Time Space Science

The eerie beauty of the northern and southern lights has evoked visions of the supernatural for centuries: foxes of fire whisking their tales, the fighting souls of dead warriors or ancestors dancing around a ceremonial fire.

The English poet Sir Walter Scott in 1805 conjured up otherworldly beings when he wrote, "He knew, by the streamers that shot so bright, That spirits were riding the northern light."

But it was a French scientist, not a poet, who named the sight after Roman gods. In 1621, Pierre Cassendi paired Aurora, goddess of dawn, with Boreas, god of the north wind, to christen the northern lights “aurora borealis.” Those centered above the South Pole are called aurora australis for “southern dawn.”

Even today, scientists and forecasters at NOAA’s Space Weather Prediction Center in Boulder, Colo., look beyond the Earth itself for the first step in a chain of events that ultimately paints brilliant hues across the night sky at opposite ends of the planet.

Anatomy of an Aurora

Deep within the Sun, 93 million miles away, roiling plasma rises and bursts through the solar atmosphere, sometimes thrusting highly charged protons and electrons our way. When this so-called solar wind arrives near Earth, it energizes protons and electrons trapped in the planet’s magnetic field.

These charged particles then travel down magnetic field lines, like beads slipping along a string, into Earth’s upper atmosphere near the poles. There the particles in turn excite atoms and molecules of oxygen, nitrogen, and other atmospheric gases. As these atoms relax back down into their normal state, they release the excess energy as visible light, forming an aurora oval loosely centered on the magnetic pole.

During an aurora, vivid arcs, curls, waves and bands of green, red, and sometimes blue dance across the sky for minutes or hours, peaking near midnight — all between 60 and 600 miles above the ground.

Many people think auroras are rare events, but there’s almost always an aurora of some size in the sky near the poles. Seeing one is another matter.

Auroras are most often visible in regions bordering the Arctic Circle: Canada, Alaska, northern Greenland, the Scandinavian coast, and Siberia. In the south, you need to be visiting Antarctica to see an aurora frequently. But the larger the solar storm reaching Earth’s upper atmosphere, the farther the aurora extends from the poles. Residents of New England or southern Chile might see an aurora every few years. If you live in Florida or Italy, you’d be lucky to see an aurora once in your lifetime.

How Space Weather Affects Us

One of the nation’s critical operations centers, NOAA’s Space Weather Prediction Center keeps a close eye on solar activity that precedes an aurora. When a major storm explodes on the sun, followed by a suddenly intensified solar wind heading toward Earth, the center alerts airlines, the military, the communications industry, power companies and the media that a storm is on its way.

Why do NOAA scientists care about this odd “weather” on the sun and in space? NOAA monitors solar storms because they can disrupt satellite functions, power grid operations, GPS signals, high-frequency communications used by airlines and the military, and other space-based technologies that we depend on. Solar radiation could also threaten astronauts’ safety if they happen to be outside the space shuttle as it zooms past.

Visit the Space Weather Prediction Center’s aurora Web site to view the current shape and size of the auroras around the two poles. If the auroras shown there are exceptionally large and you’re in a far northern or far southern latitude, look for those spirits hurtling across the midnight sky!

Tips on Seeing an Aurora

Best time of night: 10:00 p.m. to 2:00 a.m.
Best conditions: clear night with no moon and far from light pollution
Best season: mid-winter
Best phase of the solar cycle: maximum
Best years in the sun’s current cycle: 2012 to 2013
Best position on Earth: far northern or southern latitudes


http://www.noaa.gov/

The "coming of age" of galaxies and black holes has been pinpointed, thanks to new data from NASA's Chandra X-ray Observatory and other telescopes. This discovery helps resolve the true nature of gigantic blobs of gas observed around very young galaxies.

About a decade ago, astronomers discovered immense reservoirs of hydrogen gas -- which they named "blobs" – while conducting surveys of young distant galaxies. The blobs are glowing brightly in optical light, but the source of immense energy required to power this glow and the nature of these objects were unclear.

A long observation from Chandra has identified the source of this energy for the first time. The X-ray data show that a significant source of power within these colossal structures is from growing supermassive black holes partially obscured by dense layers of dust and gas. The fireworks of star formation in galaxies are also seen to play an important role, thanks to Spitzer Space Telescope and ground-based observations.

"For ten years the secrets of the blobs had been buried from view, but now we've uncovered their power source," said James Geach of Durham University in the United Kingdom, who led the study. "Now we can settle some important arguments about what role they played in the original construction of galaxies and black holes."

Galaxies are believed to form when gas flows inwards under the pull of gravity and cools by emitting radiation. This process should stop when the gas is heated by radiation and outflows from galaxies and their black holes. Blobs could be a sign of this first stage, or of the second.

Based on the new data and theoretical arguments, Geach and his colleagues show that heating of gas by growing supermassive black holes and bursts of star formation, rather than cooling of gas, most likely powers the blobs. The implication is that blobs represent a stage when the galaxies and black holes are just starting to switch off their rapid growth because of these heating processes. This is a crucial stage of the evolution of galaxies and black holes - known as "feedback" - and one that astronomers have long been trying to understand.

"We're seeing signs that the galaxies and black holes inside these blobs are coming of age and are now pushing back on the infalling gas to prevent further growth," said coauthor Bret Lehmer, also of Durham. "Massive galaxies must go through a stage like this or they would form too many stars and so end up ridiculously large by the present day."

Chandra and a collection of other telescopes including Spitzer have observed 29 blobs in one large field in the sky dubbed "SSA22." These blobs, which are several hundred thousand light years across, are seen when the Universe is only about two billion years old, or roughly 15% of its current age.

In five of these blobs, the Chandra data revealed the telltale signature of growing supermassive black holes - a point-like source with luminous X-ray emission. These giant black holes are thought to reside at the centers of most galaxies today, including our own. Another three of the blobs in this field show possible evidence for such black holes. Based on further observations, including Spitzer data, the research team was able to determine that several of these galaxies are also dominated by remarkable levels of star formation.

The radiation and powerful outflows from these black holes and bursts of star formation are, according to calculations, powerful enough to light up the hydrogen gas in the blobs they inhabit. In the cases where the signatures of these black holes were not detected, the blobs are generally fainter. The authors show that black holes bright enough to power these blobs would be too dim to be detected given the length of the Chandra observations.

Besides explaining the power source of the blobs, these results help explain their future. Under the heating scenario, the gas in the blobs will not cool down to form stars but will add to the hot gas found between galaxies. SSA22 itself could evolve into a massive galaxy cluster.

"In the beginning the blobs would have fed their galaxies, but what we see now are more like leftovers," said Geach. "This means we'll have to look even further back in time to catch galaxies and black holes in the act of forming from blobs."

These results will appear in the July 10 issue of the Astrophysical Journal. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.


http://chandra.harvard.edu/

Astronomers who think they know how the very early universe came to have so much interstellar dust need to think again, according to new results from the Spitzer Space Telescope.


In the last few years, observers have discovered huge quantities of interstellar dust near the most distant quasars in the very young universe, only 700 million years after the cosmos was born in the Big Bang.

"And that becomes a big question," said Oliver Krause of the University of Arizona Steward Observatory in Tucson and the Max Planck Institute for Astronomy in Heidelberg. "How could all of this dust have formed so quickly?"

Astronomers know two processes that form the dust, Krause said. One, old sun-like stars near death generate dust. Two, infrared space missions have revealed the dust is produced in supernovae explosions.

"The first process takes several billion years," Krause noted. "Supernovae explosions, by contrast, produce dust in much less time, only about 10 million years."

So when astronomers reported detecting submillimeter emission from massive amounts of cold interstellar dust in the supernova remnant Cassiopeia A last year, some considered the mystery solved. Type II supernovae like 'Cas A' likely produced the interstellar dust in the very early universe, they concluded. (Type II supernovae come from massive stars that blow apart in huge explosions after their cores collapse.)

Krause and colleagues from UA's Steward Observatory and the Max Planck institute in Heidelberg have now discovered that the detected submillimeter emission comes not from the Cas A remnant itself but from the molecular cloud complex known to exist along the line of sight between Earth and Cas A. They report the work in the Dec. 2 issue of Nature.

Cas A is the youngest known supernova remnant in our Milky Way. It is about 11,000 light years away, behind the Perseus spiral arm clouds that are roughly 9,800 light years away. Krause suspects that the Perseus clouds explain why late 17th century astronomers didn't report observing the brilliant Cas A outburst around A.D. 1680. Cas A is so close to Earth that the supernova should have been the brightest stellar object in the sky, but dust in the Perseus clouds eclipsed the view.

The Arizona and German team mapped Cas A at 160-micron wavelengths using the ultra-heat-sensitive Multiband Imaging Photometer (MIPS) aboard the Spitzer Space Telescope. These long wavelengths are the most sensitive to cold interstellar dust emission. They then compared the results with maps of interstellar gas previously made with radio telescopes. They found that the dust in these interstellar clouds account for virtually all the emission at 160 microns from the direction of Cas A.

Minus the emission from this dust, there is no evidence for large amounts of cold dust in Cas A, the team concludes.

"Astronomers will have to go on searching for the source of the dust in the early universe," UA Steward Observatory astronomer and Regents' Professor George Rieke said. Rieke is principal investigator for the Spitzer Space Telescope's MIPS instrument and a co-author of the Nature paper.

"Solving this riddle will show astronomers where and how the first stars formed, or perhaps indicate there is some non-stellar process that can produce large amounts of dust," Rieke said. "Either way, (finding the source of the dust) will reveal what went on at the formative stage for stars and galaxies, an epoch that is nearly unobserved in any other way."

Authors of the Nature article, "No cold dust within the supernova remnant Cassiopeia A," are Oliver Krause, Stephan M. Birkmann, George H. Rieke, Dietrich Lemke, Ulrich Klaas, Dean C. Hines and Karl D. Gordon.

Birkmann, Lemke and Klaas are with the Max Planck Institute for Astronomy in Heidelberg. Krause, Rieke, and Gordon are with the University of Arizona Steward Observatory. Hines is with the Space Science Institute in Boulder, Colo.

The Spitzer Space Telescope is managed for NASA by the Jet Propulsion Laboratory in Pasadena, Calif.

On the evidence to date, our solar system could be fundamentally different from the majority of planetary systems around stars because it formed in a different way. If that is the case, Earth-like planets will be very rare. After examining the properties of the 100 or so known extrasolar planetary systems and assessing two ways in which planets could form, Dr Martin Beer and Professor Andrew King of the University of Leicester, Dr Mario Livio of the Space Telescope Science Institute and Dr Jim Pringle of the University of Cambridge flag up the distinct possibility that our solar system is special in a paper to be published in the Monthly Notices of the Royal Astronomical Society.


In our solar system, the orbits of all the major planets are quite close to being circular (apart from Pluto’s, which is a special case), and the four giant planets are a considerable distance from the Sun. The extrasolar planets detected so far - all giants similar in nature to Jupiter – are by comparison much closer to their parent stars, and their orbits are almost all highly elliptical and so very elongated.

‘There are two main explanations for these observations,’ says Martin Beer. ‘The most intriguing is that planets can be formed by more than one mechanism and the assumption astronomers have made until now - that all planets formed in basically the same way - is a mistake.’

In the picture of planet formation developed to explain the solar system, giant planets like Jupiter form around rocky cores (like the Earth), which use their gravity to pull in large quantities of gas from their surroundings in the cool outer reaches of a vast disc of material. The rocky cores closer to the parent star cannot acquire gas because it is too hot there and so remain Earth-like.

The most popular alternative theory is that giant planets can form directly through gravitational collapse. In this scenario, rocky cores - potential Earth-like planets - do not form at all. If this theory applies to all the extrasolar planet systems detected so far, then none of them can be expected to contain an Earth-like planet that is habitable by life of the kind we are familiar with.

However, the team are cautious about jumping to a definite conclusion too soon and warn about the second possible explanation for the apparent disparity between the solar system and the known extrasolar systems. Techniques currently in use are not yet capable of detecting a solar-system look-alike around a distant star, so a selection effect might be distorting the statistics - like a fisherman deciding that all fish are larger than 5 inches because that is the size of the holes in his net.

It will be another 5 years or so before astronomers have the observing power to resolve the question of which explanation is correct. Meanwhile, the current data leave open the possibility that the solar system is indeed different from other planetary systems.

Notes

1. Currently around 100 extrasolar planets are known which have been detected through the wobble of their host stars caused by the motion of the planets themselves.

2. The paper has recently been accepted by the Monthly Notices of the Royal Astronomical Society but no publication date has yet been set.


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http://www.ras.org.uk/

An extrasolar planet under three suns has been discovered in the constellation Cygnus by a planetary scientist at the California Institute of Technology using the 10-meter Keck I telescope in Hawaii. The planet is slightly larger than Jupiter and, given that it has to contend with the gravitational pull of three bodies, promises to seriously challenge our current understanding of how planets are formed.

In the July 14 issue of Nature, Maciej Konacki, a senior postdoctoral scholar in planetary science at Caltech, reports on the discovery of the Jupiter-class planet orbiting the main star of the close-triple-star system known as HD 188753. The three stars are about 149 light-years from Earth and are about as close to one another as the distance between the sun and Saturn.

In other words, a viewer there would see three bright suns in the sky. In fact, the sun that the planet orbits would be a very large object in the sky indeed, given that the planet's "year" is only three and a half days long. And it would be yellow, because the main star of HD 188753 is very similar to our own sun. The larger of the other two suns would be orange, and the smaller red.

Konacki refers to the new type of planet as "Tatooine planets," because of the similarity to Luke Skywalker's view of his home planet's sky in the first Star Wars movie.

"The environment in which this planet exists is quite spectacular," says Konacki. "With three suns, the sky view must be out of this world-literally and figuratively."

However, Konacki adds that the fact that a planet can even exist in a multiple-star system is amazing in itself. Binary and multiple stars are quite common in the solar neigborhood, and in fact outnumber single stars by some 20 percent.

Researchers have found most of the extrasolar planets discovered so far by using a precision velocity technique that is easier to employ on studies of single stars. Experts generally avoided close-binary and close-multiple stars because the existing planet detection techniques fail for such complicated systems, and also because theories of solar-system formation suggested that planets were very unlikely to form in such environments.

Konacki's breakthrough was made possible by his development of a novel method that allows him to precisely measure velocities of all members of close-binary and close-multiple-star systems. He used the technique for a search for extrasolar planets in such systems with the Keck I telescope. The planet in the HD 188753 system is the first one from this survey.

"If we believe that the same basic processes lead to the formation of planets around single stars and components of multiple stellar systems, then such processes should be equally feasible, regardless of the presence of stellar companions," Konacki says. "Planets from complicated stellar systems will put our theories of planet formation to a strict test."

Scientists in 1995 discovered the first "hot Jupiter"-in other words, an extrasolar gas-giant planet with an orbital period of three to nine days. Today, more than 20 such planets are known to orbit other stars. These planets are believed to form in a disk of gas and condensed matter at or beyond three astronomical units (three times the 93-million-mile distance between the sun and Earth).

A sufficient amount of solid material exists at three astronomical units to produce a core capable of capturing enough gas to form a giant planet. After formation, these planets are believed to migrate inward to their present very close orbits.

If the parent star is orbited by a close stellar companion, then its gravitational pull can significantly truncate a protoplanetary disk around the main star. In the case of HD 188753, the two stellar companions would truncate the disk around the main star to a radius of only 1.3 astronomical units, leaving no space for a planet to form.

"How that planet formed in such a complicated setting is very puzzling. I believe there is yet much to be learned about how giant planets are formed," says Konacki.

The research was funded by NASA

http://www.caltech.edu/

The UK's leading team of planet-hunting astronomers, the Wide Angle Search for Planets (WASP), have announced the discovery of three new planets.

These extra-solar planets were seen to pass in front of, or transit, their host star. Studying such planets outside of our Solar System allows scientists to investigate how planetary systems form. WASP is the first team to detect planets in both the Northern and Southern Hemisphere using this technique.

Exoplanet expert Dr. Pierre Maxted comments “The planets are known as ‘hot-Jupiters’ as they are similar to Jupiter but are so close to their parent star that they orbit it in less than two days. This means that these planets have a surface temperature of nearly 2000°C and so are unlikely to host life. But finding these planets is important as these stars could also host much smaller planets similar to Earth, although detecting these worlds will be much more difficult”.

The planets orbit around stars similar to our Sun that are located at a distance of 850 light-years away from the Earth. Two are in the constellation of Phoenix visible only from the Southern hemisphere, while the third is in the Northern constellation of Lyra. All three stars are too faint to be seen with the naked eye, but are easily detectable with a small telescope.

Dr Coel Hellier, of Keele University, comments "When we see a transit we can deduce the size and mass of the planet and also what it is made of, so we can use these planets to study how solar systems form."

WASP-4 and WASP-5 are the first planets discovered by the WASP project's cameras in South Africa, and were confirmed by a collaboration with Swiss and French astronomers. "These two are now the brightest transiting planets in the Southern hemisphere" said Dr Hellier. WASP-3 is the third planet that the team has found in the North, using the SuperWASP camera sited in the Canary Islands.

Using data produced by SuperWASP’s cameras, which monitor up to 400,000 stars every minute, the new extra-solar planets were discovered as they were seen to pass in front of their host star.

Explaining the discovery, Dr Don Pollacco of Queen’s University, Belfast, Astrophysics Research Centre said: “We take pictures of the sky and measure the brightness of stars. If a planet is going around one of these stars and it happens to pass across the face of that star, our cameras will pick up the light from the star getting a little fainter.

“Discoveries such as these open up a whole new area of astronomy. Such transiting planets are important because they are the only ones that can have their mass and size measured directly. Astronomers can determine what they are made of and armed with this information we can begin to understand how these solar systems were formed.”

The WASP project is the most ambitious project in the world designed to discover large planets. Funding for the project comes from the UK Universities and the Science and Technology Facilities Council.

http://www.keele.ac.uk/

Saturn's ring shadows appear wrapped in a harmonious symphony with the planet in this color view from the Cassini spacecraft.

Saturn and its rings would nearly fill the space between Earth and the Moon. Yet, despite their great breadth, the rings are a few meters thick and, in some places, very translucent. This image shows a view through the C ring, which is closest to Saturn, and through the Cassini division, the 4,800-kilometer-wide gap (2,980-miles) that arcs across the top of the image and separates the optically thick B ring from the A ring. The part of the atmosphere seen through the gap appears darker and more bluish due to scattering at blue wavelengths by the cloud-free upper atmosphere.

The different colors in Saturn's atmosphere are due to particles whose composition is yet to be determined. This image was obtained with the Cassini spacecraft narrow angle camera on July 30, 2004, at a distance of 7.6 million kilometers (4.7 million miles) from Saturn.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

http://www.jpl.nasa.gov/

NASA and industry engineers successfully completed the first test of the Ares I rocket's three main parachutes Wednesday. The parachutes -- the largest rocket parachutes ever manufactured -- are designed to slow the rapid descent of the rocket's spent first-stage motor, permitting its recovery for use on future flights.



The Ares I, the first rocket in NASA's Constellation Program, is designed to launch explorers aboard the Orion crew capsule on journeys to the International Space Station, the moon and beyond. The three main parachutes measure 150 feet in diameter and weigh 2,000 pounds each. They are a primary element of the rocket's deceleration system, which also includes a pilot parachute and drogue parachute. Deployed in a cluster, the main parachutes open at the same time, providing the drag necessary to slow the descent of the huge solid rocket motor to a soft landing in the ocean.

"The successful main chute cluster test today confirms the development and design changes we have implemented for the Ares I first stage recovery system," said Ron King, Ares I first stage deceleration subsystem manager for the Ares Projects at NASA's Marshall Space Flight Center in Huntsville, Ala. "Thanks to our great, collaborative team, the test went as anticipated, and all of our design objectives were met."

Engineers from Marshall managed the team that conducted this first cluster test at the U.S. Army's Yuma Proving Ground near Yuma, Ariz. This was the eighth in an ongoing series of flight tests supporting development of the Ares I recovery system. Researchers dropped the 41,500-pound load from a U.S. Air Force C-17 aircraft flying at an altitude of 10,000 feet. The parachutes and all test hardware functioned properly and landed safely.

As the test series progresses, engineers will perform three classifications of testing: development, design load and overload. Each level of testing is designed to fully test the performance of the new parachute design with different size payloads under varying conditions. The next test in the cycle -- scheduled for fall 2009 -- will involve the first design limit load test of a single main parachute.

The Ares I recovery system currently under development uses parachutes similar to those used for the four-segment space shuttle boosters, but the parachutes have been redesigned to accommodate the new requirements of the Ares I first stage. The Ares I launch vehicle will have a five-segment solid rocket booster that will fly faster and fall from a higher altitude than the shuttle boosters.

ATK Space Systems near Promontory, Utah, is the prime contractor for the first stage booster. ATK's subcontractor, United Space Alliance of Houston, is responsible for design, development and testing of the parachutes at its facilities at NASA's Kennedy Space Center in Florida.

NASA's Johnson Space Center in Houston manages the Constellation Program. Marshall manages the Ares Projects. The U.S. Army's Yuma Proving Ground provides the test range, support facilities and equipment to NASA for parachute testing.

http://www.nasa.gov/

Imagine Captain Kirk being beamed back to the Starship Enterprise and two versions of the Star Trek hero arriving in the spacecraft's transporter room.


It happened 40 years ago in an episode of the TV science fiction classic, and now scientists at the University of York and colleagues in Japan have managed something strikingly similar in the laboratory - though no starship commander was involved.

The first experimental demonstration of quantum telecloning has been achieved by scientists at the University of Tokyo, the Japan Science and Technology Agency, and the University of York. The work is reported in the latest issue of Physical Review Letters. Telecloning combines cloning (or copying) with teleportation (i.e., disembodied transport).

The scientists have succeeded in making the first remote copies of beams of laser light, by combining quantum cloning with quantum teleportation into a single experimental step. Telecloning is more efficient than any combination of teleportation and local cloning because it relies on a new form of quantum entanglement - multipartite entanglement.

Professor Sam Braunstein, of the Department of Computer Science at York, said: "Quantum mechanics allows us to do things which we previously thought were impossible. In 1998, I was involved in an experiment in America which was one of the first for quantum teleportation in which we transmitted a beam of light without it crossing the physical medium in between.

"This new experiment is an extension of that work. Whether it will change the world for individuals or is just of use to governments or big companies is hard to say. Any new protocol is like a new-born baby and it has to develop, but we know this one could be used to tap cryptographic channels.

"Quantum cryptographic protocols are so secure that they can not only discover tapping but also where and how much information is leaking out. Now, using telecloning, the identity and location of the eavesdropper can be concealed."

Telecloning and teleportation may no longer be theories, but we are still a long way from teleporting people.

Professor Braunstein said: "What we know is that it would be incredibly difficult and from the perspective of today's technology, a completely outrageous thing. But in 100 years, who knows?"



http://www.york.ac.uk/

The first robotic mission to return samples to Earth from Mars took a further step toward realisation with the recent publication of a mission design report by the iMARS Working Group. The report defines key elements of the future internationally-funded mission involving the cooperation of ESA, NASA and other national agencies.


iMARS, which stands for the International Mars Architecture for the Return of Samples, is a committee of the International Mars Exploration Working Group made up of scientists, engineers, strategic planners, and managers. The report, which comes after months of deliberation, outlines the scientific and engineering requirements of such an international mission to be undertaken in the timeframe 2020-2022.

The Mars Sample Return mission is an essential step with respect to future exploration goals and the prospect of establishing a future human mission to Mars. Returned samples will increase the knowledge of the properties of Martian soil and contribute significantly to answering questions about the possibility of life on the Red Planet. This mission will improve our understanding of the Mars environment to support planning for the future human exploration.

The iMARS report outlines the mission’s scientific objectives including the types and quantities of samples to be returned from Mars; the different mission elements (launchers, spacecraft, Mars lander, a rover and a Mars ascent vehicle) and ground processing facilities necessary to contain and analyse the received samples in a protected environment. A preliminary timeline for the mission and approximate budget has also been defined.

“Exploration is gaining momentum year by year, as is the experience and knowledge gained by ESA and its international partners in this area” said Bruno Gardini ESA’s Exploration Programme Manager in the Directorate of Human Spaceflight and iMARS study leader. “The information we gain from current Mars missions and from the ISS provide a basis not only for future robotic missions but also a stepping stone for the human exploration missions.”


http://www.esa.int/esaCP/index.html

According to the international space agencies, "space weather" is the single greatest obstacle to deep space travel. Radiation from the sun and cosmic rays pose a deadly threat to astronauts in space. New research shows how knowledge gained from the pursuit of nuclear fusion research may reduce the threat to acceptable levels, making humanity's first mission to Mars a much greater possibility.


The solar energetic particles, although just part of the 'cosmic rays' spectrum, are of greatest concern because they are the most likely to cause deadly radiation damage to the astronauts.

Large numbers of these energetic particles occur intermittently as "storms" with little warning and are already known to pose the greatest threat to man. Nature helps protect the Earth by having a giant "magnetic bubble" around the planet called the magnetosphere.

The Apollo astronauts of the 1960's and 70's who walked upon the Moon are the only humans to have travelled beyond the Earth's natural "force field" – the Earth's magnetosphere. With typical journeys on the Apollo missions lasting only about 8 days, it was possible to miss an encounter with such a storm; a journey to Mars, however, would take about eighteen months, during which time it is almost certain that astronauts would be enveloped by such a "solar storm".

Space craft visiting the Moon or Mars could maintain some of this protection by taking along their very own portable "mini"-magnetosphere. The idea has been around since the 1960's but it was thought impractical because it was believed that only a very large (more than 100km wide) magnetic bubble could possibly work.

Researchers at the Science and Technology Facilities Council's Rutherford Appleton Laboratory, the Universities of York, Strathclyde and IST Lisbon, have undertaken experiments, using know-how from 50 years of research into nuclear fusion, to show that it is possible for astronauts to shield their spacecrafts with a portable magnetosphere - scattering the highly charged, ionised particles of the solar wind and flares away from their space craft.

Computer simulations done by a team in Lisbon with scientists at Rutherford Appleton last year showed that theoretically a very much smaller "magnetic bubble" of only several hundred meters across would be enough to protect a spacecraft.

Now this has been confirmed in the laboratory in the UK using apparatus originally built to work on fusion. By recreating in miniature a tiny piece of the Solar Wind, scientists working in the laboratory were able to confirm that a small "hole" in the Solar Wind is all that would be needed to keep the astronauts safe on their journey to our nearest neighbours.

Dr. Ruth Bamford, one of the lead researchers at the Rutherford Appleton Laboratory, said, "These initial experiments have shown promise and that it may be possible to shield astronauts from deadly space weather."


http://www.iop.org/

In the last year space agencies in the United States, Europe, China, Japan and India have announced their intention to resume human exploration of the Solar system, beginning with the Moon and perhaps ultimately moving on to Mars. But travel beyond the immediate vicinity of the Earth carries significant risks for astronauts, not the least of which is the exposure to sometimes high levels of radiation. Now a team of scientists at the Rutherford Appleton Laboratory are set to construct an experimental magnetic shield that would protect explorers in their journeys between the planets. Dr Ruth Bamford presented this idea at the Royal Astronomical Society National Astronomy Meeting in Preston.

Cosmic rays and radiation from the Sun itself can cause acute radiation sickness in astronauts and even death. Between 1968 and 1973, the Apollo astronauts going to the moon were only in space for about 10 days at a time and were simply lucky not to have been in space during a major eruption on the sun that would have flooded their spacecraft with deadly radiation. In retrospect Neil Armstrong’s ‘one small step for Man’ would have looked very different if it had.

On the International Space Station there is a special thick-walled room to which the astronauts have had to retreat during times of increased solar radiation. However on longer missions the astronauts cannot live within shielded rooms, since such shielding would add significantly to the mass of the spacecraft, making them much more expensive and difficult to launch. It is also now known that the ‘drip-drip’ of even lower levels of radiation can be as dangerous as acute bursts from the sun.

On the surface of the Earth we are protected from radiation by the thick layers of the atmosphere. And the terrestrial magnetic field extends far into space, acting as a natural ‘force field’ to further protect our planet and deflecting the worst of the energetic particles from the Sun by creating a ‘plasma barrier’.

Now scientists at the Rutherford Appleton Laboratory in Oxfordshire plan to mimic nature. They will build a miniature magnetosphere in a laboratory to see if a deflector shield can be used to protect humans living on space craft and in bases on the Moon or Mars.

In order to work, an artificial mini-magnetosphere on a space craft will need to utilise many cutting edge technologies, such as superconductors and the magnetic confinement techniques used in nuclear fusion.

Thus science is following science fiction once again. The writers of Star Trek realised that any space craft containing humans would need protection from the hazardous effects of cosmic radiation. They envisioned a ‘deflector shield’ spreading out from the Starship Enterprise that the radiation would bounce off. These experiments will help to establish whether this idea could one day become a practical reality.


http://www.ras.org.uk/

Alien creatures are the least of NASA's worries when it comes to moon travel. There are several potential threats to future missions - with space radiation at the top of the list. Now, a group of students at North Carolina State University has developed a "blanket" of sorts that covers lunar outposts - the astronauts' living quarters - to provide astronauts protection against radiation while also generating and storing power.
Astronauts who previously traveled to the moon had little protection against radiation, but were only exposed to it for a short amount of time. NASA's plans to return astronauts to the moon by 2020 - and to potentially keep them there for several months at a time - could be stymied by space radiation.

The surface of the moon is exposed to cosmic rays and solar flares - making radiation hard to stop with shielding. When these rays hit matter, they produce a dangerous spray of secondary particles which, when penetrating human flesh, can damage DNA, boosting the risk of cancer and other maladies.

Groups all over the globe are trying to determine ways to combat space radiation - including Michael Sieber, Ryan Boyle and Anne Tomasevich, all recent graduates of the textile engineering program at NC State. Their design of a lunar radiation shield with the ability to protect its inhabitants from radiation was reviewed by a panel of industry experts and chosen as one of 10 undergraduate abstract finalists in the Revolutionary Aerospace Systems Concepts Academic Linkage (RASC-AL) competition.

Sponsored by NASA and the National Institute of Aerospace, the RASC-AL competition challenges university students to think about what sorts of conditions astronauts will face when returning to the moon, then design projects that might become part of actual lunar exploration.

"We had many factors to consider in developing this outpost cover - not just being able to protect against radiation," Sieber says. "The product needed to be as lightweight as possible to feasibly fit on the transportation module, and have the ability to be easily erected by a minimum number of astronauts for immediate use once landing on the moon."

"These obstacles are where our knowledge of textile properties will give us an advantage," adds Dr. Warren Jasper, professor of textile engineering and advisor for the project. "This is a competition aimed at aerospace engineering students, but we understand the properties associated with different textile materials, and that gives us unique insight on how to troubleshoot some of these issues."

The "lunar texshield" is made from a lightweight polymer material that has a layer of radiation shielding that deflects or absorbs the radiation so astronauts are only exposed to a safe amount. The outermost surface of the shield includes a layer of solar cells to generate electricity, backed up by layers of radiation-absorbing materials. The advantages of the materials used in the design include flexibility, large surface area, ease of transportation, ease of construction and the ability to have multiple layers of independent functional fabrics.

The students will present their lunar texshield at the 2009 RASC-AL Forum held June 1-3 in Cocoa Beach, Fla. The project will be judged by a steering committee made up of experts from NASA, industry and universities.

"We aren't even sure what the prize is for being named first place - but that wasn't what was important to us," Sieber says. "We used what we've learned throughout our college careers and were able to apply that logic to provide a solution a real-world problem. That is what is cool to us."


http://www.ncsu.edu/

Observations of the white dwarf star, Sirius B, made with NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite give astronomers firm new evidence that mathematical models widely used to predict white dwarf star mass and radius are correct.


Jay B. Holberg of the University of Arizona Lunar and Planetary Laboratory is presenting the result today at the American Astronomical Society in San Diego.

The FUSE result is important because Sirius B is one of the few stars that astronomers have to test their ideas on the relationship between mass and radius for white dwarf stars. White dwarf stars are small but astonishingly dense stars. Sirius B is the size of the Earth and as massive as the sun.

Theory that describes how white dwarf stars can exist emerged in the early 1930s, when Subramanyan Chandrasekhar – or Chandra, as he was known – calculated the limit to a white dwarf's mass by applying Einstein's theory of special relativity. It was one of the first applications of quantum mechanics to large physical systems in the sky.

No white dwarf star could be more than 1.4 times as massive as the sun or it will collapse, Chandra predicted.

"Chandra was the first person to lay out the essential details of how white dwarfs sustain themselves, and it is very, very different from the sun or any other stars," Holberg said.

Unlike most white dwarfs, Sirius B is part of a binary system, and astronomers can determine the mass of stars in a binary system.

"Having a binary system – when two stars orbit one another - is virtually the only way you can fundamentally measure the mass of a star," Holberg said. "You observe their orbits, get the period, know how far away they are, and you can find the sum of the two star masses. If you can time the orbits and know how far apart the stars are, you can determine the individual star masses. That's the most accurate way, the acceptable way to determine star masses.

"But this star has always been devilishly difficult to observe," Holberg said. The primary star in the system, Sirius A, is 8 light years from Earth and has twice the mass of the sun. It is the brightest star in the night sky, visible below Orion. Sirius B is 10,000 times dimmer than Sirius A. Astronomers can’t even see the white dwarf companion when it comes closest to the primary star during its 50-year, very elongated orbit around Sirius A.

For the post several years, Holberg and colleagues have observed Sirius B with the Voyager and Extreme Ultraviolet Explorer spacecrafts. They have refined the star's temperature and gravity - gravity being the gravitational field at the surface of the star - to refine estimates of its mass and radius.

"The methods we're using are spectroscopic. They infer the mass from synthetic models that we produce from measurements of temperature and gravity, the only two parameters of matter for a white dwarf."

Holberg and his colleagues published the best determination of Sirius B's mass-radius relationship in 1998, but that was "still far from definitive," Holberg said. "That is, the uncertainties are so large, that while these studies define the basic relationship, they don’t tell you lots of details we need to know about these stars."

The FUSE observations gave Holberg and his colleagues better spectral data on Sirius B's gravitational field and temperature needed to calculate mass. "And this is a very clean spectrum. We rolled the FUSE spacecraft to keep Sirius A from contaminating the spectrum, and we succeeded very well.

"The mathematical model very well predicts our results on the gravitational field, temperature and brightness of this white dwarf star," Holberg said. "That helps us determine the radius of the star. What we really want to do is determine mass and radius to within one percent. By verifying the Chandrasekhar limit, you put a great deal of astrophysics on much firmer footing," he added.

"Astronomy has reached the level where you can make very definitive comparisons between the models and the observations. And it looks like we are going to come out to what we expected," Holberg said.


http://www.arizona.edu/

Using the European Southern Observatory's Very Large Telescope in Chile, an international team of researchers discovered a brown dwarf belonging to the 24th closest stellar system to the Sun. Brown dwarfs are intermediate objects that are neither stars nor planets. This object is the third closest brown dwarf to the Earth yet discovered, and one of the coolest, having a temperature of about 750 degrees Centigrade. It orbits a very small star at about 4.5 times the mean distance between the Earth and the Sun. Its mass is estimated to be somewhere between 9 and 65 times the mass of Jupiter.


At a time when astronomers are peering into the most distant Universe, looking at objects as far as 13 billion light-years away, one may think that our close neighbourhood would be very well known. Not so. Astronomers still find new star-like objects in our immediate vicinity. Using ESO's VLT, they just discovered a brown dwarf companion to the red star SCR 1845-6357, the 36th closest star to the Sun.

"This newly found brown dwarf is a valuable object because its distance is well known, allowing us to determine with precision its intrinsic brightness", said team member Markus Kasper (ESO). "Moreover, from its orbital motion, we should be able in a few years to estimate its mass. These properties are vital for understanding the nature of brown dwarfs."

To discover this brown dwarf, the team used the high-contrast adaptive optics NACO Simultaneous Differential Imager (SDI) on ESO's Very Large Telescope, an instrument specifically developed to search for extrasolar planets. The SDI camera enhances the ability of the VLT and its adaptive optics system to detect faint companions that would normally be lost in the glare of the primary star. In particular, the SDI camera provides additional, often very useful spectral information which can be used to determine a rough temperature for the object without follow-up observations.

Located 12.7 light-years away from us, the newly found object is nevertheless not the closest brown dwarf. This honour goes indeed to the two brown dwarfs surrounding the star Epsilon Indi, located 11.8 light years away.

However, this newly discovered brown dwarf is unique in many aspects. "Besides being extremely close to Earth, this object is a T dwarf - a very cool brown dwarf - and the only such object found as a companion to a low-mass star," said Beth Biller, a graduate student at the University of Arizona and lead author of the paper reporting the discovery. "It is also likely the brightest known object of its temperature because it is so close."

The discovery of this brown dwarf hints that, at least close to the Sun, cool brown dwarfs prefer to be part of a couple with a star or another brown dwarf, rather than wandering alone in the cosmic emptiness. Indeed, of the seven cool brown dwarfs that reside within 20 light years of the Sun, five have a companion.

"This has wide-ranging implications for theories of brown dwarf formation, which, until now, tend to favour the production of single brown dwarfs," said team member Laird Close (University of Arizona).

http://www.eso.org/public/

Astronomers have found three brown dwarfs with estimated masses of less than 10 times that of Jupiter, making them among the youngest and lowest mass sub-stellar objects detected in the solar neighbourhood to date.

The observations were made by a team of astronomers working at the Laboratoire d'Astrophysique de l'Observatoire de Grenoble (LAOG), France, using the Canada-France-Hawaii Telescope (CFHT). Andrew Burgess will be presenting the discovery at the European Week of Astronomy and Space Science at the University of Hertfordshire, Hatfield, on Wednesday 22nd April.

The dwarfs were found in a star forming region named IC 348, which lies almost 1000 light years from the Solar System towards the constellation of Perseus. This cluster is approximately 3 million years old – extremely young compared to our 4.5 billion year old Sun – which makes it a good location in order to search for the lowest mass brown dwarfs. The dwarfs are isolated in space, which means that they are not orbiting a star, although they are gravitationally bound to IC 348. Their atmospheres all show evidence of methane absorption which was used to select and identify these young objects.

"There has been some controversy about identifying young, low mass brown dwarfs in this region. An object of a similar mass was discovered in 2002, but some groups have argued that it is an older, cooler brown dwarf in the foreground coinciding with the line of sight. The fact that we have detected three candidate low-mass dwarfs towards IC 348 supports the finding that these really are very young objects," said Burgess.

The team set out to find a population of these brown dwarfs in order to help theoreticians develop more accurate models for the distribution of mass in a newly-formed population, from high mass stars to brown dwarfs, which is needed to test current star formation theories. The discovery of the dwarfs in IC 348 has allowed them to set new limits on the lowest mass objects.

"Finding three candidate low-mass dwarfs towards IC 348 backs up predictions for how many low-mass objects develop in a new population of stars. Brown dwarfs cool with age and current models estimate that their surfaces are approximately 900-1000 degrees Kelvin (about 600-700 degrees Celsius). That’s extremely cool for objects that have just formed, which implies that they have the lowest masses of any of this type of object that we’ve seen to date," said Burgess.


http://www.ras.org.uk/

Boring” light from red dwarf star Gliese 581 means better odds for extraterrestrial life in that planetary system, according to University of British Columbia astronomer Jaymie Matthews.

Approximately 20.5 light years from the Earth, Gliese 581 made the headlines in April 2007 when European scientists discovered a planet, named Gliese 581c. Dubbed “SuperEarth,” the planet orbits Gliese 581 and could have water -- and thus able to support life.

“The Gliese 581 system is the first to be found -- beyond our own Earth -- that might have a liveable planet,” said Matthews.

Using Canada Space Agency’s suitcase-sized space telescope, the Microvariability and Oscillations of STars (MOST), Matthews put Gliese 581 on a six-week scientific stakeout following the April discovery. He will present his findings today at the Canadian Astronomical Society’s annual meeting in Kingston, Ontario.

Matthews and his team searched for the subtle dips in the light from the star when the planet’s orbit carried it directly between the star and the Earth, resulting in a “mini-eclipse” every 13 days. The depth of the dips would help researchers determine the size of the planet Gliese 581c, while the behaviour of the starlight at other times would help astronomers gauge the suitability of Gliese 581 as a “home star,” a star able to sustain life on planets around it.

“Gliese 581 seems remarkably stable over the six weeks it was monitored by MOST,” said Matthews. “The brightness of the star changed by only a few tenths of a percent over that time. This level of stability means that it provides a stable source of light -- hence heat -- to the surface of planet Gliese 581c.

“The climate there should not be a wild rollercoaster ride that would make it difficult for life to get a foothold,” said Matthews. “It also suggests the star is quite old, and settled in its ways, and that the planets around it have probably been around for billions of years.”

It took approximately 3.5 billion years for life on Earth to reach the level of complexity that we call human, said Matthews. “So if Gliese 581 has been around for at least that long, it’s more encouraging for the prospects of complex life on any planet around it.”

With space missions like MOST, the French satellite COROT, which joined MOST in orbit late last December, and the American Kepler mission due for launch in November 2008, Matthews predicts that other ‘Earthy’ worlds will come to light in the coming months and years.

“Some of them will have orbits that produce planetary alignments,” said Matthews. “Not the kind that excites somebody reading a horoscope but the kind that’s exciting for astronomers because they will allow us to test our models of alien worlds -- worlds that might be homes to neighbours in our Galactic city, the Milky Way.”

MOST is a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute for Aerospace Studies and the University of British Columbia, with the assistance of the University of Vienna.

http://www.astro.ubc.ca/MOST/

Exoplanet researchers have discovered the lightest exoplanet found so far. The planet, “e”, in the famous system Gliese 581, is only about twice the mass of our Earth. The team also refined the orbit of the planet Gliese 581 d, first discovered in 2007, placing it well within the habitable zone, where liquid water oceans could exist.
These amazing discoveries are the outcome of more than four years of observations using the most successful low-mass-exoplanet hunter in the world, the HARPS spectrograph attached to the 3.6-metre ESO telescope at La Silla, Chile.

“The holy grail of current exoplanet research is the detection of a rocky, Earth-like planet in the ‘habitable zone’ — a region around the host star with the right conditions for water to be liquid on a planet’s surface,” says Michel Mayor from the Geneva Observatory, who led the European team to this stunning breakthrough.

Planet Gliese 581 e orbits its host star – located only 20.5 light-years away in the constellation Libra (“the Scales”) — in just 3.15 days. “With only 1.9 Earth-masses, it is the least massive exoplanet ever detected and is, very likely, a rocky planet”, says co-author Xavier Bonfils from Grenoble Observatory.

Being so close to its host star, the planet is not in the habitable zone. But another planet in this system appears to be. From previous observations — also obtained with the HARPS spectrograph at ESO’s La Silla Observatory and announced two years ago — this star was known to harbour a system with a Neptune-sized planet and two super-Earths. With the discovery of Gliese 581 e, the planetary system now has four known planets, with masses of about 1.9 (planet e), 16 (planet b), 5 (planet c), and 7 Earth-masses (planet d). The planet furthest out, Gliese 581 d, orbits its host star in 66.8 days.

“Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star,” says team member Stephane Udry. The new observations have revealed that this planet is in the habitable zone, where liquid water could exist. “‘d’ could even be covered by a large and deep ocean — it is the first serious 'water world' candidate,” continued Udry.

The gentle pull of an exoplanet as it orbits the host star introduces a tiny wobble in the star’s motion — only about 7 km/hour, corresponding to brisk walking speed — that can just be detected on Earth with today’s most sophisticated technology. Low-mass red dwarf stars such as Gliese 581 are potentially fruitful hunting grounds for low-mass exoplanets in the habitable zone. Such cool stars are relatively faint and their habitable zones lie close in, where the gravitational tug of any orbiting planet found there would be stronger, making the telltale wobble more pronounced. Even so, detecting these tiny signals is still a challenge, and the discovery of Gliese 581 e and the refinement of Gliese 581 d’s orbit were only possible due to HARPS’s unique precision and stability.

“It is amazing to see how far we have come since we discovered the first exoplanet around a normal star in 1995 — the one around 51 Pegasi,” says Mayor. “The mass of Gliese 581 e is 80 times less than that of 51 Pegasi b. This is tremendous progress in just 14 years.”

The astronomers are confident that they can still do better. “With similar observing conditions an Earth-like planet located in the middle of the habitable zone of a red dwarf star could be detectable,” says Bonfils. “The hunt continues.”

http://www.eso.org/public/

The first detailed images of a binary asteroid system reveal a bizarre world where the highest points on the surface are actually the lowest, and the two asteroids dance in each other's gravitational pull.

A binary asteroid is a system where two asteroids orbit around one another, like a mini Earth-moon system, said Daniel Scheeres, University of Michigan associate professor of aerospace engineering. The new results are scheduled to appear Oct. 12 in the journal Science in a pair of papers by Scheeres and Dr. Steven Ostro of the NASA/Caltech Jet Propulsion Laboratory.

The radar images of asteroid KW4 (the official full designation is 66391 1999 KW4) were obtained in May 2001, when the asteroid passed 4.8 million kilometers from Earth. Previously, KW4 was classified as a potentially hazardous asteroid (PHA) because of the proximity of the asteroid's orbit to Earth's orbit. The new observations show that there is no chance of KW4 hitting Earth within at least the next 1,000 years, Scheeres said.

"The KW4 results have profound consequences for ideas about mitigation of the asteroid collision hazard," Scheeres said.

The observations show that the larger object is spinning in its orbit so fast that it has been flattened into a kind of flying saucer shape, said Scheeres. Because of this, the mountainous region along the center of the asteroid actually forms the lowest part on the asteroid. In fact the asteroid is spinning so fast that the equatorial ridge is very close to lifting off the surface and spinning into space, he said.

Another interesting finding is that the two bodies in the asteroid system are orbiting so closely that they are caught in each other's gravitational pull.

"They are so close together that when one rotates it affects the other's movements," Scheeres said.

Based on the observations, the KW4 binary asteroid appears to have formed either from tidal disruption during a close pass by the Earth or from sunlight shining on it, so that it spins so fast that it eventually broke into two pieces. The odd shapes of asteroids cause them to sometimes spin faster and faster when illuminated by the sun, acting a bit like a solar sail, Scheeres said. This is called the YORP effect.

The recent findings also confirm that the asteroids are only floating piles of rubble held together by gravity and not a solid mass.


http://www.umich.edu/

In the hit 1998 movie Armageddon, Bruce Willis and Ben Affleck blew up an asteroid to save the world. While the film was science fiction, the chances of an asteroid hitting the Earth one day are very real ― and blowing up an asteroid in real life, says a Tel Aviv University researcher, will be more complicated than in the movies.
Astrophysicists agree that the best method for avoiding a catastrophic collision would be to change the path of the asteroid heading toward our planet. “For that to work, we need to be able to predict what would happen if we attempt an explosion,” says Tel Aviv University doctoral student David Polishook, who is studying asteroids with his supervisor Dr. Noah Brosch at the Department of Geophysics and Planetary Sciences.

Polishook and Brosch are among the few scientists in the world researching the structure and composition of asteroids a critical first step in learning how to destroy them before they reach the Earth’s atmosphere. Their research could prevent catastrophe: blowing up an asteroid may create many equally dangerous smaller asteroids of about 100 meters each in diameter ― twice the size of the asteroid that created the famous Arizona crater.

Looking on the Bright Sides

“The information we are investigating can have a tremendous impact on future plans to alter the course of asteroids on a collision course with Earth,” says Polishook. “Science needs to know whether asteroids are solid pieces of rock or piles of gravel, what forces are holding them together, and how they will break apart if bombed.”

By observing the waxing and waning brightness of far-away asteroids, Polishook is able to examine the shape, spin period and surface composition of these flying rocks. “This is a good way of evaluating what asteroids are made of,” says Polishook, who takes measurements on an almost daily basis at Tel Aviv University's Wise Observatory.

As part of their observations, the researchers used the fact that small asteroids change their rotation rate, accelerating or slowing down during short periods, as often as every 100,000 years. Compared to the age of the solar system 4.5 billion years that is an extremely fast change, says Polishook.

The most recent results of their research were presented at the 2008 meeting of Asteroids, Comets and Meteors, sponsored by the Johns Hopkins University Applied Physics Laboratory in Baltimore.

Size Matters

An asteroid’s rotation and acceleration are influenced by sunlight the “YORP Effect.” If the YORP effect causes an asteroid to rotate faster than one revolution in 2.2 hours, it will break apart.

To understand how the YORP Effect works on asteroids, Tel Aviv University researchers examined several variables relating to these asteroids, including size and location. They concluded that size is the most important factor in determining how an asteroid’s rotation rate accelerates according to the YORP Effect.

“We think this adds an important clue to how asteroids will behave should a space agency need to knock one off-course to prevent a collision with earth,” Polishook notes.


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