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Evidence for Thousands of Black Holes Buzzing Around the Center of the Milky Way
Since the 1970s, astronomers have understood that a Supermassive Black Hole (SMBH) resides at the center of the Milky Way Galaxy. Located about 26,000 light-years from Earth between the Sagittarius and Scorpius constellations, this black hole has come to be known as Sagittarius A* (Sgr A*). Measuring 44 million km across, this object is roughly 4 million times as massive as our Sun and exerts a tremendous gravitational pull.
Since that time, astronomers have discovered that most massive galaxies have SMBHs at their core, which is what separates those that have an Active Galactic Nuclei (AGN) from those that don’t. But thanks to a recent survey conducted using NASA’s Chandra X-ray Observatory, astronomers have discovered evidence for hundreds or even thousands of black holes located near the center of the Milky Way Galaxy.
The study which described their findings was recently published in the journal Nature under the title “A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy“. The study was led by Chuck Hailey, the Pupin Professor of Physics and the Co-Director of the Columbia Astrophysics Laboratory (CAL) at Columbia University, and including members from the Instituto de Astrofísica at the Pontificia Universidad Católica de Chile and the Harvard-Smithsonian Center for Astrophysics.
The center of the Milky Way Galaxy, with X-ray binaries circled in red, other X-ray sources circled in yellow, and Sagittarius A* circled in blue at the center. Credit: NASA/CXC/Columbia University/C. Hailey et al.
Using Chandra data, the team searched for X-ray binaries containing black holes that were in the vicinity of Sgr A*. To recap, black holes are not detectable in visible light. However, black holes (or neutron stars) that are locked in close orbits with a star will pull material from their companions, which will then be accreted onto the black holes’ disks and heated up to millions of degrees.
This will result in the release of X-rays which can then be detected, hence why these systems are called “X-ray binaries”. Using Chandra data, the team sought out X-ray of sources that were located within roughly 12 light years of Sgr A*. They then selected sources with X-ray spectra similar to those of known X-ray binaries, which emit relatively large amounts of low-energy X-rays.
Using this method, they detected fourteen X-ray binaries within about three light years of Sgr A*, all of which contained stellar-mass black holes (between 5 and 30 times the mass of our Sun). Two of these sources had been identified by previous studies and were eliminated from the analysis, while the remaining twelve (circled in red in the image above) were newly-discovered.
Other sources which relatively large amounts of high energy X-rays (labeled in yellow) were believed to be binaries containing white dwarfs. Hailey and his colleagues concluded that the majority of the dozen X-ray binaries were likely to contain black holes, based on their variability and the fact that their X-ray emissions over the course of several years was different from what is expected from binaries containing neutron stars.
Artist”s impression of a black hole binary, consisting of a black hole siphoning material from its companion. Credit: ESO/L. Calçada
Given that only the brightest X-ray binaries containing black holes are likely to be detectable around Sgr A* (given its distance from Earth), Hailey and his colleagues concluded that this detection implies the existence of a much larger population. By their estimates, there could be at least 300 and as many as one thousand stellar-mass black holes present around Sgr A*.
These findings confirmed what theoretical studies on the dynamics of stars in galaxies have indicated in the past. According to these studies, a large population of stellar mass black holes (as many as 20,000) could drift inward over the course of millions of years and collect around an SMBH. However, the recent analysis conducted by Hailey and his colleagues was the first observational evidence of black holes congregating near Sgr A*.
Naturally, the authors acknowledge that there are other explanations for the X-ray emissions they detected. This includes the possibility that half of the dozen sources they observed are millisecond pulsars – very rapidly rotating neutron stars with strong magnetic fields. However, based on their observations, Hailey and his team strongly favor the black hole explanation.
In addition, a follow-up study conducted by Aleksey Generozov (et al.) of Columbia University – titled “An Overabundance of Black Hole X-Ray Binaries in the Galactic Center from Tidal Captures” – indicated that there could be as many as 10,000 to 40,000 black holes binaries at the center of our galaxy. According to this study, these binaries would be the result of companions being captured by black holes.
In addition to revealing much about the dynamics of stars in our galaxy, this study has implications for the emerging field of gravitational wave (GW) research. Essentially, by knowing how many black holes reside at the center of galaxies (which will periodically merge with one another), astronomers will be able to better predict how many gravitational wave events are associated with them.
From this, astronomers could create predictive models about when and how GW events are likely to happen, and well as discerning what role they may play in galactic evolution. And with next-generation instruments – like the James Webb Space Telescope (JWST) and the ESA’s Advanced Telescope for High Energy Astrophysics (ATHENA) – astronomers will be able to determine exactly how many black holes reside near the center of our galaxy.
Further Reading: NASA
The post Evidence for Thousands of Black Holes Buzzing Around the Center of the Milky Way appeared first on Universe Today.
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The First Billion Years — Bombardment:
Shaping Planetary Surfaces and Their Environments
The LPI’s First Billion Years initiative is designed to support an interdisciplinary study of planetary accretion, differentiation, bombardment, and habitability in a series of four topical conferences. The third installment in that series, Bombardment, investigated the range of collisional events that occurred after planetary accretion when an extended period of bombardment may have been punctuated by one or more bursts of activity. The largest impactors produced impact basins hundreds to thousands of kilometers in diameter, completely reshaping the surfaces of rocky and icy planets. These types of events were not unique to our solar system. Debris disks produced by similar processes have been observed around other stars after they emerged from their natal gas-rich nebulae and up to several hundred million years after they formed. Although the Moon was a central component of the conference due to its exquisitely preserved record, the discussion necessarily included observations elsewhere, such as on the Hadean Earth, Mars, the asteroid belt, outer solar system moons, and planetary systems elsewhere. Because the bombardment may have affected the origin and early evolution of life, discussion also drew on astrobiological findings.
Before those discussions kicked off, conference participants made a trip to Meteor Crater, Arizona. The group had an opportunity to see first hand how astronomical and geological forces can shape a planetary surface. The excursion provided ample opportunity to discuss the nature of impacting objects, crater excavation processes, the development of ejecta blankets, and some of the environmental effects of impact events, both large and small. Importantly, the group also had an opportunity to see the types of geologic samples available around an impact crater and discuss how we can use the characteristics of related lunar samples to better infer their provenance. The group made good use of the second edition of the LPI’s award-winning Guidebook to the Geology of Barringer Meteorite Crater, Arizona (a.k.a. Meteor Crater).
Back in Flagstaff, the meeting was launched by a fascinating presentation by Kate Su (University of Arizona), who spoke about astronomical observations of debris disks that provide insights to the types of bombardment that occur around young stars. That was the first of a series of oral sessions that explored the first billion years of a planetary system’s history. “Astronomical Observations” of collisions in exoplanetary systems provided a potential snapshot of the types of events that affected our own solar system. “Geochemical, Geological, and Petrological Observations” used analyses of the rock record to extract clues about the last phase of accretion and the latest portion of a subsequent period of bombardment. “Ages of Impacts Part I and Part II” presented geochronologic and geological data used to determine the absolute and relative timing of impacts during the (lunar) basin-forming epoch. Discussion was led by session chairs David Kring (LPI), Timmons Erickson (NASA Johnson Space Center), and Richard Walker (University of Maryland). To ensure important constraints were not overlooked, a broadly-themed “Solar System Bombardment” poster session examined bombardment processes across the solar system.
Those data-rich sessions were followed by “Developing Models Consistent with the Data,” which not only drew on existing data, but also provided hints of future work. That set the stage for the session “Future Tests,” which recognized that the new NASA Lunar Exploration Campaign will provide opportunities to test several of the hypotheses being discussed. That discussion was guided by chairs Heather Meyer (LPI) and Gregory Neumann (NASA Goddard Space Flight Center).
Those sessions revealed three fault lines in the community: (1) argon-argon lunar impact ages and their implications for early solar system bombardment are often misunderstood; (2) It is unclear if the size frequency distribution (SFD) of surface craters can be integrated with subsurface gravity signatures of additional craters to obtain a revised SFD of impactors; and (3) the geological and lithological products of impact-cratering processes on the Moon are apparently mysterious, not only in an exciting way ripe with discovery, but also in a disappointing way reflective of confusion. That latter point is a reminder that the planetary science field has drifted far from the talents of those involved in Apollo. If we are going to press forward with new lunar and planetary surface operations, training programs like those at Meteor Crater will be essential for safe and productive missions.
Conference attendees then turned their attention to related topics: “The Early Earth Record,” “The Last Billion Years,” and “Bombardment and Implications for Habitability,” guided by chairs Simone Marchi (Southwest Research Institute), David Minton (Purdue University), and Nicole Zellner (Albion College). A wonderfully engaging closing presentation was provided by Penelope Boston (Director, NASA Astrobiology Institute), who drew out the biological threads in the meeting and provided an inspired transition to the Habitability conference, which is the next (and final) installment in LPI’s First Billion Years initiative. For those interested in the conference finale, make plans for visiting Wyoming and Montana September 8–12, 2019. The meeting will begin with a one-day excursion to Yellowstone National Park to explore the biologic potential of hydrothermal systems in volcanic settings and to spark discussion of a similar potential in impact-generated hydrothermal systems that may have existed during the dawn of life nearly 4 billion years ago. The field trip will be followed by presentations and discussion of planetary habitability, the production of conditions conducive to life, the emergence of life on Earth, the potential for abiogenesis on other solar system bodies, and extensions to extrasolar systems.
For more information, including links to the program and abstracts, visit the meeting website at https://www.hou.usra.edu/meetings/bombardment2018/.
— David A. Kring, Convener, Lunar and Planetary Institute | 0.878029 | 3.922963 |
The Great Filter, in the context of the Fermi paradox, is whatever prevents “dead matter” from giving rise, in time, to “expanding lasting life”.The concept originates in Robin Hanson’s argument that the failure to find any extraterrestrial civilizations in the observable universe implies the possibility something is wrong with one or more of the arguments from various scientific disciplines that the appearance of advanced intelligent life is probable; this observation is conceptualized in terms of a “Great Filter” which acts to reduce the great number of sites where intelligent life might arise to the tiny number of intelligent species with advanced civilizations actually observed (currently just one: human). This probability threshold, which could lie behind us (in our past) or in front of us (in our future), might work as a barrier to the evolution of intelligent life, or as a high probability of self-destruction.The main counter-intuitive conclusion of this observation is that the easier it was for life to evolve to our stage, the bleaker our future chances probably are.
With no evidence of intelligent life other than ourselves, it appears that the process of starting with a star and ending with “advanced explosive lasting life” must be unlikely. This implies that at least one step in this process must be improbable. Hanson’s list, while incomplete, describes the following nine steps in an “evolutionary path” that results in the colonization of the observable universe:
- The right star system (including organics and potentially habitable planets)
- Reproductive molecules (e.g., RNA)
- Simple (prokaryotic) single-cell life
- Complex (archaeatic and eukaryotic) single-cell life
- Sexual reproduction
- Multi-cell life
- Tool-using animals with big brains
- Where we are now
- Colonization explosion.
According to the Great Filter hypothesis at least one of these steps – if the list were complete – must be improbable. If it’s not an early step (i.e., in our past), then the implication is that the improbable step lies in our future and our prospects of reaching step 9 (interstellar colonization) are still bleak. If the past steps are likely, then many civilizations would have developed to the current level of the human race. However, none appear to have made it to step 9, or the Milky Way would be full of colonies. So perhaps step 9 is the unlikely one, and the only thing that appears likely to keep us from step 9 is some sort of catastrophe or the resource exhaustion leading to impossibility to make the step due to consumption of the available resources (like for example highly constrained energy resources). So by this argument, finding multicellular life on Mars (provided it evolved independently) would be bad news, since it would imply steps 2–6 are easy, and hence only 1, 7, 8 or 9 (or some unknown step) could be the big problem.
Although steps 1–7 have occurred on Earth, any one of these may be unlikely. If the first seven steps are necessary preconditions to calculating the likelihood (using the local environment) then an anthropically biased observer can infer nothing about the general probabilities from its (pre-determined) surroundings.
A variant of the self-replicating starship is the Berserker. Unlike the benign probe concept, Berserkers are programmed to seek out and exterminate lifeforms and life-bearing exoplanets whenever they are encountered.
The name is derived from the Berserker series of novels by Fred Saberhagen which describe a war between humanity and such machines. Saberhagen points out (through one of his characters) that the Berserker warships in his novels are not von Neumann machines themselves, but the larger complex of Berserker machines – including automated shipyards – do constitute a von Neumann machine. This again brings up the concept of an ecology of von Neumann machines, or even a von Neumann hive entity.
It is speculated in fiction that Berserkers could be created and launched by a xenophobic civilization (see Anvil of Stars, by Greg Bear, in Examples in fiction below) or could theoretically “mutate” from a more benign probe. For instance, a von Neumann ship designed for terraforming processes – mining a planet’s surface and adjusting its atmosphere to more human-friendly conditions – might malfunction and attack inhabited planets, killing their inhabitants in the process of changing the planetary environment, and then self-replicate and dispatch more ships to attack other planets.
All pages & panels from Ultimate Galactus – tell your friends about The Eater of Worlds!Read more "The Great Filter & Ultimate Galactus" | 0.806358 | 3.527065 |
Planet Earth. That shiny blue marble that has fascinated humanity since they first began to walk across its surface. And why shouldn’t it fascinate us? In addition to being our home and the place where life as we know it originated, it remains the only planet we know of where life thrives. And over the course of the past few centuries, we have learned much about Earth, which has only deepened our fascination with it.
But how much does the average person really know about the planet Earth? You’ve lived on Planet Earth all of your life, but how much do you really know about the ground underneath your feet? You probably have lots of interesting facts rattling around in your brain, but here are 10 more interesting facts about Earth that you may, or may not know.
Plate Tectonics Keep the Planet Comfortable:
Earth is the only planet in the Solar System with plate tectonics. Basically, the outer crust of the Earth is broken up into regions known as tectonic plates. These are floating on top of the magma interior of the Earth and can move against one another. When two plates collide, one plate will subduct (go underneath another), and where they pull apart, they will allow fresh crust to form.
This process is very important, and for a number of reasons. Not only does it lead to tectonic resurfacing and geological activity (i.e. earthquakes, volcanic eruptions, mountain-building, and oceanic trench formation), it is also intrinsic to the carbon cycle. When microscopic plants in the ocean die, they fall to the bottom of the ocean.
Over long periods of time, the remnants of this life, rich in carbon, are carried back into the interior of the Earth and recycled. This pulls carbon out of the atmosphere, which makes sure we don’t suffer a runaway greenhouse effect, which is what happened on Venus. Without the action of plate tectonics, there would be no way to recycle this carbon, and the Earth would become an overheated, hellish place.
Earth is Almost a Sphere:
Many people tend to think that the Earth is a sphere. In fact, between the 6th cenury BCE and the modern era, this remained the scientific consensus. But thanks to modern astronomy and space travel, scientists have since come to understand that the Earth is actually shaped like a flattened sphere (aka. an oblate spheroid).
This shape is similar to a sphere, but where the poles are flattened and the equator bulges. In the case of the Earth, this bulge is due to our planet’s rotation. This means that the measurement from pole to pole is about 43 km less than the diameter of Earth across the equator. Even though the tallest mountain on Earth is Mount Everest, the feature that’s furthest from the center of the Earth is actually Mount Chimborazo in Ecuador.
Earth is Mostly Iron, Oxygen and Silicon:
If you could separate the Earth out into piles of material, you’d get 32.1 % iron, 30.1% oxygen, 15.1% silicon, and 13.9% magnesium. Of course, most of this iron is actually located at the core of the Earth. If you could actually get down and sample the core, it would be 88% iron. And if you sampled the Earth’s crust, you’d find that 47% of it is oxygen.
70% of the Earth’s Surface is Covered in Water:
When astronauts first went into the space, they looked back at the Earth with human eyes for the first time. Based on their observations, the Earth acquired the nickname the “Blue Planet:. And it’s no surprise, seeing as how 70% of our planet is covered with oceans. The remaining 30% is the solid crust that is located above sea level, hence why it is called the “continental crust”.
The Earth’s Atmosphere Extends to a Distance of 10,000 km:
Earth’s atmosphere is thickest within the first 50 km from the surface or so, but it actually reaches out to about 10,000 km into space. It is made up of five main layers – the Troposphere, the Stratosphere, the Mesosphere, the Thermosphere, and the Exosphere. As a rule, air pressure and density decrease the higher one goes into the atmosphere and the farther one is from the surface.
The bulk of the Earth’s atmosphere is down near the Earth itself. In fact, 75% of the Earth’s atmosphere is contained within the first 11 km above the planet’s surface. However, the outermost layer (the Exosphere) is the largest, extending from the exobase – located at the top of the thermosphere at an altitude of about 700 km above sea level – to about 10,000 km (6,200 mi). The exosphere merges with the emptiness of outer space, where there is no atmosphere.
The exosphere is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules – including nitrogen, oxygen and carbon dioxide. The atoms and molecules are so far apart that the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or with the solar wind.
Want more planet Earth facts? We’re halfway through. Here come 5 more!
The Earth’s Molten Iron Core Creates a Magnetic Field:
The Earth is like a great big magnet, with poles at the top and bottom near to the actual geographic poles. The magnetic field it creates extends thousands of kilometers out from the surface of the Earth – forming a region called the “magnetosphere“. Scientists think that this magnetic field is generated by the molten outer core of the Earth, where heat creates convection motions of conducting materials to generate electric currents.
The magnetic field and electric currents in and around Earth generate complex forces that have immeasurable impact on every day life. The field can be thought of as a huge bubble, protecting us from cosmic radiation and charged particles that bombard Earth in solar winds. It’s shaped by winds of particles blowing from the sun called the solar wind, the reason it’s flattened on the “sun-side” and swept out into a long tail on the opposite side of the Earth.
Be grateful for the magnetosphere. Without it, particles from the Sun’s solar wind would hit the Earth directly, exposing the surface of the planet to significant amounts of radiation. Instead, the magnetosphere channels the solar wind around the Earth, protecting us from harm. Scientists have also theorized that Mars’ thin atmosphere is due to it having a weak magnetosphere compared to Earth’s, which allowed solar wind to slowly strip it away.
Earth Doesn’t Take 24 Hours to Rotate on its Axis:
It actually takes 23 hours, 56 minutes and 4 seconds for the Earth to rotate once completely on its axis, which astronomers refer to as a Sidereal Day. Now wait a second, doesn’t that mean that a day is 4 minutes shorter than we think it is? You’d think that this time would add up, day by day, and within a few months, day would be night, and night would be day.
But remember that the Earth orbits around the Sun. Every day, the Sun moves compared to the background stars by about 1° – about the size of the Moon in the sky. And so, if you add up that little motion from the Sun that we see because the Earth is orbiting around it, as well as the rotation on its axis, you get a total of 24 hours.
This is what is known as a Solar Day, which – contrary to a Sidereal Day – is the amount of time it takes the Sun to return to the same place in the sky. Knowing the difference between the two is to know the difference between how long it takes the stars to show up in the same spot in the sky, and the it takes for the sun to rise and set once.
A year on Earth isn’t 365 days:
It’s actually 365.2564 days. It’s this extra .2564 days that creates the need for a Leap Year once ever four years. That’s why we tack on an extra day in February every four years – 2004, 2008, 2012, etc. The exceptions to this rule is if the year in question is divisible by 100 (1900, 2100, etc), unless it divisible by 400 (1600, 2000, etc).
Earth has 1 Moon and 2 Co-Orbital Satellites:
As you’re probably aware, Earth has 1 moon (aka. The Moon). Plenty is known about this body and we have written many articles about it, so we won’t go into much detail there. But did you know there are 2 additional asteroids locked into a co-orbital orbits with Earth? They’re called 3753 Cruithne and 2002 AA29, which are part of a larger population of asteroids known as Near-Earth Objects (NEOs).
The asteroid known as 3753 Cruithne measures 5 km across, and is sometimes called “Earth’s second moon”. It doesn’t actually orbit the Earth, but has a synchronized orbit with our home planet. It also has an orbit that makes it look like it’s following the Earth in orbit, but it’s actually following its own, distinct path around the Sun.
Meanwhile, 2002 AA29 is only 60 meters across and makes a horseshoe orbit around the Earth that brings it close to the planet every 95 years. In about 600 years, it will appear to circle Earth in a quasi-satellite orbit. Scientists have suggested that it might make a good target for a space exploration mission.
Earth is the Only Planet Known to Have Life:
We’ve discovered past evidence of water and organic molecules on Mars, and the building blocks of life on Saturn’s moon Titan. We can see amino acids in nebulae in deep space. And scientists have speculated about the possible existence of life beneath the icy crust of Jupiter’s moon Europa and Saturn’s moon Titan. But Earth is the only place life has actually been discovered.
But if there is life on other planets, scientists are building the experiments that will help find it. For instance, NASA just announced the creation of the Nexus for Exoplanet System Science (NExSS), which will spend the coming years going through the data sent back by the Kepler space telescope (and other missions that have yet to be launched) for signs of life on extra-solar planets.
Giant radio dishes are currently scan distant stars, listening for the characteristic signals of intelligent life reaching out across interstellar space. And newer space telescopes, such as NASA’s James Webb Telescope, the Transiting Exoplanet Survey Satellite (TESS), and the European Space Agency’s Darwin mission might just be powerful enough to sense the presence of life on other worlds.
But for now, Earth remains the only place we know of where there’s life. Now that is an interesting fact!
We have written many interesting articles about planet Earth here on Universe Today. Here’s What is the Highest Place on Earth?, What is the Diameter of the Earth?, What is the Closest Planet to Earth?, What is the Surface Temperature of Earth? and The Rotation of the Earth?
Other articles include how fast the Earth rotates, and here’s an article about the closest star to Earth. If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.
And there’s even an Astronomy Cast episode on the subject of planet Earth. | 0.905051 | 3.309346 |
IWC Da Vinci Perpetual Chronograph
Say you’ve got £10,000 weighing down your wallet and you’re looking to trade it for a watch. If you’re lucky, you could grab Rolex’s latest, greatest ceramic Daytona, but what about this instead: a mechanical perpetual calendar chronograph and change.
As far as complications go, the perpetual calendar is right up there, one of the most intricate and highly revered mechanisms in watchmaking. You may think that sounds like hyperbole, especially in an age where a device small enough to sit on your wrist can access all the information in the world, but there’s something really quite remarkable about the perpetual calendar that’s worth digging a little deeper on.
It’s worth bearing in mind that the units of time measured by a perpetual calendar—that is to say, seconds, hours, minutes, days, dates, months, moonphase, years and leap years—took thousands of years to perfect. Establishing time is no easy task, and with each generation of civilisation, from Palaeolithic humans tracking the moon 6,000 years ago, to the astronomical calendars of the Mayans 4,000 years ago, and on to the Roman Julian calendar 2,000 years ago and even the Gregorian calendars we use today, our gauge of time has been slowly, slowly refined to sync perfectly with our place in the universe.
Time and timekeeping fall hand-in-hand—rather, the improvement of technology allows for better measurement and recording of the astronomical events that gave birth to the system of measurement that we now consider to be our fourth dimension. Now we know that we are on a planet spinning at 1,000mph, orbiting the sun at 100,000 mph, which orbits our galaxy at 500,000 mph, which itself is travelling through the universe at over 1,000,000 mph, the way we determine the particulars of time has become more and more refined.
For horologers 300 years ago, however, much of that information was still a mystery. What we did know is that the orbit of the Earth around the sun is 365.2422 days, and that poses something of a problem. A day is based on one rotation of the Earth, fine, but as bad luck—or rather, the randomness of nature—would have it, a complete orbit doesn’t last an exact amount of days.
But 365.2422 is almost 365-and-a-quarter, so the solution was originally thought to be simple enough: make a year 365 days exactly and tack on another day every four years—the leap year. This is where the perpetual calendar meets its match, because the leap year just isn’t good enough, that pesky 0.0078 of a day causing slip over time—a lot of time. This is why every three out of four centuries the leap year is skipped, and why your perpetual calendar watch will need to be adjusted by a watchmaker in the year 2100.
So, here’s where we are with it: through lots of mathematics and hand-drawn blueprints, English watchmaker Thomas Mudge built a pocket watch that could tell the user exactly what day it was, leap year and all. This was in 1762, barely a decade after the Gregorian calendar was even adopted in England.
Some 223 years later, IWC watchmaker Kurt Klaus made a similar step forward, simplifying this mechanism that had tormented the minds of many a watchmaker in the centuries before such that it could be set entirely by the crown. Typically, an array of hidden pushers was necessary to control each part of the movement’s display, but by using a single program wheel, notched into four years’ worth of teeth to accommodate the length of each month including the leap year, Klaus made all that complexity completely redundant.
The space he saved left room for another remarkable complication: the chronograph. This is a device that doesn’t get as much recognition as it perhaps deserves. It may be common, but it is still remarkably complex. A typical perpetual calendar for example, has in the region of 300–350 parts; a chronograph is pushing 300, an indication of just how much is going on to make this on-demand complication work. It wasn’t until 50 years after the perpetual calendar that the chronograph was first invented by Louis Moinet, and another century still before a chronograph was developed for a wristwatch. A further 50 years were needed to get one running automatically. It’s the need to engage and disengage with the perpetual motion of the escapement at a moment’s notice that makes it such a fiendishly difficult complication to master.
It was on death’s door that this swansong from IWC emerged, the Da Vinci Perpetual Calendar Chronograph. The development of Kurt Klaus’ perpetual calendar with a chronograph on top, in a case penned by IWC designer Hano Burtscher, was a last-ditch attempt to demonstrate the importance of a mechanical watch in a newly emerging digital world. They very much knew it could well be their last.
But it wasn’t. This revolutionary mechanism may have been no match for circuit boards and electricity, but its ingenuity, affordability and usability sold more perpetual calendar watches for IWC than the rest of the industry combined.
Today, the IWC IW3750 Da Vinci Perpetual Calendar Chronograph may not be the biggest, boldest, most exciting watch on the market, but for less money than a Rolex Daytona, it offers not just a slice, but a whole greedy handful of watchmaking history within its 39mm case. So many great names have touched the journey of this watch through its many centuries and even millennia of development, that to hold it all in the palm of the hand is really rather special indeed.
Looking for a IWC watch? Click here to shop now | 0.814012 | 3.354829 |
From: Jet Propulsion Laboratory
Posted: Monday, January 7, 2013
NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, set its X-ray eyes on a spiral galaxy and caught the brilliant glow of two black holes lurking inside.
The new image is being released Monday along with NuSTAR's view of the supernova remnant Cassiopeia A, at the American Astronomical Society meeting in Long Beach, Calif.
"These new images showcase why NuSTAR is giving us an unprecedented look at the cosmos," said Lou Kaluzienski, NuSTAR Program Scientist at NASA headquarters in Washington. "With NuSTAR's greater sensitivity and imaging capability, we're getting a wealth of new information on a wide array of cosmic phenomena in the high-energy X-ray portion of the electromagnetic spectrum."
Launched last June, NuSTAR is the first orbiting telescope with the ability to focus high-energy X-ray light. It can view objects in considerably greater detail than previous missions operating at similar wavelengths. Since launch, the NuSTAR team has been fine-tuning the telescope, which includes a mast the length of a school bus connecting the mirrors and detectors.
The mission has looked at a range of extreme, high-energy objects already, including black holes near and far, and the incredibly dense cores of dead stars. In addition, NuSTAR has begun black-hole searches in the inner region of the Milky Way galaxy and in distant galaxies in the universe.
Among the telescope's targets is the spiral galaxy IC342, also known as Caldwell 5, featured in one of the two new images. This galaxy lies 7 million light-years away in the constellation Camelopardalis (the Giraffe). Previous X-ray observations of the galaxy from NASA's Chandra X-ray Observatory revealed the presence of two blinding black holes, called ultraluminous X-ray sources (ULXs).
How ULXs can shine so brilliantly is an ongoing mystery in astronomy. While these black holes are not as powerful as the supermassive black hole at the hearts of galaxies, they are more than 10 times brighter than the stellar-mass black holes peppered among the stars in our own galaxy. Astronomers think ULXs could be less common intermediate-mass black holes, with a few thousand times the mass of our sun, or smaller stellar-mass black holes in an unusually bright state. A third possibility is that these black holes don't fit neatly into either category.
"High-energy X-rays hold a key to unlocking the mystery surrounding these objects," said Fiona Harrison, NuSTAR principal investigator at the California Institute of Technology in Pasadena. "Whether they are massive black holes, or there is new physics in how they feed, the answer is going to be fascinating."
In the image, the two bright spots that appear entangled in the arms of the IC342 galaxy are the black holes. High-energy X-ray light has been translated into the color magenta, while the galaxy itself is shown in visible light.
"Before NuSTAR, high-energy X-ray pictures of this galaxy and the two black holes would be so fuzzy that everything would appear as one pixel," said Harrison.
The second image features the well-known, historical supernova remnant Cassiopeia A, located 11,000 light-years away in the constellation Cassiopeia. The color blue indicates the highest energy X-ray light seen by NuSTAR, while red and green signify the lower end of NuSTAR's energy range. The blue region is where the shock wave from the supernova blast is slamming into material surrounding it, accelerating particles to nearly the speed of light. As the particles speed up, they give off a type of light known as synchrotron radiation. NuSTAR will be able to determine for the first time how energetic the particles are, and address the mystery of what causes them to reach such great speeds.
"Cas A is the poster child for studying how massive stars explode and also provides us a clue to the origin of the high-energy particles, or cosmic rays, that we see here on Earth," said Brian Grefenstette of Caltech, a lead researcher on the observations. "With NuSTAR, we can study where, as well as how, particles are accelerated to such ultra-relativistic energies in the remnant left behind by the supernova explosion."
For more information about NuSTAR and to view the new images, visit: http://www.nasa.gov/nustar
// end // | 0.887267 | 3.868978 |
ESA’s Cluster spacecraft were in the right place at the right time on September 15, 2001. They flew through a region of the Earth’s magnetosphere at the exact moment that it reconfigured itself. The wealth of data will help scientists better model interactions between the Earth’s magnetosphere and the solar wind, as well as the magnetic fields around other stars and exotic objects with powerful magnetic fields.
ESA’s spacecraft constellation Cluster has hit the magnetic bull’s-eye. The four spacecraft surrounded a region within which the Earth’s magnetic field was spontaneously reconfiguring itself.
This is the first time such an observation has been made and gives astronomers a unique insight into the physical process responsible for the most powerful explosions that can occur in the Solar System: the magnetic reconnection.
When looking at the static pattern of iron filings around a bar magnet, it is difficult to imagine how changeable and violent magnetic fields can be in other situations.
In space, different regions of magnetism behave somewhat like large magnetic bubbles, each containing electrified gas known as plasma. When the bubbles meet and are pushed together, their magnetic fields can break and reconnect, forming a more stable magnetic configuration. This reconnection of magnetic fields generates jets of particles and heats the plasma.
At the very heart of a reconnection event, there must be a three dimensional zone where the magnetic fields break and reconnect. Scientists call this region the null point but, until now, have never been able to positively identify one, as it requires at least four simultaneous points of measurements.
On 15 September 2001, the four Cluster spacecraft were passing behind the Earth. They were flying in a tetrahedral formation with separations between the spacecraft of over 1 000 kilometres. As they flew through the Earth’s magnetotail, which stretches out behind the night-time side of our planet, they surrounded one of the suspected null points.
The data returned by the spacecraft have been extensively analysed by an international team of scientists led by Dr. C. Xiao from Chinese Academy of Sciences, Prof. Pu from Peking University, Prof. Wang from Dalian University of Technogy. Xiao and his colleagues used the Cluster data to deduce the three-dimensional structure and size of the null point, revealing a surprise.
The null point exists in an unexpected vortex structure about 500 kilometres across. “This characteristic size has never been reported before in observations, theory or simulations,” say Xiao, Pu and Wang.
This result is a major achievement for the Cluster mission as it gives scientists their first look at the very heart of the reconnection process.
Throughout the Universe, magnetic reconnection is thought to be a fundamental process that drives many powerful phenomena, such as the jets of radiation seen escaping from distant black holes, and the powerful solar flares in our own Solar system that can release more energy than a billion atomic bombs.
On a smaller scale, reconnection at the dayside boundary of the Earth’s magnetic field allows solar gas through, triggering a specific type of aurora called ‘proton aurora’.
Understanding what sparks magnetic reconnection will also help scientists trying to harness nuclear fusion for energy production. In tokamak fusion reactors, spontaneous magnetic reconfigurations rob the process of its controllability. By understanding how magnetic fields reconnect, fusion scientists hope to be able to design better reactors that prevent this from taking place.
Having identified one null point, the team now hopes to score future bull’s-eyes to compare nulls and see whether their first detection possessed a configuration that is rare or common.
Original Source: ESA News Release | 0.858003 | 3.942952 |
A constellation is an area of the celestial sphere as defined by the International Astronomical Union (IAU) in the early 20th century.
Constellations are typically grouped around asterisms, patterns formed by prominent, relatively bright stars that appear to be close to each other in the night sky.
These star patterns themselves are often mistakenly called constellations, whether they are famous asterisms like Orion’s Belt, the Big Dipper or the Southern Cross, or less familiar patterns formed by stars visible to the naked eye and belonging to one of the 88 constellations.
While the modern constellations are seen as areas of the sky used for orientation and arranged in a grid-like map of the celestial sphere, the term is still colloquially used to refer to the visible star patterns and prominent asterisms, which are only smaller elements found in constellations.
The constellations themselves are much larger than asterisms and occupy considerably larger areas than the prominent star patterns.
The borders of the modern 88 constellations were defined by the IAU in the early 20th century. 48 of the modern constellations, mainly those visible in the northern hemisphere, are based on the Greek constellations, documented by the astronomer Claudius Ptolemy in the 2nd century.
The celestial sphere was divided into 88 official constellations in 1922 by the IAU with the help of American astronomer Henry Norris Russell. In 1930, Belgian astronomer Eugène Delporte devised the boundaries between the modern constellations along horizontal and vertical lines. Delporte based his work on that of Benjamin A. Gould.
Most of the modern 88 constellations kept the names of their predecessors, which were the 50 ancient constellations, dating back to Greece, Rome and the Middle East, and the 38 constellations that were created more recently.
However, there were many other constellations over the millennia, and they weren’t the same from one culture to the next. Some of these historical constellations – including Quadrans Muralis, created in 1795 and later divided between Draco and Boötes, with the name preserved only in the Quadrantids meteor shower – weren’t widely recognized and fell out of use, while others were split into smaller areas of the sky.
The Greek constellation Argo Navis, for instance, that represented the ship of Jason and the Argonauts, was divided by the French astronomer Nicolas Louis de Lacaille into Carina, Vela, and Puppis, three smaller constellations representing the ship’s keel, sails, and stern respectively. The new division was introduced in 1763, in the star catalogue Coelum Australe Stelliferum, published after de Lacaille’s death.
Today, when talking about stars and deep sky objects being ‘in’ a given constellation, astronomers mean to say that they lie within the defined boundaries of the constellation. Constellations themselves are not real, as the stars and deep sky objects (nebulae, galaxies, clusters) belonging to them lie at very different distances from Earth and only appear close to one another because they lie in the same line of sight when seen from Earth.
Since the stars and other visible objects are located at different distances, this also means that we are seeing them as they were at very different points in the past and not as they appear now. Antares in Scorpius, for instance, lies about 550 light years from Earth. We are therefore seeing it as it appeared some 550 years ago. The Trifid Nebula in Sagittarius is approximately 5,200 light years distant, so the image we are seeing is 5,200 years old. Galaxies lie at even greater distances. The famous Antennae Galaxies in Corvus are located some 45 million light years from Earth. This makes the images of the colliding pair 45 million years old.
Merriam-Webster dictionary defines the constellation as “a group of stars that forms a particular shape in the sky and has been given a name” or “any of 88 arbitrary configurations of stars or an area of the celestial sphere covering any of these configurations.”
Britannica defines the term, as used in astronomy, as “any of certain groupings of stars that were imagined – at least by those who named them – to form conspicuous configurations of objects or creatures in the sky.”
In ancient times, observers saw distinctive, identifiable patterns of stars in night sky, now called asterisms, and made up different kinds of stories that they associated with them.
Orion, the Hunter and Taurus, the Bull, for instance, were known to many cultures since antiquity and associated with a number of different legends. Once the first astronomers started creating star maps, the most familiar asterisms were included in the maps to become the first constellations.
The word constellation is derived from the Latin constellātiō, which can be translated as “set with stars.” The term comes from astrology, and was first used for asterisms that were believed to exert influence, as noted by Roman soldier and historian Ammianus Marcellinus in the 4th century.
In the English language, the word was also initially used in astrology, from the 14th century onwards, and referred to conjunctions of planets. The term wasn’t used in the modern sense – to refer to an area of the celestial sphere – until the mid-16th century.
The 48 Greek constellations listed by Ptolemy in his Almagest in the 2nd century, which formed the basis for the modern division, were based on the work of the Greek astronomer Eudoxus of Cnidus, who is credited for introducing Babylonian astronomy to Greece in the 4th century BC. 30 of these constellations date back to ancient times and some of them, including the constellations of the zodiac, have a history going all the way back to the Late Bronze Age.
Greek astronomers adopted Babylonian astronomy and, as a result, some of the Greek constellations contained the same stars as Babylonian ones, and were only listed under different names. The Almagest served as a basis for astronomy as taught from Late Antiquity to the Early Modern period in the west.
Many of the southern stars could not be seen by Greeks, Babylonians, Arabs, Chinese, or any other culture north of the equator. The modern southern constellations were not defined until the age of exploration. They were charted by Dutch navigators Frederick de Houtman and Pieter Dirkszoon Keyser in the late 16th century and then included in Johann Bayer’s star atlas Uranometria (1603).
Bayer added a total of 11 new constellations, including Tucana, Musca, Dorado, Indus and Phoenix. He also assigned Greek letters to a total of 1,564 stars in different constellations, giving the stars designations in the order of brightness, starting from Alpha. These were mostly kept until present day, which is why out of some 10,000 naked eye stars, 1,564 have Bayer designations, consisting of a Greek letter and the name of the constellation in genitive form (Alpha Centauri, Beta Tauri, Gamma Aquilae, etc.) Some of these stars also have proper names as they were bright enough to be seen by ancient cultures, so we know Alpha Scorpii as Antares, Alpha Aquilae as Altair, Alpha Canis Majoris as Sirius, Alpha Orionis as Betelgeuse, and Alpha Tauri as Aldebaran, to only name a few.
Several more constellations were added by the French astronomer Nicolas Louis de Lacaille in his catalogue published in 1756. Lacaille created 13 new constellations while mapping the southern skies from an observatory in South Africa. The Lacaille Family includes Octans, Fornax, Pictor, Antlia and Mensa, the last of which was named after Mons Mensa, or Table Mountain, which is where his observatory was located.
The International Astronomical Union, formed in 1919, set out to define the official boundaries between the constellations in the 1920s. Eugène Delporte adjusted the modern boundaries along lines of right ascension and declination for the epoch B1875.0. As a result of the precession of the equinoxes, the boundaries will eventually have to be re-adjusted. | 0.845878 | 3.92625 |
All of the space that surrounds us isn’t empty. We’ve always known the Milky Way was filled with great areas of turbulent gas, but we’ve never been able to see them… Until now. Professor Bryan Gaensler of the University of Sydney, Australia, and his team used a CSIRO radio telescope in eastern Australia to create this first-ever look which was published in Nature today.
“This is the first time anyone has been able to make a picture of this interstellar turbulence,” said Professor Gaensler. “People have been trying to do this for 30 years.”
So what’s the point behind the motion? Turbulence distributes magnetism, disperses heat from supernova events and even plays a role in star formation.
“We now plan to study turbulence throughout the Milky Way. Ultimately this will help us understand why some parts of the galaxy are hotter than others, and why stars form at particular times in particular places,” Professor Gaensler said.
Employing CSIRO’s Australia Telescope Compact Array because “it is one of the world’s best telescopes for this kind of work,” as Dr. Robert Braun, Chief Scientist at CSIRO Astronomy and Space Science, explained, the team set their sights about 10,000 light years away in the constellation of Norma. Their goal was to document the radio signals which emanate from that section of the Milky Way. As the radio waves pass through the swirling gas, they become polarized. This changes the direction in which the light waves can “vibrate” and the sensitive equipment can pick up on these small differentiations.
By measuring the polarization changes, the team was able to paint a radio portrait of the gaseous regions where the turbulence causes the density and magnetic fields to fluctuate wildly. The tendrils in the image are also important, too. They show just how fast changes are occurring – critical for their description. Team member Blakesley Burkhart, a PhD student from the University of Wisconsin, made several computer simulations of turbulent gas moving at different speeds. By matching the simulations with the actual image, the team concluded “the speed of the swirling in the turbulent interstellar gas is around 70,000 kilometers per hour — relatively slow by cosmic standards.”
Original Story Source: CSIRO Astronomy and Space Science News Release. For Further Reading: Low Mach number turbulence in interstellar gas revealed by radio polarization gradients. | 0.936897 | 3.616109 |
By Christopher Phillips
For The Beachcomber
We begin the month of December with the moon passing through its first quarter phase. As we move into the second week of the month, the moon will make its presence felt as its brightness increases. This will peak on Wednesday, Dec. 11, when the moon passes through its full phase. Provided the night is cloud-free, we will be able to appreciate a marvelous celestial sight in which the moon appears in the constellation of Taurus, and looks to be almost suspended between the horns of the celestial bull. The constellation of Orion can also be seen below the pair, with the great hunter’s bow aimed skyward toward both the moon and Taurus. This is nothing short of a quintessential winter sky display.
The intense brightness of the full moon will mean that only the brightest of stars will be visible during this period, with the best stargazing occurring at both the beginning and end of the month when the moon is waxing and waning respectively.
During these times, it may be possible to spot a bright pass of the International Space Station (ISS). Thursday, Dec. 5 will see the ISS pass from the west-north-west to the east-north-east, at 5:56 p.m. It will rise to an altitude of around 61 degrees, and provided we have a view clear of obstructions, we will be able to appreciate humanity’s first, permanently crewed, orbital outpost as it whips overhead at the astonishing speed of almost five miles per second. The ISS will make an additional bright pass on Sunday, Dec. 8, moving from the west-north-west to the south-east, at 5:55 p.m.
The December sky will be free of visible planets, for the most part, although it may be possible to catch a fleeting glimpse of Venus and Saturn, just after sunset in the southwest. However, a clear horizon that is free of obstructions will be needed to view these members of our solar family.
As we approach the end of the current year, we will be greeted with gloriously dark skies, perfect for stargazing, and the majesty of the winter sky will present itself in full. The constellation of Orion itself is worthy of your attention. Orion’s famous belt and sword hold a plethora of galactic wonders, including luminous blue giant stars. In the sword of Orion, just below the belt, we can see the Orion nebula. The nebula is a massive region of star formation in which new solar systems are born amongst clouds composed of the most basic cosmic ingredient, hydrogen. These clouds are vast, spanning many light-years, and their appearance is almost as that of waves, with swells and surges sculpted and driven by fierce stellar winds from hot newborn stars.
It may come as a surprise, but this stellar birthplace is visible to the naked eye on a clear night. Through a modest pair of binoculars or a small telescope, one can view this universal wonder as a small, fuzzy patch. However, do not be dissuaded by this modest view, because the nature and allure of this heavenly forge hold our gaze and stokes the fires of the human imagination on these cold winter nights.
I wish you clear skies for the month of December — and happy stargazing!
Christopher Phillips is based at the University of Washington, where he works as a research scientist on the Zwicky Transient Facility. | 0.908049 | 3.235537 |
One of the defining characteristics of the mysterious deep-space signals we call fast radio bursts is that they are unpredictable. They belch out across the cosmos without rhyme or reason, with no discernible pattern, making them incredibly hard to study.
Now, for the first time, astronomers have found a fast radio burst (FRB) that repeats on a regular cycle.
Every 16.35 days, the signal named FRB 180916.J0158+65 follows a similar pattern. For four days, it will spit out a burst or two every hour. Then it falls silent for 12 days. Then the whole thing repeats.
Astronomers with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Collaboration in Canada observed this cycle for a total of 409 days. We don't yet know what it means; but it could be another piece in the complicated conundrum of FRBs. The research has been uploaded to pre-print server arXiv, where it awaits scrutiny from other experts in the field.
It's easy to become somewhat obsessed with fast radio bursts, a fascinating space mystery that has so far defied any attempts at a comprehensive explanation.
To recap, FRBs are hugely energetic flares of radiation in the radio spectrum that last just a few milliseconds at most. In that timeframe, they can discharge as much power as hundreds of millions of Suns.
Most of them spark once, and we have never detected them again. This makes it rather difficult to track these bursts down to a source galaxy. Some FRBs spit out repeating radio flares, but wildly unpredictably. These are easier to track to a galaxy, but so far, that hasn't brought us a great deal closer to an explanation.
Last year, the CHIME collaboration announced they had detected a whopping eight new repeating fast radio bursts, bringing the then-total of repeaters to 10 out of over 150 FRB sources. (Another paper recently brought that total up to 11.)
FRB 180916.J0158+65 was among the eight repeaters included in last year's haul; apart from its repeat bursts, initially it didn't appear to be anything special. But as the CHIME experiment continued to stare at the sky, a pattern emerged.
This is exciting, because it offers new information that can be used to try and model what could be causing FRB 180916.J0158+65.
"The discovery of a 16.35-day periodicity in a repeating FRB source is an important clue to the nature of this object," the researchers wrote in their paper.
Other objects that demonstrate periodicity tend to be binary systems - stars and black holes. The 16.35-day period could be the orbital period, with the FRB object only facing Earth during a certain part of the orbit.
FRB 180916.J0158+65 is one of the handful of FRBs that have been traced back to a galaxy. It's on the outskirts of a spiral galaxy 500 million light-years away, in a star-forming region. This means a supermassive black hole is unlikely, but a stellar-mass black hole is possible.
"The single constraint on the orbital period still allows several orders of magnitude range in companion mass amongst known stellar-mass compact object binaries: from so-called 'black widow' binary systems, consisting of a low-mass star and a powerful millisecond pulsar whose wind ablates the companion (albeit typically with few-hour orbital periods), to massive O/B stars with highly eccentric companion pulsar orbits," the researchers wrote.
Alternatively, winds from the companion object, or tidal disruptions from a black hole, may periodically somehow block the FRB radiation.
It also can't be ruled out that the FRB source is a single, lone object such as a magnetar or X-ray pulsar, although the researchers note this explanation is a little harder to reconcile with the data. That's because those objects have a wobbling rotation that produces periodicity, and none are known to wobble that slowly.
And radio pulsars that do have periodic intervals of several days are orders of magnitude fainter than FRBs. So it's still a mystery.
But remember that 11th repeater we mentioned earlier? It was found coming from an FRB astronomers had thought was a one-off; its repeats were simply too faint for the equipment that had initially been used to look for them.
This suggests that many more FRBs could be repeating, but outside our detection range. And the fact that FRB 180916.J0158+65 seemed more or less the same as other FRBs could mean that other repeating FRBs are also on a cycle - we just haven't detected those cycles yet.
So, the next step would be, of course, to continue staring at FRB 180916.J0158+65 for a bit. But it also would be pretty interesting to try and see if periodicity can be detected in other bursts as well.
"Future observations, both intensity and polarimetric, and at all wavebands, could distinguish among models and are strongly encouraged," the researchers wrote, "as are searches for periodicities in other repeaters, to see if the phenomenon is generic."
The research is available on arXiv ahead of peer review. | 0.850702 | 3.936119 |
Newton's inverse-square force law
is elegant in its simplicity and leads to predictions qualitatively similar to observations, but it does not graduate to become a physical theory until ample quantitative data supports it.
In this quiz, we will investigate how scientists resolve theoretical models with experimental data. Specifically, we test the hypothesis that is proportional to by examining a set of measurements of the orbital periods and radii of Jupiter's moons.
In the next few questions we will
Possibly the most challenging step in validating a theoretical model with observational data is deciding on which data are most directly relevant. Here, we have basically identified that orbital radius and period are to be used as a test of Newton's gravitational law.
How Newton and concurrent astronomers whittled down all possible data to these two variables is too arduous to describe here. Clearly, directly measuring the force between Jupiter and any of its moon's is not feasible. It helped that these data are accessible to any patient astronomer with a decent telescope. Our task is to determine how Newton's gravitational law relates these variables.
The orbital period is how long it takes for one of Jupiter's moons to complete one revolution around the planet, but time does not appear explicitly in Modeling our approach on the last quiz where we related the Moon's centripetal acceleration to let's look for a way to pull into this relationship.
If the orbital radius is which choice expresses centripetal acceleration in terms of ?
According to the result of the last quiz, we suspect that but we would like to assess whether data from Jupiter's moons supports the same theory.
Thus, let's introduce a parameter into the force law
expressing the deviation of the power law from an inverse-square law. We will use the data to estimate The closer is to then the stronger the support for Newton's inverse-square law.
Using the result of the previous question, and Newton's second law, which choice expresses orbital period in terms of orbital radius ?
In a linear regression, the calculated parameters are the slope and intercept of a line that best fits a set of data.
Plotting the natural log of period and orbital radius of the moon data, they fall almost exactly on a line. The slope and intercept of the best fit line are shown next to the plot.
Taking the natural log of your model relationship between and in the previous problem, what is the order of magnitude of the derivation ?
Given that Jupiter's mass is , make a prediction for proportionality constant from this data. The accepted value of the proportionality constant in Newtonian gravity is By what fraction does the predicted value deviate from the accepted value?
Orbital data has been used over the last several centuries to validate Newton's universal law of gravity between massive bodies, as well as to validate its only known improvement (general relativity). Here, we've used it to narrow down the functional form of gravity to within one part in of the exponent on
We can summarize our findings as follows:
Newtonian gravity is defined by the force law where is the magnitude of the displacement of the centers of two masses and with The force between the masses is always attractive, directed between the centers of and
Newton's work unearthed the connection between falling objects and orbital motion. His theory formed the foundation of orbital mechanics, more than 250 years before the first man-made object was launched into orbit in 1957. Today, with more than 2,000 man-made satellites in orbit around Earth (and even more space junk), Newton's theory remains more relevant today than ever.
Newton's theory withstands the test of time because it exemplifies a bedrock assumption of modern science: that the laws of nature are systematic and universal, which was not a widely held belief in his time. | 0.867083 | 3.95926 |
If you have ever gazed at the stars and wondered what could be out there then you will be happy to know we are now closer to finding out.
A new study by the Centre for Robotics and Neural Systems (CRNS) at Plymouth University was presented on April 4 at the European Week of Astronomy and Space Science that explores how artificial intelligence (AI) can be used to identify the possibility of alien life on other planets.
Models that replicate brain patterns
The research is based on the use of artificial neural networks (ANNs), tools commonly used in machine learning. ANNs are computational models inspired by the structure of biological neural networks which replicate the way the human brain learns.
As such, ANNs can be used to identify patterns too complex for human brains to process. In this study, CRNS scientists took information from the spectral profiles (atmospheric observations) of planet types from NASA’s Planetary Spectrum Generator and used ANNs to analyze them in terms of habitability (the possibility of sustaining life).
They created a network that was fed over a hundred different spectral profiles, each with hundreds of habitability-related parameters. Sorting through such an impressive amount of information would take humans years but the ANNs successfully analyzed and classified the data in minutes.
The data was arranged into five planet types: present-day Earth, the early Earth, Mars, Venus or Saturn’s moon Titan. These types were chosen for having compositions and atmospheres that were the most potentially habitable in our solar system.
System to pinpoint habitable exoplanets
PhD student and leader of the project Christopher Bishop said in a statement: “We’re currently interested in these ANNs for prioritising exploration for a hypothetical, intelligent, interstellar spacecraft scanning an exoplanet system at range.”
The team reported that their system adapted well even when fed new and alien spectral profiles. The hope now is that ANNs can be used in the future to distinguish exoplanets with a high probability for supporting life.
Bishop, who is also a professor in Artificial Intelligence and Cognition Angelo Cangelosi, said: “We're also looking at the use of large area, deployable, planar Fresnel antennas to get data back to Earth from an interstellar probe at large distances. This would be needed if the technology is used in robotic spacecraft in the future.”
This development comes at a good time as NASA’s TESS spacecraft is scheduled to launch in just a few weeks and could use support in analyzing the large amount of data that the mission is bound to collect.
“Given the results so far, this method may prove to be extremely useful for categorising different types of exoplanets using results from ground–based and near Earth observatories” said Dr. Angelo Cangelosi, the supervisor of the project. | 0.904102 | 3.180176 |
The Earth's core is the part of Earth in the middle of our planet. It has a solid inner core and a liquid outer core. The temperature of the outer core ranges from 4400 °C in the outer regions to 6100 °C near the inner core.
The outer core of the Earth is a liquid layer about 2,260 kilometers thick. It is made of iron and nickel. This is above the Earth's solid inner core and below the mantle. Its outer boundary is 2,890 km (1,800 mi) beneath the Earth's surface. The transition between the inner core and outer core is approximately 5,000 km (3,100 mi) beneath the Earth's surface.
The temperature of the outer core ranges from 4400 °C in the outer regions to 6100 °C near the inner core. Eddy currents in the nickel iron fluid of the outer core are believed to influence the Earth's magnetic field. Convection in the outer core, combined with the Coriolis effect, gives rise to Earth's magnetic field. The solid inner core is too hot to hold a permanent magnetic field. It may stabilize the magnetic field generated by the liquid outer core.
Without the outer core, life on Earth would be very different. Convection of liquid metals in the outer core creates the Earth's magnetic field. This magnetic field extends outward from the Earth for several thousand kilometers, and creates a protective magnetosphere around the Earth that deflects the Sun's solar wind. Without this field, the solar wind would directly strike the Earth's atmosphere. This might have removed the Earth's atmosphere, making the planet nearly lifeless. It may have happened to Mars.
The inner core of the Earth, as detected by seismology, is a solid sphere about 1,216 km (760 mi) in radius, or about 70% that of the Moon. It is believed to be an iron–nickel alloy, and may have a temperature similar to the Sun's surface, about 5778 K (5505 °C).
In 2015, Prof Xiaodong Song from the University of Illinois and other researchers in China suggested the inner core has two layers. The seismic wave data suggests that crystals in the "inner inner core" are in an east-to-west direction. Those in the "outer inner core" are lined up north to south. Another scientist commented: "If this is true, it would imply that something very substantial happened to flip the orientation of the core to turn the alignment of crystals in the inner core north-south as is seen today in its outer parts". Other scientists are checking their data.
- Bruce A. Buffett 2010. Tidal dissipation and the strength of the Earth’s internal magnetic field. Nature 468, 952-954. doi:10.1038/nature09643
- First measurement of magnetic field inside Earth's core. Science20.com. Retrieved on 2012-01-27.
- Woodrow L. Shew, Daniel P. Lathrop 2005. Liquid sodium model of geophysical core convection. Physics of the Earth and Planetary Interiors 153 136–149
- Kent C. Condie 1997. Plate tectonics, Butterworth-Heinemann; 4th ed. p140 ISBN 978-0750633864
- "Module title". ceo.scec.org.
- Morelle, Rebecca 2015. BBC News Science & Environment. Heart of Earth's inner core revealed. | 0.800104 | 3.768744 |
Cosmic rays continue to puzzle scientists a century after the fast-moving particles were discovered.
Austrian scientist Victor Hess first cottoned on to the existence of cosmic rays after a high-altitude balloon flight on Aug. 7, 1912. In the 100 years since, researchers have learned a lot about these highly energetic particles, which constantly bombard Earth from outer space. But important questions remain, including where exactly they come from.
Scientists got on the trail of cosmic rays in the 1780s, when French physicist Charles-Augustin de Coulomb noticed that an electrically charged sphere spontaneously lost its charge. This seemed strange, because at the time scientists believed air to be an insulator rather than a conductor.
Further experiments demonstrated, however, that air becomes a conductor when its molecules are ionized — given a net positive or negative electrical charge — by interaction with charged particles or X-rays. [Video: Monster Stars Spit Cosmic Rays]
The source of these particles baffled scientists, as experiments showed that objects were losing their charge even when shielded by large chunks of lead, which blocks X-rays and other radioactive sources.
That's where Hess' landmark 1912 balloon flight comes in. At an altitude of 17,400 feet (5,300 meters), he measured ionizing radiation levels about three times greater than those seen on the ground. Hess concluded that this radiation is penetrating Earth's atmosphere from outer space, an insight that earned him the Nobel Prize in Physics in 1936.
Hess had discovered cosmic rays, charged subatomic particles that streak through space at nearly the speed of light. They're thought to be atomic nuclei from the entire range of naturally occurring elements, though the vast majority appear to be protons (hydrogen nuclei).
The source of cosmic rays, however, has remained mysterious. Scientists aren't sure which cosmic phenomena are accelerating the particles to their fantastic speeds.
"The universe is full of natural particle accelerators, as for example in supernova explosions, in binary star systems or in active galactic nuclei," said Christian Stegmann, head of the German Electron Synchrotron research center (known by its German acronym, DESY) at Zeuthen, in a statement.
"So far, only 150 of these objects are known to us, and we have just an initial physical understanding of these fascinating systems," Stegmann added.
DESY is helping to organize a symposium to mark the 100th anniversary of the discovery of cosmic rays. From Aug. 6-8, scientists from around the world will meet in Bad Saarow in the German state of Brandenburg, where Hess landed his balloon a century ago. They'll present and discuss the latest research about the ultra-speedy particles — including ideas about how to unlock their long-held secrets. | 0.807372 | 4.057704 |
So far so good, except that as we all know, Venus's surface temperature is that of molten lead, its pressure is higher than in the Marianas Trench and after CO2 and Nitrogen, the most common atmospheric gas is sulfuric acid. Also it's gravity is about the same as Earth and so would require a full sized ( Titan or bigger) acid proof rocket to get the crew back into orbit in the unlikely event they weren't baked, dissolved, and crushed.
This is why Venus has not been on N.A.S.A.'s shortlist for places to visit.
Fortunately there is an amazingly cutting edge technology that allows a manned survey of Venus.
The High Altitude Venus Operational Concept takes advantage of the fact that temperatures 34 miles above the surface are around 80 degrees and the pressure is that of Boulder Colorado. However because the CO2 atmosphere is much denser than nitrogen, earth air is a lifting gas at that altitude.
"Dirigibles in space!"
So the idea is to inflate the "landing" party's ship on the way down and have it double as a 423 foot long airship, (Actually a manned, dirigible, rockoon) and then fly around the planet for a few weeks or months doing more detailed surveys than can be done from orbit and tele-operating probes on the surface. This also allows for detailed chemical analysis of the atmosphere, using sensors lowered on tethers into the dense lower atmosphere, much like a oceanographer uses Nansen bottles to sample the deep.
After completing the mission, the Blimp will launch a rocket from high altitude (Like a Pegasus) and transport the crew into space, where they'll rendezvous with their mother ship and return to Earth.
Assuming an acid proof blimp, Venus is actually much safer than Mars for the astronauts. The gravity is about the same as Earth, the thick atmosphere plus the planet's weak magnetic field would protect the crew from cosmic rays even better than earth does. Venus is much easier to get to and launch windows open much more often than they do for Mars. Two precursor missions, one manned but confined to orbit and one using a 1 quarter scale drone dirigible to test acid proofing and demonstrate that the inflation/deployment system works would precede the crewed Venus blimp sortie..
This is a very good idea for an icebreaker mission. It's more advanced than the moon or asteroid missions currently in the pipeline but still far quicker, easier (and probably safer) than the upcoming mission to Mars. Such a mission would be far shorter in duration than a Mars landing and would be a nice stepping stone on the way to those missions as well as expeditions to the asteroids Mercury, Ceres and Callisto. Flags and footprints albeit without flags or dirty feet (but with a blimp!).
So, today we've discussed rockets, space travel, a manned mission to the planet Venus and an airship, nay, a rockoon even! The only thing that would make this cooler is a swordfight.
Or floating cities...
The fact that air is a lifting gas means that large, long term settlements are theoretically possible, with all the advantages regarding radiation and gravity listed above. Even the sulfuric acid is not that big a problem as it is mostly below the altitudes proposed, where it is quite dilute. In fact, the temperatures while hotter than Death Valley are such that one could could probably do something one can do nowhere except Earth: step outside in a birthday suit and survive as long as one could hold one's breath (but run to the cold shower/eyewash station afterwards!). As an added bonus, unlike anywhere except Titan, due to the sheer density of the CO2, such cloud cities would also be far better protected against meteor strikes than any city on Earth.
A 2015 study at Rutgers (preliminary draft here) published the above artwork some time ago to illustrate what a (very hypothetical) more permanent research station might look like and news reports on Monday's announcement almost universally featured the below N.A.S.A. image of a large floating outpost acting as a tender to several H.A.V.O.C. type airships.
Both of these are very ambitious indeed and probably quite far term. For one thing, despite its advantages, Venus would seem to make little sense as a location for space cities, as they'd be far down a gravity well, there's no water except what one can crack from the sulphuric acid and no easy way to bring in supplies from asteroids. In an O'Neal cylinder or on the surface of a planet like Mars a major damage incident is survivable with space suits and repair teams, on Venus if you balloon deflates you're baked, dissolved, and crushed.
So unless the view of the clouds is SPECTACULAR and sufficiently so to somehow justify interplanetary tourism, there's little reason to believe that there would ever be any kind of permanent outpost on Venus.
I mean what could Venus produce that has real value and couldn't be gotten FAR easier somewhere, indeed anywhere else?
One of our Crack Team Of 2-D Science Babes reminds us of this paper (PDF) we perused recently that reviewed what scientists know about Venus's atmosphere. Here's an interesting excerpt...
Venera 13, Venera 14, Vega 1, and Vega 2 descent probes all carried X-ray fluorescence instruments. These instruments measured elemental composition of the cloud particles and found not only sulfur, but also phosphorus, chlorine and iron – notably, as much phosphorus as sulphur in the lower clouds below 52 km [Andreichikov et al, Sov. Astron. Lett. 1986, 1987]. A chemical analysis by Krasnopolsky [PSS, 1985] con- cluded that the phosphorus could be in the form of phosphoric acid (H3PO4) aerosols, which would ac- count for the particulates observed by descent probes down to 33 km altitudes
Phosphorus is absolutely vital to life and while theoretically common on earth is concentrated in useable forms mainly in living organisms and in phosphate rocks (mostly fossils of dead organisms). The amount of free phosphorous pretty much dictates the carrying capacity of the planet and it is a real concern for food production as phosphates are a finite resource. Furthermore, additional sources of phosphorus need to be found if humanity is going to expand into space. such deposits are presumed to exist, but on Earth they seem to have been concentrated by biological action leaving a bit of a chicken-egg problem finding it off planet. Even without off planet colonization phosphorous shortages represent a potential disaster for human food supplies. There is discussion of peak phosphorus here, here and here.
Even if the perils of peak phosphorus are overstated, it IS a finite resource and most off planet settlements are going to require off planet sources of phosphorus if they are to expand. Phosphorus could well end up being something akin to the dilithium, quanticum 40,or spice Melange of the real future. The only extraterrestrial places that I've read that it exists in other than trace amounts is the above mentioned cloud layer on Venus and the red clouds of Jupiter (bound in phosphene).
This moves the notion of a floating city on Venus from technically feasible to potentially practical and indeed desirable. See, if the Soviet probes were correct, then there is, in Venus's lower atmosphere, phosphorus (in gaseous form) in greater concentrations than the ubiquitous sulfur. You'd need to pump up atmosphere near the surface, filter out the undesirable stuff and if its phosphoric acid then you have to take out the water and oxygen (I'm sure uses can be found for those) I don't know what reagents might be necessary but this represents a steady supply of phosphorous.
But wait...there's more. Venus has more sunlight than earth, a zillion times as much CO2, and about 4 times as much atmospheric nitrogen as Earth. There's also water to be had from the phosphoric and sulphuric acid. And remember you're better protected from meteor strikes and cosmic rays than on Earth. A Venusian phosphorus-gas mine could grow all its own food.
Art from Technica Molodezhi TM - 9 1971 a Soviet Science Magazine
In the longer term, expanding upon such floating farms, Venus could be the breadbasket of the solar system. All that stuff that can be got so much easier on Luna, Mercury, Mars or The Belt? Well, the cloud cities of Venus ought to be able to just buy them. Of course you have solar power out the wazoo so it's at least conceivable that such an outpost might make something useful out of the carbon in the CO2. Note too that the referenced report also mentions the apparent presence of gaseous iron compounds in the lower atmosphere which might be industrially exploitable as well. Finally, Venus has, as mentioned, well more that three Earths worth of nitrogen in its atmosphere. If Venus sold Mars an atmosphere, there'd still be enough left over for thousands of O'Neal Cylinders. Venus has the potential to be not only self-sufficient but an exporter of food, fertilizer and air.
Of course for any of that that to eventually come to pass we need to confirm the Soviet probe data and do close surveys of the planet. N.A.S.A. seems to be planning just that in the next decade.
This is awesome. Even putting aside the longer term speculations; the fact that N.A.S.A. is looking at innovative missions like this is truly heartening.
With regard to the more ambitious proposals, I think we should begin a movement to have high pressure gaseous phosphoric acid referred to by the trade name "Tibanna".
:While trying to hunt down a picture credit I discovered that there is an extensive disquisition on the topic of Venusian settlement and even terraforming from 2014 here.
:Thanks to Pete Zaitcev in the comments there are some links to much earlier thoughts by John Goff on the matter regarding safe rocket recovery here and here as well as Venusian industrial chemistry here and here.
Crackerjack 2-D Science Babe is Rikka from Haganai
Enough floating cities and floating Solar arrays, and you'd end up with a planet-wide solar screen, which might well induce an ice age. Easier to mine ice than air I'd think. Condense the thicker parts of the atmosphere into glaciers Bob's-yer-uncle.
Posted by: jabrwok at Wed Oct 17 11:51:03 2018 (BlRin)
Mercury, at the poles is surprisingly amenable, there seems to be a lot of ice in the shadows there.
Outside the ices though, there are NO volitiles and it has Mars gravity. OTOH, even away from the poles it's ok to go exploring during the very long night. | 0.9027 | 3.422175 |
The Gravity Assist Podcast is hosted by NASA’s Chief Scientist, Jim Green, who each week talks to some of the greatest planetary scientists on the planet, giving a guided tour through the Solar System and beyond in the process. This week, he’s joined by Alex Young, a solar scientist from NASA’s Goddard Space Flight Center, to discuss the mechanisms behind the Sun’s violent outbursts.
You can listen to the full podcast here, or read the abridged transcript below. [Stunning NASA Image Lets You Watch the Sun Explode in Real Time]
Jim Green: What do we mean when we use the term, ‘space weather’?
Alex Young: Well, space weather is this environment in the Solar System that’s created by the Sun and the energy and matter that it puts out, and how that interacts with all the bodies in the Solar System. [There is] this sort of somewhat steady wind that’s coming off the Sun, we call it the solar wind, and that’s the Sun’s hot atmosphere that is streaming out into space. It carries away the Sun’s magnetic field and sometimes we even get these explosions, and they’re huge — almost like tsunamis – that ride on top of the solar wind, and these are the more energetic phenomena that make up space weather.
Alex Young: Right. The Sun has a very strong magnetic field and that magnetic field gets twisted up inside of it, much like rubber bands get twisted; they have tension, they have pressure, [and] sometimes they get twisted enough and they snap violently, releasing energy [in the form of] a flash of light that we call a solar flare. And sometimes they spit out these huge blobs of material. Those are called coronal mass ejections (CMEs), and both [flares and coronal mass ejections] can create shock waves that excite particles to [high] speeds and so we get this storm of energetic particles.
Jim Green: Those particles can affect instruments on our spacecraft, ands also have implications for human exploration not only on the [International Space] Station but for when we go beyond low-Earth orbit too.
Alex Young: Exactly, and they are creating this very, very dynamic but hazardous and hostile environment [not only] for humans out in space, but [also for] all our technology, because all this stuff is electromagnetic and interacts with technology, which is electric in nature.
Jim Green: Alex, what’s the worst solar flare you’ve ever seen from the missions you’ve been involved in?
Alex Young: Well, the biggest one that I know of — and it actually happens to be the biggest one that was ever been recorded in the Space Age — happened during a time period of about two weeks. [During a period between] the end of October to the beginning of November 2003 [there were the] Halloween storms, and one of those flares that occurred just as the flaring region was rotating out of view on 4th November created what we call an X-class flare, and this one was off the charts. It was bigger than anything we’d ever seen, and in fact our instruments couldn’t even record it, so we had to estimate how big it really was.
Jim Green: When these flares take off and they start accelerating particles does that happen in all directions, or is it very directional?
Alex Young: The light from flares is not directional, it’s pretty isotropic. So if you see it anywhere that region is visible on the Sun. But the particles, those are very directional. They are created by jets and those particles are actually slamming into the Sun, creating the light, [and] then streaming out into space.
Jim Green: What’s the worst CME you’ve ever seen?
Alex Young: Well the worst CME I’ve ever seen also happens to be the biggest we’ve seen in the Space Age. In July 2012 there was an event that actually happened on the side of the Sun. It was caught by one of our spacecraft, STEREO, which [is actually two spacecraft] orbiting the Sun, and we measured this CME moving at a phenomenal 3,500 kilometers per second. It’s the biggest, fasted one we’ve ever recorded.
Jim Green: So these are bubbles of reconnected magnetic field and in those bubbles are all the atmosphere that the bubbles capture, and they just sort of lift off and fly at us?
Alex Young: Exactly. And the crazy thing is that they’re really huge — they start off bigger than Earth in size and they quickly expand as they’re moving away from the Sun, and very quickly they can then fill huge portions of the inner Solar System. And they’re carrying billions of tons of material as well as the magnetic field of the Sun inside of them.
Jim Green: Now a CME may or may not hit the Earth, but when they do, we’re in for a beautiful dazzling display of auroral lights.
Alex Young: And it’s amazing. But there’s so much more that happens when all of that stuff is interacting with Earth’s magnetic field and the tear-shaped bubble around the Earth we call the magnetosphere.
Jim Green: Have we seen everything the Sun can put out in terms of space weather?
Alex Young: Most definitely not. We have not seen even a blink of an eye of the life of the Sun. When the Sun was younger it was far more active, and we’ve really only seen a little bit [of that]. We know, by looking at historical records of aurorae that there [have been] huge storms. But we also see signatures in radioactive elements — carbon-12, beryllium-10. These are left by nuclear reactions in the atmosphere with particles [from the Sun] and we can see these traces in things like ice cores and tree rings, so we know there have been much bigger events in the past.
Jim Green: What are some of the big historic solar storms that we’ve been studying?
Alex Young: There have been a few in the modern age. There’s one that I talked about, the Halloween storms, [which were a] whole series [of events] during October/November 2003. A very famous one, in March 1989, caused a power outage in Quebec in Canada. But the big one that most people refer to is what’s called the Carrington Event. That was seen by Richard Carrington in England in September 1859. There were a series of events and he saw the first white-light flare, [which is] a solar flare visible in white light with a telescope, and then a few days later, they observed aurorae here on Earth. That’s the first time they made the connection between these magnetic eruptions on the Sun, the flare, and something occurring here on Earth.
Jim Green: Carrington saw the flare and then a coronal mass ejection lifted off. Seventeen hours later, there was the aurora. Now coronal mass ejections typically take 80 hours to reach here from the Sun, and so this thing was really moving. It had an enormous amount of mass and then the aurora was observed cutting right through the United States, through Mexico, and down into Central America. So a pretty spectacular event.
Alex Young: t was a really cool event for a lot of reasons and we’ve seen similar things. Even with the July 2012 event, the speeds were comparable — about 17 hours for it to reach about the distance from the Sun to the Earth.
Jim Green: Now that one didn’t hit the Earth.
Alex Young: That one didn’t hit the Earth, it hit a spacecraft to the side of the Earth, STEREO. But that spacecraft was at about the same distance. [Anatomy of Sun Storms and Solar Flares (Infographic)]
Jim Green: Now, they [CMEs] come from really big sunspots.
Alex Young: We’re talking sunspots that are many times the size of the Earth. And these sunspots, the bigger they get, the more complex they get. We can see how much energy they have contained inside them, which gives an indication of what sort of activity might we see.
Jim Green: Are there other events like the Carrington Event even further back in the past?
Alex Young: There’s one that’s been talked about recently, called the Charlemagne Event because it’s estimated to be within a period of about 774 or 775AD, somewhere in that period during the time of Charlemagne, and it was recorded in carbon-14 in tree rings. This event was 10 to 20 times bigger than the Carrington Event. And that’s just massive.
Jim Green: What would happen to our technological infrastructure if an event like that occurred today?
Alex Young: It could be quite catastrophic. There have been studies by the National Academies that estimate that there would certainly be billions of dollars of damage, there are even estimates of up to trillions of dollars because it would have such a global impact on our technology infrastructure. We could see power outages across the globe and in interconnected power grids especially. There would also be impact to communications and we would possibly lose many satellites. We’re now in an age of technology that we didn’t have even in 2003, and certainly not in 1989. So we don’t really know what a massive or strong solar event would do to the infrastructure that we have today.
Jim Green: Now that we’re becoming more aware of how active the Sun could be, how can we protect our technology here on Earth?
Alex Young: There are a lot of things we can do. One is simply prediction; that is, trying to make some sort of estimate of when an event is going to occur. Now as you mentioned, CMEs take some time to get here. But for a solar flare, there’s not a lot you can do. Once you see it, it’s here. [In that case] you just have to be prepared and have a fast reaction time. Another thing that we can do, when we talk about the impact on the power grids, is that we can improve the power grids themselves, improve the infrastructure, and even when we know an event is coming, we can do simple things like turning the power grid off for a short amount of time. It’s just like if you knew there was a lightning storm coming to your house, the first thing you would do is unplug your stereo.
Jim Green: In fact, how it affects our power grids is really because of the aurora. The aurora has huge currents that are in the ionosphere, so as they pass overhead, they induce other currents in our power grid that aren’t usually there, and therefore they can overload the transformers, burn them out, and that’s what causes the massive power-outages.
Alex Young: Exactly, because these currents are looking for large conductors to travel through.
Jim Green: Do you think there’s a connection between space weather and its importance to the formation of life in our Solar System?
Alex Young: Absolutely! One of the things we know is the Sun has changed over time. It was much dimmer in the past, spinning much faster, but it was also much more active. We estimate the early Sun was producing many Carrington-like events on a daily basis. Also the spectrum of that Sun was different. [Back then] there was much more ultraviolet, much more X-rays, so all the planets were being bathed by huge amounts of radiation. This had an impact on how atmospheres themselves formed. This radiation is interacting with these atmospheres, changing how they evolve, and it could have had an impact on the energy source needed to spark life.
Jim Green: One of the things that I love to do when I talk to my colleagues is to try and understand how they got into this field. What were the events in their life that really got them excited about their science, gave them that gravity assist that propelled them forward to become the scientist they are today? So Alex, what’s your gravity assist?
Alex Young: Well, it’s a multi-part assist. It’s a couple of little pushes and then one giant push. When I was a young kid I saw the original Star Trek in syndication, and I was fascinated by this idea of exploring space and especially the character of Mr. Spock, so I thought this would be so cool to be able to do that. Then around the same time I saw a show by Carl Sagan called Cosmos, [in which he took the viewer] around the Universe in a space ship. I started to see, hey, I can actually do this. I can actually be an explorer like Mr. Spock, but I can do it in real life and study the Universe from here with telescopes and spacecraft. It was an exciting time because it was the early 1980s, so the Voyager results were coming out. I was writing to NASA and they were sending me pictures from Jupiter and Saturn. At the same time I was getting specs for the space shuttle, they were just beginning with the launch of that, so all this was happening as I slowly slipped into high school. And my dad was an art professor, and one of his colleagues was a physics professor, so they made a deal. The physics professor’s daughter wanted to study art. And I wanted to study physics. So they said, if we can swap and in the afternoons they go and meet with each other and learn. So I went and met with the physicist while his daughter studied with my dad, and I learned about physics. He helped me, I built a laser and went to the science fair and really got into all this. This sort of came together finally, and that was the piece that just shot me out. That was the really, really serious assist.
This story was provided by Astrobiology Magazine, a web-based publication sponsored by the NASA astrobiology program. This version of the story published on Space.com. Follow us on Twitter @Spacedotcom or on Facebook. | 0.846991 | 3.580043 |
World Geography / Universe and Solar System
There are many theories that are being proposed for the origin and evolution of solar system. The Universe comprises of large number of
heavenly bodies. The basic unit of the Universe is the star. All stars are grouped into Constellations and group of Constellations is Galaxy. Universe is made
up of 1 million galaxies. In every Galaxy, there are more than 1 billion stars.
Where are We in the Milky Way
Our galaxy is Milky Way. It has more than 1 billion stars. One such star is Sun. Sun has its own family named Solar System.
It has planets, dwarf planets, meteoroids, comets, dust and asteroids. 99.8% of mass of solar system is with Sun. 0.1% of mass of solar system is in
Jupiter. Remaining 0.1% of mass is stored with all other bodies. Earth is located here. In earth 71% is water and 29% is continent or land.
4-40 million species are living either on the land or the water on the earth. Homo sapiens is one such species.
Formation of the Solar System Theories
- There are large number of theories available regarding the origin of Solar system. It is said that 4.5-5 billion years back, earth and the solar system
came into existence. Some contemporary studies also say that it got originated around 9–11 billion years back.
- All the theories can be classified into two categories of theories, (i) Catastrophic Theories, according to which the origin of the Earth is a Celestial or
Cosmic accident (not accepted now) and (ii) Evolutionary Theories, according to which the Earth got evolved through process of evolution (accepted nowadays).
- Jean and Jeffreys Tidal Hypothesis (Hit and Run Hypothesis) - According to this theory, Sun was approached by another star, because of which huge
amount of mass came out from Sun due to gravitational pull and formed planets.
- Supernova Hypothesis of Hoyle - Hoyle in his supernova concept postulates that there existed the primitive Sun and a companion star of giant size.
The companion star experienced nuclear explosion to become a Nova. When the explosion is intensely high, the bursting star is called Supernova.
explosion led to emission of large amounts of gaseous matter. The intense heat and atomic reactions are responsible for the formation of heavier elements like
helium, oxygen, carbon, nitrogen, etc. The heavier elements thus formed, are the source material for the formation of the earth.
- Russell and Lyttleton's Binary Star Hypothesis - The Binary hypothesis believes that many stars exist as pairs in the universe. Our solar system was
also having the Sun and other smaller star. Another bigger star approached the companion star and matter came out of companion star which became the source for
our earth contents.
- Interstellar Hypothesis - Otto Schmidt proposed that interstellar dust around the Sun got turned into planets.
- Kant and Laplace's Nebular Hypothesis - According to this theory, the original mass of the Solar system was in the form of Nebula (hot
rotating gaseous mass in the form of series of rings). Gradually the rings got separated, the gaseous matter cooled down and coalesced and turned into planets
and central portion was turned into the Sun. This is the most accepted theory. Other theories also support the Nebular theory.
- Big Bang Theory - According to this theory, all the matter of the Universe was at one place (super celestial body). There was an explosion
and the matter got disintegrated and the matter came out to form to planets and stars. According to Rig Veda, Adi Purusha is the super celestial body. | 0.881016 | 3.031576 |
After months of back and forth, scientists now agree that NASA's Voyager 1 has become the first manmade object to leave the solar system. And it only took 36 years to make the 12 billion mile-long journey.
It's obviously a major milestone for space exploration which is probably why scientists have been arguing for months over whether or not Voyager 1 had crossed the threshold into interstellar space. In the end, it all came down to the plasma surrounding the spacecraft. After a burst of solar wind and magnetic fields caused the plasma around the spacecraft to oscillate in April, researchers realized plasma was also 40 times denser at that point than it was in the heliosphere. This was a sign that the Voyager 1 had entered interstellar space, and the team ultimately determined that the spacecraft crossed the line in August 12 of last year. (Listen to the sound of interstellar space below.)
"Voyager has boldly gone where no probe has gone before, marking one of the most significant technological achievements in the annals of the history of science, and adding a new chapter in human scientific dreams and endeavors," said NASA’s associate administrator for science John Grunsfeld. "Perhaps some future deep space explorers will catch up with Voyager, our first interstellar envoy, and reflect on how this intrepid spacecraft helped enable their journey."
In the meantime, all eyes are on Voyager 2, which is nipping at its sibling's heels, speeding fast into interstellar space. (That is, if 2 billion miles can be considered nipping at its heels.) Either way, Voyager is now on its way to another star. At it's current speed of 100,000 miles per hour, it'll only take her 40,000 years.
What interstellar space sounds like:
How scientists decided Voyager had entered interstellar space: | 0.827111 | 3.009598 |
Astronomers Discovered Jupiter-like Clouds On The Nearest Brown Dwarf
In a first, astronomers have used polarimetry technique to study exoclouds — atmospheric clouds outside of our solar system. According to the article on HubbleSite, the team found that the closest brown dwarf to the Earth, Luhman 16A features cloud bands that are similar to the ones found on the gas giants in our solar system.
Brown dwarfs are sub-stellar objects that failed to sustain hydrogen fusion in the process of becoming a star, warranting the moniker of ‘failed stars’. Luhman 16 is a binary brown dwarf system located 6.5 light-years away from Earth. Both objects in the system, Luhman 16A and Luhman16B, are similar to each other in terms of masses and temperature, but have noticeably different weather.
Today’s weather forecast: partly cloudy with a high of 1,900 degrees F and ammonia rain . Not on Earth, clearly, but on the brown dwarf Luhman 16A. Astronomers have found evidence that Luhman 16A has Jupiter-like cloud bands: https://t.co/CAaFZpaPY5 pic.twitter.com/GUBMqAZIxT— HubbleTelescope (@HubbleTelescope) May 5, 2020
Researcher Julien Girard from Space Telescope Science Institute compared the extent of similarities to twin objects in our solar system, Earth and Venus explaining, that on the later, “It can rain things like silicates or ammonia. It’s pretty awful weather, actually.”
On Luhman 16A, the cloud bands are similar to that of Jupiter and Saturn. On the other hand, Luhman 16B shows no sign of stationary cloud bands. Instead, it exhibits evidence of more irregular, patchy clouds. This causes noticeable variations in the brightness of 16B.
Researchers used data from the NAOS-CONICA(NaCo) instrument at the Very Large Telescope facility in Chile to study the polarized light from the Luhman 16 system. Polarization is a property that dictates the direction of oscillation in transverse waves like light. So, instruments that polarize light, like Polarized sunglasses can block oscillation in one direction which translates to reduced glare and improved contrast.
But instead, researchers used NaCo to measure the oscillations of light waves from Luhman 16 system in different directions to determine what it encountered along its path and compared it to various models. Another researcher from the team, Theodora Karalidi of the University of Central Florida stated that in comparison, they found "that only models of atmospheres with cloud bands could match our observations of Luhman 16A."
Image Source: HubbleSite
Image Credit: Caltech/R. Hurt (IPAC) | 0.819693 | 3.645287 |
The Most Frightening Places in the Solar System | Universe
Solar System | The highest, the deepest, the hottest, the weirdest: our solar system is a place of extremes. In new work, “The Most Extreme 50 Places in the Solar System”, researchers David Baker and Todd Ratcliff are taking their readers into a sensational cosmic tour of gaseous giants, frozen months and incandescent planets. Here is a sample of the most spectacular places that eclipses any terrestrial recordings.
The most bizarre rotation movement
Saturn Moon Hyperion is an irregular shape, measuring about 408 x 260 x 220 kilometres in diameter, along with its three axes. As satellites with such dimensions of the planets generally possess enough gravitational force to obtain the spherical shape, astronomers suggest that Hyperion could be the fragment of a larger month, shattered by a devastating impact. The unusual form of the astral body explains why this is, according to Baker and Ratcliff, “total chaos”.
Most of the big months are “tangled,” meaning the same face of the natural satellite is always geared towards the planet that governs it. Is the case of the “relationship” between Earth and the Moon. But Hyperion’s strange form prevents such a link because the gravitational forces of Saturn and the Titan moon are unequally exerted on him. The result is an unplayable rotation. Days are never the same on Hyperion. Not only does the rotation rate vary radically, but even the northern pole of this month consistently points to a different direction in space, making it even impossible for the most skilled astronomers to predict Hyperion’s axis of rotation over 300 days from now.
The deepest ocean in the Solar System
Here, on Earth, we are impressed by the Marian Pit in the Pacific Ocean, whose depth, the absolute record, is about 11,000 meters below sea level. But Europe’s ocean of Jupiter makes this record pale. Although Europe is covered with a thick layer of ice, the measurements made by NASA’s Galileo spacecraft, as well as other probes, convincingly suggest the presence of a liquid ocean beneath that surface. And some of these measurements estimate the depth of the ocean at 100 kilometres.
The interior of the ocean would have been warmed, I think, by the tides produced in Europe by Jupiter and several other larger satellites of the planet, as well as radioactivity. The giant ocean of Europe is one of the most promising places to search and research alien life. NASA and the European Space Agency are currently working on a joint mission that could be launched in 2020 and whose purpose is the detailed examination of Jupiter and his moons Europe and Ganymede. A major goal is to determine the thickness of Europe’s ice layer, which has implications for the moon’s potential to sustain life.
The most pestilential place
Io, the Jupiter moon is fascinating from a certain perspective of planetary science – it is the most volcanic astral body active in our solar system, and its surface is sprinkled by volcanic craters. But visiting Io would not be really desirable. Baker and Ratcliff write that “the moon of Jupiter Io smells like a giant rotting egg”. The miasma is due to the hydrogen sulphide on the surface and the atmosphere of Io, the distinctive yellow and red colours of the moon coming from sulphur compounds. Volcanic eruptions are common on Io and are constantly restoring the atmospheric sulphur reserve.
The moon is very active because it revolves around Jupiter on a vague elliptical orbit. As it dances repeatedly, when closer to the giant planet, Jupiter’s gravity produces tidal phenomena inside the natural satellite that warms its mantle and causes violent explosions. In 2007, NASA’s New Horizons flew near Io and noticed a sulphurous volcanic eruption that expanded to an altitude of nearly 300 kilometres above the ground.
in comparison, the largest volcanic eruptions reach up to a height of about 20 thousand meters.
The toughest (and precious) rain of Solar System
The giant frozen planet Uranus and Neptune differ from the giant giants Jupiter and Saturn by composition; they contain especially “ice” made up of water, ammonia and methane. In the Neptune and Uranus shells, the elevated temperatures probably fragment the methane into its component parts, hydrogen and carbon. Astronomers believe that intense pressure could force such released carbon so forcefully that it turns into crystalline networks or diamonds.
As explained by Baker and Ratcliff, diamond stones, small or large grains of salt, such as rocks could cross a liquid and sprinkle rain jacket solid core. This core could be covered with a thick layer of diamonds, more massive than any Earth mine. So far, the Uranus and Neptune outer diamond rains are hypothetical, however, and astronomers need more data to accurately determine whether or not this strange phenomenon occurs. unfortunately, no spacecraft is currently scheduled to explore these worlds.
The largest canyon
Is enough to imagine a canyon whose crap stretches over a distance of about 4,000 kilometres, that is to say, from Bucharest, Romania, to Delhi, India, to make us an image as close as possible to the appearance and size of theValles canyon Marineris on Mars. The huge hole was first observed by NASA’s Mariner 9 in 1972 and was later baptized in honour of it. The Martian crater splits four million meters of “red” land, reaching maximum depths of up to ten thousand meters. In comparison, the Great Canyon of the Colorado River in the United States has an “only” length of 446 kilometres and an absolute depth of about one mile, or 1.6 kilometres. It is assumed that the Valles Marineris is a sloping and sloping valley when the molten rock from Mars’ mantle expanded and forced the boundaries of the planetary crust.
The highest mountain
Mars is provided not only with the deepest valley of the Solar System but also with the highest mountain massif. The Martian volcano Olimp Mons reaches an altitude of about 25,000 meters, that is, more than three times higher than Mount Everest, the highest massive on Earth. The liquid piscine was probably formed like earthly volcanoes: being above a “hot spot”, from which the hot rock waves rose from the interior of the planet to the surface.
But this mountain could grow higher than any other volcano because Mars has no tectonic plates, explains Bake and Ratcliff in their book. On Terra, the tectonic plates “migrate” above the mantle eruption points, the two researchers write. “The volcanoes are formed, they are extinguished, and others are formed as the tectonic plates move over the hot spots, thus producing a long volcanic chain”. As on Mars, there are no moving plaques, Olimp Mons may have been over a volcano eruption for a very long time, which has led to an uninterrupted development.
The most powerful power discharges
When NASA Cassini was on its way to Saturn in the late 1990s, it swung over Earth to fall under its gravitational attraction to change its speed and trajectory. From a distance of 88,000 kilometres above Terra, the probe detected radio wave rays representing the terrestrial lightning signal (a lightning beam emits electromagnetic radiation with a variety of wavelengths, including visible light and radio waves).
As Cassini continued his trip to Saturn in the early 2000s, the mission’s coordinators had a shock. From a distance of 160 million kilometres away, the probe detected radio pulses indicating strong electric storms on Saturn. the radio signal was about a million times stronger than the one detected on Earth. For years, Saturn superheroes could not be seen directly, but radio eruptions indicated that they occurred in a region called the “Storm Alley” in the southern hemisphere of the planet. Finally, this spring, Cassini captured the first images of lightning on Saturn.
The most powerful magnet
The beautiful image shows our magnetically sunny sun, ornate with glowing rays, crowns and waves of plasma. electrically charged plasma from the outer layers of the Sun creates turbulent bubbles of the state of Texas, generating local magnetic fields. These magnetic field structures are often highlighted by shimmering plasma as the charged particles fly along the magnetic field lines. For this reason, the shimmering filaments give out the sunspot, regions where the plasma is held captive by intense magnetic and cold fields. where magnetic field lines intersect, they can release stunning energy rains, known as “solar flares,” and even more powerful explosions called coronary mass decompensation (CME). a single CME can break into space, at huge speeds, up to 10% of the solar crown (the Sun’s outer atmosphere).
The most destructive global warming
Our sister planet, Venus, has almost the same size, the same density and the same composition as the Earth, and when its dense atmosphere was discovered, the alien’s wonders wondered if this planet was inhabiting the lush jungle and exotic life. In fact, Venus is an incredibly hot world, governed by abundant clouds of sulfuric acid. Venus is 40 million kilometres closer to the Sun than Terra, but this is not the only reason the planet is so hot.
Venus was “ripe” by the global warming phenomenon. Under normal conditions, the solar radiation reaches the surface of the planet, and the latter releases some of that energy in the form of infrared radiation. But on Venus, the greenhouse effect created by thick clouds and a dense atmosphere composed mainly of carbon dioxide capture the heat and prevent its leakage into space. the surface temperature of this planet is 460 degrees Celsius, making it the hottest planetary surface in our solar system.
The longest storm
It is a storm that does not give signs that it will stop too soon. The great red dot ofJupiterwas first seen by Italian astronomer Giovanni Cassini in 1665; while observations were sporadic in the later centuries, 18 and 19, many astronomers believe today that the storm has wrecked Jupiter’s land for 345 years since its first documentation. The huge storm is the size of three Earths, and its winds reach speeds of up to 650 km/h. How have you been active for centuries?
Baker and Ratcliff explain how the storm energy comes from inside the planet Jupiter and from smaller whirls from the surface. “Remarkably, Jupiter’s interior provides 70% more energy to the higher ceiling than clouds than the planet from the Sun”, the authors write. “Like a giant air compressor, gravitational contraction generates intense heat and heat inside the planet. Strong electric storms in the Jupiter atmosphere channel a good deal of this heat to the upper portion of the clouds.” Smaller storms are devoured by the Great Red Spot, which allows it to manifest itself further.
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The Magic of Crystals
Free eBook Crystals provide energy, helping the body to the cellular level and the mind reaching the area of suggestion,maintaining health or even recovering. Get the eBook and find out everything about crystals.
You're Amazing! The eBook is on it's way to your inbox. Enjoy! | 0.889016 | 3.623919 |
Scientists observe superconductivity in meteorites
Scientists at UC San Diego and Brookhaven Laboratory in New York went searching for superconducting materials where researchers have had little luck before. Setting their sights on a diverse population of meteorites, they investigated the 15 pieces of comets and asteroids to find "Mundrabilla" and "GRA 95205"—two meteorites with superconductive grains.
While meteorites—due to their extreme origins in space—present researchers with a wide variety of material phases from the oldest states of the solar system, they also present detection challenges because of the potentially minute measurability of the phases. The research team overcame this challenge using an ultrasensitive measurement technique called magnetic field modulated microwave spectroscopy (MFMMS). Details of their work are published in Proceedings of the National Academy of Sciences (PNAS).
In their paper, UC San Diego researchers Mark Thiemens, Ivan Schuller and James Wampler, along with Brookhaven Lab's Shaobo Cheng and Yimei Zhu, characterize the meteorites' phases as alloys of lead, tin and indium (the softest non-alkali metal). They say their findings could impact the understanding of several astronomical environments, noting that superconducting particles in cold environments could affect planet formation, shape and origin of magnetic fields, dynamo effects, motion of charged particles and more.
"Naturally occurring superconductive materials are unusual, but they are particularly significant because these materials could be superconducting in extraterrestrial environments," said Wampler, a postdoctoral researcher in the Schuller Nanoscience Group and the paper's first author.
Schuller, a distinguished professor in the Department of Physics with expertise in superconductivity and neuromorphic computing, guided the methodological techniques of the study. After mitigating the detection challenge with MFMMS, the researchers subdivided and measured individual samples, enabling them to isolate the grains containing the largest superconductivity fraction. Next, the team characterized the grains with a series of scientific techniques including vibrating sample magnetometry (VSM), energy dispersive X-ray spectroscopy (EDX) and numerical methods.
"These measurements and analysis identified the likely phases as alloys of lead, indium and tin," said Wampler.
According to Thiemens, a distinguished professor of chemistry and biochemistry, meteorites with extreme formation conditions are ideal for observing exotic chemical species, such as superconductors—materials that conduct electricity or transport electrons without resistance. He noted, however, the uniqueness of superconductive materials occurring in these extraterrestrial [minor] planets.
"My part of the project was to determine which of the tens of thousands of meteorites of many classes was a good candidate and to discuss the relevance for planetary processes; one from the iron nickel core of a planet, the other from the more surficial part that has been heavily bombarded and was among the first meteorites where diamonds were observed," said Thiemens.
According to the cosmological chemist, who has a meteorite named after him—Asteroid 7004Markthiemens—Mundrabilla is an iron-sulfide-rich meteorite from a class formed after melting in asteroidal cores and cooling very slowly. GRA 95205, on the other hand, is a ureilite meteorite—a rare stony-like piece with unique mineral makeup—that underwent heavy shocks during its formation.
According to Schuller, superconductivity in natural samples is extremely unusual.
"Naturally collected materials are not phase-pure materials. Even the simplest superconducting mineral, lead, is only rarely found in its native form," Schuller explained.
The researchers agreed that they knew of only one prior report of natural superconductivity, in the mineral covellite; however, because the superconducting phases they report in the PNAS article exists in two such dissimilar meteorites, it likely exists in other meteorites. | 0.878 | 3.479258 |
In my last post, I detailed some of the hottest locations for astrobiology in our Solar System. Today, however, we’re going to be going farther afield- outside the Solar System entirely, in fact.
The discovery of exoplanets – planets that orbit other stars- has been one of the great scientific success stories of the last century. In less than 20 years, we’ve gone from a handful of early detections to literally over a thousand (plus thousands more “candidates” that are awaiting verification). Obviously, astrobiologists have been more than a little excited by this pace of discovery.
Detecting an exoplanet is no mean feat- such bodies are usually a million times dimmer than their host star, and the light of the star tends to overwhelm such faint emissions. However, several techniques have been developed to get around these limitations.
The earliest used, Doppler spectroscopy,takes advantage of the fact as a planet orbits a star, it “tugs” on its center of mass, causing it to “wobble” ever so slightly. The motion due to this wobble can be detected by looking for the resulting Doppler shift in the star’s spectra. However, this method is generally most effective in determining extremely large planets that orbit close to their parents stars (so called “hot Jupiters”), which are unlikely to host life.
The most successful method used to date has been transit photometry, which looks for tiny dips in the star’s light output as the planet crosses in front of it. This method does have some limitations- the star, the planet, and Earth have to be precisely aligned for the transit dip to be visible- but it’s a relatively easy signal to look for otherwise. Transit photometry has been used by a number of different observing missions, the most famous example being the spectacular planet-hunting Kepler space telescope.
A few other planets have been detected using more esoteric methods, such as gravitational microlensing or timing pulsations in stars and pulsars. A scant handful have even been directly imaged, although this only feasible if the planet is extremely large, hot, and widely separated from its host star.
Using these methods, a whole zoo of exoplanets has been detected. Most of them are likely to be uninhabitable- but let’s take a look at the ones that might be a bit more promising for seekers of extraterrestrial life.
One of the most Earth-like planets (at least in terms of mass and theoretical surface temperatures) yet discovered, Kepler-296e is 1.75 times the size of Earth. It orbits a red dwarf star 1089 light years away, which is part of a binary system. It is located within the habitable zone of the star, where the temperature is warm enough for water to be liquid on the surface. Kepler-296’s habitable zone is much closer than the Earth is to the sun, owing to the cooler temperature of the host star; the planet orbits its star in only 34 days.
Located 1,120 light years from Earth, Kepler-442b also orbits a cooler red dwarf star. It’s 2.34 times the size of Earth, and would have a surface gravity about 30% greater (definitely the planet to go to if you want to get a good workout).
Detected 1,200 light years from Earth in the Lyra constellation, Kepler-62e is a member of an older star system, being likely billions of years older than Earth. It is thought to have a rocky composition (like Earth’s), and computer modeling suggests the planet could be largely covered by oceans. It’s considered a strong enough candidate for habitability that it’s been targeted for observation by the SETI program.
Gliese 832 c
One of the closest potentially habitable planets detected, Gliese 832 c is a scant 16.1 lights away. It is thought to have an extremely elliptical orbit, as planets go- that is to say, the distance from its star varies considerably. Consequently, the surface temperature may swing from -40 degrees Celsius to 7 degrees Celsius, depending on where the planet is in its orbit; on average, however, the temperature is warm enough to allow liquid water. However, it is possible the planet may have developed a dense atmosphere, leaving it in an uninhabitably hot state similar to Venus. Further observation will be required to determine how friendly to life the planet really is.
Unlike the other entries in this list, KIC 8462852 isn’t a planet. In fact, we’re not entirely sure what it is. The star first became well-known when analysis of Kepler data detected a intermittent, massive drop in the amount of light produced by the star- equivalent to covering up over half the star’s visible surface- something that had never been observed before. Furthermore, no dust or debris cloud has been detected around the star.
Initially, it was thought that the dimming could be due a mass of comets pulled inwards by a passing star- and, indeed, there’s another star in the local area that could’ve done such a thing. However, an examination of historical images showed that KIC 8462852 has been dimming for the last century- far too long a timescale for the comet explanation.
Lacking any other explanation, some researchers have begun speculating that the dimming could be due to the construction of megastructures in orbit around the star- perhaps a swarm of solar power satellites to capture the maximum amount of the star’s energy (popularly referred to as a Dyson sphere or Dyson swarm).
Admittedly, there are some problems with the aliens-did-it hypothesis- the laws of thermodynamics dictate that such structures would generate a large and detectable quantity of waste heat, which has yet to be observed. Observing campaigns by SETI also haven’t turned up any signs of intelligent life. Nonetheless, the sheer weirdness of the system means it will likely be a target of investigation for the foreseeable future. Whatever’s going on out there, it’s not like anything we’ve seen before.
These are just a handful of the potential living worlds that might be found throughout our galaxy. Undoubtedly more will be detected by upcoming missions, such as the James Webb Space Telescope, PLATO, and Kepler’s successor TESS. Get your travel itineraries ready- because the list of possible cosmic vacation hotspots is only going to keep growing!
Tessa is a 28 year old PhD student, and perhaps the world’s only queer trans astrobiologist. A nerd going way back, her interests include science fiction, space exploration, sustainability, science communication, and feminism and gender. Her hobbies also include horseback riding, playing the flute, social dancing, knitting, and occasional attempts at writing fiction. She currently resides in Tempe, AZ with her even nerdier fiancee and a mastiff mix who thinks he’s a lapdog. She tweets occasionally @spacermase. | 0.929633 | 3.989946 |
This computer-generated image shows an artist's conception of a black hole. The event horizon is depicted as the black sphere in the middle of the picture. The surrounding disk of gas, represented by white and blue rings, whirls around the black hole at different speeds, with the material closest to the black hole approaching the speed of light.
Click on image for full size
Courtesy of NASA
Black Holes Out for a Spin
News story originally written on May 14, 2001
Everyone is awed by black holes.
How could there be a thing that devours all light and matter around it...so that matter can never escape?!?
A new discovery has been made about black holes - some of them spin! Dr. Tod Strohmayer, a scientist at NASA, used data from NASA's Rossi X-ray Timing Explorer to show that at least some black holes spin. "Almost every kind of object in space spins, such as planets,
stars, and galaxies," said Strohmayer. "With black holes, it's
much harder to directly see that they are spinning, because
they don't have a solid surface that you can watch spin
around. We can, however, see the light emitted from matter
plunging into the black hole. The matter whips frantically
around the black hole before it is lost forever."
The specific black hole that Strohmayer was studying was a stellar black hole. A stellar black hole is one formed from a star. When stars at least 10 times the mass of the Sun cannot support themselves any longer, the stars can explode off their outer shell in a supernova explosion. There is still a lot of material left that doesn't get thrown off into space. This material collapses into a single point of infinite density. This single point is the beginning of a stellar black hole.
Because the star that formed the black hole would have been spinning, it is thought that the spin of a black hole is caused by the angular momentum of the star that formed it.
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Astronomers at the Big Bear Solar Observatory have captured the most detailed, visible-light images of the Sun. In the image above, you can see the terrifying detail of a sunspot, where intense magnetic activity prevents the convective flow of superheated plasma. In the image below, the Sun’s photosphere (the surface region that emits light) shows off its “ultrafine magnetic loops.”
These images were captured by the New Solar Telescope, which is equipped with a 1.6-meter clear-aperture Gregorian telescope and the Visible Imaging Spectrometer (VIS). With a huge aperture and modern imaging sensor, the NST is the largest and best solar telescope on the planet — and indeed, it was built specifically by the New Jersey Institute of Technology (NJIT) to study the activity of the Sun. Scientific observations began in 2009, but it seems it took more than four years for the conditions to be just right to capture these photos.
In the image at the top of this story (view larger), you see the most detailed photo ever of a sunspot. The dark patch in the middle is the umbra, with the “petals” forming the penumbra. The texture around the outside is what most of the surface of the Sun looks like. Like most solar phenomena, we don’t know exactly what causes a sunspot, but it appears to be some function of the Sun’s intense magnetic fields and differential rotation (where internal regions of the Sun rotate at different speeds). Basically, something causes the magnetic field to collapse in on itself. This intense magnetic field is vertical (normal to the Sun’s surface), pointing straight down, blocking the Sun’s normal convection and in turn reducing the sunspot’s surface temperature. This is why sunspots appear darker — a sunspot might be just 2,700-4,200 degrees Celsius, while a normal patch of the Sun is around 5,500 C. The lighter, petal-like regions are where the magnetic field is more inclined, allowing for some convection to occur.
The second image, above, appears to just be a close-up of the Sun’s photosphere, captured by the Visible Image Spectrometer’s H-alpha filter (red light produced by energetic hydrogen atoms). The lines/loops of hydrogen plasma are created by magnetic fields that emanate from the Sun’s inner layers. Basically, it just gives us a better idea of just how crazy the surface of the Sun is. In the image below, captured by the TRACE space telescope as it orbited near the Sun, you can see what a sunspot looks like from another angle.
The New Solar Telescope, and space-based telescopes such as NASA’s STEREO, are of vital scientific importance because they give us more data about one of the most significant objects in the universe: the Sun. By learning more about sunspots, solar flares, and other heliophysical phenomena, we stand a better chance of weathering whatever the Sun throws at us and prospering here on Earth. | 0.820105 | 3.996105 |
After two years of operations, the NEOWISE space mission is consistently beating ground-based telescopes in its fraction of detected possibly dangerous asteroids to Earth.
While overall near-Earth NEOWISE asteroid discoveries are tiny — this NASA site says NEOWISE found 34 in its second year — 13 of those asteroids have orbits that bring them really close to Earth, putting them in the "potentially hazardous" category. As a fraction of discoveries, NEOWISE's haul of potentially hazardous asteroids exceeds ground-based surveys by a factor of three, a new paper says.
The paper (available on Arxiv and set to publish in the Astronomical Journal) was released just before its investigators find out if the successor mission to NEOWISE will be approved. Called NEOCam or Near-Earth Object Camera, the mission is one of five being considered for NASA's next round of lower-cost Discovery-class missions. A decision is expected in September, with the selected mission launching in 2021.
Meanwhile, NEOWISE is still going strong as it enters its third and likely final year of operations in Earth orbit, according to status updates on the website. In 2017 it is expected to enter an orbital zone too sunny for observations.
"As of mid-June 2016, NEOWISE has completed its fifth coverage of the entire sky and is beginning the sixth pass," the website says, adding that 541 near-Earth objects and 99 comets have been surveyed so far (among more than 20,000 solar system objects).
The investigators are now reprocessing the mission data to seek asteroids and comets at even fainter magnitudes. They're also cataloging the asteroid and comet properties they have to deliver to NASA's Planetary Data SystemPlanetary Data System.
NEOWISE comes from a base telescope has already endured a two-year hibernation and subsequent restart since the first mission, the Wide-field Infrared Survey Explorer (WISE), launched in 2009.
WISE scanned the sky in four infrared wavelengths until its coolant ran out in 2010. NEOWISE began as a four-month mission scanning the sky in 2011 using the two shortest wavelength detectors. NEOWISE went into hibernation in 2011, then was brought out again in 2013.
Among NEOWISE's major contributions to asteroid science is refining the size of many known asteroids. In its second year alone, 84% of the 207 near-Earth asteroids NEOWISE observed were missing precise diameters and albedos (brightness) until it did measurements.
"Using visible wavelengths of light, it is difficult to tell if an asteroid is big and dark, or bright and small, because both combinations reflect the same amount of light," Carrie Nugent, a NEOWISE scientist at the California Institute of Technology, explained in a 2015 NASA press release.
"But when you look at an asteroid in the infrared with NEOWISE, the amount of infrared light corresponds with how big the asteroid is, and with some thermal models on a computer, you can figure out how big the asteroids are."
The new paper summarizing NEOWISE's second year was led by Nugent and co-authored by NEOWISE principal investigator Amy Mainzer. Both were unavailable for interviews before this article's publication date due to work on a large project, they told Discovery News.
Originally published on Discovery News. | 0.839025 | 3.732038 |
A new computer model of our solar system’s movement relative to the Milky Way indicates that it “bounces” up and down through the plane of the galaxy; a cycle that scientists say is a “beautiful match” with the mass extinction events that occur periodically on Earth.
Writing in the Monthly Notices of the Royal Astronomical Society, the scientists at the Cardiff Centre for Astrobiology that built the computer model say that during certain periods in the bounce, gravitational forces from surrounding gas and dust clouds could dislodge comets from their paths. These comets could then plunge into our solar system, some of them colliding with the Earth.
Napier contends that the periods of comet bombardment also coincide with mass extinctions, such as that of the dinosaurs 65 million years ago. But while the bounce effect may have been bad news for dinosaurs, it may also have helped life to spread. The scientists suggest the impact may have thrown debris containing micro-organisms out into space and across the universe.
“This is a seminal paper which places the comet-life interaction on a firm basis, and shows a mechanism by which life can be dispersed on a galactic scale,” commented Centre director Professor Chandra Wickramasinghe. And in case you’re interested in when the next comet infestation might occur, our present position in the galaxy suggests we are now very close to another such period.
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Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2001 February 16
Explanation: In nearby galaxy NGC 6822, this glowing emission nebula complex surrounds bright, massive, newborn stars. A mere 4 million years young, these stars condensed from the galaxy's interstellar gas and dust clouds. The nebular glow is powered by the bright stars' intense ultraviolet radiation while its shape is sculpted by the interaction of stellar winds and radiation with the immense interstellar clouds themselves. Cataloged as Hubble-X, many skygazers find the appearance of this extragalactic star forming region reminiscent of the most famous stellar nursery in our own galaxy, the Orion Nebula. Hubble-X is intrinsically much brighter than Orion though, and at a distance of 1.6 million light-years it is about 1,000 times farther away. Hubble-X is also about 100 light-years across compared to 10 light-years for the Orion Nebula. Why is it called Hubble-X? X is the Roman numeral 10, this nebula's designation in a catalog of similar objects for galaxy NGC 6822.
Authors & editors:
Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/GSFC
& Michigan Tech. U. | 0.903674 | 3.125254 |
- To create a tactile version of the Moon using low cost household materials.
- To explore our moon through a tactile model.
Ask students to point at a feature on their diagram as soon as they know which one it is. First give a description and a couple of seconds to think about it. Then give the name and a couple more seconds to point it out. e.g. This is the main overall surface of the Moon, it is not smooth. These are called the seas of the Moon, although there was never water on the Moon. Instead this was caused by lava on the surface a long time ago. They are smooth and dark (the dark coloured Maria). This bowl shaped part or feature of the Moon is caused by rocks hitting the surface (Crater). These are the bumpy features on the Moon at a greater height (Mountains).
Evidently the Moon is not made of fabric and sequins. Ask students to discuss the importance of building models, strengths and limitations of this model of the Moon, and how they might improve the model. Ask students in their groups to write down two things they learned from the activity, and two things they want to learn more about.
The Moon is the only natural satellite of the Earth. It orbits our planet in 27.3 days at a mean distance of 384,400 km. Its diameter of 3,474 km makes it the fifth largest satellite in the solar system.
It is thought that the Moon was formed at the same time as the Earth, 4.55 billion years ago, from the debris of a giant collision between the Earth and a Mars-size object.
The Moon is in on a synchronous orbit around the Earth, which means that it makes one turn around itself as it makes one turn around the Earth. So, it is always showing the same face to us. All we know about the ‘hidden’ face of the Moon comes from the records taken by astronauts or automatic probes that went around on to the other side. There is no rising or setting of the Earth on the horizon of the Moon. If you were standing on the near side of the Moon, the Earth would appear immobile in the sky.
During its revolution around the Earth, the disk of the Moon is not always completely lit by the Sun. This variation in the appearance of the lunar disk is called the “phases of the Moon”, and is characterized by a well-known cycle.
The apparent diameter of the Moon as seen from Earth is almost exactly that of the Sun. This is why the Moon can sometimes completely mask the solar disk and produce total solar eclipses. Another important influence of the Moon on Earth is the phenomenon of tides, which is due to the Moon’s gravitational pull on the seas and oceans of Earth.
The Moon is the only celestial object that has been visited by human beings. The first visit was on 21 July 1969 when two members of the Apollo 11 mission set foot on our satellite: they were Neil Armstrong and Edwin Aldrin. As many as 12 astronauts walked the surface of the Moon between 1969 and 1972, and they returned with 382 kg of lunar soil to be analysed on Earth.
(while you explore the tactile schematic image)
The visible surface of the Moon shows bright and dark areas. The bright areas are generally hills or mountains (materialized by thick fabric on the tactile image), while the dark ones are flat lands, called “mare” (materialized by thin fabric in relief on the tactile image). These low altitude areas were filled with lava during an ancient period of volcanic activity, around 3 billion years ago. Most of them were named by ancient astronomers after common phenomena encountered on terrestrial seas and oceans: Oceanus Procellarum (‘Ocean of Storms’), Mare Imbrium (‘Sea of Rains’), Mare Serenitatis (‘Sea of Serenity’), Mare Tranquilitatis (‘Sea of Tranquility’), etc.
The whole face of the Moon is dotted with craters, with diameters from a few meters to hundreds of kilometres (curved sequins). They are the result of impacts by asteroids, since the Moon does not have any atmosphere to prevent them from reaching the surface (a few of them are materialized by buttons on the tactile image: Plato and Aristoteles at the top, Aristarchus on the left, Copernicus near the centre, and Clavius at the bottom). Copernicus has a diameter of 93 km and is located in Mare Imbrium at the end of a chain of mountains called Apennins (materialized by the thick fabric on top of the thin fabric on the tactile image).
Cut the outer round shape of the moon from one of the printed 'Moon Featureless PDF'.
Place it on top of the thick fabric and draw a circle.
Cut the same round shape on the thick fabric.
Apply glue on the surface of the moon on the other Moon Featureless PDF.
Place the circular fabric cutout on top of the glued area of the printed paper.
Using the Moon Features PDF, cut out the inner section which has several black dots on.
Place the inner section on top of the thin fabric and draw the outline of the shape.
Cut out the outlined shape.
Glue this piece of fabric on top of your fabric moon.
Cut a small piece of the thick fabric and glue it in place so it matches the dashed line on the Moon Features PDF.
Glue the thick fabric piece on top of the previously glued thin fabric.
Place glue on the flat section of the sequins and glue them on top of the fabric, in the same places as the small circles on the Moon Features PDF.
Wait for the image to dry before you start exploring.
There are several ways in which you can explore the scientific content of the tactile schematic images.
If you’re presenting the final tactile image to the students, first let them explore and feel the different textures. Questions will arise as the students explore; encourage them to write their questions down and share with the other groups. Read “Background Information” to understand the different features present in Earth’s schematic tactile image, and share with the students as they ask about them, or (if you have more time), prompt each group to choose a feature to learn more about and then have them present to the other groups in the class.
Discuss the idea of models with the students. Suggested discussion points:
Ask students in their groups to write down two things they learned from the activity, and two things they want to learn more about.
|UK||KS3||Chemistry||-||Earth and Atmosphere|
|UK||KS2: Year 5||Science||-||Earth and Space|
|UK||KS2||Art and Design||-|
Explore the rest of the planets through ‘Meet Our Neighbours’ in tactile form at http://nuclio.org/astroneighbours/resources/
Cheap tactile version of the moon is a great resource to explore lunar features for both visually impaired and normal vision students. | 0.844041 | 3.687902 |
Until about 150 years ago, most people thought rocks did not fall to earth from outer space. Only people who had witnessed it, or knew of it actually happening believed that rocks fell from the sky. Others thought such an idea was crazy. But science soon caught up with the stories, and rocks from space or meteorites became a reality.
Craters on the Moon and other planets were once, thought to be created by old volcanoes. This concept was thought to be the same for Earth too, but around the year 1900, it was proven otherwise at a place now called Meteor Crater in Arizona. Rocks, including large ones, do collide or fall to the Earth, the Moon and other planets such as Mars. Many believe that the dinosaurs were killed off by a large (6 miles in size) meteor collision with Earth. Large impact craters create new rocks called tektites, which are like volcanic glass, and impact melts called breccias, and fractured rocks called shattercones.
"Shooting Stars" were once thought to be stars falling from their place in the heavens, never to be seen again. But we now know that these shooting stars are actually meteors that pass through our atmosphere. The typical shooting star is a small spec of rock that burns up in our atmosphere from friction. If a bigger meteor fell you would definitely notice a difference in the brightness and size of the streak. A large meteor seen locally would brighten the sky in the daytime, and often creates a "sonic boom".
Meteorites are meteors that land on Earth. They are called a Fall if witnessed by people when they fall, or Finds when people find them and no one saw them come down in an area. A new or recent fall will typically have a dark, often black "fusion crust" on one or more sides which demonstrates the heat generated during its’ flight through our atmosphere. The rocks get cooked, and melt away. Crust colors can vary with different types of meteorites.
Most meteorites have a nickel-iron metal in them that is attracted to magnets. This attraction to magnets is called paramagnetism. Most achondrites have very little metal are not attracted to magnets or metal detectors.
Where do meteorites come from? The main source of meteorites is from the Asteroid Belt, which lies between Mars and Jupiter. This belt is full of orbiting asteroids that range in size from small particles to rocks up to 10 miles in length. These pieces are thought by some to be the parts of a planet that never came together. When asteroids collide with each other, they create new pieces that may fall out of orbit towards Earth, or to other planets or moons that eventually may grab them by gravity forces. They often hit a planet’s atmosphere moving at 10,000 to 20,000 MPH (WOW). Other sources of meteorites include the Moon, Mars, and comets.
Most meteorites are thought to be about 4.56 billion years old, which is slightly older than Earth. Planetoid meteorites including the Mars and the Moon are usually younger.
There are three main types of meteorites. Stone(93%), Iron(6%) and Stony-iron(1%). 86% of the total represent stones are estimated to be from the undifferentiated (unchanged or changed little) or chondrite (stone) category. About 7% of the total are differentiated (changed a lot) stones that are called Achondrites. A very small % are unique, one of a kind types that don’t easily fit into a distinct category. These estimates are based on the recorded falls, and the types that have fallen with them, and by number of finds.
Stone meteorites are split into two major categories: Chondrites (starts with a ‘k’ sound) and Achondrites, meaning rocks with or without chondrules, which are small rounded ball-like structures made only out in space. You will not find rocks made on planets , like Earth, that have chondrules in them. The details on how chondrules are made are still a mystery. Many ideas have been proposed, but we still don’t know for sure.
Most meteorites that are from the Asteroid Belt are Chondrule filled stony rocks with a little to a lot of metal inside. Others are the Iron (iron-nickel) rocks that are all metal, or a unique mixture of both kinds, the Stony-Irons. Achondrites do occur in the Belt, and are usually associated with larger planet-like differentiated pieces. Mars and Moon meteorites are also Achondrites, and they are obviously closer to us than the Asteroid Belt asteroids are.
Summary of Meteorite Types
There are about 15 different named types of Chondrites including:
H or high metal
L or low metal
LL or very low metal
Various C-meteorites for Carbonaceous (comets are thought to be in this class)
There are about 10 different types of Achondrites including:
Shergottites, Nakhlites, and Chassignite
Lunar (from the Moon)
Howardites (mixture of Eucrites and Diogenites)
There are two types of Stony-Iron meteorites:
There are three main types of Iron meteorites with many sub-categories
Facts and Fiction of Falls and Finds
Meteorite Falls can happen all over the earth. Most fall into the oceans that cover the majority of earth.
What we usually see as a falling star is just a small bit of rock that burns up in the atmosphere.
Fireball’s which can "light up the sky", day or night, are the meteors that will produce meteorites. They often start out a chunk as big as a car or so, only to break up and burn away to usually less than a hundred pounds for the total weight of meteorites found for a particular fall.
Witnessed falls are usually given the name of the nearest town or landmark. The same can be said for most finds.
Fresh fusion crust is probably the most obvious feature of a new fall. It does not take long for the effects of earth to start breaking down a meteorite.
Finds can also happen all over the earth. The majority however are found in the desert regions of the world, particularly north Africa and the middle east. Antarctica is also a rich location for meteorites finds. The reduced weathering effect in these regions is one of the reasons more are found. Wet or jungle like climates/terrain make finding falls and new finds difficult.
Iron meteorites are found more often (higher %) than they actually fall because they are more durable over time, and they look like what people think are meteorites.
They are not hot when they first land on earth. Maybe warm.
They are not radioactive, nor do they have healing powers.
They are hard to find and difficult to acquire or purchase????
To date, not one person has been reported killed by a meteorite. | 0.808663 | 3.632425 |
April 28, 2008
Paulette Campbell, The Johns Hopkins University Applied Physics Laboratory
240-228-6792 or 443-778-6792
The International Astronomical Union (IAU) has approved new names for features on Mercury and agreed on a new theme for fossae on the planet. These newly christened features were discovered from images taken by the MESSENGER spacecraft during its first flyby of Mercury in January.
The IAU is the internationally recognized authority for assigning designations to surface features on celestial bodies. "We are very pleased with how quickly the IAU has responded to the need to name many of the prominent landforms on Mercury first seen in MESSENGER images," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "The Science Team has just submitted our first scientific papers on the flyby observations, and this prompt action by the IAU has meant that we are able to refer to these features by their formal names."
Naming rules exist for most features on planets, moons, and asteroids. Mercury's cliffs are named after the ships of famous explorers. One set of cliffs discovered by MESSENGER (called by the Latin name for cliffs, rupes) is named Beagle Rupes, after the ship on which naturalist Charles Darwin sailed around the world.
Craters on Mercury are named after famous deceased artists, musicians, or authors. The approved crater names are:
MESSENGER discovered a striking set of graben (or fault-bounded troughs) that radiate out from a small area near the center of the Caloris basin. An individual graben is termed a fossa (plural is fossae) by the IAU. No previous fossae had been discovered on Mercury from the Mariner 10 images, so the IAU had to approve a new naming scheme—"significant works of architecture." Pantheon Fossae were named after the Pantheon, a still-used second-century Roman temple and later church. The ancient building and the fossae both feature a central circular feature and radiating texture.
Arizona State University's Mark Robinson, who leads the development of global image products from MESSENGER, says he drew on a database maintained by the IAU, as well as requests from individuals, for nomenclature ideas.
"There's a certain romance to these names," says Robinson. "But more practically, naming these features facilitates communication among scientists studying the planet. It's very cumbersome to write a scientific paper and say, ‘that big crater just east of that really huge crater near Mercury's north pole.' It's much easier to name the features."
An image of Mercury showing the locations of the newly named features is available online at http://messenger.jhuapl.edu/Explore/Graphics.html#photos.
During its first Mercury pass, MESSENGER's cameras imaged a large portion of Mercury's surface that had not been previously seen by spacecraft. (When Mariner 10, the only other space mission to visit Mercury, examined the surface 33 years ago, the Sun illuminated a different portion of the planet.) As the MESSENGER Science Team continues to study the images of Mercury, more features on Mercury will be named.
"The naming process is an ongoing effort because as we get more and more science out of the data we start finding more and more features," Robinson says.
MESSENGER will next fly past Mercury in October, viewing the opposite side of the planet. A third flyby is scheduled for September 2009, and the probe will settle into Mercury's orbit in March 2011.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The Johns Hopkins University Applied Physics Laboratory (APL) built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA. APL meets critical national challenges through the innovative application of science and technology. | 0.809343 | 3.613507 |
This article needs to be updated. The reason given is: The article appears to only cover projects up to 2016..June 2019)(
Solar sails (also called light sails or photon sails) are a method of spacecraft propulsion using radiation pressure exerted by sunlight on large mirrors. Based on the physics, a number of spaceflight missions to test solar propulsion and navigation have been proposed since the 1980s.
A useful analogy to solar sailing may be a sailing boat; the light exerting a force on the mirrors is akin to a sail being blown by the wind. High-energy laser beams could be used as an alternative light source to exert much greater force than would be possible using sunlight, a concept known as beam sailing. Solar sail craft offer the possibility of low-cost operations combined with long operating lifetimes. Since they have few moving parts and use no propellant, they can potentially be used numerous times for delivery of payloads.
Solar sails use a phenomenon that has a proven, measured effect on aerodynamics. Solar pressure affects all spacecraft, whether in interplanetary space or in orbit around a planet or small body. A typical spacecraft going to Mars, for example, will be displaced thousands of kilometers by solar pressure, so the effects must be accounted for in trajectory planning, which has been done since the time of the earliest interplanetary spacecraft of the 1960s. Solar pressure also affects the orientation of a spacecraft, a factor that must be included in spacecraft design.
The total force exerted on an 800 by 800 meter solar sail, for example, is about 5 newtons (1.1 lbf) at Earth's distance from the Sun, making it a low-thrust propulsion system, similar to spacecraft propelled by electric engines, but as it uses no propellant, that force is exerted almost constantly and the collective effect over time is great enough to be considered a potential manner of propelling spacecraft.
History of concept
Johannes Kepler observed that comet tails point away from the Sun and suggested that the Sun caused the effect. In a letter to Galileo in 1610, he wrote, "Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void." He might have had the comet tail phenomenon in mind when he wrote those words, although his publications on comet tails came several years later.
James Clerk Maxwell, in 1861–1864, published his theory of electromagnetic fields and radiation, which shows that light has momentum and thus can exert pressure on objects. Maxwell's equations provide the theoretical foundation for sailing with light pressure. So by 1864, the physics community and beyond knew sunlight carried momentum that would exert a pressure on objects.
Jules Verne, in From the Earth to the Moon, published in 1865, wrote "there will some day appear velocities far greater than these [of the planets and the projectile], of which light or electricity will probably be the mechanical agent ... we shall one day travel to the moon, the planets, and the stars." This is possibly the first published recognition that light could move ships through space.
Pyotr Lebedev was first to successfully demonstrate light pressure, which he did in 1899 with a torsional balance; Ernest Nichols and Gordon Hull conducted a similar independent experiment in 1901 using a Nichols radiometer.
Svante Arrhenius predicted in 1908 the possibility of solar radiation pressure distributing life spores across interstellar distances, providing one means to explain the concept of panspermia. He apparently was the first scientist to state that light could move objects between stars.
Konstantin Tsiolkovsky first proposed using the pressure of sunlight to propel spacecraft through space and suggested, "using tremendous mirrors of very thin sheets to utilize the pressure of sunlight to attain cosmic velocities".
Friedrich Zander (Tsander) published a technical paper in 1925 that included technical analysis of solar sailing. Zander wrote of "applying small forces" using "light pressure or transmission of light energy to distances by means of very thin mirrors".
JBS Haldane speculated in 1927 about the invention of tubular spaceships that would take humanity to space and how "wings of metallic foil of a square kilometre or more in area are spread out to catch the Sun's radiation pressure".
J. D. Bernal wrote in 1929, "A form of space sailing might be developed which used the repulsive effect of the Sun's rays instead of wind. A space vessel spreading its large, metallic wings, acres in extent, to the full, might be blown to the limit of Neptune's orbit. Then, to increase its speed, it would tack, close-hauled, down the gravitational field, spreading full sail again as it rushed past the Sun."
Solar radiation pressure
Many people believe that spacecraft using solar sails are pushed by the Solar winds just as sailboats and sailing ships are pushed by the winds across the waters on Earth. But Solar radiation exerts a pressure on the sail due to reflection and a small fraction that is absorbed.
- p = E/c
where p is the momentum, E is the energy (of the photon or flux), and c is the speed of light. Specifically the momentum of a photon depends on its wavelength p = h/λ
- perfect absorbance: F = 4.54 μN per square metre (4.54 μPa) in the direction of the incident beam (an inelastic collision)
- perfect reflectance: F = 9.08 μN per square metre (9.08 μPa) in the direction normal to surface (an elastic collision)
An ideal sail is flat and has 100% specular reflection. An actual sail will have an overall efficiency of about 90%, about 8.17 μN/m2, due to curvature (billow), wrinkles, absorbance, re-radiation from front and back, non-specular effects, and other factors.
The force on a sail and the actual acceleration of the craft vary by the inverse square of distance from the Sun (unless extremely close to the Sun), and by the square of the cosine of the angle between the sail force vector and the radial from the Sun, so
- F = F0 cos2 θ / R2 (ideal sail)
where R is distance from the Sun in AU. An actual square sail can be modeled as:
- F = F0 (0.349 + 0.662 cos 2θ − 0.011 cos 4θ) / R2
Note that the force and acceleration approach zero generally around θ = 60° rather than 90° as one might expect with an ideal sail.
If some of the energy is absorbed, the absorbed energy will heat the sail, which re-radiates that energy from the front and rear surfaces, depending on the emissivity of those two surfaces.
Solar wind, the flux of charged particles blown out from the Sun, exerts a nominal dynamic pressure of about 3 to 4 nPa, three orders of magnitude less than solar radiation pressure on a reflective sail.
Sail loading (areal density) is an important parameter, which is the total mass divided by the sail area, expressed in g/m2. It is represented by the Greek letter σ.
A sail craft has a characteristic acceleration, ac, which it would experience at 1 AU when facing the Sun. Note this value accounts for both the incident and reflected momentums. Using the value from above of 9.08 μN per square metre of radiation pressure at 1 AU, ac is related to areal density by:
- ac = 9.08(efficiency) / σ mm/s2
Assuming 90% efficiency, ac = 8.17 / σ mm/s2
The lightness number, λ, is the dimensionless ratio of maximum vehicle acceleration divided by the Sun's local gravity. Using the values at 1 AU:
- λ = ac / 5.93
The lightness number is also independent of distance from the Sun because both gravity and light pressure fall off as the inverse square of the distance from the Sun. Therefore, this number defines the types of orbit maneuvers that are possible for a given vessel.
The table presents some example values. Payloads are not included. The first two are from the detailed design effort at JPL in the 1970s. The third, the lattice sailer, might represent about the best possible performance level. The dimensions for square and lattice sails are edges. The dimension for heliogyro is blade tip to blade tip.
|Type||σ (g/m2)||ac (mm/s2)||λ||Size (km2)|
An active attitude control system (ACS) is essential for a sail craft to achieve and maintain a desired orientation. The required sail orientation changes slowly (often less than 1 degree per day) in interplanetary space, but much more rapidly in a planetary orbit. The ACS must be capable of meeting these orientation requirements. Attitude control is achieved by a relative shift between the craft's center of pressure and its center of mass. This can be achieved with control vanes, movement of individual sails, movement of a control mass, or altering reflectivity.
Holding a constant attitude requires that the ACS maintain a net torque of zero on the craft. The total force and torque on a sail, or set of sails, is not constant along a trajectory. The force changes with solar distance and sail angle, which changes the billow in the sail and deflects some elements of the supporting structure, resulting in changes in the sail force and torque.
Sail temperature also changes with solar distance and sail angle, which changes sail dimensions. The radiant heat from the sail changes the temperature of the supporting structure. Both factors affect total force and torque.
To hold the desired attitude the ACS must compensate for all of these changes.
In Earth orbit, solar pressure and drag pressure are typically equal at an altitude of about 800 km, which means that a sail craft would have to operate above that altitude. Sail craft must operate in orbits where their turn rates are compatible with the orbits, which is generally a concern only for spinning disk configurations.
Sail operating temperatures are a function of solar distance, sail angle, reflectivity, and front and back emissivities. A sail can be used only where its temperature is kept within its material limits. Generally, a sail can be used rather close to the Sun, around 0.25 AU, or even closer if carefully designed for those conditions.
Potential applications for sail craft range throughout the Solar System, from near the Sun to the comet clouds beyond Neptune. The craft can make outbound voyages to deliver loads or to take up station keeping at the destination. They can be used to haul cargo and possibly also used for human travel.
For trips within the inner Solar System, they can deliver loads and then return to Earth for subsequent voyages, operating as an interplanetary shuttle. For Mars in particular, the craft could provide economical means of routinely supplying operations on the planet according to Jerome Wright, "The cost of launching the necessary conventional propellants from Earth are enormous for manned missions. Use of sailing ships could potentially save more than $10 billion in mission costs."
Solar sail craft can approach the Sun to deliver observation payloads or to take up station keeping orbits. They can operate at 0.25 AU or closer. They can reach high orbital inclinations, including polar.
Solar sails can travel to and from all of the inner planets. Trips to Mercury and Venus are for rendezvous and orbit entry for the payload. Trips to Mars could be either for rendezvous or swing-by with release of the payload for aerodynamic braking.
|Mercury Rendezvous||Venus Rendezvous||Mars Rendezvous||Mars Aerobrake|
σ = 5 g/m²
σ = 3 g/m²
Minimum transfer times to the outer planets benefit from using an indirect transfer (solar swing-by). However, this method results in high arrival speeds. Slower transfers have lower arrival speeds.
The minimum transfer time to Jupiter for ac of 1 mm/s2 with no departure velocity relative to Earth is 2 years when using an indirect transfer (solar swing-by). The arrival speed (V∞) is close to 17 km/s. For Saturn, the minimum trip time is 3.3 years, with an arrival speed of nearly 19 km/s.
Minimum times to the outer planets (ac = 1 mm/s2) Jupiter Saturn Uranus Neptune Time, yr 2.0 3.3 5.8 8.5 Speed, km/s 17 19 20 20
Oort Cloud/Sun's inner gravity focus
The Sun's inner gravitational focus point lies at minimum distance of 550 AU from the Sun, and is the point to which light from distant objects is focused by gravity as a result of it passing by the Sun. This is thus the distant point to which solar gravity will cause the region of deep space on the other side of the Sun to be focused, thus serving effectively as a very large telescope objective lens.
It has been proposed that an inflated sail, made of beryllium, that starts at 0.05 AU from the Sun would gain an initial acceleration of 36.4 m/s2, and reach a speed of 0.00264c (about 950 km/s) in less than a day. Such proximity to the Sun could prove to be impractical in the near term due to the structural degradation of beryllium at high temperatures, diffusion of hydrogen at high temperatures as well as an electrostatic gradient, generated by the ionization of beryllium from the solar wind, posing a burst risk. A revised perihelion of 0.1 AU would reduce the aforementioned temperature and solar flux exposure. Such a sail would take "Two and a half years to reach the heliopause, six and a half years to reach the Sun’s inner gravitational focus, with arrival at the inner Oort Cloud in no more than thirty years." "Such a mission could perform useful astrophysical observations en route, explore gravitational focusing techniques, and image Oort Cloud objects while exploring particles and fields in that region that are of galactic rather than solar origin."
Robert L. Forward has commented that a solar sail could be used to modify the orbit of a satellite about the Earth. In the limit, a sail could be used to "hover" a satellite above one pole of the Earth. Spacecraft fitted with solar sails could also be placed in close orbits such that they are stationary with respect to either the Sun or the Earth, a type of satellite named by Forward a "statite". This is possible because the propulsion provided by the sail offsets the gravitational attraction of the Sun. Such an orbit could be useful for studying the properties of the Sun for long durations. Likewise a solar sail-equipped spacecraft could also remain on station nearly above the polar solar terminator of a planet such as the Earth by tilting the sail at the appropriate angle needed to counteract the planet's gravity.
In his book The Case for Mars, Robert Zubrin points out that the reflected sunlight from a large statite, placed near the polar terminator of the planet Mars, could be focused on one of the Martian polar ice caps to significantly warm the planet's atmosphere. Such a statite could be made from asteroid material.
The MESSENGER probe orbiting Mercury used light pressure on its solar panels to perform fine trajectory corrections on the way to Mercury. By changing the angle of the solar panels relative to the Sun, the amount of solar radiation pressure was varied to adjust the spacecraft trajectory more delicately than possible with thrusters. Minor errors are greatly amplified by gravity assist maneuvers, so using radiation pressure to make very small corrections saved large amounts of propellant.
In the science fiction novel Rocheworld, Forward described a light sail propelled by super lasers. As the starship neared its destination, the outer portion of the sail would detach. The outer sail would then refocus and reflect the lasers back onto a smaller, inner sail. This would provide braking thrust to stop the ship in the destination star system.
Both methods pose monumental engineering challenges. The lasers would have to operate for years continuously at gigawatt strength. Forward's solution to this requires enormous solar panel arrays to be built at or near the planet Mercury. A planet-sized mirror or fresnel lens would need to be located at several dozen astronomical units from the Sun to keep the lasers focused on the sail. The giant braking sail would have to act as a precision mirror to focus the braking beam onto the inner "deceleration" sail.
A potentially easier approach would be to use a maser to drive a "solar sail" composed of a mesh of wires with the same spacing as the wavelength of the microwaves directed at the sail, since the manipulation of microwave radiation is somewhat easier than the manipulation of visible light. The hypothetical "Starwisp" interstellar probe design would use microwaves, rather than visible light, to push it. Masers spread out more rapidly than optical lasers owing to their longer wavelength, and so would not have as great an effective range.
Masers could also be used to power a painted solar sail, a conventional sail coated with a layer of chemicals designed to evaporate when struck by microwave radiation. The momentum generated by this evaporation could significantly increase the thrust generated by solar sails, as a form of lightweight ablative laser propulsion.
Another more physically realistic approach would be to use the light from the Sun to accelerate. The ship would first drop into an orbit making a close pass to the Sun, to maximize the solar energy input on the sail, then it would begin to accelerate away from the system using the light from the Sun. Acceleration will drop approximately as the inverse square of the distance from the Sun, and beyond some distance, the ship would no longer receive enough light to accelerate it significantly, but would maintain the final velocity attained. When nearing the target star, the ship could turn its sails toward it and begin to use the outward pressure of the destination star to decelerate. Rockets could augment the solar thrust.
Similar solar sailing launch and capture were suggested for directed panspermia to expand life in other solar system. Velocities of 0.05% the speed of light could be obtained by solar sails carrying 10 kg payloads, using thin solar sail vehicles with effective areal densities of 0.1 g/m2 with thin sails of 0.1 µm thickness and sizes on the order of one square kilometer. Alternatively, swarms of 1 mm capsules could be launched on solar sails with radii of 42 cm, each carrying 10,000 capsules of a hundred million extremophile microorganisms to seed life in diverse target environments.
Theoretical studies suggeset relativistic speeds if the solar sail harnesses a supernova.
Deorbiting artificial satellites
Small solar sails have been proposed to accelerate the deorbiting of small artificial satellites from Earth orbits. Satellites in low Earth orbit can use a combination of solar pressure on the sail and increased atmospheric drag to accelerate satellite reentry. A de-orbit sail developed at Cranfield University is part of the UK satellite TechDemoSat-1, launched in 2014, and is expected to be deployed at the end of the satellite's five-year useful life. The sail's purpose is to bring the satellite out of orbit over a period of about 25 years. In July 2015 British 3U CubeSat called DeorbitSail was launched into space with the purpose of testing 16 m2 deorbit structure, but eventually it failed to deploy it. There is also a student 2U CubeSat mission called PW-Sat2 planned to launch in 2017 that will test 4 m2 deorbit sail. In June 2017 a second British 3U CubeSat called InflateSail deployed a 10 m2 deorbit sail at an altitude of 500 kilometers (310 mi). In June 2017 the 3U Cubesat URSAMAIOR has been launched in Low Earth Orbit to test the deorbiting system ARTICA developed by Spacemind. The device, which occupies only 0.4 U of the cubesat, shall deploy a sail of 2.1 m2 to deorbit the satellite at the end of the operational life
IKAROS, launched in 2010, was the first practical solar sail vehicle. As of 2015, it was still under thrust, proving the practicality of a solar sail for long-duration missions. It is spin-deployed, with tip-masses in the corners of its square sail. The sail is made of thin polyimide film, coated with evaporated aluminium. It steers with electrically-controlled liquid crystal panels. The sail slowly spins, and these panels turn on and off to control the attitude of the vehicle. When on, they diffuse light, reducing the momentum transfer to that part of the sail. When off, the sail reflects more light, transferring more momentum. In that way, they turn the sail. Thin-film solar cells are also integrated into the sail, powering the spacecraft. The design is very reliable, because spin deployment, which is preferable for large sails, simplified the mechanisms to unfold the sail and the LCD panels have no moving parts.
Parachutes have very low mass, but a parachute is not a workable configuration for a solar sail. Analysis shows that a parachute configuration would collapse from the forces exerted by shroud lines, since radiation pressure does not behave like aerodynamic pressure, and would not act to keep the parachute open.
The highest thrust-to-mass designs for ground-assembled deploy-able structures are square sails with the masts and guy lines on the dark side of the sail. Usually there are four masts that spread the corners of the sail, and a mast in the center to hold guy-wires. One of the largest advantages is that there are no hot spots in the rigging from wrinkling or bagging, and the sail protects the structure from the Sun. This form can, therefore, go close to the Sun for maximum thrust. Most designs steer with small moving sails on the ends of the spars.
In the 1970s JPL studied many rotating blade and ring sails for a mission to rendezvous with Halley's Comet. The intention was to stiffen the structures using angular momentum, eliminating the need for struts, and saving mass. In all cases, surprisingly large amounts of tensile strength were needed to cope with dynamic loads. Weaker sails would ripple or oscillate when the sail's attitude changed, and the oscillations would add and cause structural failure. The difference in the thrust-to-mass ratio between practical designs was almost nil, and the static designs were easier to control.
JPL's reference design was called the "heliogyro". It had plastic-film blades deployed from rollers and held out by centrifugal forces as it rotated. The spacecraft's attitude and direction were to be completely controlled by changing the angle of the blades in various ways, similar to the cyclic and collective pitch of a helicopter. Although the design had no mass advantage over a square sail, it remained attractive because the method of deploying the sail was simpler than a strut-based design.
Heliogyro design is similar to the blades on a helicopter. The design is faster to manufacture due to lightweight centrifugal stiffening of sails. Also, they are highly efficient in cost and velocity because the blades are lightweight and long. Unlike the square and spinning disk designs, heliogyro is easier to deploy because the blades are compacted on a reel. The blades roll out when they are deploying after the ejection from the spacecraft. As the heliogyro travels through space the system spins around because of the centrifugal acceleration. Finally, payloads for the space flights are placed in the center of gravity to even out the distribution of weight to ensure stable flight.
JPL also investigated "ring sails" (Spinning Disk Sail in the above diagram), panels attached to the edge of a rotating spacecraft. The panels would have slight gaps, about one to five percent of the total area. Lines would connect the edge of one sail to the other. Masses in the middles of these lines would pull the sails taut against the coning caused by the radiation pressure. JPL researchers said that this might be an attractive sail design for large manned structures. The inner ring, in particular, might be made to have artificial gravity roughly equal to the gravity on the surface of Mars.
A solar sail can serve a dual function as a high-gain antenna. Designs differ, but most modify the metalization pattern to create a holographic monochromatic lens or mirror in the radio frequencies of interest, including visible light.
Electric solar wind sail
Pekka Janhunen from FMI has invented a type of solar sail called the electric solar wind sail. Mechanically it has little in common with the traditional solar sail design. The sails are replaced with straightened conducting tethers (wires) placed radially around the host ship. The wires are electrically charged to create an electric field around the wires. The electric field extends a few tens of metres into the plasma of the surrounding solar wind. The solar electrons are reflected by the electric field (like the photons on a traditional solar sail). The radius of the sail is from the electric field rather than the actual wire itself, making the sail lighter. The craft can also be steered by regulating the electric charge of the wires. A practical electric sail would have 50–100 straightened wires with a length of about 20 km each.
Electric solar wind sails can adjust their electrostatic fields and sail attitudes.
A magnetic sail would also employ the solar wind. However, the magnetic field deflects the electrically charged particles in the wind. It uses wire loops, and runs a static current through them instead of applying a static voltage.
All these designs maneuver, though the mechanisms are different.
Magnetic sails bend the path of the charged protons that are in the solar wind. By changing the sails' attitudes, and the size of the magnetic fields, they can change the amount and direction of the thrust.
The most common material in current designs is a thin layer of aluminum coating on a polymer (plastic) sheet, such as aluminized 2 µm Kapton film. The polymer provides mechanical support as well as flexibility, while the thin metal layer provides the reflectivity. Such material resists the heat of a pass close to the Sun and still remains reasonably strong. The aluminum reflecting film is on the Sun side. The sails of Cosmos 1 were made of aluminized PET film (Mylar).
Eric Drexler developed a concept for a sail in which the polymer was removed. He proposed very high thrust-to-mass solar sails, and made prototypes of the sail material. His sail would use panels of thin aluminium film (30 to 100 nanometres thick) supported by a tensile structure. The sail would rotate and would have to be continually under thrust. He made and handled samples of the film in the laboratory, but the material was too delicate to survive folding, launch, and deployment. The design planned to rely on space-based production of the film panels, joining them to a deploy-able tension structure. Sails in this class would offer high area per unit mass and hence accelerations up to "fifty times higher" than designs based on deploy-able plastic films. The material developed for the Drexler solar sail was a thin aluminium film with a baseline thickness of 0.1 µm, to be fabricated by vapor deposition in a space-based system. Drexler used a similar process to prepare films on the ground. As anticipated, these films demonstrated adequate strength and robustness for handling in the laboratory and for use in space, but not for folding, launch, and deployment.
Research by Geoffrey Landis in 1998–1999, funded by the NASA Institute for Advanced Concepts, showed that various materials such as alumina for laser lightsails and carbon fiber for microwave pushed lightsails were superior sail materials to the previously standard aluminium or Kapton films.
In 2000, Energy Science Laboratories developed a new carbon fiber material that might be useful for solar sails. The material is over 200 times thicker than conventional solar sail designs, but it is so porous that it has the same mass. The rigidity and durability of this material could make solar sails that are significantly sturdier than plastic films. The material could self-deploy and should withstand higher temperatures.
There has been some theoretical speculation about using molecular manufacturing techniques to create advanced, strong, hyper-light sail material, based on nanotube mesh weaves, where the weave "spaces" are less than half the wavelength of light impinging on the sail. While such materials have so far only been produced in laboratory conditions, and the means for manufacturing such material on an industrial scale are not yet available, such materials could mass less than 0.1 g/m2, making them lighter than any current sail material by a factor of at least 30. For comparison, 5 micrometre thick Mylar sail material mass 7 g/m2, aluminized Kapton films have a mass as much as 12 g/m2, and Energy Science Laboratories' new carbon fiber material masses 3 g/m2.
The least dense metal is lithium, about 5 times less dense than aluminium. Fresh, unoxidized surfaces are reflective. At a thickness of 20 nm, lithium has an area density of 0.011 g/m2. A high-performance sail could be made of lithium alone at 20 nm (no emission layer). It would have to be fabricated in space and not used to approach the Sun. In the limit, a sail craft might be constructed with a total areal density of around 0.02 g/m2, giving it a lightness number of 67 and ac of about 400 mm/s2. Magnesium and beryllium are also potential materials for high-performance sails. These 3 metals can be alloyed with each other and with aluminium.
Reflection and emissivity layers
Aluminium is the common choice for the reflection layer. It typically has a thickness of at least 20 nm, with a reflectivity of 0.88 to 0.90. Chromium is a good choice for the emission layer on the face away from the Sun. It can readily provide emissivity values of 0.63 to 0.73 for thicknesses from 5 to 20 nm on plastic film. Usable emissivity values are empirical because thin-film effects dominate; bulk emissivity values do not hold up in these cases because material thickness is much thinner than the emitted wavelengths.
Sails are fabricated on Earth on long tables where ribbons are unrolled and joined to create the sails. Sail material needed to have as little weight as possible because it would require the use of the shuttle to carry the craft into orbit. Thus, these sails are packed, launched, and unfurled in space.
In the future, fabrication could take place in orbit inside large frames that support the sail. This would result in lower mass sails and elimination of the risk of deployment failure.
Sailing operations are simplest in interplanetary orbits, where altitude changes are done at low rates. For outward bound trajectories, the sail force vector is oriented forward of the Sun line, which increases orbital energy and angular momentum, resulting in the craft moving farther from the Sun. For inward trajectories, the sail force vector is oriented behind the Sun line, which decreases orbital energy and angular momentum, resulting in the craft moving in toward the Sun. It is worth noting that only the Sun's gravity pulls the craft toward the Sun—there is no analog to a sailboat's tacking to windward. To change orbital inclination, the force vector is turned out of the plane of the velocity vector.
In orbits around planets or other bodies, the sail is oriented so that its force vector has a component along the velocity vector, either in the direction of motion for an outward spiral, or against the direction of motion for an inward spiral.
Trajectory optimizations can often require intervals of reduced or zero thrust. This can be achieved by rolling the craft around the Sun line with the sail set at an appropriate angle to reduce or remove the thrust.
A close solar passage can be used to increase a craft's energy. The increased radiation pressure combines with the efficacy of being deep in the Sun's gravity well to substantially increase the energy for runs to the outer Solar System. The optimal approach to the Sun is done by increasing the orbital eccentricity while keeping the energy level as high as practical. The minimum approach distance is a function of sail angle, thermal properties of the sail and other structure, load effects on structure, and sail optical characteristics (reflectivity and emissivity). A close passage can result in substantial optical degradation. Required turn rates can increase substantially for a close passage. A sail craft arriving at a star can use a close passage to reduce energy, which also applies to a sail craft on a return trip from the outer Solar System.
A lunar swing-by can have important benefits for trajectories leaving from or arriving at Earth. This can reduce trip times, especially in cases where the sail is heavily loaded. A swing-by can also be used to obtain favorable departure or arrival directions relative to Earth.
A planetary swing-by could also be employed similar to what is done with coasting spacecraft, but good alignments might not exist due to the requirements for overall optimization of the trajectory.
|Mission||Laser Power||Vehicle Mass||Acceleration||Sail Diameter||Maximum Velocity (% of the speed of light)|
|1. Flyby – Alpha Centauri, 40 years|
|outbound stage||65 GW||1 t||0.036 g||3.6 km||11% @ 0.17 ly|
|2. Rendezvous – Alpha Centauri, 41 years|
|outbound stage||7,200 GW||785 t||0.005 g||100 km||21% @ 4.29 ly|
|deceleration stage||26,000 GW||71 t||0.2 g||30 km||21% @ 4.29 ly|
|3. Manned – Epsilon Eridani, 51 years (including 5 years exploring star system)|
|outbound stage||75,000,000 GW||78,500 t||0.3 g||1000 km||50% @ 0.4 ly|
|deceleration stage||21,500,000 GW||7,850 t||0.3 g||320 km||50% @ 10.4 ly|
|return stage||710,000 GW||785 t||0.3 g||100 km||50% @ 10.4 ly|
|deceleration stage||60,000 GW||785 t||0.3 g||100 km||50% @ 0.4 ly|
Interstellar travel catalog to use photogravitational assists for a full stop.
|α Centauri A||101.25||4.36||1.52|
|α Centauri B||147.58||4.36||0.50|
- Successive assists at α Cen A and B could allow travel times to 75 yr to both stars.
- Lightsail has a nominal mass-to-surface ratio (σnom) of 8.6×10−4 gram m−2 for a nominal graphene-class sail.
- Area of the Lightsail, about 105 m2 = (316 m)2
- Velocity up to 37,300 km s−1 (12.5% c)
Projects operating or completed
Attitude (orientation) control
Both the Mariner 10 mission, which flew by the planets Mercury and Venus, and the MESSENGER mission to Mercury demonstrated the use of solar pressure as a method of attitude control in order to conserve attitude-control propellant.
MTSAT-1R (Multi-Functional Transport Satellite)'s solar sail counteracts the torque produced by sunlight pressure on the solar array. The trim tab on the solar array makes small adjustments to the torque balance.
Ground deployment tests
NASA has successfully tested deployment technologies on small scale sails in vacuum chambers.
On February 4, 1993, the Znamya 2, a 20-meter wide aluminized-mylar reflector, was successfully deployed from the Russian Mir space station. Although the deployment succeeded, propulsion was not demonstrated. A second test, Znamya 2.5, failed to deploy properly.
In 1999, a full-scale deployment of a solar sail was tested on the ground at DLR/ESA in Cologne.
A 15-meter-diameter solar sail (SSP, solar sail sub payload, soraseiru sabupeiro-do) was launched together with ASTRO-F on a M-V rocket on February 21, 2006, and made it to orbit. It deployed from the stage, but opened incompletely.
On August 9, 2004, the Japanese ISAS successfully deployed two prototype solar sails from a sounding rocket. A clover-shaped sail was deployed at 122 km altitude and a fan-shaped sail was deployed at 169 km altitude. Both sails used 7.5-micrometer film. The experiment purely tested the deployment mechanisms, not propulsion.
On 21 May 2010, Japan Aerospace Exploration Agency (JAXA) launched the world's first interplanetary solar sail spacecraft "IKAROS" (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) to Venus. Using a new solar-photon propulsion method, it was the first true solar sail spacecraft fully propelled by sunlight, and was the first spacecraft to succeed in solar sail flight.
JAXA successfully tested IKAROS in 2010. The goal was to deploy and control the sail and, for the first time, to determine the minute orbit perturbations caused by light pressure. Orbit determination was done by the nearby AKATSUKI probe from which IKAROS detached after both had been brought into a transfer orbit to Venus. The total effect over the six month flight was 100 m/s.
Until 2010, no solar sails had been successfully used in space as primary propulsion systems. On 21 May 2010, the Japan Aerospace Exploration Agency (JAXA) launched the IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) spacecraft, which deployed a 200 m2 polyimide experimental solar sail on June 10. In July, the next phase for the demonstration of acceleration by radiation began. On 9 July 2010, it was verified that IKAROS collected radiation from the Sun and began photon acceleration by the orbit determination of IKAROS by range-and-range-rate (RARR) that is newly calculated in addition to the data of the relativization accelerating speed of IKAROS between IKAROS and the Earth that has been taken since before the Doppler effect was utilized. The data showed that IKAROS appears to have been solar-sailing since 3 June when it deployed the sail.
IKAROS has a diagonal spinning square sail 14×14 m (196 m2) made of a 7.5-micrometre (0.0075 mm) thick sheet of polyimide. The polyimide sheet had a mass of about 10 grams per square metre. A thin-film solar array is embedded in the sail. Eight LCD panels are embedded in the sail, whose reflectance can be adjusted for attitude control. IKAROS spent six months traveling to Venus, and then began a three-year journey to the far side of the Sun.
A team from the NASA Marshall Space Flight Center (Marshall), along with a team from the NASA Ames Research Center, developed a solar sail mission called NanoSail-D, which was lost in a launch failure aboard a Falcon 1 rocket on 3 August 2008. The second backup version, NanoSail-D2, also sometimes called simply NanoSail-D, was launched with FASTSAT on a Minotaur IV on November 19, 2010, becoming NASA's first solar sail deployed in low earth orbit. The objectives of the mission were to test sail deployment technologies, and to gather data about the use of solar sails as a simple, "passive" means of de-orbiting dead satellites and space debris. The NanoSail-D structure was made of aluminium and plastic, with the spacecraft massing less than 10 pounds (4.5 kg). The sail has about 100 square feet (9.3 m2) of light-catching surface. After some initial problems with deployment, the solar sail was deployed and over the course of its 240-day mission reportedly produced a "wealth of data" concerning the use of solar sails as passive deorbit devices.
NASA launched the second NanoSail-D unit stowed inside the FASTSAT satellite on the Minotaur IV on November 19, 2010. The ejection date from the FASTSAT microsatellite was planned for December 6, 2010, but deployment only occurred on January 20, 2011.
Planetary Society LightSail Projects
In June 21, 2005, a joint private project between Planetary Society, Cosmos Studios and Russian Academy of Science launched a prototype sail Cosmos 1 from a submarine in the Barents Sea, but the Volna rocket failed, and the spacecraft failed to reach orbit. They intended to use the sail to gradually raise the spacecraft to a higher Earth orbit over a mission duration of one month. The launch attempt sparked public interest according to Louis Friedman. Despite the failed launch attempt of Cosmos 1, The Planetary Society received applause for their efforts from the space community and sparked a rekindled interest in solar sail technology.
On Carl Sagan's 75th birthday (November 9, 2009) the Planetary Society announced plans to make three further attempts, dubbed LightSail-1, -2, and -3. The new design will use a 32 m2 Mylar sail, deployed in four triangular segments like NanoSail-D. The launch configuration is a 3U CubeSat format, and as of 2015, it was scheduled as a secondary payload for a 2016 launch on the first SpaceX Falcon Heavy launch.
"LightSail-1" was launched on 20 May 2015. The purpose of the test was to allow a full checkout of the satellite's systems in advance of LightSail-2. Its deployment orbit was not high enough to escape Earth's atmospheric drag and demonstrate true solar sailing.
Projects in development or proposed
Despite the losses of Cosmos 1 and NanoSail-D (which were due to failure of their launchers), scientists and engineers around the world remain encouraged and continue to work on solar sails. While most direct applications created so far intend to use the sails as inexpensive modes of cargo transport, some scientists are investigating the possibility of using solar sails as a means of transporting humans. This goal is strongly related to the management of very large (i.e. well above 1 km2) surfaces in space and the sail making advancements. Development of solar sails for manned space flight is still in its infancy.
A technology demonstration sail craft, dubbed Sunjammer, was in development with the intent to prove the viability and value of sailing technology. Sunjammer had a square sail, 124 feet (38 meters) wide on each side (total area 13,000 sq ft or 1,208 sq m). It would have traveled from the Sun-Earth L1 Lagrangian point 900,000 miles from Earth (1.5 million km) to a distance of 1,864,114 miles (3 million kilometers). The demonstration was expected to launch on a Falcon 9 in January 2015. It would have been a secondary payload, released after the placement of the DSCOVR climate satellite at the L1 point. Citing a lack of confidence in the ability of its contractor L'Garde to deliver, the mission was cancelled in October 2014.
Gossamer deorbit sail
As of December 2013[update], the European Space Agency (ESA) has a proposed deorbit sail, named "Gossamer", that would be intended to be used to accelerate the deorbiting of small (less than 700 kilograms (1,500 lb)) artificial satellites from low-Earth orbits. The launch mass is 2 kilograms (4.4 lb) with a launch volume of only 15×15×25 centimetres (0.49×0.49×0.82 ft). Once deployed, the sail would expand to 5 by 5 metres (16 ft × 16 ft) and would use a combination of solar pressure on the sail and increased atmospheric drag to accelerate satellite reentry.
The Near-Earth Asteroid Scout (NEA Scout) is a mission being jointly developed by NASA's Marshall Space Flight Center (MSFC) and the Jet Propulsion Laboratory (JPL), consisting of a controllable low-cost CubeSat solar sail spacecraft capable of encountering near-Earth asteroids (NEA). Four 7 m (23 ft) booms would deploy, unfurling the 83 m2 (890 sq ft) aluminized polyimide solar sail. In 2015, NASA announced it had selected NEA Scout to launch as one of several secondary payloads aboard Artemis 1, the first flight of the agency's heavy-lift SLS launch vehicle.
OKEANOS (Outsized Kite-craft for Exploration and Astronautics in the Outer Solar System) is a proposed mission concept by Japan's JAXA to Jupiter's Trojan asteroids using a hybrid solar sail for propulsion; the sail is covered with thin solar panels to power an ion engine. In-situ analysis of the collected samples would be performed by either direct contact or using a lander carrying a high-resolution mass spectrometer. A lander and a sample-return to Earth are options under study. The OKEANOS Jupiter Trojan Asteroid Explorer is a finalist for Japan's ISAS' 2nd Large-class mission to be launched in the late 2020s.
The well-funded Breakthrough Starshot project announced in April 12, 2016, aims to develop a fleet of 1000 light sail nanocraft carrying miniature cameras, propelled by ground-based lasers and send them to Alpha Centauri at 20% the speed of light. The trip would take 20 years.
In August 2019, NASA awarded the Solar Cruiser team $400,000 for nine-month mission concept studies. The spacecraft would have a 1,672 m2 (18,000 sq ft) solar sail and would orbit the Sun in a polar orbit, while the coronagraph instrument would enable simultaneous measurements of the Sun's magnetic field structure and velocity of coronal mass ejections. If selected for development, it would launch in 2024.
In popular culture
A similar technology appeared in the Star Trek: Deep Space Nine episode, Explorers. In the episode, Lightships are described as an ancient technology used by Bajorans to travel beyond their solar system by using light from the Bajoran sun and specially constructed sails to propel them through space ("Explorers". Star Trek: Deep Space Nine. Season 3. Episode 22.).
A space sail is used in the novel Planet of the Apes.
- CubeSail – A planned solar sail spacecraft
- LightSail – Project to demonstrate controlled solar sailing in low Earth orbit
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Sometimes the satellite is called NanoSail-D and sometimes NanoSail-D2. ... Dean: The project is just NanoSail-D. NanoSail-D2 is the serial #2 version.
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- "NEA Scout". NASA. 2015-10-30. Retrieved February 11, 2016.
- McNutt, Leslie; Castillo-Rogez, Julie (2014). "Near-Earth Asteroid Scout" (PDF). NASA. American Institute of Aeronautics and Astronautics. Retrieved 2015-05-13.
- Krebs, Gunter Dirk (13 April 2015). "NEA-Scout". Retrieved 2015-05-13.
- Castillo-Rogez, Julie; Abell, Paul. "Near Earth Asteroid Scout Mission" (PDF). NASA. Lunar and Planetary Institute. Retrieved 2015-05-13.
- Gebhardt, Chris (November 27, 2015). "NASA identifies secondary payloads for SLS's EM-1 mission". NASAspaceflight.
- Sampling Scenario for the Trojan Asteroid Exploration Mission Archived 2017-12-31 at the Wayback Machine (PDF). Jun Matsumoto, Jun Aoki, Yuske Oki, Hajime Yano. 2015.
- "Breakthrough Starshot". Breakthrough Initiatives. 12 April 2016. Retrieved 2016-04-12.
- Starshot - Concept.
- "Breakthrough Initiatives". breakthroughinitiatives.org.
- NASA Selects Proposals to Demonstrate SmallSat Technologies to Study Interplanetary Space. NASA press release, 15 August 2019.
- ""Star Trek Deep Space Nine" Explorers (TV Episode 1995) - IMDB". IMDB. 8 February 2018.
- G. Vulpetti, Fast Solar Sailing: Astrodynamics of Special Sailcraft Trajectories, ;;Space Technology Library Vol. 30, Springer, August 2012, (Hardcover) https://www.springer.com/engineering/mechanical+engineering/book/978-94-007-4776-0, (Kindle-edition), ASIN: B00A9YGY4I
- G. Vulpetti, L. Johnson, G. L. Matloff, Solar Sails: A Novel Approach to Interplanetary Flight, Springer, August 2008, ISBN 978-0-387-34404-1
- J. L. Wright, Space Sailing, Gordon and Breach Science Publishers, London, 1992; Wright was involved with JPL's effort to use a solar sail for a rendezvous with Halley's comet.
- NASA/CR 2002-211730, Chapter IV— presents an optimized escape trajectory via the H-reversal sailing mode
- G. Vulpetti, The Sailcraft Splitting Concept, JBIS, Vol. 59, pp. 48–53, February 2006
- G. L. Matloff, Deep-Space Probes: To the Outer Solar System and Beyond, 2nd ed., Springer-Praxis, UK, 2005, ISBN 978-3-540-24772-2
- T. Taylor, D. Robinson, T. Moton, T. C. Powell, G. Matloff, and J. Hall, "Solar Sail Propulsion Systems Integration and Analysis (for Option Period)", Final Report for NASA/MSFC, Contract No. H-35191D Option Period, Teledyne Brown Engineering Inc., Huntsville, AL, May 11, 2004
- G. Vulpetti, "Sailcraft Trajectory Options for the Interstellar Probe: Mathematical Theory and Numerical Results", the Chapter IV of NASA/CR-2002-211730, The Interstellar Probe (ISP): Pre-Perihelion Trajectories and Application of Holography, June 2002
- G. Vulpetti, Sailcraft-Based Mission to The Solar Gravitational Lens, STAIF-2000, Albuquerque (New Mexico, USA), 30 January – 3 February 2000
- G. Vulpetti, "General 3D H-Reversal Trajectories for High-Speed Sailcraft", Acta Astronautica, Vol. 44, No. 1, pp. 67–73, 1999
- C. R. McInnes, Solar Sailing: Technology, Dynamics, and Mission Applications, Springer-Praxis Publishing Ltd, Chichester, UK, 1999, ISBN 978-3-540-21062-7
- Genta, G., and Brusa, E., "The AURORA Project: a New Sail Layout", Acta Astronautica, 44, No. 2–4, pp. 141–146 (1999)
- S. Scaglione and G. Vulpetti, "The Aurora Project: Removal of Plastic Substrate to Obtain an All-Metal Solar Sail", special issue of Acta Astronautica, vol. 44, No. 2–4, pp. 147–150, 1999
|Wikimedia Commons has media related to Solar sails.|
- "Deflecting Asteroids" by Gregory L. Matloff, IEEE Spectrum, April 2012
- Planetary Society's solar sailing project
- The Solar Photon Sail Comes of Age by Gregory L. Matloff
- NASA Mission Site for NanoSail-D
- NanoSail-D mission: Dana Coulter, "NASA to Attempt Historic Solar Sail Deployment", NASA, June 28, 2008
- Far-out Pathways to Space: Solar Sails from NASA
- Solar Sails Comprehensive collection of solar sail information and references, maintained by Benjamin Diedrich. Good diagrams showing how light sailors must tack.
- U3P Multilingual site with news and flight simulators
- ISAS Deployed Solar Sail Film in Space
- Suggestion of a solar sail with roller reefing, hybrid propulsion and a central docking and payload station.
- Interview with NASA's JPL about solar sail technology and missions
- Website with technical pdf-files about solar-sailing, including NASA report and lectures at Aerospace Engineering School of Rome University
- Advanced Solar- and Laser-pushed Lightsail Concepts
- Andrews, D. G. (2003). "Interstellar Transportation using Today's Physics" (PDF). AIAA Paper 2003-4691. Archived from the original (PDF) on 2006-03-11.
- www.aibep.org: Official site of American Institute of Beamed Energy Propulsion
- Space Sailing Sailing ship concepts, operations, and history of concept
- Bernd Dachwald's Website Broad information on sail propulsion and missions | 0.851439 | 3.846907 |
The stars of our Milky Way Galaxy are separated from a person another by very good distances, as they perform their sparkling dance within the frigid darkness of interstellar space. Certainly, the length to even the nearest star beyond our individual Solar is sort of unimaginably vast–our closest stellar neighbor is in fact a triple star scheme named Alpha Centauri, which is certainly 4 light-years away, or 24 trillion miles! The separation relating to stars is so extremely super that it really should be measured in light-years, and mainly because light travels at 186,000 miles per 2nd inside of a vacuum, this means that 1 light yr is equal to six trillion miles. The quest to find planets in orbit near stars beyond our Solar, even though historically difficult, has now yielded an brilliant bundle of strange and wild worlds within a celestial Wonderland that delights the imaginations of their curious observers. In February 2018, astronomers announced their particular fascinating discovery, inhabiting this strange celestial Wonderland–a star approximately 100 light-years away from the Pisces constellation hosts what could very well be a person within the most massive and dense super-Earth planets spotted to date.
Related to earth cam new orleans, Why was the Earth put together? Why are we, as human beings, even here? The answers to these and a lot of other effective questions might possibly be noticed in God’s letter to us, the Bible. By taking the text again on the original language, we are able to know and understand what is undoubtedly becoming reported. Get started your journey over a nearer walk with your heavenly Father in the present day.
For practically a era now, the hunt for Earth-like alien worlds, orbiting stars beyond our personal Sunshine, has accelerated greatly primarily as being a outcome in the start of highly successful space missions these types of given that the Kepler Space Telescope and other instruments. These new technologies have enabled astronomers to find and characterize literally many hundreds brave new worlds, with hundreds of many people awaiting confirmation. As routines continue to improve, astronomers will likely be better capable of spot ever smaller and smaller worlds, eventually identifying Earth-sized exoplanets. Super-Earths are exoworlds defined by their mass, which happens to be higher than Earth’s, but substantially beneath that for the smaller giant denizens of our Solar Program, the ice-giant planets, Uranus and Neptune –the term does not indicate compositions, orbital homes, temperatures, general environmental characteristics, and habitability. In February 2014, a study conducted by a team of planetary scientists, published in “Monthly Notices from the Royal Astronomical Society” in London, suggests that alien worlds which have been born from less massive cores can developed into welcoming would-be habitats for lifestyle as we all know it–whereas the larger cores tragically wind up as “mini-Neptunes,” with heavy, thick atmospheres, rendering them barren, dead worlds.
Although the historical past of Earth Day is commonly associated with U.S. Senator Gaylord Nelson of Wisconsin, and Congressman Pete McCloskey of California, it’s been alleged which the idea originated initially in 1969 with John McConnell at an UNESCO conference held in San Francisco. But nevertheless the origins of Earth Working day started, its clear that this party has deeply resonated with citizens across the world.
Diatomaceous earth is actually a organic, inexpensive substance in existence that may not merely help you get rid in the pesky insects in your own lawn and garden, but will also detoxify and remove the parasites out of your personal body too. Diatomaceous earth is non-toxic to individuals and animals, but could be a versatile agent that is a must-have inside your preparedness pantry. This can be connected to earth cam new orleans.
Element three belonging to the New World Earth Series will be the last explanation of unity consciousness. This idea, to be the cornerstone of all other attributes in the new earth earth, is supplied an in depth assessment.
Okay so, is Chicken Little Real – is Chicken Modest accurate? Nicely, it depends on what she’s saying for the time. Consider the boy who cried wolf was producing it up the 1st couple times, but then when it incredibly happened not a soul listened, because he’d played that card too a large number of times, and they figured he was bluffing.
During the tragicomedy that characterizes human relationships, it’s been stated which the nearer we reach someone, the weirder that individual gets. Earth’s Moon is our planet’s closest neighbor in Space–mysterious, bewitching, bothersome, and bewildering, it has successfully hidden loads of of its secrets from the prying eyes of curious observers. In July 2017, utilizing satellite info, a team of astronomers announced which they have, with the primary time, detected widespread drinking water hidden inside historic explosive volcanic material on Earth’s nearest and dearest companion earth. This discovery implies the interior of Earth’s Moon contains large quantities of indigenous h2o, that has finally been revealed in numerous volcanic deposits distributed across the lunar surface–and these historic deposits contain unusually significant amounts of imprisoned h2o compared with surrounding terrains.
The planet is within dear will need a change, how will you turn it into a better place? Individuals have suggested many solutions and they’re yet to create an effect. The reality remains the real cause from the problems is not addressed. This short article is aimed at addressing this. | 0.932071 | 3.081111 |
Quarter ♋ Cancer
Moon phase on 12 March 2076 Thursday is First Quarter, 7 days young Moon is in Gemini.Share this page: twitter facebook linkedin
First Quarter is the lunar phase on . Seen from Earth, illuminated fraction of the Moon surface is 50% and growing larger. The 7 days young Moon is in ♊ Gemini.
* The exact date and time of this First Quarter phase is on 12 March 2076 at 12:41 UTC.
Moon rises at noon and sets at midnight. It is visible high in the southern sky in early evening.
Moon is passing about ∠22° of ♊ Gemini tropical zodiac sector.
Lunar disc appears visually 7.3% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1793" and ∠1930".
Next Full Moon is the Worm Moon of March 2076 after 8 days on 20 March 2076 at 16:37.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 7 days young. Earth's natural satellite is moving through the first part of current synodic month. This is lunation 942 of Meeus index or 1895 from Brown series.
Length of current 942 lunation is 29 days, 10 hours and 23 minutes. It is 42 minutes shorter than next lunation 943 length.
Length of current synodic month is 2 hours and 21 minutes shorter than the mean length of synodic month, but it is still 3 hours and 48 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠26.4°. At beginning of next synodic month true anomaly will be ∠48.3°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
8 days after point of perigee on 3 March 2076 at 17:20 in ♒ Aquarius. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 3 days, until it get to the point of next apogee on 15 March 2076 at 16:37 in ♋ Cancer.
Moon is 399 664 km (248 340 mi) away from Earth on this date. Moon moves farther next 3 days until apogee, when Earth-Moon distance will reach 405 173 km (251 763 mi).
12 days after its descending node on 29 February 2076 at 09:23 in ♑ Capricorn, the Moon is following the southern part of its orbit for the next day, until it will cross the ecliptic from South to North in ascending node on 13 March 2076 at 06:34 in ♋ Cancer.
26 days after beginning of current draconic month in ♋ Cancer, the Moon is moving from the second to the final part of it.
11 days after previous South standstill on 29 February 2076 at 23:45 in ♑ Capricorn, when Moon has reached southern declination of ∠-23.705°. Next day the lunar orbit moves northward to face North declination of ∠23.806° in the next northern standstill on 14 March 2076 at 02:15 in ♋ Cancer.
After 8 days on 20 March 2076 at 16:37 in ♍ Virgo, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.182034 |
September 12, 2019
We can build again, when our own world is destroyed by global warming and the oil companies or whatever.
For the first time, astronomers looking beyond our solar system have spotted water vapor in the atmosphere of a planet where temperatures might also be just right for life.
Exoplanet K2-18b is a super-Earth that’s twice the size of our planet, with eight times the mass. It’s also wet, or at least the skies around it are. Researchers found evidence of water vapor when they took data captured by NASA’s Hubble Space Telescope in 2016 and 2017 and ran it through an open-source algorithm they developed to analyze distant planets. They published their findings Wednesday in the journal Nature.
Water vapor has been found in the atmospheres of other planets, but this is the first time such moisture has been spotted at a planet in the habitable zone of its star, where temperatures could be tolerable, if not downright pleasant.
More data is needed to determine what kind of cloud coverage the planet has, how much water is present in the atmosphere and if the stuff is actually forming big bodies of water on the planet’s surface like here on Earth.
“It’s entirely possible this is a water world,” said co-author Giovanna Tinetti, a professor of astrophysics at University College London. But she cautioned that it’s too early to confirm the presence of some sort of surface ocean.
It’s estimated that temperatures on the planet could be between about minus 100 degrees Fahrenheit (minus 73 Celsius) and 150 Fahrenheit (66 Celsius). That’s a big range, of course, but it’s not too far off from the conditions we see here on Earth.
The first thing we’re going to need to do is send in a team to set up dilation stations across the entire surface of the planet, so that the trannies can be certain that wherever they are, they can dilate their neo-vaginas.
Then we’re going to need to set up free needle dispensaries.
Then we’re going to have to set up ramps for cripples.
We’re going to need EBT card refill stations.
Liquor stores with bulletproof glass.
And fried chicken joints with bulletproof glass.
We’re going to need mosques.
And of course we’re going to need streets for gay sex parades.
Once we have all that set up then maybe – just maybe – we’ll be able to start talking about building a civilization on another planet. | 0.850229 | 3.324466 |
Crescent ♈ Aries
Moon phase on 1 June 2013 Saturday is Last Quarter, 22 days old Moon is in Pisces.Share this page: twitter facebook linkedin
Last Quarter is the lunar phase on . Seen from Earth, illuminated fraction of the Moon surface is 43% and getting smaller. The 22 days old Moon is in ♓ Pisces.
* The exact date and time of this Last Quarter phase is on 31 May 2013 at 18:58 UTC.
Moon rises at midnight and sets at noon. It is visible to the south in the morning.
Moon is passing about ∠20° of ♓ Pisces tropical zodiac sector.
Lunar disc appears visually 0.2% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1887" and ∠1892".
Next Full Moon is the Strawberry Moon of June 2013 after 21 days on 23 June 2013 at 11:32.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 22 days old. Earth's natural satellite is moving through the last part of current synodic month. This is lunation 165 of Meeus index or 1118 from Brown series.
Length of current 165 lunation is 29 days, 15 hours and 28 minutes. This is the year's longest synodic month of 2013. It is 10 minutes longer than next lunation 166 length.
Length of current synodic month is 2 hours and 44 minutes longer than the mean length of synodic month, but it is still 4 hours and 19 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠143.3°. At beginning of next synodic month true anomaly will be ∠168.8°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
6 days after point of perigee on 26 May 2013 at 01:45 in ♐ Sagittarius. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 8 days, until it get to the point of next apogee on 9 June 2013 at 21:40 in ♊ Gemini.
Moon is 379 758 km (235 971 mi) away from Earth on this date. Moon moves farther next 8 days until apogee, when Earth-Moon distance will reach 406 487 km (252 579 mi).
8 days after its ascending node on 24 May 2013 at 00:40 in ♏ Scorpio, the Moon is following the northern part of its orbit for the next 4 days, until it will cross the ecliptic from North to South in descending node on 6 June 2013 at 00:59 in ♉ Taurus.
8 days after beginning of current draconic month in ♏ Scorpio, the Moon is moving from the beginning to the first part of it.
6 days after previous South standstill on 26 May 2013 at 04:47 in ♐ Sagittarius, when Moon has reached southern declination of ∠-20.182°. Next 7 days the lunar orbit moves northward to face North declination of ∠20.200° in the next northern standstill on 8 June 2013 at 19:16 in ♊ Gemini.
After 7 days on 8 June 2013 at 15:56 in ♊ Gemini, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.1602 |
Geologic Atlas of the Moon
The purpose of the lunar maps presented here is to provide an up-to-date and comprehensive depiction of lunar nomenclature. As new names are approved, they are added to the maps so users have access to the most recent changes in lunar nomenclature.
The International Astronomical Union (IAU) is the internationally recognized authority for assigning nomenclature to planetary surface features. The lunar maps on this web site are based on the information contained in the Gazetteer of Planetary Nomenclature, which is a dynamic listing of IAU-approved planetary surface feature names. The Astrogeology Science Center of the U.S. Geological Survey maintains the Gazetteer of Planetary Nomenclature on behalf of the IAU with funding from the National Aeronautics and Space Administration (NASA).
At the time of this writing, there are 9,003 IAU-approved names in use on the Moon (not including names that have been dropped but are retained in the gazetteer for reference). These names are of various feature types: catenae, craters, dorsa, fossae, lacūs, landing site names, maria, montes, oceanus, paludes, planitiae, promontoria, rimae, rupēs, lettered craters (called “satellite features” in the gazetteer), sinūs, and valles. The maps shown here include only names that are formally approved by the IAU and are currently in use. The lettered crater names included in the Gazetteer of Planetary Nomenclature, and therefore in this atlas, are found in the definitive source “NASA Catalogue of Lunar Nomenclature” (NASA Reference Publication 1097). Over the decades, many informal names have been used on the Moon and some IAU-approved names have been officially changed. Informal names and names that have been changed are not shown. Cross references between these old and new names have been noted in the “Additional Information” field of the gazetteer. This is not a complete record of cross references, only those discovered during the research for these maps.
These maps are kept up-to-date. As new names are approved by the IAU, they will be added to the maps. If a name is dropped, it will be removed, and if a feature is renamed, the new name will replace the old name. Whenever there is a change to the lunar portion of the Gazetteer of Planetary Nomenclature, that change will be shown on the corresponding map, and a revision date will be added to the map. Changes to the gazetteer listings are recorded in the “News” section on the title page of the gazetteer. The IAU name approval process is also described in the gazetteer. | 0.836093 | 3.349164 |
During the night, the sky is filled with tiny dots that appear to be glowing. These dots are only visible when the night sky is clear and if no clouds present. Some of the dots are stars while others are planets. But how is it possible for someone looking at them to differentiate between two based on how they look and behave?
The first difference between the two bodies is obviously their definition. A star is a celestial body that produces its own light due to a reaction at its core. There are millions of stars.
On the other hand, a planet is a celestial body that has a fixed course, otherwise known as an orbit. The orbit is the pathway that allows the planet to move around a star. The biggest planet is Jupiter while the smallest is Mercury. There are eight planets in total with a few dwarf planets already discovered.
Finding the Differences
The first and most visible differences between the two can be seen by observing whether the body is twinkling. Stars are constantly twinkling and shimmering while planets do not. Observed through a telescope, stars appear to shake around the edges.
Observing the relative brightness is another technique that can be used to tell the two apart. Planets are typically brighter than stars. The reason for differing brightness is because starts reflect the light of the sun, which is close to the planets, while the stars emit their own light.
Regarding shape, stars appear as a dot while planets appear spherical. Generally, stars are also bigger than planets. Due to the nuclear reactions that produce thermal energy in the core of stars, stars are much hotter than planets.
Another visible difference is whether or not the body is moving. All celestial bodies move, this is a known fact. However, stars and planets move in differing manners. A planet moves across the night sky while observing the rules followed by the sun and the moon. Therefore, a celestial body appearing to move in a straight line is more likely going to be a planet. Stars move in a circular pattern. Sometimes one may mistake planes and satellites for either stars or planets, but these move faster.
Someone may also try a more advanced technique of identifying the ecliptic. The ecliptic is an imaginary band that planets move along. The difficulties in identifying the belt are clear to the untrained eye, but careful observation may be able to reveal the belt. However, stars may also be in the belt. Other techniques, like looking for twinkles, should then be used to identify the stars and the planets. Observation of the trajectory followed by the moon and sun is the easiest way to find the band since planets move close to the path.
Other methods include observation of the color of different bodies, using guides and charts from credible sources, using telescopes or binoculars, and visiting dark-sky places for improved visibility. While trying to observe the bodies, one should also make sure that factors that limit visibility are reduced.
About the Author
Ferdinand graduated in 2016 with a Bsc. Project Planning and Management. He enjoys writing about pretty much anything and has a soft spot for technology and advocating for world peace.
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NGC 4038 (on the center-left of the image, as well as its counterpart in this image, NGC 4039) has no less than eight different denominations. The most popular are NGC 4038 (9), Caldwell 60 (1), Arp 244 and The Antennae galaxies. They are a pair of interacting (colliding) spiral galaxies and the closest colliding pair to the Milky Way. This kind of galactic collisions usually triggers star birth. This is the reason for the strong blue hue on NGC 4038 (on the left). If some of the stars being generated are massive, their lifetime is short and they end up in colossal supernova explosions. In fact, five supernovae have been observed in these galaxies in the last 100 years. Another consequence of the collision is that huge numbers of globular clusters are generated. Although globular clusters are usually associated with old ages, the pressure of the colliding Interstellar Medium (ISM) accounts for the formation of large groups of close stars, originating star clusters.
Our milky Way and the Andromeda Galaxy (M31) also head on for a collision with each other in a few billion years. The appearance of this collision will, most probably, resemble the current Antennae galaxies.
Name(s): NGC 4038/4039. Caldwell 60+61. The Antennae
Type: Spiral Galaxies
RA: 12h 02m 45s
Dec: -18º 57’ 33”
Size (arcmin): 3.4×1.7
Distance: 45 Mly
Date: 2017-01-22 thru 2017-02-22
Location: iTelescope.net, SSO near Coonabarabran, NSW Australia
Size (arcmin): 35×34
Telescope: Planewave CDK 20” f/6.8
Camera: SBIG STX16803 (4096x4096pix)
Guiding: Astrodon MonsterMOAG off-axis guider
Total exposure: 10.5 hours (L: 16x900s; RGB: 11-8-7x900s)
Processing: CCDStack, Photoshop CC 2017 | 0.909075 | 3.533331 |
When is a central peak crater not a central peak crater?
When its found in Gale crater on Mars and called Mount Sharp instead.
Meteor impact craters often produce mountains or peaks in the middle of the crater, called central peak craters.
Science suggests that these central peaks were formed by melting of rock from the impact of the asteroid/meteor and then when the rock is rebounding it freezes in the shape of the central peak.
Not Gale central peak crater
Mars has lots of these central peak craters. Gale Crater also has a central peak but it seems less sharp than others or maybe due to another reason, so is called a mountain instead, Mount Sharp. It is over 3 miles tall.
But Mount Sharp is not the central peak of Gale Crater, although it is located in the center of the crater and looks like one. Mount Sharp was not formed by the rebounding theory.
Now scientists using the Mars Curiosity rover images have concluded that Mount Sharp was formed by sediment inside Gale Crater lake.
How was not central peak Sharp formed?
What depth did the Gale Crater lake have to be to form the 3 mile high Mount Sharp?
What sort of water erosion was happening around and in the lake to produce that much sediment?
Where is the evidence of the erosion from or around Gale Crater?
Where has all the water on Mars gone?
Will all other craters with central peaks have to be looked to see if they were formed by water erosion and sediment, especially if they are not exaggerated peaks?
Eu theory and central peak craters formation
Could craters and their central peaks be formed by spark erosion, Electric Discharge Machining or large plasma discharge events in an Electric Universe?
Everythings Electric forum links:
Gale Crater geology - crater and mountain formation
Mount Sharp (Aeolis Mons) formation - Gale Crater geology, Mars | 0.815261 | 3.404081 |
Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.
Nuclear fusion powers a star for most of its existence. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their existence, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.
Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.
Stellar evolution starts with the gravitational collapse of a giant molecular cloud. Typical giant molecular clouds are roughly 100 light-years (9.5×1014 km) across and contain up to 6,000,000 solar masses (1.2×1037 kg). As it collapses, a giant molecular cloud breaks into smaller and smaller pieces. In each of these fragments, the collapsing gas releases gravitational potential energy as heat. As its temperature and pressure increase, a fragment condenses into a rotating sphere of superhot gas known as a protostar.
A protostar continues to grow by accretion of gas and dust from the molecular cloud, becoming a pre-main-sequence star as it reaches its final mass. Further development is determined by its mass. Mass is typically compared to the mass of the Sun: 1.0 M☉ (2.0×1030 kg) means 1 solar mass.
Protostars are encompassed in dust, and are thus more readily visible at infrared wavelengths. Observations from the Wide-field Infrared Survey Explorer (WISE) have been especially important for unveiling numerous Galactic protostars and their parent star clusters.
Brown dwarfs and sub-stellar objects
Protostars with masses less than roughly 0.08 M☉ (1.6×1029 kg) never reach temperatures high enough for nuclear fusion of hydrogen to begin. These are known as brown dwarfs. The International Astronomical Union defines brown dwarfs as stars massive enough to fuse deuterium at some point in their lives (13 Jupiter masses (MJ), 2.5 × 1028 kg, or 0.0125 M☉). Objects smaller than 13 MJ are classified as sub-brown dwarfs (but if they orbit around another stellar object they are classified as planets). Both types, deuterium-burning and not, shine dimly and fade away slowly, cooling gradually over hundreds of millions of years.
For a more-massive protostar, the core temperature will eventually reach 10 million kelvin, initiating the proton–proton chain reaction and allowing hydrogen to fuse, first to deuterium and then to helium. In stars of slightly over 1 M☉ (2.0×1030 kg), the carbon–nitrogen–oxygen fusion reaction (CNO cycle) contributes a large portion of the energy generation. The onset of nuclear fusion leads relatively quickly to a hydrostatic equilibrium in which energy released by the core maintains a high gas pressure, balancing the weight of the star's matter and preventing further gravitational collapse. The star thus evolves rapidly to a stable state, beginning the main-sequence phase of its evolution.
A new star will sit at a specific point on the main sequence of the Hertzsprung–Russell diagram, with the main-sequence spectral type depending upon the mass of the star. Small, relatively cold, low-mass red dwarfs fuse hydrogen slowly and will remain on the main sequence for hundreds of billions of years or longer, whereas massive, hot O-type stars will leave the main sequence after just a few million years. A mid-sized yellow dwarf star, like the Sun, will remain on the main sequence for about 10 billion years. The Sun is thought to be in the middle of its main sequence lifespan.
Eventually the core exhausts its supply of hydrogen and the star begins to evolve off of the main sequence. Without the outward radiation pressure generated by the fusion of hydrogen to counteract the force of gravity the core contracts until either electron degeneracy pressure becomes sufficient to oppose gravity or the core becomes hot enough (around 100 MK) for helium fusion to begin. Which of these happens first depends upon the star's mass.
What happens after a low-mass star ceases to produce energy through fusion has not been directly observed; the universe is around 13.8 billion years old, which is less time (by several orders of magnitude, in some cases) than it takes for fusion to cease in such stars.
Recent astrophysical models suggest that red dwarfs of 0.1 M☉ may stay on the main sequence for some six to twelve trillion years, gradually increasing in both temperature and luminosity, and take several hundred billion years more to collapse, slowly, into a white dwarf. Such stars will not become red giants as the whole star is a convection zone and it will not develop a degenerate helium core with a shell burning hydrogen. Instead, hydrogen fusion will proceed until almost the whole star is helium.
Slightly more massive stars do expand into red giants, but their helium cores are not massive enough to reach the temperatures required for helium fusion so they never reach the tip of the red giant branch. When hydrogen shell burning finishes, these stars move directly off the red giant branch like a post-asymptotic-giant-branch (AGB) star, but at lower luminosity, to become a white dwarf. A star with an initial mass about 0.6 M☉ will be able to reach temperatures high enough to fuse helium, and these "mid-sized" stars go on to further stages of evolution beyond the red giant branch.
Stars of roughly 0.6–10 M☉ become red giants, which are large non-main-sequence stars of stellar classification K or M. Red giants lie along the right edge of the Hertzsprung–Russell diagram due to their red color and large luminosity. Examples include Aldebaran in the constellation Taurus and Arcturus in the constellation of Boötes.
Mid-sized stars are red giants during two different phases of their post-main-sequence evolution: red-giant-branch stars, with inert cores made of helium and hydrogen-burning shells, and asymptotic-giant-branch stars, with inert cores made of carbon and helium-burning shells inside the hydrogen-burning shells. Between these two phases, stars spend a period on the horizontal branch with a helium-fusing core. Many of these helium-fusing stars cluster towards the cool end of the horizontal branch as K-type giants and are referred to as red clump giants.
When a star exhausts the hydrogen in its core, it leaves the main sequence and begins to fuse hydrogen in a shell outside the core. The core increases in mass as the shell produces more helium. Depending on the mass of the helium core, this continues for several million to one or two billion years, with the star expanding and cooling at a similar or slightly lower luminosity to its main sequence state. Eventually either the core becomes degenerate, in stars around the mass of the sun, or the outer layers cool sufficiently to become opaque, in more massive stars. Either of these changes cause the hydrogen shell to increase in temperature and the luminosity of the star to increase, at which point the star expands onto the red giant branch.
The expanding outer layers of the star are convective, with the material being mixed by turbulence from near the fusing regions up to the surface of the star. For all but the lowest-mass stars, the fused material has remained deep in the stellar interior prior to this point, so the convecting envelope makes fusion products visible at the star's surface for the first time. At this stage of evolution, the results are subtle, with the largest effects, alterations to the isotopes of hydrogen and helium, being unobservable. The effects of the CNO cycle appear at the surface during the first dredge-up, with lower 12C/13C ratios and altered proportions of carbon and nitrogen. These are detectable with spectroscopy and have been measured for many evolved stars.
The helium core continues to grow on the red giant branch. It is no longer in thermal equilibrium, either degenerate or above the Schoenberg-Chandrasekhar limit, so it increases in temperature which causes the rate of fusion in the hydrogen shell to increase. The star increases in luminosity towards the tip of the red-giant branch. Red giant branch stars with a degenerate helium core all reach the tip with very similar core masses and very similar luminosities, although the more massive of the red giants become hot enough to ignite helium fusion before that point.
In the helium cores of stars in the 0.6 to 2.0 solar mass range, which are largely supported by electron degeneracy pressure, helium fusion will ignite on a timescale of days in a helium flash. In the nondegenerate cores of more massive stars, the ignition of helium fusion occurs relatively slowly with no flash. The nuclear power released during the helium flash is very large, on the order of 108 times the luminosity of the Sun for a few days and 1011 times the luminosity of the Sun (roughly the luminosity of the Milky Way Galaxy) for a few seconds. However, the energy is consumed by the thermal expansion of the initially degenerate core and thus cannot be seen from outside the star. Due to the expansion of the core, the hydrogen fusion in the overlying layers slows and total energy generation decreases. The star contracts, although not all the way to the main sequence, and it migrates to the horizontal branch on the Hertzsprung–Russell diagram, gradually shrinking in radius and increasing its surface temperature.
Core helium flash stars evolve to the red end of the horizontal branch but do not migrate to higher temperatures before they gain a degenerate carbon-oxygen core and start helium shell burning. These stars are often observed as a red clump of stars in the colour-magnitude diagram of a cluster, hotter and less luminous than the red giants. Higher-mass stars with larger helium cores move along the horizontal branch to higher temperatures, some becoming unstable pulsating stars in the yellow instability strip (RR Lyrae variables), whereas some become even hotter and can form a blue tail or blue hook to the horizontal branch. The morphology of the horizontal branch depends on parameters such as metallicity, age, and helium content, but the exact details are still being modelled.
After a star has consumed the helium at the core, hydrogen and helium fusion continues in shells around a hot core of carbon and oxygen. The star follows the asymptotic giant branch on the Hertzsprung–Russell diagram, paralleling the original red giant evolution, but with even faster energy generation (which lasts for a shorter time). Although helium is being burnt in a shell, the majority of the energy is produced by hydrogen burning in a shell further from the core of the star. Helium from these hydrogen burning shells drops towards the center of the star and periodically the energy output from the helium shell increases dramatically. This is known as a thermal pulse and they occur towards the end of the asymptotic-giant-branch phase, sometimes even into the post-asymptotic-giant-branch phase. Depending on mass and composition, there may be several to hundreds of thermal pulses.
There is a phase on the ascent of the asymptotic-giant-branch where a deep convective zone forms and can bring carbon from the core to the surface. This is known as the second dredge up, and in some stars there may even be a third dredge up. In this way a carbon star is formed, very cool and strongly reddened stars showing strong carbon lines in their spectra. A process known as hot bottom burning may convert carbon into oxygen and nitrogen before it can be dredged to the surface, and the interaction between these processes determines the observed luminosities and spectra of carbon stars in particular clusters.
Another well known class of asymptotic-giant-branch stars is the Mira variables, which pulsate with well-defined periods of tens to hundreds of days and large amplitudes up to about 10 magnitudes (in the visual, total luminosity changes by a much smaller amount). In more-massive stars the stars become more luminous and the pulsation period is longer, leading to enhanced mass loss, and the stars become heavily obscured at visual wavelengths. These stars can be observed as OH/IR stars, pulsating in the infra-red and showing OH maser activity. These stars are clearly oxygen rich, in contrast to the carbon stars, but both must be produced by dredge ups.
These mid-range stars ultimately reach the tip of the asymptotic-giant-branch and run out of fuel for shell burning. They are not sufficiently massive to start full-scale carbon fusion, so they contract again, going through a period of post-asymptotic-giant-branch superwind to produce a planetary nebula with an extremely hot central star. The central star then cools to a white dwarf. The expelled gas is relatively rich in heavy elements created within the star and may be particularly oxygen or carbon enriched, depending on the type of the star. The gas builds up in an expanding shell called a circumstellar envelope and cools as it moves away from the star, allowing dust particles and molecules to form. With the high infrared energy input from the central star, ideal conditions are formed in these circumstellar envelopes for maser excitation.
It is possible for thermal pulses to be produced once post-asymptotic-giant-branch evolution has begun, producing a variety of unusual and poorly understood stars known as born-again asymptotic-giant-branch stars. These may result in extreme horizontal-branch stars (subdwarf B stars), hydrogen deficient post-asymptotic-giant-branch stars, variable planetary nebula central stars, and R Coronae Borealis variables.
In massive stars, the core is already large enough at the onset of the hydrogen burning shell that helium ignition will occur before electron degeneracy pressure has a chance to become prevalent. Thus, when these stars expand and cool, they do not brighten as dramatically as lower-mass stars; however, they were more luminous on the main sequence and they evolve to highly luminous supergiants. Their cores become massive enough that they cannot support themselves by electron degeneracy and will eventually collapse to produce a neutron star or black hole.
Extremely massive stars (more than approximately 40 M☉), which are very luminous and thus have very rapid stellar winds, lose mass so rapidly due to radiation pressure that they tend to strip off their own envelopes before they can expand to become red supergiants, and thus retain extremely high surface temperatures (and blue-white color) from their main-sequence time onwards. The largest stars of the current generation are about 100-150 M☉ because the outer layers would be expelled by the extreme radiation. Although lower-mass stars normally do not burn off their outer layers so rapidly, they can likewise avoid becoming red giants or red supergiants if they are in binary systems close enough so that the companion star strips off the envelope as it expands, or if they rotate rapidly enough so that convection extends all the way from the core to the surface, resulting in the absence of a separate core and envelope due to thorough mixing.
The core of a massive star, defined as the region depleted of hydrogen, grows hotter and more dense as it accretes material from the fusion of hydrogen outside the core. In sufficiently massive stars, the core reaches temperatures and densities high enough to fuse carbon and heavier elements via the alpha process. At the end of helium fusion, the core of a star consists primarily of carbon and oxygen. In stars heavier than about 8 M☉, the carbon ignites and fuses to form neon, sodium, and magnesium. Stars somewhat less massive may partially ignite carbon, but are unable to fully fuse the carbon before electron degeneracy sets in, and these stars will eventually leave an oxygen-neon-magnesium white dwarf.
The exact mass limit for full carbon burning depends on several factors such as metallicity and the detailed mass lost on the asymptotic giant branch, but is approximately 8-9 M☉. After carbon burning is complete, the core of these stars reaches about 2.5 M☉ and becomes hot enough for heavier elements to fuse. Before oxygen starts to fuse, neon begins to capture electrons which triggers neon burning. For a range of stars of approximately 8-12 M☉, this process is unstable and creates runaway fusion resulting in an electron capture supernova.
In more massive stars, the fusion of neon proceeds without a runaway deflagration. This is followed in turn by complete oxygen burning and silicon burning, producing a core consisting largely of iron-peak elements. Surrounding the core are shells of lighter elements still undergoing fusion. The timescale for complete fusion of a carbon core to an iron core is so short, just a few hundred years, that the outer layers of the star are unable to react and the appearance of the star is largely unchanged. The iron core grows until it reaches an effective Chandrasekhar mass, higher than the formal Chandrasekhar mass due to various corrections for the relativistic effects, entropy, charge, and the surrounding envelope. The effective Chandrasekhar mass for an iron core varies from about 1.34 M☉ in the least massive red supergiants to more than 1.8 M☉ or more in more massive stars. Once this mass is reached, electrons begin to be captured into the iron-peak nuclei and the core becomes unable to support itself. The core collapses and the star is destroyed, either in a supernova or direct collapse to a black hole.
When the core of a massive star collapses, it will form a neutron star, or in the case of cores that exceed the Tolman-Oppenheimer-Volkoff limit, a black hole. Through a process that is not completely understood, some of the gravitational potential energy released by this core collapse is converted into a Type Ib, Type Ic, or Type II supernova. It is known that the core collapse produces a massive surge of neutrinos, as observed with supernova SN 1987A. The extremely energetic neutrinos fragment some nuclei; some of their energy is consumed in releasing nucleons, including neutrons, and some of their energy is transformed into heat and kinetic energy, thus augmenting the shock wave started by rebound of some of the infalling material from the collapse of the core. Electron capture in very dense parts of the infalling matter may produce additional neutrons. Because some of the rebounding matter is bombarded by the neutrons, some of its nuclei capture them, creating a spectrum of heavier-than-iron material including the radioactive elements up to (and likely beyond) uranium. Although non-exploding red giants can produce significant quantities of elements heavier than iron using neutrons released in side reactions of earlier nuclear reactions, the abundance of elements heavier than iron (and in particular, of certain isotopes of elements that have multiple stable or long-lived isotopes) produced in such reactions is quite different from that produced in a supernova. Neither abundance alone matches that found in the Solar System, so both supernovae and ejection of elements from red giants are required to explain the observed abundance of heavy elements and isotopes thereof.
The energy transferred from collapse of the core to rebounding material not only generates heavy elements, but provides for their acceleration well beyond escape velocity, thus causing a Type Ib, Type Ic, or Type II supernova. Current understanding of this energy transfer is still not satisfactory; although current computer models of Type Ib, Type Ic, and Type II supernovae account for part of the energy transfer, they are not able to account for enough energy transfer to produce the observed ejection of material. However, neutrino oscillations may play an important role in the energy transfer problem as they not only affect the energy available in a particular flavour of neutrinos but also through other general-relativistic effects on neutrinos.
Some evidence gained from analysis of the mass and orbital parameters of binary neutron stars (which require two such supernovae) hints that the collapse of an oxygen-neon-magnesium core may produce a supernova that differs observably (in ways other than size) from a supernova produced by the collapse of an iron core.
The most massive stars that exist today may be completely destroyed by a supernova with an energy greatly exceeding its gravitational binding energy. This rare event, caused by pair-instability, leaves behind no black hole remnant. In the past history of the universe, some stars were even larger than the largest that exists today, and they would immediately collapse into a black hole at the end of their lives, due to photodisintegration.
After a star has burned out its fuel supply, its remnants can take one of three forms, depending on the mass during its lifetime.
White and black dwarfs
For a star of 1 M☉, the resulting white dwarf is of about 0.6 M☉, compressed into approximately the volume of the Earth. White dwarfs are stable because the inward pull of gravity is balanced by the degeneracy pressure of the star's electrons, a consequence of the Pauli exclusion principle. Electron degeneracy pressure provides a rather soft limit against further compression; therefore, for a given chemical composition, white dwarfs of higher mass have a smaller volume. With no fuel left to burn, the star radiates its remaining heat into space for billions of years.
A white dwarf is very hot when it first forms, more than 100,000 K at the surface and even hotter in its interior. It is so hot that a lot of its energy is lost in the form of neutrinos for the first 10 million years of its existence, but will have lost most of its energy after a billion years.
The chemical composition of the white dwarf depends upon its mass. A star of a few solar masses will ignite carbon fusion to form magnesium, neon, and smaller amounts of other elements, resulting in a white dwarf composed chiefly of oxygen, neon, and magnesium, provided that it can lose enough mass to get below the Chandrasekhar limit (see below), and provided that the ignition of carbon is not so violent as to blow the star apart in a supernova. A star of mass on the order of magnitude of the Sun will be unable to ignite carbon fusion, and will produce a white dwarf composed chiefly of carbon and oxygen, and of mass too low to collapse unless matter is added to it later (see below). A star of less than about half the mass of the Sun will be unable to ignite helium fusion (as noted earlier), and will produce a white dwarf composed chiefly of helium.
In the end, all that remains is a cold dark mass sometimes called a black dwarf. However, the universe is not old enough for any black dwarfs to exist yet.
If the white dwarf's mass increases above the Chandrasekhar limit, which is 1.4 M☉ for a white dwarf composed chiefly of carbon, oxygen, neon, and/or magnesium, then electron degeneracy pressure fails due to electron capture and the star collapses. Depending upon the chemical composition and pre-collapse temperature in the center, this will lead either to collapse into a neutron star or runaway ignition of carbon and oxygen. Heavier elements favor continued core collapse, because they require a higher temperature to ignite, because electron capture onto these elements and their fusion products is easier; higher core temperatures favor runaway nuclear reaction, which halts core collapse and leads to a Type Ia supernova. These supernovae may be many times brighter than the Type II supernova marking the death of a massive star, even though the latter has the greater total energy release. This instability to collapse means that no white dwarf more massive than approximately 1.4 M☉ can exist (with a possible minor exception for very rapidly spinning white dwarfs, whose centrifugal force due to rotation partially counteracts the weight of their matter). Mass transfer in a binary system may cause an initially stable white dwarf to surpass the Chandrasekhar limit.
If a white dwarf forms a close binary system with another star, hydrogen from the larger companion may accrete around and onto a white dwarf until it gets hot enough to fuse in a runaway reaction at its surface, although the white dwarf remains below the Chandrasekhar limit. Such an explosion is termed a nova.
Ordinarily, atoms are mostly electron clouds by volume, with very compact nuclei at the center (proportionally, if atoms were the size of a football stadium, their nuclei would be the size of dust mites). When a stellar core collapses, the pressure causes electrons and protons to fuse by electron capture. Without electrons, which keep nuclei apart, the neutrons collapse into a dense ball (in some ways like a giant atomic nucleus), with a thin overlying layer of degenerate matter (chiefly iron unless matter of different composition is added later). The neutrons resist further compression by the Pauli exclusion principle, in a way analogous to electron degeneracy pressure, but stronger.
These stars, known as neutron stars, are extremely small—on the order of radius 10 km, no bigger than the size of a large city—and are phenomenally dense. Their period of rotation shortens dramatically as the stars shrink (due to conservation of angular momentum); observed rotational periods of neutron stars range from about 1.5 milliseconds (over 600 revolutions per second) to several seconds. When these rapidly rotating stars' magnetic poles are aligned with the Earth, we detect a pulse of radiation each revolution. Such neutron stars are called pulsars, and were the first neutron stars to be discovered. Though electromagnetic radiation detected from pulsars is most often in the form of radio waves, pulsars have also been detected at visible, X-ray, and gamma ray wavelengths.
If the mass of the stellar remnant is high enough, the neutron degeneracy pressure will be insufficient to prevent collapse below the Schwarzschild radius. The stellar remnant thus becomes a black hole. The mass at which this occurs is not known with certainty, but is currently estimated at between 2 and 3 M☉.
Black holes are predicted by the theory of general relativity. According to classical general relativity, no matter or information can flow from the interior of a black hole to an outside observer, although quantum effects may allow deviations from this strict rule. The existence of black holes in the universe is well supported, both theoretically and by astronomical observation.
Because the core-collapse mechanism of a supernova is, at present, only partially understood, it is still not known whether it is possible for a star to collapse directly to a black hole without producing a visible supernova, or whether some supernovae initially form unstable neutron stars which then collapse into black holes; the exact relation between the initial mass of the star and the final remnant is also not completely certain. Resolution of these uncertainties requires the analysis of more supernovae and supernova remnants.
A stellar evolutionary model is a mathematical model that can be used to compute the evolutionary phases of a star from its formation until it becomes a remnant. The mass and chemical composition of the star are used as the inputs, and the luminosity and surface temperature are the only constraints. The model formulae are based upon the physical understanding of the star, usually under the assumption of hydrostatic equilibrium. Extensive computer calculations are then run to determine the changing state of the star over time, yielding a table of data that can be used to determine the evolutionary track of the star across the Hertzsprung–Russell diagram, along with other evolving properties. Accurate models can be used to estimate the current age of a star by comparing its physical properties with those of stars along a matching evolutionary track.
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- MESA stellar evolution codes (Modules for Experiments in Stellar Astrophysics)
- "The Life of Stars", BBC Radio 4 discussion with Paul Murdin, Janna Levin and Phil Charles (In Our Time, Mar. 27, 2003) | 0.902605 | 4.151597 |
I understand that astronomers once thought that the material in the disc of a galaxy was moving around the galactic centre (where most of the mass was thought to be) in roughly circular orbits. The circular motions would be explained by the combination of inertia and gravitational acceleration towards the centre. This follows the Kepler/Newton model which describes/explains the orbits of planets around the Sun. In a Kepler/Newton system the tangential or transverse velocity of a low-mass orbitting object depends on the radial distance of the high-mass object from the centre. Objects further out must have lower velocities so that the weaker centrally-directed acceleration at that distance can keep the object moving in a roughly circular track.
In the centre of the galaxy the velocities are low and increase rapidly with distance away from the centre. This is understandable as the mass of the central bulge of the galaxy is not concentrated at the centre, it is spread out over a relatively large volume.
However it is now well-known that the measured velocities of visible material in the disks of discoidal galaxies do not vary as expected for a Kepler/Newton system. At a certain distance where the velocities would be expected to start decreasing (as per curve A) they either level out or continue increasing at a slow rate (as per curve B).
The current explanantion is that a large mass of Dark Matter extends throughout the galaxy in such a way as to produce non-Keplerian behavior.
But isn't there another possible explanantion of the non-Keplerian velocity profile namely that the ordinary detectable material (e.g. gas, dust, stars) in the disk is not completely gravitationally bound to the galactic centre and is actually gradually moving outwards along a spiral path? | 0.812951 | 3.796127 |
Jun 05, 2013
Structures on Mars that resemble Earth’s hydrothermal vents or eroded mounds have sparked renewed interest in water flowing over the Red Planet.
Mounds on Mars are thought to be the remains of ancient hydrothermal vents because they have a similar appearance to fossilized “mound springs” in the Australian Outback, so researchers theorize that both structures could be of similar origin.
Hydrothermal vents were a startling discovery for scientists when the first deep water exploration of the mid-ocean ridge was conducted. The surprise was not that the vents were spewing black, mineral-rich water at over 300 Celsius, but that there were colonies of living organisms surrounding them, thriving in a frigid environment a thousand meters or more beneath the sea.
Since conventional geological theories suggest that the ocean bottoms have changed places with the high places on Earth over millions of years, the formations that were once in the deep are now located on mountain tops or in torrid deserts. Formations like the Australian mounds are thought to be the remains of hydrothermal vents that were once active on the bottom of an ancient sea.
A few of the mound springs in Australia retain connections to underground water sources and continue to flow after millions of years. Some of them are nothing more than circular discolorations that identify striations composed of different chemical composition. According to the theory, hot mineralized water that once jetted out from the vent left ring-shaped cross-sections as the eruptions lost their geothermal energy and shut down after eons of existence. When the land and sea changed places, the fossilized vents relocated to the desert.
Modern science has retained the long-hoped-for desire that Mars could be the cradle of different life forms that arose and evolved in a separate ecology. As the overall theory goes, in order for what has become the subtext of nearly every presentation about Mars to exist, the planet must have gone through a stage when there were oceanic quantities of liquid water on the surface. This idea also implies that Mars once retained an atmosphere dense enough in oxygen (and a moderating gas) that life could respire in the open.
However, there is disagreement in the scientific community about whether such volumes of water could ever have existed on Mars. In the March 5, 2007 edition of Scientific American, it was reported that most of what has been interpreted as water-based erosion on Mars could have come from “dry avalanches” of dirt. The authors expressed serious doubts about whether observations have demonstrated any effects caused by liquid water.
Allan Treiman, a geologist from Houston’s Lunar and Planetary Institute wrote: “The idea of it being liquid water was a very reasonable hypothesis to start with. From my standpoint liquid water hasn’t been proved at all.”
Some features cannot be the result of water erosion. Since they’re found within the so-called “alluvial fans” that seem to indicate deposits left behind by deltas or other aquatic action, then the backbone of that theory has a serious flaw. Another often-overlooked aspect to what is happening on Mars is the electrical activity that can occur when dry mountains of dust move as a large mass.
The supposed water runoff from the rims of large craters or down the slopes of giant volcanoes is probably not the result of melting ice from beneath the surface dust but from falls of dust down slope. The blackened tracks left by such falls provide evidence for their electrical origin and not an aqueous one.
The large-scale structure of Mars, with its continent-wide canyon, gigantic volcanoes, thousand-kilometer-wide craters, fractures, plateaus and blasted wastelands of crushed stone was most likely created a relatively short time ago, as has been written for many years in these pages. Planetary scientists are beginning to see the signs of catastrophe on the small scale. Now, they must lift their eyes to the heights and consider the origin of what they see in the cliffs and ridges. | 0.839157 | 3.811123 |
The first magnifier constructed for scientific purposes is believed to have been designed by the English philosopher Roger Bacon (circa 1220-1292) sometime during the thirteenth century. Most magnifying glasses are double-convex lenses and are used to make objects appear larger. Today our magnification options are vast in both types of magnifiers and the rate in which they can enlarge an object. This blog will look at three basic options to include the monocular, binocular, and electronic magnifier.
Both binoculars and monoculars are intended for long-range observations. However, you will find a few differences while making use of each one. The biggest difference between a monocular and binoculars is how they look as well as how they are being used.
Two reasons you might choose a monocular over binoculars are cost and portability. When you compare a monocular with binoculars of the same specs, you will usually discover that monoculars are available at a generally lower price tag. Plus, since they are both lighter and smaller than binoculars, a monocular provides the benefit of being easier to carry around. While binoculars tend to come with a neck strap the monocular usually comes with a wrist strap. If you have arthritis or other conditions which hurt your hands or wrists, you may not want to wear a wrist strap. Even people with healthy wrists usually do not find a wrist strap as comfortable as a neck strap.
In terms of ease of use monoculars are straightforward. There are only one lens and one focus to adjust. That lets you work very quickly in most situations. Plus, since they do only have one lens, they are easier to maintain than binoculars.
Binocular Insight states that binoculars, also known as field glasses, are two telescopes which are usually mounted on a single frame aligned side-by-side. They provide magnification for distant objects. They are handheld devices with each telescope dedicated to one eye. Most binoculars come with a neck strap making them easier to carry around.
Focusing a pair of binoculars can take some practice but once figured out can be done quickly. The way binoculars are designed is so you can easily adjust the focus of the telescopes by using a one hand thumbwheel which is called the central focus adjustment. Once the central focus is adjusted, one of the two eyepieces can be further adjusted to compensate for differences between the viewer’s eyes. This is usually accomplished by rotating the eyepiece of each mount.
Unlike a monocular, binoculars can provide a three-dimensional image. Binoculars are designed to be used with or without glasses. Most manufacturers allow for corrective lens in their designs by adding extra focus ability or larger eye relief.
Nightskyinfo provides an in depth look at what the numbers on binoculars mean. All binoculars are described by using a pair of numbers, such as 7×50 or 8×30. The first number, including the x, represents magnification or “power”. This tells the degree to which the object observed is enlarged. For example, a 7x binocular makes an object appear seven times closer than when viewed by the naked eye.
The second number in the two-number code is aperture, the most important specification of binoculars if you plan to use them for astronomical observations. It represents the diameter of each of the objective lenses (the lenses furthest from your eye), given in millimeters. Therefore, 7×50 binoculars have objective lenses 50 mm in diameter. Aperture is so important because it determines the light gathering ability of your binoculars. Most celestial objects glow very dimly, so a large aperture becomes much more important in low light conditions. For example, 35 mm binoculars will do great when you watch a baseball game on a sunny day, but when used to observe the night sky you will find that they are pretty useless compared to typical 50 mm binoculars.
ILA’s featured binocular is the 2.8X Sports Spectacles.
The American Foundation for the Blind has a three-part series discussing electronic magnifiers. People with low vision have more choices than ever when it comes to magnification. You can choose from full-sized desktop electronic magnifiers (once called CCTVs), portable units that are small enough to fit in a laptop bag, and handhelds you can tuck into a pocket or purse.
Part 1: Identify Your Priorities: This article looks at such things as portability, features, and cost. You will learn how to ask the right questions, not just about products you’re considering, but about how you will use a magnifier in your daily life, at work, at school, at home, or on the go. In this first article, the focus is on you, the potential magnifier buyer, and how understanding your priorities is key to making a good purchase decision.
Part 2: Larger Magnifier Systems, Specs, and Features: This second article will take a deeper dive into the world of desktop and transportable magnifiers, explaining how their components work together, and guiding you through the most important specs and features.
Part 3: Handheld Magnifiers: Finally in this third article, the focus is on electronic magnifier products with the goal of helping you identify the features you need, and answering the question: given so many options, who needs a standalone electronic magnifier, anyway? If you are in the market for a handheld magnifier, ILA is currently featuring the Explore 8 Handheld Electronic Magnifier. | 0.809177 | 3.233062 |
The activity of comets – modelling the dusty-gas outflow from a nucleusKolloquium / Kongress / Forum Zielpublikum: Breite Öffentlichkeit
Comets are widely assumed to be debris from the formation of our Solar System and therefore attract considerable interest from scientists and space agencies. Spacecraft observations in the vicinity of an active comet always have limitations. To maximize our understanding, we need to produce a chain of models that allows us to compare, in a self-consistent way, the data from several different instruments. Only in this way can we use all the constraints on the large number of free parameters. The Planetary Imaging Group at the University of Bern has produced such a chain of models. This is showing us that, for example, dust and gas emission from the nightside of the nucleus (where there is no direct solar energy input that is supposed to drive the flow) is surprisingly strongly.
The presentation will discuss why researchers are particularly interested in comets, some of the modelling tools we use, and what we are learning from them.
Vortragende / Mitwirkende
Prof. Nicolas Thomas
Physics Institute, Space Research & Planetary Sciences
University of Bern | 0.896779 | 3.290879 |
The Moon observed by BepiColombo's MERTIS instrument during Earth flyby
The first ever measurements of the Moon's surface in the thermal infrared spectrum taken by the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) aboard the European/Japanese BepiColombo mission.
MERTIS, a novel instrument for studying the surface composition of celestial objects, obtained the measurements during BepiColombo's Earth flyby on 10 April 2020. Each image in this sequence represents one observation. The colourful band in the middle is the Moon's reflection in thermal infrared against the colder surrounding space. Since various minerals absorb and emit thermal infrared radiation differently, scientists can get a clear picture of the surface composition of the studied celestial bodies from MERTIS data.
MERTIS was designed specifically to study Mercury, the closest planet to the Sun with surface temperatures of over 400 °C. Seeing such a clear signature of the much colder surface of the Moon proved to the science teams that the instrument will be able to obtain even higher quality data than expected once at its destination
The observations were performed from the distance of 700 000 km, which is up to 2000 times farther away than will be the orbit of ESA's Mercury Planetary Orbiter (MPO), one of the two orbiters comprising the BepiColombo mission, which carries the MERTIS instrument.
Moreover, MERTIS made the measurements using its calibration port and not the main port, currently hidden behind the Mercury Transfer Module (MTM), which carries MPO and the Mercury Magnetospheric Orbiter of the Japanese Aerospace Exploration Agency (JAXA) to their destination. | 0.848433 | 3.580682 |
Super-Earth worlds are planets that are bigger than our Earth but smaller than Neptune. We don’t have such planets in the Solar System.
Aleksander Wolszczan and Dale Frail discovered the first super-Earth worlds, with masses about four times Earth, around a pulsar star (PSR B1257+12) in 1992.
Super-Earths are surprisingly abundant in our galaxy and stand as the most likely planets to be habitable.
Since 2009, the Kepler Space Telescope has discovered about 4,000 exoplanets. 30% of them are super-earths and a lot of them orbit within their star’s habitable zone.
You Might Like This: This is a Super-Earth Exoplanet
Scientists define super-Earths only by their masses and not by their temperatures, surface conditions, or habitability. A super-Earth is a planet with a mass between 1 and 10 times that of Earth. All that extra mass could make super-Earths the perfect home.
More mass means stronger gravity. Stronger gravity means the planet can hold on to more air molecules. Thus, forming a thicker atmosphere that can protect the world from harmful space radiation.
However, astronomers speculate that super-Earths may be more geologically active than our world, and may experience more vigorous plate tectonics due to thinner plates that are under more stress.
A super-Earth can be all sorts of things. It could be a bigger version of our own Earth – mostly rocky, with an atmosphere – or a mini-Neptune, with a large rock-ice core enclosed in a thick envelope of hydrogen and helium.
But it might also be a water world – a rocky core enveloped in a blanket of water and perhaps an atmosphere of steam (depending on the temperature of the planet).
If we were living on a super-Earth it would be harder for us to leave it and that’s because of the large size. That means a rocket would need more fuel to reach its destination. | 0.934999 | 3.447442 |
An easy trick to remember what moon phase the moon is in on any given night is the mnemonic DOC. DOC, (or COD if you’re in the southern hemisphere), reflects the amount of the moon illuminated, which you can use to discern the current phase the moon is in.
DOC represents the half-moon, the full moon, and the crescent moon, and whether or not the moon is waxing or waning.
“The moon does not simply disappear when we are not looking at it.” — Albert Einstein
Defining The Phases Of The Moon
Phases Of The Moon:
- New Moon
- Waxing Crescent
- First Quarter
- Waxing Gibbous
- Full Moon
- Waning Gibbous
- Last Quarter
- Waning Crescent
Though it’s often thought that the phases of the moon are caused by the Earth’s shadow being cast on the surface of the moon, this actually doesn’t happen very often and is known as lunar eclipse when it does. The phases of the moon are actually caused by shifts in the moon’s position relative to the sun. When part of the moon appears dark, this is because this portion of the moon is turned away from the sun. At least half of the moon is always in shadow, and half is illuminated. Yet because the moon always faces the Earth the same way (this is called being tidally locked), we perceive the shift in illumination as changing phases.
A New Moon occurs when the side of the moon that isn’t illuminated faces the Earth. No part of the moon is lit up, and as such, it isn’t visible at all, unless a solar eclipse is happening.
The moon is said to be “waxing” when more of its surface is being illuminated. As such, a waxing crescent moon is when the moon is only partially illuminated by the sun. A crescent moon means that less then half the moon illuminated, so it’s between 1% to 49% illuminated.
A First Quarter moon is when one half of the moon’s visible surface is illuminated. The First Quarter happens during the waxing period when the percentage of the moon’s surface that is illuminated is increasing.
A Waxing Gibbous moon is when the visible surface of the moon is more than half illuminated, but not fully illuminated. When the portion of the moon illuminated is between 51% to 99%, and the percentage of the illuminated moon is increasing, it’s a Waxing Gibbous moon.
The Full Moon happens when the illuminated portion of the moon is directly facing the Earth, and as such the entire disc of the moon appears to be lit up.
A Waning Gibbous Moon occurs when more than one half, yet less than the whole moon’s visible surface, is illuminated by the sun. The percentage of the moon’s illuminated surface is decreasing during this time and is between 99% to 51%.
The Last Quarter Moon occurs when only one half of the moon is illuminated by the sun, and when the amount of illuminated surface is decreasing.
A Waning Crescent moon occurs when there’s less than one-half of the moon illuminated, and when the percentage of the moon illuminated is decreasing. The percentage of the moon illuminated during a waning crescent is between 49% to 0%.
The cycle then resets with the New Moon. The cycle takes about 29.5 days to complete or to reach the same visual phase. Meanwhile, it takes the moon around 27.4 days to revolve around the Earth. These two different lunar months are referred to as the synodic month and the sidereal month respectively. A lunation is a complete cycle of lunar phases.
Due to the fact that the amount of time it takes the moon to complete a cycle is shorter than most months of the year, the phase the moon is in at the beginning of the month often repeats itself at the month’s end. If there are two full moons in a month, it’s called a Blue Moon.
Using The DOC Mnemonic
The DOC mnemonic is a handy tool for remembering which part of the moon is light up, and hence which part of the cycle the moon is currently in.
The “D” manifests itself on the moon as a lit-up arch on the right side of the moon, with a straight line down the moon’s center, where it transitions into darkness. If the illuminated portion of the moon makes a D, then the lunar cycle is just starting (D is the first letter in DOC). While half the moon will be illuminated twice during a full cycle of moon phases, only when the moon is waxing will it resemble a letter D, with the illuminated portion on the right-hand side.
“The moon is a friend for the lonesome to talk to.” — Carl Sandburg
The letter “O” in DOC is representative of the full moon, naturally. You may be able to guess that the “C” in DOC represents the crescent moon. Remember that although the moon adopts a crescent shape at two points in the cycle, only the waning crescent moon (coming at the end of DOC) will resemble a letter C. If the crescent moon resembles a C, a new moon will soon arrive.
Remember that if you’re in the southern hemisphere, you’ll want to reverse the mnemonic device and use COD instead.
Moon Phases And The Tides
You should also know that the phases of the moon are somewhat correlated with the intensity of the tides. Tides are at their most extreme during new moons and full moons. During these two time periods, the normal tides will become more severe, creating very high tides and very low tides. This is because when the moon is full, the moon and sun are pretty much in straight lines on either side of the Earth. The combined gravitational forces of the Sun and Moon create slightly larger tidal bulges than normal. The Sun and Moon are in a straight line on the same side of the planet at the New Moon, also cresting larger tidal bulges.
“Do not swear by the moon, for she changes constantly. Then your love would also change.” — William Shakespeare
By contrast, the tides of the Earth are at their least extreme when the moon is at one of the two-quarter phases. This is because it is essentially creating a 90-degree angle with the Sun, and the gravitational forces from the Sun and Moon are diminished since they are acting at perpendicular angles. | 0.823731 | 3.813718 |
Could life exist on a planet orbiting a supermassive black hole? And if so what would existence on such a planet be like?
Jeremy Schnittman, an astrophysicist at the NASA Goddard Space Flight Center in Greenbelt, Maryland, has been exploring the intriguing scenario. He has subsequently shed light on the bizarre possibility of a habitable planet orbiting a black hole in a magazine article released in the MIT Technology Review.
Time Slows Down
According to the ground-breaking sci-fi movie Interstellar, whose scientific advisor was the Nobel Prize–winning physicist Kip Thorne, the space-time surrounding such a planet would be warped in line with Einstein’s theory of general relativity. Consequently, time would pass at a slowed-down rate for those on the planet compared to elsewhere in the universe.
In Interstellar, for instance, astronauts returning from their visit to Miller’s planet orbiting the supermassive black hole called Gargantuan had experienced time at a rate of several years to every hour they spent on the planet.
One of the thought experiments that Schnittman conducted in his study involved contemplating the kind of light and temperatures that would exist on the planet in order to make it habitable for life. Of course, any planet around a black hole would have to receive its light from a source other than a star. Instead, the planet would likely be bathed in light emanating from the black hole’s accretion disks, or hot halos of gas and matter that collect around and fall into such supermassive objects in space. This blue-shifting of light would also make the planet hotter, helping to provide the sort of temperatures that would allow for the presence of liquid and not frozen water, which is one of the fundamental conditions necessary for life.
In other words, the same gravitational force that slows down time on such a planet would also cause the light it receives to shift to higher energies. This “blueshift” effect would potentially result in incoming light being amplified to higher frequencies, including in the UV range, with exposure to such high-energy radiation posing a threat to the living cells of an organism by damaging their DNA. As Schnittman explains:
“Time really affects everything around us. Not just our perception of reality, if you will, but it actually changes the reality, changes the blueshift. It can really make everything very, very different when time is running at a different rate.”
High Radiation from UV Light, X-Rays & Neutrinos
Furthermore, Schnittman raises a number of other factors that would ultimately make the possibility of a habitable planet near to a supermassive black hole even less likely. For instance, supermassive black holes are generally found at the center of galaxies, a region of space where the density of stars is extremely high. A planet circling the supermassive black hole at the center of our galaxy would have a night sky at least 100,000 times brighter than on Earth, meaning you could read at night without the use of electricity. It would also result in significantly higher amounts of background UV light and X-rays, which would produce strong harmful radiation to living creatures.
In addition, supermassive black holes are believed to create highly energetic particles known as neutrinos. These subatomic particle have very little interaction with matter and just pass through living tissue. In sufficient quantities, however, they can be harmful to life, for example in the eventuality of living organisms being unfortunate enough to be located sufficiently close to a supernova when the explosion took place. In the case of our theoretical planet close to a supermassive black hole, the volume of neutrinos emanating from the star clusters near a black hole would also be sufficient to radioactively heat up the planet and its core, eventually leading to it becoming unbearably hot.
Suffice to say, a planet orbiting a supermassive black hole would not be very conducive to the development of complex life and, as Schnittman concludes, the possibility of life surviving on such a planet was ultimately pretty unlikely indeed. | 0.844066 | 3.970452 |
Monster black holes shooting jets of gamma-ray radiation right at us have been spotted farther away than ever before, dating back to when the universe was nearly one-tenth its current age.
The five distant objects, called gamma-ray blazars, deepen the mystery of how black holes so large could have formed so early in the universe's history.
Roopesh Ojha, an astronomer at NASA's Goddard Space Flight Center in Maryland, presented the new results during a press conference today (Jan. 30) at the American Physical Society meeting in Washington, D.C. The results will also be published in The Astrophysical Journal Supplement. [Found: Gamma-Ray Blazars Powered by 'Supersized' Black Holes (Video)]
"The light we observed from these five objects left when the universe was just somewhere between 1.9 to 1.4 billion years old," Ojha said. Based on the data, "you arrive at the conclusion that they're all home to really, really massive black holes. Two of them are so big that their black holes may be well over 1 billion solar masses."
The supermassive black hole at the center of our galaxy, in contrast, has a mass of between 4 and 5 million times the sun's.
A blazar is a class of active galactic nuclei — a supermassive black hole at the center of a galaxy with a large disk of material whirling around it (outside the black hole's point of no return), generating radiation that blasts out in hyperfast jets. Blazars are the most active, from Earth's perspective, because the jets of material are speeding right toward us at near the speed of light. The new study looked at a particular type of blazar that's even more active than usual, Ojha said — and those blazars tend to spark from incredibly massive black holes, even compared to other galactic cores.
Before these five blazars were detected, the most distant blazar that had been seen emitted its light when the universe was close to 2.1 billion years old. The team, led by two researchers at Clemson University in South Carolina, was able to find blazars even more distant because of a significant processing software update to the orbiting Fermi Gamma-ray Space Telescope's Large Area Telescope, which increased its sensitivity by about 40 percent, particularly at lower frequencies, Ojha said.
The five newfound blazars are only a few of the many similarly powerful objects that must have existed that early in the universe's history — after all, we only detected the ones whose fierce jets are pointed directly at us.
"For a typical value of one of these objects, for the one object you see, there's something closer to 600 that you don't see," Ojha said. And that further emphasizes a major question about the early universe: How did black holes so large form so quickly?
"We've probably just made this problem a little bit more difficult by finding objects that are so massive," Ojha said. | 0.844902 | 3.959132 |
e (epsilon) - Perseid meteor shower active, from 5th to 21st, producing peak rate of meteors on 9th /10th (figure 1a & b). The radiant is circumpolar, meaning it is always above the horizon and the shower will be active throughout the night. The radiant of the shower will appear at a peak altitude of 78° above the horizon, and on the basis of this, you may see up to 4/5 meteors per hour at the peak (00:00 – 05:00 BST).
Over this period, there will be a chance of seeing September ε-Perseid meteors whenever the shower's radiant point in the constellation Perseus (figure 1c) is above the horizon, with the number of visible meteors increasing the higher the radiant point is in the sky.
Figure 1(a): Perseid meteor shower.
Figure 1 (b): Perseid meteor shower. Credit: Dhilung Kirat/Flickr.
Figure 1(c): Perseus constellation.
Full Moon (figure 2) will occur on 14th. Nights following 14th, it will rise approximately 1 hour later each day, becoming prominent later in the night. Within a few days, it will only be visible in the pre-dawn and early morning sky. As it reaches last quarter, a week after full moon, it will rise at midnight and set around noon.
The exact moment the Moon reaches full phase, it will lie in the constellation Aquarius (figure 3) and appear high in the sky at all but the most extreme latitudes. It will be visible at all latitudes between 72°N and 87°S. Distance from Earth will be 406,000 km.
Figure 2: Full Moon.
Figure 3: Constellation Aquarius.
22nd Moon at last quarter (figure 4), visible in the dawn sky, rising at 22:55 (BST) and reaching an altitude of 59° above Southern horizon before fading from view as dawn breaks around 06:38. This is the point of the Moon parading the Sun on the final arc of the lunar process. At this point the Moon appears half illuminated. The Moon takes on the shape of a pie sliced in half.
Figure 4: Moon at last quarter.
23rd is September equinox (figure 5) marking first day of autumn for the Northern hemisphere. On the day of the equinox, everywhere on Earth has almost exactly 12 hours of day and night, as the Sun's annual journey through the constellations of the zodiac carries it across the celestial equator. The word equinox derived from Latin words aequus (equal) and nox (night).
Wherever you are on Earth at the Equinox the Sun will rise from the point on the horizon which lies Due East and sets beneath the point which lies Due West.
Figure 5: Autumn Equinox.
WARNING: Never attempt to view through binoculars, telescope or any optical aid an object close to the Sun. Also, never attempt to view the Sun unaided, doing so may result in immediate and permanent blindness. Always use astronomical approved viewing equipment.
The Stellarium software will assist greatly in locating objects in the sky.
Nuclear Fusion & Astrophysics. | 0.872086 | 3.695859 |
Mercury May Be Meteor Like
Geologists at MIT have traced part of Mercury’s cooling history and based on their findings have determined that the planet likely has the composition of a meteorite.
Cecil and Ida Green Professor of Geology in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, Timothy Grove says this new information on Mercury’s past is of interest for tracing Earth’s early formation.
The team utilized data collected by NASA’s MESSENGER spacecraft, (The MErcury Surface, Space ENvironment, GEochemistry, and Ranging probe) which orbited Mercury between 2011 and 2015, and collected measurements of the planet’s chemical composition with each flyby.
“It’s true of all planets that different age terrains have different chemical compositions because things are changing inside the planet,” Grove says. “Why are they so different? That’s what we’re trying to figure out.”
In an effort to answer that question, Grove started by recreating Mercury’s lava deposits in the lab using MESSENGER’s 5,800 compositional data points, and selected two extremes: one representing the older lava deposits and one from the younger deposits.
The team found a surprising disparity in the two samples: The older rock melted deeper in the planet, at 360 kilometers, and at higher temperatures of 1,650 C, while the younger rock melted at shallower depths, at 160 kilometers, and 1,410 C. The experiments indicate that the planet’s interior cooled dramatically, over 240 degrees Celsius between 4.2 and 3.7 billion years ago—a geologically short span of 500 million years.
“Mercury has had a huge variation in temperature over a fairly short period of time, that records a really amazing melting process” Grove says. “We now know something like an enstatite chondrite was the starting material for Mercury, which is surprising, because they are about 10 standard deviations away from all other chondrites.”
Grove concluded by saying “The next thing that would really help us move our understanding of Mercury way forward is to actually have a meteorite from Mercury that we could study. That would be lovely.”
Grove and his colleagues, including researchers from the University of Hanover, in Germany; the University of Liége, in Belgium; and the University of Bayreuth, in Germany, have published their results in Earth and Planetary Science Letters. | 0.89092 | 3.580585 |
Get your telescopes ready and keep your eyes peeled on the skies, as the Lyrid meteor shower is expected to take place over the next few days.
Every year our skies are lit up by returning meteor showers, from Geminids and Quadrantids, to Draconids and Perseids. If the weather conditions are in our favour and the Moon isn't too bright, it's possible to see some spectacular shooting stars in action.
But when, where and how can you see the meteor showers of 2020? We've compiled a complete guide to the magnificent, must-see sights, which have left mankind awestruck for centuries.
From the science behind meteor showers to the best stargazing spots, here is everything you need to know.
What exactly is a meteor shower?
A meteor shower occurs when Earth passes through the debris stream occupying the orbit of a comet - or, in simpler terms, when a number of meteors flash across the sky from roughly the same point.
Meteors are sometimes called shooting stars, although they actually have nothing to do with stars.
Perspective makes meteor showers appear to emanate from a single point in the sky known as the shower radiant. A typical meteor results from a particle the size of a grain of sand vaporising in Earth’s atmosphere when it enters at 134,000mph.
Something larger than a grape will produce a fireball and this is often accompanied by a persistent afterglow known as a meteor train. This is a column of ionised gas slowly fading from view as it loses energy.
Meteor, meteorid or meteroite?
Let's get this straight. A meteor is a meteoroid – or a particle broken off an asteroid or comet orbiting the Sun – that burns up as it enters the Earth's atmosphere creating the effect of a "shooting star".
Meteoroids that reach the Earth's surface without disintegrating are called meteorites.
Meteors are mostly pieces of comet dust and ice no larger than a grain of rice. Meteorites are principally rocks broken off asteroids in the asteroid belt between Mars and Jupiter and can weigh as much as 60 tonnes.
They can be "stony", made up of minerals rich in silicon and oxygen, "iron", consisting mainly of iron and nickel, or "stony-iron", a combination of the two.
Scientists think about 1,000 tons to more than 10,000 tons of material from meteors falls on Earth each day, but it's mostly dust-like grains, according to Nasa, and they pose no threat to Earth.
There are only two incidents recorded where people reported being injured by a meteorite, including one in 1954 when a woman was bruised by a meteorite weighing eight pounds after it fell through her roof.
The Lyrid meteor shower
The Lyrid meteor shower takes place annually between April 16 and April 25 and in 2020, it peaked late on the 21st and in the early hours of the 22nd.
This particular shower is visible in both the Northern and Southern Hemispheres, offering stargazers a chance to see up to 18 meteors per hour during its peak.
Lyrid meteors are typically as bright as the stars in the Big Dipper, but some are much more intense, even brighter than Venus, the brightest object in the night sky after the moon.
Called "Lyrid fireballs", these cast shadows for a split second and leave behind smokey debris trails that linger for minutes.
What causes the Lyrid meteor shower?
The ionised gas in the meteors' trail burns up as it enters the Earth's atmosphere, creating the glow which can be seen streaking across the night sky.
The shower occurs as the Earth passes through the dust left over from Comet Thatcher (C/186 G1), which makes a full orbit of the sun once every 415 years (which is why there are no photographs of it).
Flakes of comet dust, most no bigger than grains of sand, strike Earth's atmosphere travelling 49 km/s (110,000 mph) and disintegrate as streaks of light.
Comet Thatcher last visited the inner solar system in 1861 - before the widespread use of photography - and isn’t expected to return until the year 2276.
How did the Lyrids get its name?
The shower radiates out from the direction of the star Vega, the brightest light in the constellation Lyra the Harp, from which it takes its name.
Vega is a brilliant blue-white star about three times wider than our Sun and 25 light years away.
You might remember Vega being mentioned in Carl Sagan's movie Contact - it was the source of alien radio transmissions to Earth.
When were the Lyrids first observed and recorded?
The earliest sightings of the Lyrid meteor shower go back 2,700 years and are among the oldest of known meteor showers.
In the year 687 BC the ancient Chinese observed the meteors and recorded them in the ancient Zuo Zhan chronicles saying:
"On the 4th month in the summer in the year of xīn-mǎo (of year 7 of King Zhuang of Lu), at night, (the sky is so bright that some) fixed stars become invisible (because of the meteor shower); at midnight, stars fell like rain.
That era of Chinese history corresponds with what is now called the Spring and Autumn Period (about 771 to 476 BC).
Tradition associates this period with the Chinese teacher and philosopher Confucius, one of the first to espouse the principle: “Do not do to others what you do not want done to yourself.”
American observers saw an outburst of nearly 100 Lyrid meteors per hour in 1982. Around 100 meteors per hour were seen in Greece in 1922 and from Japan in 1945.
The other major meteor showers of 2020
The Perseid meteor shower
The window for the Perseid meteor shower each year is from July 17 to August 24. As one of the brighter showers of the year, stargazers stand a chance of seeing meteors at any point in this window, however the peak typically occurs between August 12 and 13.
The shower appears to originate from within the star constellation Perseus – hence the shower's name. It occurs when Earth passes through the debris stream occupying the orbit of the comet Swift-Tuttle.
The wonderfully named comet is the largest object known to repeatedly pass Earth (it's 16 miles wide). It orbits the sun ever 133 years and each time it passes through the inner solar system it warms up, releasing fresh comet material into its orbital stream.
The last time it was closest to the sun was in December 1992. It will be back again in July 2126.
Peak rates of 150-200 meteors per hour were recorded in 2016, but typical rates are about 80 meteors an hour streaking across the night sky, each leaving a trail. During the 2020 peak, space fans will have the chance to see up to 150 meteors per hour.
To see the Perseid meteor shower in its full glory, look at a height approximately two-thirds up the sky in any direction. If you want a recommendation, east through south offers some great background constellations in the early hours during August. Look for the shower's "radiant" from the north-east corner of Perseus.
Draconid meteor shower
The Draconid meteor shower only graces our skies during a short window every year, from October 6 to 10, peaking on the night of October 8 and 9 in the UK.
The Draconids are considered among astronomers to be among the least exciting meteor showers - but that doesn't mean the shooting stars aren't worth looking out for.
Otherwise known as the Giacobinids, they are created as Earth passes through the debris left by the 21 P/ Giacobini-Zinner comet, which the comet takes about 6.6 years to make a single revolution around the Sun.
The shower comes from the constellation Draco the Dragon, which is where its name originates. For the best chance to see the shower, which is most easily visible in the northern hemisphere, look for the constellation's brightest stars, Eltanin and Rastaban.
While it is best to view most meteor showers when the sky is at its darkest, astronomers advise stargazers look out for the Draconids at dusk. The shower's radiant point, which is where the shower is known to originate from, is at its highest point just before nightfall.
Orionid meteor shower
The Orionid meteors appear every year between October 2 and November 7. While meteors can be seen throughout the shower's window, the best time to see them is from October 20 to 21, when the shower is at its brightest.
Tom Kerss, an astronomer at the Royal Observatory Greenwich said: "If you can brave the cold, make a plan to stay out and enjoy the thrill of seeing tiny flecks of Halley's Comet disintegrate at hypersonic speeds above your head."
He advises finding a secluded spot and allowing the eyes to adjust to the darkness.
Mr Kerss said: "There's no advantage to using binoculars or a telescope, your eyes are the best tool available for spotting meteors, so relax and gaze up at the sky, and eventually your patience will be rewarded.
"Meteors can appear anywhere in the sky, though if you have to pick a direction, you might fare slightly better looking east."
The meteoroids from Halley's Comet strike Earth's atmosphere at a speed of 148,000mph, (238,000kph) burning up in streaking flashes of light that can be seen with the naked eye.
Orionid meteors are known for their speed and brilliance, so if you persevere there's a good chance you'll see several bright 'shooting stars' zipping across the sky.
Why is it called Orionid?
It's named Orionid because it appears to radiate from the constellation Orion. Orion is one of the brightest and best known constellations and contains two of the 10 brightest stars in the sky Rigel and Betelgeuse, as well as the famous Orion's Belt.
Orion's Belt is made up of three bright stars quite close together almost in a straight line, and is about 1,500 light years from us on Earth.
Orion has been known since ancient times and is also referred to as Hunter thanks to Greek mythology. He is often seen in star maps facing Taurus, the bull.
The Geminid meteor shower
The Geminid meteor shower can be seen from around December 7th to 16th in 2020, with peak activity set to take place on December 13th and 14th.
Caused by the 3200 Phaethon asteroid, the Geminids' orbit brings it very close to the Sun, resulting in its surface material crumbling and breaking off. The Earth passes through this space debris every December, which burns up as it hits our atmosphere. These are the meteors visible in our sky.
The Geminids were first observed relatively recently, in 1862, compared with the Perseids (36AD) and the Leonids (902AD).
The meteor shower appears to come from a point in the constellation Gemini, hence its name.
How to spot the Geminids in 2020
Sightings are possible around the world, but there's good news for Britons: the shower favours observers in the Northern Hemisphere over those in the Southern.
You can spot the meteors anywhere, but they will appear to come from the Gemini constellation.
During December, it begins in the evening in the east and moves across the sky to the west during the night. Find Orion's Belt - three bright stars positioned in a row - and then look above it and a little to the left.
They will appear as streaks of light, and will sometimes arrive in bursts of two or three. They vary in colour, depending on their composition.
Up to 120 meteors an hour - or two a minute - can be expected, or more during the peak.
The Quadrantid meteor shower
The Quadrantid meteor shower was the first major meteor shower of 2020. It took place from December 28 to January 12, and peaked on the night of January 3 and early hours of January 4.
Unlike other meteor showers, which tend to peak for approximately two days, the Quadrantid meteor shower typically peaks for a few hours.
First spotted in 1825 by the Italian astronomer Antonio Brucalassi, astronomers suspect the shower originates from the comet C/1490 Y1, which was first observed 500 years ago by Japanese, Chinese and Korean astronomers.
Why is it called Quadrantid?
The Quadrantids appear to radiate from the extinct constellation Quadrans Muralis, which is now part of the Boötes constellation and not far from the Big Dipper.
Because of the constellation's position in the sky, the shower is often impossible to see in the Southern Hemisphere - however there is a chance of spotting it up to 51 degrees south latitude.
The best spots to see the display are in countries with high northern latitudes, like Norway, Sweden, Canada and Finland.
The best stargazing spots in the UK
A dark night is best for a meteor shower, after midnight and before dawn.
Head somewhere away from the bright lights - into more rural areas if you can - and be prepared to wait a good hour if you want the best chance of seeing a shower. Look for a wide, open viewing area - perhaps a national park or large field on the side of a road - and make sure you concentrate you gaze towards the east.
Meteor showers are unpredictable though, so prepare for the fact you might not see much.
Choose a dark location away from stray lights and give yourself at least 20 minutes in total darkness to properly adapt.
Britain has some wonderful stargazing locations, including three "Dark Sky Reserves" (Snowdonia, Brecon Beacons and Exmoor national parks) and Europe's largest "Dark Sky Park" (Northumberland National Park and the adjoining Kielder Water and Forest Park).
- Galloway Forest Park: Galloway is a couple of hours from Glasgow and an hour from Carlisle. The park's most popular spot for stargazing is Loch Trool.
- Exmoor and around: Exmoor was granted International Dark-Sky Reserve status by the International Dark-Sky Association in 2011. Light pollution is managed to make the area more appealing to amateur astronomers.
- Romney Marsh: Night once provided cover for smugglers known as Owlers, but today Romney Marsh offers celestial bounty, arching over a landscape adorned with the spires of ancient churches.
- Kielder: Kielder Forest is officially the darkest place in England – 250 square miles of wooded beauty where Northumberland brushes against Scotland. It has its own fabulous, modern, wood-clad observatory on the slopes of Black Fell above Kielder Water.
- North York Moors: As well as stunning night skies, the North York Moors boast historic market towns such as Helmsley and Pickering, plus appealing coastal spots, including Scarborough and Whitby. | 0.829238 | 3.877163 |
WASHINGTON (NNS) -- A U.S. Naval Research Laboratory-built camera mounted on the NASA Parker Solar Probe revealed an asteroid dust trail that has eluded astronomers for decades.
Karl Battams, a computational scientist in NRL’s Space Science Division, discussed the results from the camera called Wide-Field Imager for Solar Probe (WISPR) on Dec. 11 during a NASA press conference.
WISPR enabled researchers to identify the dust cloud trailing the orbit of the asteroid 3200 Phaethon.
“This is why NRL’s heliospheric imagers are so ground-breaking,” Battams said. “They allow you to see near-Sun outflows massively fainter than the Sun itself, which would otherwise blind our cameras. And in this case, you can also see solar system objects extremely close to the Sun, which most telescopes cannot do.”
He said the trail is best seen near the Sun where 3200 Phaethon’s dust is more densely packed, making WISPR a vital tool for scientists.
The data captured by WISPR determined the asteroid dust trail weighs an estimated billion tons, and measures more than 14 million miles long. The findings raise questions about the trail’s origin.
“Something catastrophic happened to Phaethon a couple of thousand years ago and created the Geminid Meteor shower,” Battams said. “There’s no way the asteroid is anywhere near active enough when it is near the Sun to produce the mass of dust we are seeing, so we are confident that WISPR is seeing part of the Geminid meteor stream.”
WISPR, designed, developed and led by NRL, records visible-light images of the solar corona and solar outflow in two overlapping cameras, which together cover more than 100-degrees angular width from the Sun.
Understanding how the solar environment behaves is important to the Navy and Marine Corps because when the solar winds reach Earth, they can affect GPS, spacecraft operations, and ground-based power grids.
WISPR and the Parker Solar Probe will continue to orbit the Sun for the next five years.
About the U.S. Naval Research Laboratory
NRL is a scientific and engineering command dedicated to research that drives innovative advances for the Navy and Marine Corps from the seafloor to space and in the information domain. NRL headquarters is located in Washington, D.C., with major field sites in Stennis Space Center, Mississippi, Key West, Florida, and Monterey, California, and employs approximately 2,500 civilian scientists, engineers and support personnel.
For more news from U.S. Naval Research Laboratory, visit www.navy.mil/local/nrl/. | 0.875429 | 3.407759 |
What Geologic Activity Does Uranus Have?
Uranus is one of two ice-giant planets in the solar system. Like Neptune, the other ice giant, it is sometimes also called a gas giant. Information about Uranus comes mostly from data gathered by NASA’s Voyager 2 spacecraft, which approached within 80,000 kilometers (50,000 miles) of the planet’s surface. Uranus does not display the type of geological activity associated with terrestrial planets such as Earth and Mars. The rings and moons of Uranus, however, do exhibit recognizable geological features.
Scientists report that between 80 percent and 85 percent of Uranus consist if an ice and rock mass. The ices are mostly frozen water, ammonia and methane around a liquid core. An envelope of hydrogen and helium, with traces of methane and ammonia, forms the planets’ atmosphere. Extreme temperatures and pressures in the planet’s interior could convert the carbon content of methane into diamond. According to space researchers Mona Delitsky, from California Specialty Engineering and Kevin Baines from the University of Wisconsin, Madison, the temperature at Uranus’ core could be 5,727 degrees Celsius (10,340 degrees Fahrenheit). This temperature could produce diamonds the size of a hand that precipitate from the liquid.
Thirteen rings have been identified around Uranus. These consist of a combination of ice and rock and are replenished with dust from meteor impacts -- also called space weathering -- on Mab, one of Uranus’ small outer moons. Some could be Centaurs, captured asteroids that orbit the sun together with Uranus, or comets. Uranus’ 27 identified moons appear to be made of ice and rock. The satellite system is chaotic and unstable. Astronomers predict that within a few million years, the moons could collide.
Miranda and Ariel
All of Uranus’ moons consist of ice and rock. Miranda and Ariel, two of the planets smaller moons, have features that indicate ongoing geological activity. Miranda’s diameter is just 450 kilometers (281 miles), yet it has surface fault scarps 10 kilometers (6 miles) high. Ariel, which has an 1,160 kilometers (725 miles) diameter, has canyons that could be between 3 and 5 kilometers (1.9 to 3.1 miles) deep. Miranda has areas of concentric fractures with surface volcanism called coronae, while the Ariel surface has ridged and smooth plains with surface volcanism. The extruded material could be ammonia and water ices that were melted by tidal heating of the moons’ interiors.
Umbriel, Oberon and Titania
Meteorite impacts dominate the geological features of the three largest moons. Umbriel has the most cratered surface and little apparent tectonic activity. Craters on Oberon are surrounded by brilliant rays similar to those of the Earth’s moon and Jupiter’s moon Callisto. Like Umbriel, Oberon appears to have little current tectonic activity. Impact craters on Titania reach diameters of 300 kilometers (187 miles), about one fifth of the moon’s 1,578-kilometer (986-mile) diameter. There fewer craters on Titania than on Oberon or Umbriel. But canyons and rifts indicate ongoing geological activity in its interior. The Messina Chasmata rift system is 50 to 100 kilometers (31 to 62 miles) wide.
- NASA: Uranus
- CNN: Diamonds May Be Produced on Other Planets
- Hubble Site: NASA’s Hubble Discovers New Rings and Moons around Uranus
- Information and Scientific News Service: Three Centaurs Follow Uranus Through the Solar System
- Lunar and Planetary Institute: Miranda and Ariel
- Royal Observatory of Belgium: The Icy Satellites
- Ablestock.com/AbleStock.com/Getty Images | 0.909853 | 3.785446 |
The Global-scale Observations of the Limb and Disk (GOLD) mission is part of the NASA Explorers Program, which is designed to provide frequent, low-cost access to space for heliophysics and astrophysics missions with small to mid-sized spacecraft. The information collected by the GOLD mission has a direct impact on understanding space weather and its impact on communication and navigation satellites, which we’ve come to rely on for everything from television programming to cell phone coverage and GPS in our vehicles.
The GOLD mission is being led by Principal Investigator, Richard Eastes, a research scientist at LASP. The University of Central Florida’s Florida Space Institute will be responsible for disseminating data products to the scientific community.
The scientific goals of the GOLD mission are:
- To determine how geomagnetic storms alter the temperature and composition of Earth’s atmosphere;
- To analyze the global-scale response of the thermosphere to solar extreme-ultraviolet variability;
- To investigate the significance of atmospheric waves and tides propagating from below the temperature structure of the thermosphere; and
- To resolve how the structure of the equatorial ionosphere influences the formation and evolution of equatorial plasma density irregularities.
GOLD is the first mission to study the weather of the thermosphere-ionosphere rather than its climate and also is the first NASA mission to fly as a hosted payload on a commercial communications satellite pioneering cost-effective access to geostationary orbit. GOLD is a hosted payload on the SES-14 satellite, which was built by Airbus Defence and Space.
- The GOLD instrument, a high-resolution far-ultraviolet imaging spectrograph with two identical channels
- Project management, systems engineering, safety and mission assurance, and instrument operations
- GOLD Principal Investigator, Richard Eastes
- GOLD Deputy Principal Investigator, Bill McClintock
- GOLD Program Manager, Mary Bolton
GOLD is positioned in a geostationary orbit at an altitude of about 22,000 miles, ideal for imaging the Earth below. The LASP-built instrument makes images of temperature and composition in the Sun-lit thermosphere and of electron density in the nighttime ionosphere. By capturing the first global-scale images of conditions in Earth’s upper atmosphere on a cadence of 30 minutes, GOLD is providing critical data on subtle changes due to space weather events.
Launch date: January 25, 2018
Launch location: Guiana Space Center in Kourou, French Guiana
Launch vehicle: Arianespace Ariane 5 rocket
Mission target: Earth’s ionosphere and thermosphere
Mission duration: 2-year nominal mission; extended mission possible
Other organizations involved:
- University of Central Florida’s Florida Space Institute (FSI)
- National Center for Atmospheric Research (NCAR)
- National Oceanic and Atmospheric Administration (NOAA)
- University of California, Berkeley
- SES Government Solutions (SES)
- Computational Physics, Inc. | 0.83988 | 3.39502 |
Composite ALMA image of the debris disk around the young star 49 Ceti. The distribution of dust is shown in red; the distribution of carbon monoxide is shown in green; and the distribution of carbon atoms is shown in blue. (Credit: ALMA (ESO/NAOJ/NRAO), Higuchi et al.)
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) found a young star surrounded by an astonishing mass of gas. The star, called 49 Ceti, is 40 million years old and conventional theories of planet formation predict that the gas should have disappeared by that age. The enigmatically large amount of gas requests a reconsideration of our current understanding of planet formation.
Planets are formed in gaseous dusty disks called protoplanetary disks around young stars. Dust particles aggregate together to form Earth-like planets or to become the cores of more massive planets by collecting large amounts of gas from the disk to form Jupiter-like gaseous giant planets. According to current theories, as time goes by the gas in the disk is either incorporated into planets or blown away by radiation pressure from the central star. In the end, the star is surrounded by planets and a disk of dusty debris. This dusty disk, called a debris disk, implies that the planet formation process is almost finished.
Recent advances in radio telescopes have yielded a surprise in this field. Astronomers have found that several debris disk still possess some amount of gas. If the gas remains long in the debris disks, planetary seeds may have enough time and material to evolve to giant planets like Jupiter. Therefore, the gas in a debris disk affects the composition of the resultant planetary system.
“We found atomic carbon gas in the debris disk around 49 Ceti by using more than 100 hours of observations on the ASTE telescope,” says Aya Higuchi, an astronomer at the National Astronomical Observatory of Japan (NAOJ). ASTE is a 10-m diameter radio telescope in Chile operated by NAOJ. “As a natural extension, we used ALMA to obtain a more detailed view, and that gave us the second surprise. The carbon gas around 49 Ceti turned out to be 10 times more abundant than our previous estimation.”
Thanks to ALMA’s high resolution, the team revealed the spatial distribution of carbon atoms in a debris disk for the first time. Carbon atoms are more widely distributed than carbon monoxide, the second most abundant molecules around young stars, hydrogen molecules being the most abundant. The amount of carbon atoms is so large that the team even detected faint radio waves from a rarer form of carbon, 13C. This is the first detection of the 13C emission at 492 GHz in any astronomical object, which is usually hidden behind the emission of normal 12C.
“The amount of 13C is only 1% of 12C, therefore the detection of 13C in the debris disk was totally unexpected,” says Higuchi. “It is clear evidence that 49 Ceti has a surprisingly large amount of gas.”
What is the origin of the gas? Researchers have suggested two possibilities. One is that it is remnant gas that survived the dissipation process in the final phase of planet formation. The amount of gas around 49 Ceti is, however, comparable to those around much younger stars in the active planet formation phase. There are no theoretical models to explain how so much gas could have persisted for so long. The other possibility is that the gas was released by the collisions of small bodies like comets. But the number of collisions needed to explain the large amount of gas around 49 Ceti is too large to be accommodated in current theories. The present ALMA results prompt a reconsideration of the planet formation models.
Quelle: National Astronomical Observatory of Japan | 0.83554 | 3.987495 |
A five-year survey of 200,000 galaxies, stretching back seven billion years in cosmic time, has led to one of the best independent confirmations that dark energy is driving our universe apart at accelerating speeds. The survey used data from NASA’s space-based Galaxy Evolution Explorer and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.
The findings offer new support for the favored theory of how dark energy works — as a constant force, uniformly affecting the universe and propelling its runaway expansion. They contradict an alternate theory, where gravity, not dark energy, is the force pushing space apart. According to this alternate theory, with which the new survey results are not consistent, Albert Einstein’s concept of gravity is wrong, and gravity becomes repulsive instead of attractive when acting at great distances.
“The action of dark energy is as if you threw a ball up in the air, and it kept speeding upward into the sky faster and faster,” said Chris Blake of the Swinburne University of Technology in Melbourne, Australia. Blake is lead author of two papers describing the results that appeared in recent issues of the Monthly Notices of the Royal Astronomical Society. “The results tell us that dark energy is a cosmological constant, as Einstein proposed. If gravity were the culprit, then we wouldn’t be seeing these constant effects of dark energy throughout time.”
Dark energy is thought to dominate our universe, making up about 74 percent of it. Dark matter, a slightly less mysterious substance, accounts for 22 percent. So-called normal matter, anything with atoms, or the stuff that makes up living creatures, planets and stars, is only approximately four percent of the cosmos.
The idea of dark energy was proposed during the previous decade, based on studies of distant exploding stars called supernovae. Supernovae emit constant, measurable light, making them so-called “standard candles,” which allows calculation of their distance from Earth. Observations revealed dark energy was flinging the objects out at accelerating speeds.
Dark energy is in a tug-of-war contest with gravity. In the early universe, gravity took the lead, dominating dark energy. At about 8 billion years after the Big Bang, as space expanded and matter became diluted, gravitational attractions weakened and dark energy gained the upper hand. Billions of years from now, dark energy will be even more dominant. Astronomers predict our universe will be a cosmic wasteland, with galaxies spread apart so far that any intelligent beings living inside them wouldn’t be able to see other galaxies.
The new survey provides two separate methods for independently checking the supernovae results. This is the first time astronomers performed these checks across the whole cosmic timespan dominated by dark energy. The team began by assembling the largest three-dimensional map of galaxies in the distant universe, spotted by the Galaxy Evolution Explorer. The ultraviolet-sensing telescope has scanned about three-quarters of the sky, observing hundreds of millions of galaxies.
“The Galaxy Evolution Explorer helped identify bright, young galaxies, which are ideal for this type of study,” said Christopher Martin, principal investigator for the mission at the California Institute of Technology in Pasadena. “It provided the scaffolding for this enormous 3-D map.”
The astronomers acquired detailed information about the light for each galaxy using the Anglo-Australian Telescope and studied the pattern of distance between them. Sound waves from the very early universe left imprints in the patterns of galaxies, causing pairs of galaxies to be separated by approximately 500 million light-years.
This “standard ruler” was used to determine the distance from the galaxy pairs to Earth — the closer a galaxy pair is to us, the farther apart the galaxies will appear from each other on the sky. As with the supernovae studies, this distance data were combined with information about the speeds at which the pairs are moving away from us, revealing, yet again, the fabric of space is stretching apart faster and faster.
The team also used the galaxy map to study how clusters of galaxies grow over time like cities, eventually containing many thousands of galaxies. The clusters attract new galaxies through gravity, but dark energy tugs the clusters apart. It slows down the process, allowing scientists to measure dark energy’s repulsive force.
“Observations by astronomers over the last 15 years have produced one of the most startling discoveries in physical science; the expansion of the universe, triggered by the Big Bang, is speeding up,” said Jon Morse, astrophysics division director at NASA Headquarters in Washington. “Using entirely independent methods, data from the Galaxy Evolution Explorer have helped increase our confidence in the existence of dark energy.”
For more information see the Australian Astronomical Observatory | 0.846408 | 4.101242 |
geckzilla wrote: sallyseaver wrote:
What I really like about this image is how it shows how a nebula is raw material for forming stars. And you can see where star formation has used up the surrounding nebula gases.
My understanding is that the orange-red gas around the orange crescent shape (that Alexander331 is referring to) is mostly hydrogen gas with some helium gas that is created by the multiple stars that are being born in the region. The hydrogen-helium gas is bumping into a clump of existing nebula gas and pushing it into the crescent shape. The proto-stars themselves are too small to be seen with the resolution of the image.
As a star forms, it actually creates and kicks out hydrogen and helium nuclei and electrons--the beginning of its stellar wind. You can see the mostly hydrogen (red) with some helium (orange) gas as part of star formation in the images below; these are images of proto-stars (called proplyds) from a study that the Hubble Space telescope did of the Orion Nebula. (The black in these images are multi-element gases that absorb the full visible spectrum of light.)
Those pictures illustrate artifacts around point sources. WISE resolution really isn't that great, and the stars tend to be all fuzzy partly because of the wavelengths, and I think partly also because of the way the data gets combined... Anyway, some sharpening filters have been applied which create some dark spots and rings, and infrared PSF's tend to form rings of dots.
It is also difficult to analyze the colors in this picture because they are more artistic than anything, but even when they are presented scientifically in the typical WISE color palette, red can sometimes be hydrogen-alpha emission, and other times it can be warm dust. Oftentimes it's both together. Context is important. And I think that saying this color is hydrogen and that color is helium is totally wrong. The bands being presented are wide, and you can see more about them here: http://www.astro.ucla.edu/~wright/WISE/passbands.html
Looking at the graph it's easy to see that all of them will cover multiple emission lines, even if you don't know exactly where the emission lines are. Note also that we are supplied no information about exactly which bands were even used, though I suspect it is mostly a combination of W3 and W4.
Yes, the APOD picture of NGC 7822 is fairly low resolution. Thank you for the reminder that it is primarily infrared data in the APOD picture. So red would tend to mean higher temperature, or "warm dust," yes? The "artistic" use of the orange-red color (orWISE hydrogen-alpha emission colors) for the gases in the upper right of the large image (after you click on the regular APOD image) seem to match the optical colors associated with the early stages of proplyd [protoplanetary disk, or young star object] development, per the proplyd images I included.
Regarding the proplyd images and the characterization of hydrogen and helium gases, the images are in optical wavelengths.
"Only the NASA/ESA Hubble Space Telescope, with its high resolution and sensitivity, can take such detailed pictures of circumstellar discs at optical wavelengths."
All of the colors and bands for the 2 proplyd images came from the Hubble Space Telescope ACS (Advanced Camera for Surveys) in the optical spectrum.
Colours & filters
Band | Wavelength
Optical, B | 435 nm
Optical, V | 555 nm
Optical, H-alpha | 658 nm
Infrared, Z | 850 nm
Infrared, I | 775 nm
I judged the information from this site regarding colors of dust and gases in telescope images to be usable.
http://www.clarkvision.com/articles/col ... llar.dust/
Do you disagree? | 0.848801 | 3.759243 |
Until the discovery of the Antikythera Mechanism, astrolabes were often considered the earliest analog mathematical devices. Such complex gearwork as in this astronomical calculator, however, only appeared (again) much later, especially in medieval clockworks. Leonardo da Vinci (1452–1519) knew gears, as his drawings show. Heron of Alexandria (1st century) used cogwheels for his pantograph. The construction of analog measuring and drawing instruments (for example, sectors, proportional dividers, compasses) and logarithmic circular and cylindrical slide rules was comparatively simple. Planimeters and (mechanical) differential analyzers were sophisticated. The first mechanical calculating machines were invented in the 17th century (Wilhelm Schickard, Blaise Pascal, Gottfried Leibniz). These digital devices required stepped drums, pinwheels, and accumulators. In the second half of the 20th century there was a competition between electronic analog computers and electronic digital computers.
This article is not about new groundbreaking insights. Rather, it presents an overview of decades of effort and different views. The review is not aimed at experts, but at computer scientists who are interested in the history of technology.
Some consider the Antikythera Mechanism (see Figures 1,2,3,4,5,6,7,8,9,10,11,12,13,14)—an astronomical calculator—as the world's first analog calculator. This article is based on an international survey among the leading specialists for the Antikythera Mechanism and an adaptation of a chapter of the book on the history of computing by the author and its English translation.3,4,5 For more explanation, see the sidebar "Structure of the Antikythera Mechanism."
Figure 1. The complex astronomical calculator, over 2,000 years old, was discovered in 1901 in the sea off the Greek island of Antikythera. The discovery of the mysterious technological marvel was a big surprise. It is still unknown where the device was manufactured and who invented it. The opinions about its age vary by about 120 years. There are numerous physical and virtual replicas. Research groups from Greece, the U.K. and the U.S. are trying to elicit the last secrets from the device. The Antikythera mechanism and the astrolabes are considered to be the first analogue calculators (courtesy of National Archaeological Museum, Athens/Costas Xenikakis).
Figure 2. The front of the Antikythera Mechanism shows seven hands (sun, moon, five planets) and a double ring scale (outside: Egyptian calendar, inside: zodiac). At the top and bottom of the digital model is the Parapegma inscription (courtesy of Hublot, with data from the Antikythera Mechanism Research Project).
Figure 3. The rear side of the mechanism (digital reconstruction) has two spiral scales. Above: Metonic cycle with display of the Callippic cycle (restored) and the Panhellenic games; below: Saros cycle for eclipses and Exeligmos cycle (courtesy of Hublot, with data from the Antikythera Mechanism Research Project).
Figure 6. Digital reconstruction by Tony Freeth: on the left the front side with the two concentric scales and seven pointers, on the right the back side with the spiral scales, among others for the display of solar and lunar eclipses (courtesy of Tony Freeth, Images First Ltd., London).
Figure 14. One of the 48 models designed by two Chinese researchers for the design of the Antikythera Mechanism. Above are shown the hands for sun, moon and five planets, below four astronomical cycles and the course of the Panhellenic games (courtesy of Jian-Liang Lin and Hong-Sen Yan).
It is not easy for most laypeople to understand the movements of the celestial bodies. The structure of the Metonic dial "was very unusual, having two distinct centers. We will call one of them the axial center because this was the location of the axle or arbor bearing the dial's pointer ... On the right side of the plate, a series of five concentric semicircular slots ... were cut through the plate. On the left side was another series of five concentric semicircular slots, centered on the secondary center.17 (To learn more about the structure, the astronomical functions, and the details of the gearing, see Seiradakis,19 Edmunds,9 and Freeth.14)
For a long time, the purpose of the Antikythera Mechanism—a bronze gearwork in a wooden case—was unknown. Was the approximately 32cm-33cm high, 17cm-18cm wide, and at least 8cm deep, shoe-box sized device an astrolabe, a planetarium, or a calculator?
This question has been resolved today, unlike many others. It is an astronomical calculating machine. The device determines the approximate position of the sun, the moon and—as can be inferred from the texts on the device—possibly the (five then known) planets and serves as a calendar. It predicted or described solar and lunar eclipse possibilities based on the Saros cycle and calculated the phases of the moon. The machine also showed the data for the four Panhellenic games (the Isthmia, Olympia, Nemea, and Pyhtia) as well as the minor Naa of Dodona and Halieia of Rhodes. The scales are concentric on the front. The major cycles of the back (Metonic and Saros dials) were spiral-shaped. Greek (astronomical and technical) texts were found on the covers of both sides of the device. Almost certainly the machine contains over 40 individual gears (including any plausible reconstruction of the lost planetary gearwork). The fixed programmed calculator was presumably operated by a lateral knob or a crank. The development of such astronomical instruments apparently began in the 3rd century B.C. The mechanism is so mature that it can hardly be a unique device. In the history of culture, technology, and science, gear-works are of outstanding importance. Such complex constructions only reappear in Europe with the astronomical tower clocks in the 14th century, more than 1,000 years later. The Antikythera Mechanism is probably the world's the first analog calculator. Alexander Jones of New York University believes the device was designed primarily for educational and philosophical purposes. It certainly was good for demonstrations. For astronomers it was probably too imprecise, and unsuitable for navigation.
Why astronomical calculators have rarely survived? The bronze gears of the Antikythera Mechanism were only 2mm thin. This fine, fragile construction may explain why hardly any devices have survived. Metal was precious and was therefore recycled. These devices were not gold-plated artifacts with precious stones.
The Antikythera Mechanism Research Project. In 2005, an international research community called Antikythera Mechanism Research Project was founded. It is mainly made up of experts from the fields of astronomy, physics, astrophysics, mathematics, engineering, history of technology and science, archaeology, and classicists. For further information, see http://antikythera-mechanism.gr.
When was the astronomical calculator found? The Ionian island of Antikythera, originally called Aigila, is located between the Peloponnese peninsula and Crete, opposite Kythera (hence Antikythera). The shipwreck was found by sponge divers in 1900. The Antikythera Mechanism came to light in the summer of 1901 (probably July). Dives were also carried out in 1953, 1972, and several since 2012 up to the present year. The mechanism is only partially preserved and consists of 82 damaged fragments. Fundamental investigations have only been carried since the 1950s. Tomographic methods were also used for this purpose.
When did the ship go down? As can be seen from the finds of coins and amphorae, the ship sank between 70 B.C. and 50 B.C. This date period is generally accepted. "Around 60 B.C., a ship was wrecked of the northeast coast of a small island called Aigila in the straits between Crete and the Peloponnese ... The exact character of the ship is not known, but it was probably a large merchant vessel, perhaps about 40 meters long."17 The vessel may have been on its way from Asia Minor to the western Mediterranean. Perhaps the sail freighter was about 10m wide and could load 250 tons. The cargo included silver and bronze coins dating between 85 B.C. and 60 B.C.
When was the ship built? According to the 2010 radiocarbon analyses by Andrew Wilson (University of Oxford), the wood used for shipbuilding is estimated (with a probability of 84.8%) to have been cut between 211 B.C. and 40 B.C. This can be seen from the new calibration curves of radiocarbon dating (C-14 method, 14C method).7 Since wooden ships do not last indefinitely long and are not permanently seaworthy, the boat is likely to have been manufactured at the earliest a few decades before the shipwreck.
When was the astronomical calculator built? Opinions on the year of manufacture of the astronomical calculator vary widely. The estimates range from 205 B.C. to 50 B.C. Christián Carman, James Evans, and Tony Freeth assume a production approximately 205 B.C. Michael Edmunds, Paul Iversen, Alexander Jones, and Michael Wright however believe in a much later production at a time when the ship was much closer to sinking.
Michael Edmunds from the University of Cardiff writes: "The present best estimate of its construction date is around the middle of the range 150 B.C.—60 B.C.—although a date as early as early as 220 B.C. is not completely ruled out."7 The astrophysicist adds: "My preferred period is 140 B.C.-70 B.C. But there must have been earlier, probably simpler versions. So, one would guess that similar mechanical devices might date from 200 B.C. or maybe 250 B.C."7 According to Edmunds, there are references in the literature mentioning that astronomical devices were made or at least known from 250 B.C. to at least 500 A.D.
The historian of science and classicist Alexander Jones writes in this context: "We are obviously a long way from being able to put together a coherent story of the evolution and eventual degeneration of the ancient tradition of astronomical mechanisms, but there is enough evidence to suggest that complex and scientifically ambitious mechanisms were being made at least through the three centuries from about 100 B.C. to A.D. 200, and that the people who were most likely to encounter them were mechanicians, philosophers, and scientists."17
Paul Iversen from Case Western University, Cleveland, believes in a late production of the Mechanism: "I would say the Mechanism was manufactured soon before the shipwreck of about 70 BCE-50 BCE, but in any case, probably not more than one generation, or about 100 BCE at the earliest."16
Jones shares a similar opinion: "A far simpler hypothesis, however, is that the Mechanism was made somewhere around the Aegean not long before the shipwreck and was on its way to its intended home by a route that would next have proceeded up the Adriatic toward, say, Brundisium, stopping somewhere along the way to deliver part of the cargo. Occam's razor thus makes it probable that the Mechanism was commissioned by someone who lived in or near Epirus in the first half of the first century B.C."17
Jones adds: "I argued that the archeological context favors the hypothesis that the Mechanism was new when it was lost in the wreck, because otherwise it becomes difficult to account for the presence of an antique object that was manifestly made for a locality west of the Aegean in a cargo originating in the Aegean and destined for points west."17
Michael Wright (formerly of the Science Museum, London): "There is, however, no good argument for suggesting that the instrument was designed that early [205 B.C.] and there is a counterargument that the several displays were adjusted to mutual agreement in a way that could not have been done before the latter half of the second century B.C. The most likely explanation is that the designer of these displays drew on old information."20
The physicist Wright, however, rejects the assumption the instrument was new when the ship sank. Part of the device was mechanically confused. He writes: "I think it very unlikely that the instrument was very old at the time because I think it simply would not have lasted very long without being destroyed by use and handling. I suggest that it was probably built with a generation or so of its loss; that is, within a few decades of 100 B.C.20
The physicist James Evans from the University of Puget Sound, Tacoma, WA, tends to assume an early production: "The eclipse predictor best fits an 18-year Saros cycle that started in 205 B.C. One or two Saros cycles later would also work, though with somewhat larger errors. Of course, we cannot rule out the possibilty that it was built considerably later but using an out-of-date eclipse cycle."11
London-based Tony Freeth, on the other hand, assumes a construction around 205 B.C.: The prediction of the solar and lunar eclipses is based on the Saros cycle. The display on the back of the mechanism is intended to allow the determination of its age.13
According to Christián Carman and James Evans, the eclipse dial works best when the full moon of the first month of the Saros cycle reaches May 12, 205 B.C.6
If the astronomical calculator had been manufactured by Archimedes during his lifetime, it would have been approximately 150 years old when the ship sank. Such an early production does not seem very plausible.
Where was the mechanism made? The origin of the mechanism is unknown. Sicily was once thought to be the place of production, current thinking puts Rhodes as the likely location.
Possibilities include Alexandria, Pergamon, Syracuse and Rhodes. Syracuse had the advantage of any heritage left by Archimedes, but the problem that it was sacked in at the time of his death in 211 B.C., although something may have remained. The best candidate must be Rhodes, a port at which the Antikythera ship had called (judged by some of its cargo) not long before its wreck. Rhodes was a highly technological naval center around 100 B.C. with a fine bronze industry and an astronomical tradition. It is also one place where we know that a similar contemporary device was reputedly made and seen."16
Edmunds adds that the star calendar (Parapegma) on the wheels corresponds to the geographical latitude of Rhodes and that Cicero had seen a comparable device on Rhodes in the first century B.C.8
The classicist and epigrapher Iversen contends the computer was most likely to be manufactured in Rhodes for several reasons:16
Iversen considers it unlikely that Archimedes built the device, because it makes use of certain findings on the movement of the sun and moon, which are attributed to Hipparchos (around 150 B.C.). For example, Poseidonios or an employee of his school could be considered as the creator. The customer is likely to be from Epirus due to the epirotic calendar (Metonic spiral).16
Cicero mentions in De Natura Deorum, book 2, (45 B.C.), the "sphaera" of Posidonius. The word "sphaera" (Greek sphaira) has several meanings: "We need to be careful to distinguish mechanized planetaria from certain other concepts and categories of objects that may be described in similar language. The Greek word sphaira (or Latin sphaera) may refer to an astronomical mechanism but was also appropriate for a simple globe."17
The star calendar is also associated with the Greek author Geminos, who presumably lived in the 1st century.
The mathematician Freeth, on the other hand, assumes the original form of the astronomical computer originated from Archimedes. This famous scholar, who died in 211 B.C., lived in the Corinthian colony in Syracuse. According to Cicero, the great Greek scholar is said to have made such an instrument. The sophisticated state of the mechanism was a surprise. Until the discovery of Price, nothing comparable was known in ancient Greek technology. Freeth writes: "I personally think it is likely that the original design came from Archimedes and he started the tradition of making these devices. The Antikythera Mechanism is simply a later version of the Archimedes design. But there is little hard evidence. ... The sophistication of the mechanism, when uncovered by Price, was astonishing, given what had previously been known about ancient Greek technology."13
According to Wright, however, the mechanism of Archimedes was a completely different device, namely a mechanical celestial globe. The English man, who also works as a mechanic, has reconstructed it. Cicero, who reported in De Re Publica (book 1, 54 B.C-51 B.C.) and in Tusculanae Disputations (book 1, 45 B.C.) on the "sphaera" of Archimedes, has lived, however, over 100 years later than the outstanding Sicilian researcher.
Kyriakos Efstathiou (University of Thessaloniki) suggests that at this time one of the most important Greek astronomers, Hipparchos, lived in Rhodes. Many researchers believed he, his disciple Poseidonios, or someone from the astronomy school there could be considered the creator of the mechanism.10
The most convincing assumption is the Antikythera Mechanism comes from the surroundings of Poseidonios. The stoic philosopher had no astronomical or craft skills himself. There are obviously close relations between the Mechanism and Hipparchos as well as Geminos.
There are numerous real replicas (reconstructions) of the Antikythera Mechanism and some virtual models (simulations). Among the best known real (that is, physical) replicas were the devices of Ioannis Theofanidis (Greece, 1934), Derek de Solla Price and Robert Deroski (U.S.), Allan Bromley and Frank Percival (Australia), John Gleave (U.K.), Michael Wright (U.K.) as well as John Seiradakis and Kyriakos Efstathiou (Greece). Further models have been produced by Dionysios Kriaris (Greece), Massimo Vicentini (Italy), and Tatjana van Vark (Netherlands). However, some replicas are not operational and differ from the original design. 3D Solidforms sells the devices developed in cooperation with the Aristotle University of Thessaloniki. Markos Skoulatos and Georg Brandl (Germany) have built new real and virtual replicas.
Digital replicas are available, for example, from Tony Freeth (U.K.). In Switzerland, the Mechanism was also reconstructed, for example by Ludwig Oechslin (formerly International Watch Museum in La Chaux-de-Fonds). Matthias Buttet created for Hublot SA, Nyon VD a watch that incorporates the functions of the Antikythera Mechanism.
The most important (real) replicas are the reconstructions of Michael Wright and the Antikythera Mechanism Research Project (2006). Wright, the leading model maker of Antikythera Mechanism, justly points out that a computer-generated 3D image does not have the same persuasive power as a physical model. In the artificial world there is neither mass, inertia, force, friction, nor elastic or inelastic deflection. Questions of material strength and wear properties are excluded.
The physicist Markos Skoulatos of the University of Technology in Munich designed a real reconstruction and then followed with a digital model, developed together with the physicist Georg Brandl. The mechanical reconstruction exhibits less friction and the virtual model high accuracy.
The (non-programmable) mechanism of Antikythera is sometimes called the world's oldest analog "computer." The gear trains refer to the orbits of the planets. Due to this similarity, the mechanical calendar computer appears as an analog device. In addition to the input, the output of this machine is also analog: the dials (scales) and the continuously rotating hands.
However, the calendars are calculated digitally. The number of teeth on the gears is always an integer. The ratio between two gears is always a rational number. These relations reflect the celestial movements, for example, in the Metonic cycle (x cycles in y years, where x and y are integers). Rational numbers are numbers that can be represented as a quotient of two integers. In addition to the number zero, this includes all (positive and negative) whole and fractional numbers.
The display is analog, but the gear-work operates digitally. Most researchers regard the astronomical marvel as an analog device. However, it can also be understood as a mixed calculator. Astronomical clocks are also hybrid, as are digital clocks with analog display. A numerical display is more precise than analog pointers but less comfortable to read.
For further explanations see Computation and its Limits by P. Cockshott, L.M. Mackenzie, and G. Michaelson (Oxford Press 2012).
The current state of research can be summarized as follows: The Antikythera Mechanism, discovered in 1901, was lost about 60 B.C. when a Roman merchant ship sank in the Mediterranean Sea. The complex astronomical calculator was probably built on the island of Rhodes near the Greek philosopher Poseidonios. The client for the teaching material seems to be a person in northwestern Greece.
I am very grateful to Michael G. Edmunds, Kyriakos Efstathiou, James C. Evans, Tony Freeth, Paul A. Iversen, Alexander R. Jones, and Michael T. Wright for their helpful answers in connection with my survey and for the valuable comments of the reviewers. Markos Skoulatos and Georg Brandl provided exciting information on their new project. In addition, I would like to thank all for the permission to reproduce the fascinating images.
3. Bruderer, H. Meilensteine der Rechentechnik I. Mechanische Rechenmaschinen-Rechenschieber - historische Automaten - wissenschaftliche Instrumente. de Gruyter Oldenbourg, Berlin/Boston, 2018; https://www.degruyter.com/view/product/480555.
4. Bruderer, H. Meilensteine der Rechentechnik II. Erfindung des Computers - Elektronenrechner - Entwicklungen in Deutschland, England und der Schweiz. de Gruyter Oldenbourg, Berlin/Boston, 2018; https://www.degruyter.com/view/product/503373.
5. Bruderer, H. Milestones in Analog and Digital Computing. Springer Nature Switzerland AG, Cham, 3rd edition, 2020; https://www.springer.com/de/book/9783030409739.
12. Freeth, T. Eclipse prediction on the ancient Greek astronomical calculating machine known as the Antikythera Mechanism. Plos One 9, 7 (July 30, 2014) e103275; https://doi.org/10.1371/journal.pone.0103275
14. Freeth, T. Revisitng the eclipse prediction scheme in the Antikythera mechanism. Palgrave Commun. (2019); doi.org/10.1057/s41599-018-0210-9
18. Jones, A.R. The Antikythera mechanism and the public face of Greek science. In Proceedings of From Antikythera to the Square Kilometre Array: Lessons from the Ancients Conference (Kerastari, Greece, June 12–15, 2012).
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The universe has been expanding since the Big Bang occurred 13.8 billion years ago—a proposition first made by the Belgian canon and physicist Georges Lemaître (1894-1966), and first demonstrated by Edwin Hubble (1889-1953).The American astronomer discovered in 1929 that every galaxy is pulling away from us, and that the most distant galaxies are moving the most quickly. This suggests that there was a time in the past when all the galaxies were located at the same spot, a time that can only correspond to the Big Bang.
This research gave rise to the Hubble-Lemaître law, including the Hubble constant (H0), which denotes the universe’s rate of expansion. The best H0 estimates currently lie around 70 (km/s)/Mpc (meaning that the universe is expanding 70 kilometers a second more quickly every 3.26 million light years). The problem is that there are two conflicting methods of calculation.
The first is based on the cosmic microwave background: This is the microwave radiation that comes at us from everywhere, emitted at the time the universe became cold enough for light to be able to circulate freely (about 370,000 years after the Big Bang). Using the precise data supplied by the Planck space mission, and given the fact that the universe is homogeneous and isotropic, a value of 67.4 is obtained for H0 using Einstein’s theory of general relativity to run through the scenario. The second calculation method is based on the supernovae that appear sporadically in distant galaxies. These very bright events provide the observer with highly precise distances, an approach that has made it possible to determine a value for H0 of 74.
If we were in a kind of gigantic ‘bubble, where the density of matter was significantly lower than the known density for the entire universe, it would have consequences on the distances of supernovae and, ultimately, on determining H0.
All that would be needed would be for this “Hubble bubble” to be large enough to include the galaxy that serves as a reference for measuring distances. By establishing a diameter of 250 million light years for this bubble, the physicist calculated that if the density of matter inside was 50% lower than for the rest of the universe, a new value would be obtained for the Hubble constant, which would then agree with the one obtained using the cosmic microwave background.
To narrow the gap, professor Lombriser (a professor in the Theoretical Physics Department in UNIGE’s Faculty of Sciences)entertained the idea that the universe is not as homogeneous as claimed, a hypothesis that may seem obvious on relatively modest scales. There is no doubt that matter is distributed differently inside a galaxy than outside one. | 0.821807 | 4.199531 |
(NASA) – NASA’s Hubble Space Telescope has picked up the faint, ghostly glow of stars ejected from ancient galaxies that were gravitationally ripped apart several billion years ago. The mayhem happened 4 billion light-years away, inside an immense collection of nearly 500 galaxies nicknamed “Pandora’s Cluster,” also known as Abell 2744. The scattered stars are no longer bound to any one galaxy, and drift freely between galaxies in the cluster.
By observing the light from the orphaned stars, Hubble astronomers have assembled forensic evidence that suggests as many as six galaxies were torn to pieces inside the cluster over a stretch of 6 billion years. Computer modeling of the gravitational dynamics among galaxies in a cluster suggest that galaxies as big as our Milky Way are the likely candidates as the source of the stars. The doomed galaxies would have been pulled apart like taffy if they plunged through the center of the galaxy cluster where gravitational tidal forces are strongest. Astronomers have long hypothesized that the light from scattered stars should be detectable after such galaxies are disassembled. However, the predicted “intracluster” glow of stars is very faint and was therefore a challenge to identify.
“The Hubble data revealing the ghost light are important steps forward in understanding the evolution of galaxy clusters,” said Ignacio Trujillo of the Instituto de Astrofísica de Canarias (IAC), La Laguna, Tenerife, Spain, one of the researchers involved in this study of Abell 2744. “It is also amazingly beautiful in that we found the telltale glow by utilizing Hubble’s unique capabilities.”
“The results are in good agreement with what has been predicted to happen inside massive galaxy clusters,” added Mireia Montes of the IAC, lead author of the paper published in the Oct. 1 issue of The Astrophysical Journal.
The team estimates that the combined light of about 200 billion outcast stars contributes approximately 10 percent of the cluster’s brightness.
Because these extremely faint stars are brightest at near-infrared wavelengths of light, the team emphasized that this type of observation could only be accomplished with Hubble’s infrared sensitivity to extraordinarily dim light.
Hubble measurements determined that the phantom stars are rich in heavier elements like oxygen, carbon, and nitrogen. This means the scattered stars must be second- or third-generation stars that were enriched with the elements forged in the hearts of the universe’s first-generation stars. Spiral galaxies — like the ones believed to be torn apart — can sustain ongoing star formation that creates chemically enriched stars.
With the mass of 4 trillion suns, Abell 2744 is a target in the Frontier Fields program. This ambitious three-year effort teams Hubble and NASA’s other Great Observatories to look at select massive galaxy clusters to help astronomers probe the remote universe. Galaxy clusters are so massive that their gravity deflects light passing through them, magnifying, brightening, and distorting light in a phenomenon called gravitational lensing. Astronomers exploit this property of space to use the clusters as a zoom lens to magnify the images of far-more-distant galaxies that otherwise would be too faint to be seen.
Montes’ team used the Hubble data to probe the environment of the foreground cluster itself. There are five other Frontier Fields clusters in the program, and the team plans to look for the eerie “ghost light” in these clusters, too. | 0.847626 | 3.982392 |
Things to Know
Space travel has made exceptional progress over the years. It was only in July 1969 that man first walked on the moon, and now just 50 years later there are plans to send humans to Mars in the not-so-distant future. According to NASA, they plan to send humans to Mars by the year 2033.
There have been several spacecrafts that have landed on Mars – the United States has successfully landed eight on the Red Planet, including Opportunity and InSight. While the spacecrafts have conducted exceptional research on the planet, it’s not the same as having humans exploring the area.
Although it’s exciting to think about humans landing on Mars, they will encounter numerous problems during their exploration of our planetary neighbor. From long-lasting dust storms and exceptionally high radiation levels, to worrying about their food supply and their overall health, they will have several obstacles to overcome — not to mention to extremely long trip there and back. Let’s take a look at 10 of the most challenging obstacles the astronauts will face on their journey.
10. Mars May Still Be Volcanically Active
In a new study, it appears as though Mars may still be volcanically active. Located under solid ice at the South Pole, there is a lake of liquid water measuring 20 kilometers wide. While it was originally thought that the water stayed in liquid format because of dissolved salt as well as pressure from above the lake, new research provides a much different theory.
The new study concluded that the salt and pressure couldn’t have stopped the water from becoming frozen and that volcanic activity (more specifically a magma chamber that was created in the previous few hundred years) was the only way that it could have remained in liquid format.
Mars was definitely volcanically active in the past, as Olympus Mons is the biggest volcano in our entire solar system. Located near Olympus Mons are three other shield volcanoes called Tharsis Montes, and there are several more volcanoes on the Red Planet.
According to the study, magma from the planet’s interior came up to the surface around 300,000 years ago. Instead of breaking through the surface of the planet and creating a new volcano, it remained in a magma chamber located beneath the South Pole. When the magma chamber cooled down, it would have released a sufficient amount of heat in order to melt the water underneath the polar ice sheet. They believe that the heat is still being slowly released even to this day. The authors of the study suggest that if there was volcanic activity 300,000 years ago, there is a definite possibility that it’s still active today which could cause an issue for eventual visitors to the planet.
9. Scarce Food Sources
Astronauts need to eat and growing food on Mars would be a very difficult task. In fact, it would take several hundred years before farming could be conducted without protective greenhouses since the soil there contains perchlorates, which are harsh chemicals that would need to be removed before any plants could be grown.
In addition to the chemicals, gravity would also pose a problem as the planet only has around one-third of the gravity that’s here on Earth. Although some experiments have proved some plants can grow in the microgravity located on the International Space Station, that doesn’t mean that they’ll grow on Mars.
There is some hope, as revealed in a 2014 study that tomatoes, wheat, cress and mustard leaves were able to grow in simulated Martian soil without fertilizers for 50 days. But transforming Mars into a planet capable of growing plants would take hundreds of years for its thin atmosphere to contain enough oxygen.
Let’s say, for example, that humans could quickly transform the atmosphere in order to grow plants, the winters pose another huge problem as the temperatures can dip as low as -207 degrees Fahrenheit.
8. They’d Have To Wear Permanent Space Suits
Astronauts visiting Mars would have to wear permanent space suits during their trip as the planet is not suitable for humans. The suits would have to be flexible enough for the astronauts to work with construction materials as well as for using different machines. Plus, they have to be comfortable enough for them to essentially live in.
As for the atmosphere there, it’s comparable to being at an altitude of 25 kilometers on Earth, which means that the air would be much too thin for humans to breathe. In addition to the thin air, there is way too much carbon dioxide and not enough oxygen. And since the winter temperatures can get as low as -207 degrees Fahrenheit, the astronauts need warm space suits to keep their blood circulating throughout their bodies. These spacesuits will be their life-line, so they need to be made perfectly for the astronauts to survive their exploration trip to our planetary neighbor.
7. Creating A Human Civilization May Not Be So Easy
Obviously, the astronauts exploring the Red Planet wouldn’t be there to create Martian families, but there is much talk about one day humans colonizing there permanently. That may not be as easy as it sounds. Just the lack of gravitational pull and the high amount of radiation are enough to severely damage a fetus. While there have been several experiments involving mice, rats, frogs, salamanders, fish, and plants to see if they could successfully reproduce in space, results have been inconclusive.
While mice and humans are obviously different, based on the experiments conducted, as of right now it’s not looking good for humans to successfully reproduce on Mars.
6. Landing And Returning
Landing on Mars will not be a smooth ride. For example, when NASA’s InSight spacecraft entered into the atmosphere on Mars, it was moving at a whopping 12,300 MPH. While it was descending through the atmosphere, it had to slow down to just 5 MPH before landing on the surface. The deceleration happened in less than seven minutes, which NASA engineers referred to as “seven minutes of terror.”
Since we know how to land on the Red Planet – although it will most likely be one rough landing – leaving Mars may not be so easy. The Mars Ascent Vehicle (MAV) will be powered by liquid oxygen and methane, with all of the ingredients (hydrogen, carbon, and oxygen) being available on Mars. The atmosphere is mostly carbon dioxide, so that would be relatively easy to get; however, drilling for water would be much more challenging as they wouldn’t be 100% certain that water lies underneath them. Assuming they would get the necessary ingredients for the fuel, taking off from the harsh environment and atmosphere on Mars may not be an easy lift-off.
5. Long-Lasting Dust Storms
Mars is definitely known for their massive dust storms – some of which are so huge that they can be seen from Earth-bound telescopes. As a matter of fact, some dust storms cover the same area as an entire continent, lasting for several weeks. And approximately every three Mars years (or five and a half Earth years), a gigantic dust storm covers the entire Red Planet which are known as “global dust storms.” The good thing about the dust storms is that the strongest winds only reach approximately 60 miles per hour, so it’s very unlikely that they would damage any spacecrafts.
On the other hand, the small dust particles tend to stick to surfaces and even mechanical gears. One specific problem would be the solar panels and if enough dust would cover them, they wouldn’t be able to absorb as much sunlight in order to get the energy to power the equipment.
4. Extremely Rough Terrain And Chilling Weather
The very rough and rocky terrain on Mars could cause problems for the spacecraft as well as the astronauts who are trying to walk around on the surface. The planet is covered with rocks, canyons, volcanoes, craters, and dry lake beds, as well as red dust covering the majority of the surface. The Curiosity rover experienced such problems when, in 2013, it came upon an area with sharp rocks that looked similar to spikes. The sharp rocks – that looked like 3 to 4 inch teeth from a shark – were most likely created by the wind. These sharp rocks could dent and even puncture wheels, not to mention how impossible they’d be to walk on.
Astronauts visiting the Red Planet will certainly not be accustomed to its extremely freezing cold temperatures. The average temperature on the planet is a frigid -80 degrees Fahrenheit and can get as low as -207 degrees Fahrenheit during the winter. They would need special spacesuits that would keep them warm from the chilling temperatures.
3. High Levels Of Radiation And Very Little Gravity
Since Mars has a much thinner atmosphere than Earth, humans visiting the Red Planet will have very little protection against the high levels of radiation. In fact, they have to worry about two dangerous sources of radiation. The first are the dangerous solar flares that come from our sun, for which they’ll need proper protection. The second are particles from galactic cosmic rays that pass through the solar system almost at the speed of light and can damage anything they hit, such as the spacecraft or even the astronauts themselves. The spacesuits, as well as the spacecrafts, will need to be made from materials that will shield them from the high levels of radiation.
Another major problem is that the gravity on Mars is only a fraction of what it is on Earth. In fact, the gravity on the Red Planet is 62% lower than it is here on our planet. To better understand, if a person weighs 220 pounds on Earth, they would weigh just 84 pounds on Mars. There are several factors that contribute to its lower gravity, such as density, mass, and radius of the planet. While both planets have nearly the same land surface, Mars has just 15% of our planet’s volume and only 11% of our mass.
While it’s still uncertain what long-term effects the change in gravity would have on the astronauts’ health, research indicates that the effects of microgravity would cause loss of bone density, muscle mass, organ function, and eyesight.
2. The Long Journey To Mars
Before the astronauts even get to Mars, they would have to endure an exceptionally long journey just to get there. As for how long the trip would actually take, there are several factors to take into consideration, such as where the planets are positioned in the solar system at the time of the launch, since the distance between them is always changing as they go around the sun.
While the average distance between Mars and Earth is 140 million miles, they do get much closer to each other depending on their position around the sun. The two planets would be closest to each other when Mars is located at its closest position to the sun and the Earth is at its farthest position. At that point, the two planets would be 33.9 million miles away from each other. When the planets are located on opposite sides of the sun, they are at a distance of 250 million miles from each other.
According to NASA, the ideal launch to Mars would take approximately nine months. And that’s just how long it would take to get there. It would take another nine months or so to return back to Earth, along with however long they end up staying on the Red Planet.
1. Mental And Physical Health Issues
In addition to the rough terrain, freezing temperatures, and dust storms, astronauts would also have to worry about the mental and physical health issues that they could develop. The process of going from two highly different gravitational fields would affect their spatial orientation, balance, mobility, motion sickness, hand-eye and head-eye coordination.
Being confined to a small space on an unpopulated planet away from family and friends for several months or years would be mentally hard on them. They could develop a drop in their mood, morale, cognition, or a decline in their daily interactions (misunderstandings and impaired communication). In addition, they could develop sleep disorders, fatigue, or even depression.
Being in an enclosed area makes it very easy for one person to transfer germs to the others, which could cause illnesses, allergies, or diseases.
The biggest health factor is the high levels of radiation on Mars, which could increase their chances of developing cancer. Radiation can damage their central nervous system, causing changes to their cognitive function, their behavior, and reducing their motor function. It could also cause nausea, vomiting, fatigue, and anorexia. Cardiac and circulatory diseases, as well as cataracts, could additionally develop. | 0.83856 | 3.336544 |
From Fairfield, it will be visible between 23:17 and 02:41. It will become accessible around 23:17, when it rises to an altitude of 21° above your south-eastern horizon. It will reach its highest point in the sky at 01:01, 26° above your southern horizon. It will become inaccessible around 02:41 when it sinks below 22° above your south-western horizon.
134340 Pluto opposite the Sun
This optimal positioning occurs when 134340 Pluto is almost directly opposite the Sun in the sky. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time.
At around the same time that 134340 Pluto passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest and largest.
This happens because when 134340 Pluto lies opposite the Sun in the sky, the solar system is lined up so that 134340 Pluto, the Earth and the Sun form a straight line with the Earth in the middle, on the same side of the Sun as 134340 Pluto.
In practice, however, 134340 Pluto orbits much further out in the solar system than the Earth – at an average distance from the Sun of 39.86 times that of the Earth, and so its angular size does not vary much as it cycles between opposition and solar conjunction.
On this occasion, 134340 Pluto will lie at a distance of 33.56 AU, and reach a peak brightness of magnitude 15.0. Even at its closest approach to the Earth, however, 134340 Pluto is so distant from the Earth that it is not possible to distinguish it as more than a star-like point of light.
134340 Pluto in coming weeks
Over the weeks following its opposition, 134340 Pluto will reach its highest point in the sky four minutes earlier each night, gradually receding from the pre-dawn morning sky while remaining visible in the evening sky for a few months.
The position of 134340 Pluto at the moment it passes opposition will be:
|Object||Right Ascension||Declination||Constellation||Magnitude||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 20 July 2022|
21 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|20 Jul 2022||– 134340 Pluto at opposition|
|18 Jan 2023||– 134340 Pluto at solar conjunction|
|22 Jul 2023||– 134340 Pluto at opposition|
|20 Jan 2024||– 134340 Pluto at solar conjunction| | 0.820787 | 3.663278 |
By Karin Zeitvogel
WASHINGTON, May 31 (PNA/RIA Novosti) - Flying to Mars in the spacecraft available today would expose astronauts to radiation levels that could significantly boost their risk of contracting cancer, a study published Thursday said.
In terms of accumulated dose, its like getting a whole-body CT scan once every five or six days, said Cary Zeitlin, a researcher at the Colorado-based Southwest Research Institutes (SwRI) space science and engineering division, and lead author of the study published in the journal Science.
Researchers from the SwRI, NASA, the German Aerospace Center and Christian Albrechts University in Kiel, Germany used measurements collected by a Radiation Assessment Detector (RAD) on board the Mars Science Laboratory that delivered the Curiosity rover to the Red Planet to determine how much radiation astronauts would be exposed to during the 348-million-mile (560-million-kilometer) journey to Mars.
RAD measured radiation inside the spacecraft for 253 days, focusing on two types of radiation exposure that could pose serious health risks to astronauts in deep space.
These were long-term, low-dose exposure to galactic cosmic rays (GCRs) and short-term exposure to solar energetic particles (SEPs) produced by solar flares from the sun and coronal mass ejections such as those which were captured in stunning images earlier this month.
The data collected by RAD shows that an astronaut or cosmonaut would be exposed to around .66 Sieverts of radiation during a roundtrip to Mars with rockets and spacecraft with the protection used today.
One Sievert of radiation exposure is associated with a five percent increase in the risk of dying of cancer, the researchers note. The same level has been set by several space agencies, including Russias, Canadas and the European Space Agency, as the maximum allowable exposure level during an astronauts or cosmonauts career.
Time spent on Mars would expose the space travelers to even more radiation, and this should be taken into account when new spacecraft and a Mars habitat are being developed, the scientists said.
The spacecraft used today are much more effective against low-energy SEPs than high-energy and highly penetrating GCRs, according to the study.
The vehicles developed to take humans to Mars would likely have a storm shelter to protect against solar particles, Zeitlin said.
But the GCRs are harder to stop and even an aluminum hull a foot thick wouldnt change the dose very much, he added.
NASAs "Curiosity" Rover Sends Back First Color Panoramic Pictures of MarsZoom InAdd to blog
The researchers also noted that the seven months from Dec. 6, 2011 to July 14, 2012 — during which RAD measured radiation on the spacecraft bound for Mars were relatively quiet in terms of solar activity, meaning there were not so many SEP particles bombarding the spacecraft.
The unpredictable nature of solar activity would impact radiation exposure, and the habitat and spacecraft developed for a Mars mission would help to mitigate exposure during a journey to the Red Planet.
NASA is looking to develop spacecraft that would make the trip to Mars in around 180 days about two months less than it took the spacecraft carrying RAD and Curiosity as one way of keeping down radiation exposure and making the journey a little less hazardous. (PNA/RIA Novosti) | 0.823931 | 3.151171 |
US, WASHINGTON (NEWS OBSERVATORY) — It has been revolving around our planet for three years, but this is noticed only now.
Asteroid 2020 CD3 was discovered on the night of February 15-16, 2020 by astronomers Theodore Pruyne and Kacper Wierzchos. Both researchers are part of the Catalan Sky Survey (CSS) – a project aimed at detecting near-Earth asteroids: including objects whose size exceeds 140 meters.
Some of the detected asteroids are classified as potentially dangerous – this means that their orbit allows them to approach the Earth at a distance that allows a collision, and their size is large enough to impact the planet, causing great damage.
Upon detection of 2020, CD3 had a 20th magnitude magnitude. It was captured by the Earth’s gravitational field and became a temporary satellite of our planet about three years ago. An asteroid is a carbon body with a diameter of 1.9 to 3.5 meters.
BIG NEWS (thread 1/3). Earth has a new temporarily captured object/Possible mini-moon called 2020 CD3. On the night of Feb. 15, my Catalina Sky Survey teammate Teddy Pruyne and I found a 20th magnitude object. Here are the discovery images. pic.twitter.com/zLkXyGAkZl
— Kacper Wierzchos (@WierzchosKacper) February 26, 2020
Despite the fact that the number of such objects in the Earth’s orbit can be measured in thousands, they are extremely difficult to detect due to their small size. In addition, most asteroids pass by our planet or burn out in its atmosphere. Computer modeling in 2012 showed that out of 10 million virtual asteroids, only 18 thousand fall into near-Earth orbit.
The main distinguishing feature of the 2020 CD3 was that it can be considered the second currently known temporary Earth satellite. The first such object was the asteroid 2006 RH120, which “accompanied” our planet for 18 months – from 2006 to 2007.
Here's an animated GIF of our new mini-moon 2020 CD3, discovered by @WierzchosKacper. Rotating frame keeps the Earth/Sun line stationary. Orbital elements courtesy of IUA MPEC. https://t.co/dok3jn3G9hhttps://t.co/x1DXWLq2vm pic.twitter.com/O3eRaOIYjB
— Tony Dunn (@tony873004) February 26, 2020
Such mini-moons are extremely promising for research. Sending spaceships to asteroids is expensive and time-consuming, and often requires overcoming vast distances. If the asteroid simply rotates around the Earth, it is much easier to get to it. However, in the case of 2020, CD3 may already be too late: if the researchers’ estimate is correct, the temporary satellite will leave the Earth’s orbit by April.
Contact us: [email protected]
Article is written and prepared by our foreign editors from different countries around the world – material edited and published by News Observatory staff in our US newsroom. | 0.855809 | 3.113812 |
by Stephen Wilde
In his latest article for CO2Sceptics.Com, Stephen Wilde establishes that the correct description of the Earth’s climate system is that of a pair of in line (series) electrical resistors of hugely different sizes with each being independently variable.
Additionally the weather systems provide a variable air flow across them and the hydrological cycle provides a variable water cooling system. All observed atmospheric changes fit within the parameters of that system with no climate warming possible from any changes in greenhouse gas concentrations.
That is the critical climate question and the one that I have agonised over most because even if human CO2 only increased the global air temperature permanently by a small amount then over a long enough period of time the effect would accumulate and could be dangerous.
In my various articles to date I have generally accepted in principle that a warming effect would occur but formed the conclusion and expressed the view that any such increase would take many centuries to be noticeable by which time humanity will have solved it’s energy problems or have destroyed itself by other means.
However, over time I have come across more and more opinions that the greenhouse effect of the air is not only wrongly described but that also there may be no such thing.
What is certain is that the Earth has a specific temperature although there are serious problems measuring it because one then has to consider the entire planet, not just the air.
Generally, for climate purpose, the Earth’s temperature is regarded as the average temperature of the air at any given moment and much scientific effort has been put into ascertaining what it is and how the real world arrives at that temperature for the air.
There are many diagrams and theories that try to balance the inputs and outputs but they are all setting out long term averaged estimates that do not accommodate the changes that occur over time.
Climate models attempt to deal with changes but in my opinion they are woefully incomplete and serve only to be sources of alarm rather than accurate information.
A better description ?
The Earth is at a temperature warmer than it would be if it had no atmosphere.
The same applies to the other planets.
It is implied by some AGW (Anthropogenic Global Warming) proponents that the proportion of CO2 in the air is a critical determinant of temperature but both Venus and Mars have over 90% of their air as CO2 yet their temperatures are very different. Thus I prefer the idea that overall atmospheric density (including air, any surface liquids and any suspended particulates) is the primary determinant with composition being significant but a secondary issue.
The distance from the sun is not such a major factor as regards Venus Earth and Mars.
I have previously conceded the view that the temperature of a planet is a result of the delay in solar energy passing through the planetary system however it is constituted for a particular planet and that is consistent with standard ‘greenhouse’ theory.
Hence I see it as being clearer to regard a planet and in particular it’s atmosphere (in our case air AND water) as a form of ‘resistor’ in the same way as an electrical resistor will delay the current passing through it and thereby generate heat.
The interesting thing about that analogy of a resistor is that what matters, is both the total volume of energy being put through the resistor (the electric current/flow of solar energy) AND the efficiency of the resistor in slowing down the passage of energy.
I do not doubt that the greenhouse (resistor) effect does exist and that it causes a delay in the transmission of energy with consequent heating. However the temperature of the air around the Earth is set by the combination of both the power of the solar energy reaching the Earth (the electricity supply) and the greenhouse effect (or rather the resistor effect) of the entire atmosphere and at this point readers need to recall my earlier contention that for greenhouse (resistor) purposes the oceans must be included as part of the ‘atmosphere’. The truth is that the Earth’s atmosphere for the purposes of any resistor effect is comprised of both air and water. Even in the air, water, in vapour form, is a substantial constituent.
The oceans are far more important than the air in causing that resistance on Earth. The proportion of the resistor effect contributed by the air is miniscule.
Now, if the total energy input remains the same then the only way of affecting the temperature permanently via the atmospheric resistor effect (both air and oceans) would be either by increasing the total atmospheric density (including the density of the oceans) or by increasing the proportion of gases in the air that have a stronger resistor effect such as CO2. Keep in mind that the contribution of the air to the entire effect is miniscule let alone the human portion.
The action of CO2 and other such gases does not add extra heat energy to the air. It just further increases the length of time that the heat energy remains in the air before it escapes to space. This is important for what I say later.
Many who fear AGW seem to think that the CO2 effect actually generates new heat that can accumulate within the air to dangerous effect. That is not so. It is just a delaying effect whereby the surface temperature increases until the increase in surface/space temperature differential in turn increases the rate of radiation to space and a new but higher temperature equilibrium is reached. Note that even if such a change in the temperature equilibrium does occur it will not be significant in practical terms from just CO2 and especially not from just human CO2. I explain why later in this article.
As far as I know all the calculations about the anticipated warming effect of more CO2 in the air ignore the massively greater resistor effect of the oceans so that the contribution of the CO2 to the total resistor effect is grossly overstated.
Up to this point I have taken the other possible inputs as stable but the reality is that they are not stable. Over the longer term the sun varies (there is uncertainty as to how much) and in the medium term the oceans vary much more than we previously thought possible in that they can act as net absorbers or net emitters of previously acquired solar energy for decades at a time.
I have already made it clear elsewhere that the additional resistor effect of human CO2 would be insignificant in relation to that from the rest of the air and the oceans together with the varying solar and oceanic heating and cooling effects but we still need to know for sure whether it is significant at all over periods of less than several hundred years because that may be the time we need to solve our energy, pollution, resource and population problems.
The point of this article:
What if there is a mechanism whereby the small amount of extra warmth from human CO2 could be eliminated naturally?
I have likened the action of the Greenhouse Effect in the air to an electrical resistor.
I have looked at the situation where the energy supply is constant.
The amount of warmth or heat retained in the wire of an electrical resistor also depends on the flow of air past it. The faster the air flow the lower the temperature at which the resistor will stabilise.
Thus it is possible for an increasingly efficient resistor (increasing greenhouse gases in the air) to stay at the same temperature provided there is a mechanism to dispose of the extra heat being generated as the efficiency of the resistor increases. It is important that the heat removal mechanism be able to ramp up in line with the increasing efficiency of the resistor.
If it does so then the resistor will not have any greater heating effect on anything around it as a result of it’s increased efficiency due to the fact that the increase in heat is being drawn away.
The CO2 and other greenhouse gases in the atmosphere are like a resistor (as are the oceans), not a greenhouse or a blanket as already explained in this earlier article:
As I describe in that article the weather systems on Earth (primarily the jet streams and the high pressure cells either side of them) ramp up their thermal efficiency in tune with the scale of any positive or negative energy input changes from any source including that from human CO2. Just like increasing or decreasing the flow of air across a resistor.
Shifting large volumes of air towards the poles increases radiation of energy to space thus neutralising any warming of the air and shifting large volumes of air towards the equator draws heat from sunshine and oceans thus neutralising any cooling of the air.
The air can only push energy towards space or draw it from the oceans. Air cannot draw energy from space or push it into the oceans.
At this point I should mention the vast energy transfer potential of the latent heats of evaporation and condensation. Huge quantities of energy are taken from water surfaces by evaporation then dumped higher up in the air by condensation to accelerate the expulsion of energy to space. That process is highly variable in scale and speed and is intimately linked to the air circulation that drives weather and climate. It is that process which gives the weather systems an overwhelming power to vary quickly in response to any imbalance between energy flowing into the air from the oceans and into space from the air.
Whether the air warms or cools the weather systems change to cancel it out.
Thus there does seem to be a mechanism whereby the warming effect from human CO2 (indeed all greenhouse gases) could be removed naturally as it arises. The weather systems accelerate the expulsion of the additional energy to space in order to return the energy inputs and outputs of the air to balance.
Greenhouse gases do not create extra heat. Their only effect is to delay it’s loss to space so if another process such as a change in the weather systems accelerates the loss of energy to space the effect of the extra greenhouse gases is negated.
It follows that an increase in CO2, water vapour or any other greenhouse gas may not increase any equilibrium temperature of the air because the weather systems change as necessary to redistribute the available energy in the system and accelerate the loss of energy to space. The weather systems seem to be an additional highly efficient and infinitely variable energy dispersal system imposing the temperature SET BY THE OCEANS on the air above it.
Due to that effect of the weather systems acting in conjunction with the hydrological cycle the air does not establish any specific temperature on it’s own, nor can it force a change of temperature on the oceans.
A change in the absorption characteristics of the air would have no temperature effect because it would immediately be eliminated by the adjustment in the weather systems to leave the air temperature, set by the oceans, unchanged.
Note that any equilibrium temperature of the whole planet dictated by the resistor effect and the energy flow from the sun is not the same as the sea surface temperatures or the surface air temperatures. The air and the sea surfaces conduct their own complex dance around the planetary temperature equilibrium and no doubt the planetary temperature equilibrium itself constantly dances around with the influence of other variables. Human CO2 would come nowhere in such a large and complex ever varying scenario.
However, despite all that, the weather systems combined with the hydrological cycle and the global air circulation guided by the sea surface temperatures do provide reasonable overall stability for eons at a time by neutralising many potentially disruptive natural and biologically induced variables affecting air temperature.
It is true that a permanent increase in greenhouse gases or a permanent effect from any other input will result in a permanent shift of the jet streams and the air pressure systems but they vary so much from energy increases or decreases from other causes and the chaotic variability of weather that the effect from human CO2 would be insignificant and in any event the temperature change overall would be neutralised whatever the reason for the change.
In fact there may be no such thing as any specific temperature of the air attributable to any particular greenhouse gas or other characteristic of the air because the weather systems always strive to keep the energy budget of the air balanced. The average surface air temperature is always tied to the average sea surface temperature so that the weather systems render any greenhouse warming process in the air ineffective and then leave the oceanic influence in unchallenged control.
The observed changes in air temperature that we notice and measure occur during the process of equalisation and are fully explicable by that process alone.
Such oceanic temperature as now subsists would probably be a historical inheritance from a long past state possibly at the end of the last ice age when it was reset by a combination of changed energy throughput from the sun plus the resistor effect of the oceans and air combined with the then state of the air circulation. The temperature of the entire body of all the oceans can only be changed by truly huge astronomic or geological causes acting suddenly or over millennia. Nothing that humans could ever do (apart from nuclear Armageddon) could ever come close.
Variations in the resistor effect from changes in the air alone would be easily neutralised by the movement of the weather systems towards poles or equator as they continually work to equalise the energy budget of the air.
The energy budget in the oceans operates independently of the air because the sun/sea exchange of energy is so huge. Variations in the supply of heat from the oceans to the air are dealt with by the weather systems in the same way as variations in the resistor effect from changes in the air alone. Due to the hugely greater scale of the oceanic influence there is usually a period of rising or falling air temperatures while the weather systems go about their work of neutralising the variations in oceanic input. Sudden shocks to the system such as volcanic events will take more time to be neutralised.
If the energy budget of the air is maintained in balance by means of the weather systems neutralising changes in the power of the resistor effect in the air alone (more CO2) and changes in energy received from the oceans (ocean cycles) then the only remaining factor requiring consideration at any particular time is total throughput of energy from the sun (the electric current in the resistor analogy).
Most of the time sun and ocean cycles (even those in individual oceans) work against one another and, fortunately they are not usually all in the same phase for long. If they acted in phase for long periods (say, hundreds of years) then in combination sun and oceans could make huge climatic changes as the weather systems strained to contain them.
1) It is proposed that the temperature of the whole atmosphere (air and water) is set by a combination of total energy throughput from the sun and the length of delay in the transmission of that energy through the resistor effect of the oceans and air but the oceans provide by far the dominant resistor effect and the properties of the air are insignificant in comparison.
2) If minor changes in the air attempt to make the air temperature alone diverge from that equilibrium then the weather systems change to modify the energy flow and in due course restore the surface air temperature to match the sea surface temperature set by the oceans.
3) A change in the greenhouse or other energy characteristics of the air is prevented from changing the temperature of the air as long as it is within the power of the weather systems to address it. The power of the weather systems is well able to cope with large variations in oceanic energy output and the variations in the power of the greenhouse effect in the air arising from natural changes in global humidity. Any human effect is insignificant in comparison.
4) The speed and efficiency of the weather and air circulation process stops the average global surface air temperature from ever diverging significantly or for long from the average global ocean surface temperatures. By preventing any persistent build up of temperature differential between air and water it also prevents any changes in air temperature affecting the temperature of the oceans and thereby changing the air temperature by indirect means. Even if the system did not prevent that entirely it would take many thousands of years to have any measurable effect on the oceans at all due to the huge density differential between air and water and the volume of water involved.
5) There are three categories of climate variation:
a) Chaotic temporary variation otherwise known as weather.
b) Changes in overall energy input and energy output involving the air alone (from changes in the quantity of greenhouse gases or normal range solar and oceanic variations) that are neutralised by the circulation changes in the air that I have described. Whilst the process is occurring we will observe increases or decreases in air temperatures and movement of the weather systems towards the poles if a warming tend is being neutralised or towards equator if a cooling trend is being neutralised.
c) Changes in overall energy input and energy output affecting the oceans AND the air that cannot be neutralised by the circulation changes in the air so that they result in major climate shifts such as those between glacial and interglacial epochs. It seems likely that the temperature of the oceans is only changed significantly as a result of events on a very large astronomic or geological scale. Events of a lesser scale leave the air circulation movements in a position to maintain the current temperature both in oceans and air.
6) The addition of extra CO2 by humans would be in category 4b and well within the parameters of the system. Additionally the effect of increasing human CO2 would be slow and incremental so that there would be no lag whilst the systems in the air adjust to it. We would not expect to see any effect on weather or climate other than that the air circulation patterns would be in very slightly differing (but still ever changing) positions than if we had made no difference at all. The difference would be imperceptible amongst the normal climate chaos and the much larger changes caused by solar and oceanic variability.
On the basis of the above I suggest that our extra CO2 emissions make no difference to the global air temperature let alone the temperature equilibrium of the entire planet or even the oceans and an imperceptible difference to the weather systems.
The effect on the temperature of the atmosphere by a human contribution of many multiples of the current CO2 level would be akin to a fly hitting the windscreen of a moving truck.
In the above narrative I have treated the Earth as if it is a single entity akin to one electrical resistor.
It is perhaps helpful to instead regard it as two separate resistors, the oceans being one and the air another.
The efficiency of each resistor varies independently because each has it’s own set of internal circulations, the ocean cycles in the seas and the weather systems in the air.
Those circulations change the efficiency (as resistors) of their respective materials separately although the air follows the lead of the oceans.
Thus, when the ocean circulations increase the resistor efficiency of the oceans by slowing the release of energy into the air then the air follows by increasing it’s own resistor efficiency by exposing less equatorial air to space. It does that by means of the weather systems moving towards the equator and thereby reducing the size of the equatorial air mass.
When the ocean circulations reduce the resistor efficiency of the oceans by increasing the release of energy into the air then the air follows by exposing more equatorial air to space. It does that by means of the weather systems moving towards the poles and thereby increasing the size of the equatorial air mass.
However the different densities of the oceans and the air make a very large difference to the outcome of the two types of circulation change.
In the case of the oceans the circulation changes are very slow. In the case of the Pacific Ocean it seems that each positive (energy emitting) stage and each negative (energy absorbing) stage can last 30 years making a total cycle of 60 years for the Pacific alone. A complete planetary oceanic cycle involving all the separate ocean cycles would take longer and it seems that all the ocean cycles act out of phase for most of the time and so further complicate the issue.
In the case of the air the circulation changes are very quick. The commencement of changes would be immediate upon a sea surface temperature change being initiated. It seems to take a few months for the jet streams and pressure systems to move noticeably and a few years for them to move substantial latitudinal distances.
The movement of pressure systems is irregular both in latitude and longitude because of the underlying chaotic behaviour of the weather systems but move they clearly do.
It is the speed of the response in the air as compared to the slowness of ocean changes that enables the air to cope with the oceanic changes and thereby keep the temperature of the air and the vigour of the weather systems within bounds amenable to us as inhabitants of the planet.
There is of nevertheless a time lag between the increase or decrease in energy flow from the oceans and the ability of the atmosphere to restore the equilibrium. The length of the lag is related to the scale of the change in oceanic energy emission or absorption and the length of time it takes for the oceanic change to be completed. Bear in mind that the oceanic change is itself irregular as witness the presence of both El Nino and La Nina episodes in both positive and negative phases of the Pacific Decadal Oscillation (PDO).
We observe changing air temperatures together with movements of the weather systems towards the poles or towards the equator during those periods of transition when the air is catching up with the ocean surface changes whether they be warming or cooling.
Additionally it is the speed and flexibility of the circulations in the air that enable it to deal quickly with any other change in resistor efficiency which is limited to the air such as a change in the quantity of greenhouse gases.
Due to the surface air temperature being tied to the sea surface temperature any change in the resistor efficiency of the air will attempt to prevent that equilibrium between sea and air.
It cannot do so because the sea surface temperature will always dominate and so the change in the resistor efficiency of the air can only be accommodated by a change in the air, not by a change in the ocean. Just like an electrical resistor the flow of energy is one way only.
The air responds to a change in it’s own resistor efficiency by changing it’s own circulation patterns to again meet the requirement that the surface air temperature and the sea surface temperature be the same on average globally.
The oceans and the air can be regarded as two separate flywheels with the relative sizes represented by their respective densities and volumes. The small one cannot move the large one but the large one can make the small one move very fast indeed.
It is that disproportionate relationship which makes the air so flexible in neutralising even large changes in the energy output of the oceans. The air can work faster and faster as necessary by moving the weather systems ever closer to the poles or the equator. There is a limit but only catastrophic events will break the system and establish a new equilibrium. Extra greenhouse gases would never be enough. It has to be something big enough to change the average temperature of the entire body of all the oceans.
So, again, any increase in greenhouse gases will result not in a change in air temperature but an imperceptible shift in the air circulation patterns.
Now, how do we clean up that squashed fly of AGW theory?
Addendum; The Ocean Skin Effect:
This effect represents the only attempt I am aware of whereby AGW proponents try to get round the problem of having to warm up the oceans before one can significantly warm up the air.
The idea is that instead of warming air the extra CO2 warms just a top layer of molecules on the ocean surface, known as the ocean skin.
The warmer skin then alters the temperature profile just below the surface and reduces the normal flow of energy from ocean to air. Heat is then supposed to build up in the oceans that then warm the atmosphere.
The problem for that idea is that even if it is possible the reduced energy flow from ocean to air merely mimics on a miniscule scale what happens naturally when a negative ocean cycle reduces the flow of energy from ocean to air.
In both cases the air circulation responds in exactly the same way to balance the energy budget of the air.
The weather systems move towards the equator to allow the polar air north of the jet streams to cover a larger oceanic area and thereby draw more heat from the oceans to replace any energy deficit.
A self stabilising system which is as well capable of neutralising any ocean skin effect as it is capable of neutralising negative ocean cycles, positive ocean cycles and any warming of the air by any increase in greenhouse gases. File attachment: Do More Greenhouse Gases Raise The Earths Temperature.pdf | 0.821097 | 3.056823 |
Quarter* ♎ Libra
Moon phase on 22 June 2083 Tuesday is Waxing Crescent, 7 days young Moon is in Virgo.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 7 days on 15 June 2083 at 09:37.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠23° of ♍ Virgo tropical zodiac sector.
Lunar disc appears visually 1.3% wider than solar disc. Moon and Sun apparent angular diameters are ∠1912" and ∠1888".
Next Full Moon is the Strawberry Moon of June 2083 after 7 days on 29 June 2083 at 16:51.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 7 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 1032 of Meeus index or 1985 from Brown series.
Length of current 1032 lunation is 29 days, 14 hours and 17 minutes. It is 1 hour and 26 minutes longer than next lunation 1033 length.
Length of current synodic month is 1 hour and 33 minutes longer than the mean length of synodic month, but it is still 5 hours and 30 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠203.8°. At the beginning of next synodic month true anomaly will be ∠232°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
9 days after point of apogee on 12 June 2083 at 22:19 in ♉ Taurus. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 5 days, until it get to the point of next perigee on 28 June 2083 at 06:42 in ♐ Sagittarius.
Moon is 374 943 km (232 979 mi) away from Earth on this date. Moon moves closer next 5 days until perigee, when Earth-Moon distance will reach 360 069 km (223 737 mi).
3 days after its descending node on 19 June 2083 at 01:15 in ♌ Leo, the Moon is following the southern part of its orbit for the next 9 days, until it will cross the ecliptic from South to North in ascending node on 1 July 2083 at 19:10 in ♒ Aquarius.
18 days after beginning of current draconic month in ♒ Aquarius, the Moon is moving from the second to the final part of it.
7 days after previous North standstill on 15 June 2083 at 05:35 in ♊ Gemini, when Moon has reached northern declination of ∠26.886°. Next 6 days the lunar orbit moves southward to face South declination of ∠-26.916° in the next southern standstill on 28 June 2083 at 15:42 in ♐ Sagittarius.
After 7 days on 29 June 2083 at 16:51 in ♑ Capricorn, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.165303 |
Astronomers have identified a new class of cosmic explosions that are more powerful than supernovae but considerably weaker than most gamma-ray bursts. The discovery strongly suggests a continuum between the two previously-known classes of explosions. Although the burst was the closest gamma-ray burst to Earth ever studied (all the others have been several billion light-years away), researchers noticed that the explosion was extremely faint–releasing only about one-thousandth of the gamma rays of a typical gamma-ray burst. However, the burst was also much brighter than supernovae explosions, which led to the conclusion that a new type of explosion had been found.
Gamma-ray burst of December 3 was a new type of cosmic explosion
Astronomers have identified a new class of cosmic explosions that are more powerful than supernovae but considerably weaker than most gamma-ray bursts. The discovery strongly suggests a continuum between the two previously-known classes of explosions.
In this week’s issue of Nature, astronomers from the Space Research Institute of the Russian Academy of Sciences and the California Institute of Technology announce in two related papers the discovery of the explosion, which was first detected on December 3, 2003, by the European-Russian Integral satellite and then observed in detail at ground-based radio and optical observatories. The burst, known by its birthdate, GRB031203, appeared in the constellation Puppis and is about 1.6 billion light-years away.
Although the burst was the closest gamma-ray burst to Earth ever studied (all the others have been several billion light-years away), researchers noticed that the explosion was extremely faint–releasing only about one-thousandth of the gamma rays of a typical gamma-ray burst. However, the burst was also much brighter than supernovae explosions, which led to the conclusion that a new type of explosion had been found.
Both supernovae and the rare but brilliant gamma-ray bursts are cosmic explosions marking the deaths of massive stars. Astronomers have long wondered what causes the seemingly dramatic differences between these events. The question of how stars die is currently a major focus of stellar research, and is particularly directed toward the energetic explosions that destroy a star in one cataclysmic event.
Stars are powered by the fusion (”burning”) of hydrogen in their interiors. Upon exhaustion of fuel in the interior, the core of massive stars collapse to compact objects–typically a neutron star and occasionally a black hole. The energy released as a result of the collapse explodes the outer layers, the visible manifestation of which is a supernova. In this process, new elements are added to the inventory of matter in the universe.
However, this nuclear energy may be insufficient to power the supernova explosions. One theory is that additional energy is generated from the matter falling onto the newly produced black hole. Many astronomers believe that this is what powers the luminous gamma-ray bursts.
But the connection between such extreme events and the more common supernovae is not yet clear, and if they are indeed closely related, then there should be a continuum of cosmic explosions, ranging in energy from that of ”ordinary” supernovae to that of gamma-ray bursts.
In 1998, astronomers discovered an extremely faint gamma-ray burst, GRB 980425, coincident with a nearby luminous supernova. The supernova, SN 1998bw, also showed evidence for an underlying engine, albeit a very weak one. The question that arose was whether the event, GRB 980425/SN 1998bw, was a ”freak” explosion or whether it was indicative of a larger population of low-powered cosmic explosions with characteristics in between the cosmological gamma-ray bursts and typical supernovae.
”I knew this was an exciting find because even though this was the nearest gamma-ray burst to date, the gamma-ray energy measured by Integral is one thousand times fainter than typical cosmological gamma-ray bursts,” says Sergey Sazonov of the Space Research Institute, the first author of one of the two Nature papers.
The event was studied in further detail by the Chandra X-Ray Observatory and the Very Large Array, a radio telescope facility located in New Mexico.
”I was stunned that my observations from the Very Large Array showed that this event confirmed the existence of a new class of bursts,” says graduate student Alicia Soderberg, who is the principal author of the other Nature paper. ”It was like hitting the jackpot.”
There are several exciting implications of this discovery, including the possible existence of a significant new population of low-luminosity gamma-ray bursts lurking within the nearby universe, said Shrinivas Kulkarni, who is the MacArthur Professor of Astronomy and Planetary Science at Caltech and Soderberg’s faculty adviser.
”This is an intriguing discovery,” says Kulkarni. ”I expect a treasure trove of such events to be identified by NASA’s Swift mission scheduled to be launched this fall from Cape Canaveral. I am convinced that further discoveries and studies of this new class of hybrid events will forward our understanding of the death of massive stars.” | 0.917049 | 4.004222 |
Quaking after a collision
Extremely rare survivor of star collision discovered
What happens when two stars that were previously orbiting each other collide? How can such a huge explosion leave more than gas and radiation behind – and in fact even leave both partners intact, albeit in a different form? A team of astronomers1) from Great Britain, Germany and Spain is now hoping to find out what really happens during a stellar collision by examining an oscillating specimen, which is very rare in our galaxy. ‘There is an abundance of data that has told us a lot about the binary star system,’ said Prof. Dr. Ulrich Heber of FAU, who was involved in the analysis. The results were published in the journal Nature on 27 June 20132).
The researchers were actually searching for extrasolar planets when they caught sight of the exotic star. Project leader Dr. Pierre Maxted and his colleagues then decided to use one of the European Southern Observatory’s (ESO) high-speed cameras in Chile3). This led to the discovery that the brightness is fluctuating in a unique way, caused by the star’s oscillating. This is the first time such a thing has been proven in a celestial body of this kind.
This lends credence to the collision hypothesis, which says that a momentous collision can occur in a binary star system if one of the partners inflates to a red giant. Our sun is facing a similar fate: its radius will grow more than hundredfold when its supply of hydrogen, the current nuclear fuel, runs out. But unlike many other stars, it was not born as a twin. As soon as one of the siblings reaches the giant star phase in its life cycle, collisions between the expanded star and its smaller companion can occur. This cannot be compared with the collision of two rocks, however: the orbit of the secondary star, now surrounded and slowed down by the inflated shell, becomes ever smaller until a massive release of energy explodes away up to 90 percent of the red giant’s mass. Computer simulations predict that the remaining star has not only become very light, but that it now has highly unusual characteristics.
Unfortunately such stars are rare, which is why the team of astronomers was thrilled to discover this misfit. The footage from the high-speed camera ULTRACAM showed tiny fluctuations in brightness. They are caused by sonic waves spreading through the star’s interior. Such pulsations can be found in our sun as well as many other stars and undergo regular cycles. In our sun and in the new fluctuating star, such a cycle is about five minutes long. The sonic waves penetrate deep into the star’s interior, almost to its centre. Similar to how seismic waves can be used to explore the Earth’s interior, the internal structure of the star can be sounded out using the appropriate physical-numeric computer models. This requires more accurate measurements, which the team plans on carrying out at the European Southern Observatory.
‘We have even been able to weigh the two stars,’ said Prof. Dr. Ulrich Heber. ‘What we found out was that one of them is much too light – a clear indicator of its companion tearing away the majority of its mass in a collision. Now we can find out why stars even survive such collisions.’
Further information on the new star, an audio clip and an animated visualisation can be found at www.astro.keele.ac.uk
1) The discovery team consist of: Dr. Pierre Maxted (project leader) and Dr. Barry Smalley (Keele University, UK); Dr. Aldo Serenelli (CSIC-IECC, Spain); Andrea Miglio (University of Birmingham, UK); Prof. Thomas Marsh and Dr. Elmé Breedt (University of Warwick, UK), Prof. Ulrich Heber and Veronika Schaffenroth (University of Erlangen-Nürnberg), Prof. Vikram Dhillon and Dr. Stuart Littlefair (University of Sheffield, UK), Dr. Chris Copperwheat (Liverpool John Moores University, UK)
2) DOI: 10.1038/nature12192
3) The British high-speed camera ULTRACAM at the 3.6-metre New Technology Telescope at the European Southern Observatory (ESO). ULTRACAM website: http://www.vikdhillon.staff.shef.ac.uk/ultracam
Prof. Dr. Ulrich Heber
Phone: +49 (0)951 9522214 | 0.853068 | 3.934984 |
- 2020-05-20 14:30:06
- 己被围观 次
The sun is an ordinary star, which has spent about half of its main sequence career on the H-R diagram. It is a hot gas (plasma) sphere with a mass of 19.91 billion tons (about 330000 times the mass of the earth) and a diameter of 1.392 million km (about 109 times the diameter of the earth). Its average density is 1.4 times that of water, but it implies a wide range of density, from the ultra-high density core to the thin outer layer.
As a star, the overall appearance of the sun is 38.3 billion watts in luminosity and 4.8 in absolute magnitude. It is a yellow G2 dwarf with an effective temperature equal to 5800 degrees Kelvin. The average distance between the sun and the earth in orbit is 149597870km (499.005 light seconds or 1 astronomical unit). By mass, it consists of 71% hydrogen, 26% helium and a small amount of heavy elements. The angular diameter of the solar circle in the sky is 32 minutes, which is very close to the angular diameter of the moon seen from the earth. It is a wonderful coincidence (the diameter of the sun is about 400 times the diameter of the moon and the distance from us is just 400 times the distance between the earth and the moon), which makes the solar eclipse look particularly spectacular.
As the sun is much closer to us than other stars, its apparent magnitude reaches - 26.8, making it the brightest object on earth. The sun rotates once every 25.4 days (average period; the equator rotates faster than high latitude), and once every 200 million years around the center of the galaxy. The sun is slightly flat due to rotation, 0.001% different from the perfect sphere, which is equivalent to 6km difference between the equatorial radius and the polar radius (the difference is 21km for the earth, 9km for the moon, 9000km for Jupiter and 5500km for Saturn). | 0.851371 | 3.492264 |
‘Oumuamua, the rocky object identified as the first confirmed interstellar asteroid, originates from a binary star system and was most probably ejected during the formation of planets.
Binary systems are very efficient at ejecting rocky objects, and that a sufficient number of them exist, according to a new study published in the journal Monthly Notices of the Royal Astronomical Society: Letters.
“It’s really odd that the first object we would see from outside our system would be an asteroid, because a comet would be a lot easier to spot and the Solar System ejects many more comets than asteroids,” said lead author Dr Alan Jackson, a postdoc at the Centre for Planetary Sciences at the University of Toronto Scarborough in Ontario, Canada, who specializes in planet and solar system formation.
Jackson and his team determined that ‘Oumuamua probably came from a system with a relatively hot, high mass star since such a system would have a greater number of rocky objects closer in.
Based on ‘Oumuamua’s trajectory and speed, an eccentricity of 1.2 – classifies its path as an open-ended hyperbolic orbit – and such a high speed meant it was not bound by the gravity of the Sun.
Interesting is that ‘Oumuamua’s orbit has the highest eccentricity ever observed in an object passing through our Solar System
Cucumber-Shaped Asteroid ‘Oumuamua’ Had A Violent Past – Researchers Say
‘Oumuamua, which is Hawaiian for ‘scout’, was first spotted by the Haleakala Observatory in Hawaii on 19 October 2017. With a radius of 200 meters and travelling at a blistering speed of 30 kilometers per second, at its closest it was about 33,000,000 km from Earth.
When it was first discovered researchers initially assumed the object was a comet, one of countless icy objects that release gas when they warm up on approaching the Sun.
But it didn’t show any comet-like activity as it neared the Sun, and was quickly reclassified as an asteroid, meaning it was rocky.
There are still many questions about ‘Oumuamua and planetary scientists like Jackson, hope to observe other objects like ‘Oumuamua and shed light on formation of planets in other star systems.
“The same way we use comets to better understand planet formation in our own Solar System, maybe this curious object can tell us more about how planets form in other systems.” | 0.911205 | 3.895502 |
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30° 4' *, and quite within reasonable limits of resemblance. But how does this agree with the longer period of 175 years before assigned? To reconcile this we must suppose that these 175 years comprise at least eight returns of the comet, and that in effect a mean period of 2F-875 must be allowed for its return. Now it is worth remarking that this period calculated backwards from 1843*156 will bring us upon a series of years remarkable for the appearance of great comets, many of which, as well as the imperfect descriptions we have of their appearance and situation in the heavens, offer at least no obvious contradiction to the supposition of their identity with this. Besides those already mentioned as indicated by the period of 175 years, we may specify as probable or possible intermediate returns, those of the comets of 1733 ?f, 1689 above-mentioned, 1559?, 1537fc 1515§, 1471, 1426, 1405-6, 1383, 1361, 13401|, 1296, 1274, 1230 f, 1208, 1098, 1056, 1034,1012',*,990?tt,925?,858??,684tt. 552, 530 §§, 421, 245 or 2471|||, 180Iff, 158. Should this view of the subject be the true one, we may expect its return about the end of 1864 or beginning of 1865, in which event it will be observable in the Southern Hemisphere both before and after its perihelion passage.*
• United States Gazette, May 29. 1843. Considering that all the observations lie near the descending node of the orbit, the proximity of the comet at that time to the sun, and the loose nature of the recorded observations, no doubt almost any given inclination might be deduced from them. The true test in such cases is not to ascend from the old incorrect data to elements, but to descend from known and certain elements to the older data, and ascertain whether the recorded phenomena can be represented by them (perturbations included) within fair limits of interpretation. Such is the course pursued by Clausen.
t P. Passage 1733-781. The great southern comet of May 17th seems too early in the year.
t P. P. 1536906. In January 15S7, a comet was seen in Pisces.
§ P. P. 1515-031. A comet predicted the death of Ferdinand the Catholic He died Jan. 23. 1515.
|| P.P. 1.14 0-031. Evidently a southern comet, and a very probable appearance.
1 P. P. 1230-656, was perhaps a return of Halley's.
** P. P. 1011-906. In 1012, a very great comet in the southern pnrt of the heavens. "Son eclat blessait les yeui." (Pingre Com£tographie, from whom all these recorded appearances are taken.)
ff P. P. 990031. "Comete fort epouvantable," tome year between 989 and 998.
}J P. P. 683 781. In 684, appeared two or three comets. Dates begin to be obscure.
§§ Two distinct comets (one probably the comet of Cassar and 1680) appeared in 530 and 531, the former observed in China, the latter in Europe.
HII P. P. 246-281; both southern comets of the Chinese annals. The year of one or other may be wrong.
«,«, P. P. 180-656. Nov6. *.o. 180. A southern comet of the Chinese annals.
(596.) M. Clausen, from the assemblage of all the observations of this comet known to him, has calculated elliptic elements which give the extraordinarily short period of 6*38 years. And in effect it has been suggested that a still further subdivision of the period of 21 "875 into three of 7'292 years would reconcile this with other remarkable comets. This seems going too far, but at all events the possibility of representing its motions by so short an ellipse will easily reconcile us to the admission of a period of 21 years. That it should only be visible in certain apparitions, and not in others, is sufficiently explained by the situation of its orbit.
(597.) We have been somewhat diffuse on the subject of this comet, for the sake of showing the degree and kind of interest which attaches to cometic astronomy in the present state of the science. In fact, there is no branch of astronomy more replete with interest, and we may add more eagerly pursued at present, inasmuch as the hold which exact calculation gives us on it may be regarded as completely established; so that whatever may be concluded as to the motions of any comet which shall henceforward come to be observed, will be concluded on sure grounds and with numerical precision ; while the improvements which have been introduced into the calculation of cometary perturbation, and the daily increasing familiarity of numerous astronomers with computations of this nature, enable us to trace their past and future history with a certainty, which at the commencement of the present century could hardly have been looked upon as attainable. Every comet newly discovered is at once subjected to the ordeal of a most rigorous enquiry. Its elements, roughly calculated within a few days of its appearance, are gradually approximated to as observations accumulate, by a multitude of ardent and expert computists. On the least indication of a deviation from a parabolic orbit, its elliptic
• Clausen, Astron. Nachr. No. 485.
elements become a subject of universal and lively interest and discussion. Old records are ransacked, and old observations reduced, with all the advantage of improved data and methods, so as to rescue from oblivion the orbits of ancient comets which present any similarity to that of the new visitor. The disturbances undergone in the interval by the action of the planets are investigated, and the past, thus brought into unbroken connexion with the present, is made to afford substantial ground for prediction of the future. A great impulse meanwhile has been given of late years to the discovery of comets by the establishment in 1840*, by his late Majesty the King of Denmark, of a prize medal to be awarded for every such discovery, to the first observer, (the influence of which may be most unequivocally traced in the great number of these bodies which every successive year sees added to our list,) and by the circulation of notices, by special letter f, of every such discovery (accompanied, when possible, by an cphemeris), to all observers who have shown that they take an interest in the enquiry, so as to ensure the full and complete observation of the new comet so long as it remains within the reach of our telescopes.
(598.) It is by no means merely as a subject of antiquarian interest, or on account of the brilliant spectacle which comets occasionally afford, that astronomers attach a high degree of importance to all that regards them. Apart even from the singularity and mystery which appertains to their physical constitution, they have become, through the medium of exact calculation, unexpected instruments of enquiry into points connected with the planetary system itself, of no small importance. We have seen that the movements of the comet of Encke, thus minutely and perseveringly traced by the eminent astronomer whose name is used to distinguish it, has afforded ground for believing in the presence of a resisting medium filling the whole of our system. Similar enquiries, prosecuted in the cases of other periodical comets, will extend, confirm, or modify our conclusions on this head. The per
* Sep the announcement or this institution in Astron. Nachr. No. 400.
turbations, too, which comets experience in passing near any of the planets, may afford, and have afforded, information as to the magnitude of the disturbing masses, which could not well be otherwise obtained. Thus the approach of this comet to the planet Mercury in 1838 afforded an estimation of the mass of that planet the more precious, by reason of the great uncertainty under which all previous determinations of that element laboured. Its approach to the same planet in the present year (1848) will be still nearer. On the 22d of November their mutual distance will be only fifteen times the moon's distance from the earth.
(599.) It is, however, in a physical point of view that these bodies offer the greatest stimulus to our curiosity. There is, beyond question, some profound secret and mystery of nature concerned in the phenomenon of their tails. Perhaps it is not too much to hope that future observation, borrowing every aid from rational speculation, grounded on the progress of physical science generally, (especially those branches of it which relate to the ajtherial or imponderable elements), may ere long enable us to penetrate this mystery, and to declare whether it is really matter in the ordinary acceptation of the term which is projected from their heads with such extravagant velocity, and if not impelled, at least directed in its course by a reference to the sun, as its point of avoidance. In no respect is the question as to the materiality of the tail more forcibly pressed on us for consideration, than in that of the enormous sweep which it makes round the sun in perihelio, in the manner of a straight and rigid rod, in defiance of the law of gravitation, nay, even of the received laws of motion, extending (as we have seen in the comets of 1680 and 1843) from near the sun's surface to the earth's orbit, yet whirled round unbroken; in the latter case through an angle of 180° in little more than two hours. It seems utterly incredible that in such a case it is one and the same material object which is thus brandished. If there could be conceived such a thing as a negative shadow, a momentary impression made upon the luminiferous octher behind the comet, this would represent in some degree the conception such a phenomenon irresistibly calls up. But this is not all. Even such an extraordinary excitement of the aether, conceive it as we will, will afford no account of the projection of lateral streamers; of the effusion of light from the nucleus of a comet towards the sun; and its subsequent rejection; of the irregular and capricious mode in which that effusion bas been seen to take place; none, of the clear indications of alternate evaporation and condensation going on in the immense regions of space occupied by the tail and coma, — none, in short, of innumerable other facts which link themselves with almost equally irresistible cogency to our ordinary notions of matter and force.
(600.) The great number of comets which appear to move in parabolic orbits, or orbits at least undistinguishable from parabolas during their description of that comparatively small part within the range of their visibility to us, has given rise to an impression that they are bodies extraneous to our system, wandering through space, and merely yielding a local and temporary obedience to its laws during their sojourn. What truth there may be in this view, we may never have satisfactory grounds for deciding. On such an hypothesis, our elliptic comets owe their permanent denizenship within the sphere of the sun's predominant attraction to the action of one or other of the planets near which they may have passed, in such a manner as to diminish their velocity, and render it compatible with elliptic motion. * A similar cause acting the other way, might with equal probability, give rise to a hyperbolic motion. But whereas in the former case, the comet would remain in the system, and might make an indefinite number of revolutions, in the latter it would return no more. This may possibly be the cause of the exceedingly rare occurrence of a hyperbolic comet as compared with elliptic ones.
(601.) All the planets without exception, and almost all the satellites, circulate in one direction. Retrograde comets, however, are of very common occurrence, which
* The velocity in an ellipse is always less than in a parabola, at equal distances from the sun ; in an hyperbola always greater. | 0.8179 | 3.584051 |
This is the first in a series of articles on ‘dark gravity’ that look at emergent gravity and modifications to general relativity. In my book Dark Matter, Dark Energy, Dark Gravity I explained that I had picked Dark Gravity to be part of the title because of the serious limitations in our understanding of gravity. It is not like the other 3 forces; we have no well accepted quantum description of gravity. And it is some 33 orders of magnitude weaker than those other forces.
I noted that:
The big question here is ~ why is gravity so relatively weak, as compared to the other 3 forces of nature? These 3 forces are the electromagnetic force, the strong nuclear force, and the weak nuclear force. Gravity is different ~ it has a dark or hidden side. It may very well operate in extra dimensions… http://amzn.to/2gKwErb
My major regret with the book is that I was not aware of, and did not include a summary of, Erik Verlinde’s work on emergent gravity. In emergent gravity, gravity is not one of the fundamental forces at all.
Erik Verlinde is a leading string theorist in the Netherlands who in 2009 proposed that gravity is an emergent phenomenon, resulting from the thermodynamic entropy of the microstates of quantum fields.
In 2009, Verlinde showed that the laws of gravity may be derived by assuming a form of the holographic principle and the laws of thermodynamics. This may imply that gravity is not a true fundamental force of nature (like e.g. electromagnetism), but instead is a consequence of the universe striving to maximize entropy. – Wikipedia article “Erik Verlinde”
This year, Verlinde extended this work from an unrealistic anti-de Sitter model of the universe to a more realistic de Sitter model. Our runaway universe is approaching a dark energy dominated deSitter solution.
He proposes that general relativity is modified at large scales in a way that mimics the phenomena that have generally been attributed to dark matter. This is in line with MOND, or Modified Newtonian Dynamics. MOND is a long standing proposal from Mordehai Milgrom, who argues that there is no dark matter, rather that gravity is stronger at large distances than predicted by general relativity and Newton’s laws.
In a recent article on cosmology and the nature of gravity Dr.Thanu Padmanabhan lays out 6 issues with the canonical Lambda-CDM cosmology based on general relativity and a homogeneous, isotropic, expanding universe. Observations are highly supportive of such a canonical model, with a very early inflation phase and with 1/3 of the mass-energy content in dark energy and 2/3 in matter, mostly dark matter.
1. The equation of state (pressure vs. density) of the early universe is indeterminate in principle, as well as in practice.
2. The history of the universe can be modeled based on just 3 energy density parameters: i) density during inflation, ii) density at radiation – matter equilibrium, and iii) dark energy density at late epochs. Both the first and last are dark energy driven inflationary de Sitter solutions, apparently unconnected, and one very rapid, and one very long lived. (No mention of dark matter density here).
3. One can construct a formula for the information content at the cosmic horizon from these 3 densities, and the value works out to be 4π to high accuracy.
4. There is an absolute reference frame, for which the cosmic microwave background is isotropic. There is an absolute reference scale for time, given by the temperature of the cosmic microwave background.
5. There is an arrow of time, indicated by the expansion of the universe and by the cooling of the cosmic microwave background.
6. The universe has, rather uniquely for physical systems, made a transition from quantum behavior to classical behavior.
“The evolution of spacetime itself can be described in a purely thermodynamic language in terms of suitably defined degrees of freedom in the bulk and boundary of a 3-volume.”
Now in fluid mechanics one observes:
“First, if we probe the fluid at scales comparable to the mean free path, you need to take into account the discreteness of molecules etc., and the fluid description breaks down. Second, a fluid simply might not have reached local thermodynamic equilibrium at the scales (which can be large compared to the mean free path) we are interested in.”
Now it is well known that general relativity as a classical theory must break down at very small scales (very high energies). But also with such a thermodynamic view of spacetime and gravity, one must consider the possibility that the universe has not reached a statistical equilibrium at the largest scales.
One could have reached equilibrium at macroscopic scales much less than the Hubble distance scale c/H (14 billion light-years, H is the Hubble parameter) but not yet reached it at the Hubble scale. In such a case the standard equations of gravity (general relativity) would apply only for the equilibrium region and for accelerations greater than the characteristic Hubble acceleration scale of (2 centimeters per second / year).
This lack of statistical equilibrium implies the universe could behave similarly to non-equilibrium thermodynamics behavior observed in the laboratory.
The information content of the expanding universe reflects that of the quantum state before inflation, and this result is 4π in natural units by information theoretic arguments similar to those used to derive the entropy of a black hole.
The black hole entropy is where A is the area of the black hole using the Schwarzschild radius formula and Lp is the Planck length, , where G is the gravitational constant, is Planck’s constant.
This beautiful Bekenstein-Hawking entropy formula connects thermodynamics, the quantum world and gravity.
This same value of the universe’s entropy can also be used to determine the number of e-foldings during inflation to be 6 π² or 59, consistent with the minimum value to enforce a sufficiently homogeneous universe at the epoch of the cosmic microwave background.
If inflation occurs at a reasonable ~ GeV, one can derive the observed value of the cosmological constant (dark energy) from the information content value as well, argues Dr. Padmanhaban.
This provides a connection between the two dark energy driven de Sitter phases, inflation and the present day runaway universe.
The table below summarizes the 4 major phases of the universe’s history, including the matter dominated phase, which may or may not have included dark matter. Erik Verlinde in his new work, and Milgrom for over 3 decades, question the need for dark matter.
Epoch / Dominated / Ends at / a-t scaling / Size at end
Inflation / Inflaton (dark energy) / seconds / (de Sitter) / 10 cm
Radiation / Radiation / 40,000 years / / 10 million light-years
Matter / Matter (baryons) Dark matter? / 9 billion light-years / / > 100 billion light-years
Runaway / Dark energy (Cosmological constant) / “Infinity” / (de Sitter) / “Infinite”
In the next article I will review the status of MOND – Modified Newtonian Dynamics, from the phenomenology and observational evidence.
E. Verlinde. “On the Origin of Gravity and the Laws of Newton”. JHEP. 2011 (04): 29 http://arXiv.org/abs/1001.0785
T. Padmanabhan, 2016. “Do We Really Understand the Cosmos?” http://arxiv.org/abs/1611.03505v1
S. Perrenod, 2011. Dark Matter, Dark Energy, Dark Gravity 2011 http://amzn.to/2gKwErb
S. Carroll and G. Remmen, 2016, http://www.preposterousuniverse.com/blog/2016/02/08/guest-post-grant-remmen-on-entropic-gravity/ | 0.802945 | 3.778159 |
Night sky puts on a meteor shower to celebrate Rosetta's closest approach to the sun
A firework display is often the finale of a celebratory event, something that many people can experience and enjoy at the same time. This week, the 9 – 14th August, we should be seeing a firework display with a difference: rather than sparks shooting from the ground upwards, they will be falling downwards. And there is actually something worth celebrating up there, as comet 67P/Churyumov-Gerasimenko simultaneously reaches its closest approach to the sun.
The Perseid meteor shower, which reaches its maximum on 12 August, is an annual event in the northern hemisphere which frequently garners media attention, mainly because it occurs in the middle of the summer holiday. A story about cosmic fireworks is a sure winner for a slow news day, especially given that people may be away from city lights, and able to see the night sky more clearly than usual.
Meteors, or shooting stars, are dust particles the size of sand grains that travel through the atmosphere, about 50 miles above the Earth's surface. They move fast – some 20-30 kilometres per second – and friction between the particle and the atmosphere at that speed causes them to heat up, emitting light. The grains aren't burning up, they are evaporating into a plasma, which exists for a split second, before extinguishing.
Nothing lands from a meteor. And neither do they go bang like a firework – the most they might do is sizzle a little bit – but you would have to be somewhere extremely quiet to hear them. A shooting star is generally white, but they can be coloured, mainly green or orange depending on their composition. Orange is from sodium, the same colour that stains the night sky in cities, with reflected light from street lights.
On most nights of the year, around six meteors per hour can be seen, assuming the skies are clear. These sporadic meteors emanate from random bits of dust from asteroids or comets. At certain times of the year, though, the count goes up to more like 100 meteors per hour. Such meteor showers or storms are connected with specific comets, which is why we are able to predict them.
The Perseids are associated with comet Swift-Tuttle, which takes 133 years to travel around our solar system. It was last at perihelion (its closest approach to the sun) in 1995. Each time the comet comes to the inner solar system, it sheds dust. Over time, this debris has built up, and is smeared out along the entire track of the orbit. Once a year, in August, the Earth's orbit crosses that of comet Swift-Tuttle, and dust from the comet is captured.
If you record a meteor shower, it seems as if all the tracks come from a single point – the radiant. For the Perseids, the radiant is in the constellation of Perseus, which is in the north-east part of the sky. The shooting stars aren't coming from Perseus, they just appear to be, in the same way that the parallel tracks of a railway line appear to converge as they disappear into the distance.
All eyes on 67P
At the same time that the Perseids are lighting up the night skies, 67P reaches its perihelion – the point at which its activity is expected to be at its highest. This is a prime focus of the Rosetta mission: the spacecraft has been travelling alongside 67P for a year, observing development of the comet's tail, how the nucleus has outgassed and where jets have formed.
Over the past few months we have been treated to amazing images of the nucleus, and the spacecraft has had to retreat further and further away from the comet as the amount of dust increased, causing a hazard to the navigation systems. I must make it clear that even though I have linked them in this column, the Perseid meteor shower is not connected with comet 67P or the Rosetta mission.
Over the coming year, Rosetta will watch as the comet moves away from the sun, causing the tail to die away and the surface to re-freeze. Then, the spacecraft will be able to get closer to the nucleus again. We should hear more from the Philae lander (assuming communications get sorted out), and see additional fantastic pictures of the comet's rugged surface.
What we probably won't see is a display of cometary fireworks from the Perseids. In the UK, at least, the prediction of a storm of shooting stars is almost inevitably the cue for a week of unbroken cloud. Still, if you are in the northern hemisphere, look to the north-east after midnight – and if you wish to wish upon a shooting star, I hope you manage to see at least one.
This story is published courtesy of The Conversation (under Creative Commons-Attribution/No derivatives). | 0.871091 | 3.801003 |
The Moon will be prominent in the dawn sky, rising at around midnight.
From Fairfield, it will be visible in the morning sky, becoming accessible around 01:13, when it rises to an altitude of 7° above your eastern horizon. It will then reach its highest point in the sky at 05:56, 39° above your southern horizon. It will be lost to dawn twilight around 06:52, 37° above your southern horizon.
Observing the Moon at last quarter
As it progresses through this cycle, it is visible at different times of day. At last quarter, it rises at around midnight, appears high in the sky by dawn, and sets at around midday. Click here for more information about the Moon's phases.
The period when the Moon shows half phase is ideal for observing the Moon with a pair of binoculars or a small telescope. The border between the light and dark portions of the Moon's disk is the best place to look for detail on its surface, because along this line, the Moon's surface is illuminated at a very shallow angle. As a result, mountains and crater rims cast long shadows which are very easy to see. An observer on the Moon would see the Sun on the horizon, casting long shadows just like the ones we see on Earth at sunrise and sunset.
At first quarter and last quarter, when the terminator line is down the middle of the Moon, it is best presented for view, without any foreshortening.
Although the Moon passes last quarter every month, it is more favourably placed in the pre-dawn sky at some times of year than others.
It appears high up in the pre-dawn sky around the autumn equinox, but much lower towards the horizon around the spring equinox.
This is because it always lies close to a line across the sky called the ecliptic. This marks the flat plane in space in which all of the planets circle the Sun. It is the line through the zodiacal constellations that the Sun follows through the year.
The altitude at which the Moon appears above the horizon at sunrise depends how steeply the line of the ecliptic is inclined to the horizon. If the plane of the ecliptic meet the horizon at a very shallow angle, the Moon will rise or set along a line which is almost parallel to the horizon, and a large separation from the Sun along this line would still only correspond to a very low altitude in the sky.
The inclination of the ecliptic plane to the horizon at Fairfield varies between 72° (sunrise at the autumn equinox) and 25° (sunrise at the spring equinox). On January 27, the ecliptic is inclined at 31° to the eastern dawn horizon, as shown by the yellow line in the planetarium view above, meaning that on this occasion the Moon is poorly placed for viewing from Fairfield.
The Moon's position
At the moment it reaches last quarter, the Moon's distance from the Earth will be 371,000 km. Its exact position will be as follows:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 31 May 2020|
9 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|27 Jan 2038||– Moon at Last Quarter|
|02 Feb 2038||– The Moon at perihelion|
|04 Feb 2038||– New Moon|
|09 Feb 2038||– The Moon at apogee| | 0.901567 | 3.724022 |
The European Space Agency's (ESA) Rosetta mission will come to a dramatic end on Friday, Sept. 30, with a controlled touchdown of the spacecraft on a region of comet 67P/Churyumov-Gerasimenko known for active pits that spew comet dust into space. Confirmation of the end of mission is expected at about 4:20 a.m. PDT (7:20 a.m. EDT). ESA is ending the mission due to the spacecraft's ever-increasing distance from the sun, which has resulted in significantly reduced solar power with which to operate the vehicle and its instruments.
Rosetta is an international mission led by ESA with instruments provided by its member states, and additional support and instruments provided by NASA.
"The European Space Agency's Rosetta Mission is a magnificent demonstration of what excellent mission design, execution, and international collaboration can achieve," said Geoff Yoder, acting associate administrator for NASA's Science Mission Directorate in Washington. "Being neighbors with a comet for more than two years has given the world invaluable insight into these beautiful nomads of deep space. We congratulate ESA on its many accomplishments during this daring mission."
The final hours of descent will enable Rosetta to make many once-in-a-lifetime measurements, including analyzing gas and dust closer to the surface than ever possible before, and taking very high-resolution images of the comet nucleus. The images will include views of the open pits of the Ma'at region, where the spacecraft is expected to make its controlled impact. Ma'at is home to several active pits more than 330 feet (100 meters) in diameter and 160 to 200 feet (50 to 60 meters) deep.
The walls of the pits exhibit intriguing lumpy structures about 3 feet wide (1 meter wide) called "goose bumps." Scientists believe those structures could be the signatures of early cometesimals that assembled to create the comet in the early phases of solar system formation. Rosetta will attempt to get its closest look yet at these fascinating structures on Sept. 30, when the spacecraft will target a point adjacent to a 430-feet-wide (130-meter), well-defined pit that the mission team has informally named Deir el-Medina.
"Rosetta will keep giving us data to the very end," said Bonnie Buratti, project scientist for the U.S. Rosetta project from NASA's Jet Propulsion Laboratory in Pasadena, California. "NASA's three instruments aboard Rosetta will be among those collecting data all the way down."
Those three NASA science instruments are: the Microwave Instrument for Rosetta Orbiter (MIRO); an ultraviolet spectrometer called Alice; and the Ion and Electron Sensor (IES). They are part of a suite of 11 science instruments on the orbiter.
MIRO was designed to provide data on how gas and dust leave the surface of the nucleus to form the coma and tail that give comets their intrinsic beauty. Studying the surface temperature and evolution of the coma and tail provides information on how the comet evolves as it approaches and leaves the vicinity of the sun. MIRO has the ability to study water, carbon monoxide, ammonia and methanol.
Alice, an ultraviolet spectrometer, analyzes gases in the comet's coma and tail; measures how fast the comet produces water, carbon monoxide and carbon dioxide (clues to the surface composition of the nucleus); and measures argon levels. These measurements help determine the temperature of the solar system when the nucleus formed more than 4.6 billion years ago.
The Ion and Electron Sensor is part of a suite of five instruments that analyzes the plasma environment of the comet, particularly the coma. The instrument measures the charged particles in the sun's outer atmosphere, or solar wind, as they interact with the gas flowing out from the comet.
NASA provided part of the electronics package for the Double Focusing Mass Spectrometer, which is part of the Swiss-built Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument. U.S. scientists also partnered on several non-U.S. instruments and were involved in seven of the mission's 26 instrument collaborations. NASA's Deep Space Network is supporting ESA's Ground Station Network for spacecraft tracking and navigation. NASA also provided autonomous science operations planning software, which helped in planning science operations and navigation support.
The Rosetta mission was launched in 2004 and arrived at comet 67P/Churyumov-Gerasimenko on Aug. 6, 2014. It's the first mission in history to rendezvous with a comet and escort it as it orbits the sun. On Nov. 4, 2014, a smaller lander named Philae -- which had been deployed from the Rosetta mothership -- touched down on the comet and bounced several times before alighting on the surface. Philae obtained the first images taken from a comet's surface and sent back valuable scientific data for several days.
"It will be hard to see that last transmission from Rosetta come to an end," said Art Chmielewski of JPL, project manager for the U.S. Rosetta. "But whatever melancholy we will be experiencing will be more than made up for in the elation that we will feel to have been part of this truly historic mission of exploration."
Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander was provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; French National Space Agency, Paris; and the Italian Space Agency, Rome. JPL, a division of Caltech in Pasadena, manages the U.S. contribution of the Rosetta mission for NASA's Science Mission Directorate in Washington. JPL also built the MIRO and hosts its principal investigator, Mark Hofstadter. The Southwest Research Institute (San Antonio and Boulder, Colorado), developed the Rosetta orbiter's IES and Alice instruments and hosts their principal investigators, James Burch (IES) and Alan Stern (Alice).
For more information on the US instruments aboard Rosetta, visit:
More information about Rosetta is available at:
News Media ContactDC Agle
Jet Propulsion Laboratory, Pasadena, Calif. | 0.845209 | 3.255933 |
The previous closest black hole is probably about three times further, about 3,200 light-years, he said.
The discovery of a closer black hole, which is in the constellation Telescopium in the Southern Hemisphere, hints that there are more out there. Astronomers theorise there are between 100 million to 1 billion of these small but dense objects in the Milky Way.
But scientists can usually only spot them when they’re absorbing sections of a partner star or another object falls into them.
Astronomers believe most black holes, including this newly discovered one, do not have anything close enough to swallow. So they go undetected.
Astronomers found this hole because of the unusual orbit of a star. The new black hole is part of what used to be a three-star dance in a system called HR6819. The two remaining super-hot stars are not close enough to be sucked in, but the inner star’s orbit is warped.
These are young hot stars compared to our 4.6 billion-year-old Sun.
They are maybe 140 million years old, but at 15,000°C, they are three times hotter than the Sun, Dr Rivinius said.
About 15 million years ago, one of those stars got too big and too hot and went supernova, turning into the black hole in a violent process, he said.
“It is most likely that there are black holes much closer than this one,” said Avi Loeb, director of Harvard’s Black Hole Initiative.
“If you find an ant while scanning a tiny fraction of your kitchen, you know there must be many more out there.”
Reader Q&A: Do black holes collapse?
Asked by: Patricia Rodrigues, King’s Lynn
The Schwarzschild radius (event horizon) of a black hole is sometimes thought of as the black hole’s ‘size’. It is proportional to mass, which means that more massive black holes have bigger Schwarzschild radii.
Left alone, black holes lose mass due to ‘Hawking radiation’, so that their event horizons are slowly shrinking. A typical black hole would take many billions of times the age of the Universe to completely ‘evaporate’ and disappear.
But, the interior of the black hole, or its ‘singularity’ (the point at which all the black hole’s matter is concentrated) has already reached the limit of its density and cannot ‘collapse’ any further.
Alexander is the Online Editor at BBC Science Focus and is the one that keeps sciencefocus.com looking shipshape and Bristol fashion. He has been toying around with news, technology and science on internet for well over a decade, and sports a very fetching beard. | 0.88001 | 3.792217 |
Features on the Moon's surface
The majority of features listed below are visible with a small telescope or binoculars. The moon is an ideal object for beginners to observe.
A great many craters litter the moons surface. Some of these craters can be up to hundreds of kilometres across. These craters are caused mainly by the impact of meteorites. Newly created craters have bright rays extending across the surface. These are caused when material is sprayed out from impacts onto the surface.
The surface appearance of the moon is largely craters and dark lunar Maria. The mares ('seas') were thought to be water from their dark and flat appearance. It was realized that these areas were lava flooding portions of the moon, leaving these dark areas. Massive impacts early in the life of the Moon created large basins in the surface that filled with lava flowing from the Moon's interior.
The brighter regions on the moon are the mountainous highlands, where the terrain is rough and strewn with rocky rubble. The lunar mountain ranges, with heights up to 25,000 ft (7800 m), are comparable to the highest mountains on earth but in general are not very steep. It is generally agreed that the highlands are the oldest parts of the moons surface.
Rilles are trenches within the Moon's surface and are thought to be caused by collapsing lava tubes. They are scattered all over the surface of the Moon and can be recognized quite easily. They resemble wide canyons and when near the terminator, give the impression of bottomless abysses. To observe the vast majority of Rilles a telescope of reasonable size is required although the largest ones can be observed with smaller telescopes.
|Weymouth Astronomy Estab 2006| | 0.84091 | 3.563747 |
When trying to get at the technical core of what the FBI is asking of Apple, this researcher/hacker/forensic scientist/? seems to have the explanations.
Might I suggest you start here and here and a Summary
Really you should just go read the last 15 or so posts.
This is a controversial topic, but at the core of the debate is a tremendous amount of misinformation and purposeful ambiguity. Fight the FUD (fear, uncertainty and doubt).
Source: Zdziarski’s Blog of Things
“We’ve taken a major step back in time, beyond what we’d ever expected to be able to do with Hubble. We managed to look back in time to measure the distance to a galaxy when the Universe was only three percent of its current age,” says Pascal Oesch of Yale University and lead author of the paper.To determine large distances, like the one to GN-z11, astronomers measure the redshift of the observed object. This phenomenon is a result of the expansion of the Universe; every distant object in the Universe appears to be receding from us and as a result its light is stretched to longer, redder wavelengths.Before astronomers determined the distance to GN-z11, the most distant measured galaxy, EGSY8p7, had a redshift of 8.68. Now, the team has confirmed GN-z11’s distance to be at a redshift of 11.1, which corresponds to 400 million years after the Big Bang.“The previous record-holder was seen in the middle of the epoch when starlight from primordial galaxies was beginning to heat and lift a fog of cold, hydrogen gas,” explains co-author Rychard Bouwens from the University of Leiden, the Netherlands. “This transitional period is known as the reionisation era. GN-z11 is observed 150 million years earlier, near the very beginning of this transition in the evolution of the Universe.”
This makes me think about the difference between a video camera and a still frame camera. A video camera, or video itself, is about capturing images over time, while a still camera, or a picture, is about capturing an image at this specific time. But what if the concept of a picture gets more complex, a photo taken today, right now, of a time in the past (realizing that this is always true of photography just on a incredibly tiny scale), then do we need to change the name of what is happening when the Hubble Space Telescope “documents” the past?
A new space telescope is so exciting but this is an ugly website
Source: Hubble breaks cosmic distance record | ESA/Hubble via Engadget
Described as a “voracious reader” by curator Geoffrey Marsh, Bowie’s top 100 book list spans decades, from Richard Wright’s raw 1945 memoir Black Boy to Susan Jacoby’s 2008 analysis of U.S. anti-intellectualism in The Age of American Unreason.
Source: David Bowie’s Top 100 Books : Open Culture
Fascinating (but short) article about early computer graphics.
Source: Nautilus via HackerNews
These are just silly. But boy oh boy do I enjoy them.
It seems all to fitting that track that starts to play at the end of Ken Block’s video would be M.I.A.’s Bad Girls. This feels like how music videos should be, epic, beautiful, ridiculous.
As you slide away from the curb, the sound of the electric drive motor hardly rises above a whisper. A few blocks from home, you steer the car into a special lane, and pull a lever under the dash. The front wheels lock in straight-ahead position. Simultaneously, the side-hatch door slides back and an electric third-rail shoe folds out. It makes contact with a power rail, the flanged wheels roll onto rails of a track, and your car accelerates at a controlled rate of 0.3g. You twirl a dial until you see ‘Fifth Street’ appear in a small window. Seconds later, as your car enters a main guideway at exactly 60 mph, you open the paper and begin scanning the news.
Fascinating long form article. This is near to my ideal vision for public transit.
The delightfully opposite of efficient public transit and another
Source: The road not taken : The Verge
In the remote and spectacular mountain ranges of Oman rise dozens of conical towers whose function and origin remain unknown. Only discovered by a British aviator in the nineties, these 5,000-year-old tombs are an enigmatic mystery for the archeologists of the 21st century.
Source: The Lost Tombs of Oman : Maptia via HackerNews
The orange and blue here reminds me strongly of lego sets I yearned for (and a few I did have) when I was young.
Note: MOC = “My own creation” This term refers to a non-Lego designed build. This is not my creation.
Lego Ice Planet “Elephant” : Brothers Brick
This is a photo of a scratch circle taken by David Marvin
However, the lack of snow and ice on the beaches has allowed unique features called scratch circles, or Scharrkreise, to form on the sand. Etched by windblown, dried dune grasses, the circles take shape when the wind causes a bent stalk of grass to pivot around on its axis, scratching out an arc or full circle in the sand.
Source: Scratch circle and Earth Science Picture of the Day
This makes me think of Andy Goldsworthy and some of his work. | 0.875434 | 3.187525 |
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Sinus Medii / / (Latin sinus mediī "Middle Bay") is a small lunar mare. It takes its name from its location at the intersection of the Moon's equator and prime meridian; as seen from the Earth, this feature is located in the central part of the Moon's near side, and it is the point closest to the Earth. From this spot the Earth would always appear directly overhead, although the planet's position would vary slightly due to libration.
|Diameter||287 km (178 mi)|
|Eponym||Bay of the Center|
During the Apollo program, Sinus Medii was designated ALS3. Flight operations planners were concerned about having the optimum lighting conditions at the landing site, hence alternative landing sites moved progressively westward, following the terminator. A delay of two days for weather or equipment reasons would have sent Apollo 11 to Sinus Medii instead of ALS2, Mare Tranquillitatis; another two-day delay would have resulted in ALS5, a site in Oceanus Procellarum, being targeted.
The eastern part of this area is notable for a series of rille systems. In the far northeast is the Rima Hyginus, which is bisected by the crater Hyginus. At the far eastern end is the 220-km long Rima Ariadaeus rille which continues eastward to the edge of the Mare Tranquillitatis. At longitudes 4-6° E is the Rimae Triesnecker rille system, named after the crater Triesnecker just to the west.
The northern edge of the Sinus Medii is formed by a highland region, with the impact craters Murchison and Pallas along the border. Near the northern border on this mare is the cup-shaped Chladni.
Another highland region lies to the south and southeastern edge of the Sinus Medii. Several flooded craters lie along this border, with Flammarion near the western edge, then Oppolzer, Réaumur, and Seeliger further east. The Rima Flammarion and Rima Oppolzer rilles lie along the edge of the mare near their corresponding craters. Also along the southeast border and bisecting the prime meridian is the crater Rhaeticus.
The English astronomer William Gilbert was the first to give a name to this mare, calling it Insula Medilunaria ("Middlemoon Island"). The idea for its present name originates with Michael Van Langren, who labelled it Sinus Medius in his 1645 map. Johannes Hevelius called the feature Mare Adriaticum ("The Adriatic Sea") in his 1647 map. Giovanni Riccioli called it Sinus Aestuum ("Bay of Hot Days") in his 1651 map.
- "Sinus Medii". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
- Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999), p.15
- Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999), p.41, 200.
- Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999), p.53, 201.
- Hevelius J. (1647). Selenographia sive Lunae descriptio. Gedani: Hünefeld. pp. 226–227, 234. doi:10.3931/e-rara-238. (List of names on p. 228)
- Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999), p.61, 216, 217.
- Map of the Moon by Giovanni Riccioli (1651)
|Wikimedia Commons has media related to Sinus Medii.| | 0.820659 | 3.455444 |
A new study challenges the long-held belief that the universe contains several hundred billion galaxies. Recently published in the Astrophysical Journal Letters, the theory reveals a universe with far fewer galaxies than previously thought. Using specially-developed computer simulations, a team of researchers has estimated the number of faint, distant galaxies as 10 to 100 times less than earlier claims.
Since its launch in 1990, the Hubble Space Telescope has allowed scientists and astronomers to uncover some of the most startling mysteries of outer space. Unlike the brighter galaxies present in the observable part of the universe, the faint galaxies exist in a distant region, which even the Hubble struggles to see. Formed over ten billion years ago, the faint galaxies were, until now, thought to be hundreds or thousands of times more in number than the bright galaxies. According to the new study, however, the number is merely ten to hundred times greater.
The study is part of a project, carried out jointly by the University of California, San Diego, Michigan State University and the Georgia Institute of Technology. For the research, the team relied on National Science Foundation’s advanced Blue Water supercomputer, to generate incredibly precise simulations of thousands of distant galaxies as well as their interactions through radiation and gravity. Using the results, the scientists were able to investigate, in great detail, the process of formation of star systems in early universe. Speaking about the project, Brian O’Shea, a professor of physics and astronomy at Michigan State University, said:
Our work suggests that there are far fewer faint galaxies than we once previously thought. Earlier estimates placed the number of faint galaxies in the early universe to be hundreds or thousands of times larger than the few bright galaxies that we can actually see with the Hubble Space Telescope. We now think that number could be closer to ten times larger.
According to O’Shea, the simulations correctly mapped the distant, observable galaxies that have already been discovered and listed. However, in the case of faint galaxies, the estimates were found to be inconsistent with former claims. Instead of an astronomically large number of faint star clusters, the simulations reported a far emptier picture of the universe. The team is currently awaiting the launch of the more advanced James Webb Space telescope, that will be operational from the year, 2018. A rightful successor to the Hubble, the JWST’s improved technology will allow the researchers to confirm their findings. O’Shea said:
A deeper understanding based on theory may be necessary to correctly interpret what’s being seen, such as high redshift survey results.
Michael Norman, the director of UCSD’s San Diego Supercomputer Center, believes that the Hubble Space Telescope can see only “the tip of the iceberg” that makes up the innumerable faint galaxies yet to be discovered.
Source: Astrophysical Journal Letters | 0.838876 | 3.920796 |
Докладчик: Rob R. Landis, NEO Program Executive (NASA Headquarters)
Название доклада: «International Asteroid Warning Network (IAWN)and NASA’s NEO observations Program»
Краткое содержание доклада:
The intent of the International Asteroid Warning Network (IAWN) is to establish a worldwide effort to detect, track, and physically characterize near-Earth objects (NEOs) to determine those that are potential impact threats to Earth. This network is comprised of a partnership of scientific institutions, observatories, and other interested parties performing observations, orbit computation, modeling, and other scientific research related to the impact potential and effects of asteroids. Initially, the concept was developed within the United Nations (UN) Committee on the Peaceful Uses of Outer Space (COPUOS). IAWN endeavors to foster a shared understanding of the NEO hazard and optimize the scientific return on these small celestial bodies. Part of IAWN is NASA’s NEO Observations Program. Since being established in 1998, NEO observations program has discovered ~98% of all new NEO discoveries. Since the program’s inception, NASA has funded several universities and space institutes to upgrade and operate existing 1-meter class telescopes to conduct the search for NEOs. Of critical importance to the effort is the Minor Planet Center (MPC) of the Smithsonian Astrophysical Observatory, where automated systems process [in near real-time] observations produced by the search teams. The NEO Program Office at the Jet Propulsion Laboratory (JPL) determines precise orbits for the objects. Both JPL and the MPC utilize processes and procedures for NEO orbit determination and prediction that are sanctioned and monitored by the International Astronomical Union (IAU) and produce data catalogues on small bodies in the Solar System that are utilized world-wide by the astronomical community. Most recently, the Wide-field Infrared Survey Explorer (WISE) was reactivated with an emphasis on detecting NEOs. WISE is in Sun-synchronous, near-polar inclination (97.5°) orbit around the Earth. The NEOWISE project continues to utilize WISE in ‘warm mode’ (i.e., at 3.4 and 4.6 microns) and in conjunction with ground-based follow-up, this unique dataset has set limits on population statistics, orbital parameters, approximate sizes, and initial compositional knowledge of the asteroid population. | 0.868162 | 3.436223 |
You can learn a lot from fake astrophotography.
The New Zealand Herald has an article today about a cool and very popular image of the Moon positioned perfectly within a radio satellite, produced by astrophotographer Chris Pegman: Supermoon image goes into media orbit
The article talks about how there has been debate online about whether or not this could be taken without resorting to Photoshop. It concludes that “the verdict was that it might be, but it would require an incredible amount of planning” but this isn’t strictly correct.
The apparent rotation of the Moon changes as it travels through the sky. When it rises, it will appear to be “on its side” relative to when it is at its zenith, and when it sets it will have rotated further still.
This is most obvious with a crescent Moon. Depending on if it’s waxing or waning, the Moon will rise with the crescent facing either down or up, then when it’s at its zenith the crescent will be facing sideways, and as it sets it will have rotated around further. Of course, the lit side of the Moon always faces the Sun. It’s the fact that the Earth rotates beneath us that makes it look like the Moon is rotating as it travels across the sky.
Here’s an example of this which I took with my phone in July, showing a waning crescent Moon shortly before sunset:
We can see from the lunar maria (the dark areas) that the Moon in Chris Pegman’s picture is rotated how it would be if (when viewed from the southern hemisphere) it were near its peak, not near the horizon, so his picture couldn’t be produced without artificial manipulation.
Mark Gee is a fantastic astrophotographer from Wellington. In October he captured a time lapse of a full moon rising, in which you can clearly see that angle of the Moon is not the same as in Chris Pegman’s image when it rises: Supermoon rises over New Zealand timelapse.
There’s a Twitter account called Fake Astropix, which tweets fake astronomical images with the reasons why they are recognised as fake (well, as much as can be given within a tweet).
I find these reasons can be very educational and thought provoking. For example, it’s impossible to take a photo from Earth where the Sun and Moon don’t appear to be roughly the same apparent size. Also, the full moon can’t appear next to the Sun in the sky (remember the lit side faces the Sun). So “debunking” these fake astronomical images can be a good educational exercise that makes you think a bit more carefully about how things work in our solar system.
Do you have any fake astronomical images that you can share, along with the reason why you can tell it must have been faked?
Have you seen any astronomical images that you think might be fake but you’re not sure? Share them here and let’s investigate, and see if we can learn something.
Featured image by Chris Pegman | 0.814437 | 3.251289 |
Crescent ♊ Gemini
Moon phase on 29 July 2016 Friday is Waning Crescent, 24 days old Moon is in Gemini.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 2 days on 26 July 2016 at 23:00.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing about ∠10° of ♊ Gemini tropical zodiac sector.
Lunar disc appears visually 3.4% wider than solar disc. Moon and Sun apparent angular diameters are ∠1956" and ∠1890".
Next Full Moon is the Sturgeon Moon of August 2016 after 19 days on 18 August 2016 at 09:27.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 24 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 204 of Meeus index or 1157 from Brown series.
Length of current 204 lunation is 29 days, 9 hours and 44 minutes. It is 2 hours and 35 minutes shorter than next lunation 205 length.
Length of current synodic month is 3 hours and 1 minute shorter than the mean length of synodic month, but it is still 3 hours and 9 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠48.9°. At beginning of next synodic month true anomaly will be ∠77.9°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
2 days after point of perigee on 27 July 2016 at 11:25 in ♉ Taurus. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 11 days, until it get to the point of next apogee on 10 August 2016 at 00:05 in ♏ Scorpio.
Moon is 366 395 km (227 667 mi) away from Earth on this date. Moon moves farther next 11 days until apogee, when Earth-Moon distance will reach 404 266 km (251 199 mi).
6 days after its descending node on 23 July 2016 at 07:49 in ♓ Pisces, the Moon is following the southern part of its orbit for the next 6 days, until it will cross the ecliptic from South to North in ascending node on 5 August 2016 at 07:48 in ♍ Virgo.
20 days after beginning of current draconic month in ♍ Virgo, the Moon is moving from the second to the final part of it.
11 days after previous South standstill on 18 July 2016 at 03:41 in ♑ Capricorn, when Moon has reached southern declination of ∠-18.569°. Next day the lunar orbit moves northward to face North declination of ∠18.529° in the next northern standstill on 31 July 2016 at 04:53 in ♋ Cancer.
After 4 days on 2 August 2016 at 20:45 in ♌ Leo, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.180746 |
The subject of particle physics concerns itself with the basic constituents of matter at the most fundamental nature - the subatomic particles from which all matter in the known universe is made.
In the first part of the twentieth century it was believed that all matter was made from atoms composed of just three basic particles - positively charged protons and electrically neutral neutrons forming a central nucleus, with negatively charged electrons circulating in orbits around the nucleus.
However, studies on these seemingly "fundamental" particles in the mid part of the twentieth century soon revealed that the protons and neutrons are in themselves composed of even smaller particles - the so called "quarks" (which are also present in more exotic kinds of particles found in the cosmic radiation originating from outside our own galaxy) and exchange particles called "gluons" which hold them together.
Protons and neutrons are made from different combinations of just two types (or "flavours" of quark (called "up" and "down" quarks) but four other flavours of quark (called "strange", "charm", "bottom" and "top") have also been identified in particles found in cosmic rays and accelerator experiments (see below), making six in all. Together with six types of lepton (the electron, the electron-neutrino, the muon, the muon-neutrino, the tau, and the tau-neutrino), the gluons and the intermediate vector bosons (special force carrying entities which allow the quarks and leptons to interact) these particles are currently believed to be the fundamental "building blocks" from which all matter in the universe is made.
The subject of particle physics deals with the detection and measurement of the properties and behavior of these fundamental particles, along with the four apparantly distinct forces by which they are known to interact. These four forces are categorised as the electromagnetic, strong nuclear and weak nuclear forces, as well as gravity. The weak nuclear and electromagnetic forces have already been shown to be two different aspects of a single underlying "electroweak" force, and it is believed that this will be combined with the strong nuclear force in a "Grand Unified Theory" (or GUT) at some point in the future - followed by the addition of gravity within a mooted "Theory of Everything" (or ToE). The eventual demonstration that all four forces are different manifestations of one single underlying force is thus the ultimate aim and "Holy Grail" of particle physics.
[N.B. It is a very strange world indeed, as subatomic particles do not behave according to the "intuitive" and deterministic laws of classical physics (which account for phenomenon as seen at the macroscopic level in our everyday lives), but rather they obey the laws of quantum mechanics (a theory which was developed to account for the very different way that very small objects such as fundamental particles are believed to behave).]
To study these basic particles and forces huge particle accelerators (machines capable of accelerating subatomic particles and colliding them at very high energies) are required. Because of the scale of these particle accelerators (which are often tens of kilometres long) they are often built in underground tunnels at international laboratories such as CERN near Geneva in Switzerland, Fermilab near Chicago in the USA, DESY in Hamburg in Germany, SLAC in California, and JINR in Russia and KEK in Japan, as well as others throughout the world. [N.B. Please click here for more information about particle physics laboratories worldwide.]
Typical experiments in the subject often involve hundreds or even thousands of physicists, usually working within multinational research teams at the above laboratories. In addition, engineers and technicians from various different fields (including engineering, electronics, computing etc) are also needed to support the experimentalists, who often work round the clock on shifts while their experiments collect valuable data. Processing the vast amount of information which is collected is a mammoth task which often pushes computing technology to its limits, and particle physics has often been seen as a driving force towards the development of better and faster computers and computing technology.
Besides using accelerators, particle physics can also be studied by observing cosmic radiation, which includes high energy particles and gamma rays which rain down on our planet from outer space. Such experiments are often conducted at high altitudes or very deep underground at installations such as the Gran Sasso laboratory in Italy and the Boulby Mine at Boulby on the Yorkshire Coast in the UK.
Although often thought to be quite esoteric, the pursuit of knowledge in the field of high energy physics has led to many practical "spin off" developments in areas as diverse as cyrogenics, medicine, electronic sensing, computer technology and telecommunications. Probably one of the most significant of these developments in recent years has been that of the World Wide Web - the now globally accepted format for presenting information across the Internet which was invented at CERN and which you will probably be using to read this page(!)
[N.B. Please click here for more details about the history of the Internet and the World Wide Web.]
Please click here for books about particle physics.
Please click here for books about the history of the Internet and the World Wide Web.
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Please also read the "Particle Physics" copyright and disclaimer details | 0.817362 | 4.008297 |
The Moon and Saturn will share the same right ascension, with the Moon passing 3°04' to the north of Saturn. The Moon will be 16 days old.
From Ashburn, the pair will be visible in the morning sky, becoming accessible around 21:38, when they rise to an altitude of 7° above your south-eastern horizon. They will then reach its highest point in the sky at 01:36, 28° above your southern horizon. They will be lost to dawn twilight around 05:25, 8° above your south-western horizon.
The Moon will be at mag -12.5, and Saturn at mag 0.0, both in the constellation Ophiuchus.
The pair will be too widely separated to fit within the field of view of a telescope, but will be visible to the naked eye or through a pair of binoculars.
A graph of the angular separation between the Moon and Saturn around the time of closest approach is available here.
The positions of the two objects at the moment of conjunction will be as follows:
|Object||Right Ascension||Declination||Constellation||Magnitude||Angular Size|
The coordinates above are given in J2000.0. The pair will be at an angular separation of 173° from the Sun, which is in Taurus at this time of year.
|The sky on 09 June 2017|
15 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|10 Dec 2016||– Saturn at solar conjunction|
|15 Jun 2017||– Saturn at opposition|
|21 Dec 2017||– Saturn at solar conjunction|
|17 Apr 2018||– Saturn at aphelion| | 0.895513 | 3.400453 |
- Open Access
Studies on neutrino Earth radiography
Earth, Planets and Space volume 62, pages211–214(2010)
Neutrino Earth radiography seems to provide an alternative tool to study the very deep geological structures. Even if the level of precision of such measurements might not be very high, nevertheless the information which can be obtained are absolutely independent and complementary to the more conventional seismic studies.
The Earth’s tomography with ultra-high energy cosmic neutrinos seems to provide a viable independent determination of the Earth’s internal structure (Jain et al., 1999; Reynoso and Sampayo, 2004). Standard methods to measure the density of the Earth are based on seismic wave propagation that have substantial intrinsic uncertainties (Jain et al., 1999).
In this framework, atmospheric neutrinos in the energy range of the order of few TeV provide a unique opportunity to probe the very interior of our planet due to their interaction length which does not exceed too much the Earth radius. In particular, at this energy, neutrinos are copious enough to cross the Earth and interact during their travel transforming in their corresponding charged lepton via Charged-Current Interaction. The detectable events can be classified in two categories: the track events where the charged lepton is produced outside the fiducial volume and is able to emerge from the surface and be detected by the NT, and the contained events, where neutrino converts inside the NT. For seek of brevity we will focus our analysis on track events only.
At the moment the experimental community is undertaking a relevant effort to construct giant Neutrino Telescopes (NT’s). After the first generation of telescopes which has proved the feasibility of the Cerenkov detection technique under deep water (Balkanov et al., 1999) and ice (Ahrens et al., 2002) by detecting atmospheric neutrinos, we are likely approaching the first detections at the IceCube (Ahrens et al., 2004) telescope, being completed at the South Pole, and possibly at the smaller ANTARES (Spurio, 2006) telescope under construction in the Mediterranean. Moreover, ANTARES as well as NESTOR (Aggouras et al., 2006) and NEMO (Migneco et al., 2008) are involved in R&D projects aimed at the construction of a km3 NT in the deep water of the Mediterranean sea, coordinated in the European network KM3NeT (Katz, 2006). In this very exciting scientific framework it has been proposed the idea to use neutrinos, which are elusive particles, to probe the very internal part of the Earth.
In this framework, the evidence for a sensitivity of the physics at a NT to the very deep geological structure is provided by the muons event rate expected at a NT as a function of the arrival direction. It shows a clear angular dependence that is affected by the radial matter density profile adopted, as it is reported in Fig. 1, taken from González-García et al. (2008). In this analysis it is shown the expected zenith angle distribution of atmospheric v μ induced events in IceCube for different energy thresholds assuming Preliminary Reference Earth Model (PREM) (Dziewonski, 1971). In the following we will refer our calculation to a km3 NT placed at NEMO site, reported in Fig. 2.
2. Neutrino Sensitivity to Matter Distribution
Neutrino Sensitivity to Matter Distribution In order to understand how the number of charged lepton events at a km3 NT depends on the density of matter crossed by HE neutrinos, let us remind the formalism developed in Cuoco et al. (2007).
We define the km3 NT fiducial volume as that bounded by the six lateral surfaces Σ a (the subindex a = D, U, S, N, W, and E labels each surface through its orientation: Down, Up, South, North, West, and East), and indicate with Ω a ≡ (θ a , φ a ) the generic direction of a track entering the surface Σ a . The scheme of the NT fiducial volume and two examples of incoming tracks are shown in Fig. 3. We introduce all relevant quantities with reference to v μ being the case vτ completely analogous.
Let dΦ v /(dE v dΩ a ) be the differential flux of UHE v μ +v̄ μ . The number per unit time of μ leptons emerging from the Earth surface and entering the NT through Σ a with energy E μ is given by
The kernel kμ a (E v , E μ ; r⃗ a , Ω a ) is the probability that an incoming v μ crossing the Earth, with energy E v and direction Ω a , produces a μ-lepton which enters the NT fiducial volume through the lateral surface dS a at the position r⃗ a with energy E μ (see Fig. 3 for the angle definition). For an isotropic flux we can rewrite Eq. (1), summing over all the surfaces, as
which defines the total aperture Aμ(E v ). The contribution of each surface to the total aperture reads
As already shown in details in Cuoco et al. (2007) a typical event corresponds to the simultaneous fulfillment of the following conditions:
A v μ with energy E v travels over a distance z through the Earth before interacting. The corresponding probability P1 is given by(4)
where N A the Avogadro number and ϱr is the Earth density assumed to be constant).
The neutrino produces a μ in the interval z, z + dz, the probability of such an event being(6)
The produced μ emerges from the Earth rock with an energy E′ μ . This happens with a probability(7)
See Cuoco et al. (2007) for notations.
Finally, the μ lepton emerging from the Earth rock propagates in water and enters the NT fiducial volume through the lateral surface Σ a at the pointr⃗ a with energy E μ . The corresponding survival probability is(8)
where ϱ w stands for the water density and z w (r⃗ a ,Ω a ) represents the total length in water before arriving to the fiducial volume for a given track entering the lateral surface Σ a at the point r⃗ a and with direction Ω a .
3. Results and Conclusions
As shown the Earth density profile enters via the matter density, ϱr in most of the previous expressions, and thus one must expect a certain sensitivity to PREM characteristics of number of events.
In particular we have performed part of the integration contained in Eq. (2) by generating a large number of tracks crossing the NEMO site by means of a detailed DEM of the under-water Earth surface which is available from the Global Relief Data survey (ETOPO2). A grid of altimetry measurements with a vertical resolution of 1 m averaged over cells of 2 minutes of latitude and longitude. In terms of these tracks and applying the above formalism we have reproduced the analogous plot of Fig. 1 in the case on the Mediterranean under sea NT at NEMO site. In fact, in Fig. 4 we report the ratio of the angular distributions of the expected v μ -induced track events for PREM divided the same quantity obtained for a Homogeneous Earth model. This ratio is evaluated by using two values of the muon energy threshold. A larger threshold amplifies the effect due to the non trivial radial density profile which makes the ratio significantly different from the unit. Unfortunately, increasing the energy threshold also means to reduce the expected number of events and thus the statistics which implies larger error bars.
Nevertheless, as already stated in González-García et al. (2008) the quoted uncertainties, relative to ten years of data taking, seem to suggest the possibility to recognize a non trivial radial density profile with a good level of statistical confidence.
Aggouras, G. et al. [NESTOR Collaboration], Recent results from NESTOR, Nucl. Instrum. Meth. A, 567, 452, 2006.
Ahrens, J. et al. [AMANDA Collaboration], Observation of high-energy atmospheric neutrinos with the Antarctic Muon and Neutrino Detector Array, Phys. Rev. D, 66, 012005, 2002.
Ahrens, J. et al. [IceCube Collaboration], Sensitivity of the IceCube detector to astrophysical sources of high energy muon neutrinos, Astropart. Phys., 20, 507, 2004.
Balkanov, V. A. et al., Registration of atmospheric neutrinos with the BAIKAL neutrino telescope NT-96, Astropart. Phys., 12, 75, 1999.
Cuoco, A., G. Mangano, G. Miele, S. Pastor, O. Pisanti, and P. D. Serpico, Ultrahigh energy neutrinos in the Mediterranean: Detecting v(tau) and v(mu) with a km3 telescope, JCAP, 0702, 007, 2007.
Dziewonski, A., Earth Structure, Global, in The Encyclopedia of Solid Earth Geophysics, edited by James, D. E., 331, Van Nostrand Reinhold, New York, 1971.
González-García, M. C., F. Halzen, M. Maltoni, and H. K. M. Tanaka, Radiography of earth’s core and mantle with atmospheric neutrinos, Phys. Rev. Lett., 100, 061802, 2008.
Jain, P., J. P. Ralston, and G. M. Frichter, Neutrino absorption tomography of the Earth’s interior using isotropic ultra-high energy flux, Astropart. Phys., 12, 193, 1999.
Katz, U. F., KM3NeT: Towards a km**3 Mediterranean neutrino telescope, Nucl. Instrum. Meth. A, 567, 457, 2006.
Migneco, E. et al. [NEMO Collaboration], Recent achievements of the NEMO project, Nucl. Instrum. Meth. A, 588, 111, 2008.
Reynoso, M. M. and O. A. Sampayo, On neutrino absorption tomography of the earth, Astropart. Phys., 21, 315, 2004.
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ETOPO2, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Geophysical Data Center, 2-minute Gridded Global Relief Data, http://www.ngdc.noaa.gov/mgg/fliers/01mgg04.html, 2001
About this article
Cite this article
Borriello, E., De Lellis, G., Mangano, G. et al. Studies on neutrino Earth radiography. Earth Planet Sp 62, 211–214 (2010). https://doi.org/10.5047/eps.2009.06.004
- High energy cosmic rays
- Earth radial density profile | 0.819244 | 3.567083 |
We now know quite a bit about the interior of the atom, the fundamental building block of nature. There are just a few basic "parts" of an atom, and while it would be difficult for the average person to actually "see" and identify these parts on some specific atom, for example, a carbon atom in a piece of bread, it isn't difficult to understand the basic idea. There really are just four structures of any atom: the nucleus, the protons and neutrons of the nucleus, and the surrounding electron cloud.
Remember: Electrons do not orbit the nucleus like the earth orbits the sun. Electrons are found in a cloud in a defined area near the nucleus. They do move rapidly around the nucleus (visualize a cloud of mosquitoes buzzing around your nose on a summer evening).
Find the nucleus. The nucleus of an atom is always right smack dab in the middle of any atom, like the sun is in the middle of the solar system (but don't take that analogy too far). The nucleus is very dense and compact, and while it can have just one particle (a single proton for regular hydrogen), it usually has multiple protons and neutrons. No matter what element you are looking at, the protons and neutrons will always be densely packed together in the nucleus. On your diagram, find and label the nucleus.
Find and label protons. The protons are always in the nucleus, always have a positive charge (label them with a "P" or a "+"), and there are always the same number of protons as the atomic number of the element. Example: What is the atomic number of gold? It is 79. So a gold atom will have 79 protons.
Find and label neutrons. Neutrons have no charge, so a good way to represent one in the nucleus is with just an "N". In a nucleus diagram, the neutrons will be jammed tightly right in with the protons. If you were trying to find and label the neutrons in the gas called tritium, an isotope of hydrogen, you would find two neutrons packed in with one proton.
Find and label the electron cloud. As an aid to remembering that atoms with overall neutral charges have an equal number of protons and electrons, draw small circles in the electron cloud area representing the number of electrons of that element. For example, with carbon, which has six protons, you know that it will also have six electrons. So in the area around the carbon nucleus, draw six randomly spaced small circles (each with a negative sign "-" inscribed).
- atom image by Oleg Verbitsky from Fotolia.com | 0.825618 | 3.60902 |
Astronomers find star material could be building block of life
An organic molecule detected in the material from which a star forms could shed light on how life emerged on Earth, according to new research led by Queen Mary University of London.
The researchers report the first ever detection of glycolonitrile (HOCH2CN), a pre-biotic molecule which existed before the emergence of life, in a solar-type protostar known as IRAS16293-2422 B.
This warm and dense region contains young stars at the earliest stage of their evolution surrounded by a cocoon of dust and gas—similar conditions to those when our Solar System formed.
Detecting pre-biotic molecules in solar-type protostars enhances our understanding of how the solar system formed as it indicates that planets created around the star could begin their existence with a supply of the chemical ingredients needed to make some form of life.
This finding, published in the journal Monthly Notices of the Royal Astronomical Society: Letters, is a significant step forward for pre-biotic astrochemistry since glycolonitrile is recognised as a key precursor towards the formation of adenine, one of the nucleobases that form both DNA and RNA in living organisms.
IRAS16293-2422 B is a well-studied protostar in the constellation of Ophiuchus, in a region of star formation known as rho Ophiuchi, about 450 light-years from Earth.
The research was also carried out with the Centro de Astrobiología in Spain, INAF-Osservatorio Astrofisico di Arcetri in Italy, the European Southern Observatory, and the Harvard-Smithsonian Center for Astrophysics in the USA.
Lead author Shaoshan Zeng, from Queen Mary University of London, said: "We have shown that this important pre-biotic molecule can be formed in the material from which stars and planets emerge, taking us a step closer to identifying the processes that may have led to the origin of life on Earth."
The researchers used data from the Atacama Large Millimeter/submillimetre Array (ALMA) telescope in Chile to uncover evidence for the presence of glycolonitrile in the material from which the star is forming—known as the interstellar medium.
With the ALMA data, they were able to identify the chemical signatures of glycolonitrile and determine the conditions in which the molecule was found. They also followed this up by using chemical modelling to reproduce the observed data which allowed them to investigate the chemical processes that could help to understand the origin of this molecule.
This follows the earlier detection of methyl isocyanate in the same object by researchers from Queen Mary. Methyl isocyanate is what is known as an isomer of glycolonitrile—it is made up of the same atoms but in a slightly different arrangement, meaning it has different chemical properties. | 0.865426 | 3.891543 |
A supernova is the death blast of a giant star, far larger than our Sun. Massive stars go out with a bang, outshining entire galaxies, allowing us to see them across the universe. A supernova observed in 2013 occurred in a distant galaxy and took over 30 Million years to reach Earth, where the timing was perfect for us to observe and study it. And now that it’s been studied, the explosion was truly the death of a giant.
The supernova, named 2013 ej, was discovered in June 2013 in the galaxy M74 in the constellation Pisces. It was the closest supernova observed in the last few years, giving astronomers a chance to study it in greater detail than a typical distant supernova. After it was discovered, observations continued for 450 days to help astronomers understand the short term evolution of the explosion and ejecta.
Southern Methodist University in Dallas, USA led the study, and gave some context for just how incredible the explosion was. The massive star was 15 times as heavy as our Sun and 200x as wide. When it exploded, the blast ejected material at a speed of 10,000 kilometers per second (36 million Km/h) into space.
Understanding the mechanisms of how supernovae explode are among the most intense areas of research in astrophysics today. They are incredibly valuable as a method for determining distances to objects in the universe, acting as a standard candle that is bright enough to observe over incredible distances. | 0.818167 | 3.646033 |
This new NASA/ESA Hubble Space Telescope image shows Messier 96 (M96 or NGC 3368), a spiral galaxy just over 35 million light-years away in the constellation of Leo (The Lion). It is of about the same mass and size as the Milky Way. It was first discovered by astronomer Pierre Méchain in 1781, and added to Charles Messier’s famous catalogue of astronomical objects just four days later.
The galaxy resembles a giant maelstrom of glowing gas, rippled with dark dust that swirls inwards towards the nucleus. Messier 96 is a very asymmetric galaxy; its dust and gas is unevenly spread throughout its weak spiral arms, and its core is not exactly at the galactic centre. Its arms are also asymmetrical, thought to have been influenced by the gravitational pull of other galaxies within the same group as Messier 96.
This group, named the M96 Group, also includes the bright galaxies Messier 105 and Messier 95, as well as a number of smaller and fainter galaxies. It is the nearest group containing both bright spirals and a bright elliptical galaxy (Messier 105). | 0.841831 | 3.085856 |
More than fifty years, he worked for NASA, but now has William Borucki, the American space agency leave. From this weekend, he may enjoy his retirement. And not surprising, because the scientist let a cargo of valuable knowledge behind.
Likely, the name Borucki’s not everybody’s bells ring. However, it is likely that his work, however, at the most will know. Borucki was during his career at the American space agency, one of the driving forces behind the Kepler project. Thanks to that project took NASA over the past few years, less than a thousand exoplanets. That are planets that revolve around other stars than our sun.
After completing his master’s in Physics came Borucki in 1962 at NASA. It is there that he years engaged in the development of the heat shields for the Apollo program, that was intended to be the first man on the moon. The shields were designed to ensure that the astronauts safely back could go home without having to go into the atmosphere.
After the work on the Apollo heat shields began Borucki on study meteorology. Herein he obtained his master’s degree eventually in 1982. In the same year he began to bite into the formation of thunderstorms. He is examined by means of the data from the satellites, how the storm on our planet and on other planets, including Jupiter, Venus, and Saturnusmaan Titan. To do this, he developed several models.
Slowly went the attention of the scientist to other planets. He started at NASA to deal with the so-called Transit Method. That means that scientists observe stars to see if there are planets beyond mad. Borucki was specialized in the method and later came up with a way that telescopes in a similar way, looking could to so-called exoplanets.
The researcher wanted to have telescopes in space went in search of the planets, but the first two proposals above were made by the NASA disapproved. The first time, in 1992, the technique is still not suitable. Two years later it turned out that the project is too much money it would cost.
Fortunately for Borucki and his team was there in 1995 the first exoplanet around a similar star like the our found. This proved the effect of the former detection method. Therefore followed in 1996, again a research proposal, but was again rejected. The technique would still not be able to thousands of stars simultaneously to observe and measure.
Here let Borucki not down. Together with other researchers, he built an observatory on Mount Hamilton, east of the Californian San Jose. With a special telescope, the Vulcan, he showed that it was actually possible to make thousands of stars simultaneously to observe. Eventually, it was his plan to exoplanets to study in 2000 accepted.
The work resulted in the Kepler satellite, which only was launched in 2009 by financial setbacks. Thanks to the spacecraft are so far over a thousand exo-planets have been found around other stars. At the beginning of this year, scientists found thanks to Kepler, a 11.2 billion years old planetary system with five planets. It is the oldest planetary system of the milky way galaxy that we know of.
Borucki from Saturday after 53 years in the service of NASA of his pension. Many praising him for his leadership, his vision and his research. An astronaut says: “He goes away with such a high valuation that not only his legacy will be celebrated, but also his work will be remembered as the beginning of a new chapter in the history of science and the human imagination.” | 0.894525 | 3.131436 |
Paul conducts public and private amateur astronomy programs and star parties for children and adults in schools, camps, parks and other settings. Below are some of his slide (Power Point) programs which are geared to general audiences of all ages with limited astronomical background. (Some will also be of interest to the more sophisticated amateur astronomers.)
"A Brief History of the Copernican Revolution"
This program presents the major players and their roles in the "paradigm shift" from the Ptolemaic Earth-centered view of the cosmos to Copernican's Sun-centered view. "Constellations with a Little Imagination"
This program introduces star patterns we call constellations, how and why they came to be, and some of the better known patterns. "Constellations of the Season"
This program focuses on the constellations prominent in the current season. "Cosmic Concert"
In 2001 concert pianist Dr. Michael Ard and amateur astronomer Dr. Paul Derrick combined their talents to present a concert in which Dr. Ard's piano performance of William Duckworth's "The Time Curve Preludes" was given a cosmic perspective by Dr. Derrick's accompanying astronomy slide presentation. In Dr. Ard's absence (he has now retired to Tucson), Dr. Derrick's revisited presentation, set to Don Robertson's synthesized recorded "Starmusic: Horizons Beyond Infinity," produces a visual-auditory-cerebral experience that takes one from the beginning to the end of time-space, and from the remote reaches of deep space to everyday life -- all in 15 minutes. "Extraterrestrials"
Based on the marvelous book Extraterrestrials: A Field Guide for Earthlings written by Terence Dickinson and illustrated by Adolf Schaller, this program presents speculations on what extraterrestrial life - if it exists - might be like. "Journey to Outer Space"
Using the metaphor of an imaginary journey starting at planet Earth and traveling into deep outer space, this program presents a good introductory survey of "what's out there" - from solar system objects to stars, nebulae, clusters, galaxies, and yes, even black holes. "Learning the Night Sky by Regions"
This program is an introduction to Paul's original system of learning the major stars and constellations by partitioning the night sky into nine regions and the story or theme which relates each of the region's constellations to one another. "Life Cycle of a Star"
This program examines the life cycle of stars beginning with their formation in star-birthing nebulae through their main sequence and on to their end stages and death, including planetary nebulae, white dwarfs, supernovae, pulsars, and black holes. "Maya Astronomy"
This program presents an elementary introduction to the role of astronomy in the creation myths of the Mayas who lived hundreds of years ago in what is now southern Mexico and Guatemala. "Meteors, Comets and Impacts"
This program introduces meteors, comets and the relationships between them, and the effects produced by their impacts with other objects, including Earth. "Our Expanding Universe"
The Big Bang, the Copernican Revolution, other intelligent life in the universe, and the impact these things have on us and our species are among the topics are presented and opened for discussion. "Seeing the Southern Sky"
Based on the Stargazer's 2001 and 2012 trips to New Zealand (and Tahiti), this program presents highlights of the night sky as seen from the southern hemisphere and the differences those of us from the northern hemisphere are accustomed to seeing - not just seeing new stars and constellations but also seeing familiar patterns from a different perspective - like an "up-side-down" Orion. "Solar System Model"
Using familiar every-day objects (e.g., Earth as a tennis ball) and the Waco area, this program helps one visualize the relative sizes of solar system objects and the distances between them. "Time: Cycles of Nature and Humans"
This program identifies the major measures of the passage of time we use in our everyday life, differentiates those which are human inventions, and examines more closely those based on cycles of nature. | 0.854237 | 3.073263 |
Nobody is sure exactly how many planets there are in the universe, but it's undoubtedly a number that's got an awful lot of zeroes. After all, by NASA's estimate our Milky Way galaxy alone contains about 100 billion planets, including at least 1,500 that are within 50 light years of Earth.
In fact, they're so common that scientists now think that stars with planets orbiting them are more the rule than the exception. Some of those worlds are rocky planets like ours, while others are enormous gas giants that have more in common with Jupiter, Saturn and Neptune. But while we know that planets are plentiful, we still have plenty to learn about the process by which planets form from dust that swirls around their suns.
That's why astronomers have turned their gaze to young stars hundreds of light-years from Earth, in an effort to watch new worlds that are just starting to take shape. One such effort is the recently completed VLA Nascent Disk and Multiplicity (VANDAM) Survey.
That project used the Very Large Array, a collection of 27 radio telescopes in a Y-shaped configuration in the plains of New Mexico, to study 100 young stars in the Perseus Cloud, a star-forming region that's about 750 light-years in the constellation Perseus. (That means that what they are observing actually happened during the late Middle Ages here on Earth, since that's how long it has taken the radio waves generated by those objects to reach us.)
The thing to understand about both stars and their solar systems is that they all start out as a big cloud of gas and dust. As this Universe Today article explains, eventually something happens — a supernova explodes nearby, for instance, or a passing star exerts its gravity — to change the pressure inside the cloud, causing it to collapse into a disk. The pressure at the center becomes so great that hydrogen atoms begin to fuse and produce helium, starting up the nuclear furnace inside the young star. Meanwhile, whatever material doesn't become part of the star starts to form other dusty discs, which become planets.
As the California Academy of Sciences details, up until VANDAM, astronomers had only observed a few of those dusty discs around young stars, because they're not that easy to detect. VANDAM was able to make out the disks around a quarter of the stars in the survey.
At the meeting of the American Astronomical Society in early January, a team led by University of Illinois researcher Dominique Segura-Cox used data from the VANDAM survey to shed new light on the nature of dusty disks and the process by which they form and eventually become planets.
The researchers found that the dusty disks around some protostars, as young stars are called, are even bigger than theoretical models have predicted. Those models are based on the idea that as the material around a young star is drawn inward toward it, the star also pulls in magnetic fields, which become concentrated as they get closer. That effect, which is called magnetic breaking, supposedly limited the size of the dusty disks to a radius of roughly 10 times the 93-million-mile expanse between the Earth and the Sun.
But Segura-Cox and her colleagues found that the dusty disks around some of the young stars are as much as three times larger than the magnetic breaking model predicted, and perhaps even bigger. The researchers think this might be caused by some sort of misalignment between the rotation axis and the magnetic field of the young star. A study published in 2014, which also used VANDAM data, found that the material being pulled toward one young star is twisting the magnetic field lines and changing their configuration along the way.
But the most significant thing discovered may be that the dusty disks seem to form very early in the life of a young star, and that all of the ingredients needed to make a planet are available then. As John Tobin, an astronomer from the Netherlands' Leiden Observatory who also represented research on dusty disks at the same conference, explained in a press release: "It is probable that there are already centimeter-sized particles in these young disks, meaning that the growth of solids progresses rapidly." | 0.869676 | 3.995733 |
Do you like Earth’s solid surface and life-inclined climate? Thank your lucky (massive) star
ANN ARBOR—Earth’s solid surface and moderate climate may be due, in part, to a massive star in the birth environment of the Sun, according to new computer simulations of planet formation.
Without the star’s radioactive elements injected into the early solar system, our home planet could be a hostile ocean world covered in global ice sheets.
“The results of our simulations suggest that there are two qualitatively different types of planetary systems,” said Tim Lichtenberg of the National Centre of Competence in Research PlanetS in Switzerland. “There are those similar to our solar system, whose planets have little water, and those in which primarily ocean worlds are created because no massive star was around when their host system formed.”
Lichtenberg and colleagues, including University of Michigan astronomer Michael Meyer, were initially intrigued by the role the potential presence of a massive star played on the formation of a planet.
Meyer said the simulations help solve some questions, while raising others.
“It is great to know that radioactive elements can help make a wet system drier and to have an explanation as to why planets within the same system would share similar properties,” Meyer said.
“But radioactive heating may not be enough. How can we explain our Earth, which is very dry, indeed, compared to planets formed in our models? Perhaps having Jupiter where it is was also important in keeping most icy bodies out of the inner solar system.”
Researchers say while water covers more than two-thirds of the surface of Earth, in astronomical terms, the inner terrestrial planets of our solar system are very dry—fortunately, because too much of a good thing can do more harm than good.
All planets have a core, mantle (inside layer) and crust. If the water content of a rocky planet is significantly greater than on Earth, the mantle is covered by a deep, global ocean and an impenetrable layer of ice on the ocean floor. This prevents geochemical processes, such as the carbon cycle on Earth, that stabilize the climate and create surface conditions conducive to life as we know it.
It is great to know that radioactive elements can help make a wet system drier and to have an explanation as to why planets within the same system would share similar properties.
The researchers developed computer models to simulate the formation of planets from their building blocks, the so-called planetesimals—rocky-icy bodies of probably dozens of kilometers in size. During the birth of a planetary system, the planetesimals form in a disk of dust and gas around the young star and grow into planetary embryos.
Radioactive heat engine
As these planetesimals are heated from the inside, part of the initial water ice content evaporates and escapes to space before it can be delivered to the planet itself.
This internal heating may have happened shortly after the birth of our solar system 4.6 billion years ago, as primeval traces in meteorites suggest, and may still be ongoing in numerous places.
Right when the proto-Sun formed, a supernova occurred in the cosmic neighborhood. Radioactive elements, including aluminium-26, were fused in this dying massive star and got injected into our young solar system, either from its excessive stellar winds or via the supernova ejecta after the explosion.
The researchers say the quantitative predictions from this work will help near-future space telescopes, dedicated to the hunt for extrasolar planets, to track potential traces and differences in planetary compositions, and refine the predicted implications of the Al-26 dehydration mechanism.
They are eagerly awaiting the launch of upcoming space missions with which Earth-sized exoplanets outside our solar system will be observable. These will bring humanity ever-closer to understanding whether our home planet is one of a kind, or if there are “an infinity of worlds of the same kind as our own.”
Their study appears in Nature Astronomy. Other researchers include those from the Swiss Federal Institute of Technology, University of Bayreuth and University of Bern.
Adapted from the original story published by PlanetS. | 0.870006 | 3.756217 |
If there ever was a planet that I feel has gotten a bad rap for its inability to be readily observed, it would have to be Mercury, known in many circles as the "elusive planet."
In the classic astronomy guide "New Handbook of the Heavens" (1941 McGraw-Hill Book Company, Inc.), here is what is written about the innermost planet:
"Because you must look for it so soon after sunset, or before sunrise, Mercury stays close to the sun like a child clinging to its mother's apron strings. There was a famous astronomer, Copernicus, who never saw the planet all his life."
Nonetheless, over the next three weeks, we will be presented with an excellent opportunity to view Mercury in the early morning/dawn sky. The planet is considered "inferior" because its orbit is nearer to the sun than the Earth's is: Therefore, Mercury always appears, from our vantage point, to be in the same general direction as the sun.
In old Roman legends, Mercury was the swift-footed messenger of the gods. The planet is well named, for it is the closest planet to the sun and the swiftest planet in the solar system, averaging about 30 miles per second (48 kilometers per second). Mercury makes its yearly journey around the sun in only 88 Earth days. Interestingly, the time it takes Mercury to rotate once on its axis is 59 days, so all parts of its surface experience periods of intense heat and extreme cold. Although the planet's mean distance from the sun is only 36 million miles (58 million km), Mercury has by far the broadest range of temperatures: 800 degrees Fahrenheit (427 degrees Celsius) on its day side; minus 280 degrees F (–173 degrees C) on its night side.
In the pre-Christian era, Mercury actually had two names; it was not known that it could alternately appear on one side of the sun and then the other. The planet was called Mercury when in the evening sky, but was known as Apollo when it appeared in the morning. There are reports that, around the 5th century B.C., Pythagoras pointed out that the two orbs were one and the same.
Sunrise ... sunset
Mercury possesses the most eccentric orbit of any planet. At its farthest distance from the sun (aphelion), the planet lies about 43 million miles (69 million km) away, but when it arrives at its closest point to the sun (perihelion) it's just less than 29 million miles (47 million km) away. So, its angular velocity through space is appreciably higher at perihelion. Interestingly, Mercury rotates on its axis three times for every two revolutions it makes around the sun. But when it arrives at perihelion (as it will on Aug. 20) Mercury's orbital velocity will exceed its rotational speed.
As a consequence, a hypothetical observer standing on Mercury would see a sight unique in our entire solar system: Over the course of eight days (four days before perihelion through four days after perihelion), the sun will appear to reverse its course, then double back and resume its normal track across the sky. If our observer were located on the part of Mercury where the sun rises around the time of perihelion, the sun would appear to partially come up above the eastern horizon, pause and then drop back below the horizon, followed in rapid succession by a second sunrise!
Mercury in the morning
Mercury rises before the sun all of this month, and is surprisingly easy to see from now through Aug. 27. All you have to do is just look low above the east-northeast horizon during morning twilight, from about 30 to 45 minutes before sunrise for a bright yellowish-orange "star."
Mercury will be at its western elongation, 18 degrees to the west of the sun, on Aug. 9, rising shortly after dawn breaks and making this a very good morning apparition. Mercury, like Venus, appears to go through phases, like the moon does. When August began, Mercury was a crescent, just 13% illuminated by the sun. By next Tuesday (Aug. 6) that amount of illumination will have more than doubled to 28%, and the amount of its surface illuminated by the sun will continue to increase for the rest of this month: Almost 50% by Aug. 12 and more than 75% by Aug. 19. So, although the planet will begin to turn back toward the sun's vicinity after Aug. 9, Mercury will continue to brighten steadily, which should help to keep it in easy view over the next few weeks.
The 'Twins' point the way
As an added bonus, during the first half of August, Mercury will not be very far from the famous "Twin Stars" of the Gemini constellation, Pollux and Castor. These two stars will rise above the east-northeast horizon around 4 a.m. local daylight time, about half an hour before Mercury does The pair can be used as pointers to help you to locate Mercury.
During the first week of August, look for the Gemini twins at around 5 a.m. hovering about 15 degrees above the east-northeast horizon. Your clenched fist held at arm's length measures roughly 10 degrees, so Pollux and Castor will appear a bit higher than that above the horizon. Now look well down to the lower right of these stars and you'll see a somewhat brighter star-like object, hovering only about 5 degrees above the horizon.
That will be Mercury.
On Aug. 12, trace an imaginary line from Castor, through Pollux, continue straight toward the horizon for 10 degrees and you will come to Mercury, shining at a brilliant -0.3 magnitude. In the days that follow, the distance between Mercury and the Twin Stars will increase, while Mercury moves to their lower left.
The speedy planet will still be easily visible as late as Aug. 27; though nearer to the sun, it will have brightened to –1.5, even rivaling Sirius, the brightest star in the night sky. Thereafter, it drops back down under the dawn horizon.
- The Brightest Visible Planets in August's Night Sky: How to See them (and When)
- Catch a Shooting Star with 2019's Summer Meteor Showers
- The Mercury Transit of 2016 in Amazing Photos
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications, and he is also an on-camera meteorologist for Verizon FiOS1 News in New York's lower Hudson Valley. Follow us on Twitter @Spacedotcom and on Facebook. | 0.915662 | 3.564122 |
Come Thursday (March 19), we will have a change of the seasons: the occurrence of the vernal equinox, marking the official start of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. In fact, it will be a rather auspicious occurrence: the earliest that the equinox has occurred nationwide in 124 years. More on that in a moment.
The exact moment of the equinox will occur Thursday night at 11:49 p.m. EDT (0349 GMT on March 20), according to the astronomy reference book "Astronomical Table of the Sun, Moon and Planets" (Willmann-Bell, 2016). At that time, the Earth will reach the point in its orbit where its axis isn't tilted toward or away from the sun. Thus, the sun will then be directly over a specific point on the Earth's equator moving northward. On the sky, it's where the ecliptic and celestial equator cross each other.
A not-so-equal equinox
On the day of the equinox, the sun will appear to rise exactly east and set exactly west. Daytime and nighttime are often said to be equally long with the equinox, but this is a common misconception — the day can be up to 8 minutes longer, depending on your latitude.
The sun is above the horizon half the day and below for half — but that statement neglects the effect of the Earth's atmosphere, which bends the rays of sunlight (called refraction) around the Earth's curvature when the sun lies close to the horizon. But, because of this bending of the sun's rays, the disk of the sun is always seen slightly higher above the horizon than it really is.
In fact, when you see the sun appearing to sit on the horizon, what you are looking at is an optical illusion; the sun at that moment is actually below the horizon. So, we get several extra minutes of daylight at the start of the day and several extra minutes more at the end.
The supposed equality of day and night gives us the Latin name "equinox," which means "equal night." But in reality, thanks to our atmosphere, the day is longer than the night at the equinox. At the latitude of New York, for instance, day and night are roughly equal a few days before the equinox, on St. Patrick's Day (March 17).
Sun overhead from the Emerald of the Equator
Astronomers can calculate the moment of the vernal equinox right down to the nearest second. This year it will occur on Thursday (March 19) at 11:49:28 p.m. EDT (0349 GMT on March 20). At that moment, the sun will appear directly overhead about 50 miles (80 kilometers) south of Gorontalo, a province of Indonesia — often referred to as the "Emerald of the Equator" — on the island of Sulawesi, on the equator in the Gulf of Tomini. In the days that follow, the direct rays of the sun migrate to the north of the equator and the length of daylight in the Northern Hemisphere will correspondingly appear to increase.
Why so early?
As was noted, this will be the earliest that the vernal equinox will occur across the contiguous United States in 124 years. There are two specific reasons for this variation of the date: leap years and daylight saving time.
When a leap year set us back a day
First, that 2020 is a leap year (meaning that the month of February had one extra day) is not the reason for the early arrival of this year's equinox. Rather, it is the leap year that we observed in the year 2000.
Let's look at the dates and times of the vernal equinoxes leading up to 2000. Note that each year the occurrence of the equinox happens about 6 hours (or one-quarter of a day) later in the calendar:
- 1996: March 20 at 3:03 a.m. EST (0803 GMT)
- 1997: March 20 at 8:54 a.m. EST (1354 GMT)
- 1998: March 20 at 2:54 p.m. EST (1954 GMT)
- 1999: March 20 at 8:46 p.m. EST (0146 GMT on March 21)
- 2000: March 20 at 2:35 a.m. EST* (0735 GMT)
In 46 B.C., Julius Caesar's consulting astronomer, Sosigenes, knew from Egyptian experience that the solar year was about 365.25 days in length. So to account for that residual quarter of a day, an extra day — leap day — was added to the calendar every four years. Unfortunately, the new Julian calendar was 11 minutes and 14 seconds longer than the actual solar year. By the year 1582 — thanks to the overcompensation of observing too many leap years — the calendar had fallen out of step with the solar year by 10 days.
It was then that Pope Gregory XIII stepped in and, with the advice of his own astronomer, Christopher Clavius (1538-1612), produced our current "Gregorian" calendar. First, to catch things up, 10 days were omitted after Oct. 4, 1582, making the next day Oct. 15. In order to better adjust the new calendar format to more closely match the length of the solar year, most century years (such as 1700, 1800, 1900) — which in the old Julian calendar would have been observed as leap years — were not. The exceptions were those century years equally divisible by 400. That's why 1700, 1800 and 1900 were not leap years.
But 2000 was a century year, evenly divisible by 400, so it was observed as a leap year. Had we skipped the leap year in 2000 (as in 1900), then the vernal equinox in 2000 would have occurred a day later, on March 21 at 2:35 a.m. EST (0735 GMT).
Hence, the reason we have an asterisk next to that date.
So, thanks to February having an extra day in 2000, the date of the equinox slipped back a day to March 20.
Daylight saving time delayed the equinox in the East
Because the solar year is not exactly one-quarter of a day longer than the 365-day calendar year, but a little bit less than one-quarter (24.22%) of a day, the occurrence of the equinox comes about 47 minutes earlier (on average) every four years:
- 2000: March 20 at 2:35 a.m. EST (0735 GMT)
- 2004: March 20 at 1:48 a.m. EST (0648 GMT)
- 2008: March 20 at 1:48 a.m. EDT (0548 GMT)*
- 2012: March 20 at 1:14 a.m. EDT (0514 GMT)
- 2016: March 20 at 12:30 a.m. EDT (0430 GMT)
- 2020: March 19 at 11:49 p.m. EDT (0349 GMT on March 20)
The asterisk (*) indicates that the United States and Canada had begun observing daylight saving time on the second Sunday in March rather than the first Sunday in April, a practice that began in 2007. In 2000, only those in the Pacific time zone (as well as in Alaska and Hawaii) observed the equinox on March 19. In 2004, 2008 and 2012, those time zones again saw spring arrive on March 19, along with people on Mountain Time.
In 2016, those in the Central time zone celebrated a March 19 arrival. Were we still on the old system (when daylight saving time did not begin until early April), we would have been on standard time in 2016, and those in the eastern parts of North America, too, would have observed the equinox on March 19 (at 11:30 p.m. EST), but daylight time pushed that off for another four years. Finally this year, from coast-to-coast, spring will arrive on March 19 — the earliest in 124 years.
And as a point of record: In 1896, the vernal equinox arrived on March 19 at 9:29 p.m. EST (0229 GMT on March 20).
Astronomical vs. meteorological spring
Truth be told, there are really two springs: astronomical spring and meteorological spring.
Astronomical spring is measured by the vernal equinox, but that's only a marker in the big flow of time, set up by astronomers — a sidereal milepost, accurate as a ticking clock but only approximately timing the changing of the seasons.
Meteorological spring supposedly has already started as of March 1, and runs through the end of May, according to Accuweather. In truth, however, meteorological spring ignores the clock and calendar, makes its own rules and creates a festival of song and blossom, all in its own time.
The crocuses, early robins and other vernal phenomena pay no attention to the hairsplitting details marking the astronomical arrival of the vernal equinox. They all have their own way of knowing when spring truly begins.
- Season to season: Earth's equinoxes & solstices (infographic)
- Vernal equinox: First day of spring seen from space (photo)
- Why the autumnal equinox doesn't fall on the same day every year
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications. Follow us on Twitter @Spacedotcom and on Facebook.
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 | 0.861493 | 3.774753 |
According to the researchers, including Michelle Kunimoto from the University of British Columbia in Canada, the Kepler satellite, over its original four-year mission, looked for planets, especially those lying in the potentially habitable "Goldilocks Zone" of their stars, where liquid water could exist on a rocky planet''s surface.
The current findings, published in The Astronomical Journal, include one such rare planet named KIC-7340288 b.
This planet, the researchers said, is just one and a half times the size of the Earth -- small enough to be considered rocky, instead of gaseous like the giant planets of the Solar System, and in the habitable zone of its star.
"This planet is about a thousand light years away, so we''re not getting there anytime soon!" said Kunimoto.
"But this is a really exciting find, since there have only been 15 small, confirmed planets in the habitable zone found in Kepler data so far," she added.
The study noted that the planet has a year that is 142 and a half days long, orbiting its star at 0.444 Astronomical Units (AU, the distance between Earth and the Sun) -- just bigger than Mercury''s orbit in our Solar System.
The planet gets about a third of the light that the Earth gets from the Sun, the scientists noted.
Of the other 16 new planets discovered, the researchers said, the smallest is only two-thirds the size of the Earth -- one of the smallest planets to be found with Kepler so far.
The remaining planets, they said, range in size up to eight times the size of the Earth.
In the current study Kunimoto used what is known as the "transit method" to look for the planets among the roughly 2,00,000 stars observed by the Kepler mission.
"Every time a planet passes in front of a star, it blocks a portion of that star''s light and causes a temporary decrease in the star''s brightness," she explained.
"By finding these dips, known as transits, you can start to piece together information about the planet, such as its size and how long it takes to orbit," Kunimoto added.
In addition to the new planets, the researchers were also able to observe thousands of known Kepler planets using the transit method, which they said will be used to reanalyse the exoplanet census as a whole.
"We''ll be estimating how many planets are expected for stars with different temperatures," said Jaymie Matthews, another co-author of the study. PTI VIS VIS VIS
Disclaimer :- This story has not been edited by Outlook staff and is auto-generated from news agency feeds. Source: PTI | 0.863086 | 3.879146 |
By Zoe Bedard
The Hubble Space Telescope is a space telescope that was created to gather light from far away objects and to take photos of these objects so that people could understand more about space. It was named after Edwin Hubble, an American astronomer. The launch of the Hubble Telescope was delayed because of the Space Challenger, a previous space shuttle that carried 7 members, and had failed in its mission to orbit the earth. The spacecraft telescope broke into pieces 73 seconds after its launch. The Hubble Space Telescope was launched into orbit on April 24, 1990. It was carrying 5 astronauts, and was launched from the Kennedy Space Center.
The project had began in 1940, it took decades of planning and research to complete. In 1949 the first paper about the telescope was written by Lyman Spitzer, an astrophysicist at Yale University. This was at a time where satellites had not been frequently launched yet, and many scientists lacked crucial knowledge about these mysteries. Lyman Spitzer wanted to explain the importance of learning about astronomy from space itself. In July 1958, Congress passed The Space Act, which created the National Aeronautics Space Administration more commonly recognized as NASA. This was created for the Space Race against the Soviet Union and to help scientists, astronomers, and engineers pursue their hopes on building the telescope. In 1974 astrophysicists held their first meeting for the space telescope. It contained the collosal budget and technology requirements for the spacecraft. On October 1, 1977, Congress approved funding for the project and it officially began.
With their first goal being to build it, they began building the mirror in 1978, and in 1989 astronauts began training for their trip. It was named in 1983, and then 3 years later the Space Shuttle Challenger was lost, being completely destroyed after take off and placing fear into the creators of the Hubble Space Telescope. Finally on April 24, 1990, it was finally launched successfully inside the Space Shuttle Discovery, from the Kennedy Space Center in Florida.
It was deployed on April 25, 1990, and since then has made some of the most amazing and useful discoveries of our time. The telescope is able to contribute to finding how far we are from objects in space, and it can photograph Supernovas (when a star explodes) and planets. The spacecraft can tell us what surfaces on comets and planets look like and what their made of. We have even discovered that the universe is still expanding and creating more space and emptiness! The creation of the telescope has done so much for the growth of our knowledge on astrology and engineering.
Sadly, NASA is planning to replace the Hubble Telescope with the new James Webb Telescope, but the legacy of the Hubble will never be forgotten. | 0.806782 | 3.302119 |
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