video showing the shifting habitable zone of a star over time.
Just before the star goes into the red giant phase and burns up the planets, the graph shows the stars spend half a billion years cooling slightly. What is happening there? What is it that creates a pause in the otherwise inexorable rise in temperature over a star's lifetime?
No, see fuck all, the twilight zone is a work of fiction. Rather like Christianity.
The Multiverse is a consequence of known science. Not fiction.
Then again you think that fiction is reality, so why is anyone surprised you think the twilight zone is reality...
Denier, there is no inexorable rise without a pause even BEFORE that event.
The change in the habitable zone is not due to a change in temperature of the star. Just its surface luminosity. Which depends on the size and temperature of the star.
And when a star goes from yellow dwarf to red giant, the colour change indicates the temperature is falling.
The result of that is complicated, but can result in either a reduction in the solar constant or an increase of it, depending on what's going on specifically with that size and composition of star.
"The Multiverse is a consequence of known science"
Got any observable proof?
If not then your know science is a "post-empirical" load of bollocks.
"Got any observable proof?"
Yes, known science is the result of observed phenomena, retard.
Hey, raggie, ever seen the inside of a brick?
Then your belief that there is an interior to that brick is "post-empirical bollocks".
Ever seen Thomas Jefferson? No? Then your belief that one of the founding fathers existed is "post-empirical bollocks".
How many false set ups can I do now you've done one?
Re. Ragtag Media @ 5:
Having read your linked article, what I see looks a lot like political partisans ginning up a controversy when they should be cooperating.
The reason string theory and multiverse theory exist in the first place is that they are logical outgrowths of attempts to reconcile problems in our existing theories. The fact that they are both untestable _at present_ does not mean that either or both of them will never generate a testable prediction. The only way to find out is to keep going and see where they get us.
I don't see physics or cosmology turning into postmodernist mush there. Empiricism is not dead nor even injured: it's still the gold standard and, if nothing else, produces too many useful results to be abandoned. So in both a principled way and a pragmatic way, it will remain.
The solution to the real debate over theory today, is to increase funding, hiring, research, and teaching accordingly. As for where to get the money, various progressive taxes will do nicely, and any sane Republican should also agree that if Nixon was a good conservative, then the Nixon-era tax rates are acceptable. That will buy us all the scientists, professors, labs, space telescopes, and scholarships from undergrad to post-doctoral fellowships, that we need. (On a different issue entirely, that kind of revenue will also buy us the replacement of fossil fuel energy sources with climate-clean power, which will buy us time to deal with the underlying factors in ecological overshoot, and prepare the way forward toward a very real renaissance.)
People coming up through these fields also need to be educated in the psychology of science, which is to say, they need to learn and recognize and internalize the point that they should not become so emotionally committed to any given theory as to compromise their objectivity or put them at risk of existential crisis should their preferred theory be falsified or superseded. Some of these theories are going to be knocked out of the running, and the people who are committed to them should be able to accept that situation with grace and then turn their attention to new problems.
We could be on the verge of climate catastrophe, and we could also be on the verge of a scientific renaissance that enables us to look even further into the fundamental questions of existence. This is one of those historic times when both the existence of civilization itself, and the highest aspirations of humanity, are both in play. There is no room for apathy or laziness in the face of such potential.
Re. Ethan's article:
If I understand you correctly:
= Reasonable calculations lead to the conclusion that star systems & planets that duplicate the Sun & Earth scenario, are relatively few in number.
= The enormous number of M-class red dwarfs offers a potentially highly fruitful set of places to look for planets that might harbor intelligent life.
OK, that makes sense. From previous articles, I also get that it is going to take a substantial improvement in our technology, to be able to resolve objects of the relevant sizes.
Now heading off into wild speculation territory: Re. what you said about planets in the habitable zone of M-class red dwarfs being exposed to solar flares and the like: How would an intelligent civilization protect a planet's ecosystems & habitability from any such events?
I'm still convinced that the convergent solution for intelligent life is to aim for interstellar civilization based on "rogue" (free-floating) planets and Dyson rings around suitable stars as remote energy sources: a network of these types of objects adds up to something highly resilient and robust.
And I'm also thinking that NASA is going to surprise us with an announcement about signs of rudimentary life, sooner than we expect. Perhaps soon enough to bear on next year's election. One can hope, anyway.
BTW, can we do something about cleaning up the comments around here?, they've been getting downright repellant but I've decided to not let it deter me. Others may not have such a large supply of barf bags at hand. Better to make good use of the broom and shovel.
"How would an intelligent civilization protect a planet’s ecosystems & habitability from any such events?"
The problem really isn't the actions of intelligent life but the problem of getting TO intelligent life that is advanced enough to do something to stop them dying when the sun flares up.
The problems of flares and so on are much like we get here with CME's (read up on them), but worse.
Hardening against EM damage, non reliance on kit affected, or just burying yourself under the crust and wait it out are all options. If you're landing there from some other planet. | 0.849818 | 3.025963 |
A very rapidly evolving, supermassive star with a newly formed nebula only a few thousand years old
Space news (supermassive stars: Wolf-Rayet stars; star NaSt1) – 3,000 light-years away on the edge of a pancake-shaped disk of gas moving at 22,000 mph –
Astronomers using the Hubble Space Telescope have discovered new clues concerning a nearby supermassive, rapidly aging star they have nicknamed “Nasty 1”. Designated NaSt1 in astronomy catalogs, “Nasty 1” when first discovered decades ago was identified as a non-typical Wolf-Rayet star with an orbiting disk-like structure. A vast disk estimated to be almost 2 trillion miles wide astronomers now think formed due to a companion star snacking on its outer envelope. Putting NaSt1 in a class of Wolf-Rayet stars astronomers haven’t observed often during the human journey to the beginning of space and time. A star type possibly representing a transition stage in the evolution of supermassive stars.
“We were excited to see this disk-like structure because it may be evidence for a Wolf-Rayet star-forming from a binary interaction,” said study leader Jon Mauerhan of the University of California, Berkeley. “There are very few examples in the galaxy of this process in action because this phase is short-lived, perhaps lasting only a hundred thousand years, while the timescale over which a resulting disk is visible could be only ten thousand years or less.”
In the case of NaSt1, computer simulations show a supermassive star evolving really fast and swelling as it begins to run out of hydrogen. Its outer hydrogen envelope is loosely bound and is gravitationally stripped from the star- astronomers call this process stellar cannibalism – by a more compact, nearby companion star. In the process the more compact star gains mass, while the more massive star loses its hydrogen envelope, exposing its helium core and eventually becoming a Wolf-Rayet star.
The mass-transfer model is the favored process for how Wolf-Rayet stars evolve at the moment and considering at least 70 percent of supermassive stars detected, so far, are members of binary star system, this seems logical. Astronomers used to think this type of star could also form when a massive sun ejects its hydrogen envelope. But the direct mass loss model by itself can’t account for the number of Wolf-Rayet stars observed relative to less-evolved supermassive suns in the Milky Way.
“We’re finding that it is hard to form all the Wolf-Rayet stars we observe by the traditional wind mechanism because the mass loss isn’t as strong as we used to think,” said Nathan Smith of the University of Arizona in Tucson, who is a co-author on the new NaSt1 paper. “Mass exchange in binary systems seems to be vital to account for Wolf-Rayet stars and the supernovae they make, and catching binary stars in this short-lived phase will help us understand this process.”
Astronomers computer models show that the mass-transfer process isn’t always perfectly efficient. Matter can only transfer from NaSt1 at a certain rate, left over material begins orbiting, creating a disk-like structure.
“That’s what we think is happening in Nasty 1,” Mauerhan said. “We think there is a Wolf-Rayet star buried inside the nebula, and we think the nebula is being created by this mass-transfer process. So this type of sloppy stellar cannibalism actually makes Nasty 1 a rather fitting nickname.”
Observing Nasty 1 (star NaSt1) through the clock of gas and dust surrounding this star system hasn’t been easy. The intervening disk-like structure even blocks the view of the Hubble Space Telescope. Scientists haven’t been able to measure the distance between the stars, their mass, or the volume of material transferring to the smaller companion star.
Astronomers have been able to discover a few items concerning the disk-like structure surrounding Nasty 1. Measurements indicate it’s traveling at around 22,000 mph in the outer nebula, a slower speed than recorded in other stars of this type. Scientists think this indicates a much less energetic supernova than was recorded for other events, like Era Carinae. In this case and other similar stars, the gas in the outer nebula has been recorded in the hundreds of thousands of miles per hour. Nasty 1 could be different supernova animal altogether.
Nasty 1 could also lose its outer envelope of hydrogen intermittently. Previous studies in the infrared light provided clues indicating the existence of a dense pocket of hot gas and dust close to the central stars in the region. More recent observations using the Magellan Telescope located at the Las Campanas Observatory in Chile has also detected a bigger pocket of cooler gas and dust possibly indirectly blocking light from these stars. Astronomers think the existence of warm dust in the region implies it formed just recently, perhaps intermittently, as elementally enriched matter from the stellar winds of massive stars collides, mixes, flows away, and cools. Irregular stellar wind strength, the rate at which star NaSt1 loses its outer envelope, could also help explain the observed clumpy structure and gaps noted in the outer regions of the disk.
Astrophysicists used NASA’s Chandra X-ray Observatory to measure the hypersonic winds screaming from each star. Readings showed a scorching hot plasma, indicating colliding stellar winds producing high-energy shockwaves that glow in X-rays. This is consistent with previous data collected on other evolving Wolf-Rayet star systems. We’ll get a better view once the outer hydrogen of Nasty 1’s (star NaSt1) depleted, and the mass-transfer process completes. Eventually, the gas and dust in the lumpy, disk-like structure will dissipate, giving us a clearer view of this mysterious binary star system.
Nasty 1’s still evolving!
“What evolutionary path the star will take is uncertain, but it will definitely not be boring,” said Mauerhan. “Nasty 1 could evolve into another Eta Carinae-type system. To make that transformation, the mass-gaining companion star could experience a giant eruption because of some instability related to the acquiring of matter from the newly formed Wolf-Rayet. Or, the Wolf-Rayet could explode as a supernova. A stellar merger is another potential outcome, depending on the orbital evolution of the system. The future could be full of all kinds of exotic possibilities depending on whether it blows up or how long the mass transfer occurs, and how long it lives after the mass transfer ceases.”
Astronomers continue to study Nasty 1 and its peculiar, unusual disk-like structure looking for clues to explain the mysteries surrounding its origin.
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Discover the Magellan Telescope. | 0.904114 | 3.858023 |
It is expected that NASA’s Parker Solar Probe will be launched in early August. It is the first NASA’s mission of this kind. The car-sized spacecraft will study the Sun closer than any human-made object ever has.
Using Venus’ gravity, the Probe will gradually get closer to the sun over the course of 7 years. The Probe will fly to the sun’s corona, providing the closest observations of a star to date. The main mission goals are to understand how energy and heat move through the corona and learn what accelerates the solar wind and energetic particles.
Illustration of the Parker Solar Probe spacecraft approaching the sun. Credit: Johns Hopkins University Applied Physics Laboratory
According to info on the website, “At closest approach, Parker Solar Probe hurtles around the sun at approximately 430,000 mph (700,000 kph). That’s fast enough to get from Philadelphia to Washington, D.C., in one second.”
“The spacecraft will need to withstand temperatures that reach almost 2,500 F, or 1,377 C. This is possible through advances in thermal engineering.”
“We’ve been studying the Sun for decades, and now we’re finally going to go where the action is,” said Alex Young, associate director for science in the Heliophysics Science Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Our Sun is far more complex than meets the eye. Rather than the steady, unchanging disk it seems to human eyes, the Sun is a dynamic and magnetically active star. The Sun’s atmosphere constantly sends magnetized material outward, enveloping our solar system far beyond the orbit of Pluto and influencing every world along the way.
“The Sun’s energy is always flowing past our world,” said Nicky Fox, Parker Solar Probe’s project scientist at the Johns Hopkins University Applied Physics Lab in Laurel, Maryland.
“And even though the solar wind is invisible, we can see it encircling the poles as the aurora, which are beautiful – but reveal the enormous amount of energy and particles that cascade into our atmosphere. We don’t have a strong understanding of the mechanisms that drive that wind toward us, and that’s what we’re heading out to discover.”
There are many unanswered questions about or Sun.
One of those questions is the mystery of the acceleration of the solar wind, the Sun’s constant outflow of material.
Data shows that many changes happen in the corona, a region of the Sun’s atmosphere that Parker Solar Probe will fly directly through, and scientists plan to use Parker Solar Probe’s remote and in situ measurements to shed light on how this happens.
Interesting is also the secret of the corona’s enormously high temperatures. The visible surface of the Sun is about 10,000 F – but, for reasons we don’t fully understand, the corona is hundreds of times hotter, spiking up to several million degrees F. This is counterintuitive, as the Sun’s energy is produced at its core.
“It’s a bit like if you walked away from a campfire and suddenly got much hotter,” said Fox.
Parker Solar Probe needs is energy – getting to the Sun takes a lot of energy at launch to achieve its orbit around the Sun. That’s because any object launched from Earth starts out traveling around the Sun at the same speed as Earth – about 18.5 miles per second – so an object has to travel incredibly quickly to counteract that momentum, change direction, and go near the Sun.
The timing of Parker Solar Probe’s launch – between about 4 and 6 a.m. EDT, and within a period lasting about two weeks – was very precisely chosen to send Parker Solar Probe toward its first, vital target for achieving such an orbit: Venus.
“The launch energy to reach the Sun is 55 times that required to get to Mars, and two times that needed to get to Pluto,” said Yanping Guo from the Johns Hopkins Applied Physics Laboratory, who designed the mission trajectory. “During summer, Earth and the other planets in our solar system are in the most favorable alignment to allow us to get close to the Sun.”
The spacecraft will perform a gravity assist to shed some of its speed into Venus’ well of orbital energy, drawing Parker Solar Probe into an orbit that – already, on its first pass – carries it closer to the solar surface than any spacecraft has ever gone, well within the corona. Parker Solar Probe will perform similar maneuvers six more times throughout its seven-year mission, assisting the spacecraft to final sequence of orbits that pass just over 3.8 million miles from the photosphere. | 0.81524 | 3.801075 |
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Earlier infrared data did not have sufficient resolution to separate MK 2 from Makemake's veiling glare. The astronomers' reanalysis, however, based on the more recent HST observations, indicates that much of the warmer surface spotted earlier in infrared light may simply be the dark surface of the companion MK 2.
Ganymede, and four other moons dwelling in our Sun's family, possess liquid water beneath their frigid crusts of ice. The others are Saturn's moons, Titan and Enceladus, and two other Galilean moons of Jupiter--Europa and Callisto. Planetary scientists think the oceans of Europa and Enceladus are in contact with rock--thus making these two moons high-priority targets for future astrobiology missions.
Titan has a radius that is about 50% wider than Earth's Moon. It is approximately 759,000 miles from its parent-planet Saturn, which itself is about 886 million miles from our Sun--or 9.5 astronomical units (AU). One AU is equal to the average distance between Earth and Sun, which is 93,000,000 miles. The light that streams out from our Star takes about 80 minutes to reach Saturn. Because of this vast distance, sunlight is 100 times more faint at Saturn and Titan than on Earth.
- Cassini Satellite Fun
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- Water On Planet Mercury | 0.924355 | 3.222602 |
General relativity known as the general theory of relativity, is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present; the relation is specified by the Einstein field equations, a system of partial differential equations. Some predictions of general relativity differ from those of classical physics concerning the passage of time, the geometry of space, the motion of bodies in free fall, the propagation of light. Examples of such differences include gravitational time dilation, gravitational lensing, the gravitational redshift of light, the gravitational time delay; the predictions of general relativity in relation to classical physics have been confirmed in all observations and experiments to date.
Although general relativity is not the only relativistic theory of gravity, it is the simplest theory, consistent with experimental data. However, unanswered questions remain, the most fundamental being how general relativity can be reconciled with the laws of quantum physics to produce a complete and self-consistent theory of quantum gravity. Einstein's theory has important astrophysical implications. For example, it implies the existence of black holes—regions of space in which space and time are distorted in such a way that nothing, not light, can escape—as an end-state for massive stars. There is ample evidence that the intense radiation emitted by certain kinds of astronomical objects is due to black holes. For example and active galactic nuclei result from the presence of stellar black holes and supermassive black holes, respectively; the bending of light by gravity can lead to the phenomenon of gravitational lensing, in which multiple images of the same distant astronomical object are visible in the sky.
General relativity predicts the existence of gravitational waves, which have since been observed directly by the physics collaboration LIGO. In addition, general relativity is the basis of current cosmological models of a expanding universe. Acknowledged as a theory of extraordinary beauty, general relativity has been described as the most beautiful of all existing physical theories. Soon after publishing the special theory of relativity in 1905, Einstein started thinking about how to incorporate gravity into his new relativistic framework. In 1907, beginning with a simple thought experiment involving an observer in free fall, he embarked on what would be an eight-year search for a relativistic theory of gravity. After numerous detours and false starts, his work culminated in the presentation to the Prussian Academy of Science in November 1915 of what are now known as the Einstein field equations; these equations specify how the geometry of space and time is influenced by whatever matter and radiation are present, form the core of Einstein's general theory of relativity.
The 19th century mathematician Bernhard Riemann's non-Euclidean geometry, called Riemannian Geometry, provided the key mathematical framework which Einstein fit his physical ideas of gravity on, enabled him to develop general relativity. The Einstein field equations are nonlinear and difficult to solve. Einstein used approximation methods in working out initial predictions of the theory, but as early as 1916, the astrophysicist Karl Schwarzschild found the first non-trivial exact solution to the Einstein field equations, the Schwarzschild metric. This solution laid the groundwork for the description of the final stages of gravitational collapse, the objects known today as black holes. In the same year, the first steps towards generalizing Schwarzschild's solution to electrically charged objects were taken, which resulted in the Reissner–Nordström solution, now associated with electrically charged black holes. In 1917, Einstein applied his theory to the universe as a whole, initiating the field of relativistic cosmology.
In line with contemporary thinking, he assumed a static universe, adding a new parameter to his original field equations—the cosmological constant—to match that observational presumption. By 1929, the work of Hubble and others had shown that our universe is expanding; this is described by the expanding cosmological solutions found by Friedmann in 1922, which do not require a cosmological constant. Lemaître used these solutions to formulate the earliest version of the Big Bang models, in which our universe has evolved from an hot and dense earlier state. Einstein declared the cosmological constant the biggest blunder of his life. During that period, general relativity remained something of a curiosity among physical theories, it was superior to Newtonian gravity, being consistent with special relativity and accounting for several effects unexplained by the Newtonian theory. Einstein himself had shown in 1915 how his theory explained the anomalous perihelion advance of the planet Mercury without any arbitrary parameters.
A 1919 expedition led by Eddington confirmed general relativity's prediction for the deflection of starlight by the Sun during the total solar eclipse of May 29, 1919, making Einstein famous. Yet the theory entered the mainstream of theoretical physics and astrophysics only with the developments between 1960 and 1975, now known as the golden age of general relativity. Physicists began to understand the concept of a black hole, to identify quasars as one
Nguyễn Phúc Lan was one of the Nguyễn lords who ruled south Vietnam from the city of Phú Xuân from 1635 to 1648. During his rule the Trịnh–Nguyễn War continued. Nguyễn Phúc Lan was the second son of Nguyễn Phúc Nguyên, his father died in the midst of the war by Trịnh Tráng to conquer the southern provinces. Unwilling to make peace, Nguyễn Phúc Lan continued his father's policies of maintaining a strong defensive position on the great walls while continuing friendly relations with the Portuguese and expanding south into Cambodian and Champa territory. Following after his grandfather, he took the title of Vuong. In 1640, famed Jesuit missionary Alexandre de Rhodes returned to Vietnam, this time to the Nguyễn court at Phú Xuân, he had been forced to leave the court at Hanoi ten years earlier but now he was back, reasoning that rules against him in Hanoi did not apply in Phú Xuân. He began work on converting people to the Roman Catholic building churches. However, after six years, Nguyễn Phúc Lan came to the same conclusion as Trịnh Tráng had: that de Rhodes and the Catholic Church represented a threat to his rule.
De Rhodes was condemned to death but the sentence was reduced to exile on pain of death should he return. De Rhodes never returned to Vietnam but Vietnamese Catholics remained and continued to practice their new religion. After a break of nine years, Trịnh Tráng launched a new major assault in 1642; this time they had their own European cannons, purchased from the Dutch. They had modern Dutch ships to lead their fleet. At first the assault went well and the first of the great walls was breached; the attack was renewed in 1643 but the second wall could not be taken. At sea, once again the Nguyễn fleet defeated the Royal fleet; the offensive halted and the Trịnh withdrew. On March 19, 1648, Nguyễn Phúc Lan died and was succeeded by his son, Nguyễn Phúc Tần, 28 years old. Lê dynasty List of Vietnamese dynasties Encyclopedia of Asian History, Volume 3 1988. Charles Scribner's Sons, New York Genealogy of the Royal Nguyen Family The Encyclopedia of Military History by R. Ernest Dupuy and Trevor N. Dupuy.
Harper & Row
Diego Carlos Santos Silva, or Diego Carlos, is a Brazilian professional defender who plays for Spanish club Sevilla FC. Diego began his senior career with Desportivo Brasil in the 2012–13 season. On 1 January 2013, Diego was sent out on loan to São Paulo. Diego spent the latter portion of the 2013–14 season out on loan at Paulista. Diego spent about a month out on loan at Madureira On 2 July 2014, Diego was sold to Estoril. In September 2014, Diego was loaned to FC Porto, he only played for the B team. In June 2016, it was announced; the transfer fee paid to Estoril was estimated at €2 million. On 14 January 2018, during a Ligue 1 match between Nantes and Paris Saint-Germain, referee Tony Chapron appeared to kick Diego following a collision, before sending him off for a second bookable offence. Chapron, suspended by the French Football Federation, admitted his mistake and asked for Diego Carlos' second yellow card to be rescinded; as a result, French football league withdrew the second yellow card.
On 31 May 2019, Spanish club Sevilla FC announced they had reached an agreement with Nantes for the transfer of Diego Carlos. As of match played 25 January 2020 Diego Carlos at ForaDeJogo Diego Carlos at Soccerway | 0.840052 | 4.310215 |
MUSE spectrograph reveals that nearly the entire sky in the early Universe is glowing with Lyman-alpha emission
Deep observations made with the MUSE spectrograph on ESO’s Very Large Telescope have uncovered vast cosmic reservoirs of atomic hydrogen surrounding distant galaxies. The exquisite sensitivity of MUSE allowed for direct observations of dim clouds of hydrogen glowing with Lyman-alpha emission in the early Universe — revealing that almost the whole night sky is invisibly aglow.
An unexpected abundance of Lyman-alpha emission in the Hubble Ultra Deep Field (HUDF) region was discovered by an international team of astronomers using the MUSE instrument on ESO’s Very Large Telescope (VLT). The discovered emission covers nearly the entire field of view — leading the team to extrapolate that almost all of the sky is invisibly glowing with Lyman-alpha emission from the early Universe .
Astronomers have long been accustomed to the sky looking wildly different at different wavelengths, but the extent of the observed Lyman-alpha emission was still surprising. “Realising that the whole sky glows in optical when observing the Lyman-alpha emission from distant clouds of hydrogen was a literally eye-opening surprise,” explained Kasper Borello Schmidt, a member of the team of astronomers behind this result.
“This is a great discovery!” added team member Themiya Nanayakkara. “Next time you look at the moonless night sky and see the stars, imagine the unseen glow of hydrogen: the first building block of the universe, illuminating the whole night sky.”
The HUDF region the team observed is an otherwise unremarkable area in the constellation of Fornax (the Furnace), which was famously mapped by the NASA/ESA Hubble Space Telescope in 2004, when Hubble spent more than 270 hours of precious observing time looking deeper than ever before into this region of space.
The HUDF observations revealed thousands of galaxies scattered across what appeared to be a dark patch of sky, giving us a humbling view of the scale of the Universe. Now, the outstanding capabilities of MUSE have allowed us to peer even deeper. The detection of Lyman-alpha emission in the HUDF is the first time astronomers have been able to see this faint emission from the gaseous envelopes of the earliest galaxies. This composite image shows the Lyman-alpha radiation in blue superimposed on the iconic HUDF image.
MUSE, the instrument behind these latest observations, is a state-of-the-art integral field spectrograph installed on Unit Telescope 4 of the VLT at ESO’s Paranal Observatory . When MUSE observes the sky, it sees the distribution of wavelengths in the light striking every pixel in its detector. Looking at the full spectrum of light from astronomical objects provides us with deep insights into the astrophysical processes occurring in the Universe .
"With these MUSE observations, we get a completely new view on the diffuse gas 'cocoons' that surround galaxies in the early Universe," commented Philipp Richter, another member of the team.
The international team of astronomers who made these observations have tentatively identified what is causing these distant clouds of hydrogen to emit Lyman-alpha, but the precise cause remains a mystery. However, as this faint omnipresent glow is thought to be ubiquitous in the night sky, future research is expected to shed light on its origin.
“In the future, we plan to make even more sensitive measurements,” concluded Lutz Wisotzki, leader of the team. “We want to find out the details of how these vast cosmic reservoirs of atomic hydrogen are distributed in space.”
Light travels astonishingly quickly, but at a finite speed, meaning that the light reaching Earth from extremely distant galaxies took a long time to travel, giving us a window to the past, when the Universe was much younger.
Unit Telescope 4 of the VLT, Yepun, hosts a suite of exceptional scientific instruments and technologically advanced systems, including the Adaptive Optics Facility, which was recently awarded the 2018 Paul F. Forman Team Engineering Excellence Award by the American Optical Society.
The Lyman-alpha radiation that MUSE observed originates from atomic electron transitions in hydrogen atoms which radiate light with a wavelength of around 122 nanometres. As such, this radiation is fully absorbed by the Earth’s atmosphere. Only red-shifted Lyman-alpha emission from extremely distant galaxies has a long enough wavelength to pass through Earth’s atmosphere unimpeded and be detected using ESO’s ground-based telescopes.
This research was presented in a paper titled “Nearly 100% of the sky is covered by Lyman-α emission around high redshift galaxies” which was published today in the journal Nature.
The team is composed of Lutz Wisotzki (Leibniz-Institut für Astrophysik Potsdam, Germany), Roland Bacon (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon, Université de Lyon, France), Jarle Brinchmann (Universiteit Leiden, the Netherlands; Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, Portugal), Sebastiano Cantalupo (ETH Zürich, Switzerland), Philipp Richter (Universität Potsdam, Germany), Joop Schaye (Universiteit Leiden, the Netherlands), Kasper B. Schmidt (Leibniz-Institut für Astrophysik Potsdam, Germany), Tanya Urrutia (Leibniz-Institut für Astrophysik Potsdam, Germany), Peter M. Weilbacher (Leibniz-Institut für Astrophysik Potsdam, Germany), Mohammad Akhlaghi (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon, Université de Lyon, France), Nicolas Bouché (Université de Toulouse, France), Thierry Contini (Université de Toulouse, France), Bruno Guiderdoni (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon, L’Université de Lyon, France), Edmund C. Herenz (Stockholms universitet, Sweden), Hanae Inami (L’Université de Lyon, France), Josephine Kerutt (Leibniz-Institut für Astrophysik Potsdam, Germany), Floriane Leclercq (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon,L’Université de Lyon, France), Raffaella A. Marino (ETH Zürich, Switzerland), Michael Maseda (Universiteit Leiden, the Netherlands), Ana Monreal-Ibero (Instituto Astrofísica de Canarias, Spain; Universidad de La Laguna, Spain), Themiya Nanayakkara (Universiteit Leiden, the Netherlands), Johan Richard (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon,L’Université de Lyon, France), Rikke Saust (Leibniz-Institut für Astrophysik Potsdam, Germany), Matthias Steinmetz (Leibniz-Institut für Astrophysik Potsdam, Germany), and Martin Wendt (Universität Potsdam, Germany).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a strategic partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.
Source: Nearly all the sky is covered by Lyman-α emission around high-redshift galaxies. L. Wisotzki, R. Bacon, J. Brinchmann, S. Cantalupo, P. Richter, J. Schaye, K. B. Schmidt, T. Urrutia, P. M. Weilbacher, M. Akhlaghi, N. Bouché, T. Contini, B. Guiderdoni, E. C. Herenz, H. Inami, J. Kerutt, F. Leclercq, R. A. Marino, M. Maseda, A. Monreal-Ibero, T. Nanayakkara, J. Richard, R. Saust, M. Steinmetz & M. Wendt. Nature (2018) | 0.880135 | 4.095163 |
A surprising superbubble
This colourful new view shows the star-forming region LHA 120-N44 in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way. This picture combines the view in visible light from the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile with images in infrared light and X-rays from orbiting satellite observatories.
At the centre of this very rich region of gas, dust and young stars lies the star cluster NGC 1929. Its massive stars produce intense radiation, expel matter at high speeds as stellar winds, and race through their short but brilliant lives to explode as supernovae. The winds and supernova shock waves have carved out a huge cavity, called a superbubble, in the surrounding gas.
Observations with NASA's Chandra X-ray Observatory (shown here in blue) reveal hot regions created by these winds and shocks, while infrared data from NASA's Spitzer Space Telescope (shown in red) outline where the dust and cooler gas are found. The visible-light view from the MPG/ESO 2.2-metre telescope (in yellow) completes the picture and shows the hot young stars themselves as well as the glowing clouds of gas and dust that surround them.
Combining these different views of this dramatic region has allowed astronomers to solve a mystery: why are N44, and similar superbubbles, giving off such strong X-rays? The answer seems to be that there are two extra sources of bright X-ray emission: supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls. This X-ray emission from the edge of the superbubble shows up clearly in the picture.
The designation of this object indicates that it was included in the Catalogue of H-alpha emission stars and nebulae in the Magellanic Clouds, compiled and published in 1956 by American astronomer–astronaut Karl Henize (1926–1993). The letter “N” indicates that it is a nebula. The object is often called simply N44.Credit:
Optical: ESO, X-ray: NASA/CXC/U.Mich./S.Oey, IR: NASA/JPL
About the Image
|Release date:||3 September 2012, 10:00|
|Size:||3600 x 2874 px|
About the Object
|Name:||LHA 120-N 44, NGC 1929|
|Type:||Local Universe : Nebula : Type : Star Formation|
|Distance:||150000 light years|
|Position (RA):||5 21 37.98|
|Position (Dec):||-67° 54' 42.75"|
|Field of view:||25.28 x 20.18 arcminutes|
|Orientation:||North is 0.1° right of vertical|
Colours & filters
|X-ray||Chandra X-ray Observatory|
|Optical||MPG/ESO 2.2-metre telescope|
|Infrared||Spitzer Space Telescope| | 0.887293 | 3.837177 |
Using data from the Dark Energy Survey (DES), researchers have found more than 300 trans-Neptunian objects (TNOs), minor planets located in the far reaches of the solar system, including more than 100 new discoveries.
Above: The Blanco Telescope dome at the Cerro Tololo Inter-American Observatory in Chile, where the Dark Energy Camera used for the recently completed Dark Energy Survey was housed. Credit Reidar Hahn, Fermilab
Published in The Astrophysical Journal Supplement Series, the study also describes a new approach for finding similar types of objects and could aid future searches for the hypothetical Planet Nine and other undiscovered planets. The work was led by graduate student Pedro Bernardinelli and professors Gary Bernstein and Masao Sako.
This updated catalog of trans-Neptunian objects and the methods used to find them could aid in future searches for undiscovered planets in the far reaches of the solar system.
The goal of DES, which completed six years of data collection in January, is to understand the nature of dark energy by collecting high-precision images of the southern sky. While DES wasn’t specifically designed with TNOs in mind, its breadth and depth of coverage made it particularly adept at finding new objects beyond Neptune. “The number of TNOs you can find depends on how much of the sky you look at and what’s the faintest thing you can find,” says Bernstein.
Because DES was designed to study galaxies and supernovas, the researchers had to develop a new way to track movement. Dedicated TNO surveys take measurements as frequently as every hour or two, which allows researchers to more easily track their movements. “Dedicated TNO surveys have a way of seeing the object move, and it’s easy to track them down,” says Bernardinelli. “One of the key things we did in this paper was figure out a way to recover those movements.”
Using the first four years of DES data, Bernardinelli started with a dataset of 7 billion “dots,” all of the possible objects detected by the software that were above the image’s background levels. He then removed any objects that were present on multiple nights—things like stars, galaxies, and supernova—to build a “transient” list of 22 million objects before commencing a massive game of “connect the dots,” looking for nearby pairs or triplets of detected objects to help determine where the object would appear on subsequent nights.
source University of Pennsylvania | 0.843322 | 3.879714 |
A long time ago in a galaxy half the universe away, a flood of high-energy gamma rays began its journey to Earth. When they arrived in April, NASA's Fermi Gamma-ray Space Telescope caught the outburst, which helped two ground-based gamma-ray observatories detect some of the highest-energy light ever seen from a galaxy so distant.
Astronomers had assumed that light at different energies came from regions at different distances from the black hole. Gamma rays, the highest-energy form of light, were thought to be produced closest in. But observations across the spectrum suggest that light at all wavelengths came from a single region located far away roughly five light-years from the black hole, which is greater than the distance between our sun and the nearest star.
The gamma rays came from a galaxy known as PKS 1441+25, a type of active galaxy called a blazar. Located toward the constellation Boötes, the galaxy is so far away its light takes 7.6 billion years to reach us. At its heart lies a monster black hole with a mass estimated at 70 million times the sun's and a surrounding disk of hot gas and dust. If placed at the center of our solar system, the black hole's event horizon -- the point beyond which nothing can escape -- would extend almost to the orbit of Mars.
As material in the disk falls toward the black hole, some of it forms dual particle jets that blast out of the disk in opposite directions at nearly the speed of light. Blazars are so bright in gamma rays because one jet points almost directly toward us, giving astronomers a view straight into the black hole's dynamic and poorly understood realm.
In April, PKS 1441+25 underwent a major eruption. Luigi Pacciani at the Italian National Institute for Astrophysics in Rome was leading a project to catch blazar flares in their earliest stages in collaboration with the Major Atmospheric Gamma-ray Imaging Cerenkov experiment (MAGIC), located on La Palma in the Canary Islands. Using public Fermi data, Pacciani discovered the outburst and immediately alerted the astronomical community. Fermi's Large Area Telescope revealed gamma rays up to 33 billion electron volts (GeV), reaching into the highest-energy part of the instrument's detection range. For comparison, visible light has energies between about 2 and 3 electron volts.
Following up on the Fermi alert, the MAGIC team turned to the blazar and detected gamma rays with energies ranging from 40 to 250 GeV. Because this galaxy is so far away, we didn't have a strong expectation of detecting gamma rays with energies this high. That’s because distance matters for very high-energy gamma rays -- they convert into particles when they collide with lower-energy light.
The visible and ultraviolet light from stars shining throughout the history of the universe forms a remnant glow called the extragalactic background light (EBL). For gamma rays, this is a cosmic gauntlet they must pass through to be detected at Earth. When a gamma ray encounters starlight, it transforms into an electron and a positron and is lost to astronomers. The farther away the blazar is, the less likely its highest-energy gamma rays will survive to be detected.
Following the MAGIC discovery, VERITAS also detected gamma rays with energies approaching 200 GeV. PKS 1441+25 is one of only two such distant sources for which gamma rays with energies above 100 GeV have been observed. Its dramatic flare provides a powerful glimpse into the intensity of the EBL from near-infrared to near-ultraviolet wavelengths and suggests that galaxy surveys have identified most of the sources responsible for it.
Black-hole-powered galaxies called blazars are the most common sources detected by NASA's Fermi Gamma-ray Space Telescope. As matter falls toward the supermassive black hole at the galaxy's center, some of it is accelerated outward at nearly the speed of light along jets pointed in opposite directions. When one of the jets happens to be aimed in the direction of Earth, as illustrated here, the galaxy appears especially bright and is classified as a blazar.
More distant blazars show a loss of higher-energy gamma rays thanks to the extragalactic background light (EBL), a "cosmic fog" of visible and ultraviolet starlight that permeates the universe. From studies of nearby blazars, scientists know how many gamma rays should be emitted at different energies. If a gamma ray on its way to Earth collides with lower-energy light in the EBL, it converts into a pair of particles and is lost to astronomers. As shown by the graphs at left in this illustration, the more distant the blazar, the fewer high-energy gamma rays we can detect. During the April 2015 outburst of PKS 1441+25, MAGIC and VERITAS saw rare gamma rays exceeding 100 GeV that managed to survive a journey of 7.6 billion light-years.
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 18.104.22.168.0 | 0.860138 | 4.130376 |
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Skywatchers all over the world jumped at the chance to view and photograph Friday's (Aug. 31) full moon, the last so-called "blue moon" until July 2015.
Friday's full moon was the second one to rise during the month of August, following the full moon of Aug. 1. This qualifies it as a blue moon, according to the popularly accepted (but incorrect) definition of the term.
"Blue moon" orginally referred to the third full moon in a season that has four full moons instead of the usual three. But in 1946, a writer for "Sky and Telescope" magazine erroneously reported the second-full-moon-in-month meaning, and the definition stuck.
Friday's blue moon rose on the same day that late astronaut Neil Armstrong was memorialized in Cincinnati. Armstrong, the first person to walk on the moon, died Aug. 25 following complications from a recent heart surgery.
Several skywatchers thought of the famous moonwalker when they looked up last night. [Gallery: August 2012 Blue Moon]
"From Michigan, we are thinking of you, Neil," wrote Dennis Daniels, who photographed the full disk of the moon Friday night.
Blue moons aren't actually blue, unless clouds of smoke or volcanic ash in Earth's atmosphere lend them that particular hue. Rather, they usually look like any other full moon in the sky. [Photos: The Blue Moon and Full Moons of 2012]
However, some sky photographers, such as Johan Clausen of Denmark, used photographic effects to get pictures of blue-looking moons.
Blue moons occur because lunar months and calendar months aren't perfectly synched up. It takes the moon 29.5 days to zip around our planet, during which time we see the satellite go through all of its phases. But Earth's months all have 30 or 31 days (except February), so once in a while two full moons get squeezed into a single month.
The moon looked markedly different from various locations around the world because of the different weather and atmospheric affects in each location.
An almost red moon was photographed over Evergreen Valley in Olympia, Wash., by Mary P. Bowman.
Before Friday night, the last blue moon occurred on Dec. 31, 2009. The next blue moon will come along on July 31, 2015.
The phrase "once in a blue moon" implies that the celestial phenomenon is incredibly rare, but it's really not. Blue moons occur on average once every 2.7 years, and sometimes much more frequently. In 1999, for example, two of them rose within three months. The next year that will see two blue moons is 2018.
If you snapped any good photos of Friday's full moon and would like them to be considered for a future story or gallery, please send them to SPACE.com assistant managing editor Clara Moskowitz at [email protected]. | 0.825169 | 3.344749 |
There was a time when the only way to learn about space was to have a look with your own eyes. Then came telescopes, which weren’t available to the masses. Soon we were flying in space ourselves thanks to Russians and Americans racing to the moon. Today we use the latest technology to look billions of years back in time and investigate how the universe began. Perhaps the best thing about modern technology is that we have awesome astronomy tools we can carry around with us.
Smartphones are great tools for learning or even doing astronomy. Firstly, they’re connected so you have access to the latest discoveries. But more importantly, the technology inside modern phones lets us learn astronomy in novel ways. There are apps that help you find sights in the night sky and there are apps that teach you more about the universe. Here are our top 5 apps for amateur astronomers.
Star Walk 2
Star Walk 2 does a lot of things that other apps do but does them better. The main feature of this app is that it uses the smartphone’s gyroscope, compass, and GPS to act as a window into the night sky. As you point your phone in certain directions, the app shows an augmented reality view of the night sky in that direction. This means you can spot an object with your own eyes then point the phone at it to find out what it is. There are tens of thousands of entries on different stars, galaxies, and nebulae that you can tap to learn more about and see 3D models or NASA imagery.
It’s not just constellations and stars. You can track planets, asteroids, and even satellites. One of the best features is that you can slide your finger to view the night sky on different nights. Seeing what the sky will look like in the future means you can plan ahead to see some amazing sights. Other apps do the same sort of thing with augmented reality but the user experience is better on Star Walk 2 and it looks beautiful.
There are a few weather apps designed for astronomers but Xasteria is our favourite because it’s free and has everything you need. It works anywhere in the world giving you a weather resolution of about 20 km. If you’re planning to do some amateur astronomy sometime soon, this app helps you pick the best time.
It shows when the sun and moon will set or rise and even highlights the twilight times that are best for viewing the moon. You can see the moon’s phase; the cloud cover in your area; how transparent the atmosphere will be; the predicted temperature and humdity; plus there are predictions for rain, snow, and even wind. You can change the view on the app for a detailed text-only mode that experienced astronomers might prefer or a graphical interface that makes it easier to see everything at a glance.
This might seem obvious but the NASA app is great for anyone fascinated by astronomy. It’s a great way to keep up-to-date with the latest NASA missions and discoveries. You can view news, schedules, and sighting opportunities for the current missions. You can see the latest images including the famous Astronomy Picture of the Day. The latest news is there to read and you can watch the latest videos from missions and press conferences when new discoveries are made. It’s also an educational app for anyone wanting to learn about astronomy. In the “Featured” section there are interactive entries on topics ranging from the formation of the solar system to gravity itself.
Moon Globe HD
Want to know more about our nearest neighbour? Viewing it through a telescope and need to know what features you’re actually looking at? There are a bunch of moon atlas apps available that do more or less the same thing but our favourite is Moon Globe HD on iOS. The images are really high-resolution and it looks amazing in 3D thanks to the laser altimetric data combined with the satellite imagery.
You can view the Moon as it appears from where you are in Telescope mode or you can zoom around the moon like you’re using Google Earth. There are words floating around the globe showing different geographical features or abandoned spacecraft. If you tap any of the words you can learn more about them.
Moon Globe HD is £0.79 on iOS. There’s also a free version using slightly lower resolution imagery. The options on Android aren’t as great but the best we’ve used is Moon Atlas 3D, which also allows you to learn more about hundreds of features on the lunar surface. It’s free on Android.
Wonders of the Universe
This app isn’t for use in astronomy as a tool. Instead it’s a beautiful educational experience. Based on the BBC TV show, Brian Cox talks you through the most amazing sights in space. There are articles to read, of course, but it’s the video and 3D content that brings the app to life. You can learn about planets, gravity, and black holes from lots of other apps but none have the same production quality as this app does. It’s like having an interactive episode of Cosmos in your pocket (sorry Cox, we still prefer Sagan). If you consider yourself an astronomy genius then this app might not be for you, but if you want an attractive experience learning new things then it’s a good way to go.
Main image © iStock/Thomas_EyeDesign | 0.823364 | 3.113248 |
In 2014 , the European Space Agency’s (ESA) Rosetta spacecraft made history when it rendezvoused with Comet 67P/Churyumov-Gerasimenko. This mission would be the first of its kind, where a spacecraft intercepted a comet, followed it as it orbited the Sun, and deployed a lander to its surface. For the next two years, the orbiter would study this comet in the hopes of revealing things about the history of the Solar System.
The Northern Lights have fascinated human beings for millennia. In fact, their existence has informed the mythology of many cultures, including the Inuit, Northern Cree, and ancient Norse. They were also a source of intense fascination for the ancient Greeks and Romans, and were seen as a sign from God by medieval Europeans.
Thanks to the birth of modern astronomy, we now know what causes both the Aurora Borealis and its southern sibling – Aurora Australis. Nevertheless, they remain the subject of intense fascination, scientific research, and are a major tourist draw. For those who live north of 60° latitude, this fantastic light show is also a regular occurrence.
Aurora Borealis (and Australis) is caused by interactions between energetic particles from the Sun and the Earth’s magnetic field. The invisible field lines of Earth’s magnetoshere travel from the Earth’s northern magnetic pole to its southern magnetic pole. When charged particles reach the magnetic field, they are deflected, creating a “bow shock” (so-named because of its apparent shape) around Earth.
However, Earth’s magnetic field is weaker at the poles, and some particles are therefore able to enter the Earth’s atmosphere and collide with gas particles in these regions. These collisions emit light that we perceive as wavy and dancing, and are generally a pale, yellowish-green in color.
The variations in color are due to the type of gas particles that are colliding. The common yellowish-green is produced by oxygen molecules located about 100 km (60 miles) above the Earth, whereas high-altitude oxygen – at heights of up to 320 km (200 miles) – produce all-red auroras. Meanwhile, interactions between charged particles and nitrogen will produces blue or purplish-red auroras.
The visibility of the northern (and southern) lights depends on a lot of factors, much like any other type of meteorological activity. Though they are generally visible in the far northern and southern regions of the globe, there have been instances in the past where the lights were visible as close to the equator as Mexico.
In places like Alaska, Norther Canada, Norway and Siberia, the northern lights are often seen every night of the week in the winter. Though they occur year-round, they are only visible when it is rather dark out. Hence why they are more discernible during the months where the nights are longer.
Because they depend on the solar wind, auroras are more plentiful during peak periods of activity in the Solar Cycle. This cycle takes places every 11 years, and is marked by the increase and decrease of sunspots on the sun’s surface. The greatest number of sunspots in any given solar cycle is designated as a “Solar Maximum“, whereas the lowest number is a “Solar Minimum.”
A Solar Maximum also accords with bright regions appearing in the Sun’s corona, which are rooted in the lower sunspots. Scientists track these active regions since they are often the origin of eruptions on the Sun, such as solar flares or coronal mass ejections.
The most recent solar minimum occurred in 2008. As of January 2010, the Sun’s surface began to increase in activity, which began with the release of a lower-intensity M-class flare. The Sun continued to get more active, culminating in a Solar Maximum by the summer of 2013.
Locations for Viewing:
The ideal places to view the Northern Lights are naturally located in geographical regions north of 60° latitude. These include northern Canada, Greenland, Iceland, Scandinavia, Alaska, and Northern Russia. Many organizations maintain websites dedicated to tracking optimal viewing conditions.
For instance, the Geophysical Institute of the University of Alaska Fairbanks maintains the Aurora Forecast. This site is regularly updated to let residents know when auroral activity is high, and how far south it will extend. Typically, residents who live in central or northern Alaska (from Fairbanks to Barrow) have a better chance than those living in the south (Anchorage to Juneau).
In Northern Canada, auroras are often spotted from the Yukon, the Northwest Territories, Nunavut, and Northern Quebec. However, they are sometimes seen from locations like Dawson Creek, BC; Fort McMurry, Alberta; northern Saskatchewan and the town of Moose Factory by James Bay, Ontario. For information, check out Canadian Geographic Magazine’s “Northern Lights Across Canada“.
The National Oceanic and Atmospheric Agency also provides 30 minute forecasts on auroras through their Space Weather Prediction Center. And then there’s Aurora Alert, an Android App that allows you to get regular updates on when and where an aurora will be visible in your region.
Understanding the scientific cause of auroras has not made them any less awe-inspiring or wondrous. Every year, countless people venture to locations where they can be seen. And for those serving aboard the ISS, they got the best seat in the house!
Speaking of which, be sure to check out this stunning NASA video which shows the Northern Lights being viewed from the ISS:
For more information, visit the THEMIS website – a NASA mission that is currently studying space weather in great detail. The Space Weather Center has information on the solar wind and how it causes aurorae.
Ever since Galileo first observed it through a telescope in 1610, Jupiter and its system of moons have fascinated humanity. And while many spacecraft have visited the system in the past forty years, the majority of these missions were flybys. With the exception of the Galileo space probe, the visits of these spacecraft to the Jupiter system were one of several intended objectives, taking place before they made their way deeper into the Solar System.
Having launched on August 5th, 2011, NASA’s Juno spacecraft has a different purpose in mind. Using a suite of scientific instruments, Juno will study Jupiter’s atmosphere, magnetic environment, weather patterns, and shed light on the history of its formation. In essence, it will be the first probe since the Galileo mission to orbit Jupiter, where it will spend the next two years sending information about the gas giant back to Earth.
If successful, Juno will prove to be the only other long-term mission to Jupiter. However, compared to Galileo – which spent seven years in orbit around the gas giant – Juno’s mission is planned to last for just two years. However, its improved suite of instruments are expected to provide a wealth of information in that time. And barring any mission extensions, its targeted impact on the surface of Jupiter will take place in February of 2018.
As part of the NASA’s New Frontiers program, the Juno mission is one of several medium-sized missions intended to explore the various bodies of the Solar System. It is currently one of three probes that NASA is operating, or in the process of building. The other two are the New Horizons probe (which flew by Pluto in 2015) and OSIRIS-REx, which is expected to fly to asteroid 101955 Bennu in 2020 and bring samples back to Earth.
During a 2003 decadal survey – titled “New Frontiers in the Solar System: An Integrated Exploration Strategy” – The National Research Council discussed destinations that would serve as the source for the first competition for the New Frontiers program. A Jupiter orbiter was identified as a scientific priority, which it was hoped would address several unanswered questions pertaining to the gas giant.
These included whether or not Jupiter had a central core (the research of which would help establish how the planet was formed), the water content of Jupiter’s atmosphere, how its weather systems can remain stable, and what the nature of the magnetic field and plasma surrounding Jupiter are. In 2005, Juno was selected for the New Frontiers program alongside New Horizons and OSIRIS-REx.
Though it was originally intended to launch in 2009, NASA budget restrictions forced a delay until August of 2011. The probe was named in honor of the Roman goddess Juno, the wife of Jupiter (the Roman equivalent of Zeus) who was able to peer through a veil of clouds that Jupiter drew around himself. The name was previously a backronym which stood for JUpiter Near-polar Orbiter as well.
The Juno mission was created for the specific purpose of studying Jupiter for the sake of learning more about the formation of the Solar System. For some time, astronomers have understood that Jupiter played an important role in the development Solar System. Like the other gas giants, it was assembled during the early stages, before our Sun had the chance to absorb or blow away the light gases in the huge cloud from which they were born.
As such, Jupiter’s composition could tell us much about the early Solar System. Similarly, the gas giants are believed to have played a major role in the process of planet formation because their huge masses allowed them to shape the orbits of other objects – planets, asteroids and comets – in their planetary systems.
However, for astronomers and planetary scientists, much still remains unknown about this massive gas giant. For instance, Jupiter’s interior structure and composition, as well as what drives its magnetic field, are still the subject of theory. Because Jupiter formed at the same time as the Sun, their chemical compositions should be similar, but research has shown that Jupiter has more heavy elements than our Sun (such as carbon and nitrogen).
In addition, there are some unanswered questions about when and where the planet formed. While it may have formed in its current orbit, some evidence suggests that it could have formed farther from the sun before migrating inward. All of these questions, it is hoped, are things the Juno mission will answer.
Having launched on August 5th, 2011, the Juno spacecraft spent the next five years in space, and will reach Jupiter on July 4th, 2018. Once in orbit, it will spend the next two years orbiting the planet a total of 37 times from pole to pole, using its scientific instruments to probe beneath the gas giant’s obscuring cloud cover.
The Juno spacecraft comes equipped with a scientific suite of 8 instruments that will allow it to study Jupiter’s atmosphere, magnetic and gravitational field, weather patterns, its internal structure, and its formational history. They include:
Gravity Science: Using radio waves and measuring them for Doppler effect, this instrument will measure the distribution of mass inside Jupiter to create a gravity map. Small variations in gravity along the orbital path of the probe will induce small changes in velocity. The principle investigators of this instrument are John Anderson of NASA’s Jet Propulsion Laboratory and Luciano Iess of the Sapienza University of Rome.
JunoCam: This visible light/telescope is the spacecraft’s only imaging device. Intended for public outreach and education, it will provide breathtaking pictures of Jupiter and the Solar System, but will operate for only seven orbits around Jupiter (due to the effect Jupiter’s radiation and magnetic field have on instruments). The PI for this instrument is Michael C. Malin, of Malin Space Science Systems
Jovian Auroral Distribution Experiment (JADE): Using three energetic particle detectors, the JADE instrument will measure the angular distribution, energy, and velocity vector of low energy ions and electrons in the auroras of Jupiter. The PI is David McComas of the Southwest Research Institute (SwRI).
Jovian Energetic Particle Detector Instrument (JEDI): Like JADE, JEDI will measure the angular distribution and the velocity vector of ions and electrons, but at high-energy and in the magnetosphere of Jupiter. The PI is Barry Mauk of NASA’s Applied Physics Laboratory.
Jovian Infrared Aural Mapper (JIRAM): Operating in the near-infrared, this spectrometer will be responsible for mapping the upper layers of Jupiter’s atmosphere. By measuring the heat that is radiated outward, it will determine how water-rich clouds can float beneath the surface. It will also be able to assess the distribution of methane, water vapor, ammonia and phosphine in Jupiter’s atmosphere. Angioletta Coradini of the Italian National Institute for Astrophysics is the PI on this instrument.
Magnetometer: This instrument will be used to map Jupiter’s magnetic field, determine the dynamics of the planet’s interior and determine the three-dimensional structure of the polar magnetosphere. Jack Connemey of NASA’s Goddard Space Flight Center is the instrument’s PI.
Microwave Radiometer: The MR instrument will perform measurements of the electromagnetic waves that pass through the Jovian atmosphere, measuring the abundance of water and ammonia in its deep layers. In so doing, it will obtain a temperature profile at various levels and determine how deep the atmospheric circulation of Jupiter is. The PI for this instrument is Mike Janssen of the JPL.
Radio and Plasma Wave Sensor (RPWS): This RPWS will measure the radio and plasma spectra in Jupiter’s auroral region. In the process, it will identify the regions of auroral currents that define the planet’s radio emissions and accelerate its auroral particles. William Kurth of the University of Iowa is the PI.
Ultraviolet Imaging Spectrograph (UVS): The UVS will record the wavelength, position and arrival time of detected ultraviolet photons, providing spectral images of the UV auroral emissions in the polar magnetosphere. G. Randall Gladstone of the SwRI is the PI.
In addition to its scientific suite, the Juno spacecraft also carries a commemorative plaque dedicated to Galileo Galilei. The plaque was provided by the Italian Space Agency and depicts a portrait of Galileo, as well as script that had been composed by Galileo himself on the occasion that he observed Jupiter’s four largest moons (known today as the Galilean Moons).
The text, written in Italian and transcribed from Galileo’s own handwriting, translates as:
“On the 11th it was in this formation, and the star closest to Jupiter was half the size than the other and very close to the other so that during the previous nights all of the three observed stars looked of the same dimension and among them equally afar; so that it is evident that around Jupiter there are three moving stars invisible till this time to everyone.”
The spacecraft also carries three Lego figurines representing Galileo, the Roman god Jupiter and his wife Juno. The figure of Juno holds a magnifying glass as a sign of her searching for the truth, Jupiter holds a lightning bolt, and the figure of Galileo Galilei holds his famous telescope. Lego made these figurines out of aluminum (instead of the usual plastic) to ensure they would survive the extreme conditions of space flight.
The Juno mission launched from Cape Canaveral Air Force Station on August 5th, 2011, atop an Atlas V rocket. After approximately 1 minute and 33 seconds, the five Solid Rocket Boosters (SRBs) reached burnout and then fell away. After 4 minutes and 26 seconds after liftoff, the Atlas V main engine cut off, followed 16 seconds later by the separation of the Centaur upper stage rocket.
After a burn that lasted for 6 minutes, the Centaur was put into its initial parking orbit. It coasted for approximately 30 minutes before its engine conducted a second firing which lasted for 9 minutes, putting the spacecraft on an Earth escape trajectory. About 54 minutes after launch, the spacecraft separated from the Centaur and began to extend its solar panels.
A year after launch, between August and September 2012, the Juno spacecraft successfully conducted two Deep Space Maneuvers designed to correct its trajectory. The first maneuver (DSM-1) occurred on August 30th, 2012, with the main engine firing for approximately 30 minutes and altering its velocity by about 388 m/s (1396.8 km/h; 867 mph).
The second maneuver (DSM-2), which had a similar duration and resulted in a similar velocity change, took place on September 14th. The two firings occurred when the probe was about 480 million km (298 million miles) from Earth, and altered the spacecraft’s speed and its Jupiter-bound trajectory, setting the stage for a gravity assist from its flyby of Earth.
Juno’s Earth flyby took place on October 9th, 2013, after the spacecraft completed one elliptical orbit around the Sun. During its closest approach, the probe was at an altitude of about 560 kilometers (348 miles). The Earth flyby boosted Juno’s velocity by 3,900 m/s (14162 km/h; 8,800 mph) and placed the spacecraft on its final flight path for Jupiter.
During the flyby, Juno’s Magnetic Field Investigation (MAG) instrument managed to capture some low-resolution images of the Earth and Moon. These images were taken while the Juno probe was about 966,000 km (600,000 mi) away from Earth – about three times the Earth-moon separation. They were later combined by technicians at NASA’s JPL to create the video shown above.
The Earth flyby was also used as a rehearsal by the Juno science team to test some of the spacecraft’s instruments and to practice certain procedures that will be used once the probe arrives at Jupiter.
Rendezvous With Jupiter:
The Juno spacecraft reached the Jupiter system and established polar orbit around the gas giant on July 4th, 2016. It’s orbit will be highly elliptical and will take it close to the poles – within 4,300 km (2,672 mi) – before reaching beyond the orbit of Callisto, the most distant of Jupiter’s large moons (at an average distance of 1,882,700 km or 1,169,855.5 mi).
This orbit will allow the spacecraft to avoid long-term contact with Jupiter’s radiation belts, while still allowing it to perform close-up surveys of Jupiter’s polar atmosphere, magnetosphere and gravitational field. The spacecraft will spend the next two years orbiting Jupiter a total of 37 times, with each orbit taking 14 days.
Already, the probe has performed measurements of Jupiter’s magnetic field. This began on June 24th when Juno crossed the bow shock just outside Jupiter’s magnetosphere, followed by it’s transit into the lower density of the Jovian magnetosphere on June 25. Having made the transition from an environment characterized by solar wind to one dominated by Jupiter’s magnetosphere, the ship’s instruments revealed some interesting information about the sudden change in particle density.
The probe entered its polar elliptical orbit on July 4th after completing a 35-minute-long firing of the main engine, known as Jupiter Orbital Insertion (or JOI). As the probe approached Jupiter from above its north pole, it was afforded a view of the Jovian system, which it took a final picture of before commencing JOI.
On July 10th, the Juno probe transmitted its first imagery from orbit after powering back up its suite of scientific instruments. The images were taken when the spacecraft was 4.3 million km (2.7 million mi) from Jupiter and on the outbound leg of its initial 53.5-day capture orbit. The color image shows atmospheric features on Jupiter, including the famous Great Red Spot, and three of the massive planet’s four largest moons – Io, Europa and Ganymede, from left to right in the image.
While the mission team had hoped to reduce Juno’s orbital period to 14 days, thus allowing for it to conduct a total of 37 perijoves before mission’s end. However, due to a malfunction with the probe’s helium valves, the firing was delayed. NASA has since announced that it will not conduct this engine firing, and that the probe will conduct a total perijoves in total before the end of its mission.
End of Mission:
The Juno mission is set to conclude in February of 2018, after completing 12 orbits of Jupiter. At this point, and barring any mission extensions, the probe will be de-orbited to burn up in Jupiter’s outer atmosphere. As with the Galileo spacecraft, this is meant be to avoid any possibility of impact and biological contamination with one of Jupiter’s moons.
The mission is managed by the JPL, and its principal investigator is Scott Bolton of the Southwest Research Institute. NASA’s Launch Services Program, located at the Kennedy Space Center in Florida, is responsible for managing launch services for the probe. The Juno mission is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Ala.
As of the writing of this article, the Juno mission is one day, four hours and fifty-five minutes away from its historic arrival with Jupiter. Check out NASA’s Juno mission page to get up-to-date information on the mission, and stay tuned to Universe Today for updates!
That might seem like a sensational headline worthy of a supermarket tabloid but, taken in context, it’s exactly what’s happening here!
The bright blue star at the center of this image is a B-type supergiant named Kappa Cassiopeiae, 4,000 light-years away. As stars in our galaxy go it’s pretty big — over 57 million kilometers wide, about 41 times the radius of the Sun. But its size isn’t what makes K Cas stand out — it’s the infrared-bright bow shock it’s creating as it speeds past its stellar neighbors at a breakneck 1,100 kilometers per second.
K Cas is what’s called a runway star. It’s traveling very fast in relation to the stars around it, possibly due to the supernova explosion of a previous nearby stellar neighbor or companion, or perhaps kicked into high gear during a close encounter with a massive object like a black hole.
As it speeds through the galaxy it creates a curved bow shock in front of it, like water rising up in front of the bow of a ship. This is the ionized glow of interstellar material compressed and heated by K Cas’ stellar wind. Although it looks like it surrounds the star pretty closely in the image above, the glowing shockwave is actually about 4 light-years out from K Cas… slightly less than the distance from the Sun to Proxima Centauri.
Although K Cas is visible to the naked eye, its bow shock isn’t. It’s only made apparent in infrared wavelengths, which NASA’s Spitzer Space Telescope is specifically designed to detect. Some other runaway stars have brighter bow shocks — like Zeta Ophiuchi at right — which can be seen in optical wavelengths (as long as they’re not obscured by dust, which Zeta Oph is.)
The bright wisps seen crossing K Cas’ bow shock may be magnetic filaments that run throughout the galaxy, made visible through interaction with the ionized gas. In fact bow shocks are of particular interest to astronomers precisely because they help reveal otherwise invisible features and allow deeper investigation into the chemical composition of stars and the regions of the galaxy they are traveling through. Like a speeding car on a dark country road, runaway stars’ bow shocks are — to scientists — like high-beam headlamps lighting up the space ahead.
Runaway stars are not to be confused with rogue stars, which, although also feel the need for speed, have been flung completely out of their home galaxies.
For years, scientists have thought a bow “shock” formed ahead of our solar system’s heliosphere as it moved through interstellar space – similar to the sonic boom made by a jet breaking the sound barrier. But new data from NASA’s Interstellar Boundary Explorer (IBEX) shows that our system and its heliosphere move through space too slowly to form a bow shock, and therefore does not exist. Instead there is a more gentle ‘wave.’
“While bow shocks certainly exist ahead of many other stars, we’re finding that our Sun’s interaction doesn’t reach the critical threshold to form a shock,” said Dr. David McComas, principal investigator of the IBEX mission, “so a wave is a more accurate depiction of what’s happening ahead of our heliosphere — much like the wave made by the bow of a boat as it glides through the water.”
From IBEX data, McComas and his team were able to make refinements in relative speed of our system, as well as finding more information about the local interstellar magnetic field strength. IBEX data have shown that the heliosphere actually moves through the local interstellar cloud at about 52,000 miles per hour, roughly 7,000 miles per hour slower than previously thought. That is slow enough to create more of a bow “wave” than a shock.
Another influence is the magnetic pressure in the interstellar medium. IBEX data, as well as earlier Voyager observations, show that the magnetic field is stronger in the interstellar medium requiring even faster speeds to produce a bow shock. Combined, both factors now point to the conclusion that a bow shock is highly unlikely.
The IBEX team combined its data with analytical calculations and modeling and simulations to determine the conditions necessary for creating a bow shock. Two independent global models — one from a group in Huntsville, Ala., and another from Moscow — correlated with the analytical findings.
Their paper was published today in the journal Science.
How does this new finding change our understanding of our heliosphere?
“It’s too early to say exactly what this new data means for our heliosphere,” McComas said. “Decades of research have explored scenarios that included a bow shock. That research now has to be redone using the latest data. Already, we know there are likely implications for how galactic cosmic rays propagate around and enter the solar system, which is relevant for human space travel.” | 0.911938 | 3.872238 |
An international team of researchers, including physicists from the University of Sussex, will create a 3D map of 10 million galaxies neighboring the Milky Way.
The “4MOST” project (4-metre Multi-Object Spectroscopic Telescope) is a partnership with eminent institutions in the United Kingdom and other countries. Initially, the researchers will add a new spectroscopic facility to the VISTA telescope at the European Southern Observatory in Chile. Then, they will have a watch over nearly 10 million galaxies and also millions of stars from the Milky Way.
Through the analysis of the spectral features of the light radiated from the center of each galaxy, the researchers can compute the speed at which each galaxy is traveling away from the Milky Way. Since the rate of expansion of the universe is uniform, a galaxy’s speed of movement is a precise proxy for its distance from the Milky Way. The team has located each of the galaxies and will develop a 3D map of a considerable volume of the universe.
This is one of the largest astrophysics projects of the University of Sussex. The Sussex team includes Dr Jon Loveday, Prof. Seb Oliver, Prof. Kathy Romer, and Dr Robert Smith, together with several students and other researchers.
We will be creating a 3D map of ten million galaxies in the sky, viewing them from a telescope in Chile. Not only is this an important and fascinating endeavour in its own right, but it may also help us to understand what the universe is made of. We know there are such things as ‘dark matter’ and ‘dark energy’ which are responsible for the way the universe formed and is expanding—but we still don’t know what they actually are.
Dr Jon Loveday, Reader in Astronomy, School of Mathematical and Physical Sciences, University of Sussex
Loveday, who leads the project for the University of Sussex, continued saying “Sussex scientists working on this project will be therefore trying to unlock some of the greatest mysteries of the universe.”
According to PhD student Dan Pryer who has already started working on the project, on the “extragalactic helpdesk,” “As a student it’s really exciting to be able to work on a project like this. I’ve also volunteered on the ‘extragalactic helpdesk’, which might sound like a call centre for aliens (!), but it actually sees me working with researchers around the world on surveys of galaxies in space.”
Pryer added, “I think it will allow me to develop my communication skills and also network within the scientific community which might help me in the future.”
We’re thrilled to have joined the highly prestigious 4MOST consortium in leadership roles, as this will help to keep the University of Sussex at the very forefront of the next generation of UK astronomy.
Professor Philip Harris, Head of the School of Mathematical and Physical Sciences, University of Sussex
Harris continued, “It is tremendously exciting, and amongst other things, it will give our staff and students the opportunity to help create a three-dimensional map of the universe with unparalleled resolution, shedding light on some of the greatest outstanding questions about our cosmic origins.”
The 4MOST project will start making observations in 2022 and will continue the same at least for five years. | 0.845989 | 3.436438 |
A surprising superbubble
This colourful new view shows the star-forming region LHA 120-N44 in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way. This picture combines the view in visible light from the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile with images in infrared light and X-rays from orbiting satellite observatories.
At the centre of this very rich region of gas, dust and young stars lies the star cluster NGC 1929. Its massive stars produce intense radiation, expel matter at high speeds as stellar winds, and race through their short but brilliant lives to explode as supernovae. The winds and supernova shock waves have carved out a huge cavity, called a superbubble, in the surrounding gas.
Observations with NASA's Chandra X-ray Observatory (shown here in blue) reveal hot regions created by these winds and shocks, while infrared data from NASA's Spitzer Space Telescope (shown in red) outline where the dust and cooler gas are found. The visible-light view from the MPG/ESO 2.2-metre telescope (in yellow) completes the picture and shows the hot young stars themselves as well as the glowing clouds of gas and dust that surround them.
Combining these different views of this dramatic region has allowed astronomers to solve a mystery: why are N44, and similar superbubbles, giving off such strong X-rays? The answer seems to be that there are two extra sources of bright X-ray emission: supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls. This X-ray emission from the edge of the superbubble shows up clearly in the picture.
The designation of this object indicates that it was included in the Catalogue of H-alpha emission stars and nebulae in the Magellanic Clouds, compiled and published in 1956 by American astronomer–astronaut Karl Henize (1926–1993). The letter “N” indicates that it is a nebula. The object is often called simply N44.Kilde:
Optical: ESO, X-ray: NASA/CXC/U.Mich./S.Oey, IR: NASA/JPL
|Publiseringsdato:||3. september 2012 10:00|
|Størrelse:||3600 x 2874 px|
|Navn:||LHA 120-N 44, NGC 1929|
|Type:||Local Universe : Nebula : Type : Star Formation|
|Position (RA):||5 21 37.98|
|Position (Dec):||-67° 54' 42.75"|
|Field of view:||25.28 x 20.18 arcminutes|
|Orientering:||Nord er 0.1° til høyre for vertikalen|
Farger og filtre
|Røntgen||Chandra X-ray Observatory|
|Optisk||MPG/ESO 2.2-metre telescope|
|Infrarødt||Spitzer Space Telescope| | 0.887293 | 3.834054 |
Detected Galaxies and Large Scale Structure in the Arecibo L-band Feed Array Zone of Avoidance Survey (ALFAZOA)Henning, P. A., Sanchez-Barrantes, M., McIntyre, T., Minchin, R. F., Momjian, E., Butcher, Z., Rosenberg, J. L., Schneider, S. E., Staveley-Smith, L., van Driel, W., Ramatsoku, M., Koribalski, B. & Spears, B., Jan-2017, In : American Astronomical Society Meeting. 229, 137.08.
Research output: Contribution to journal › Article › Academic › peer-review
While large, systematic redshift surveys of galaxies have been conducted for decades, lack of information behind the Milky Way (the Zone of Avoidance) contributes uncertainty to our picture of dynamics in the local universe. Controversy persists for the dipole calculated from galaxy and redshift surveys compared to the CMB. Depth in redshift space is an issue, as is incomplete sky mapping, even of supposed all sky redshifts surveys. For instance, the wide-angle 2MASS Redshift Survey retains a gap of 5-8 deg around the Galactic plane. Fortunately, there is no ZOA at 21cm, except for velocities occupied by the Galaxy. This long-wavelength spectral line passes unimpeded through dust, and is unaffected by stellar confusion. With immediate redshift determination, a 21-cm survey produces a 3-dimensional map of the distribution of obscured galaxies which contain HI. It traces large-scale structure right across the Galactic Plane, and identifies obscured mass overdensities relevant to flow-field studies.ALFAZOA is a blind HI survey for galaxies behind the Milky Way covering more than 1000 square degrees of the Arecibo sky. It proceeds in two phases: shallow (completed) and deep (ongoing). The shallow survey (rms ~5-7 mJy) mapped the region within Galactic longitude l = 30 - 75 deg, and latitude b = -10 to +10 deg, detecting several hundred galaxies to about 12,000 km/s, tracing large-scale structure across the plane. The deep survey (rms ~1 mJy), in both the inner (Galactic longitude 30 - 75 deg and latitude plus/minus 2 deg) and outer (longitude 175 - 207 deg and latitude = +1 to -2 deg) Galaxy is ongoing, with detections reaching to 18,000 km/s. Analysis of detections to date, and large-scale structure mapped, will be presented.
|Journal||American Astronomical Society Meeting|
|Publication status||Published - Jan-2017| | 0.815567 | 3.852213 |
NGC 1333 is located in the constellation Perseus and is a beautiful example of a reflection nebula embeded with an open star cluster. The star in the middle illuminates NGC 1333. NGC 1333 is the currently most active region of star formation in the Perseus molecular cloud. A number of very red structures indicate regions where new stars are forming. These regions of gas are catalogued as Herbig-Haro (HH) objects. These are a relatively brief cosmic light show, they only last a few thousand years. In fact, NGC 1333 contains hundreds of stars less than a million years old, most still hidden from optical telescopes by the pervasive stardust. Recent estimates for distance to NGC 1333 are at about 750 light years, making the the middle blue part measuring to about 3 light years.
I took this image over 11.5 hours. (24 luminance images of 20 minutes and 7 images of 10 minutes of each color). | 0.836503 | 3.109569 |
Scotland’s Sky in December, 2014
Jupiter outstanding as the Geminids meteors fly
December brings our longest nights of the year and what may be 2014’s richest meteor shower. Indeed, there is an argument for ranking December nights as the most spectacular of the year if only because Orion, and the sparkling constellations that attend him, stand at their highest near the meridian at midnight. Of the bright planets, Jupiter outshines every star and is well placed from mid-evening onwards, but the others are lurking shyly near the Sun and require a little more effort.
Jupiter is unmistakable from the moment it rises in the east-north-east some 35 minutes after our star map times. Improving in brightness from magnitude -2.3 to -2.5 this month, it climbs to pass high in the south and onwards into the south-west before dawn. We find it in Leo, to the right of the Sickle and less than 8° above-right of Regulus. It is here that it reaches a stationary point on the 9th before beginning a westerly motion which carries it back into Cancer just a day before its opposition in early February.
With its large disk and changing cloud-patterns, Jupiter is always an rewarding telescopic sight while the motions from side to side of its four main moons may be followed using nothing more than decent binoculars. When Jupiter lies near the Moon on the night of the 11th-12th, it is 717 million km distant and its globe appears 41 arcsec in diameter.
Orion stands clear of the horizon in the east-south-east at the map times. Its main stars, the blue-white supergiant Rigel at Orion’s knee and the contrasting red supergiant Betelgeuse at his shoulder, are among the ten brightest. the trio of stars between them form Orion’s Belt while hanging below the Belt is Orion’s Sword and the fuzzy glow of the Orion Nebula where new stars and planets are forming, albeit slowly, before our eyes.
A line upwards along the Belt extends to Aldebaran (close to the Moon on the 5th-6th) and onwards to the Pleiades or Seven Sisters star cluster. Carry the line downwards towards Sirius which rises one hour after our map times and is our brightest star after the Sun.
North and east (above-left) of Orion lies Gemini with its twins Castor and Pollux, while close to Castor (see chart) is the radiant point for the annual Geminids meteor shower. Bright medium-slow meteors streak in all parts of the sky between the 8th and 17th but all radiate away from this point as they follow parallel paths into the upper atmosphere. The radiant climbs from the north-north-east horizon at nightfall to pass high in the south at about 02:00. Meteor rates are expected to be highest during the 24 hours around 07:00 on the morning of the 14th when more than 80 Geminids per hour might be counted under ideal conditions. The Moon is much less obtrusive than during the Geminids last year.
The Square of Pegasus crosses the high meridian in the early evening and shifts to the south-west by our map times as Andromeda stretches up from its upper-left corner. High in the south are the two smaller constellations of Triangulum the Triangle and Aries the Ram. Aries’ main star, Hamal, is identical in brightness to Polaris, the Pole Star, but lies perhaps five times closer to us at 66 light years, It also appears to have a planet that is larger than Jupiter and takes 381 days to orbit at a distance slightly greater than that between the Earth and the Sun.
Aries also gives its name to the celestial counterpart of the Greenwich meridian. Longitudes in the sky are measured eastwards from the so-called First Point of Aries where the Sun crosses the sky’s equator at the spring or vernal equinox. When the Greek astronomer Hipparchus assigned the name more than two thousand years ago this point was located in Aries. However, the Earth wobbles on its axis over a period of 26,000 years with the result that the First Point of Aries has slipped more than 30° westwards against the stars and now lies to the south of the Square of Pegasus in the dim constellation of Pisces.
The Sun is furthest south in the sky at 23:03 GMT on the 21st, the moment of our winter solstice. Sunrise/sunset times for Edinburgh change from 08:19/15:44 on the 1st, to 08:43/15:40 on the 21st and 08:44/15:48 on the 31st. Nautical twilight persists for around 94 minutes at dawn and dusk. The Moon is full on the 6th, at last quarter on the 14th, new on the 22nd and at first quarter on the 28th.
Mars, the best of the planets after Jupiter, is the brightest object low in the south-south-west at nightfall and climbs a little higher from night to night as it slides northwards in relation to the Sun. It does, though, dim from magnitude 1.0 to 1.1 as it tracks eastwards through Capricornus. It sets at about 19:15 and stands left of the young earthlit Moon on Christmas Eve.
By mid-month, and provided we have a clear south-western horizon, we may be able to spot the brilliant (magnitude -3.9) evening star Venus just after sunset. At Hogmanay, Venus stands 6° high at sunset and sets itself 76 minutes later. Mercury slips around the Sun’s far side on the 8th and is destined to join Venus as an evening star in the New Year.
Saturn is emerging as a pre-dawn object low in the south-east where it shines at magnitude 0.5 as it tracks from Libra into Scorpius. Catch it 7° below-left of the waning Moon on the 19th.
This is a slightly-revised version of Alan’s article published in The Scotsman on November 28th 2014, with thanks to the newspaper for permission to republish here.
Posted on 28/11/2014, in Uncategorized and tagged 2014, Alan Pickup, Andromeda Galaxy, ASE, Astronomical Society of Edinburgh, Castor, First Point of Aries, Gemini, Geminids, Jupiter, Mars, Mercury, meteor shower, moon, Night Sky, orion, Pollux, Scotland, Square of Pegasus, The Scotsman. Bookmark the permalink. Leave a comment. | 0.845517 | 3.490351 |
compact high-velocity clouds (CHVCs)
abrhâ-ye hampak-e tondrow
Fr.: nuages compacts à grande vitesse
A population of relatively small (typically < 2°) → high-velocity clouds, which are spatially and kinematically isolated from the gas distribution in their environment. They are thought to be located in the → intergalactic medium of the → Local Group.
high-velocity clouds (HVCs)
Fr.: nuages à grande vitesse
A population of neutral or partly ionized gas clouds in the → Galactic halo which are seen as high-altitude structures in the atomic hydrogen 21 cm emission at high radial velocities (vLSR> 100 km/sec). They have substantial neutral column densities (> 1019 cm-2) and their metallicities range from 0.1 to about 1.0 times solar. The distances to the majority of them remain unknown. They may represent the continuing infall of matter onto the → Local Group. See also → compact high-velocity clouds. | 0.817317 | 3.037359 |
Thirty-five years ago this week, Voyager 1 was launched. Its mission—along with its sister craft, Voyager 2 (which, interestingly enough, was launched two weeks earlier)—was to explore the outer reaches of our solar system and the beginnings of interstellar space. Aboard each craft was a gold-plated audio disc containing sounds, images and messages from Earth, on the off-chance either was ever found by intelligent life from outside the Solar System.
In 1979 and 1980, Voyager 1 visited Jupiter and Saturn, respectively. While there, the craft provided the first high-resolution pictures and conducted other studies of the two planets and their respective satellites. This resulted in the first views of Jupiter’s ring system, discovery of volcanic activity on the moon Io, the first close analysis of the atmosphere of Titan, and detection of complex structures in Saturn’s rings.
A close flyby of Saturn’s moon, Titan, meant that Voyager wouldn’t get a close look at the other three outer planets (including, at the time, Pluto). After leaving Saturn, Voyager headed toward the far reaches of the Solar System, eventually to reach interstellar space.
In the 32 years since Saturn, Voyager has sent back data regarding the Solar System, much of it focused on finding the heliopause—the point where the force of the solar wind no longer is strong enough to push back against particles in the interstellar medium. Scientists believe that it crossed the “termination shock” (where the solar wind slows to subsonic speeds) in 2004. Late in 2010, it entered the heliosheath (the region just outside the termination shock), where there is no outward-flowing solar wind; it instead flows sideways, similar to two streams of water or other fluid hitting each other.
As of June 2012, Voyager has been reporting a substantial increase of interstellar charged particles, indicating that it has nearly reached the heliopause, and is getting ready to move into interstellar space, something that should happen within the next three years.
It’s really something to think that, soon, mankind will soon be taking its first direct measurements and exploration of the universe from outside the Sun’s influence. The amount of things we have the potential to learn from the Voyagers (and, of course, the New Frontiers probe launched in 2006 that will explore Pluto, then go on to the Kuiper belt, which lies outside the heliopause), is simply staggering.
Oh, not all things named Voyager get launched into space….there’s some fine earthbound items that do the name proud as well. | 0.843634 | 4.00885 |
On its way to sample an asteroid, the University of Arizona’s OSIRIS-REx mission will look for other, yet unobserved asteroids.
These asteroids are called Trojans, adopting the term from Greek mythology, because they can't be seen easily. Earth is one of six planets with known Trojan asteroids. They circle the sun in a constant orbit behind or in front of their companion planet. One Earth Trojan was discovered in 2010.
OSIRIS-Rex staff scientist Carl Hergenrother said the Earth’s likely companion space rocks are hard to detect because they appear close to the sun from Earth and cannot be observed from terrestrial telescopes.
"You are talking about looking at a part of the sky that is very close to the sun," he said.
Hergenrother said the OSIRIS-REx spacecraft’s path will provide a better vantage point because its cameras will not be staring into the sun to look for the objects.
In February, when the OSIRIS-REx spacecraft is headed back toward Earth after its orbit around the sun, scientists will turn on one of the cameras and spend 12 days scanning the universe for the objects, which are estimated to be 90 million miles from Earth.
The search will be a test for the mission to prepare to observe its target asteroid, Bennu, in 2018, Hergenrother said.
Listen to Carl Hergenrother talk about the search for Trojan asteroids: | 0.846919 | 3.19436 |
Stellar Shockwaves Shaped our Solar System
Stellar shockwaves shaped our solar system
Solar emissions rippling outward from our new-born Sun would have produced rings of material destined to form the planets. Credit: ESO/L. Calçada
The early years of our solar system were a turbulent time, and questions remain about its development. Dr. Tagir Abdylmyanov, Associate Professor from Kazan State Power Engineering University, has been researching shockwaves emitted from our very young sun, and has discovered that these would have caused the planets in our solar system to form at different times. Abdylmyanov will present his work at the European Planetary Science Congress in Madrid on Thursday 27th September.
Abdylmyanov has modeled the movements of particles in fluids and gases in the gas cloud from which our Sun accreted. His work suggests our new-born Sun emitted a series of shockwaves that rippled out into the remaining material. This created a series of debris rings around the Sun that accreted over millions of years into planets.
The research indicates that the first series of shockwaves during short but very rapid changes in solar activity would have created the proto-planetary rings for Uranus, Neptune, and dwarf planet Pluto. Jupiter, Saturn, and the asteroid belt would have come next during a series of less powerful shockwaves. Mercury, Venus, Earth, and Mars would have formed last, when the Sun was far calmer. This means that our own planet is one of the youngest in the solar system.
Solar shockwaves would have produced proto-planetary rings at different times, meaning the planets did not form simultaneously. Credit: ESO
“The planets formed in intervals — not altogether, as was previously thought,” Abdylmyanov explains. “It is difficult to say exactly how much time would have separated these groups, but the proto-planetary rings for Uranus, Neptune and Pluto would have likely formed very close to the Sun’s birth. 3 million years later and we would see the debris ring destined to form Saturn. Half a million years after this we would see something similar but for Jupiter. The asteroid belt would have begun to form about a million years after that, and another half a million years on we would see the very early stages of Mercury, Venus, Earth and Mars.”
Abdylmyanov hopes that this research will help us understand the development of planets around distant stars. “Studying the brightness of stars that are in the process of forming could give indications as to the intensity of stellar shockwaves. In this way we may be able to predict the location of planets around far-flung stars millions of years before they have formed.” | 0.855312 | 3.763696 |
Hubble Repair Details... Jan 23, 2007 22:18:36 GMT -6
Post by Chicago Astronomer Joe on Jan 23, 2007 22:18:36 GMT -6
Repairing The Hubble one last time
Time is running out for Hubble. The batteries are nearly depleted, its steer-controlling gyroscopes are shutting down one-by-one and the wear and tear from years in space is taking its toll. Without some serious TLC—tasks slated in the proposed service mission—Hubble might cease to function as a science instrument anytime in the next year or two. Eventually, without installation of a mechanism to bring the telescope back to Earth safely it would spin out of control.
Over a series of five spacewalks, astronauts will complete nuts-and-bolts work to keep Hubble alive.
They will also install two new instruments: the Wide Field Camera 3, which has visible, near-UV and near-infrared capabilities; and the Cosmic Origins Spectrograph (COS), which will use ultraviolet vision to study the formation and evolution of galaxies and ultimately how the universe’s structure has changed over time.
For Grunsfeld, the most significant and trickiest task will be to revive the Space Telescope Imaging Spectrograph (STIS), which conked out after a power failure in August 2003.
Installed on Hubble in February 1997, the STIS separates incoming light into its constituent colors, giving astronomers a chemical map of a distant object. Since deployed, STIS has been critical in the confirmation of black holes at the centers of galaxies, made the only discovery of an atmosphere around an exoplanet and helped confirm the age of the universe.
The repair job would typically be completed in a clean room, where mechanics would don sterile garbs and be equipped with tiny screwdrivers. The instrument is too bulky to even move it into the shuttle for repairs.
“The first problem is that the power supplies are deep in the instrument and behind covers," Grunsfeld said. "If we could take STIS out of Hubble and bring it to the shuttle it would be relatively straightforward, but you can’t do that."
The most optimal power supply for replacement is beneath a cover plate mounted to the instrument with more than 100 tiny screws and washers. “And that’s the kind of thing we have no capability to do with the current set of tools," he said. "So we’ve developed a new power tool— a mini power screwdriver—and ways of grabbing these screws so they don’t get loose inside the telescope, which could be disastrous."
Once this sweat-dripping operation is complete, the astronaut can change out the power-supply card—and the real fun begins.
“The card has 300 or so tiny gold pins on the back for replacement that we have to slide in. But you can’t really see it because we have on these huge bubble helmets. You can’t get your head in there with a tiny flashlight. So it’s going to be hard,” he said.
Grunsfeld and other service team members have practiced the repairs for hours and hours in a simulated environment. With a background in ballooning, Grunsfeld said he has experience reaching into instruments and completing repairs like this one without stereo vision.
I wish it were sooner, but ok... | 0.804235 | 3.051632 |
Tides are a fact of life for our readers on the ocean coasts and have been important to all coastal inhabitants who have become fishing and seafaring peoples. Their cause was a mystery until the application of Newton’s law of gravity almost 400 years ago. The oceanic tides are the manifestation of two independent “heartbeats” of our solar system (the sun and our moon) and display the force that keeps our universe together—yet they’re revealed to any patent observer standing by the seashore.
The sun is 400 times more distant than our moon, but it is 27 million times more massive, so its gravitational influence is still about 175 times greater. But our tides are caused by the “difference” in the gravitational attraction between one side of the Earth and the diametrically opposite side. The moon has the dominant effect because, compared with the sun’s attraction, it is much closer to us and its relative attraction to the far side of the Earth is much weaker than on the near side. The moon pulls on a litre of Earth-bound water with only 34 micro-newtons, but that is enough to raise tides that are over a metre in height.
The moon pulls on our Earth, but the water on the moon-facing hemisphere is pulled more strongly than the water on the far hemisphere. With respect to the centre of the Earth, water flows toward the moon on the near hemisphere and is pushed away on the far hemisphere. The results are the two tidal bulges on each side of the Earth. We experience the rise and fall of the tides as the Earth rotates “under” those tidal bulges.
All ocean ports have different tides, so these tables cannot be used for St. John’s, Nanaimo or Iqaluit. Landforms get in the way of a steady movement of water, but that rhythmic movement can cause exceptionally high tides, such as those in the Bay of Fundy. The amplitude of the tides is also caused by the volumes of water involved; therefore, inland lakes don’t show significant tidal activity. The tides on the Great Lakes are only a few centimetres, which is masked by water levels raised by wave action, as well as storms that cause the sloshing effect called “seiches,” which can be tens of centimetres high.
As the moon slowly orbits the Earth, it passes overhead about 50 minutes later each day, causing maximum tide to occur 50 minutes later. The heights of the tides are not always the same, because the combined pull of the moon and the sun change with the angle between them in the sky, which also manifests in the lunar phases.
The figure below shows the slowly evolving pattern of maximum and minimum tides that results from the gravitational pull of the moon and sun as they go in and out of phase each month (Halifax, 2016). On the left is the height of the tides in metres. The swing between high and low tides occurs about twice a day. The month-long wave-like variations are due to the sun and moon’s gravitational forces drifting in and out of phase. We have been told that these patterns are lost in our many pages of tide tables, so we thought we should put them into a more revealing context.
Halifax, 2016. Even though the moon is 400,000 km and the sun is 150 million km away from us, tides demonstrate the physical impact of these celestial bodies on the Earth. We cannot reach out to touch them, but they can touch us. | 0.823737 | 3.743346 |
Are you looking for it, too? It's that frustrating time of year again. As the Northern Hemisphere rolls away from winter we eagerly await signs of spring. For many, spring comes with returning robins bobbing along the ground in a spirited hunt for lunch. For others it's spring flowers putting in a first appearance. But the most reliable sign of spring is not of the Earth, but of the sky. It is the stars of Leo.
Leo the lion is a prominent spring constellation. When I see Leo riding high in the southern sky before midnight (figure 1), I know that Earth has not stalled in its yearly orbit and we are not stuck in perpetual winter.
At night, we face away from the Sun. Our nighttime view changes through the year. As Earth orbits around the Sun our view sweeps through the yearly cycle of seasonal constellations. The solar system is tilted compared to the plane of the galaxy (figure 2), and this also affects what we see as we look out into the stars. During spring nights we face away from the rich star fields of our galaxy. The Milky Way hugs the western horizon and our view is up and out of the galaxy (figure 3). This gives us a clear view into the deeps of intergalactic space.
In spring, the rest of the universe is on display. There is little interference from the Milky Way's intervening clouds of gas, dust and stars. Millions of external galaxies glow faintly in the blackness of space, beckoning telescopes to reveal their splendor. Astronomers answer the call of the galaxies each spring with eager enthusiasm. Leo and its neighboring constellations are rich territory for observers wanting to soak up photons from hundreds of millions of light years away. Such intergalactic communion is an experience like none other.
We all have our favorite signs of spring. This year spring arrived officially on March 21 at seven minutes after midnight Universal Time. For sky gazers, spring is synonymous with the arrival of Leo and a sky blooming with galaxies. The celestial lion is the surest signal that terrestrial blossoms will soon follow. | 0.850375 | 3.29265 |
Tonight – July 30, 2016 – the innermost planet Mercury and bright star Regulus in the constellation Leo the Lion present the year’s closest conjunction of a planet and bright star. Their fleeting rendezvous takes place in the glare of evening twilight, unfortunately. Both worlds are bright, but won’t appear bright against a bright twilight background.
If you’re up for the challenge, bring along binoculars to see if you can catch their furtive meeting in the twilight glare.
Find an unobstructed horizon in the direction of setting sun, and in addition, hope for a crystal-clear sky. Some 30 to 40 minutes after sunset, look for the very bright planets Venus and Jupiter to pop out into the western sky. Venus, though the brighter of these two dazzling worlds, might be the harder to spot, because it also sits low in the sky after sunset and near the sunset glare. Once again, binoculars may come in handy.
Seek for the two embracing worlds – Mercury and Regulus – in between Venus and Jupiter, though they’ll be much closer to Venus on the sky’s dome.
The coy couple will slip beneath the horizon about an hour after sunset – or before it gets good and dark – roughly 15 minutes after Venus sinks below the horizon.
Mercury is actually several times brighter than Regulus, the constellation Leo the Lion’s brightest star. So if you see only one starlike object in your binocular field, it’s probably Mercury, the innermost planet of the solar system.
If you miss Venus, Mercury and Regulus, there is still a wonderful consolation prize awaiting you at dusk or nightfall. Jupiter should be easy pickings in the western sky, given that this dazzling world will stay out till after dark.
Also, as darkness falls, look in the south to southwest sky for the planets Mars and Saturn (or look high overhead if you live in the Southern Hemisphere).
If you do spot Mercury and Venus, you may well have the opportunity to view all five bright planets at the same time. These are the planets known and observed by our ancestors since time immemorial: Mercury, Venus, Mars, Jupiter and Saturn.
They’re all in the evening sky, now.
Bottom line: Planet Mercury and star Regulus appear in 2016’s closest conjunction of a planet and a bright star on July 30. Too bad they’re so near the sunset glare.
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. | 0.85969 | 3.229034 |
July 7, 2015 – With just one year remaining in a five-year trek to Jupiter, the team of NASA’s Juno mission is hard at work preparing for the spacecraft’s expedition to the solar system’s largest planet. The mission aims to reveal the story of Jupiter’s formation and details of its interior structure. Data from Juno will provide insights about our solar system’s beginnings, and what we learn from the mission will also enrich scientists’ understanding of giant planets around other stars.
Juno is scheduled to arrive at Jupiter on July 4, 2016 (Pacific Daylight Time). Once it settles into orbit, the spacecraft will brave the hazards of Jupiter’s intense radiation when it repeatedly approaches within a few thousand miles, or kilometers, of the cloud tops to collect its data.
Juno is the first mission dedicated to the study of a giant planet’s interior, which it will do by mapping the planet’s magnetic and gravity fields. The mission will also map the abundance of water vapor in the planet’s atmosphere, providing the key to understanding which of several theories about the planet’s formation is likely the correct one. In addition, Juno will travel through the previously unexplored region above the planet’s poles, collecting the first images from there, along with data about electromagnetic forces and high-energy particles in the environment.
Although other spacecraft have previously visited Jupiter, the space around the planet is full of unknowns, especially the regions above the poles. With these challenges in mind, the Juno team has been busy fine-tuning their flight plan.
“We’re already more than 90 percent of the way to Jupiter, in terms of total distance traveled,” said Scott Bolton, Juno principal investigator at Southwest Research Institute, San Antonio. “With a year to go, we’re looking carefully at our plans to make sure we’re ready to make the most of our time once we arrive.”
Following a detailed analysis by the Juno team, NASA recently approved changes to the mission’s flight plan at Jupiter. Instead of taking 11 days to orbit the planet, Juno will now complete one revolution every 14 days. The difference in orbit period will be accomplished by having Juno execute a slightly shorter engine burn than originally planned.
The revised cadence will allow Juno to build maps of the planet’s magnetic and gravity fields in a way that will provide a global look at the planet earlier in the mission than the original plan. Over successive orbits, Juno will build a virtual web around Jupiter, making its gravity and magnetic field maps as it passes over different longitudes from north to south. The original plan would have required 15 orbits to map these forces globally, with 15 more orbits filling in gaps to make the map complete. In the revised plan, Juno will get very basic mapping coverage in just eight orbits. A new level of detail will be added with each successive doubling of the number, at 16 and 32 orbits.
The slightly longer orbit also will provide a few extra days between close approaches to the planet for the team to react to unexpected conditions the spacecraft might experience in the complex environment very close to Jupiter.
“We have models that tell us what to expect, but the fact is that Juno is going to be immersed in a strong and variable magnetic field and hazardous radiation, and it will get closer to the planet than any previous orbiting spacecraft,” said Bolton. “Juno’s experience could be different than what our models predict — that’s part of what makes space exploration so exciting.”
The revised plan lengthens Juno’s mission at Jupiter to 20 months instead of the original 15, and the spacecraft will now complete 32 orbits instead of 30. But the extra time doesn’t represent bonus science for the mission — rather, it’s an effect of the longer orbital period and the change in the way Juno builds its web around Jupiter. Basically, it will take Juno a bit longer to collect the full data set the mission is after, but it will get a low-resolution version of its final products earlier in the mission than originally planned.
NASA also recently approved a change to the spacecraft’s initial orbit after Jupiter arrival, called the capture orbit. The revised plan splits the originally planned, 107-day-long capture orbit into two. The new approach will provide the Juno team a sneak preview of their science activities, affording them an opportunity to test the spacecraft’s science instruments during a close approach to Jupiter before beginning the actual science phase of the mission. The original scenario called for an engine burn to ease Juno into Jupiter orbit, followed by a second burn 107 days later, putting the spacecraft into an 11-day science orbit. In the updated mission design, the orbit-insertion burn is followed 53.5 days later by a practice run at Jupiter with science instruments turned on, followed by another 53.5-day orbit before the final engine burn that places Juno into its new, 14-day science orbit.
In addition to myriad preparations being made on the engineering side, Juno’s science team is also busy preparing to collect valuable data about the giant planet’s inner workings. One piece of this science groundwork is a collection of images and spectra being obtained by powerful ground-based telescopes and NASA’s Hubble Space Telescope (spectra are like chemical fingerprints of gases in the atmosphere). These data are intended to provide big-picture context for Juno’s up-close observations of Jupiter, which is important for interpreting what the spacecraft’s instruments will see.
With the countdown clock ticking — this time, not toward launch, but toward arrival at their destination — the Juno team is acutely aware of how quickly they’re sneaking up on the giant planet. And their excitement is building.
“It’s been a busy cruise, but the journey has provided our team with valuable experience flying the spacecraft and enhanced our confidence in Juno’s design,” said Rick Nybakken, Juno project manager at NASA’s Jet Propulsion Laboratory, Pasadena, California. “Now it’s time to gear up for Jupiter.”
Juno is the second mission chosen as part of NASA’s New Frontiers program of frequent, medium-class spacecraft missions that address high-priority exploration initiatives in the solar system. NASA’s New Horizons mission, which will soon encounter Pluto, is the first New Frontiers mission; OSIRIS-REx is next in the lineup, slated to launch in 2016.
NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. The New Frontiers Program is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Lockheed Martin Space Systems, Denver, built the spacecraft. JPL is a division of the California Institute of Technology in Pasadena. | 0.826134 | 3.800233 |
For centuries, astronomers have speculated that the solar process incorporates
undiscovered planets that orbit in the distant, darkish reaches of the sun’s
realm. From time to time, they have noticed the gravitational consequences of
not known bodies, forcing them to appear for the perpetrator. Equally Neptune and Pluto arrived to gentle in this way.
Black Hole Puzzle
Now, astronomers have a similar puzzle on their arms. For some time, they have been accumulating proof that a substantial planet need to be orbiting the sun at a distance of all over five hundred astronomical models, or 70 billion kilometers.
The proof arrives from the orbits of icy bodies in the Kuiper Belt further than Neptune. These objects seem to be to cluster alongside one another in strategies that can only be defined if they have been remaining “herded” by some substantial item.
This item — Earth 9, as it is dubbed — need to be between five and ten occasions the mass of Earth, but so much absent that it is challenging to see from Earth, despite quite a few ongoing lookups.
But there is a further rationale why Earth 9 may well be challenging to see: mainly because it is not a planet at all. Instead, astronomers say just one probability is that it may well be a primordial black hole, remaining above from the Major Bang but captured by the sun.
Despite the fact that between five and ten occasions extra substantial than Earth, this black hole would by little — about five centimeters across. For that reason, it is practically unattainable to spot with a telescope. There is a little probability that these a black hole may well be observable by way of its conversation with darkish make a difference, but that is by no implies certain. So astronomers are scratching their heads to arrive up with a further way of acquiring it.
Currently, they have an answer, thanks to the function of Ed Witten, a physicist at the Institute for Innovative Research in Princeton, New Jersey. Witten’s thought is to appear for the gravitational forces this black hole need to exert on something that passes nearby. So he proposes sending a fleet of nanospacecraft in its direction and then searching for any unpredicted deviations from the envisioned trajectory.
“If further review of the Kuiper Belt strengthens the scenario for existence of Earth 9, but discovery by way of telescopic lookups or a darkish make a difference annihilation signal does not comply with, then a direct lookup by a fleet of miniature spacecraft may grow to be persuasive,” he suggests.
Witten is not the very first to imagine the opportunity of nanospacecraft. Many scientists and visionaries have studied the thought of utilizing impressive ground-based mostly laser beams to propel little chip-based mostly spacecraft towards the stars.
The significant gain is that these spacecraft needn’t carry their personal gasoline, but would alternatively sit on the idea of laser beam generated on Earth. This laser beam could accelerate them consistently for extensive periods of time, allowing them to arrive at big velocities of most likely 1 or two p.c the speed of gentle.
“To lookup for Earth 9, just one would like spacecraft velocities of (at the very least) hundreds of kilometers per second,” suggests Witten, including that these speeds would let a spacecraft to travel five hundred AU on a ten-12 months timescale.
What’s extra, it is attainable to start nanospacecraft by their hundreds, probably
thousands, towards Earth 9. That is important, mainly because Witten estimates that these a spacecraft would need to arrive within a several dozen AU of a black hole for any changes in its trajectory to be observable. And mainly because astronomers never still know particularly where by Earth 9 may well be, the only solution is this scattergun tactic.
This sort of a mission would be a substantial challenge. Witten factors to prior and ongoing jobs to acquire and start nanospacecraft. The finest regarded is Breakthrough Starshot, a $100 million initiative to acquire and examination the technology able of sending laser-propelled nanospacecraft to nearby star techniques. The project’s intention is to “lay the foundations for a flyby mission to Alpha Centauri within a technology.”
A mission to the outer edges of the solar process may well be a helpful technology demonstrator. Calculations by the British rocket scientist Kevin Parkin propose that the value of these a mission would be of the identical get as the $1 billion missions that NASA has undertaken quite a few occasions.
Yet, practically each element of these a mission would be a challenge, from the improvement of a laser able of providing propulsion to the design and style of a chip able of relaying situation info back to Earth. That will require the spacecraft to carry a large-precision onboard clock within a payload measured in grams. “Sufficiently accurate timekeeping in a miniature spacecraft may be the major impediment to this task,” suggests Witten.
But there is surely enthusiasm to consider. The discovery of a black hole orbiting the sun would be quite a prize for whoever undertook these a endeavor. Certainly, it may be the past prospect to find out a substantial new system orbiting our star.
Ref: Hunting for a Black Hole in the Outer Photo voltaic Method arxiv.org/abdominal muscles/2004.14192 | 0.85529 | 3.867715 |
Some stars are lonely behemoths, with no surrounding planets or asteroids, while others sport a skirt of attendant planetary bodies.
New research published this week in The Astrophysical Journal Letters explains why the composition of the stars often indicates whether their light shines into deep space, or whether a small fraction shines onto orbiting planets.
When a star forms, collapsing from a dense cloud into a luminous ball, it and the disk of dust and gas orbiting it reflect the composition of that original cloud and the elements within it. While some clouds are poor in heavier elements, many have a wealth of these elements. These are the dirty stars that are good solar system hosts.
"When you observe stars, the ones with more heavy elements have more planets," says co-author Mordecai-Mark Mac Low, Curator of Astrophysics at the American Museum of Natural History. "In other words, what's in the disk reflects what's in the star. This is a common sense result." Observation of distant solar systems shows that exoplanets, or planets that orbit stars other than the Sun, are much more abundant around stars that have a greater abundance of elements heavier than helium, like iron and oxygen. These elements are the ones that can turn into rocks or ice.
The new simulations by Mac Low and his colleagues Anders Johansen (Leiden Observatory in the Netherlands) and Andrew Youdin (Canadian Institute of Theoretical Astrophysics at the University of Toronto) compute just how planets and other bodies form as pebbles clump into mini-planets referred to as planetesimals. Their current work hinges on their previously published research (in Nature in 2007) that explains why rocks orbiting a star within the more slowly-revolving gas disk are not quickly dragged into the star itself because of the headwinds they feel. Like bicyclists drafting behind the leader in the Tour de France, the rocks draft behind each other, so that in orbits with more rocks, they feel less drag and drift towards the star more slowly. Rocks orbiting further out drift into those orbits, until there are so many that gravity can form them into mini-planets. This concentration of orbiting rocks in a gas disk is called a "streaming instability" and is the theoretical work of co-author Youdin. "It's a run-away process. When a small group of rocks distorts the flow of gas, many others rush to line up like lazy cyclists and matter accumulates very quickly," he says.
The team was able to build this mechanism—drag leading to clumping—into a three-dimensional simulation of gas and solid rocks orbiting a star. Their results show that when pebbles, made of heavy elements, constitute less than one percent of the gas mass, clumping is weak. But if the fraction of pebbles is increased slightly, the clumping increases dramatically and quickly results in the accretion of sufficient material to make larger-scale planetesimals. These mini-planets work as planetary building blocks, merging over millions of years to form planets. In short, clumping of pebbles, when the fraction of solids in the gas is high enough, is the recipe for mini-planet formation, a crucial intermediate step in forming planets.
"There is an extremely steep transition from not being able to make planets at all to easily making planets, by increasing the abundance of heavy elements just a little," says lead author Johansen. "The probability of having planets almost explodes."
Youdin adds that "There's an inherent advantage in being born rich, in terms of solid rocks. But less advantaged systems, like our own Solar System, can still make planets if they work to marshal their resources and hang onto their solids as the gas evaporates away. So the Sun is middle-class, rather than rich." The Sun's abundance of heavy elements suggests its protoplanetary disk (the disk from which the Solar System formed) had close to the critical ratio of pebbles to gas; if the abundance of heavy elements had been slightly less, planetesimals and planets would have been far less likely to form, and we would not be here to study the question.
The results of this paper will be presented on October 8, 2009 at a meeting of the Division of Planetary Sciences of the American Astronomical Society in Puerto Rico. Computer simulations were performed on the Huygens cluster in Amsterdam and the PIA cluster of the Max Planck Institute for Astronomy. Additional funding came from the NASA Origins of the Solar Systems Program and the NSF Cyberenabeled Discovery Initiative.
Kristin Elise Phillips | EurekAlert!
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The world watched avidly earlier this year when NASA spacecraft New Horizons made a historic encounter. It flew past an object called 2014 MU69 – AKA Ultima Thule – the farthest named single object in the Solar System.
We know what it looks like. We know it’s a bit of a weirdo. But now scientists have crunched the numbers, analysed the data, and detailed those first observations in new scientific research.
MU69 is an almost incomprehensibly long way away – an average distance from the Sun of 6.7 billion kilometres (4.1 billion miles), with an orbital period of 293 years. New Horizons launched in January 2006, which means it took 13 years to get all the way to where MU69 hangs out in the Kuiper Belt.
But that position is important. MU69 isn’t just some weird emo loner skulking about in the cold and dark all by itself.
At that distance from the Sun, it’s thought that objects with a stable orbit like MU69 have remained pretty much undisturbed and unchanged since the formation of the Solar System. Not much solar radiation penetrates those far reaches, so objects are less affected by heat.
MU69 is like a time capsule that can tell us about the conditions in the Solar System around the time that Earth was still forming.
But it’s also really weird – two objects stuck together a bit like a snowman, but also a bit flattened, like pancakes.
“We’ve never seen anything like this anywhere in the Solar System,” New Horizons principal investigator Alan Stern of the Southwest Research Institute said earlier this year.
The data sent back home by New Horizons in the weeks following the flyby reveals that the object is consistent with our ideas of planetary formation.
It’s thought that as a protoplanetary disc of dust and gas orbits a newborn star, pieces of matter start to clump, held together by electrostatic forces. As they grow larger and larger, their gravity grows stronger too, which in turn pulls in more and more pieces.
MU69 is in the Kuiper Belt, a torus-shaped ring of objects in the outer Solar System, a remnant of its protoplanetary disc. The researchers believe that it was once two chunks of rock orbiting each other until the two pieces were brought together in a gentle collision.
“This fits with general ideas of the beginning of our Solar System,” said New Horizons investigator William McKinnon of Washington University in St. Louis.
“Much of the orbital momentum of the Ultima Thule binary must have been drained away for them to come together like this. But we don’t know yet what processes were most important in making that happen.”
What they have ascertained is that MU69’s spin and orbit have likely been unchanged since that merger. Impact cratering on the surface of the object is minimal, and, although individual geological features have been identified, its colour and composition are mostly uniform.
Nor does it have any moons, rings, a transient atmosphere, nor gas emission or dust – nothing that indicates relatively recent perturbation. It’s a very peaceful object. This means it has probably come into contact with very few other objects since the merger, if any.
It is also, as early imaging suggested, very red, brighter in the near-infrared spectrum than the visible. It’s still unknown what gives it that red colour – it could be organic macromolecules produced by the breakdown of simpler ones via irradiation, or it could be caused by silicates weathered by space, although there’s no direct evidence of silicates on MU69.
Although it’s pretty much the same colour all over, there are some very subtle variations that the team is yet to figure out.
This paper is just based on the first 10 percent of the data New Horizons collected, and it’s expected that it will finish sending the rest sometime in 2020.
Let’s hope it contains some answers – and maybe some even more interesting questions.
The research has been published in Science. | 0.830512 | 3.892199 |
If you were trying to identify the kind of star that should produce Earth-like planets, you’d think the task would be straightforward. Our theories of planet formation focus on a circumstellar disk around a young star out of which planets form, and we’ve already gathered evidence that gas giant worlds are more likely to form around stars that are rich in iron. Since rocky planets are rich in iron and silicon, doesn’t this mean their stars should be rich in metallic elements?
New work out of the Carnegie Institution for Science suggests that the answer is surprisingly complex. As presented by Johanna Teske at the Extreme Solar Systems III meeting in Hawaii, the team’s work has revealed that smaller planets do not require high iron content in their parent stars. In fact, looking at the abundance of 19 different elements in seven stars orbited by at least one rocky planet (these are drawn from the Kepler catalog), the team finds that rocky worlds do not preferentially form around stars rich in metallic elements like iron and silicon.
The data were taken as part of the Kepler Follow-up Observing Program and supplemented by independent observations using the 10-meter Keck telescope and the HIRES echelle spectrometer. From the paper:
The metallicities of the seven stars range from [Fe/H] = −0.30 to +0.15, further demonstrating that small planets form around stars with both low and high metallicities… The abundances of 15 elements are compared to those of a Galactic disk population that includes stars with and without known planets. The abundances of the Kepler planet host stars fall along the Galactic trends, suggesting that stars with small planets have compositions that are typical of the Galactic disk.
Stars with small planets, then, are nothing exceptional in terms of their metallicity. This implies they are common throughout the galaxy. The paper goes on:
Moreover, comparing the abundance distributions of the Kepler planet host stars to a sample of stars with no detected planets, a sample of Neptune- and super-Earth-size planet hosts, and a sample of Jupiter-type giant planet hosts, reveals that the former three – Kepler host stars, stars without known planets, and the Neptune and super-Earth-size planet hosts – may have similar compositions, whereas the Kepler host stars appear to have compositions that are less enhanced than those of Jupiter-type planet hosts.
Image: This figure from the paper shows the abundance of different elements in stars versus their abundances of iron. In each square, you can see a plot of the abundance of one element (represented by [x/Fe]) against the abundance of iron (represented by [Fe/H]). Each red dot, black square, or blue X represents a star. The red dots are the small planet-hosting stars studied in this new work. You can see how they do not stand out from the rest of the stars, which were studied in other publications, some of which host planets and some of which have no known planets. The green dashed lines show these values for our Sun. Credit: NASA Ames/JPL-Caltech/Tim Pyle.
Small, rocky planets appear to form around stars with a wide range of elements, whereas gas giants are more likely around stars rich in iron. Teske adds in this Carnegie news release that the results are exciting “…because they mean that small planets are very common and chemically diverse.” What we don’t yet know is whether the planet formation process depletes stars of some of the elements that become concentrated in the planets. None of the seven stars the team studied show a depletion signature, but if subsequent work does uncover such a trend, then looking for stars with specific chemical depletions could be a useful planet-hunting tool.
Does the architecture of a solar system play a role in these trends? With the exception of two planets, the planets of all the stars investigated have semimajor axes smaller than Mercury’s. As the paper notes, the small sample size here limits the statistical significance of the results, so the obvious next step is generating a larger sample of stars with small planets and performing abundance analyses on this set. We’re fortunate that the Kepler mission has identified numerous small planets whose host stars can now be subjected to this kind of study.
The paper is Schuler et al., “Detailed Abundances of Stars with Small Planets Discovered by Kepler I: The First Sample,” accepted for publication in The Astrophysical Journal (preprint). | 0.828943 | 3.893563 |
Unlike all of the other planets in the Solar System, Mercury is just bare rock. It does have a tenuous atmosphere, but ground and space-based observations see just the gray rocky color of Mercury. This gray color comes from Mercury’s molten surface that cooled and hardened billions of years ago after the formation of the Solar System.
There are no active tectonic or erosion processes happening on the surface of Mercury; it has remained unchanged for billions of years, reshaped only by the occasional meteorite impact. In the past, some of the basins were filled in by magma that flowed out of the planet when it still had an active geologic cycle. Geologists are fairly certain that there are no active volcanoes on Mercury any more, but it’s possible that there could still be the occasional lava flow. Fresh lava flows would appear as a different color on the surface of Mercury. Perhaps when NASA’s MESSENGER spacecraft enters orbit around Mercury, we’ll get a better idea of its colors. Certainly we’ll know more about its surface geology.
The photograph attached to this article provides one of the best true-color images of Mercury that we have. If you could fly over Mercury in your spacecraft, this is essentially what you’d see. The planet Mercury color is a dark gray surface, broken up by craters large and small. The color of Mercury’s surface is just textures of gray, with the occasional lighter patch, such as the newly discovered formation of crater and trenches that planetary geologists have named “The Spider”.
Mercury’s coloring is very similar to the Earth’s moon. In fact, when you’re looking at images of both objects, it’s very difficult to tell the two objects apart. Unlike the Moon, however, Mercury lacks the darker areas, or “seas”, that were created on the Moon by lava flows. Mercury’s color doesn’t have the variety that even the Moon has.
If you got here not asking what color is Mercury the planet, but what color is Mercury (the element), it’s silver, and a liquid at room temperature.
We have written many stories about Mercury here on Universe Today. Here’s an article about a side of Mercury never before seen by spacecraft, and here’s a story about the color of Mercury captured by NASA’s MESSENGER spacecraft during a recent flyby.
We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury. | 0.886021 | 3.461081 |
Astronomers have discovered four active black holes situated in close proximity to one another in the distant universe, surrounded by a giant nebula of cool dense gas.
Using the W.M. Keck observatory in Hawaii, a group of astronomers led by Joseph Hennawi of the Max Planck Institute for Astronomy have discovered the first quadruple quasar: four rare active black holes situated in close proximity to one another. The quartet resides in one of the most massive structures ever discovered in the distant universe, and is surrounded by a giant nebula of cool dense gas. Either the discovery is a one-in-ten-million coincidence, or cosmologists need to rethink their models of quasar evolution and the formation of the most massive cosmic structures.
Hitting the jackpot is one thing, but if you hit the jackpot four times in a row you might wonder if the odds were somehow stacked in your favor. A group of astronomers led by Joseph Hennawi of the Max Planck Institute for Astronomy have found themselves in exactly this situation. They discovered the first known quasar quartet: four quasars, each one a rare object in its own right, in close physical proximity to each other.
Quasars constitute a brief phase of galaxy evolution, which lasts approx. only 10 million years. Such a cosmic powerhouse is driven by the impact of matter on the supermassive black hole at the heart of the Milky Way system. During this phase, they are the most luminous objects in the Universe, shining hundreds of times brighter than their host galaxies, which themselves contain hundreds of billions of stars. But these hyper-luminous episodes last only a tiny fraction of a galaxy’s lifetime, which is why astronomers need to be very lucky to catch any given galaxy in the act. As a result, quasars are exceedingly rare on the sky, and are typically separated by hundreds of millions of light years from one another. The researchers estimate that the odds of discovering a quadruple quasar by chance is one in ten million. How on Earth did they get so lucky?
The four quasars are surrounded by a rare giant nebula of cool dense hydrogen gas – which the astronomers dubbed the “Jackpot nebula”, given their surprise at discovering it around the already unprecedented quadruple quasar. The nebula emits light because it is irradiated by the intense glare of the quasars. In addition, both the quartet and the surrounding nebula reside in a rare corner of the universe with a surprisingly large amount of matter. “There are several hundred times more galaxies in this region than you would expect to see at these distances” explains J. Xavier Prochaska, professor at the University of California Santa Cruz and the principal investigator of the Keck observations.
Given the exceptionally large number of galaxies, this system resembles the massive agglomerations of galaxies, known as galaxy clusters, that astronomers observe in the present-day universe. But because the light from this cosmic metropolis has been travelling for 10 billion years before reaching Earth, the images show the region as it was 10 billion years ago, less than 4 billion years after the big bang. It is thus an example of a progenitor or ancestor of a present-day galaxy cluster, or proto-cluster for short.
Piecing all of these anomalies together, the researchers tried to understand what appears to be their incredible stroke of luck. Hennawi explains “if you discover something which, according to current scientific wisdom, should be extremely improbable, you can come to one of two conclusions: either you just got very lucky, or you need to modify your theory.”
The researchers speculate that some physical process might make quasar activity much more likely in specific environments. One possibility is that quasar episodes are triggered when galaxies collide or merge, because these violent interactions efficiently funnel gas onto the central black hole. Such encounters are much more likely to occur in a dense proto-cluster filled with galaxies, just as one is more likely to encounter traffic when driving through a big city.
“The giant emission nebula is an important piece of the puzzle,” says Fabrizio Arrigoni-Battaia, a PhD student at the Max Planck Institute for Astronomy who was involved in the discovery, “since it signifies a tremendous amount of dense cool gas.” Supermassive black holes can only shine as quasars if there is gas for them to swallow, and an environment that is gas rich could provide favorable conditions for fueling quasars.
On the other hand, given the current understanding of how massive structures in the universe form, the presence of the giant nebula in the proto-cluster is totally unexpected. According to Sebastiano Cantalupo of ETH Zurich, a co-author of the study: “Our current models of cosmic structure formation based on supercomputer simulations predict that massive objects in the early universe should be filled with rarefied gas that is about ten million degrees, whereas this giant nebula requires gas thousands of times denser and colder.”
“Extremely rare events have the power to overturn long-standing theories,” says Hennawi. As such, the discovery of the first quadruple quasar may force cosmologists to rethink their models of quasar evolution and the formation of the most massive structures in the universe.
Publication: Joseph F. Hennawi, et al., “Quasar Quartet Embedded in Giant Nebulae Reveals Rare Massive Structure in Distant Universe,” Science 15 May 2015: Vol. 348 no. 6236 pp. 779-783; DOI: 10.1126/science.aaa5397
PDF Copy of the Study: Quasar Quartet Embedded in Giant Nebula Reveals Rare Massive Structure in Distant Universe
Image: Arrigoni-Battaia & Hennawi / MPIA | 0.865993 | 3.947992 |
On Tuesday April 3, Eastern Michigan University students sought to learn more about the sixth planet in our solar system, Saturn, in EMU’S planetarium located in the Science Complex. Lead by associate professor Thomas Kasper, participants sat back under the dome of the planetarium and took a journey to Saturn, its rings and its many moons.
The program started with a short introduction of spring beginning to come around and the changes in the atmosphere due to this seasonal change. The introduction focused on winter constellations such as Gemini, the twins Castor and Pollux, Sirius the dog star, and Orion the Hunter, and also focused on objects which will be leaving the northern hemisphere in the next few weeks and months.
"Saturn: Jewel of the Heavens," as the event was named after the planetary film screening, explored the many interesting facets about the planet. The film, created by Clark Planetarium in Salt Lake City, covered the history behind the discovery and exploration of Saturn, its moons, the gaseous atmosphere and its rocky core.
From ice geysers on Enceladus, a moon, to the many floating rocks in various sizes which circle Saturn forming the iconic rings, the planet has a lot to study. This planet presents countless opportunities to learn and to inspire young minds.
As students looked into the sky, Kasper said, “We learn a lot about where we came from. It allows us to look back in time almost to the time things were created…There’s no limit to what we can learn from the stars, own solar system, galaxy, the universe.”
A plethora of information can be gathered from the wide variety of Saturn’s moons, from the smallest bit of rock to Titan - Saturn’s biggest moon. This moon is bigger than the planet Mercury. With its own significant atmosphere similar to early Earth's, and traces of liquid and ice on it’s surface, scientists can look into Earth’s past, through further studies of Titan.
Once considered one of the seven ancient wonders, through studying planets like Saturn and its history, we are looking at our own. Even before Saturn got its name from the Romans, Babylonians told stories about the Seven Ancient Wonders: five planets, the sun and the moon. In learning about the history of planets like Saturn students learned about rich oral traditions and how human ancestors understood the skies above them.
“In the past Saturn was only a destination of the imagination. As we extend our presence into the solar system it is possible to imagine in the not to distant future, when Saturn and its moons are a destination for us. The past has shown us that once seemed like science fiction often becomes the reality of the future what may seem like distant dreams today could very well be the world our great grandchildren live in. These dreams represent the motivations hope, and out look of our future generations," said Kasper. | 0.837838 | 3.278546 |
PART III – Should We Be In An Ice Age Now?
RECAP: In Part I of this series, we looked at how scientists have determined that Earth has experienced regular cycles of cold climates followed by brief periods of warm climates during the last 400,000 years. We learned that the current cycle has been different because the warm period has persisted when past warm climates have rapidly dropped back into a cold climate. We also discussed how the Sun acts as a ‘battery charger’ for Earth’s climate.
Part II of the series explained that Earth’s orbital relationship with the Sun also follows a cyclic pattern and that almost 100 years ago, a Serbian named Milutin Milanković proposed possible mechanisms related to Earth’s tilt and orbit that could be the root cause of the regular cycle of Ice Ages.
PART III – Should We Be In An Ice Age Now?
No one can say for certain whether or not that we should be in an Ice Age today. Past Warm Ages have typically collapsed back into a cooler period within a few thousand years followed by a complete return to an Ice Age within about 10,000 years. If Earth past climate history is correct then our planet should be in a cooling period, if not into a full-scale Ice Age. Instead, Earth is warming. The Milankovitch Cycles don’t all concur on this issue, but there is some intriguing evidence that suggests we have missed a cooling period based on Earth’s orbit and tilt.
Consider the factors discussed in Part II of this series.
Orbit Eccentricity or Circular to Ellipse
Our orbit eccentricity is about one-third the way from our lowest level, meaning Earth’s orbit is becoming more circular. It’s cycle is about the same as Earth’s climate cycle, so it could be a significant factor. Interestingly, the eccentric peak of .02 during the current cycle was half to one-third of the peak past three cycles (.04 to .06.)¹ Could that be a factor in the prolonged warm period? Possibly, but why? Earth just passed the peak a few thousand years ago so, does a low peak eccentricity result in a prolonged Warm Age?
Obliquity or Earth’s Tilt On Its Axis
Earth is about halfway between our high and low peak tilt angles. Our planet’s tilt, or obliquity is on an approximate 41,000 year cycle, so we were just passing through our highest peak obliquity at the start of this Warm Period. If high tilt angle is a trigger for a Warm Age, then we should be cooling down, unless obliquity must be coupled with another factor to trigger a cooling period.
Axial Precession or Earth’s Wobble
Earth’s axis wobbles and it takes 26, 000 years to complete one cycle. It is hard to see a connection with the slow regression of the seasons and Earth’s climate, but perhaps the cycle of axial precession couples with another factor to trigger a cooling period, or sustain a Warm Age.
Apsidal Precession or The Hulu Hoop Effect
Apsidal precession is factor has some interesting possibilities on how it might impact Earth’s climate. Currently the Summer in the northern hemisphere occurs when Earth is farthest from the Sun (aphelion.) Our closest approach to the Sun (perihelion) occurs during Summer in the southern hemisphere.
Earth’s northern hemisphere is about 40% land and 60% water. The southern hemisphere is about 20% land and 80% water. Land that is not covered with ice absorbs more energy than water because water reflects more of Sun’s energy back into space. In Part II we learned that the hemisphere that is in summer during perihelion receives 23% more solar radiation. Because of the greater land mass, the northern hemisphere will retain more of the summer Sun’s energy in 10,000 years (when perihelion occurs in July) than the southern hemisphere does currently.
From a standpoint of apsidal precession, Earth should be in the coldest period since we are closest to the Sun when the smallest percentage of our land mass will absorb the energy or insolation.
The tilt of Earth’s orbital plane off of the invariable plane is on a 100,000 year cycle, which coincides with Earth’s climate cycle. Since higher angles of our orbital plane result in a higher obliquity and magnify the effect of land mass absorption differential between the two hemispheres, it could be a factor in triggering the Ice/Warm Age cycles; however, it is unclear how this factor could contribute to the prolonged warm period.
Are We Missing an Ice Age?
Earth’s climate cycle does not follow a perfect 100,000 year pattern. Most people would be happy if we never went into another Ice Age; however, if we have missed the trigger of the next Ice Age, what does that mean for our climate? Will Earth’s delicate climate balance be ruined leading into a runaway warm period or will the next Ice Age come in a rapid onset like in a disaster movie?
The Sun charges Earth’s climate ‘battery’ and variations in how much solar radiation our planet absorbs dramatically affects the environment for all life. It will be important for scientists to discover what is happening to our climate and why. Life on Earth exists in a narrow band that is not to cold and not to hot and we have no practical methods to reinforce or siphon off the Sun’s energy in a crisis.
While scientists to continue to examine this issue there are other issues that should be considered beyond climate. At least for the past 400,000 years, the Warm Ages have been relatively brief periods. It is during those brief periods of warmth that life has flourished, then the Earth has been cleansed with the next Ice Age. What will happen as insects, reptiles, and bacteria continue to evolve and expand without an Ice Age to push back their spread across the globe? Is it possible that too much life will threaten human existence?
These are all questions that have to be answered as long as the Earth continues to avoid the next Ice Age.
NOTES AND REFERENCES
¹Wikipedia – The Free Encyclopedia. (2011). Milankovitch Cycles. Retrieved November 13, 2011, from http://en.wikipedia.org/wiki/Milankovitch_cycles.
IMAGE 1.0 – Image thanks to http://www.space4case.com/mmw/pages/space4case/solar-system/earth/artic.php
IMAGE 1.1 – Image thanks to Wikimedia Commons at http://en.wikipedia.org/wiki/File:Precession_and_seasons.jpg
IMAGE 1.2 – Image thanks to http://www.learner.org/jnorth/tm/humm/WhyComeGlobalGame.html
IMAGE 1.3 – Image thanks to http://www.learner.org/jnorth/tm/humm/WhyComeGlobalGame.html | 0.833578 | 3.702962 |
Black holes are some of the most powerful and mysterious objects in the universe, what is left behind after a star has collapsed. NASA has compiled several dramatic images of what are believed to be black holes in space. This is a Chandra X-Ray Observatory image of the nearby galaxy Centaurus A. This image is believed to show the effects of a super massive black hole within the galaxy. (Text: Katherine Butler)
Baby black hole spotted being born
NASA recently announced that for the first time, a black hole was seen being “born” out of an exploding star in a neighboring galaxy. As Discovery News reports, “the baby black hole is located in the M-100 galaxy, which is about 50 million light-years from Earth.” NASA is excited because it now knows the precise “birth date” of a black hole, allowing experts to study it as never before.
Double black holes
Another image from the Chandra Observatory shows the galaxy M82, which has “two bright X-ray sources” of interest. NASA believes these points may be the starting points for two intermediate or super massive black holes. Researchers believe black holes may form when a star runs out of its own fuel and burns itself out. It is then crushed by its own gravitational weight. Matter collapses into “infinite density” and an extreme curve of space time is created.
Head to head
Scientists believe black holes exist according to evidence as determined by Einstein’s Theory of Relativity. Experts use Einstein’s understanding of gravity to determine the immense gravitational pull of a black hole. In this image, information from the Chandra X-ray Observatory is combined with images from the Hubble Space Telescope. NASA believes these two black holes are spiraling toward each other and have been doing so for 30 years. NASA thinks they will eventually become one big black hole.
A black hole-powered stream of electrons barrels out of the M87 galaxy into space. These are subatomic particles traveling near the speed of light. This indicates that there may be a super massive black hole at the center of this galaxy. Super massive black holes are, in fact, the largest black holes in the galaxy. This one is believed to have “swallowed up” matter equal to 2 billion of our suns.
NASA believes this image shows evidence of a recoiling black hole, caused either by two super massive black holes colliding with each other to form a system, or it is the “slingshot effect” formed from a system that had three black holes. When stars supernova, they can leave behind a huge remnant that collapses back into itself. This means they have no volume but infinite density, making them black holes.
Pulling from a star
This artist’s rendering shows a black hole pulling gas away from a nearby star. A black hole is black because its gravitational pull is so dense that it traps light. They are invisible, which is why researchers rely on their evidence to determine their existence. NASA points out that black holes can be as small as one atom or as large as a billion of our suns.
Bursting with stars
This artist’s rendering shows a quasar, which is a super massive black hole surrounded by spinning material. This quasar exists at the center of a galaxy. While quasars are the early stages of a black hole, they nonetheless may exist for billions of years. Still, it is thought that they were made in the ancient era of the universe. Any “new” quasars that are found are thought to merely have been hidden from our view.
Kaleidoscope of color
NASA, Spitzer and Hubble telescopes show a false-color image of a giant jet of particles being shot of out a super massive black hole. It is thought this jet is stretching across 100,000 light-years of space, which NASA reports is as big as our Milky Way Galaxy. The color shows the jet’s different light waves. There is a super massive black hole at the center of our galaxy called Sagittarius A. NASA believes it has a mass equal to 4 billion of our suns.
This image shows a “micro quasar,” which is believed to be a scaled-down black hole the same mass as a star. If you were to fall into the black hole, you would cross the event horizon, which is the boundary of the black hole. Even if you were not already crushed by gravity, you would not be able to cross back out of the black hole. Also, you would be in darkness to anyone watching you. Ultimately, a trip to a black hole would prove fatal. If a person were to travel into a black hole, he or she would be ripped apart by gravity. | 0.852573 | 3.574719 |
tackling the high cost of exploring space
Whenever the topic of space travel comes up, the costs involved with leaving our world are bound to come into play and without a massive infrastructure or reusable single stage launch vehicles, even routine missions will continue to come with price tags in the hundreds of millions of dollars. Want to do something more ambitious, like a grand tour of the outer solar system? Do you want to get there on the most advanced rockets we could conceivably make in the near future, adequate protection for your astronauts and have it all wrapped up in five years? That wish list will run you about $4 trillion, more than the GDP of all but three individual nations, and a lot more than would be feasible, even with an international effort. So how can we cope with the costs of space exploration and see alien worlds with our own eyes, or ever even hope to venture beyond our solar system?
Even though we can find enough energy to build a warp drive sometime in the future, the fact that we’d have to hijack distant gamma ray bursts and other energetic and distant phenomena essentially puts them way out of our reach for now. We need to think more practically and focus primarily on getting around our solar system before we aim any higher. Today, even the most ambitious and realistic designs fall short of what we’d need to travel to the stars and relativistic rocketry using exotic power sources like micro black holes are still just equations in physicists’ papers. Even if we can build them in the coming decades, they’re not going to get very far without a vast infrastructure ready to supply a massive interstellar craft. And this is why we’ll need to return to the Moon to practice surviving on other worlds, then aim towards Mars and the Jovian moons, especially the oceans of Europa where we could help robotic submersibles find life. Along the way, as we’d expand from world to world, we would build ever more satellites, launch vehicles, habitats, and use every opportunity for an interesting scientific experiment or two, enabling us to keep going even farther.
So far, we only talked about physics and practicality, What about the cost? Well, if we really want to explore the outer reaches of the solar system, we should’ve done what a surprisingly large amount of people in the U.S. already think is happening: spend $500 billion a year on spaceflight and putting space on par with that of the entire Department of Defense. And while the previous link dreams about the kind of progress that might have happened in a world where space travel was treated with the same priority as the military, we live in a world in which that didn’t happen and if we want to really travel to other worlds, we’d need to give sky-high finding to the space agencies we expect to colonize the solar system on humanity’s behalf rather than dismantle scientific and educational programs in the relevant fields. True, investing hundreds of billions into space would have major consequences for the global economy, but it would generate countless jobs and fuel innovation across the world, creating profits for companies which would help fund research, buy licenses for new inventions and integrate them into today’s high, and low tech products. Pretty much every field from energy, to construction, to industrial design would be prfoundly affected and change focus virtually overnight.
But what if you don’t want to completely restructure the global economy to pull off truly ambitious space flights and colonizing expeditions? You can’t just spend a few more tens of billions of dollars and expect that things will just take off with a little more cash. We’re talking about massive, multi-decade long projects here, many of them akin to building new cities in the middle of the wilderness, except that in this case, the wilderness would be radioactive, deadly, and brutally inhospitable to anything even remotely resembling humans. We need that seemingly unrealistic 25-fold increase to NASA’s budget if we really want to establish a real presence beyond our orbit rather than go on a few flag planting trips as Obama’s plan for space exploration would have us do. Realistically (or not so realistically), we would need to remove politicians from having a stranglehold over the space program since they’re far more concerned with using NASA as a PR tool or populist carrot than any real exploration, and treat space as a scientific and commercial venture rather than a Cold War artifact. With a slow start, help from private industry and grants for space-related R&D programs which would be considered by experts in the applicable fields, we could raise enough money to boldly set out into the solar system.
We just need to convince ourselves that it’s not impossible and avoid trampling the dreamers inside each one of us with a misguided, self-destructive pessimism and nay saying we pretend to call realism. After all, only a few generations ago we were soaring into the final frontier and calling our lifetimes the Space Age. Were three decades all it took to trade our cosmic ambitions for the humdrum, pretending that we’ll solve all the world’s problems before we return to conquering space? And do we really want to go down as the generations who decided to trade dreams of an amazing tomorrow for praising ourselves for our grounded mediocrity? | 0.806876 | 3.156486 |
It's difficult to predict exactly what will happen when the potentially great Comet ISON makes a sharp turn around the sun on Thanksgiving Day (Nov. 28). But one thing is certain: The journey will be dangerous.
At less than 730,000 miles (1.2 million kilometers) from the sun's surface, solar eruptions could rock the icy comet. Experts with NASA say lessons from another comet's tail-clipping encounter with the sun in 2007 presents a forbidding example of what could happen to Comet ISON.
That lesson comes from Comet Encke, which faithfully completes one orbit around the sun every 3.3 years and is one of the most studied comets in history. When it approached the sun in 2007, a coronal mass ejection, or CME, burst from our star and struck the comet, tearing off its tail. NASA's STEREO spacecraft captured images of the violent encounter as this video animation of the comet shows.
The U.S. Naval Research Lab's Angelos Vourlidas, who is participating in NASA's Comet ISON Observing Campaign (CIOC) explained why Comet ISON, at about 30 times closer to the sun than Comet Encke, could face an even worse fate. [Photos of Comet ISON: A Potentially Great Comet]
"For one thing, the year 2007 was near solar minimum," Vourlidas said in a statement from NASA. "Solar activity was low. Now, however, we are near the peak of the solar cycle and eruptions are more frequent."
Vourlidas was referring to sun's 11-year weather cycle. The solar maximum is typically marked by an increase in sunspots, the dark, temporary regions on the sun's surface that can give rise to CMEs.
When Comet ISON approaches the sun, it might be headed for a "hot zone" of CMEs, said Karl Battams, an astronomer at the Naval Research Lab who is also watching the comet. On Thursday, Comet ISON is expected to pass over the sun's equator on the same side of a recently active cluster of sunspots.
"I would absolutely love to see Comet ISON get hit by a big CME," Battams said in a NASA statement. "It won't hurt the comet, but it would give us a chance to study extreme interactions with the comet's tail."
Because the gas inside a CME is not very dense, the impact of this magnetized cloud of plasma would not be strong enough to tear apart a comet's core, according to NASA. A CME could, however, yank the comet's fragile tail.
And while the CME that hit Comet Encke back in 2007 was quite slow, Vourlidas believes a CME slamming into Comet ISON could have a more dramatic effect.
"Any CME that hits Comet ISON close to the sun would very likely be faster, driving a shock wave with a much stronger magnetic field," Vourlidas explained in a statement. "Frankly, we can't predict what would happen."
Both Comet ISON and Comet Encke are in the field of view STEREO-A's Heliospheric Imager, their tails waving back and forth with the solar wind. According to NASA, it is possible that both could be hit by the same CME, which would give researchers a chance see how these objects would react to widely separated locations
While ISON has slipped out of view for skywatchers on the ground, NASA's space-based fleet of solar observatories will be watching when ISON's close encounter, including STEREO-A and STEREO-B, the Solar Dynamics Observatory and the Solar and Heliophysics Observatory.
Editor's note: If you snap an amazing picture of Comet ISON or any other night sky view that you'd like to share for a possible story or image gallery, send photos, comments and your name and location to managing editor Tariq Malik at [email protected].
You can follow the latest Comet ISON news, photos and video on SPACE.com. | 0.833774 | 3.677682 |
The constellations best seen in March are Cancer, Canis Minor, Carina, Lynx, Pyxis, Vela and Volans. Cancer, Canis Minor and Lynx are located in the northern celestial hemisphere, while Carina, Pyxis, Vela and Volans lie in the southern sky.
March is the best time of year to observe some of the well-known deep sky objects located in these constellations, including Praesepe (the Beehive Cluster, M44), the Eight-Burst Nebula, the Theta Carinae Cluster, the Wishing Well Cluster and the Carina Nebula.
Situated between the far more prominent Ursa Major and Auriga, Lynx is the largest of the March constellations, occupying an area of 545 square degrees. It is, however, very faint, with no stars brighter than magnitude 3.00. Created to fill the gap between its two better known neighbours, the constellation was named Lynx because it took the eyesight of a lynx to spot it.
Lynx contains several notable deep sky objects, including the Intergalactic Wanderer (NGC 2419), one of the most distant globular clusters known in the Milky Way, the unbarred spiral galaxy NGC 2683, also known as the UFO Galaxy, and the Bear’s Paw Galaxy (NGC 2537), a blue compact dwarf galaxy.
Cancer, the celestial crab, is slightly smaller (506 square degrees) and also relatively faint. With no stars brighter than magnitude 3.00, it is the second faintest of the zodiac constellations. However, Cancer is a popular target for stargazers because it contains two well-known deep sky objects.
Praesepe, also known as the Beehive Cluster or Messier 44, lies in the centre of the constellation, and is one of the nearest open star clusters to Earth. Covering an area three times the size of the full Moon, Praesepe is also one of the largest visible open clusters in the sky. The brightest stars in the cluster are 6th magnitude.
Canis Minor is home to Procyon, one of the brightest stars in the sky. Representing one of Orion’s dogs (the other being Canis Major), the constellation is only the 71st in size with an area of 183 square degrees. It is, however, considerably easier to find than Lynx and Cancer because Procyon, the eighth brightest star in the sky, marks one of the vertices of the Winter Triangle and is also part of the Winter Hexagon, two prominent winter asterisms.
Vela and Carina are the largest of the southern March constellations. With areas 500 and 494 square degrees in size respectively, the neighbouring constellations are prominent in the southern winter sky. Together with Puppis, they once formed a much larger constellation known as the Argo Navis, which represented the Argonauts’ ship, but was divided into the three smaller constellations in the mid-18th century.
Vela, which represents the sails, contains a number of interesting deep sky objects, including the Eight-Burst Nebula (NGC 3132, Southern Ring Nebula), one of the several dozen planetary nebulae in the constellation, the Gum Nebula (Gum 12) with the Vela Supernova Remnant, Vela Pulsar and Pencil Nebula (NGC 2736).
The stars Delta and Kappa Velorum in Vela and Epsilon and Iota Carinae in Carina form the False Cross, an asterism sometimes mistaken for the brighter but smaller Southern Cross, which is used in navigation to find true south.
Carina, which represents the keel of the Argo Navis, is home to Canopus, the second brightest star in the sky. The white supergiant is one of the six stars in the constellation that shine brighter than magnitude 3.00, along with Miaplacidus (Beta Carinae), Avior (Epsilon Carinae) and Theta Carinae. Theta Carinae is the brightest member of the Theta Carinae Cluster (IC 2602), a naked eye open cluster also known as the Southern Pleiades. With a visual magnitude of 1.9, it is one of brightest open clusters in the sky. Several other open clusters in Carina are among the brightest open clusters, including the Wishing Well Cluster (NGC 3532, mag. 3.0) and the Diamond Cluster (NGC 2516, mag. 3.8).
Carina also contains Eta Carinae, one of the best known variable stars in the sky. The star is embedded inside the Homunculus Nebula, a bipolar nebula which is part of the larger Carina Nebula (NGC 3372), a vast star-forming region that consists of both bright and dark nebulae. Even though it is about four times larger than the Orion Nebula (Messier 42), its location in the southern sky makes it invisible to most northern observers and less well-known than M42. Eta Carinae itself cannot be seen north of latitude 30°N. It is a binary system composed of one of the most massive stars known and a companion that is also highly luminous, likely of spectral class O. The primary component is expected to end its life in a supernova explosion in the relatively near future.
Pyxis, which represents a mariner’s compass, is located next to what used to be Argo Navis and occupies 221 square degrees. Notable deep sky objects in the constellation include the planetary nebula NGC 2818, the Pyxis Globular Cluster, the open cluster NGC 2627 and the barred spiral galaxy NGC 2613.
Volans, the 76th constellation in size, occupies an area of only 141 square degrees and represents the flying fish. It is home to several interesting galaxies. These are the Lindsay-Shapley Ring (AM 0644-741), an unbarred lenticular galaxy also classified as a ring galaxy that can be seen not far from the Large Magellanic Cloud, the elliptical galaxy NGC 2434, and the Meathook Galaxy (NGC 2442 and NGC 2443), an intermediate spiral galaxy named for its distorted, hook-like shape.
The table below shows the latitudes between which the March constellations are visible.
|Constellation||Northern latitude||Southern latitude| | 0.80383 | 3.664631 |
One of the greatest benefits to come from space telescopes and ground-based observatories that take advantage of advanced imaging techniques is their ability to see farther into space (and hence, further back in time). In so doing, they are revealing things about the earliest galaxies, which allows astronomers to refine theories of how the cosmos formed and evolved.
For example, new research conducted by the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) has found a “ring galaxy” that existed 11 billion years ago (about 3 billion years after the Big Bang). This extremely rare structure, which the team describes as a “cosmic ring of fire,” is likely to shake up cosmological theories of how the cosmos has changed over time.
If we want to understand how the Universe evolves, we have to understand how its large structures form and evolve. That’s why astronomers study galaxy formation. Galaxies are enormous structures of stars, planets, gas, dust, and dark matter, and understanding how they form is critical to understanding the Universe itself.
In 2017, astronomers working with ALMA (Atacama Large Millimeter/sub-millimeter Array) discovered an ancient galaxy. This massive rotating disk galaxy was born when the Universe was only about 1.5 billion years old. According to the most accepted understanding of how galaxies form and evolve, it shouldn’t exist.
One of the most exciting developments in astronomy today is the way that advanced arrays and techniques are letting astronomers see farther back in time to the earliest periods of the Universe. In so doing, astronomers hope to get a closer at the earliest galaxies to learn more about how and when they first emerged – which can tell us a great deal more about their subsequent evolution.
This was the purpose of the ALMA Large Program to INvestigate C+ at Early times (ALPINE), a multiwavelength survey that examined galaxies that were around when the Universe was less than 1.5 billion years old. With funding provided by NASA and the European Southern Observatory (ESO), the ALPINE collaboration analyzed this data and learned some interesting things about the early evolution of galaxies.
In the past few decades, astronomers have been able to look farther into the Universe (and also back in time), almost to the very beginnings of the Universe. In so doing, they’ve learned a great deal about some of the earliest galaxies in the Universe and their subsequent evolution. However, there are still some things that are still off-limits, like when galaxies with supermassive black holes (SMBHs) and massive jets first appeared.
According to recent studies from the International School for Advanced Studies (SISSA) and a team of astronomers from Japan and Taiwan provide new insight on how supermassive black holes began forming just 800 million years after the Big Bang, and relativistic jets less than 2 billion years after. These results are part of a growing case that shows how massive objects in our Universe formed sooner than we thought.
By looking deeper into space (and farther back in time), astronomers and cosmologists continue to push the boundaries of what is known about the Universe. Thanks to improvements in instrumentation and observation techniques, we are now at the point where astronomers are able to observe some of the earliest galaxies in the Universe – which in turn is providing vital clues about how our Universe evolved.
Ever since astronomers realized that the Universe is in a constant state of expansion and that a massive explosion likely started it all 13.8 billion years ago (the Big Bang), there have been unresolved questions about when and how the first stars formed. Based on data gathered by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and similar missions, this is believed to have happened about 100 million years after the Big Bang.
Much of the details of how this complex process worked have remained a mystery. However, new evidence gathered by a team led by researchers from the Max Planck Institute for Astronomy indicates that the first stars must have formed rather quickly. Using data from the Magellan Telescopes at Las Campanas Observatory, the team observed a cloud of gas where star formation was taking place just 850 million years after the Big Bang.
For decades, astronomers have been trying to see as far as they can into the deep Universe. By observing the cosmos as it was shortly after the Big Bang, astrophysicists and cosmologists hope to learn all they can about the early formation of the Universe and its subsequent evolution. Thanks to instruments like the Hubble Space Telescope, astronomers have been able to see parts of the Universe that were previously inaccessible.
But even the venerable Hubble is incapable of seeing all that was taking place during the early Universe. However, using the combined power of some of the newest astronomical observatories from around the world, a team of international astronomers led by Tokyo University’s Institute of Astronomy observed 39 previously-undiscovered ancient galaxies, a find that could have major implications for astronomy and cosmology.
It takes a rich and diverse set of complex molecules for things like stars, galaxies, planets and lifeforms like us to exist. But before humans and all the complex molecules we’re made of could exist, there had to be that first primordial molecule that started a long chain of chemical events that led to everything you see around you today.
Though it’s been long theorized to exist, the lack of observational evidence for that molecule was problematic for scientists. Now they’ve found it and those scientists can rest easy. Their predictive theory wins!
It allowed us to spot auroras on Saturn and planets orbiting distant suns. It permitted astronomers to see galaxies in the early stages of formation, and look back to some of the earliest periods in the Universe. It also measured the distances to Cepheid variable stars more accurately than ever before, which helped astrophysicists constrain how fast the Universe is expanding (the Hubble Constant).
It did all of this and more, which is why no space telescope is as recognized and revered as the Hubble Space Telescope. And while it’s mission is currently scheduled to end in 2021, Hubble is still breaking new ground. Thanks to the efforts of a research team from the Instituto de Astrofísica de Canarias (IAC), Hubble recently obtained the deepest images of the Universe ever taken from space.
According to the Big Bang Theory of cosmology, the Universe began roughly 13.8 billion years ago as all matter in the Universe began to expand from a single point of infinite density. Over the next few billion years, the fundamental forces of the Universe began to separate from each other and subatomic particles and atoms formed. In time, this first stars and galaxies formed, giving rise to the large-scale structure of the Universe.
However, it was only by roughly 1 billion years after the Big Bang that the Universe began to become transparent. By about 12 billion years ago, intergalactic space was filled with gas that was much less transparent than it is now, with variations from place to place. To address why this was, a team of astronomers recently used the world’s largest telescope to search for galaxies of young stars in a huge volume of space.
For the sake of their study, the team used the Subaru Telescope – the world’s largest telescope, located at the Mauna Kea Observatories in Hawaii – to examine a 500 million light-year volume of space as it existed roughly 12 billion years ago. Using this data, the team considered two possible models that could account for the variations in transparency that astronomers have been seeing during this cosmic epoch.
On the one hand, if the region contained a small number of galaxies, the team would conclude that startlight could not penetrate very far through the intergalactic gas. On the other hand, if it contained an unusually large number of galaxies, this would indicate that the region had cooled significantly over the previous several hundred million years. Prior to their observations, Beck and his team were expecting to find that it was the latter.
However, what they found was that the region contained far fewer galaxies than expected – which indicated that the opaqueness of the region was due to a lack of starlight. As Steven Furlanetto, a UCLA professor of astronomy and a co-author of the research, explained in a recent UCLA press release:
“It was a rare case in astronomy where two competing models, both of which were compelling in their own way, offered precisely opposite predictions, and we were lucky that those predictions were testable… It is not that the opacity is a cause of the lack of galaxies. Instead, it’s the other way around.”
In addition to addressing an enduring mystery in astronomy, this study also has implications for our understanding of how the Universe evolved over time. According to our current cosmological models, the period that took place roughly 380,000 t0 150 million years after the Big Bang is known as the “Dark Ages”. Most of the photons in the Universe were interacting with electrons and protons at this time, which means radiation from this period is undetectable by our current instruments.
However, by about 1 billion years after the Big Bang, the first stars and galaxies had formed. It is further believed that ultraviolet light from these first galaxies filled the Universe and is what allowed for the gas in deep space to become transparent. This would have occurred earlier in regions with more galaxies, the astronomers concluded, hence why there are variations in transparency.
In short, if more ultraviolet radiation from galaxies would lead to greater transparency in the early Universe, then the existence of fewer nearby galaxies would cause certain regions to be murkier. In the future, Becker and his team hope to further study this region of space and others like it in the hope that it will reveal clues about how the first galaxies illuminated the Universe during that early period, which remains a subject of inquiry at this point.
This research is also expected to shed more light on how the early Universe evolved, gradually giving rise to the one that are familiar with today. And as next-generation instruments are able to probe deeper into space (and hence, further back in time), we just may come to understand how existence as we know it all unfolded. | 0.813898 | 4.014264 |
Long the subject of science fiction for us, the planet that occupies the 4th position from the sun is none other than Mars. Much of the wonder about the so-called “red planet” has been centered around the question as to whether or not it has ever been able to sustain life, or will ever be able to do so in the future. With temperatures ranging from -225 degrees to +70, and a poisonous atmosphere consisting of carbon dioxide, nitrogen, and argon, the answer to that question would seem to be a definitive no for humans, but the reasons for speculation are clear. Mars is the most like our planet, only smaller, drier, and colder; in fact, scientists point to Death Valley, Antartica, and the volcanic formations of Hawaii as being the areas on Earth that are most similar. It does have a similar daily rotational period, coming in at just over 24 hours, so drinking your morning coffee with your favorite Martian would not require that much of an adjustment beyond figuring out how to remove your spacesuit long enough to take a sip and not breathe in the air. Ah, the things we do for coffee. Mars’ orbit around the sun is nearly twice ours (687 days) so we would seem younger, and the gravitational pull has the effect of making 100 lbs come in at 38, so we’d feel thinner too. This is beginning to sound more appealing. The tilt of Mars’ rotational axis is also like ours, so it does have four seasons that last twice as long as they do on Earth. It has no rings to speak of, but it does have two potato-shaped, heavily cratered moons that are most likely asteroids that were once captured by Mars’ gravitational field and pulled into orbit. Phobus zips around Mars three times a day, and Delmos takes 30 hours to complete its orbit. I’m fascinated with the idea of looking up into the sky and seeing two moons. I think it would be so much fun! The main reason there has been so much speculation about the possibility of life on Mars, has to do with evidence of water on the planet. Currently, the thin atmosphere and cold temperatures would not allow water to exist on Mars for very long, yet the planet’s surface has great canyons and huge plains that could only have been carved out by massive floods. Missions to Mars that have collected soil and rocks have found trace minerals that also support this theory, and there are indications that a warming trend is occurring, so the investigation and speculation will most likely continue for quite some time.
Mars is a terrestial planet like Earth and Venus, with a varied landscape that has been shaped by external conditions. Mars has the largest volcano in the entire solar system, Olympus Mons, which is three times taller than Mount Everest and the size of the state of New Mexico. That’s mind boggling to me. It also has a spectacular Grand Canyon of sorts, Valles Marineris, that sits at its equator and is as long as the United States is wide. For the most part, Mars’ surface is rocky, dusty, and dry and it is at times almost completely covered by violent dust storms. Its soil is red because it contains iron oxide, commonly called rust, and its sky is also a hazy shade of red because of the constantly swirling dust. Despite the fact that it’s always cloudy on Mars, it has been one of the brightest objects in our night sky since ancient times. It is named for the Roman god of war, and its two moons are named for his Greek counterpart’s sons, Phobus (fear) and Delmos (panic), obviously not very jolly fellows. In terms of astrology, Mars rules Aries and Scorpio, and controls the aspects of all of our signs related to energy, passion, anger, determination, ambition, competition, aggression, courage, and honor. You’ll notice an important dichotomy here; Mars’ energy reminds us that we are capable of plunging into the depths of anger and soaring up to the heights of passion. It’s so necessary to remember that both are extremes, and though we may experience both, most of life is lived somewhere in between them.
Today’s cocktail had to be red of course, and so I went with a riff on a classic cocktail called a San Francisco that uses sloe gin as its base, along with two vermouths, and two different bitters. Although this drink is a Martini in terms of style, I chose to shake rather than stir so as to deliberately make the drink appear cloudy. Cheers everyone!
In Love and War
Add all ingredients to a cocktail shaker with ice and shake vigorously until very cold and strain into a martini glass. Garnish with two small tomatoes to represent Mars’ moons. Enjoy! | 0.859591 | 3.326242 |
This week’s first-ever picture of a black hole was captured by the Event Horizon Telescope, which is named after the critical boundary around the black hole. Once an object crosses the event horizon into the black hole, it will never be seen again by any observer on this side of the horizon.
The pictured black hole is fifty-five million years away, and that’s only by traveling at the speed of light. We seem to be much closer to another border beyond which there is no return, one that deserves the melodramatic name of The Apocalypse Horizon.
The world will end someday. There is no serious dispute about this fact, only a question of when. And that question seems unimportant for nearly all of us, as the end is at least several billions of years away. The Sun will expand until it engulfs the Earth, consuming whatever is left on the planet in a giant mass of red fire. No student of the universe disagrees with this, other than the few who believe that the end is even further away, with the Earth remaining just outside of the swelling Sun, surviving only to eventually collide with the Moon and then spin out to a cold death in the infinite cosmos. If that happens, it would be about a billion billion years from now. Those aren’t the only two stories: there are a few radicals who believe that instead of spinning away into the infinite, the dead husk of the Earth would eventually collapse back into the cold remnants of the dying Sun, which would take about a hundred times longer than a billion billion years.
No one can really fathom that amount of time, none of us have to worry about that end. So the fact that the world will end isn’t particularly compelling – but our lack of interest is only partially because the distant outcomes are so far beyond our capacity to envision. The disinterest is really driven by over-repetition: we’ve lived with stories of the end for about as long as we’ve had stories. There is always someone raving about the end of the world.
As a child I saw the modern ur-form of this storyteller with my own eyes, the lunatic in Times Square, disheveled in a stained trench coat and torn denim jeans, holding high a hand-lettered sign with the classic message: “THE END IS NIGH.” Even as a child I knew that he had nothing interesting to say about the end of the world. Urgency is always combined with a call to action, but the message is really about the desired action, and the story of urgency is provided only to give reason to take the action immediately. “REPENT!” The meaning and path to salvation was the story this prophet really wanted to tell; the cries of apocalypse were just a ploy to get anyone to listen.
What was the first story ever told – and why was it told? This must have been at least tens of thousands of years ago, around the time we first became capable of abstract thought. Some of those first stories must have been about food or shelter or sex. But I feel certain that on the day after the first person looked up into the sun and recalled that the sun also rose yesterday, there was some other person there to tell a story about why there would be no sun tomorrow nor any day afterwards. And that storyteller was telling the apocalyptic story to get the audience to do something. The story of the end was never really about the end, but about what the storyteller wants the audience to do now.
That is how it has been throughout all of human history, and that is why the savvy listener disregards apocalyptic tales today. The end isn’t coming unless it’s the one that’s too far away to matter. That’s the way it has always been. Anyone who tells you any different wants something from you.
But that will only be true until the day that it isn’t. The inevitable end of the Earth may be in the unreachable cosmological distance, and all of the old stories may have been diversions – but we now live in an age where humans have planetary impact of a scale that inarguably includes the ability to end all of humanity. In the simplest apocalyptic story of our times, the collective nuclear arsenal we’ve built is more than sufficient to make the planet uninhabitable. That wouldn’t be the end of all life, and the planet itself would continue on its many-billion year journey without us, but the end of humanity deserves a name, and the best one we have is Apocalypse. The term may be dramatic and it may be stained by thousands of years of misuse, but we have no better word for describing not the end of the planet, but the event that ends our time on it.
I don’t ask you to believe in any particular form of the Apocalypse. There are plentiful stories for whatever belief system you ascribe to – you can pick and choose among nuclear holocaust, environmental collapse, killer robots, infectious superbugs, or even good old fashioned Wrath of God. The point is that for the first time in human history, some of these apocalyptic stories might actually be true. And although most of the people telling you these stories probably want you to do something in reaction, unlike all previous times, the real story isn’t the desired action, but is actually the question of whether or not this particular story of the end is a true story.
All of the stories with a scientific basis have a point of no return well before the actual end, even though that point may be impossible to identify with current science. There is a point at which fissile material and nuclear technology will be so broadly available that avoiding disaster becomes improbable. There is a point at which the oceans will rise so high that areas now populated by millions will be underwater. There is a point at which the intelligence of machines will allow them to create more intelligent machines. Once those points are past, there is no going back. Those points of no return form our modern Apocalypse Horizon: the point past which we cannot prevent the end of all of our stories.
If you believe in science, you must believe that we will eventually cross the Apocalypse Horizon, and it’s possible that we have already done so. In our modern apocalyptic stories, the time between the point of no return and the storied end is about three generations. This span of parent to child to grandchild is crucial: If we are near the horizon, that means that people who are in their reproductive years today can feel confident that they and their children can live a long life before the Apocalypse occurs – but they’ll have to tell their children that their grandchildren are not likely to live out their natural lives. Or they’ll need to make up stories that are the opposite in substance but similar in purpose to the apocalyptic tales of the past: falsehoods designed to lull a doomed generation into acceptance of their unchangeable fate.
Are we the generation that lives just prior to crossing the Apocalypse Horizon? Even the possibility means that people with children in their lives might think differently than any generation before about how to discuss the future. All prior generations could simply ignore the stories of the end, as it had always been rational to do so in the past. All future generations will be past the point of no return, so will be beyond the point where choices about future generations matter. Only the generation that crosses the Apocalypse Horizon really has a decision to make about what to tell their children.
This is no entreaty to repent, I have no story of salvation to sell. This week we saw something that has never been seen before in human history, though it existed fifty-five million years ago; it is an apt time to reflect on our existence in the universe. The stories that have never been true before must now be taken seriously, for ignoring them no longer serves the truth, but furthers a lie. The Apocalypse Horizon is near enough to see, and in a sense it hardly makes any difference whether it is just in front of us or just behind us. | 0.843323 | 3.191905 |
A period of intense meteorite assaults on the inner solar system may have stopped far earlier than we thought.
Now there’s evidence to suggest that giant asteroid and comet strikes on Mars stopped 4.48 billion years ago, allowing it to develop conditions favourable to life as early as 4.2 billion years ago.
It overturns a previous suggestion that the inner solar system, including Earth and the moon, continued to be heavily hit by meteorite impacts – a period known as the Late Heavy Bombardment – until around 3.8 billion years ago.
Desmond Moser at the University of Western Ontario, Canada, and colleagues have analysed meteorites thought to come from Mars’s southern highlands. The specimens are pieces of Mars’s crust which were knocked into space by a collision, and have since fallen to Earth as meteorites. Around 120 of these have been recovered to date.
The team analysed the oldest-known mineral grains from these meteorites, zircon and baddeleyite, aged between 4.43 and 4.48 billion years old.
Zircon contains tiny amounts of radioactive uranium that decay to lead over time, which enables the age of the rock to be accurately measured. They also contain microfeatures that reveal whether they have been exposed to the high pressure typical of a big impact event, says Moser.
“We found none of these bombardment signatures in the Mars zircon and baddeleyite grains,” he says. The finding suggests that the asteroid assault of Mars ended before the analysed specimens formed.
“We know there was a giant impact on Mars, but it has to be older than 4.48 billion years ago,” says Moser. “The implication is that there could have been platform hosting life as much as half a billion years earlier than previously thought it was possible in the inner solar system.”
The massive impact on Mars would have been a “globally sterilising” event, he says. But it may also have helped to establish habitable conditions by accelerating the release of water from the planet’s interior.
“We’re refining our understanding of the history of the solar system in terms of what took place in these earliest times,” says Michele Bannister of Queen’s University Belfast.
“Impacts would take place because of things getting scattered around the system in the process of forming planets and rearranging the architecture of the system to what we see today,” she says.
But the evidence for the Late Heavy Bombardment – a specific period of heavy asteroid strikes – is diminishing, she says.
“The Late Heavy Bombardment is an idea that was originally put together because of the way that the crater record on the moon was interpreted,” she says.
It was suggested that a specific period of heavy bombardment of the inner planets was required to make sense of the moon’s craters – but measurements in the past decade made from moon rocks collected during the Apollo missions suggest otherwise.
Journal reference: Nature Geoscience, DOI: 10.1038/s41561-019-0380-0
More on these topics: | 0.852994 | 3.970329 |
Tonight’s the Harvest Moon, the full Moon closest to the fall equinox. A perfect time to catch a big orange Moon on the horizon AND the annual fall bird migration. Every September and October anyone with a small telescope or spotting scope magnifying 30x can enjoy the sight of one bird after another flying over the cratered lunar landscape. It’s so easy.
Point your telescope at the Moon and watch for dark silhouettes to flutter across its face. Because the angle of the full Moon’s path to the horizon is very shallow in September and October, the time difference between successive moonrises is only about 20-30 minutes instead of the usual 50-60. That means you’ll catch both moonlight and bird flight on successive nights without having to stay up late.
Many birds migrate at night both because it’s cooler and to avoid predators that could otherwise pick them off in a daylight run. Identifying the many warblers, blackbirds, sparrows, vireos, orioles and other species that fly across the moon while we sleep may be next to impossible for anyone but an expert, but seeing them is easy. Two night ago for fun, I counted a dozen birds in the five-minute interval around 10 o’clock through my 10-inch telescope at low power (76x). Assuming they continued to fly by at a steady rate, I could potentially have spotted 144 birds in just an hour’s time.
As you might suspect, most of those birds crossed the Moon from north to south (about two-thirds) with the other third traveling either east to west or northeast to southwest. Only one little silhouette flapped back up north in the ‘wrong’ direction.
According to the Chipper Woods Bird Observatory, located in Indianapolis, most nighttime migrators begin their flight right after sunset and continue until about 2 a.m. Peak time is between 11 p.m. and 1 a.m. Bird typically migrate at altitudes ranging from 1,500 to 5,000 feet, but on some nights, altitudes may range from 6,000 and 9,000 feet. I could tell the high ones from the low ones by their size and sharpness. Nearby birds flew by out of focus, while distant ones were sharply defined and took longer to cross the moon.
While birders may continue to use the moon night birding, they now have a new tool – NEXRAD or NEXt-generation of Weather RADar. About 150 NEXRAD sites were set up in the 1990s to track weather and storm systems across the U.S. When precipitation gets pinged by the radar’s pulse it reflects back a signal that identifies it as rain, snow or whatever. Included in the information is the material’s speed and direction of travel. NEXRAD works equally well on meteorite falls, birds and even insects. While storm activity typically shows up as familiar blotches of yellow, orange and red, birds appear as fine stipplings. By compiling NEXRAD loops, during particularly heavy migration times, you can actually watch swarms of birds wing their way south. Click HERE for a map of all U.S. NEXRAD locations, each of which links to current radar maps.
On the less technological side, watching birds pass across the Moon in a small telescope is a very pleasant activity reminiscent of meteor shower watching. At first you see nothing, then blip! a bird (meteor) flies by. You wait another minute and then suddenly two more appear in tandem. Both activities give you that delicious sense of anticipation of what the next moment might hold.
The best time to watch the nighttime avian exodus is around full Moon, when the big, round disk offers an ideal spotlight on the birds’ behavior, but anytime between waxing and waning gibbous phase will work. It’s an enchanting sight to see Earth’s creatures streak across an alien landscape, and another instance of how a distant celestial body “touches” Earth in unexpected ways. | 0.862434 | 3.002602 |
While Saturn is far away from us, scientists have just found a way to make the journey there easier. A new technique pinpointed the position of the ringed gas giant to within just two miles (four kilometers).
It’s an impressive technological feat that will improve spacecraft navigation and also help us better understand the orbits of the outer planets, the Jet Propulsion Laboratory (JPL) said.
It’s remarkable how much there is to learn about Saturn’s position given that the ancients discovered it, and it’s easily visible with the naked eye. That said, the new measurements with the Cassini spacecraft and the Very Long Baseline Array radio telescope array are 50 times more precise than previous measurements with telescopes on the ground.
“This work is a great step toward tying together our understanding of the orbits of the outer planets of our solar system and those of the inner planets,” stated study leader Dayton Jones of JPL.
What’s even more interesting is scientists have been using the better information as it comes in. Cassini began using the improved method in 2013 to improve its precision when it fires its engines.
This, in the long term, leads to fuel savings — allowing the spacecraft a better chance of surviving through the end of its latest mission extension, which currently is 2017. (It’s been orbiting Saturn since 2004.)
The technique is so successful that NASA plans to use the same method for the Juno spacecraft, which is en route to Jupiter for a 2016 arrival.
Scientists are excited about Cassini’s mission right now because it is allowing them to observe the planet and its moons as it reaches the summer solstice of its 29-year orbit.
This could, for example, provide information on how the climate of the moon Titan changes — particularly with regard to its atmosphere and ethane/methane-riddled seas, both believed to be huge influencers for the moon’s temperature.
Beyond the practical applications, the improved measurements of Saturn and Cassini’s position are also giving scientists more insight into Albert Einstein’s theory of general relatively, JPL stated. They are taking the same techniques and applying them to observing quasars — black-hole powered galaxies — when Saturn passes in front of them from the viewpoint of Earth.
Source: Jet Propulsion Laboratory | 0.808311 | 3.764776 |
New evidence from the Spitzer Space Telescope suggests that there is a “storm” of comets surrounding a nearby star, Eta Corvi, which is about 60 light-years from Earth. It is thought to be similar to the “Late Heavy Bombardment” in our own solar system several billion years ago, when comets rained down on the planets and are believed to have brought water and organics to the early Earth. The same thing may be happening now at Eta Corvi, if there are any planets there.
“We believe we have direct evidence for an ongoing Late Heavy Bombardment in the nearby star system Eta Corvi, occurring about the same time as in our solar system,” said Carey Lisse, senior research scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., and lead author of a paper detailing the findings. “We think the Eta Corvi system should be studied in detail to learn more about the rain of impacting comets and other objects that may have started life on our own planet,” Lisse said.
The makeup of this comet cloud closely resembles comets in our solar system, and suggest that a giant comet may have been obliterated, perhaps when it collided with a planet. Water ice, organics and rock have all been identified in the comet cloud. There is also an even larger, colder ring of dust farther out from Eta Corvi, which resembles the Kuiper Belt of comets and other debris in our solar system, left over from the solar system’s formation.
All of these similarities reinforce the idea that the way in which our solar system formed is much like how other older ones formed in the past, and younger ones are still forming today, as a common process in the universe.
This article was first published on Examiner.com. | 0.848978 | 3.638209 |
Happy New Year to all!
New Year’s Day proved to be a busy one for sky sights from home in southern Alberta.
Clear skies and warming temperatures allowed me to capture a trio of sights on January 1: Mercury in the morning, a unique mirage called the Fata Morgana in the afternoon, and the rising Full Moon in the evening.
On January 1 elusive Mercury was at its greatest elongation away from the Sun in the morning sky. This placed it as high as it can get above the horizon, though that’s not high at all at the best of times.
I captured Mercury before dawn as a bright star in the colourful twilight, using a telephoto lens to frame the scene more closely.
At this time the temperature outside was still about -24° C, as a cold snap that had plunged the prairies into frigid air for the last week still held its grip.
But by the afternoon, warmer air was drifting in from the west, in a Chinook flow from the Rockies.
As evidence of the change, the air exhibited a form of mirage called the Fata Morgana, named after the sorceress Morgan le Fay of Arthurian legend. The illusion of castles in the air was thought to be a spell cast by her to lure sailors to their doom.
The mirage produced the illusion of bodies of water in the distance, plus distorted, elongated forms of wind turbines and farm buildings on the horizon. The cause is the refraction of light by layers of warm air aloft, above cold air near the ground.
By evening the mirage effect was still in place, producing a wonderful moonrise with the Full Moon writhing and rippling as it rose through the temperature inversion.
As the lead image at top shows, at moments the top of the disk had a green rim (almost a distinct green flash), while the bottom was tinted red.
Here’s a short time-lapse video of the scene, shot through a small telescope. The lead image above and below is a composite of four of the frames from this movie.
This was also the largest and closest Full Moon of the year, what has become popularly called a “supermoon,” but more correctly called a perigean Full Moon.
A lunar cycle from now, at the next Full Moon, the Moon undergoes a total eclipse in the dawn hours of January 31 for western North America. This will be another misnamed Moon, a “blue Moon,” the label for the second Full Moon in a calendar month.
And some will also be calling it a “supermoon,” as it also occurs close to perigee – the closest point of the Moon to Earth in its monthly orbit – but not as close a perigee as it was at on January 1.
So it will be less than super, but it will nevertheless be spectacular as the Full “blue” Moon turns red as it travels through Earth’s shadow.
— Alan, January 2, 2018 / © 2018 Alan Dyer / amazingsky.com | 0.844634 | 3.174333 |
November 30, 2012 report
Research model suggests moons of some planets developed from rings
(Phys.org)—French researchers Sébastien Charnoz and Aurélien Crida have proposed in a paper published in the journal Science that moons that orbit some of the planets in our solar system came about due to accretion from material in rings that used to surround the planets, rather than as entities that took shape while their host planets were forming.
Space researchers have long proposed that moons circulating planets generally came to exist in one of three ways: as entities that formed on their own as their host was developing, as clumps that coalesced from material shed from a planet struck by some other body, or by being captured as they passed by. In this new research, Charnoz and Crida propose a fourth possibility – that the moons were formed from material in rings that surrounded their host planet.
In attempting to explain how moons orbiting planets such as Uranus, Neptune and Pluto, came about, the researchers created mathematical models that could predict moon formation from material surrounding a planet. Their models suggest that when material in a ring reaches a certain critical point at some distance from the host, called the Roche radius, the gravity from the host planet is offset by the gravitational pull that each piece exerts on others in the ring. Because of this, material in the ring begins to coalesce with some pieces eventually accreting enough material to form a moon. They add that the speed at which material in the ring orbits the host may account for the number of moons that form. Slow moving material might result in the formation of several small moons, while fast moving material may result in just one, as might have been the case with Earth and its single moon. Their model explains, they suggest, why all of the moons orbiting planets (except for Jupiter) in our solar system grow in size as they orbit farther from the host planet. Jupiter they say, is an exception, with its moons likely originating in tandem with the planet birth itself.
The researchers concede that their models can't explain how the rings themselves came to exist, but suggest it's possible that they came about due to collisions with other bodies moving through space.
When a planetary tidal disk—like Saturn's rings—spreads beyond the Roche radius (inside which planetary tides prevent aggregation), satellites form and migrate away. Here, we show that most regular satellites in the solar system probably formed in this way. According to our analytical model, when the spreading is slow, a retinue of satellites appear with masses increasing with distance to the Roche radius, in excellent agreement with Saturn's, Uranus', and Neptune's satellite systems. This suggests that Uranus and Neptune used to have massive rings that disappeared to give birth to most of their regular satellites. When the spreading is fast, only one large satellite forms, as was the case for Pluto and Earth. This conceptually bridges the gap between terrestrial and giant planet systems.
© 2012 Phys.org | 0.879798 | 3.889489 |
For the average person, the astrophysics involved in the earth’s single-star solar system may be difficult enough to grasp, but for a pair of planet-hunting citizen scientists and a group of international researchers taking part in a Yale University-led project that recently uncovered a new planet, one-star systems are just the tip of the iceberg.
The research team, which includes Dirk Terrell, a Boulder-based astrophysicist with the Southwest Research Institute, earlier this year identified and confirmed the existence of the first known planet orbiting twin suns in a distant star system that is in turn orbited by a second set of distant stars.
The planet, dubbed PH1, is what scientists are calling a circumbinary planet in a four-star system and is the subject of a paper presented Monday at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno, Nev. It is one of only seven known planets in circumbinary star systems — where the two central stars orbit one another — and the only one in a system with two other orbiting stars, researchers say.
“It goes to the extremes of planet formation,” said Meg Schwamb, an astronomy and astrophysics postdoctoral fellow at Yale who was the lead author of the paper on PH1 and a co-founder of the Planet Hunters project that lead to the discovery. “We don’t truly understand how planets form around these stars.”
PH1 was first spotted by a pair of “armchair astronomers” who were analyzing data from NASA’s Kepler spacecraft on the PlanetHunters.org website that invites citizen scientists to try their hand at spotting patterns in data that might otherwise go unnoticed. Schwamb notes the human brain has tremendous capacity for spotting patterns and sometimes people pick up patterns in data that machines miss.
“The way the Kepler satellite works is it measures the brightness of stars, very, very accurately,” explained Terrell, who has 20 years of experience in astrophysics and primarily studies binary star systems.
Terrell said Kepler keeps data on the light curves it observes from distant stars. When the light curve dips, or vibrates slightly, it is a sign of an object passing before the star, which sometimes indicates the presence of an orbiting planet.
Earlier this year, Planet Hunters volunteers Kian Jek of San Francisco and Robert Gagliano of Cottonwood, Ariz., were analyzing light data from PH1’s two parent stars when they noticed faint dips in the light caused by the planet. They alerted the research team to their observations, which lead to verification work and eventually the paper presented Monday.
“It’s a great honor to be a Planet Hunter, citizen scientist, and work hand-in-hand with professional astronomers, making a real contribution to science,” Gagliano said in a new release issued by Yale.
Schwamb lauded Jek and Gagliano for spotting the light patterns created by PH1, noting the difficulties in making such observations.
Schwamb was working to verify Jek and Gagliano’s observations in March when she made a visit to the offices of the Southwest Research Institute’s Boulder-based Space Studies and Spacer Operations Departments and ended up meeting with Terrell.She said he did a great job modeling the light curve data coming from the system to show the pattern created by the almost imperceptible transits of PH1 across its parent stars.
“I dug into it for a few days, and I found that yes indeed they did have a planet in this system,” Terrell said.
After Terrell helped confirm the existence of PH1, researchers utilized the Keck telescopes in Mauna Kea, Hawaii, some of the most powerful telescopes in the world, to zero in on the system and learn more about it.
So far, using all the data they have been able to collect, researchers have determined that PH1 is a gas giant and its radius appears to be a little more than six times that of the Earth, or slightly smaller than Neptune or Uranus.
The two stars at the center of the system are roughly 1.5 and 0.4 times the mass of the sun, and while they both technically orbit their combined center of mass, the larger star is much closer to the center and the smaller star effectively orbits it every 20 days, with PH1 orbiting them every 138 days. The pair of distant stars in the system are roughly 1,000 astronomical units away from the central binary, or 1,000 times the distance between the Earth and the sun.
Terrell said this discovery will have a powerful impact on the way binary stars systems are regarded by researchers, and astronomers will have to look very carefully at how planets form in conditions like that of PH1.
“There are lots of binaries but only a handful of planets have been discovered,” he said. “This has all kinds of implications for how planets form in multiple star systems.”
With research funding being very hard to come by in the field, Terrell applauded the efforts of citizen scientists like Jek and Gagliano in helping make such discoveries. He said it’s hard to predict when a discovery like that of PH1 may have much wider-ranging scientific implications, which is why it is important to continue looking to the stars.
“You just never know,” Terrell said. “You explore, you try to understand things and try to know as much as you can so when the situation arises, you are able to make use of it.”
Contact Camera Staff Writer Joe Rubino at 303-473-1132 or [email protected]. | 0.89856 | 3.769209 |
A new supernova discovered by students in London is starring in a new webcast, and you can watch it live online today (Jan. 30).
Supernova 2014J was spotted by four undergraduate students observing galaxy M82 while astronomer Steve Fossey taught them how to use a telescope at the University College London Observatory on Jan. 21. Fossey and his students will take part in the online Slooh Space Camera webcast about the exploding star discovery beginning at 4 p.m. EST (2100 GMT). You can watch the live broadcast featuring views of the new supernova on Space.com via Slooh.
"We are looking forward to this broadcast," Slooh technical director Paul Cox, who will interview Fossey and the students, said in a statement. "It's always a pleasure to interview those responsible for a new discovery — getting their unique perspective — while watching live images on Slooh." [See photos of the new supernova in galaxy M82]
SN 2014J is the closest of its kind to Earth in more than 40 years. Ben Cooke, Tom Wright, Matthew Wilde and Guy Pollack — the astronomy students speaking with Slooh today — caught sight of the star explosion after Fossey saw something odd when adjusting the telescope. They found the new supernova by checking an online archive of M82 images and seeing that it was a new feature on of the galaxy.
"The weather was closing in, with increasing cloud, so instead of the planned practical astronomy class, I gave the students an introductory demonstration of how to use the CCD camera on one of the observatory's automated 0.35–metre [13.7-inch] telescopes," Fossey said in a statement from UCL.
The new supernova is about 11 million light-years from Earth and is expected to brighten until Feb. 2, when it might be visible with only binoculars. Scientists think the new star explosion is a Type 1a supernova — the kind astronomers use as "standard candles" to measure cosmic distances because they have comparable intrinsic brightness.
NASA is planning to make observations of SN 2014J using observatories like the Hubble Space Telescope, the Nuclear Spectroscopic Telescope Array (NuSTAR), the Fermi Gamma-ray Space Telescope and the Chandra X-ray Observatory. The space agency's Swift spacecraft has already taken images of the new supernova.
"Finding and publicizing new supernova discoveries is often the weak link in obtaining rapid observations, but once we know about it, Swift frequently can observe a new object within hours," Neil Gehrels, the Swift mission's principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md., said in a statement on Jan. 24.
You can also watch the supernova webcast directly from Slooh at http://events.slooh.com/. | 0.874322 | 3.14414 |
Some months back I made some from the hip comments about ‘Oumuamua, that strange little visitor from outside the solar system. Some of them were superseded by later events, others are certainly debatable. However, in the last week or so, ‘Oumuamua has been in the spotlight due to renewed speculation that it could be artificial, so it is time to revisit this object.
Most of the conclusions that have been reached about it are based on delicate calculations of its movement through space, made based on precise measurements of its position at different times. So it behoves us to understand this data and its implications.
The first thing to say here is that the data arc that is all we have to investigate the orbit, covers just the range from 14th October 2017 to 2nd January 2018. So, the last astrometric observation of ‘Oumuamua – that is, accurately measured position to determine its orbit – was taken on January 2nd 2018. There will be no more data because, now approaching the orbit of Saturn (today, it is 8.5AU from the Sun), ‘Oumuamua is fainter than magnitude 32: that is far below the limit of any telescope on Earth, or the Hubble Space Telescope.
All our knowledge of this strange little body’s path through space is based on just 207 measurements of its position over 80 days, the first of them taken five weeks after it had passed perihelion.
Modern techniques of measurement are infinitely better than anything that was available thirty or forty years ago, but still have their limits. Astronomers like to have years, even decades of data to get a really precise orbit solution, particularly when we are treating the tiny effects that are causing such interest in ‘Oumuamua. Similarly, they like to have data both before and after the objects pass through perihelion. What we have is less than three months of data and all obtained as it moved away from the Sun.
What we know beyond any possible doubt is that ‘Oumuamua came from outside the solar system. It was travelling too fast when it passed by the Sun to have fallen from anywhere within our solar system. Technically, the orbit is strongly hyperbolic, or open. We can calculate that it entered the solar system at 26.4km/s. About half of that velocity can be explained as the Sun’s movement towards the Solar Apex: the point in the sky towards which the Sun and the Solar System are moving through space. If we trace ‘Oumuamua’s movement backwards, we discover that its point of origin is only about 4 degrees away from the Solar Apex, close to the star Vega:
RA (Origin) 18h 37m 55.0s, Dec. (Origin) 33⁰ 50ʹ 25″
The approximate point of origin of ‘Oumuamua, marked with the yellow cross.
Similarly, we can work out towards which point in the sky ‘Oumuamua is heading, which is in Pegasus:
RA (Final) 23h 51m 23.0s, Dec. (Final) 24⁰ 42ʹ 06″
‘Oumuamua takes 11500 years to travel one light year and travels 87 light years in a million years but, in a million years, constellation outlines change a lot. In less than the time than ‘Oumuamua takes to travel a distance equivalent to that from the Sun to Sirius, the stars of Lyra and the surrounding constellations will have moved quite substantially.
The North Pole of the sky and the Great Bear as we see it today.
And, as we will see the North polar area of the sky in the year 91000AD. Note how much the familiar form of the Great Bear has changed and how much Vega has moved away from the other stars of Lyra.
The North Polar area of the sky now and in the year 91000AD, compared. The sky and the constellation of Lyra would have looked very different a million years ago or, whenever in the past ‘Oumuamua set out, making it extremely difficult to work out which stars it may have been close to in the distant past.
Astronomers have analysed catalogues of nearby stars in an attempt to identify the origin of ‘Oumuamua. Two factors complicate this:
- Despite the immense progress that is being made with Gaia to measured precise positions of movements of nearby stars in space, this is still a work in progress – release of Gaia’s data is still in its early phases – not all candidate stars have good data yet so, their positions in space tens of thousands of years ago are uncertain.
- Each encounter of ‘Oumuamua with a star perturbs its orbit and adds an uncertainty to its future path. If the mass of the star and the exact distance at which ‘Oumuamua passes it are uncertain, the perturbation will be uncertain and thus the future path will be increasingly uncertain with each pass. Tens of stars would have influenced ‘Oumuamua’s trajectory in the last few million years and, with each encounter, the extrapolation of its path gets more uncertain.
Seven encounters with stars to a minimum distance of 1 parsec (3.3 light years) were found in the last seven million years. In all but one of the cases, ‘Oumuamua would have passed the star much faster than its entry velocity in the solar system: for three stars, the encounter would have been at velocities from close to 200km/s up to more than 300 – implying that ‘Oumuamua flashed through the system very quickly. None of these look like likely points of origin. In three other cases, the velocity was between 60 and 70km/s, more than double the entry velocity in the Solar System. One star, HIP 981, with a rather low encounter velocity and an approach to half a parsec, just over six and a half million years ago, but the movement of this star is almost indeterminate, so the encounter circumstances are little more than a guess.
Although one star, the prosaically named UCAC4 535-065571, is an interesting candidate, its movement is not well enough known either at present to be certain about it. Playing with the numbers a little to obtain the best fit, they find that this encounter would have happened 2.1 million years ago.
It has to be said that most of the stars that ‘Oumuamua would have encountered are red dwarfs, with masses smaller than the Sun. None, at present, looks like a really good candidate. Some studies have suggested that ‘Oumuamua may have spent hundreds of millions of years wandering through space.
So, what we can say is that the point of origin of ‘Oumuamua is unknown, although there is some hope that the Gaia data release of 2021 will improve the situation by giving accurate data for all the possible stars in the solar neighbourhood. We must remember this: at present, it seems unlikely that ‘Oumuamua came from a star less than 100 light years away, when considering some of the more exotic theories about it.
The biggest killer to the study is that the orbit used in it is a quite old one, based on less than one month of data and it does not include the non-gravitational terms that were found later so, will inevitably have some cumulative errors when extrapolated into the far future that will make the conclusions unreliable, but much bigger errors when extrapolated into the distant past. Indeed, the orbit solution provided by NASA’s Jet Propulsion Laboratory (JPL) explicit states “the behavior … outside the observed data arc from 2017 October 14 to 2018 January 2 can only be assumed. Predictions outside this time interval, especially prior to October 2017, could be much more uncertain than reported here.”
The difference between the orbit solution used to study past encounters of ‘Oumuamua with stars and the final orbit solution is nearly 2 arcminutes in the next 80 years, almost all in declination. If we go back in time, the difference is even bigger: 12 arcminutes in 1901 between the two ephemerides, which does very much invalidate conclusions about its point of origin.
It is this identification of non-gravitational terms of motion, a result, so controversial initially, that it was not released until thoroughly and absolutely checked and other explanations excluded, that has re-awoken suggestions that ‘Oumuamua could be artificial.
As far back as the nineteenth century, astronomers realised that something other than just gravity was affecting the movement of comets. However accurate the observations, however careful the calculations, something was causing comets to advance or delay themselves in their orbits. It was only a tiny amount – usually only a few hours in an orbit of years, but it refused to disappear. Initially, astronomers tried to explain it as being the result of a “resisting medium”, something that slowed comets down like air resistance slows a ball thrown through the air. It was only about fifty years ago that is was realised it was the gas jets blasting off the nucleus of the comet that were pushing the it slightly off course.
With sufficient observations of sufficient quality, the effect of these forces could be measured as accelerations in the radial direction (away from the Sun, given as A1), the transverse direction (laterally, A2), and normal direction (perpendicular to the plane of the solar system, A3). Usually, A1 is the biggest and most easily calculated, while A3 is usually too small to measure.
As ‘Oumuamua moved away from the Sun, it became obvious that it was accelerating, or rather, the Sun’s gravity was slowing it less than it should. The difficulty was that no one could find any evidence of cometary activity that would cause the acceleration. That does not necessarily mean that such activity did not exist. When it was discovered, it was already outside the Earth’s orbit, at 1.1AU from the Sun and had reached 2.9AU when last seen but, at perihelion, it had been as close as 0.26AU from the Sun, well inside the orbit of Mercury. It is quite possible that there was activity when close to the Sun that was not detectable after discovery, although possibly still present at a low level.
The value of A1 that was calculated for ‘Oumuamua was rather large: A1=2.8 in units of 10-7 AU/day2. This is the fifth largest ever calculated (for comparison, the value for Comet Halley is 0.0027), which is an unexpected result for an object that is apparently inactive.
Despite the claim in the paper that the significance of the result is “some tens of sigma”, the formal value calculated by JPL is A1=2.79±0.36, making the formal significance 7.8 sigma – still totally beyond doubt, given that the probability that a 6 sigma result is obtained by chance is about one in a million. However, the values for A2 and A3 that are calculated for ‘Oumuamua are totally indeterminate (less than 0.5 sigma in both cases) and so, consistent with zero.
Argument now centres around whether these results can be obtained naturally, or not. Everything centres around interpretation.
If ‘Oumuamua is as elongated as is claimed – its light curve amplitude of two and a half magnitudes suggests a cigar-shaped object, ten times as long as it is broad – and if the jet activity is as great as is suggested, calculations indicate that it would make ‘Oumuamua start to spin so fast, like a windmill out of control, that it would rapidly break apart. This, obviously, has not happened.
So, there are least two possible interpretations:
- ‘Oumuamua did have cometary activity close to perihelion, but is not as elongated as the light curve suggests. There are certainly researchers who believe that the very elongated shape has been exaggerated and that the difference between length and width is only a factor of 5, or less, making it less susceptible to catastrophic spin.
- ‘Oumuamua is much less dense or thinner than believed and is being affected by light pressure.
The most dramatic manifestation of (2) is the recent suggestion that it might be a light sail, although the relatively low velocity of ‘Oumuamua is not consistent with a light sail, unless it has come from a star much less luminous than our Sun. Of course, a light sail implies artificial which, in turn, suggests deliberate targeting at our Solar System. In fact, the non-gravitational acceleration in the orbit is yet another parallel with the Rama or Arthur C. Clarke’s novel, “Rendezvous with Rama”, as Rama also accelerates as it moves away from the Sun.
More plausible than the light sail would be a monolith-shaped structure like TMA-1 from “2001 a Space Odyssey”, which would be susceptible to light pressure and, if tumbling, would produce the high-amplitude light curve. It is difficult though to understand how this could be a natural object and how it could come to visit us.
A maxim in science is “extraordinary claims require extraordinary proof”. You should only invoke a revolutionary explanation if you have bullet-proof evidence for it. So far, the evidence for a non-natural origin for ‘Oumuamua is circumstantial and alternative and, more likely, explanations exist.
What would have been extraordinary proof? That would be any evidence of manoeuvring in the inner solar system, or deliberate targeting towards a star if our Sun were being used for a gravitational assist. We have no evidence of the former and the latter seems not to be the case, given that there is no obvious target star.
I suggested to a colleague that if ‘Oumuamua is an alien probe – light sail or otherwise – it is going about exploring our solar system in an odd way. His reply, tongue in cheek, was “maybe it is a survey mission of solar-like stars”. Well, if it is, it is going about it in a very odd way because there are no nearby solar-like stars either in the direction that it has come from, or the one that it is heading and, unless aliens know some method of communication that breaks the laws of physics as we know them, would never be able to communicate its results.
No, it is far more likely that ‘Oumuamua is a completely natural object, but that our observations of it are so incomplete that we will probably never be able to understand it fully.
[Author’s Note: I have made a couple of small edits to this post since the original posting to add small details that I had previously overlooked.]
1 parsec is 3.26 light years, but the authors extended their search limit slightly to 3.3 light years to include a seventh encounter that seemed particularly interesting.
Lest someone think that this was suppression of data to avoid “the public” finding out the true nature of ‘Oumuamua until it was too late, actually this was a situation in which a group of scientists wanted to be absolutely certain of their conclusions before risking embarrassment by announcing an incorrect result. The results were finally published in Nature in June 2018.
The largest calculated values are: 316P/LONEOS-Christensen, 730; 205P/Giacobini-B, 78; 287P/Christensen, 8.3; 86P/Wild 3, 3.1; 1I/’Oumuamua, 2.8; 147P/Kushida-Muramatsu, 2.7; 74P/Smirnova-Chernykh, 2.5; 90P/Gehrels 1, 2.4; 117P/Helin-Roman-Alu 1, 2.4, 203P/Korlevic, 1.5. | 0.890115 | 3.769759 |
Milky Way Bulge
The Milky Way is a barred spiral galaxy, about 100,000 light-years across. If you could look down on it from the top, you would see a central bulge surrounded by four large spiral arms that wrap around it. Spiral galaxies make up about two-third of the galaxies in the universe.
Unlike a regular spiral, a barred spiral contains a bar across its center region, and has two major arms. The Milky Way also contains two significant minor arms, as well as two smaller spurs. One of the spurs, known as the Orion Arm, contains the sun and the solar system. The Orion arm is located between two major arms, Perseus and Sagittarius.
The Milky Way does not sit still, but is constantly rotating. As such, the arms are moving through space. The sun and the solar system travel with them. The solar system travels at an average speed of 515,000 miles per hour (828,000 kilometers per hour). Even at this rapid speed, the solar system would take about 230 million years to travel all the way around the Milky Way.
Curled around the center of the galaxy, the spiral arms contain a high amount of dust and gas. New stars are constantly formed within the arms. These arms are contained in what is called the disk of the galaxy. It is only about 1,000 light-years thick.
At the center of the galaxy is the galactic bulge. The heart of the Milky Way is crammed full of gas, dust, and stars. The bulge is the reason that you can only see a small percentage of the total stars in the galaxy. Dust and gas within it are so thick that you can't even peer into the bulge of the Milky Way, much less see out the other side.
Tucked inside the very center of the galaxy is a monstrous black hole, billions of times as massive as the sun. This supermassive black hole may have started off smaller, but the ample supply of dust and gas allowed it to gorge itself and grow into a giant. The greedy glutton also consumes whatever stars it can get a grip on. Although black holes cannot be directly viewed, scientists can see their gravitational effects as they change and distort the paths of the material around it, or as they fire off jets. Most galaxies are thought to have a black hole in their heart.
That image of our Milky Way Galactic Bulge, is where it all begun.
After making it, I was officially addicted to Astrophotography and there were no way back for me. Working on that image, where I didn't knew much about processing, where simply a joy.
That was amazing night of incredible seeing and that was the first time that I got under the sky's with my widefield imaging setup. It were more of a testing-equipment-night, but as soon as I found that everything ticks, I just continued to image and this is what came out as a final result, which to my eyes, were simply amazing at that time.
Also, this image gave birth to a "Milky Way Project" which I will work on in coming months. Years? :)
Optics : Tamron 17-50mm XR Di-II LD SP @ 17mm @ F5.6
Camera : Canon T3i (600D) Baader Mod
Mount : NEQ-6 Pro (Self Hypertuned)
Guiding: Not Guided
Acquisition : BackyardEOS 2.0.4
Exposure : 10 x 240 sec @ ISO800, 10 x 300 sec @ ISO400 - 1.5 Hours
Stacking : DSS
Processing : Photoshop | 0.834869 | 3.748839 |
Researchers believe that tiny clots of terrestrial air go far into space far beyond the limits of the moon's orbit. It turns out that the Earth's geokoron (a small cloud of hydrogen atoms) is pulled out to 630,000 km into space. For you to understand, the moon is removed from us on average 384,600 km.
It turns out that the moon rotates in the earth's atmosphere. And scientists for a long time did not know about this until they reviewed the observations made more than 20 years ago by the SOHO apparatus. We are talking about a spacecraft, launched in December 1995. His goal is to study the solar and cosmic weather.
A cloud of hydrogen atoms (geocorona) is visible where the earth's atmosphere collides with space. New data suggests that this cloud extends far beyond the lunar orbit, reaching 630,000 km above the surface of the planet
Scientists analyzed the archived information from the SWAN instrument, capturing data on Lyman-alpha radiation. The solar wind is in contact with the hydrogen atoms of the geocorona at the Lyman-alpha wavelength, which is blocked by the earth's atmosphere (therefore, it must be observed from space). This work allowed us to form a map of the geocorona length and get an idea of the density of this area. It turns out that geocorona is denser on the day side due to compression from solar radiation. However, everything is relative, because only 70 hydrogen atoms per cm 3 are observed on the day side at an altitude of 60,000 km, and 0.2 atoms per cm 3 at a distance of the Moon.
The Earth and its hydrogen envelope (geocorr) in observation from the moon in ultraviolet light. The picture was taken in 1972 by astronauts of the Apollo 16 mission.
Researchers have long known about the existence of the earth geocorns. The Apollo 16 astronauts managed to capture this feature from the moon in 1972. However, no one knew about its exact size and what it is. | 0.864688 | 3.692073 |
Venus's atmosphere evolution and clues about late accretion
Venus is Earth’s closest relative and one of the biggest mysteries of the Solar System. Paradoxically, Venus’ atmosphere also offers an incredible window into the past of terrestrial planets, all the way back to the final phases of their formation, 4.5 billion years ago.
Venus holds a unique place in planetary studies: the similarities of its characteristics with the Earth’s contrast with the clear differences in their present-day surface conditions. From a presumably common origin, their geological and climatic evolutions have greatly diverged. This makes Venus the perfect subject for comparative planetology. Thanks to Venus, we hope to understand how a planet becomes or ceases to be habitable; what factors make a planet evolve into something like Earth or rather like Venus.
To answer this question, we go for the broader picture. We developed new integrated models that consider the planet as a whole – as a system composed of multiples reservoirs interacting together. Thus, these models simulate the global evolution of the planet through an analysis of the coupled evolution of the atmosphere and mantle of Venus.These models were the ground for the present study. The initial concept dates back to the years of my Ph.D., over ten years back, when it occurred to me that key differences between Earth and Venus could result from a collision with a large-enough asteroid, blowing out a large part of Earth’s early atmosphere. At the time though, none of our model was accurate-enough to test this hypothesis – but we have made significant progress since, and looking into the consequences of asteroid impacts on planetary evolution is now within grasp. Plus, blasting a planet’s atmosphere by catapulting huge chunks of rocks is pretty cool – even if only in numerical simulations.
It rapidly turned out that the erosion of the atmosphere by single large impacts was probably the most inefficient process of the whole collision event, which promptly and mercilessly put to rest our initial idea. When we subsequently introduced multiple impacts in the simulations, however, we started to see a consistent picture emerge: while the erosion component did not have much of an effect on a global scale, the deposition of volatiles (water, CO2, N2) during an impact had significant consequences. The hurdle was actually to fit the constraints based on present-day atmospheric parameters: asteroids simply brought too much volatile in most of the simulations.
This is when we had the idea of this article: constraining the maximum amount of water in the impactors throughout the evolution of Venus in search for scenarios that could reproduce the present-day atmosphere. Since most impactors are delivered early in the evolution of the planet, our method constrained mainly the Late Accretion. This turned out to be an effective and original way to circumvent the lack of isotopic data on Late Accretion for Venus.Once the models were set up, the bulk of the work was only a matter of checking as many plausible scenarios as possible. Indeed, it only took the individual review a few hundred simulations of the 4.5 billion year history of the planet. Yet, to our greatest surprise, the results seemed remarkably solid and stood many validity checks: no matter what combination of parameters (impactor distribution, composition, etc.), water delivery during Late Accretion had to be very small. This was consistent with mostly dry asteroids. Our results, despite relying on completely different methods, were compatible with those of isotopic studies on samples from Earth. They offer an independent viewpoint on a longstanding geochemistry question. They also shine a new light on how much water could be present at the surface of Venus throughout its history (i.e. not much!). Finally, this study serves as a proof of concept for our methods and integrated numerical models to be applied to other planetary bodies to investigate their temporal evolution.
The full article ("Dry late accretion inferred from Venus's coupled atmosphere and internal evolution" by C. Gillmann, G. J. Golabek, S. N. Raymond, M. Schönbächler, P. J. Tackley, V. Dehant and V. Debaille) is available at https://www.nature.com/article... Or for online reading at https://rdcu.be/b3rTc | 0.875418 | 4.07495 |
Solar System Profile
|Age:||4.6 Billion Years|
|Number of Planets:||8|
|Number of Dwarf Planets:||5|
|Number of Moons:||181|
|Number of Asteroids:||552,894|
|Number of Comets:||3,083|
|Diameter:||18.75 trillion kilometers
(11.65 trillion miles)
The Objects in Our Solar System
There are many different types of objects found in the solar system: a star, planets, moons, dwarf planets, comets, asteroids, gas, and dust. In terms of the numbers of each of these objects, our current knowledge is as follows:
- 1 star (The Sun)
- 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune)
- 5 dwarf planets (Pluto, Ceres, Haumea, Makemake, and Eris)
- 181 moons
- 566,000 asteroids
- 3,100 comets
In terms of mass, the Sun comprises over 99.8% of the Solar System, with the planet Jupiter accounting for most of the remaining mass.
How the objects in the Solar System interact
All objects in the Solar System orbit the Sun; that is, they move around the Sun in elliptical paths. Moreover, the orbits of these objects lie roughly in the same plane, called the ecliptic plane.
The mechanism that causes the orbit of objects in the Solar System is one of the fundamental forces in nature: gravity. While the natural tendency for objects in the Solar System is to continue in a straight line of motion, the Sun exerts a force (gravity) on each object and therefore “bends” the straight path into a curved one. Additionally, other objects in the Solar System are massive enough to exert gravitational forces significant enough to alter the orbit of smaller objects. For example, the Earth’s gravity is strong enough to keep the Moon in orbit around the Earth.
The size of the Solar System
Though it is common for most people to believe that the edge of the Solar System is that of Pluto’s orbit, this is far from the truth.
Over the course of the the 20th century scientists not only hypothesized the size of the Solar System extends to almost 2 light years – that’s 125,000 times the distance from the Sun to the Earth – but also that there are many objects beyond Pluto.
Scientist now believe that there are two major regions beyond Pluto. The first is
the Kuiper Belt, a region of asteroids similar to the asteroid belt between Mars and Jupiter, and the Oort Cloud, a spherical region that contains numerous comets.
The formation of the solar system
Although there is some debate as to the Solar System’s formation, the following outline is currently the best known explanation of how the Solar System developed.
- Approximately 4.6 billion years ago a large cloud of gas and dust was disturbed by some force. (Scientists have theorized that this force was a nearby supernova.)
- As a result of this disturbance and the energy introduced to the cloud, the cloud began to move.
- Once the movement began, the cloud started to collapse in on itself due to its own gravity.
- During the process of collapsing, the cloud began to rotate and heat up.
- As the cloud continued to collapse, the cloud’s temperature continued to rise and its rotation became faster and faster. As a result, the cloud eventually began to flatten out into a disk shape with most of the mass located at its center.
- At some point the pressure and temperature became so great at the cloud’s center that nuclear fusion began to take place. It was then that the Sun was born.
- After the Sun was born, the gases and dust further out from the disk’s center began to cool and condense into tiny particles.
- As more and more particles formed they began to collide with one another and stick together, thus creating particles as large as rocks and boulders.
- Like the smaller particles that collided, the boulder-sized particles began to impact and join together. These larger bodies are known as planetisimals.
- Eventually, enough planetisimals joined together to form planetary embryos. However, unlike the small particles, boulders, and planetisimals, planetary embryos were massive enough to exert significant gravitational force on surrounding objects. Hence, instead of random collisions between objects, planetary embryos pulled objects in the surrounding area to itself.
- Once all of the material in the area of each planetary embryo was pulled in, the planets were born.
- All other significant material in the solar system that did not join to form the Sun or the planets condensed to form the moons, asteroids, or comets.
- Over time, the orbits of the planets and other bodies stabilized into the solar system that we know today. | 0.854497 | 3.696086 |
When satellites die, their signals fade into the void, leaving them as nothing more than tiny specks of bonded atoms floating in an infinite abyss. After that happens, they can be pretty hard to find. But thanks to a new interplanetary radar technique, NASA just found an old space probe that no one had seen since 2009.
Scientists at NASA’s Jet Propulsion Laboratory in Pasadena, California were testing the new system of ground-based microwave radar on the agency’s Lunar Reconnaissance Orbiter, a small robotic spacecraft orbiting the moon and sending back data for the agency’s future manned missions. But while spotting the LRO was cool in and of itself, JPL then pulled off something even more exciting: it found Chandrayaan-1, an Indian Space Research Organization probe that has been dead for well over 7 years, coasting silently in an endless loop around the moon.
“Finding LRO was relatively easy, as we were working with the mission’s navigators and had precise orbit data where it was located,” Marina Brozovic, a radar scientist at JPL and principal investigator for the test project, said in a release. “Finding India’s Chandrayaan-1 required a bit more detective work because the last contact with the spacecraft was in August of 2009.”
Finding small objects — Chandrayaan-1 is a five-foot cube of metal — near the moon is extremely difficult. Sunlight reflecting off the surface of the moon makes optical telescopes pretty much useless, and microwave radar-based systems require operators to point a beam of energy in just the right spot to find what they’re looking for. Essentially, NASA had to shoot a dime out of the air with a rifle, and only knew vaguely where it would be thrown.
But the scientists at JPL realized they did know where Chandrayaan-1 would be. Though the spacecraft was technically “lost,” in an unpredictable orbit thrown off by the moon’s inconsistent gravitational pull, scientists did know two spots it would most likely pass over: the moon’s two magnetic poles. Chandrayaan-1 was in an orbit over both of the moon’s poles doing 3D mapping and other imaging processes, pursuing the hunch that one of the two poles would have frozen water hidden in its dusty gray plains. The JPL team figured Chandrayaan would do a lap of the moon at least once every two hours and eight minutes, so they pointed the biggest microwave radar they had — a 230-foot antenna at NASA’s Goldstone Deep Space Communications Complex in California — about a 100 miles above the moon’s north pole, and waited. If anything was out there, it would bounce the signal back to the 330-foot Green Bank Telescope in West Virginia. Sure enough, during a four-hour window, something small and reflective bounced back the radar beam twice, and Chandrayaan-1 was lost no more.
“It turns out that we needed to shift the location of Chandrayaan-1 by about 180 degrees, or half a cycle from the old orbital estimates from 2009,” said Ryan Park, the manager of JPL’s Solar System Dynamics group who relayed the good news to the radar team. “But otherwise, Chandrayaan-1’s orbit still had the shape and alignment that we expected.”
Over the next three months, JPL verified the results using an even bigger radar, the National Science Foundation’s Arecibo Observatory in Puerto Rico. It’s a huge step for the future — now that NASA knows how to use this technique, it has the capability to track almost infinitely small objects (relative to the expanse of space) in lunar orbit using ground-based radar. NASA says this will be essential for “collisional hazard assessment” and for helping spacecraft navigate in the event that they lose communication with the ground or their internal navigation systems. | 0.862178 | 3.671268 |
Are we alone in the Galaxy? Is there life in other planets? Have other species evolved to technological societies comparable to ours? Or maybe the right question is, How near are we from detecting signals of alien life?
In 2013 I met Lisa Kaltenegger at The Falling Walls event, in Berlin. She is an astronomer working now at Cornell University, looking for signatures of life in exoplanets (planets outside our solar system). She is quite convinced that we are very near to detecting them.
But last week, an article was published pointing to a star, KIC 8462852, whose light shows weird changes in luminosity. Astronomers can't explain it and, of course, some raise the question, Why not? to the possibility that the behavior is due to an alien technology.
Changes in luminosity is a well known effect in stars, some of them are called variable stars. It can be produced by the star's internal dynamics, spots in its surface, by the transit of one or various planets in front of the star, hiding a small portion of the star. This last effect is used to detect planets around stars, but it lowers, at much, about 1% of its total luminosity. Another method to detect exoplanets is by tracking the gravitational effect of the planet in its star (a small but detectable bouncing effect). For this star those reductions arrive up to an inexplicable 20%. Astronomers have checked all the known physics on luminosity variability in stars, and haven't been able to explain the observations of KIC 8462852. They have also accounted for different errors in their instruments, as well as for the effect of interstellar dust, but haven't found an acceptable explanation.
Are those irregular, unpredictable and inexplicable decreases in luminosity due to a technological structure being built near the star to get its energy to feed an alien society in a nearby planet? If that was the case we would be facing a much more advanced civilization, one that can use and control the energy of its star for its needs. This idea is not new, in fact it can be found in science fiction stories. Fred Hoyle, British astronomer that coined the term "Big Bang" Theory, wrote a novel, The Black Cloud, on something similar. Some scientists say that a civilization that can control its star energy is a type II civilization. If it can control its planet energy it is a type I civilization, and if it can control its galaxy energy it is a type III civilization. We are somewhere around type 0.8 civilization.
But this is not the kind of alien life that Dr. Kaltenegger is expecting to find in the next decades. What she and many other astronomers are studying are signals from the atmosphere of planets. The light that travels through the planet's atmosphere, is absorbed and re-emitted. This changes its properties (frequency distribution, for instance) and can give hints to astronomers about the atmosphere's content. Depending on the content, we can know it can have been produced without the help of organic life (bacteria, plants, ...).
A similar announcement took place in the 1960s, when astronomers detected a very precise periodic signal coming from a star. It was originally coined LGM, after Little Green Men. But that happened to be the discovery of a new type of stars, a pulsar or pulsating star, a star of very high density and magnetic field, that ejects powerful X rays in an specific axes. As the star is rotating and that X ray doesn't need to be in the same axes as the axes of rotation of the star, when the ray points to the Earth we detect is as a pulse, that is repeated every time the star rotates. The speed of rotation can be very high, several times per second.
If KIC 8462852 is the home of a technological alien society or new physics to understand we will know in the near future. In any case, astronomy doesn't stop being surprising and fascinating.
Thirty years after the release of the film “Back to the future“, we finally reach October, 21st, 2015. This is the day when Marty McFly, with Doc. Emmet Brown, come to visit from the year 1985. Most of us have been waiting for this day, and have wondered how similar the real 2015 will be with respect to the 2015 in the movie. Now we can compare.
It is highly surprising how science fiction writers, from the great H.G.Wells or Jules Verne, to Isaac Asimov, Arthur C. Clarke, or Philip K. Dick, didn’t predict the rise of the telecommunications and the smart devices that rule our daily lives. Many sci-fi books talk about flying cars, colonies in Mars, which needs a push in controlling high quantities of energy on demand . This is not here yet, and energy is one of the most important problem that our society faces, so it will not be here for a while.
In the movie Back to the future II, we see traffic jams in flying motorways, but we also see hoover-boards. This fun transportation media for the young ones could be closer than flying cars, although not yet, and with some restrictions. It is not new to see in some laboratories that do research with superconducting materials, some sort of levitating toy train. This is based in the magnetic properties of superconducting materials. These materials can reject the magnetic field to enter in them, creating an effective repulsion that can make them levitate. Unluckily, up to date, we only know materials that have these properties at very low temperatures (~200C below zero). Also, in case of having one hoover-board today, we would need it to operate at those very cold temperatures, and it should work over magnets.
Another cool idea showed in the movie is the highly precision of the weather forecast, which can predict the end of a storm at the level of seconds. We have to know that weather forecast has made a huge improvement with respect to the twentieth century. Nowadays, mathematical models and powerful computers are great tools to provide us with good predictions. We can know with low error margin the weather of the next two to three days, and with reasonable accuracy the weather of the next week. But that level of precision is not going to be in our hands for many years. The knowledge of the initial conditions to do that is beyond our reach, and maybe it wouldn’t really be that useful. Even though we could know with high accuracy the position and velocity of all the molecules in the atmosphere, chaos theory predict that small variations in that information could lead to very different results after a time, and the computational effort would increase exponentially.
On the other side, they show video-conferences, tactile keys, devices that responds to the voice, some short of smart phone that Doc. uses, smart glasses too, and tactile money. There are already among us: Skype, Google glass, i-phone, ... Even the drone that takes the dog for a walk is not far from been used, or at least we have the technology.
Maybe the key element of these movies is the time leap that they take to travel through time. Time travel is allowed by the laws of physics. Indeed, we are currently time traveling to the future at a speed of one second per second. Well, this might not sound thrilling but Einstein’s theory of relativity also tells us how to time-travel to the future faster. To do it we only need a very fast ship. This theory predicts that the faster we move in space, the slower time elapses for us. This way, the faster we travel in space, the faster time will fly, and Marty could travel from 1985 to 2015 in a few hours. But the way he would do it is not by a leap as we see in the movie, but ti would be continuous. For example, having a spaceship that travel through space at relativistic speeds (near 300,000km/s) would make Marty experience a few hours while for the whole Earth time moves 30 years.
John L. Hall, physicist. He has devoted all of his life working in optics, and has contributed greatly in this field. He was awarded with the Nobel Prize of Physics 2005 for his pioneering work on laser-based precision spectroscopy. His research could shed light into the dark matter problem, or make rethink the definition of the unit of time.
Lindy Hall, educational specialist. She has been English teacher and consultant and educational material specialist. Both founded Sci-Teks Discovery Program for Kids, a program to communicate and teach science to kids. They put their long expertise to bring the charm of science to the youngest.
I had the opportunity to meet this wonderful marriage during an Optics Conference at Duke University in March, and I couldn’t help talking to them about science and teaching science.
You have been all your life doing research in optics, and you have contributed much in that field. How much has our society changed in this time, due to our better understanding and knowledge in photonics?
I spent the 44 employed years of my career as a senior research scientist for the U. S. government developing tools and techniques to support ever more precise physical measurements and defining basic standards. I interacted constantly with representatives of other nations to push research in the various areas related to photonics. Advances have been shared by many countries working cooperatively to develop basic knowledge and the innovation of new techniques. What I observe now are increasingly rapid changes and a broadening of available data in so many related fields that it is nearly impossible to keep up and understand how all of these pieces fit together. But in my area of frequency standards the progress has been incredibly powerful, and in the next few years there will be serious planning for changing the basis of timekeeping, from Cesium atoms and microwave frequencies to an optical clock.
The last years you have focussed your effort in teaching science to kids, one very important and not easy task. What led you to do that?
Often Nobel Prize winners take the opportunity to work on a particular cause or issue of social interest. As a university professor, I have always associated with high level, gifted students, while my wife, as a teacher of teenaged children in public schools, has seen examples of many different skills, abilities and attitudes. Together we became really concerned that declining achievement test scores indicate poor preparation and performance by students in mathematics and science, and this will seriously limit their future options for education and employment. We have had many visits to other countries faced with the same dilemma – how to get children to develop competence as well as positive attitudes and enjoyment of math and science subjects. The current popular idea for science education is called STEM (combining science, technology, engineering and mathematics to get better performance). We were hoping to add another “M” for motivation: helping students want to learn, remember and apply what they discovered for themselves. It was our hope that providing free expression, exploration and contact with a variety of materials would encourage expanded views and enjoyment of science learning.
At lot has been written about teaching techniques to communicate science. The activities you perform are experiment based. How do you present science in your activities? What are the goals you seek?
We developed 23 different workshops for elementary school students, 3 for each grade from kindergarten to grade 6 on topics requested by the teachers. Students come in to the library where the materials are placed on tables and have 45 minutes to use and try what interests them. Although there are teachers available, there are no formal lectures or demonstrations. Pupils can choose to work on their own, or with a partner or in a group, and they usually end up teaching each other. They are free to explore and exchange ideas and observations. The kids will often ask high level questions or make smart and insightful comments. We lend the sets of books that go with the activities to their classrooms for several weeks afterward, in case they would like to learn more on their own. The main sadness we experience is that the school runs by a strict schedule, and that often interrupts some “magic” the young people were making and experiencing.
Our society is fundamentally based in science and technology. It seems logical to think that we want our youth to be good in these subjects. From your experience, do you think it is true, or on the contrary, is there a need of these types of activities to complement their training from school?
Your observation represents the basic truth about the American culture and experience 100 years ago. New kinds of machines were appearing and were very appealing. However the designs were early and not well evolved, so “repairing” was a natural hobby or occupation. So the people who were skilled with their hands, or had mechanical insights were very important in that society. Nowadays, it seems much of the complexity and design issues concern embedded software and micro-electronics. So the sophisticated analysis and design classes for the University students have only a marginal advantage to them if they need to maintain their gear. In affluent times it leads to a huge turnover of high-tech hardware – cellphones for example are discarded long before their functioning is degraded. I worry about our evolution and extreme specialization but, still, the networking tools are so powerful that I can easily find a service I need – say keeping my small grassy area tidy and growing well. A few moments online will let me learn other people’s experience with this or that service organization, and the competition keeps the price low. The system is comfortable and works well for the established person, who can thereby grow ever more detached from the reality outdoors. I think the new model will win out, especially if we can understand how to engage the interest and energies of people who no longer have a meaningful and valuable occupation. But the problem is that quick internet answers for a young person does not form a strong enough educational foundation.
I once read the book “Physics for future presidents: the science behind the headlines”, by Richard Muller, which I think is a good idea not just for future presidents, but for all society. From my experience in Spain, science is not seen as culture, but as something weird only accessible to freaks. On the other hand, when I have taught Physics to the broad audience I have seen how well people feel when they understand scientific concepts. Is the situation in the U.S. different? I think you have a long experience in outreach activities and very good science communicators.
The roles of contemporary science and technology are not well understood in the U. S. On the one hand, the society enjoys the products developed for business, communication and entertainment but on the other hand, the step by step necessary preparation for a career in research or development is not so clearly The roles of contemporary science and technology are not well understood in the U. S. On the one hand, the society enjoys the products developed for business, communication and entertainment but on the other hand, the step by step necessary preparation for a career in research or development is not so clearly defined and attractive. Traditionally, four years of college or university experience would be the entry way for a comfortable and satisfying middle class life. I believe this channel is still open, but works well mainly for the extra-bright student, or one whose parents had the time to deeply invest in his/her broader education. A new highway of growth and expanding possibilities involves the front edge of technology adoption by the general public. For example my new iPhone is vastly too complex for a mere University professor to learn efficiently by himself, so a visit to the Apple store was in order. Their young lady (maybe 26 yrs) had served in the US Navy, with extended terms in Japan, Taiwan, as well as two years on the ship. She absolutely knew the iOS system and understood a zillion subtle issues that I didn’t know about, in spite of my being a long-term Apple user, ever since the Apple II days. I am absolutely sure that her future will be wonderful, and with the rewards and freedom to make choices on a scale no ordinary University Graduate could dream about.
But your question is larger: there are fantastic and fascinating Physics questions opened up by the synthesis of advances in experimental techniques, coupled with advances in the theoretical frameworks. We have gone from a secure belief in the Big Bang, to the present case where many people think that Multiverses might well have come from “phase fluctuations,” along the lines believed involved in our Big Bang. The questions about the properties of space and time especially are interesting now, due to progress in the atomic clock business. I was a US representative on the committee of 50 nations that in 1982 proposed the 1983 adoption of a constant numerical value for the speed of light. At that time there were experiments showing the speed of light was constant to 9 digits over a decade of years, and had the same value at microwave and optical frequencies. But now, some 30 years later, the measuring precision is basically 18 digits and a number of questions can be perceived: 1) Is the speed of light really constant over cosmological time scales? (This is just one way the Dark Energy idea may not be correct.) ; 2) Is there a preferred direction or position effect that we traditionally are ignoring? ; 3) Is the Dark Matter arranged smoothly, or is it in clumps? Does it have an optical index of refraction effect? ; 4) Gravity and Quantum theory seem hard to combine – do we need more patience, or is there a real issue? One really good experiment would be to have several types of precise clocks exploring different gravitational fields, while comparing them to each other and an earth-based station, but with the full precision possible.
One current issue is whether Einstein’s preference for having clocks have a standard gravitational redshift is actually correct: Of course the General Relativity gravitational redshift is real – all the GPS satellites must be set with an offset frequency so that the waves at the earth have the correct atomic frequency. But consider a light-pulse clock, where a stiff crystalline material spaces the mirrors, and the repeating light pulses are compared to optical frequencies using an Optical Frequency Comb. The atomic physics forces defining the crystal lattice spacing have a coefficient 42 orders of magnitude larger than the gravitational interactions: how can the gravitational potential have any effect, when the gravitational force is itself nearly negligible? There is an international collaboration called STAR that is planning a ‘satellite in earth orbit’ experiment to check these ideas. The strongly elliptical orbit will scan us through the ranges of Special Relativity time and length effects, in addition to the General Relativity redshift and Shapiro time delay. Of course there is a noon-midnight GR shift due to the sun, which will be observable when we have a full-earth coherent time/frequency transfer system in operation.
Physicist, working in quantum optics and nonlinear dynamics in optical systems. Loves to communicate science. | 0.87801 | 3.245626 |
It is widely accepted that the Moon was created by a collision of a Mars size object with the Earth a few billion (thousands of years) years ago. One open question about it was on the tilt of the Moon's orbits. This week's Nature issue might give an answer to it and seems to be related with gold fever.
When the solar system was being formed, the Earth was just a very hot ball, and many bodies were flying through the solar system, one big object collided with the forming Earth and the debris of that collision ended orbiting the Earth at about just 20,000 miles from it. Gravitational pull of the Sun, the Moon-Earth system and other objects made both objects draw away slowly to its current 200,000 miles (and still drawing away). The gravitational dance of the Earth and the Moon should have made the Moon to move in the same plane as the Earth is doing. But it happens that the orbit of the Moon is tilted about 5 degrees from the orbit of the Earth. This has been an open question until Kaleh Pahlevan and Alessandro Morbidelli from CNRS, Nice, France, published this week on Nature their research (Collissionless encounters and the origin of the lunar inclination).
The solar system is not empty at all. There are lots of small objects moving through it, some of which impact into planets or satellites (Schoemaker-Levy), some of them are ejected from the solar system due to gravitational effects, some of them are swallowed by the Sun or might fall into a periodic stable orbit (Halley). The letter just published claims that collisionless impacts have been affecting Moons orbit to be those 5 degrees apart from Earth's orbit. Their simulations point in this direction and seem to be robust enough to a wide range of parameters.
But the research also points to the fact that most of the impacts of objects have been on Earth and not on the Moon. The fact that the Moon is filled out of craters and not the Earth is due to the fact Earth has atmosphere, life on its surface and tectonics dynamics, which clear off any footprint of an impact, while the Moon hasn't. Between 9% and 25% of the objects that impact on the Earth-Moon system will do it on the Moon, while the rest on the Earth. This higher number of impacts could be the reason that the Earth has heavy metals on its surface, while the Moon hasn't. When the Earth was being formed, heavy, more dense metals should have gone deeper into the interior of the planet. Metals such as gold or platinum should not be found on its crust. The ones we find could provide from these impacts.
Maybe yes, the gold fever was a lunatics matter.
Physicist, working in quantum optics and nonlinear dynamics in optical systems. Loves to communicate science. | 0.875257 | 3.791079 |
An amateur astronomer in Argentina has done something no scientist has ever been able to do—capture the first burst of light from the supernova explosion of a massive star.
Víctor Buso of Rosario, Argentina, the country's third-most populous city, was testing a new camera on his 16-inch telescope on September 16, 2017. He focused on the spiral galaxy NGC 613, which is approximately 80 million light-years from Earth and can be found within the southern constellation Sculptor.
Although an amateur observer of the night sky, Buso has a lifelong passion for the stars. He was inspired as a child when he saw Neil Armstrong land on the moon in 1969, and the next year he witnessed the Bennett comet fly over the Argentinian. Buso tells the Washington Post that he began building his own telescopes at age 11 using tin cans, magnifying lenses, and Play-Doh. On the night in question, Buso, a 58-year-old locksmith, was using something more advanced: a 40-centimeter telescope housed in an astronomy tower that he built on his roof, affectionately dubbed Observatorio Busoniano.
Taking a series of short-exposure photographs, he noticed a muted point of light. It appeared to be brightening near the end of a spiral arm, previously invisible in the first set of photographs. The speck was just a pixel of light, but a pixel that hadn't appeared in any prior photos. Buso, a self-taught astronomer, hadn't seen anything like it before and, as it turns out, neither had any other astronomer in history.
“I thought, ‘Oh, my God, what is this?’ he tells the Post.
Eventually, his photos found their way to Melina Bersten, an astrophysicist at the Argentine Institute of Astrophysics of La Plata. “We immediately noticed this was an incredibly important discovery,” Bersten says. “Given that we don’t know where and in which moment a supernova is going to explode, it is very easy to lose this very fast early phase.”
“Professional astronomers have long been searching for such an event,” said UC Berkeley astronomer Alex Filippenko, who followed up the discovery with observations and a detailed analysis of the explosion, which is now called SN 2016gkg. “Observations of stars in the first moments they begin exploding provide information that cannot be directly obtained in any other way.”
Scientists estimate that the chances of Buso making the discovery were one in 10 million, possibly one in 100 million. Seeing the very first light of a supernova will allow scientists to better track the explosion throughout its evolution.
“Buso’s data are exceptional,” says Fillppenko. “This is an outstanding example of a partnership between amateur and professional astronomers."
2018 has been a good year for amateur scientists. Earlier this year, an amateur paleontologist discovered some of the most concrete evidence ever seen of early mammals and dinosaurs interacting together.
If you were thinking about buying a telescope and mounting it on your roof, now might be the time. | 0.906324 | 3.597203 |
Greetings, fellow SkyWatchers! What does the weekend have in store for those who observe the starry vistas with their eyes, binoculars, or telescopes? Let’s head out into the night, because the mysteries of the Cosmos await.
Friday, March 28 – For unaided eye observers, the astronomy day starts just before dawn where your challenge is to spot Venus just ahead of the rising Sun. If the horizon is very clear, you might also spot nearby Mercury as well. Now give it a go with binoculars, because there’s more! On this date in 1802, Heinrich W. Olbers discovered the second asteroid, Pallas, while making observations of the position of Ceres. Five years later on this same date in 1807, Vesta – the brightest asteroid and fourth discovered – was identified by Olbers.
Your binocular or small telescope assignment, should you choose to accept it, is to locate Vesta. You’ll find it just a bit south of the union of Uranus, Venus and Mercury about 30 minutes before local dawn. Pallas is too close to the Sun right now for safe viewing. While asteroid chasing is not for everyone, both Vesta and Pallas are often bright enough to be identified with just binoculars. In the coming months, each will rise higher each morning in the predawn sky. Use an online resource to get accurate locator charts and keep a record of spotting these solar system planetoids!
For mid-to-large aperture telescopes, this was indeed a date of discovery as the prolific Sir William found yet another object for future generations to marvel at. Your destination tonight is around a degree east of Alpha Lyncis, and is in the field with a 7th magnitude star in Leo Minor (RA 09 24 18 Dec +34 30 48). It’s name is NGC 2859.
Located about 23 million light-years away, this handsome barred spiral was cataloged on this night in 1786 as H I.137. At around magnitude 11, it’s within reach of average telescopes and the observer will first note its bright core region. But don’t stop there: while there’s nothing unusual about barred structure, this galaxy appears to have a detached halo around it. Often known as the “Ring Galaxy,” this structure could perhaps be caused by gravitational forces reacting with gases along certain points in the bar structure, and so creating a resonance. Oddly enough, each of the four companion galaxies of NGC 2859 contains a compact object or quasar-like phenomenon, and they all have similar redshifts. Be sure to add this “space oddity” to your observing notes!
Saturday, March 29 – Don’t forget to turn off the lights at 8:00 pm to celebrate Earth Hour! For unaided observers, take advantage of the early evening dark skies to enjoy the incredible red triangle of Aldebaran, Betelguese and Mars.
For binoculars and small telescopes, on our list tonight is a Herschel object which lies directly on the galactic equator around five degrees north-northwest of Xi Puppis (RA 07 36 12 Dec -20 37 00). NGC 2421 is a magnitude 8.3 open cluster which will look like an exquisitely tiny “Brocchi’s Cluster” in binoculars; and it will begin to show good resolution of its 50 or so members to an intermediate telescope, in an arrowhead-shaped pattern. It’s bright, it’s fairly easy to find, and it’s a great open cluster to add to your challenge study lists. For the southern observer, try your hand at Sigma Puppis. At magnitude 3, this bright orange star holds a wide separation from its white 8.5 magnitude companion. Sigma’s B star is a curiosity… While it resides at a distance of 180 light-years from our solar system, it would be about the same brightness as our own Sun if placed one Astronomical Unit from Earth!
So what’s special on the agenda for telescopes tonight? Just a discovery – and an extraordinarily beautiful one at that. Two nights ago in 1781, the unsung astronomy hero Pierre Méchain happened on an incredible galaxy in Ursa Major. Located about three fingerwidths northeast of Mizar and Alcor (RA 14 03 13 Dec +54 20 53), this near 8th magnitude galaxy was added as one of the last on the Messier list, but it ranks as one of the first to be identified as a spiral. While M101 is huge and bright, binoculars will only spot the bright central region – yet the average beginner’s scope (114mm) will begin to reveal arm structure with aversion. As aperture increases, so does detail, and some areas are so bright that Herschel assigned them their own catalog numbers. Even Halton Arp noted this one’s lopsided core as number 26 (“Spiral with One Heavy Arm”) on his peculiar galaxies list.
At a distance of 27 million light-years, M101 might be somewhat disappointing to smaller scopes, but photographs show it as one of the most fantastic spirals in the Cosmos. Dubbed the “Pinwheel,” it heads up its own galactic group consisting of NGC 5474 to the south-southeast and NGC 5585 to the northeast, which are visible to larger scopes. It is estimated there may be as many as six more members as well! Be sure to take the time to really study this galaxy. The act of sketching often brings out hidden details and will enrich your observing experience.
Sunday, March 30 – If you’re out late or up before sunrise, be sure to take a look at the Moon and Jupiter making a pleasing pairing along the ecliptic. No special equipment is needed!
Take your telescopes or binoculars out tonight and look just north of Xi Puppis (RA 07 44 36 Dec -23 52 00) for a “mass concentration” of starlight known as M93. Discovered in March of 1781 by Charles Messier, this bright open cluster is a rich concentration of various magnitudes which will simply explode in sprays of stellar fireworks in the eyepiece of a large telescope. Spanning 18 to 22 light-years of space and residing more than 3400 light-years away, it contains not only blue giants, but lovely golds as well. Jewels in the dark sky…
As you view this cluster tonight, seize the moment to remember Messier, because this is one of the last objects he discovered personally. He described it as “A cluster of small stars without nebulosity” – but did he realize the light he was viewing at the time left the cluster during the reign of Ramses III? Ah, yes…sweet time. Did Charles have a clue this cluster of stars was 100 million years old? Or realize it was forming about the time Earth’s land masses were breaking up, dinosaurs ruled, and the first mammals and birds were evolving? Although H. G. Wells “Time Machine” is a work of fiction, each time we view through a telescope we take a journey back across time itself. Enjoy the mystery! | 0.927604 | 3.766214 |
Most cosmologists believe our universe is filled with strange invisible stuff that exerts a powerful gravitational force on a galactic scale. This force stops galaxies from tearing themselves apart as they rotate.
But so-called dark matter ought to have other effects. Earth, for example, must by swimming in a huge ocean of dark matter. And from time to time, a lump of it ought to smash into visible matter, leaving a telltale sign that we ought to be able to detect, such as vibrations that increase the temperature by a small amount.
Physicists are engaged in a multibillion-dollar race to detect these effects. The winner—the putative discoverer of dark matter—is set to win the kind of scientific fame and fortune that only a few scientists ever enjoy.
This search has led others to think about the possible effects of dark matter too, and earlier this year Konstantin Zioutas from the University of Patras in Greece and Edward Valachovic at the State University of New York at Albany published their theory in the journal Biophysical Research Letters.
These guys studied the rates of skin cancer in the US between 1973 and 2011 and found an unexplained annual periodicity and a much shorter 88-day periodicity. In other words, the rate of skin cancer diagnosis varies in regular annual cycles and in regular 88-day cycles. That’s a curious observation.
But even stranger is the idea Zioutas and Valachovic put forward to explain it. These guys’ theory is that dark matter causes skin cancer by damaging the DNA it bumps into. They go on to say that the sun and planets can focus dark matter as they move through it. And whenever Earth passes through one of these focused streams of dark matter, skin cancer rates rise.
The icing on this theoretical cake is that the observed periodicities exactly match the orbital periods of Earth and Mercury, so all the pieces fall neatly into place.
That’s an extraordinary claim and, of course, one that requires extraordinary evidence.
Today, Hector Socas-Navarro at the Instituto de Astrofísica de Canarias in the Canary Islands, Spain, cast a critical eye over this theory. His withering conclusion is that it is not consistent with the evidence or known science. And this analysis provides an interesting and important prism through which to see the process of science at work.
Socas-Navarro begins with a brief discussion of the basic features that dark matter seems to have (it is itself a hypothesis, of course). For a start, dark matter appears to be more uniformly distributed on interstellar scales than visible matter. “The amount of dark matter mass contained in the solar system is estimated to be comparable to that of a large asteroid,” he says. That’s why it is only important on galactic scales.
But if dark matter is uniformly distributed, it ought to be sweeping through our bodies at speeds of hundreds of kilometers per second as Earth moves through space. It is certainly conceivable that particles of dark matter could collide with human DNA from time to time and even trigger mutations.
But there is significant uncertainty in this kind of thinking. “Given our present lack of knowledge on the [dark matter] properties, it is not possible to estimate the rates of collisions or mutations produced by these particles,” says Socas-Navarro.
Neither is it possible to work out how these rates might vary over time. There is certainly a possibility that the density of dark matter Earth passes through might vary over time scales of tens of millions of years. But Zioutas and Valachovic envisage a scenario in which the motion of planets changes this density. Socas-Navarro valiantly tries to imagine how this might happen.
He imagines that there is a stream of dark matter that Mercury passes in and out of during its orbit round the sun. During each of these orbits, Mercury somehow focuses dark matter toward Earth, and this raises the rate of skin cancer diagnosis.
For this to work, Mercury must dive into this stream at the same point during each orbit over the last 38 years. So the stream of dark matter must have a scale that is comparable with Mercury’s orbit, which is 58 million kilometers across.
But Socas-Navarro cannot ignore the motion of the sun in this model. It moves through the galaxy at a rate of 200 kilometers per second and so has traveled several trillion kilometers through this dark-matter stream in the last 38 years. “This mismatch of several orders of magnitude between both distances makes it nearly impossible to construct a suitable geometrical scenario,” says Socas-Navarro. The sun’s motion could, of course, be exactly aligned with the stream over many trillions of kilometers, but this would be a remarkable and unlikely coincidence.
Then there is the motion of Earth. Even if Mercury were periodically diving in and out of this stream and focusing dark matter toward us, the position of Earth would be different each time. This makes the observed 88-day skin cancer periodicity almost impossible to match with Mercury’s orbital period.
So from an astrophysical point of view, Zioutas and Valachovic’s theory seems doomed.
But the theory suffers from some unfortunate medical shortcomings too. For example, the data set records the time of diagnosis, not the time when the skin cancer begins or when patients first notice symptoms. Various studies show that the time elapsed between first noticing symptoms and receiving a diagnosis is about seven to 11 months.
That kind of variation is hard to reconcile with the dark matter theory. “Diagnosis delay is an important problem in medicine and it would smear out any possible periodic signal that could have existed,” says Socas-Navarro.
Perhaps most damning is the apparent immunity of the black population to skin cancer caused by dark matter. Socas-Navarro points out that skin pigmentation is a well-known protective factor against ultraviolet radiation and skin cancer. “However, there is no known reason why it should protect against dark matter,” he says.
And yet the data shows that the rate of skin cancer in the black population is much lower and does not follow the same periodicities as the white population. Again, that is hard to reconcile with the dark matter theory. “There is no known reason why a darker skin should make people immune to dark matter,” says Socas-Navarro.
Clearly, the evidence is not consistent with the idea that dark matter causes skin cancer.
So what might explain the periodicities observed by Zioutas and Valachovic? “The one-year period and its harmonics found in most types of cancer are probably a direct consequence of our medical examination habits,” says Socas-Navarro. In other words, annual periodicities are probably linked to the fact that people tend to get annual health check-ups.
However, the 88-day periodicity, and another at 70 days that Socas-Navarro points out, remain unexplained.
That’s interesting work by Socas-Navarro who maintains a dignified loyalty to scientific inquiry throughout his paper. Indeed, that’s exactly how science should work: by observation, hypothesis, testing, and rechecking against nature.
Left-field ideas are an important part of the scientific firmament. They are often wrong. But every now and again, they revolutionize our understanding of the universe.
But the way to tell the difference is not through faith or ridicule or aggression or even wishful thinking, but through the process of evidence-based science. Long may it flourish.
Ref: arxiv.org/abs/1812.02482 : On The Connection Between Planets, Dark Matter | 0.918472 | 4.020273 |
You’re looking at an insanely beautiful image of the Cygnus Loop nebula captured by NASA’s Galaxy Evolution Explorer (GALEX) mission. Furthermore, this isn’t viewed in plain old visible light, this is high-energy ultraviolet light, revealing regions of hot gas remaining after a supernova detonated here 5,000 to 8,000 years ago.
In fact, the original supernova would have been bright enough to be visible with the unaided eye.
The Cygnus Loop Nebula, also known as W78 or Sharpless 103, is a huge emission nebula measuring more than 3° across. There are many smaller features inside the complex, like the Veil Nebula, the Western Veil (the Witch’s Broom), Eastern Veil and Pickering’s Triangle. Many will be familiar to astronomers and astrophotographers as they’re large and faint, and can only really be revealed with long exposure images in various narrowband filters.
Astronomers originally believed it was located about 2,500 light-years away, but according to newer research with the Hubble Space Telescope, they’ve pegged its distance at only 1,470 light-years away; and it now stretches across a distance of 90 light-years.
This extremely close distance is important. There are many supernova remnants like this, scattered across our galaxy, but none are so close, taking up such a vast region of our skies.
This view was captured by NASA’s GALEX mission, which launched in April 2003. Its main purpose was to image hundreds of thousands of galaxies, charting their rates of star formation – the science is best gathered in ultraviolet. Unfortunately, NASA cut off financial support for the mission back in February, 2011, but control might be transferred to the California Institute of Technology.
Original Source: NASA/Galex News Release | 0.843938 | 3.398008 |
In this beautiful VIS image, taken by the NASA - Mars Odyssey Orbiter on June, 2nd, 2003, and during its 6.500th orbit around the Red Planet, we can see a small portion of the Floor - as well as of the Terrain - surrounding the extremely old and irregularly-shaped Müller Crater, an Impact Crater located in the Martian Region known as Terra Cimmeria.
Müller Crater has a diameter of approx. 120,5 Km (such as about 74,8305 miles), is located in the Martian Southern Hemisphere, centeerd at 25.74° South Latitude, and 127.89° East Longitude, and it is found in the Mare Tyrrhenum Quadrangle of Mars. According to the International Astronomical Union's Working Group for Planetary System Nomenclature, Müller Crater was - jointly - named after Hermann Joseph Muller, an American Geneticist and Anti-Nuclear Weapons Activist, and Carl H. Müller, a German Astronomer.
Just out of curiosity, you should know that the Ejecta coming from Müller Crater divides two Drainage Basins which, according to Planetary Scientists, belong to the Noachian Era of Mars.
Latitude (centered): 25,899° South
Longitude (centered): 127,662° East
This image (which is an Original Mars Odyssey Orbiter falsely colored and Map-Projected frame published on the NASA - Planetary Photojournal with the ID n. PIA 19266) has been additionally processed, magnified to aid the visibility of the details, contrast enhanced and sharpened, Gamma corrected and then re-colorized in Absolute Natural Colors (such as the colors that a normal human eye would actually perceive if someone were onboard the NASA - Mars Odyssey Orbiter and then looked down, towards the Surface of Mars), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. | 0.867027 | 3.273751 |
The Dawn spacecraft is healthy and on course for its flyby of Mars early next year. The planet’s gravity will help boost the probe on its way to rendezvous with Vesta. While the spacecraft has its sights set on the asteroid belt (via Mars), its path is now bringing it closer to Earth. Meanwhile, from Earth’s perspective, Dawn appears to be approaching a blindingly close encounter with the Sun. With so much happening in the solar system, all readers, whether local or not, are invited to turn their attention here.
In the last log, we saw that Dawn was nearing the end of an extended period of thrusting with is ion propulsion system that began on December 17, 2007. When it left Earth on September 27, 2007, the Delta II rocket deposited the spacecraft into a carefully chosen orbit around the Sun. By October 31, 2008, the spacecraft had completed the thrusting it needed to change that orbit so it would encounter Mars at just the right time, location, and angle to sling it on its way to Vesta. During this interplanetary cruise phase, Dawn thrust for 270 days, or 85% of the time. Expending less than 72 kilograms (158 pounds) of xenon propellant, the spacecraft changed its speed by about 1.81 kilometers per second (4050 miles per hour).
Although controlling an interplanetary probe across hundreds of millions of kilometers (or miles) of deep space and guiding it accurately enough to reach its remote destination seems as if it should be a very simple task, readers may be surprised to know that it is not. Let’s consider just one aspect of the problem.
Suppose you want to shoot an arrow at a target. Unlike typical archers, you are so far from the target that you can only barely see it. In that case, aiming for the bull’s-eye is essentially out of the question. Adding to the problem may be a variable breeze that could nudge the arrow off course. Shooting sufficiently accurately to get the arrow even to the vicinity of the target would be challenging enough; hitting the precise point you want on the target is just too difficult.
For readers who are principally interested in archery, this concludes our in-depth analysis of the sport.
Now let’s consider how to change the situation to make it more similar to an interplanetary mission. If the arrow had a tiny radio locator mounted on it, you would be able monitor its progress as it flew closer to the target. This would be like watching it on a radar screen. You might see your arrow miss the target entirely or, if you had made a particularly good shot, hit somewhere on it. Now if you could occasionally send a signal to the arrow, perhaps to change the angles of the feathers, you might not be able to alter its course drastically, but you could change it a little. So if your initial shot had been good enough, you could guide the arrow to the desired destination. (To buy your radio controlled archery set, visit the Dawn gift shop on your planet. The set may be found between the display case with xenon ion beam jewelry and the shelves and shelves and shelves and shelves of really cool new Dawn Journal reader action figures -- be sure to buy the one that looks just like you!)
Shooting the arrow is akin to launching a spacecraft, and its flight to the target represents the interplanetary journey, although operating a spacecraft involves far greater precision (and fun!). Our knowledge of where the spacecraft is and where it is heading is amazingly, fantastically, incredibly accurate, but it is not perfect. This point is essential. Keeping most spacecraft on course is a matter of frequently recalculating the position, speed, and direction of travel and then occasionally fine-tuning the trajectory through burns of the propulsion system.
Dawn’s near-constant use of its advanced ion propulsion system for most of 2008 changes the story, but only a little. The thrust plan was calculated before launch and then updated once our arrow was free of the bow. Throughout the interplanetary cruise phase, a new thrust plan was transmitted to the spacecraft about every 5 weeks, each time with slight updates to account for the latest calculations of Dawn’s orbit around the Sun. With this method, the small adjustments to the trajectory have been incorporated into the large, preplanned changes.
The mission control team requires about 5 weeks to design, develop, check, double-check, transmit, and activate a 5-week set of commands. By the time the spacecraft is executing the final part of those instructions, it is following a flight plan that is based on information from 10 weeks earlier. During most of the mission, when there are months or even years of thrusting ahead of it, subsequent opportunities to adjust the trajectory are plentiful. In contrast, for the last period of preplanned thrusting before Mars, controllers modified their normal process for formulating the commands, making a fast update for the final few days of thrusting. By including the latest navigational data in the computations for the direction and duration of the concluding segment of powered flight, the mission control team put Dawn on a more accurate course for Mars than it otherwise would have been.
Even with this strategy, navigators recognized long ago that subsequent adjustments would be required. The plan for approaching Mars has always included windows for trajectory correction maneuvers (which engineers are physiologically incapable of calling anything other than TCMs). Dawn’s first TCM occurred on November 20.
As navigators refined their trajectory calculations after thrusting finished on October 31, they determined that the spacecraft was quite close to the aim point they wanted, but still not exactly on target. In fact, rather than being on a course to sail a few hundred kilometers above Mars, the probe’s path would have taken it to the surface of the planet. Despite the power of the ion propulsion system, Dawn does not have the capability to bore through the rocky planet and continue on its way to Vesta.
Such a situation is not surprising. Suppose in the archery, the bull’s-eye were 30 centimeters (1 foot) in diameter, but we preferred to hit a point 2.2 centimeters (7/8 inch) outside the bull’s-eye, near the 11:00 position (corresponding to where we want Dawn to fly past Mars). As our arrow approached the target, it might turn out that it was going to miss the target entirely, it might be headed for some other point on the target, and it just might be that it was headed for the bull’s-eye itself. Dawn’s case was this last one, so TCM1 put it on track for the destination we desired.
Amazing sports analogies for the fantastic accuracy of interplanetary navigation usually fail to account for TCMs, as most arrows, balls, and other projectiles do not include active control after they are on their way. Your correspondent has presented his own simile for the astonishing accuracy with which a spacecraft can reach a faraway destination, but most such analogies neglect TCMs, without which deep-space missions could not be accomplished. (Note that the accuracy is impressive with or without TCMs. We shall extend our archery example in a future log, making it more quantitative. It will be important, however, to keep in mind that the ion propulsion system provides so much maneuvering flexibility that Dawn does not need to achieve the degree of accuracy in its gravity assist that a mission using conventional chemical propulsion might.)
For reasons we will not divulge, Dawn’s first TCM has been designated TCM1. On November 20, just as it had for all of its previous thrusting, the spacecraft pointed a thruster (TCM1 used thruster #1) in the required direction and resumed emitting the familiar blue-green beam of xenon ions to alter course. While typical thrusting during the mission has lasted for almost 7 days at a time (followed by a hiatus of 7 to 8 hours), in this case only a short burn was necessary. Propelling itself from about 4:31 pm to 6:42 pm PST was just enough to fine-tune its course and change its speed by a bit more than 60 centimeters per second (1.3 miles per hour). This adjustment was modest indeed, as at that time Dawn was traveling around the Sun at more than 22.5 kilometers per second (50,400 miles per hour). Dawn and Mars, following their separate orbits that will (almost!) intersect on February 17, 2009, were moving relative to each other at 3.17 kilometers per second (7100 miles per hour).
Dawn’s second TCM window (inexplicably named TCM2) is in January. Traveling two-thirds of the way from here to Mars, the navigational accuracy then will be still better, with smaller deviations from the planned target point being detectable, so another refinement in the trajectory then is likely. In the meantime, Dawn will follow its orbital path with its ion thrusters idle.
As Dawn travels through space on its own, its path has been essentially independent of Earth’s. We saw in a previous log that the weaker grasp exerted by the Sun at Dawn’s greater distance means that it travels more slowly around the solar system. While Earth has completed more than 1 full revolution (each revolution requiring 1 year) since launch, Dawn has not yet rounded the Sun once. After receding from the Sun until early August, the spacecraft began falling back, albeit only temporarily.
The probe attained its maximum distance from Earth on November 10. (For anyone who was on Earth on that date and plans to use this information in an alibi, it may be helpful to know that the greatest range was reached at about 3:07 am PST.) The spacecraft was more than 384 million kilometers (239 million miles) from its one-time home. Although it will make substantial progress on its journey in the meantime, Dawn’s distance to Earth will continue to decrease until January 2010, when it will be less than one-third of what it is today. In the summer of that year, however, as Earth maintains its repetitive annual orbital motion and the explorer climbs away from the Sun, it will surpass this month’s distance to Earth. (Readers are encouraged to memorize the contents of this log for reference in 2010 in case we fail to include a link to this paragraph.)
The complex choreography of the solar system’s grand orbital dance rarely calls for a circular orbit; rather, the dancers follow ellipses (ovals in which the ends are of equal size) around the Sun. Thanks to the details of the shapes of their orbits, the greatest separation between Earth and Dawn did not occur when they were precisely on opposite sides of the Sun, although the alignment was close to that.
On December 12, their dance steps will take them to points almost exactly on opposite sides of the Sun. For observers on Earth, this is known as solar conjunction, because the spacecraft and the Sun will appear to be in the same location. (Similarly, from Dawn’s point of view, Earth and the Sun will be almost coincident.) In reality, of course, Dawn will be much farther away than Earth’s star. It will be 147 million kilometers (91.5 million miles) from Earth to the Sun but 379 million kilometers (236 million miles) from the planet to its cosmic envoy.
Its apparent proximity to the Sun presents a helpful opportunity for terrestrial readers to locate Dawn in the sky. On December 9 - 15, the spacecraft will be less than 1 degree from the Sun, progressing from east to west and passing just 1/3 degree south of that brilliant celestial landmark on December 12. (As Dawn does not orbit in the same plane as Earth, it will not pass directly behind the Sun.) The Sun itself is 1/2 degree across, so this is close indeed; the spacecraft will sneak in to less than 1 solar diameter from the disk. To demonstrate how small the separation is, if you blocked the Sun with your thumb at arm’s length during this week around conjunction (and you are exhorted to do so), you also would cover Dawn.
For those interested observers who lack the requisite superhuman visual acuity to discern the remote spacecraft amidst the dazzling light of the Sun, conjunction still may provide a convenient occasion to reflect upon this most recent of humankind’s missions far into the solar system. This small probe is the product of creatures fortunate enough to be able to combine their powerful curiosity about the workings of the cosmos with their impressive abilities to explore, investigate, and ultimately understand. While its builders remain in the vicinity of the planet upon which they evolved, their robotic ambassador now is passing on the far side of the extraordinarily distant Sun. This is the same Sun that has been the unchallenged master of our solar system for 4.5 billion years. This is the same Sun that has shone down on Earth throughout that time and has been the ultimate source of so much of the heat, light, and other energy upon which the planet’s inhabitants have been so dependent. This is the same Sun that has so influenced human expression in art, literature, and religion for uncounted millennia. This is the same Sun that has motivated scientific studies for centuries. This is the same Sun that acts as our signpost in the Milky Way galaxy. This is the same Sun that is more than 100 times the diameter of Earth and a third of a million times the planet’s mass. And humans have a spacecraft on the far side of it. We may be humbled by our own insignificance in the universe, yet we still undertake the most valiant adventures in our attempts to comprehend its majesty.
Solar conjunction means even more to Dawn mission controllers than the opportunity to meditate upon what magnificent feats our species can achieve. As Earth, the Sun, and the spacecraft come closer into alignment, radio signals that go back and forth must pass near the Sun. The solar environment is fierce indeed, and it causes interference in those radio waves. While some signals will get through, communications will be less reliable. Therefore, controllers plan to send no messages to the spacecraft from December 5 through December 18; all instructions needed during that time will be stored onboard beforehand. Deep Space Network antennas, pointing near the Sun, will listen through the roaring noise for the faint whisper of the spacecraft, but the team will consider any signals to be a bonus.
There is plenty of other work to do while waiting to resume communications after conjunction. In addition to preparing for the visit to Mars, engineers will continue to interpret the results of election day. On November 4, the Dawn team voted unanimously for more power. They commanded the spacecraft to execute a set of steps to yield data that will reveal the full potential of the enormous solar arrays to generate electrical power. The method was tested first on July 21, and then refined for a test on September 22. For this month’s measurement, the commands were identical to those used for the second test with one exception that had been planned from the beginning: the solar arrays were rotated to point 60 degrees away from the Sun instead of 45 degrees. The solar arrays are so powerful that when they are pointed directly at the Sun, the spacecraft could not draw enough power to measure their full capability.
The data collected show the electrical behavior of the arrays as the ion propulsion system was commanded through its start-up, drawing more and more power. Unlike the two tests, this calibration was designed so that with the arrays pointed so far from the Sun, they would not be able to provide as much power as was requested. Engineers wanted to find the point at which the arrays would no longer be able to satisfy the demands. They were not disappointed; power climbed up and up until no more was available. The prospect of having a spacecraft not be able to meet its own power demands may seem risky, but the procedure was carefully designed, analyzed, and simulated, and it executed perfectly. When the ion propulsion system asked for more power than the arrays could deliver, in the language of the trade, the solar arrays “collapsed.” Now to some (including even some engineers unfamiliar with the terminology), this suggests something not entirely desirable, such as 2 bent and twisted wings, each with 5 warped panels, and 11,480 shattered solar cells, the fragments sparkling in the sunlight as they tumbled and floated away from the powerless probe. In this case though, “collapse” is an electrical, not a mechanical, phenomenon and hence would be somewhat less visually spectacular and quite reversible -- a key attribute for a mission with well over 6 years of space exploration ahead of it. Once all the data are analyzed, controllers will have a better prediction for how much power the arrays will be able to generate for the rest of the voyage.
Dawn is 20 million kilometers (12 million miles) from Mars. It is 383 million kilometers (238 million miles) from Earth, or 950 times as far as the moon and 2.59 times as far as the Sun. Radio signals, traveling at the universal limit of the speed of light, take 43 minutes to make the round trip.
Dr. Marc D. Rayman
7:00 am PST November 26, 2008 | 0.844739 | 3.69603 |
Extreme astrophysical events such as relativistic flows, cataclysmic explosions and black hole accretion are a key area for astrophysics in the 21st century. The extremes of physics, density, temperature, pressure, velocity, gravitational and magnetic fields experienced in these environments are beyond anything achievable in any laboratory on Earth, and provide a unique glimpse at the laws of physics operating in extraordinary regimes.
Nearly all such events are associated with transient radio emission, a tracer of the acceleration of particles to relativistic energies and their interaction with the local magnetic field. By studying radio bursts from these phenomena we can pinpoint the sources of explosive events, probe relativistic accretion, and understand the budget of kinetic feedback by such events in the ambient medium. The combination of a wide field of view, wide frequency coverage with sub-band capabilities and excellent sensitivity makes MeerKAT the most powerful southern hemisphere radio telescope to study the transient sky.
ThunderKAT on MeerKAT will tackle all aspects of transient emission associated with accretion and explosive events. Through a comprehensive and complementary programme of surveying and monitoring Galactic synchrotron transients (across a range of compact accretors and a range of other explosive phenomena) and exploring distinct populations of extragalactic synchrotron transients (microquasars, supernovae and possibly yet unknown transient phenomena) – both from direct surveys and commensal observations – we will revolutionise our understanding of the dynamic and explosive transient radio sky | 0.878396 | 3.654064 |
The Rosette Nebula (NGC 2237, Caldwell 49) in Monoceros is a showpiece astrophotography object for telescopes of any size, resembling a large open flower with an open cluster of stars (NGC 2244, Caldwell 50) in the darker center. It lies about 5,200 light years away and is 130 light years across. The stellar winds from these young, hot stars are clearing the center portion of the nebula, but their ultraviolet radiation is so strong that it still causes the rest of the nebula to glow. Initially, 36 stars were identified to make up the cluster, but Chandra space telescope X-Ray data increase that number to about 160 stars and showed that this is a place of new star formation from all the dust and gas. Note the huge, dark spires of dust projecting toward the center of the Rosette.
A wide-field system is needed to show the full extent of the Rosette. This is a close-up view showcasing the central structures. Narrowband filters were used to bring out the amazing central structures with a total of 25 hours of exposures. The Hubble Color Palette was used where oxygen (OIII), hydrogen (H-a), and sulfur (SII) were mapped to blue, green and red, respectively, in the same way the famous “Pillars of Creation” image was processed. As such, we describe this image as “false color”. An additional 2.5 hours of RGB data were used to provide natural star color, especially to show the intensely beautiful open cluster.
I wish to thank my observatory partner, Chris Purves, for collecting the data and letting me process them. | 0.853078 | 3.286819 |
Line Topics Small Bodies of the Solar System
NASA was responsible for the mission. The launch date was September 27, 2007. And the end of mission is due in July 2015. The Dawn mission was selected by NASA December 21, 2001 as part of the Discovery Program, with the aim to observe the asteroids Vesta and Ceres.
After the launch in September 27, 2007, the spacecraft performed a maneuver gravity assist with Mars in February 2009 to head towards Vesta and reach it in August 2011.
Following the racking in its orbit, the spacecraft has studied Vesta until May 2012 and then head to the time of Ceres, which will be reached in February 2015. The spacecraft will orbit around Ceres until July 2015.
The mission is ideally placed in between the exploration of the inner solar system rocky and gaseous outer Solar System. Complete the exploration of the inner solar system being complementary to current missions and future of Mercury, Venus, Earth and Mars; in particular, allow you to better understand the role and the importance of water in planetary evolution. The main scientific objectives of the mission are: the collection of information on the conditions that prevailed during the early stages of the evolution of the solar system, or on the first million years of evolution, and on the processes taking place on the bodies just formed; the characterization of the “building blocks” from which are formed the terrestrial planets, thus increasing our knowledge of this process of formation.
Ceres is very primitive and retains traces of water, unlike other minor planets, could also have an atmosphere subtle but permanent. Instead of Ceres, Vesta is evolved and dry, is the only asteroid that has obvious signs of a complex and thermal evolution similar to that of the terrestrial planets, with the presence of volcanism.
This spectacular image of comet Tempel 1 was taken 67 seconds after it obliterated Deep Impact’s impactor spacecraft.
To achieve its scientific objectives, Dawn will characterize asteroids observed in terms of shape and physical properties (size, shape, mass, time and rotation axis), morphological (local structures, distribution of craters, the presence or absence of regolith), geological and mineralogical nature of the surface, presence or absence of dust and / or gases.
The Italian participation in the mission is the provision of: an imaging spectrometer operating in the visible and near-infrared high spatial and spectral resolution to make the hyperspectral mapping of the asteroids: VIR-MS “Visible-IR Mapping Spectrometer”, derived from the VIRTIS instrument aboard the Rosetta mission, is under the responsibility PI Angioletta Coradini (INAF / IFSI) and was built by the industrial prime contractor Galileo Avionica, manpower to Dawn Project Team at JPL / UCLA for transactions in flight.
We will present some of the International Agreements. On 19 December 2003, was formalized the partnership between ASI and NASA for the realization of the Dawn mission through the signing of a Letter of Agreement. Subsequently, we signed a Memorandum of Understanding between NASA and ASI, which came into force on 6 July 2007. | 0.879121 | 3.793014 |
This laboratory is an activity for you to analyze an astronomical situation. While it is part of the astronomy course principles of radiation astronomy, it is also independent.
Astronomical analysis is the detailed examination of the elements or structure of some astronomical thing (an entity, source, or object), typically as a basis for discussion or interpretation.
Once an astronomical situation has been selected, it must be separated into its constituent elements, for example, the identification and measurement of the chemical constituents of a substance or specimen.
You may choose an astronomical situation to dissect.
I will provide one example of this process. Provide any questions you may have on the discussion page.
A control group for astronomical analysis may be found in any astronomy article. It is likely to consist of
- an aim, or objective, of an investigation of an astronomical situation or event.
- a method, or approach, to hopefully solve or resolve the situation, or understand the event.
- a comparison with various astronomical models, usually two.
- drawing one or more, or some conclusions.
- choosing which model seems to work best.
Analytical X-ray astronomyEdit
"High-mass X-ray binaries (HMXBs) are composed of OB supergiant companion stars and compact objects, usually neutron stars (NS) or black holes (BH). Supergiant X-ray binaries (SGXBs) are HMXBs in which the compact objects orbit massive companions with orbital periods of a few days (3–15 d), and in circular (or slightly eccentric) orbits. SGXBs show typical the hard X-ray spectra of accreting pulsars and most show strong absorption as obscured HMXBs. X-ray luminosity (Lx) increases up to 1036 erg·s−1 (1029 watts)."
"Aim: use the discovery of long orbits (>15 d) to help discriminate between emission models and perhaps bring constraints on the models."
"Method: analyze archival data on various SGXBs such as has been obtained by INTEGRAL for candidates exhibiting long orbits. Build short- and long-term light curves. Perform a timing analysis in order to study the temporal behavior of each candidate on different time scales."
"Compare various astronomical models:
- direct spherical accretion
- Roche-Lobe overflow via an accretion disk on the compact object."
Draw some conclusions: for example, the SGXB SAX J1818.6-1703 was discovered by BeppoSAX in 1998, identified as a SGXB of spectral type between O9I−B1I, which also displayed short and bright flares and an unusually very low quiescent level leading to its classification as a SFXT. The analysis indicated an unusually long orbital period: 30.0 ± 0.2 d and an elapsed accretion phase of ~6 d implying an elliptical orbit and possible supergiant spectral type between B0.5-1I with eccentricities e ~ 0.3–0.4. The large variations in the X-ray flux can be explained through accretion of macro-clumps formed within the stellar wind.
Choose which model seems to work best: for SAX J1818.6-1703 the analysis best fits the model that predicts SFXTs behave as SGXBs with different orbital parameters; hence, different temporal behavior.
Now it's your turnEdit
The external links below will help you to find an article of interest. Read the article to look for where and how the authors resolved a situation using observational experiments.
Outline their approach and method per the control group above or compose your own.
- A successful way to teach analysis in astronomy is through learning by doing.
- Marshallsumter (April 15, 2013). X-ray astronomy. San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2013-05-11.
- Zurita Heras JA, Chaty S (2009). "Discovery of an eccentric 30 day period in the supergiant X-ray binary SAX J1818.6–1703 with INTEGRAL". Astronomy and Astrophysics 493 (1): L1. doi:10.1051/0004-6361:200811179.
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Milky Way's origins are not what they seem
In a first-of-its-kind analysis, Northwestern University astrophysicists have discovered that, contrary to previously standard lore, up to half of the matter in our Milky Way galaxy may come from distant galaxies. As a result, each one of us may be made in part from extragalactic matter.
Using supercomputer simulations, the research team found a major and unexpected new mode for how galaxies, including our own Milky Way, acquired their matter: intergalactic transfer. The simulations show that supernova explosions eject copious amounts of gas from galaxies, which causes atoms to be transported from one galaxy to another via powerful galactic winds. Intergalactic transfer is a newly identified phenomenon, which simulations indicate will be critical for understanding how galaxies evolve.
"Given how much of the matter out of which we formed may have come from other galaxies, we could consider ourselves space travelers or extragalactic immigrants," said Daniel Anglés-Alcázar, a postdoctoral fellow in Northwestern's astrophysics center, CIERA (Center for Interdisciplinary Exploration and Research in Astrophysics), who led the study. "It is likely that much of the Milky Way's matter was in other galaxies before it was kicked out by a powerful wind, traveled across intergalactic space and eventually found its new home in the Milky Way."
Galaxies are far apart from each other, so even though galactic winds propagate at several hundred kilometers per second, this process occurred over several billion years.
Professor Claude-André Faucher-Giguère and his research group, along with collaborators from the FIRE ("Feedback In Realistic Environments") project, which he co-leads, had developed sophisticated numerical simulations that produced realistic 3-D models of galaxies, following a galaxy's formation from just after the Big Bang to the present day. Anglés-Alcázar then developed state-of-the-art algorithms to mine this wealth of data and quantify how galaxies acquire matter from the universe.
The study, which required the equivalent of several million hours of continuous computing, will be published July 26 (July 27 in the U.K.) by the Monthly Notices of the Royal Astronomical Society.
"This study transforms our understanding of how galaxies formed from the Big Bang," said Faucher-Giguère, a co-author of the study and assistant professor of physics and astronomy in the Weinberg College of Arts and Sciences.
"What this new mode implies is that up to one-half of the atoms around us—including in the solar system, on Earth and in each one of us—comes not from our own galaxy but from other galaxies, up to one million light years away," he said.
By tracking in detail the complex flows of matter in the simulations, the research team found that gas flows from smaller galaxies to larger galaxies, such as the Milky Way, where the gas forms stars. This transfer of mass through galactic winds can account for up to 50 percent of matter in the larger galaxies.
"In our simulations, we were able to trace the origins of stars in Milky Way-like galaxies and determine if the star formed from matter endemic to the galaxy itself or if it formed instead from gas previously contained in another galaxy," said Anglés-Alcázar, the study's corresponding author.
In a galaxy, stars are bound together: a large collection of stars orbiting a common center of mass. After the Big Bang 14 billion years ago, the universe was filled with a uniform gas—no stars, no galaxies. But there were tiny perturbations in the gas, and these started to grow by force of gravity, eventually forming stars and galaxies. After galaxies formed, each had its own identity.
"Our origins are much less local than we previously thought," said Faucher-Giguère, a CIERA member. "This study gives us a sense of how things around us are connected to distant objects in the sky."
The findings open a new line of research in understanding galaxy formation, the researchers say, and the prediction of intergalactic transfer can now be tested. The Northwestern team plans to collaborate with observational astronomers who are working with the Hubble Space Telescope and ground-based observatories to test the simulation predictions.
The simulations were run and analyzed using the National Science Foundation's Extreme Science and Engineering Discovery Environment supercomputing facilities, as well as Northwestern's Quest high-performance computer cluster.
The study is titled "The Cosmic Baryon Cycle and Galaxy Mass Assembly in the FIRE Simulations." | 0.861595 | 4.018028 |
Friday, July 12
• The Moon this evening forms a triangle with Jupiter to its lower left and Antares under it, as shown above.
• Jupiter’s Great Red Spot should cross the planet’s central meridian around 11:08 p.m. Eastern Daylight Time. For the full schedule of this month’s Red Spot transits, good worldwide, see the July Sky & Telescope, page 50.
Saturday, July 13
• The Moon and Jupiter cross the sky together tonight, as shown above. During this month’s pairup of the two, Jupiter is 1,700 times farther than the Moon. In actuality the Moon is roughly the size of Jupiter’s own four Galilean moons, mere pinpoints as seen in a small scope or with good, steadily braced binoculars. This evening for North America, all four appear on Jupiter’s celestial west side relatively close to the planet.
Sunday, July 14
• Now the Moon shines between Jupiter and Saturn, as shown above. Notice how steadily the two planets glow compared to twinkly bright stars.
Monday, July 15
• The Moon accompanies Saturn across the sky tonight, as shown above. They appear just 2° or 3° apart for North America. Saturn is currently 3,400 times farther than the Moon — twice as distant as Jupiter.
Tuesday, July 16
• Full Moon (exact at 5:38 p.m. EDT). A partial lunar eclipse is visible from most of the world’s continents except North America. Map, timetable, and full details.
For us in North America, the full Moon shines on just as normal as can be, about 10° east of Saturn.
Wednesday, July 17
• High in the northwest after dark, the Big Dipper has started its long, slow scoop toward the right. Lower in the north-northeast, meanwhile, the upright W of Cassiopeia has slowly begun to tilt and climb.
Thursday, July 18
• Week by week, bright Arcturus is losing some of its height in the west after dark.
Look for Spica to the lower left of Arcturus by about three fists at arm’s length. Lower right of Arcturus by the same amount is Denebola, the tailtip of Leo. These three stars form an almost perfect equilateral triangle.
Friday, July 19
• The tail of Scorpius is low due south after dark, as shown above. How low depends on how far north or south you live: the farther south, the higher.
Look for the two stars especially close together in the tail. These are Lambda and fainter Upsilon Scorpii, known as the Cat’s Eyes. They’re canted at an angle; the cat is tilting his head and winking.
The Cat’s Eyes point to the right by nearly a fist-width toward Mu Scorpii, a much tighter pair (shown as a single dot on the map) known as the Little Cat’s Eyes. They’re oriented almost exactly the same way as Lambda and Upsilon. Are your eyes sharp enough to resolve the Mu pair without using binoculars? Not many people can!
Saturday, July 20
• Scorpius is sometimes called “the Orion of Summer” for its brightness, its blue-white giant stars, and its prominent red supergiant (Antares in the case of Scorpius, Betelgeuse for Orion). But Scorpius passes a lot lower across the south than Orion does, for those of us at mid-northern latitudes. That means it has only one really good evening month: July.
Catch Scorpius due south just after dark now, before it starts to tilt lower toward the southwest. It’s full of deep-sky objects to hunt with a sky atlas and binoculars or a telescope, before the waning gibbous Moon rises later tonight to light the sky.
• Once the Moon does rise in the east-southeast, contemplate the moment 50 years ago today when a man took the first step onto another world. The sunset terminator tonight is approaching Tranquillity Base, and everything there must be casting long shadows.
Want to become a better astronomer? Learn your way around the constellations. They’re the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential guide to astronomy.
Once you get a telescope, to put it to good use you’ll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows stars to magnitude 7.6.
Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, are the even larger Interstellarum atlas (stars to magnitude 9.5) and Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.
You’ll also want a good deep-sky guidebook, such as Sue French’s Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, or the bigger Night Sky Observer’s Guide by Kepple and Sanner.
Can a computerized telescope replace charts? Not for beginners, I don’t think, and not on mounts and tripods that are less than top-quality mechanically (meaning heavy and expensive). And as Terence Dickinson and Alan Dyer say in their Backyard Astronomer’s Guide, “A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand.”
This Week’s Planet Roundup
Mercury, Venus, and Mars are out of sight in the glare of the Sun. Mercury will be back in view in the dawn come August, but Venus and Mars are basically gone until October.
Jupiter (magnitude –2.5, in southern Ophiuchus) is the white point glaring in the south during and after dusk. Orange Antares, fainter at magnitude +1.0, twinkles 7° or 8° to its lower right.
Jupiter and Antares form a wide, shallow, almost isosceles triangle with Delta Scorpii (Dschubba) to their right. Delta, a long-term eruptive variable of the Gamma Cassiopeiae type, has been not much fainter than Antares for most of the last 19 years — after it brightened by some 50%, without warning, in July 2000.
In a telescope Jupiter is still a good 44 arcseconds wide. See Bob King’s observing guide to Jupiter.
Saturn (magnitude +0.1, in Sagittarius) is just past its July 9th opposition. It’s the steady, pale yellowish “star” in the southeast after dark, about 30° east (left) of Jupiter. To Saturn’s lower right is the Sagittarius Teapot.
Saturn is highest for telescopic observing in the middle of the night — but still not very high for us northerners, because it’s far south this year: around declination –22°. Saturn’s rings are tilted a wide 23° to our line of sight, not quite as open as they’ve been for the last couple of years.
Uranus (magnitude 5.8, in Aries) is high in the east before the first beginnings of dawn.
Neptune (magnitude 7.8, in Aquarius) is high in the south by that time. Finder charts for Uranus and Neptune.
All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world’s mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America.
Eastern Daylight Time (EDT) is Universal Time (UT, UTC, GMT, or Z time) minus 4 hours.
Audio sky tour. Out under the evening sky with your earbuds in place, listen to Kelly Beatty’s monthly podcast tour of the heavens above. It’s free.
“This adventure is made possible by generations of searchers strictly adhering to a simple set of rules. Test ideas by experiments and observations. Build on those ideas that pass the test. Reject the ones that fail. Follow the evidence wherever it leads, and question everything. Accept these terms, and the cosmos is yours.”
— Neil deGrasse Tyson, 2014 | 0.847235 | 3.122329 |
In episodes 7 and 8 of "Cosmos: Possible Worlds," host Neil deGrasse Tyson explores themes of science as an instrument of hope and tenacity, and as a means by which the human race can realize its true potential.
Episode 7, titled "Search for Intelligent Life," focuses specifically on first contact and the search for intelligent life in the vastness of the cosmos. Are humans ready to make first contact with other intelligent beings? Is our technology even sophisticated enough to detect communication signals from another world?
Seeking an answer, Tyson introduces us to China's Five-hundred-meter Aperture Spherical Telescope, or FAST, as it's more commonly known. FAST is the largest radio telescope on Earth and can detect radio waves across the universe.
Tyson points out that we've only had the technology to detect radio signals for a little over a century, making FAST a truly monumental achievement. FAST has already detected a number of pulsars — or compact stellar corpses — and will continue to search for gravitational waves and signs of extraterrestrial intelligence, among other data it collects.
However, there's an intricate global communications network hidden here on Earth that we've only just become aware of. Tyson turns our attention to a "hidden matrix … the creation of an enduring collaboration among fungi, plants, bacteria and animals." He's referring to the mycelium, a complex network of threadlike filaments that forms the functional structure of a fungus and extends to other species, such as trees. These hauntingly beautiful hyphae, or the branching filaments that make up the mycelium, illustrated in the show by special effects to interweave in the soil beneath our feet, reveal the forests' complex and interlinked nature.
"Who are we to search for alien intelligence when we can't even recognize or respect the consciousness all around us, or even beneath our feet," Tyson says, strolling through the forest on top of the soil that's protecting the mycelium beneath his feet. Still, conversations with different worlds, Tyson says, will be done in the language of science.
"The symbolic language of the scientist, mathematician and engineer avoid those things that are lost in translation from one culture to another," Tyson says, explaining that this type of language is more precise and less open to misinterpretation. If we find extraterrestrial intelligent life, will we be communicating with them in a language that resembles a computer programming language, built on the binary code?
"First contact" with intelligent life (on Earth)
Humans have actually already made "first contact" with other intelligent life that communicates through equations and a symbolic language, Tyson points out: bees. Insects in general have played an instrumental role in the development of the natural world, mostly by spreading pollen. Each grain of pollen has been"sculpted differently by evolution — each a novel strategy for survival, sharpened by vast expanses of time, " Tyson says.
Insects are as much a part of the Earth's history as the earth itself; The "great Ordovician biodiversity event," when our world began to change as plants and insects left the sea and began to make the land their home, occurred approximately 480 million years ago (or Dec. 20 on Tyson's "cosmic calendar," where the Big Bang marks New Year's Day). The world Tyson describes is an alien one; giant mushrooms tower over trees that only grew a few feet tall, and insects ruled the skies, undisturbed by other winged creatures.
It was Austrian ethologist Karl von Frisch who unlocked the secrets of bee behavior in the early 20th century. "For thousands of years, bees have been symbols of mindless industry … shackled to the dreary roles assigned to them by nature," says Tyson, but von Frisch found in his studies that bees lead much more complex lives. They communicate through mathematical equations expressed in their movements, appearing to the untrained eye to be little more than a waggle, but in reality can be an incredibly accurate set of coordinates to a food source meters away.
Tyson calls this a "first contact story" because bees and humans evolved on very different trajectories, and yet both species risked everything and chose the unknown; it's as if there were an unwritten code common to bees and human beings driving those ambitions.
This echoes the work of legendary scientist Charles Darwin, who realized if all life is related, certain philosophical implications had to follow. Darwin realized we are "surrounded by other ways of being alive and conscious," Tyson says, and that science had the potential to expand our capacity for empathy and compassion.
"The Sacrifice of Cassini"
Building on those themes of compassion and ambition, episode 8, "The Sacrifice of Cassini," chronicles tales of sacrifice and reveals the little-seen sentimentality and emotion that often accompany our greatest scientific endeavors. The episode honors the efforts and sacrifices of scientists Giovanni Cassini, Galileo Galilei, Christiaan Huygens, and Alexander Shargei, among others.
The episode opens with Tyson's recap of the Cassini-Huygens mission, a joint effort between NASA and the European Space Agency that launched Oct. 15, 1997. The spacecraft would embark on an epic voyage that would last more than two decades and culminate in a final, fatal mission of self-destruction by flying itself into Saturn's atmosphere in 2017.
Spacecraft sent to the outermost regions of our solar system, like Cassini, have brought back valuable data. Researchers are especially interested in any information about the mysterious ringed planets, which puzzled early planetary scientists like Galileo. These ring systems have been notoriously difficult to detect; Galileo's early research on Saturn had him believe the planet had two symmetrical moons, which we now know to be Saturn's rings. What would Galileo say if he could see Saturn as we see it now through the eyes of powerful scientific instruments?
NASA's Voyager 2 spacecraft and Cassini also sent back valuable data about the atmospheres and other physical properties of our cosmic neighbors, like the elusive Uranus. Without Voyager 2, we wouldn't know about the planet's long summers and winters, or that while Uranus doesn't generate any internal heat and the outer edges of its atmosphere is hotter than 500 degrees Fahrenheit (260 degrees Celsius), Uranus also has the coldest clouds in the solar system, nearly 400 degrees Fahrenheit (240 degrees Celsius) below zero.
Interestingly, as Tyson reviews Giovanni Cassini's early life in what is now Italy, he notes that the Italian scientist began his career as an astrologer; a pseudoscientist. Louis XIV of France, the "Sun King," who would be the first monarch to recognize the power of science and the opportunities it afforded national security, would play a pivotal role in Cassini's career development. It was Louis XIV, who established the Paris Observatory — a scientific powerhouse — and who gave Cassini the tools he needed to pursue his research.
Cassini's observations of Saturn and its moons would have an enduring effect on the scientific world among his other accomplishments, like having discovered Jupiter's Great Red Spot (independently from Robert Hooke) and having calculated the length of a day on Mars; he was only off by 3 minutes.
Cassini's work on Saturn also greatly furthered human beings' knowledge on the planet at the time; he was the first to know Saturn's rings were composed of natural satellites orbiting the planet, and that there were gaps between them. Decades later, a bus-size 12,000-lb. (5,400 kilograms) spacecraft, sent on a years-long voyage to that same celestial body, would be named in his memory.
The scientists who worked closely with the Cassini-Huygens spacecraft, some of them since the very beginning, undoubtedly became emotional as it completed its final mission, as did spectators around the world who witnessed its final moments.
The probe's travails, however, cannot compare to the pain and tragedy of scientist and visionary Oleksandr Shargei, a forgotten pioneer of spaceflight. Shargei was orphaned at a young age and, while studying engineering at a university in Saint Petersburg, Russia, was drafted to the army to serve the Russian Empire in World War I. After the Russian Revolution, when the Bolsheviks overthrew the government, he changed his name to Yuri Kondratyuk out of fear for his life.
In 1926, Kondratyuk self-published a manuscript on rocket motion and space colonization, which would end up capturing the attention of an engineer working on the Apollo program, John Houbolt, decades later. Houbolt's updating of Kondratyuk's theories convinced NASA to select the lunar orbit rendezvous flight plan for Apollo, and to win the Space Race.
Seeing footage from Apollo 11 in the episode elicits a sentimental feeling as it dawns on us that we're witnessing Kondratyuk's dreams become reality, and that his dreams are still coming true to this day; even the Cassini mission used gravity assist maneuvers, also conceived by Kondratyuk, to explore the Saturn system.
The final scene of the episode is of Kondratyuk's childhood home — a place where he endured much tragedy in his early years, and sought refuge in physics books. It was also here that Apollo 11 astronaut Neil Armstrong made a pilgrimage after his historic flight to the moon, to honor the man who made that voyage possible.
"There are all kinds of stories in the struggle to understand the cosmos," Tyson reflects. "Sometimes your dreams die with you, but sometimes the scientists of another age pick them up and take them to the moon, and far beyond."
"Cosmos" airs on the National Geographic channel on Mondays at 8 p.m. ET/9 p.m. CT and will be reprised on the Fox television network this summer.
- 'Cosmos: Possible Worlds' episode 5 explores the 'cosmic connectome'
- 'I want the solar system to become our backyard,' Neil deGrasse Tyson says
- Carl Sagan: Cosmos, Pale Blue Dot & famous quotes
All About Space magazine takes you on an awe-inspiring journey through our solar system and beyond, from the amazing technology and spacecraft that enables humanity to venture into orbit, to the complexities of space science.View Deal | 0.887528 | 3.019646 |
Astronomers have captured new, detailed maps of three nearby interstellar gas clouds containing regions of ongoing high-mass star formation. The results of this survey, called the Star Formation Project, will help improve our understanding of the star formation process.
We know that stars such as the Sun are born from interstellar gas clouds. These interstellar gas clouds are difficult to observe in visible light, but emit strong radio wavelength, which can be observed by the Nobeyama 45-m Radio Telescope in Japan. A research team led by Fumitaka Nakamura, an Associate Professor at the National Astronomical Observatory of Japan (NAOJ), used the telescope to create detailed radio maps of interstellar gas clouds, the birthplaces of stars. The team including members from NAOJ, the University of Tokyo, Tokyo Gakugei University, Ibaraki University, Otsuma Women's University, Niigata University, Nagoya City University, and other universities, will use the observational data to investigate the star formation process.
The team targeted three interstellar clouds: the Orion A, Aquila Rift, and M17 regions. For the Orion A region, the group collaborated with the CARMA interferometer in the United States, combining their data to create the most detailed map ever of the region. The resultant map has a spatial resolution of about 3200 astronomical units. This means that the map can reveal details as small as 60 times the size of the Solar System.
Even the world's most powerful radio telescope, the Atacama Large Millimeter/submillimeter Array (ALMA), could not obtain a similar large-scale map of Orion A because of ALMA's limited field-of-view and observation time constraints. But ALMA can investigate more distant interstellar clouds. Therefore, this large-scale, most-detailed radio map of the Orion A gas cloud obtained by the Star Formation Project is complementary with other observational research. | 0.873868 | 3.746716 |
vendredi 11 août 2017
CERN - European Organization for Nuclear Research logo.
11 Aug 2017
Image above: Like hunters following the tracks of their prey, physicists compare real collision data with simulations of what they expect to see if a new particle is produced and decays in their detectors. (Supersymmetry simulation image: the CMS collaboration).
With the LHC now back smashing protons together at an energy of 13 TeV, what exotic beasts do physicists hope to find in this unfamiliar corner of the natural world?
Among the top priorities for the LHC experiments this year is the hunt for new particles suspected to lurk at the high-energy frontier: exotic beasts that do not fit within the Standard Model of particle physics and could lift the lid on an even deeper theory of nature’s basic workings.
Following the discovery of the Higgs boson five years ago, which was the final missing piece of the Standard Model of particle physics, physicists have good reason to expect that new particle species lie over the horizon. Among them is the mystery of what makes up dark matter, why the Standard Model particles of matter weigh what they do and come in three families of two, and, indeed, why the Higgs boson isn’t vastly heavier than it is – that is, why it isn't so heavy that it could have ended the evolution of the universe an instant after the Big Bang.
Casting the net wide
These outlandish prey are just a few of the known unknowns for physicists. To ensure that no corner of the new-physics landscape is left unturned, the LHC experiments also employ a model-independent approach to search for general features such as pairs of high-energy quarks and leptons or for unexplained sources of missing energy.
Image above: New particles predicted by specific models of physics beyond the Standard Model (Image: Daniel Dominguez, with permission from Hitoshi Murayama).
Their most elusive quarry might not light up their detectors at all, forcing the LHC exploration teams to adopt stealth approaches, such as making ultra-precise measurements of known Standard Model processes and seeing if they diverge from predictions. While physicists are hoping for a clear shot at any new particle species – a distinctive “bump” in the data that can only be explained by the presence of a new, heavy particle – they could be faced with a mere rustling in the undergrowth or other indirect signs that something is awry. This quest is not just the preserve of all of the LHC experiments, but also of numerous other experiments at CERN that are not linked to the LHC.
Either way, physicists exploring this uncharted territory of the high-energy frontier have to take extreme care not to get tricked by numerous Standard Model doppelgängers or be teased by inconclusive statistics. Even after an exotic new beast has been snared statistically and it seems that the LHC experiments have a discovery on their hands, so begins the task of identifying what the beast really is: a mere mutant or close relative of a species we already know? Or the first glimpse of a new subatomic kingdom?
Ranging from the bizarre to the mind-boggling, and in no particular order, below is a summary of some of the quantum creatures that are in the LHC experimentalists’ sights this year.
- Supersymmetric particles:
For more than 40 years, physicists have been beguiled by a hypothetical symmetry of space–time called supersymmetry (SUSY), which would imply that every particle in the Standard Model has a partner called a “sparticle”. Given that these have not yet been seen, they must be heavier than the standard version.
Considered by many to be mathematically beautiful, SUSY can settle some of the technical problems with the Standard Model and suggests ways in which the fundamental forces may be unified. The lightest SUSY particle is also a good candidate to explain what makes up dark matter.
SUSY could reveal itself in many ways in the LHC’s ATLAS and CMS experiments, for instance in events in which much of the energy is carried away by massive, weakly interacting sparticles. Like previous colliders, the LHC has so far found no evidence for supersymmetry, which rules out the existence of certain types of sparticles below a mass of 2 TeV.
- Higgs siblings:
The Standard Model demands just one type of Higgs boson, and so far it seems that the observed Higgs particle fits the requirements. However, many theories suggest that this standard Higgs is one of a wider family of Higgs particles with slightly different properties – SUSY predicts no less than five of them.
Since the Higgs boson, which gives the Standard Model particles their masses, is a fundamentally different “scalar” object compared to all other known particles, it could open the door to new physics domains.
Exotic cousins of the Higgs have different electrical charges and other properties, especially their mass, forcing them to decay differently to the standard Higgs in ways that should be relatively easy to spot.
- New vector bosons:
At the quantum level, nature’s fundamental forces are mediated by elementary particles called vector bosons: the neutral photon for electromagnetism, and the neutral Z or charged W bosons for the weak nuclear force responsible for radioactive decay. In principle, additional vector bosons – known as W’ and Z’ – could exist, too.
Finding such particles would constitute the discovery of a fifth force of nature, radically changing our view of the universe and extending the structure of the Standard Model.
Experimental signatures of new vector bosons, which presumably are heavier than the W and Z, otherwise they would have been spotted by now, range from direct production in ATLAS and CMS to more subtle signs of lepton flavour violation in LHCb.
- Extra dimensions:
The possible existence of additional dimensions of space beyond the three we know of was put forward in the late 1990s to nurse some of the Standard Model’s ills. In this picture, the entire universe could merely be a 3D “brane” floating through a higher-dimensional bulk, to which the Standard model particles are forever shackled while leaving the force of gravity to propagate freely in the bulk, or there could be additional microscopic dimensions at extremely small scales.
If true, it would allow physicists to study gravitons and other gravitational phenomena in the lab, as it would shift the scale of quantum gravity by many orders of magnitude, right down to the TeV scale where the LHC operates.
The presence of extra dimensions could produce a clear missing-energy signal in the ATLAS and CMS detectors and lead to “resonances”, like notes on a guitar string, that correspond to invisible relatives of the hypothetical carrier of gravity: the graviton.
- Quantum black holes:
If extra dimensions exist, implying gravity is stronger than we thought, it is possible for very light black-holes to exist – mathematically resembling a conventional astrophysical black hole but trillions and trillions of times lighter. Such a state is predicted to evaporate more or less as soon as it formed and therefore poses no danger. After all, if such creatures are created at high energies, then they are also created all the time in collisions between cosmic rays and the upper atmosphere without doing any apparent harm.
The discovery of a miniature black hole would revolutionise physics and accelerate efforts to create a quantum theory of gravity that unites quantum mechanics with Einstein’s general theory of relativity.
Miniature black holes would decay or “evaporate” instantly into other particles, revealing themselves as events containing multiple particles.
- Dark matter:
The Standard Model, while passing every test on Earth, can only account for 5% of the matter observed in the universe as a whole. It is presumed that the dark matter known to exist from astronomical observations is made of some kind of particle, perhaps a supersymmetric particle, but precisely which type is a still a mystery.
In addition to explaining a large fraction of the universe, the ability to study dark matter in the laboratory would open a rich and fascinating new line of experimental study.
Dark matter interacts very weakly, if at all, via the standard forces, and would leave a characteristic missing-energy signature in the ATLAS and CMS detectors.
The Standard Model contains two basic types of matter: quarks, which make up protons and neutrons; and leptons, such as electrons and neutrinos. Leptoquarks are hypothetical particles that are a bit of both, allowing quarks and leptons to transform into one another.
Leptoquarks appear in certain extensions of the Standard Model, in particular in attempts to unify the strong, weak and electromagnetic interactions.
Since they are expected to decay into a lepton and a quark, searches at the LHC look for characteristic bumps in the mass distributions of decay products.
- Quark substructure:
All the experimental evidence so far indicates that the six types of quarks we know of are indivisible, but history has shown us to be wrong on this front with other particles, not least the atom. Exploring matter at smaller scales, it is natural to ask: are quarks really the smallest entities, or do they possess components inside them?
If found, quark substructure would prove that there is a whole new layer of the subatomic world that we do not yet know about. The existence of “preons” has been postulated to give an explanation at a more fundamental level to the table of elementary particles and forces, with the aim of replicating the successful ordering of the periodic table.
The experimental signature of the compositeness of quarks can be the detection of the decay of a quark in an excited state into ordinary quarks and gluons, which will in turn produce two streams of highly-energetic collimated particles called jets.
- Heavy sterile neutrinos:
The Standard Model involves three types of light neutrinos – electron, muon and tau neutrinos – but several puzzles, such as the very small mass of regular neutrinos, suggest that there might be additional, sterile neutrinos, much heavier than the regular ones.
If found, a heavy sterile neutrino can help solve the problem of matter-antimatter asymmetry in the universe. It could also be a candidate for dark matter, in addition to accounting for the small masses of the regular, non-sterile neutrinos, which cannot be otherwise explained in the framework of the Standard Model.
The mass of sterile neutrinos is theoretically unknown, but their presence could be revealed when they “oscillate” into regular, flavoured neutrinos.
- Long-lived particles:
New particles produced in a particle collision are generally assumed to decay immediately, almost precisely at their points of origin, or to escape undetected. However, many models of new physics include heavy particles with lifetimes large enough to allow them to travel distances ranging from a few micrometres to a few hundred thousand kilometres before decaying into ordinary matter.
Heavy, long-lived particles can help explaining many of the unsolved questions of the Standard Model, such as the small mass of the Higgs boson, dark matter, and perhaps the imbalance of matter and antimatter in the universe.
Long-lived particles could appear like a stream of ordinary matter spontaneously appearing out of nowhere (“displaced vertices”). Other ways to search for them include looking for a large “dE/dx”, long time of flight or tracks disappearing in the detector.
CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.
The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.
Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.
LHC experiments: http://home.cern/about/experiments
Large Hadron Collider (LHC): http://home.cern/topics/large-hadron-collider
Standard Model: http://home.cern/about/physics/standard-model
Higgs boson: http://home.cern/topics/higgs-boson
For more information about European Organization for Nuclear Research (CERN), Visit: http://home.cern/
Images (mentioned), Text, Credits: CERN/Matthew Chalmers, Stefania Pandolfi.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 13:54
SpaceX - CRS-12 Dragon Mission patch.
August 11, 2017
Meteorologists with the U.S. Air Force 45th Space Wing are predicting a 70 percent chance of favorable weather for liftoff of the SpaceX Falcon 9 rocket carrying a Dragon spacecraft. Launch of the company’s twelfth commercial resupply mission to the International Space Station is scheduled for Monday, Aug. 14 at 12:31 p.m. EDT from Launch Pad 39A at NASA’s Kennedy Space Center in Florida.
Image above: On June 3, 2017, a SpaceX Falcon 9 rocket lifted off from Launch Complex 39A on the company’s 11th commercial resupply services mission to the International Space Station. Photo credits: NASA/Tony Gray.
Rain and thunderstorms are expected today and through the weekend, especially in the afternoon – a familiar summer weather pattern for Florida’s Space Coast. Heading into Monday, cumulus clouds and flight through precipitation are forecasters’ primary launch weather concerns, but the early afternoon launch time is helpful.7
NASA Television: https://www.nasa.gov/multimedia/nasatv/index.html
Cargo Resupply (CRS): https://blogs.nasa.gov/spacex/category/cargo-resupply-crs/
Image (mentioned), Text, Credits: NASA/Anna Heiney.
Publié par Orbiter.ch à 12:42
NASA - Hubble Space Telescope patch.
Aug. 11, 2017
The subject of this NASA/ESA Hubble Space Telescope image is a dwarf galaxy named NGC 5949. Thanks to its proximity to Earth — it sits at a distance of around 44 million light-years from us, placing it within the Milky Way’s cosmic neighborhood — NGC 5949 is a perfect target for astronomers to study dwarf galaxies.
With a mass of about a hundredth that of the Milky Way, NGC 5949 is a relatively bulky example of a dwarf galaxy. Its classification as a dwarf is due to its relatively small number of constituent stars, but the galaxy’s loosely-bound spiral arms also place it in the category of barred spirals. This structure is just visible in this image, which shows the galaxy as a bright yet ill-defined pinwheel. Despite its small proportions, NGC 5949’s proximity has meant that its light can be picked up by fairly small telescopes, something that facilitated its discovery by the astronomer William Herschel in 1801.
Astronomers have run into several cosmological quandaries when it comes to dwarf galaxies like NGC 5949. For example, the distribution of dark matter within dwarfs is quite puzzling (the “cuspy halo” problem), and our simulations of the Universe predict that there should be many more dwarf galaxies than we see around us (the “missing satellites” problem).
Hubble Space Telescope
Image, Animation, Credits: ESA/Hubble & NASA/Text Credits: European Space Agency/NASA/Karl Hille.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 12:32
Jet Propulsion Laboratory (JPL) logo.
August 11, 2017
Image above: This illustration shows what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Image Credits: NASA/JPL-Caltech.
If we want to know more about whether life could survive on a planet outside our solar system, it's important to know the age of its star. Young stars have frequent releases of high-energy radiation called flares that can zap their planets' surfaces. If the planets are newly formed, their orbits may also be unstable. On the other hand, planets orbiting older stars have survived the spate of youthful flares, but have also been exposed to the ravages of stellar radiation for a longer period of time.
Scientists now have a good estimate for the age of one of the most intriguing planetary systems discovered to date -- TRAPPIST-1, a system of seven Earth-size worlds orbiting an ultra-cool dwarf star about 40 light-years away. Researchers say in a new study that the TRAPPIST-1 star is quite old: between 5.4 and 9.8 billion years. This is up to twice as old as our own solar system, which formed some 4.5 billion years ago.
The seven wonders of TRAPPIST-1 were revealed earlier this year in a NASA news conference, using a combination of results from the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, NASA's Spitzer Space Telescope, and other ground-based telescopes. Three of the TRAPPIST-1 planets reside in the star's "habitable zone," the orbital distance where a rocky planet with an atmosphere could have liquid water on its surface. All seven planets are likely tidally locked to their star, each with a perpetual dayside and nightside.
At the time of its discovery, scientists believed the TRAPPIST-1 system had to be at least 500 million years old, since it takes stars of TRAPPIST-1's low mass (roughly 8 percent that of the Sun) roughly that long to contract to its minimum size, just a bit larger than the planet Jupiter. However, even this lower age limit was uncertain; in theory, the star could be almost as old as the universe itself. Are the orbits of this compact system of planets stable? Might life have enough time to evolve on any of these worlds?
"Our results really help constrain the evolution of the TRAPPIST-1 system, because the system has to have persisted for billions of years. This means the planets had to evolve together, otherwise the system would have fallen apart long ago," said Adam Burgasser, an astronomer at the University of California, San Diego, and the paper's first author. Burgasser teamed up with Eric Mamajek, deputy program scientist for NASA's Exoplanet Exploration Program based at NASA's Jet Propulsion Laboratory, Pasadena, California, to calculate TRAPPIST-1's age. Their results will be published in The Astrophysical Journal.
It is unclear what this older age means for the planets' habitability. On the one hand, older stars flare less than younger stars, and Burgasser and Mamajek confirmed that TRAPPIST-1 is relatively quiet compared to other ultra-cool dwarf stars. On the other hand, since the planets are so close to the star, they have soaked up billions of years of high-energy radiation, which could have boiled off atmospheres and large amounts of water. In fact, the equivalent of an Earth ocean may have evaporated from each TRAPPIST-1 planet except for the two most distant from the host star: planets g and h. In our own solar system, Mars is an example of a planet that likely had liquid water on its surface in the past, but lost most of its water and atmosphere to the Sun's high-energy radiation over billions of years.
Image above: TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius, and its seven planets orbit very close to it. Image Credits: NASA/JPL-Caltech.
However, old age does not necessarily mean that a planet's atmosphere has been eroded. Given that the TRAPPIST-1 planets have lower densities than Earth, it is possible that large reservoirs of volatile molecules such as water could produce thick atmospheres that would shield the planetary surfaces from harmful radiation. A thick atmosphere could also help redistribute heat to the dark sides of these tidally locked planets, increasing habitable real estate. But this could also backfire in a "runaway greenhouse" process, in which the atmosphere becomes so thick the planet surface overheats - as on Venus.
"If there is life on these planets, I would speculate that it has to be hardy life, because it has to be able to survive some potentially dire scenarios for billions of years," Burgasser said.
Fortunately, low-mass stars like TRAPPIST-1 have temperatures and brightnesses that remain relatively constant over trillions of years, punctuated by occasional magnetic flaring events. The lifetimes of tiny stars like TRAPPIST-1 are predicted to be much, much longer than the 13.7 billion-year age of the universe (the Sun, by comparison, has an expected lifetime of about 10 billion years).
"Stars much more massive than the Sun consume their fuel quickly, brightening over millions of years and exploding as supernovae," Mamajek said. "But TRAPPIST-1 is like a slow-burning candle that will shine for about 900 times longer than the current age of the universe."
Some of the clues Burgasser and Mamajek used to measure the age of TRAPPIST-1 included how fast the star is moving in its orbit around the Milky Way (speedier stars tend to be older), its atmosphere's chemical composition, and how many flares TRAPPIST-1 had during observational periods. These variables all pointed to a star that is substantially older than our Sun.
Future observations with NASA's Hubble Space Telescope and upcoming James Webb Space Telescope may reveal whether these planets have atmospheres, and whether such atmospheres are like Earth's.
"These new results provide useful context for future observations of the TRAPPIST-1 planets, which could give us great insight into how planetary atmospheres form and evolve, and persist or not," said Tiffany Kataria, exoplanet scientist at JPL, who was not involved in the study.
Future observations with Spitzer could help scientists sharpen their estimates of the TRAPPIST-1 planets' densities, which would inform their understanding of their compositions.
For more information about TRAPPIST-1, visit: https://exoplanets.nasa.gov/trappist1
Images (mentioned), Text, Credits: NASA/JPL/Elizabeth Landau.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 10:46
Jet Propulsion Laboratory (JPL) logo.
August 11, 2017
Animation above: Changes in sea level height from 1993 to 2017 compared with a long-term mean of the data. Blue and purple are lower than the mean; red, yellow and white are higher. Animation Credits: NASA/JPL-Caltech.
Today marks the 25th anniversary of the launch of a revolutionary ocean research vessel -- a space "ship." As the NASA/CNES Topex-Poseidon satellite ascended into orbit, it ushered in a new era of oceanography with the first highly accurate, global measurements of sea levels. That mission and its three successors, all named Jason, have continuously mapped global ocean currents and tides; opened our eyes to the global reach of El Niño and other climate events; created a quarter-century-long, extraordinarily precise record of global and regional sea level rise; and enabled improved forecasts of extreme weather events such as hurricanes, floods and droughts.
A new slideshow celebrates this important data set -- a fundamental measurement for the study of the oceans and climate -- and the longstanding U.S.-French collaboration that brought it about.
Image above: Topex-Poseidon illustration. Image Credits: NASA/JPL-Caltech.
In 1992, when Topex-Poseidon launched, no one foresaw that its record of precision ocean height measurements would continue through three decades and four spacecraft. In fact, many oceanographers at the time weren't convinced that Topex-Poseidon's sensors would be accurate enough to reveal the signal of sea level rise out of the noise of waves, tides and other changes. But the radar altimeter and radiometer measurement system outperformed expectations from the start. In 25 years of continuous operation, Topex-Poseidon and its successors have recorded 2.8 inches (7 centimeters) of global average sea level rise.
Our planet's oceans are too vast and complex to be fully measured by any single satellite, or even by any single nation. Topex-Poseidon and its successor Jason satellite missions are shining examples of the power of a sustained, long-term international partnership, led by the U.S. and French space agencies, NASA and CNES. For nearly three decades, NASA and CNES scientists and engineers have pooled their expertise, talents and insights to design and construct an integrated spaceborne measurement system far more powerful than the sum of its parts. NASA and CNES have worked together, applying advanced technology to collect measurements of remarkable precision and accuracy, and then making those measurements freely and openly available. With this effort, they have provided humanity with unprecedented views of the global oceans, how they change on time scales of days to decades, and how the oceans influence -- and respond to -- weather and climate.
"For more than a generation, NASA and CNES scientists and engineers have collaborated to make exquisitely accurate measurements of the ocean surface from space, providing insights into the workings and interactions of our planet's two great fluid systems, the oceans and the atmosphere," said Michael Freilich, director of NASA's Earth Science Division in Washington.
Video above: This is an animation of ocean surface currents from June 2005 to December 2007 from NASA satellites. Video Credits: NASA/GSFC/SVS.
The Topex-Poseidon mission was the first to monitor the changing patterns of major ocean surface currents in a comprehensive way. Ocean current locations are revealed by large-scale hills and valleys on the ocean surface, which can vary by more than 6 feet (2 meters) in height. The peaks and dips defining the ocean's topography are caused by variations in water temperature and pressure. Large-scale currents like the Gulf Stream tend to flow along contours of constant ocean height, following the sides of the hills and valleys. The steepness of a slope indicates the speed of the current. Unlike terrain on land, however, the liquid "landscape" shifts with changes in winds, temperature and other factors, causing shifts in the locations and speeds of the currents. The only way to monitor these changes over the entire surface of Earth's ocean is to make precise measurements of the height of the ocean surface from orbiting satellites.
Measuring the ocean shape over nearly the entire globe every 10 days, Topex-Poseidon gave the first quantitative view of how ocean currents change with the seasons. Topex/Poseidon and the Jason-1, Jason-2 and Jason-3 missions have provided unique insights into how ocean circulation affects climate by moving heat from place to place on our planet.
Heat Storage in the Ocean
Image above: NOAA's annual assessment of the heat in the upper ocean (2015 shown), a measure of global warming, draws on Topex series data. Image Credit: NOAA.
More than 90 percent of the heat from global warming is stored in the ocean, which means oceans are key players in global climate. Heat causes ocean water to expand, adding to sea level rise. Measuring both long-term sea level trends and the shape of the ocean surface related to currents, Topex-Poseidon and the Jason series provide two basic ingredients for understanding the ocean's role in global climate variations.
"As human-caused global warming drives sea levels higher and higher, we are literally contributing to the reshaping of the surface of our planet," said Josh Willis, NASA project scientist for Jason-3 at NASA's Jet Propulsion Laboratory in Pasadena, California. "The precision altimetric satellite missions tell us how much and how fast."
El Niño, La Niña, and More
Image above: Among Topex-Poseidon's early achievements was recording the full extent of a record El Niño in 1997 and the succeeding La Niña in 1999. Darker colors are sea levels lower than normal, lighter and white colors are higher than normal. Image Credits: NASA/JPL-Caltech.
For decades, scientists could not predict how El Niño and other year-to-year ocean variations changed regional weather. That was partly because, using only ships and buoys, they couldn't observe the genesis and growth of these changes far out in the equatorial Pacific. Topex-Poseidon and the Jason satellites have given the first frequent, global views of the full extent and life cycles of El Niño and La Niña events. Lee-Lueng Fu of JPL -- project scientist for the first two ocean altimetry missions -- pointed out, "Topex-Poseidon allowed us to follow their evolution and showed that these events weren't limited to just the tropics. It also gave us evidence of even longer-lasting ocean variations." One of these is the Pacific Decadal Oscillation, similar to El Niño and La Niña in character but with phases lasting up to several decades.
In the last 25 years, with the help of altimetry data, scientists have pinpointed many global connections between these multi-year ocean variations and weather consequences such as drought and flooding throughout the globe. While these events have by no means yielded all their secrets, they are better understood and better forecast than before global spaceborne observations began.
Tides on the Open Ocean
Image above: A numerical model of daily global tides using sea level data from Topex-Poseidon. Image Credit: ESR.
Before satellite measurements, deep-ocean tide measurements were difficult to make, expensive and sparse. Topex-Poseidon made the first global maps of tides, which changed scientists' understanding of how tides dissipate. The data show that a third of tidal energy dissipates in the open ocean, playing important and previously unknown roles in mixing water within the ocean.
Topex-Poseidon had a three-year prime mission, but long before that time was up, oceanographers and other Earth scientists recognized the value of continuing its measurements as long as possible. Fu explained, "Sea surface height is a fundamental measure of the Earth system, so it was a no-brainer that scientists would want to have this kind of information indefinitely." With strong community support, Jason-1 was constructed by NASA and CNES and launched in December 2001. For three years, Topex-Poseidon and Jason-1 flew in coordinated orbits that allowed scientists to cross-calibrate their measurements and then combine the data sets to observe the global oceans more frequently. Each succeeding mission has also overlapped its predecessor, ensuring a consistent data record.
So far, each of the ocean altimetry missions has proven to be long-lived. Topex-Poseidon was eventually decommissioned in 2005 after 13 years in orbit. Jason-1 survived almost 12 years, until July 2013. Nine-year-old Jason-2 and Jason-3 (launched in January 2016) are still in operation.
Image above: Lee Fu (left) was the project scientists for Topex Poseidon and Jason-1 and -2. Josh Willis is the current project scientist for Jason-2 and -3. Image Credits: NASA/JPL-Caltech.
With the launch of Jason-2 in June 2008, the focus of spaceborne ocean altimetry transitioned from research objectives to data applications providing tangible benefits to society. Mission operations moved from the research agencies NASA and CNES to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT); indeed, satellite altimeter measurements are used routinely in NOAA's El Niño forecasts. NASA and CNES continue to provide science teams, instrument design, and science-focused, specialized data management.
Image above: Jason-1 data contributed to this forecast of Hurricane Rita's track across the Gulf of Mexico in 2005. The storm track appears as a black line. Jason-1 observed a tongue of very warm water (red) in the gulf, 13-23 inches ( 35-60 centimeters) higher than surrounding water. Ocean heat can strengthen hurricane intensity. Image Credits: NASA/JPL-Caltech/University of Colorado.
On smaller space and time scales, satellite altimetry measurements provide information directly useful for marine storm prediction. Hurricanes are fueled by heat stored in the ocean below, and since the upper ocean expands and contracts as it heats and cools, sea level height is a marker for water temperature and heat content. So it is hardly surprising that ocean altimetry data are routinely used in forecasting hurricane strength.
In 2014, an unexpected forecasting use for altimetry data became operational. Bangladesh, whose 46-year history has encompassed death-dealing river floods, uses Jason-2 measurements of river levels in its flood forecasting and warning system. Within the first year using these data, Bangladesh's system enabled the most accurate, long-lead flood warnings ever given for that nation.
Image above: The U.S. Navy uses the ocean altimetry satellites' data to aid surface and underwater navigation. Image Credit: U.S. Navy.
Civilian sailors and the U.S. Navy use the series' near-real-time data on currents, eddies, winds and waves to aid surface and underwater navigation. Information on eddy currents in the Gulf of Mexico has been used by marine operators to schedule offshore drilling operations, with significant cost savings.
Video above: Artist's rendering of Jason-3. Video Credits: NASA/JPL-Caltech.
When Jason-3 launched in 2016, NASA project scientist Willis commented, "This mission has big shoes to fill. Its predecessors have built one of the clearest records we have of our changing climate." Jason-3 has performed flawlessly in continuing the global record of precise sea-surface topography measurements and is now halfway through its prime mission.
A New Role for Jason-2
Image above: Jason-2's new, lower orbit will allow scientists -- such as Walter H. Smith (NOAA) and David Sandwell (Scripps Institution of Oceanography), who produced this map -- to improve their understanding of features on the global seafloor. Image Credit: NOAA.
This year, Jason-2's onboard systems began to show signs of space radiation damage. The mission management decided to lower the satellite out of its shared orbit with Jason-3. At the urging of the science community, the satellite was lowered by 17 miles (27 kilometers), where it will collect data along a series of ground tracks only 5 miles (8 kilometers) apart, with a one-year repeat cycle.
Besides protecting Jason-3, the new orbit will allow Jason-2 to produce an improved, high-resolution estimate of Earth's average sea surface height. Because ocean topography is partly determined by the contours on the ocean bottom, the estimate is expected to enable scientists to improve maps of the seafloor, resolving currently unknown details of underwater features such as seamounts. These maps will permit advances in ocean modeling, tsunami wave forecasting and naval operations support.
Into the Future
Image above: Illustration of the upcoming Sentinel-6 mission. Image Credit: ESA.
The next ocean altimetry mission, expected to launch in 2020, is called Jason Continuity of Service (Jason-CS) on the Sentinel-6 mission. As the long name implies, it will carry on the proud Jason legacy, but with a new partner: the European Space Agency. EUMETSAT will lead the mission, and NASA's role will remain similar to its role in Jason-3. CNES will assess and evaluate the performance of the mission and provide precise orbit determination.
Satellites have already revolutionized oceanography, and soon they will do the same for hydrology -- the study of water on land. The French/U.S. Surface Water and Ocean Topography (SWOT) mission will be at the forefront, carrying an innovative interferometer dubbed KaRin that marks a break with today's technologies.
Fu notes that these changes show the value the world scientific community places on the ocean altimetry program. "The measurement is so important, and the technology is fully demonstrated," he said. "In the long haul, ocean altimetry is an international commitment."
Jet Propulsion Laboratory (JPL): https://www.jpl.nasa.gov/
Animation (mentioned), Images (mentioned), Videos (mentioned), Text, Credits: NASA, written by Carol Rasmussen/JPL/Alan Buis.
Publié par Orbiter.ch à 10:27
jeudi 10 août 2017
ISS - Expedition 52 Mission patch.
August 10, 2017
International Space Station (ISS). Animation Credit: NASA
The Expedition 52 crew members pulled out their medical hardware today for a variety of eye checks and other biomedical research. The station residents are also making space and packing up gear for next week’s cargo delivery aboard the SpaceX Dragon.
The crew each participated in a series of eye exams throughout Thursday working with optical coherence tomography (OCT) gear. OCT is a medical imaging technique that captures imagery of the retina using light waves. A pair of cosmonauts then peered into a fundoscope for a more detailed look at the eye’s interior. The regularly scheduled eye checks were conducted with real-time input from doctors on the ground.
SpaceX completed a static fire test of its Falcon 9 rocket today at NASA’s Kennedy Space Center. The Dragon cargo craft will be perched atop the Falcon 9 for a targeted launch Monday at 12:31 p.m. EDT.
Image above: The full moon is pictured from the International Space Station. Image Credit: NASA.
Once in space, Dragon will conduct a series of orbital maneuvers navigating its way to the station Wednesday morning. Finally, Dragon will reach its capture point ten meters away from the complex. From there, astronauts Jack Fischer and Paolo Nespoli will command the Canadarm2 to reach out and grapple Dragon. Next, ground controllers remotely guide Dragon still attached to the Canadarm2 and install it to the Harmony module.
The crew is clearing space on the International Space Station today and packing gear to stow on Dragon after it arrives next week. NASA TV begins its pre-launch coverage Sunday covering Dragon’s science payloads. Monday’s launch coverage begins at noon. NASA TV will also broadcast Dragon’s arrival Wednesday beginning at 5:30 a.m.
Expedition 52: https://www.nasa.gov/mission_pages/station/expeditions/expedition52/index.html
Kennedy Space Center: https://www.nasa.gov/kennedy
Launch coverage: https://www.nasa.gov/press-release/nasa-television-to-air-launch-of-next-space-station-resupply-mission
Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html
International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html
Animation (mentioned), Image (mentioned), Text, Credits: NASA/Mark Garcia.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 15:31
NASA - Solar Dynamics Observatory (SDO) patch.
Aug. 10, 2017
On Aug. 21, 2017, the Moon will slide in front of the Sun and for a brief moment, day will melt into a dusky night. Moving across the country, the Moon’s shadow will block the Sun’s light, and weather permitting, those within the path of totality will be treated to a view of the Sun’s outer atmosphere, called the corona.
But the total solar eclipse will also have imperceptible effects, such as the sudden loss of extreme ultraviolet radiation from the Sun, which generates the ionized layer of Earth’s atmosphere, called the ionosphere. This ever-changing region grows and shrinks based on solar conditions, and is the focus of several NASA-funded science teams that will use the eclipse as a ready-made experiment, courtesy of nature.
NASA is taking advantage of the Aug. 21 eclipse by funding 11 ground-based science investigations across the United States. Three of these will look to the ionosphere in order to improve our understanding of the Sun’s relationship to this region, where satellites orbit and radio signals are reflected back toward the Earth.
“The eclipse turns off the ionosphere’s source of high-energy radiation,” said Bob Marshall, a space scientist at University of Colorado Boulder and principal investigator for one of the studies. “Without ionizing radiation, the ionosphere will relax, going from daytime conditions to nighttime conditions and then back again after the eclipse.”
Animation above: During the total solar eclipse, the Moon will turn off the ionosphere’s source of extreme ultraviolet radiation: The ionosphere will go from daytime conditions to nighttime conditions. Animation Credits: NASA’s Goddard Space Flight Center/Katy Mersmann.
Stretching from roughly 50 to 400 miles above Earth’s surface, the tenuous ionosphere is an electrified layer of the atmosphere that reacts to changes from both Earth below and space above. Such changes in the lower atmosphere or space weather can manifest as disruptions in the ionosphere that can interfere with communication and navigation signals.
“In our lifetime, this is the best eclipse to see,” said Greg Earle, an electrical and computer engineer at Virginia Tech in Blacksburg, Virginia, who is leading another of the studies. “But we’ve also got a denser network of satellites, GPS and radio traffic than ever before. It’s the first time we’ll have such a wealth of information to study the effects of this eclipse; we’ll be drowning in data.”
Pinning down ionospheric dynamics can be tricky. “Compared to visible light, the Sun’s extreme ultraviolet output is highly variable,” said Phil Erickson, a principal investigator of a third study and space scientist at Massachusetts Institute of Technology’s Haystack Observatory in Westford, Massachusetts. “That creates variability in ionospheric weather. Because our planet has a strong magnetic field, charged particles are also affected along magnetic field lines all over the planet — all of this means the ionosphere is complicated.”
But when totality hits on Aug. 21, scientists will know exactly how much solar radiation is blocked, the area of land it’s blocked over and for how long. Combined with measurements of the ionosphere during the eclipse, they’ll have information on both the solar input and corresponding ionosphere response, enabling them to study the mechanisms underlying ionospheric changes better than ever before.
Animation above: The Moon’s shadow will dramatically affect insolation — the amount of sunlight reaching the ground — during the total solar eclipse. Animation Credits: NASA's Scientific Visualization Studio.
Tying the three studies together is the use of automated communication or navigation signals to probe the ionosphere’s behavior during the eclipse. During typical day-night cycles, the concentration of charged atmospheric particles, or plasma, waxes and wanes with the Sun.
“In the daytime, ionospheric plasma is dense,” Earle said. “When the Sun sets, production goes away, charged particles recombine gradually through the night and density drops. During the eclipse, we’re expecting that process in a much shorter interval.”
Image above: During typical day-night cycles, the ionosphere — shown in purple and not-to-scale in this image — waxes and wanes with the Sun. The total solar eclipse will cut off this region’s source of ionizing radiation. Image Credits: NASA's Goddard Space Flight Center/Duberstein.
The denser the plasma, the more likely these signals are to bump into charged particles along their way from the signal transmitter to receiver. These interactions refract, or bend, the path taken by the signals. In the eclipse-induced artificial night the scientists expect stronger signals, since the atmosphere and ionosphere will absorb less of the transmitted energy.
“If we set up a receiver somewhere, measurements at that location provide information on the part of the ionosphere between the transmitter and receiver,” Marshall said. “We use the receivers to monitor the phase and amplitude of the signal. When the signal wiggles up and down, that’s entirely produced by changes in the ionosphere.”
Using a range of different electromagnetic signals, each of the teams will send signals back and forth across the path of totality. By monitoring how their signals propagate from transmitter to receiver, they can map out changes in ionospheric density. The teams will also use these techniques to collect data before and after the eclipse, so they can compare the well-defined eclipse response to the region’s baseline behavior, allowing them to discern the eclipse-related effects.
Probing the Ionosphere
Image above: A layer of charged particles, called the ionosphere, surrounds Earth, extending from about 50 to 400 miles above the surface of the planet. Image Credits: NASA's Goddard Space Flight Center/Duberstein.
The ionosphere is roughly divided into three regions in altitude based on what wavelength of solar radiation is absorbed: the D, E and F, with D being the lowermost region and F, the uppermost. In combination, the three experiment teams will study the entirety of the ionosphere.
Marshall and his team, from the University of Colorado Boulder, will probe the D-region’s response to the eclipse with very low frequency, or VLF, radio signals. This is the lowest and least dense part of the ionosphere — and because of that, the least understood.
“Just because the density is low, doesn’t mean it’s unimportant,” Marshall said. “The D-region has implications for communications systems actively used by many military, naval and engineering operations.”
Marshall’s team will take advantage of the U.S. Navy’s existing network of powerful VLF transmitters to examine the D-region’s response to changes in solar output. Radio wave transmissions sent from Lamoure, North Dakota, will be monitored at receiving stations across the eclipse path in Boulder, Colorado, and Bear Lake, Utah. They plan to combine their data with observations from several space-based missions, including NOAA’s Geostationary Operational Environmental Satellite, NASA’s Solar Dynamics Observatory and NASA’s Ramaty High Energy Solar Spectroscopic Imager, to characterize the effect of the Sun’s radiation on this particular region of the ionosphere.
Erickson and team will look further up, to the E- and F-regions of the ionosphere. Using over 6,000 ground-based GPS sensors alongside powerful radar systems at MIT’s Haystack Observatory and Arecibo Observatory in Puerto Rico, along with data from several NASA space-based missions, the MIT-based team will also work with citizen radio scientists who will send radio signals back and forth over long distances across the path.
MIT’s science team will use their data to track travelling ionospheric disturbances — which are sometimes responsible for space weather patterns in the upper atmosphere — and their large-scale effects. These disturbances in the ionosphere are often linked to a phenomenon known as atmospheric gravity waves, which can also be triggered by eclipses.
“We may even see global-scale effects,” Erickson said. “Earth’s magnetic field is like a wire that connects two different hemispheres together. Whenever electrical variations happen in one hemisphere, they show up in the other.”
Image above: Earth's limb at night, seen from the International Space Station, with air glow visual composited into the image. Image Credit: NASA.
Earle and his Virginia Tech-based team will station themselves across the country in Bend, Oregon; Holton, Kansas; and Shaw Air Force Base in Sumter, South Carolina. Using state-of-the-art transceiver instruments called ionosondes, they will measure the ionosphere’s height and density, and combine their measurements with data from a nation-wide GPS network and signals from the ham radio Reverse Beacon Network. The team will also utilize data from SuperDARN high frequency radars, two of which lie along the eclipse path in Christmas Valley, Oregon, and Hays, Kansas.
“We’re looking at the bottom side of the F-region, and how it changes during the eclipse,” Earle said. “This is the part of the ionosphere where changes in signal propagation are strong.” Their work could one day help mitigate disturbances to radio signal propagation, which can affect AM broadcasts, ham radio and GPS signals.
Ultimately, the scientists plan to use their data to improve models of ionospheric dynamics. With these unprecedented data sets, they hope to better our understanding of this perplexing region.
“Others have studied eclipses throughout the years, but with more instrumentation, we keep getting better at our ability to measure the ionosphere,” Erickson said. “It usually uncovers questions we never thought to ask.”
For more information on the upcoming total solar eclipse: https://eclipse2017.nasa.gov
NASA Looks to Solar Eclipse to Help Understand Earth’s Energy System: https://www.nasa.gov/feature/goddard/2017/nasa-looks-to-the-solar-eclipse-to-help-understand-the-earth-s-energy-system
Chasing the Total Solar Eclipse from NASA’s WB-57F Jets: https://www.nasa.gov/feature/goddard/2017/chasing-the-total-solar-eclipse-from-nasa-s-wb-57f-jets
Solar Dynamics Observatory (SDO): http://www.nasa.gov/mission_pages/sdo/main/index.html
GOES (Geostationary Environmental Operational Satellites): http://www.nasa.gov/goes/
RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager): http://www.nasa.gov/mission_pages/sunearth/index.html
Images (mentioned), Animations (mentioned), Text, Credits: NASA/Rob Garner/Goddard Space Flight Center, by Lina Tran.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 15:21
NASA - Mars Science Laboratory (MSL) patch.
Aug. 10, 2017
Animation above: Wispy clouds float across the Martian sky in this accelerated sequence of enhanced images taken on July 17, 2017, by the Navcam on NASA's Curiosity Mars rover. Animation Credits: NASA/JPL-Caltech/York University.
Wispy, early-season clouds resembling Earth's ice-crystal cirrus clouds move across the Martian sky in some new image sequences from NASA's Curiosity Mars rover.
These clouds are the most clearly visible so far from Curiosity, which landed five years ago this month about five degrees south of Mars' equator. Clouds moving in the Martian sky have been observed previously by Curiosity and other missions on the surface of Mars, including NASA's Phoenix Mars Lander in the Martian arctic nine years ago.
Researchers used Curiosity's Navigation Camera (Navcam) to take two sets of eight images of the sky on an early Martian morning last month. For one set, the camera pointed nearly straight up. For the other, it pointed just above the southern horizon. Cloud movement was recorded in both and was made easier to see by image enhancement. A midday look at the sky with the same camera the same day showed no clouds.
Animation above: Clouds drift across the sky above a Martian horizon in this accelerated sequence of enhanced images taken on July 17, 2017, by the Navcam on NASA's Curiosity Mars rover. Animation Credits: NASA/JPL-Caltech/York University.
Mars' elliptical orbit makes that planet's distance from the Sun vary more than Earth's does. In previous Martian years, a belt of clouds has appeared near the equator around the time Mars was at its farthest from the Sun. The new images of clouds were taken about two months before that farthest point in the orbit, relatively early in the season for the appearance of this cloud belt.
"It is likely that the clouds are composed of crystals of water ice that condense out onto dust grains where it is cold in the atmosphere," said Curiosity science-team member John Moores of York University, Toronto, Canada. "The wisps are created as those crystals fall and evaporate in patterns known as 'fall streaks' or 'mare's tails.' While the rover does not have a way to ascertain the altitude of these clouds, on Earth such clouds form at high altitude."
Animation above: Wispy clouds float across the Martian sky in this accelerated sequence of early-morning images taken on July 17, 2017, by the Navcam on NASA's Curiosity Mars rover. Animation Credits: NASA/JPL-Caltech/York University.
York's Charissa Campbell produced the enhanced-image sequences by generating an "average" of all the frames in each sequence, then subtracting that average from each frame, emphasizing any frame-to-frame changes. The moving clouds are also visible, though fainter, in a sequence of raw images.
The Curiosity mission has been investigating the environmental conditions of ancient and modern Mars since the rover landed on Aug. 5, 2012, PDT (Aug. 6, EDT and Universal Time). For more about Curiosity, visit: https://mars.jpl.nasa.gov/msl
Animations (mentioned), Text, Credits: NASA/Laurie Cantillo/Dwayne Brown/Tony Greicius/JPL/Guy Webster.
Publié par Orbiter.ch à 14:11
NASA - Chandra X-ray Observatory patch.
Aug. 10, 2017
In 1887, American astronomer Lewis Swift discovered a glowing cloud, or nebula, that turned out to be a small galaxy about 2.2 billion light years from Earth. Today, it is known as the “starburst” galaxy IC 10, referring to the intense star formation activity occurring there.
More than a hundred years after Swift’s discovery, astronomers are studying IC 10 with the most powerful telescopes of the 21st century. New observations with NASA’s Chandra X-ray Observatory reveal many pairs of stars that may one day become sources of perhaps the most exciting cosmic phenomenon observed in recent years: gravitational waves.
By analyzing Chandra observations of IC 10 spanning a decade, astronomers found over a dozen black holes and neutron stars feeding off gas from young, massive stellar companions. Such double star systems are known as “X-ray binaries” because they emit large amounts of X-ray light. As a massive star orbits around its compact companion, either a black hole or neutron star, material can be pulled away from the giant star to form a disk of material around the compact object. Frictional forces heat the infalling material to millions of degrees, producing a bright X-ray source.
When the massive companion star runs out fuel, it will undergo a catastrophic collapse that will produce a supernova explosion, and leave behind a black hole or neutron star. The end result is two compact objects: either a pair of black holes, a pair of neutron stars, or a black hole and neutron star. If the separation between the compact objects becomes small enough as time passes, they will produce gravitational waves. Over time, the size of their orbit will shrink until they merge. LIGO has found three examples of black hole pairs merging in this way in the past two years.
Starburst galaxies like IC 10 are excellent places to search for X-ray binaries because they are churning out stars rapidly. Many of these newly born stars will be pairs of young and massive stars. The most massive of the pair will evolve more quickly and leave behind a black hole or a neutron star partnered with the remaining massive star. If the separation of the stars is small enough, an X-ray binary system will be produced.
This new composite image of IC 10 combines X-ray data from Chandra (blue) with an optical image (red, green, blue) taken by amateur astronomer Bill Snyder from the Heavens Mirror Observatory in Sierra Nevada, California. The X-ray sources detected by Chandra appear as a darker blue than the stars detected in optical light.
The young stars in IC 10 appear to be just the right age to give a maximum amount of interaction between the massive stars and their compact companions, producing the most X-ray sources. If the systems were younger, then the massive stars would not have had time to go supernova and produce a neutron star or black hole, or the orbit of the massive star and the compact object would not have had time to shrink enough for mass transfer to begin. If the star system were much older, then both compact objects would probably have already formed. In this case transfer of matter between the compact objects is unlikely, preventing the formation of an X-ray emitting disk.
Chandra X-ray Observatory
Chandra detected 110 X-ray sources in IC 10. Of these, over forty are also seen in optical light and 16 of these contain “blue supergiants”, which are the type of young, massive, hot stars described earlier. Most of the other sources are X-ray binaries containing less massive stars. Several of the objects show strong variability in their X-ray output, indicative of violent interactions between the compact stars and their companions.
A pair of papers describing these results were published in the February 10th, 2017 issue of The Astrophysical Journal and is available online here and here. The authors of the study are Silas Laycock from the UMass Lowell’s Center for Space Science and Technology (UML); Rigel Capallo, a graduate student at UML; Dimitris Christodoulou from UML; Benjamin Williams from the University of Washington in Seattle; Breanna Binder from the California State Polytechnic University in Pomona; and, Andrea Prestwich from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.
Read More from NASA's Chandra X-ray Observatory: http://chandra.harvard.edu/photo/2017/ic10/
For more Chandra images, multimedia and related materials, visit: http://www.nasa.gov/chandra
Image, Animation, Text, Credits: X-ray: NASA/Lee Mohon/CXC/UMass Lowell/S. Laycock et al.; Optical: Bill Snyder Astrophotography.
Publié par Orbiter.ch à 13:51
ESA - Mars Express Mission patch.
10 August 2017
An ancient mountain range on Mars preserves a complex volcanic and tectonic past imprinted with signs of water and ice interactions.
The images, taken on 9 April by the high-resolution stereo camera on ESA’s Mars Express, show the Thaumasia mountains and Coracis Fossae, which fringe the huge Solis Planum volcanic plateau from the south.
Thaumasia mountain range in context
The region lies to the south of the vast Valles Marineris canyon system and towering Tharsis volcanoes, and is strongly linked to the tectonic stresses that played out during their formation over 3.5 billion years ago.
As the Tharsis bulge swelled with magma during the planet’s first billion years, the surrounding crust was stretched, ripping apart and eventually collapsing into troughs. While Valles Marineris is one of the most extreme results, the effects are still seen even thousands of kilometres away, such as in the Coracis Fossae region observed in this image where near-parallel north–south faults are visible primarily to the left.
Thaumasia mountain topography
Tectonic structures like these can control the movement of magma, heat and water in the subsurface, leading to hydrothermal activity and the production of minerals.
Light-toned deposits, which might be clay minerals formed in the presence of water, stand out in the right part of the colour image and at the rim of the large crater. Similar deposits were identified in the nearby Lampland crater.
Perspective view of crater in Thaumasia mountain range
There is also evidence for valley formation by groundwater erosion and surface runoff occurring at the same time as when the active tectonics shaped the landscape. The water-based erosion means the troughs have been partially buried and heavily modified.
The region was later modified by glacial processes, seen in the flow-like lineated patterns in the flat floors of the large craters.
Thaumasia mountains in 3D
As a representative of the ancient highlands of Mars, this region holds a wealth of information about the Red Planet’s geological history.
Mars Express: http://www.esa.int/Our_Activities/Space_Science/Mars_Express
Mars Webcam: http://blogs.esa.int/vmc
Robotic exploration of Mars: http://exploration.esa.int/science-e/www/area/index.cfm?fareaid=118
Mars Express overview: http://www.esa.int/Our_Activities/Space_Science/Mars_Express_overview
Mars Express in-depth: http://sci.esa.int/marsexpress
ESA Planetary Science archive (PSA): http://www.rssd.esa.int/PSA
High Resolution Stereo Camera: http://berlinadmin.dlr.de/Missions/express/indexeng.shtml
HRSC data viewer: http://hrscview.fu-berlin.de/
Behind the lens... http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Behind_the_lens
Frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Frequently_asked_questions
Images, Text, Credits: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO/NASA MGS MOLA Science Team.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 08:03
mercredi 9 août 2017
ISS - Expedition 52 Mission patch.
August 9, 2017
Moon Rise From the Space Station
Image above: From his vantage point aboard the International Space Station, NASA astronaut Randy Bresnik pointed his camera toward the rising Moon and captured this beautiful image on August 3, 2017. Bresnik wrote, "Gorgeous moon rise! Such great detail when seen from space. Next full moon marks #Eclipse2017. We’ll be watching from @Space_Station." Image Credit: NASA.
A docked Russian cargo craft fired its engines today slightly raising the orbit of the International Space Station. The orbital boost sets up next month’s crew swap. The SpaceX Dragon cargo craft also received a new target launch date while the crew gets ready for a spacewalk next week.
NASA astronauts Peggy Whitson and Jack Fischer will return to Earth on Sept. 2 with cosmonaut Fyodor Yurchikhin wrapping up their Expedition 52 mission. Fischer and Yurchikhin will each have lived 135 consecutive days in space while Whitson will have 289 days. The next crew, with cosmonaut Alexander Misurkin and astronauts Mark Vande Hei and Joe Acaba, launches Sept. 13 to begin a 167-day mission in space.
Image above: Astronaut Peggy Whitson works on the Combustion Integrated Rack in the U.S. Destiny laboratory module. Image Credit: NASA.
SpaceX announced a one-day launch slip of its Dragon cargo craft atop a Falcon 9 rocket. Dragon is now targeted to launch Monday at 12:31 p.m. EDT from Kennedy Space Center. Fischer and astronaut Paolo Nespoli of the European Space Agency are training for Dragon’s arrival and capture planned for Wednesday at 7 a.m.
Two cosmonauts are also gearing up for a spacewalk amidst the cargo mission and crew swap preparations. The experienced Russian spacewalkers, Yurchikhin with eight career spacewalks and Sergey Ryazanskiy with three, performed leak checks, installed batteries and sized up their Orlan spacesuits and ahead of their Aug. 17 spacewalk.
Combustion Integrated Rack: https://www.nasa.gov/mission_pages/station/research/facilities/index.html
SpaceX Dragon: https://www.nasa.gov/spacex
Commercial Resupply: http://www.nasa.gov/mission_pages/station/structure/launch/index.html
Expedition 52: https://www.nasa.gov/mission_pages/station/expeditions/expedition52/index.html
Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html
International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html
Images (mentioned), Text, Credits: NASA/Mark Garcia/Sarah Loff.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 16:32
NASA - Cassini Mission to Saturn patch.
Aug. 9, 2017
Image above: This artist's rendering shows Cassini as the spacecraft makes one of its final five dives through Saturn's upper atmosphere in August and September 2017. Image Credits: NASA/JPL-Caltech.
Cassini spacecraft will enter new territory in its final mission phase, the Grand Finale, as it prepares to embark on a set of ultra-close passes through Saturn’s upper atmosphere with its final five orbits around the planet.
Cassini will make the first of these five passes over Saturn at 12:22 a.m. EDT Monday, Aug. 14. The spacecraft's point of closest approach to Saturn during these passes will be between about 1,010 and 1,060 miles (1,630 and 1,710 kilometers) above Saturn's cloud tops.
The spacecraft is expected to encounter atmosphere dense enough to require the use of its small rocket thrusters to maintain stability – conditions similar to those encountered during many of Cassini's close flybys of Saturn's moon Titan, which has its own dense atmosphere.
"Cassini's Titan flybys prepared us for these rapid passes through Saturn's upper atmosphere," said Earl Maize, Cassini project manager at NASA's Jet Propulsion Laboratory (JPL) in California. "Thanks to our past experience, the team is confident that we understand how the spacecraft will behave at the atmospheric densities our models predict."
Maize said the team will consider the Aug. 14 pass nominal if the thrusters operate between 10 and 60 percent of their capability. If the thrusters are forced to work harder – meaning the atmosphere is denser than models predict – engineers will increase the altitude of subsequent orbits. Referred to as a "pop-up maneuver,” thrusters will be used to raise the altitude of closest approach on the next passes, likely by about 120 miles (200 kilometers).
If the pop-up maneuver is not needed, and the atmosphere is less dense than expected during the first three passes, engineers may alternately use the "pop-down" option to lower the closest approach altitude of the last two orbits, also likely by about 120 miles (200 kilometers). Doing so would enable Cassini's science instruments, especially the ion and neutral mass spectrometer (INMS), to obtain data on the atmosphere even closer to the planet's cloud tops.
Cassini Grand Finale. Animation Credits: NASA/JPL-Caltech
"As it makes these five dips into Saturn, followed by its final plunge, Cassini will become the first Saturn atmospheric probe," said Linda Spilker, Cassini project scientist at JPL. "It's long been a goal in planetary exploration to send a dedicated probe into the atmosphere of Saturn, and we're laying the groundwork for future exploration with this first foray."
Other Cassini instruments will make detailed, high-resolution observations of Saturn's auroras, temperature, and the vortexes at the planet's poles. Its radar will peer deep into the atmosphere to reveal small-scale features as fine as 16 miles (25 kilometers) wide – nearly 100 times smaller than the spacecraft could observe prior to the Grand Finale.
On Sept. 11, a distant encounter with Titan will serve as a gravitational version of a large pop-down maneuver, slowing Cassini’s orbit around Saturn and bending its path slightly to send the spacecraft toward its Sept. 15 plunge into the planet.
During the half-orbit plunge, the plan is to have seven Cassini science instruments, including INMS, turned on and reporting measurements in near real time. The spacecraft is expected to reach an altitude where atmospheric density is about twice what it encountered during its final five passes. Once Cassini reaches that point, its thrusters will no longer be able to work against the push of Saturn’s atmosphere to keep the spacecraft's antenna pointed toward Earth, and contact will permanently be lost. The spacecraft will break up like a meteor moments later, ending its long and rewarding journey.
The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate in Washington. JPL designed, developed and assembled the Cassini spacecraft.
For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org and ESA's website: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens
Animation (mentioned), Image (mentioned), Text, Credits: NASA/Felicia Chou/Katherine Brown/JPL/Preston Dyches.
Best regards, Orbiter.ch
Publié par Orbiter.ch à 12:39 | 0.930484 | 3.688537 |
Jupiter’s moon Io is the most volcanically-active body in our solar system, and a recent observational campaign offers a little more insight into the a terrifying hellscape that awaits any unfortunate space probes we send there.
A team of astronomers at UC Berkeley has just completed a two and a half year survey of Jupiter’s eruptive satellite Io, using the near infrared optical capabilities of the Keck II and Gemini North telescopes at Mauna Kea, Hawaii. The result is the first high-resolution time series of volcanic hot spots on Io, a world about the size of our moon that features hundreds of active volcanoes and a few mind-bogglingly vast lava lakes.
Hot spots observed in the new study, with size corresponding logarithmically to intensity (a spot twice as large is ten times brighter). More opaque regions represent where hot spots were detected multiple times, while the colour and symbol indicate the type of eruption. Image: de Kleer et al. 2016
said in a statement.
The new analysis, which has been accepted for publication in Icarus, revealed a few surprises, including a clustering of extremely bright volcanoes in the south, an apparent progression of volcanic activity across the surface, and strange stirrings inside Loki Patera, an 203km-wide lava lake that’s been observed to brighten up every few years.
Mostly, the work serves as a reminder that we still understand very little about Io’s flagrant outbursts, which are thought to be powered by tidal heating from Jupiter’s gravitational pull. “We want to understand tidal heating as a process better,” de Kleer said, noting that the same process promotes warm liquid water oceans beneath the icy surface of Jupiter’s moon Europa, and Saturn’s Enceladus. “Places that are considered the most potentially habitable all have tidal heating.”
Not all places with tidal heating are potentially habitable, however. Io, which looks like a fossilized jaw-breaker doused in acid and whose atmosphere collapses pretty regularly, certainly isn’t the first moon I’d buy cosmic real estate on. Still, it’s proven an astounding place to study from afar. | 0.852911 | 3.783812 |
Using cameras aboard an orbiting NASA satellite, Princeton astronomer Alicia Soderberg has captured a never-before-seen cosmic phenomenon - a burst of X rays marking the start of a supernova.
These exploding stars can light up surrounding space with the power of a billion suns. But no one had ever seen the initial flash of a supernova, thought to last a few minutes before a more steady glow takes over.
An astronomer could train a camera on a given galaxy for a century or more and get nothing.
With a stroke of serendipity, however, Soderberg had the right cameras pointed to the right place at the right time.
Supernovae are more than just cosmic firecrackers. They and other dying stars spew out heavy elements that infused the planets of our solar system and made life possible.
The calcium in our bones, the iron in our blood, and the carbon that pervades all life were formed during the death throes of faraway stars. And the explosions spread these elements through the universe like so much cosmic compost.
Catching this event was improbable.
"This was the earliest we've ever seen a supernova," said Roger Chevalier, an astronomer at the University of Virginia.
The closest they had come before was a dying star called 1987A, which was caught hours after exploding.
Soderberg said this new finding could help astronomers better understand what kinds of stars explode, the physics of the explosions, and how they influence the evolution of the universe.
Previously known supernovae were seen only later, usually as an afterglow of radioactive gases that persist for a few months.
Scientists working out the physics of these explosions had long predicted an initial burst of X rays called breakout light. But with supernovae occurring only once a century or so in a given galaxy, there was no way to know where to look.
Adding to the challenge was the fact that Earth's atmosphere deflects X rays, so this blast could only be detected using one of two satellites.
"After my colloquium, I rushed and looked at the data," she said, "and obviously there was something really bright in the image that wasn't there two days before."
The X rays had overwhelmed the detector, she said. "It's as if you took a digital camera and pointed it at the sun and took a picture."
Against all odds, she realized that another supernova was exploding in this same distant galaxy that had produced one just a month before.
Later, the Hubble Space Telescope would be aimed at the supernova, whose brightness in other wavelengths started to increase over the next few days.
Before stars explode, they start to collapse, said astronomer Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics. When a star runs out of fuel, it loses the gas pressure that had pushed outwards to balance the inward force of gravity.
If it's large enough, the star's core collapses so hard as to crush its very atoms, creating a superdense "neutron star" in about a second.
During a star's death throes, Kirshner said, nuclear reactions glue together small elements to make carbon, oxygen, and other elements up to iron on the periodic table. Heavier elements such as gold and uranium start to form in the heat of the blast.
So all the carbon, oxygen, and heavier elements on Earth were made in other stars that exploded long before the sun was born, Kirshner said.
Our sun will die, too, but without so much fanfare. "There's no explosion for us," Kirshner said. Instead, in about five billion years, the sun will swell to become a red-giant, which will kill all life, he said, after heating the seas, "and boiling all the lobsters."
To explode like a supernova, a star has to be 10 or 20 times the mass of our sun, Kirshner said.
This latest supernova can't be seen by the naked eye because it's so far away. There's the potential for a good show in our own galaxy, but we haven't had one for a long time.
Because there's so much dust in our galaxy, we can't see all the supernovae that have exploded in recent centuries, said Kirshner, though Renaissance astronomers Tycho Brahe and Johannes Kepler reported seeing them.
Chinese astronomers described some very bright ones, and observers in various places reported something in 1006 that outshone the full moon. In 1987, a supernova in a neighboring galaxy was visible from the Southern Hemisphere.
"If it hadn't happened in that hour, she would have missed it," he said.
On the other hand, he said, Soderberg was quick to recognize what she had found and act on it. "Sometimes if you're really energetic, you manufacture your own luck." | 0.892336 | 4.064532 |
BLASTS of radio waves from space may deliver a much bigger wallop than expected. For the first time, we have seen one of these enigmatic fast radio bursts occurring together with a spurt of gamma rays, meaning their joint source may be a billion times more energetic than we thought.
FRBs have proved baffling since their discovery in 2007. Each torrent of radio waves lasts no more than a few milliseconds and we have only spotted 17 of them so far.
Finding accompanying signals at other wavelengths may be the key to decoding their source. But to observe such a paired event, we would have to be watching the same area of the sky with a radio telescope and a telescope operating at different wavelengths when an FRB occurs there.
“We’ve been really unlucky so far: we’re almost always looking in the wrong places to be helpful,” says Emily Petroff at the Netherlands Institute for Radio Astronomy.
“This points to their source being a more catastrophic event such as a supernova or neutron star merger“
But now we have a match. Derek Fox at Pennsylvania State University and his colleagues studied old data from the Burst Alert Telescope on NASA’s Swift spacecraft to see if any gamma-ray bursts coincided with FRBs. They found one example from 2013 (arxiv.org/abs/1611.03139).
That challenges lower-energy explanations for FRBs and points to their source being a more catastrophic event such as a supernova or neutron star merger. But it also increases the mystery in some ways, Fox says. “The whole suite of properties that we observed doesn’t really line up exactly with any of the predictions.”
Finding more bursts will help. “I’ve got my party hat ready,” says Petroff. “I think we’ll have the answer in the near future.”
This article appeared in print under the headline “Mystery radio bursts spew gamma rays too”
More on these topics: | 0.870418 | 3.756847 |
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