Thursday, February 28, 2013
Saturday, February 23, 2013
Spray-Painting Asteroids Could Protect Earth from Space Rock Threat
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 An artist's illustration of an asteroid flying near Earth.CREDIT: via Texas A&M University |
The dramatic space rock events of last week highlighted the need in many people's minds for a viable asteroid-deflection strategy, and one scientist thinks he has a good candidate — paint.
On Friday (Feb. 15), the 130-foot (40 meters) asteroid 2012 DA14 gave Earth a historically close shave, missing the planet by just 17,200 miles (27,000 kilometers). Hours earlier, a 55-foot (17 m) object exploded over the Russian city of Chelyabinsk, damaging thousands of buildings and injuring 1,200 people.
The asteroid encounters served as a reminder that Earth sits in the middle of a cosmic shooting gallery, scientists say, and that destructive impacts are inevitable in the future unless humanity takes action.
The scheme would use powdered paint, which the sun's rays would then cure into a smooth coating. The paint would probably have to be applied long before any potential impact — years or decades, perhaps — to give the Yarkovsky effect enough time to make a difference.One form of action could involve dusting a threatening asteroid with a thin coat of paint. The paint would change the amount of sunlight reflected by the space rock, potentially nudging it away from Earth through the accumulated push provided by many thermal photons as they radiate from the asteroid's surface. (This force is called the Yarkovsky effect, after the Russian engineer who first described it around the turn of the 20th century.) [Photos: Asteroids in Deep Space]
"I have to admit the concept does sound strange, but the odds are very high that such a plan would be successful and would be relatively inexpensive," Dave Hyland, of Texas A&M University, said in a statement. "The science behind the theory is sound. We need to test it in space."
NASA is interested in Hyland's idea and has approached the researcher to discuss developing such a space test, Texas A&M officials said. MHyland is not the only scientist who thinks paint could save Earth from a cataclysmic impact. Last year, an MIT graduate student proposed launching a spacecraft that would bombard a threatening asteroid with paint-filled pellets. The idea won the 2012 Move an Asteroid Technical Paper Competition, which was sponsored by the United Nations' Space Generation Advisory Council.ove an Asteroid
Whatever deflection strategies researchers devise, the first step toward safeguarding the Earth is to detect and map the orbits of potentially hazardous objects, Hyland said. One million or more asteroids are thought to lurk in near-Earth space, but just 9,600 of them have been discovered to date.
"The smaller ones like DA14 are not discovered as soon as others, and they could still cause a lot of damage should they hit Earth," Hyland said. "It is really important for our long-term survival that we concentrate much more effort discovering and tracking them, and developing as many useful technologies as possible for deflecting them."
Friday, February 22, 2013
Thursday, February 21, 2013
Wednesday, February 20, 2013
Has Dark Matter Finally Been Found?
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 The powerful Alpha Magnetic Spectrometer-2 (AMS) is visible at center left. The blackness of space and Earth's horizon provide the backdrop for the scene, on May 20, 2011 (Flight Day 5 of the STS-134 shuttle mission).CREDIT: NASA |
BOSTON — Big news in the search for dark matter may be coming in about two weeks, the leader of a space-based particle physics experiment said today (Feb. 17) here at the annual meeting of the American Association for the Advancement of Science.
That's when the first paper of results from the Alpha Magnetic Spectrometer, a particle collector mounted on the outside of the International Space Station, will be submitted to a scientific journal, said MIT physicist Samuel Ting, AMS principal investigator.
Though Ting was coy about just what, exactly, the experiment has found, he said the results bear on the mystery of dark matter, the invisible stuff thought to outnumber regular matter in the universe by a factor of about six to one. "It will not be a minor paper," Ting said, hinting that the findings were important enough that the scientists rewrote the paper 30 times before they were satisfied with it. Still, he said, it represents a "small step" in figuring out what dark matter is, and perhaps not the final answer. [Photos: AMS Hunts Exotic Particles In Space]
Some physics theories suggest that dark matter is made of WIMPS (weakly interacting massive particles), a class of particles that are their own antimatter partner particles. When matter and antimatter partners meet, they annihilate each other, so if two WIMPs collided, they would be destroyed, releasing a pair of daughter particles — an electron and its antimatter counterpart, the positron, in the process.
The Alpha Magnetic Spectrometer has the potential to detect the positrons and electrons produced by dark matter annihilations in the Milky Way. The $2 billion machine was installed on the International Space Station in May 2011, and so far, it has detected 25 billion particle events, including about 8 billion electrons and positrons. This first science paper will report how many of each were found, and what their energies are, Ting said.
If the experiment detected an abundance of positrons peaking at a certain energy, that could indicate adetection of dark matter, because while electrons are abundant in the universe around us, there are fewer known processes that could give rise to positrons.
"The smoking gun signature is a rise and then a dramatic fall" in the number of positrons with respect to energy, because the positrons produced by dark matter annihilation would have a very specific energy, depending on the mass of the WIMPs making up dark matter, said Michael Turner, a cosmologist at the University of Chicago who is not involved in the AMS project. "That's the key signature that would arise."
Another telling sign will be the question of whether positrons appear to be coming from one direction in space, or from all around. If they're from dark matter, scientists expect them to be spread evenly through space, but if they're created by some normal astrophysical process, such as a star explosion, then they would originate in a single direction.
"There is a lot of stuff that can mimic dark matter," said theoretical physicist Lisa Randall of Harvard University, who is also not involved in the project but said she's eagerly awaiting the AMS results. "In these experiments the question is when do you have antimatter that could be explained by astrophysical sources, and when do you have something that really could be an indication that you have something new?"
Regardless of whether AMS has found dark matter yet, the scientists said they expected the question of dark matter's origin to become clearer soon. In addition to AMS, other experiments such as the Large Hadron Collider in Switzerland, and underground dark matter detectors buried around the world, could also make a discovery in the near future.
"We believe we're on the threshold of discovery," Turner said. "We believe this will be the decade of the WIMP."
Sunday, February 17, 2013
What Are an Asteroid, a Meteor and a Meteorite?
 What appears to be a meteor trail over eastern Russia is seen in this image released Feb. 15, 2013, by the Russian Emergency Ministry. The meteor fall included a massive blast, according to Russian reports.CREDIT: Russian Emergency Ministry |
The terms asteroid, meteor, meteorite and meteoroid get tossed around recklessly, especially when two of them threaten the Earth on the same day. Here's a quick explainer:
An asteroid is a rocky object in space that's smaller than a planet — they're sometimes called minor planets or planetoids, according toNASA. Other sources refer to them loosely as "space debris," or leftover fragments from the formation of the solar system (like the extra pieces that remain after constructing a build-it-yourself bookcase from IKEA).
There are millions of asteroids orbiting the sun, some 750,000 of which are found in the asteroid belt, a vast ring of asteroids located between the orbits of Mars and Jupiter. Asteroids can be as large as hundreds of kilometers wide: The asteroid Ceres, sometimes referred to as a dwarf planet, is 940 km (584 miles) wide. Asteroids have no atmosphere, but many are large enough to exert a gravitational pull — some, in fact, have one or two companion moons, or they form binary systems, in which two similarly sized asteroids orbit each other.
Scientists are eager to study asteroids because they reveal so much information about the early formation of our solar system some 4.6 billion years ago. One way to study them is to observe them when they come close to Earth, as 2012 DA14 will today (Feb. 15).
A meteor is an asteroid or other object that burns and vaporizes upon entry into the Earth's atmosphere; meteors are commonly known as "shooting stars." If a meteor survives the plunge through the atmosphere and lands on the surface, it's known as a meteorite.
Meteorites are usually categorized as iron or stony. As the name implies, iron meteorites are composed of about 90 percent iron; stony meteorites are made up of oxygen, iron, silicon, magnesium and other elements.
And meteoroids? That's a general term describing small particles of comets or asteroids that are in orbit around the sun. There's no universally accepted, hard-and-fast definition (based on size or any other characteristic) that distinguishes a meteoroid from an asteroid — they're simply smaller than asteroids.
Only when these objects enter the atmosphere are they referred to as meteors, like the meteor that was seen over Russia today. Because that meteor exploded in the atmosphere, the resulting fireball is known as a bolide. Again, there's no precise definition of a bolide — most astronomers understand a bolide as simply a very bright fireball.
Tuesday, February 12, 2013
Monday, February 11, 2013
Sunday, February 10, 2013
"For most, it's the deadly centerpiece of the film Star Wars. But in truth, real death stars are in the final stage of life before they explode into supernovae and, occasionally, the biggest blast in the universe--the gamma ray burst (GRB). One death star, named WR104, lurks 8,000 light-years from Earth and some believe its GRB arrow is aimed directly at us. A death star galaxy named 3C321 is a terrifying vision of what could one day befall the Milky Way galaxy: a companion galaxy's black hole is hammering it with a constant blast of high-energy particles, wreaking havoc with its celestial bodies. Nearby, Death Stars Eta Carinae and Betelgeuse burn through their fuel supplies as they hurtle toward extinction--and possibly a violent ending that's too close for comfort. "
Saturday, February 9, 2013
4.5 Billion 'Alien Earths' May Populate Milky Way
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 This artist’s conception shows a hypothetical habitable planet with two moons orbiting a red dwarf star. Astronomers have found that 6 percent of all red dwarf stars have an Earth-sized planet in the habitable zone, which is warm enough for liquid water on the planet’s surface. Since red dwarf stars are so common, then statistically the closest Earth-like planet should be only 13 light-years away. Image added Feb. 6, 2013.CREDIT: David A. Aguilar (CfA) |
Billions of Earth-like alien planets likely reside in our Milky Way galaxy, and the nearest such world may be just a stone's throw away in the cosmic scheme of things, a new study reports.
Astronomers have calculated that 6 percent of the galaxy's 75 billion or so red dwarfs — stars smaller and dimmer than the Earth's own sun — probably host habitable, roughly Earth-size planets. That works out to at least 4.5 billion such "alien Earths," the closest of which might be found a mere dozen light-years away, researchers said.
"We thought we would have to search vast distances to find an Earth-like planet," study lead author Courtney Dressing, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement. "Now we realize another Earth is probably in our own backyard, waiting to be spotted."
Dressing and her team analyzed data gathered by NASA's prolific Kepler space telescope, which is staring continuously at more than 150,000 target stars. Kepler spots alien planets by flagging the tiny brightness dips caused when the planets transit, or cross the face of, their stars from the instrument's perspective. [Gallery: A World of Kepler Planets]
Kepler has detected 2,740 exoplanet candidates since its March 2009 launch. Follow-up observations have confirmed only 105 of these possibilities to date, but mission scientists estimate that more than 90 percent will end up being the real deal.
In the new study, Dressing and her colleagues re-analyzed the red dwarfs in Kepler's field of view and found that nearly all are smaller and cooler than previously thought.
This new information bears strongly on the search for Earth-like alien planets, since roughly 75 percent of the galaxy's 100 billion or so stars are red dwarfs.
And the size and location of a star's "habitable zone," the range of distances that could support the existence of liquid water on a planet's surface, are strongly tied to stellar brightness and temperature.
Re-analzying the data
The researchers determined that 95 Kepler exoplanet candidates orbit red dwarfs. Using this information and their newly calculated stellar (and planetary) profiles, the team calculated that about 60 percent of red dwarfs likely host worlds smaller than Neptune.
By analyzing publicly available Kepler data, CfA astronomers identified 95 planetary candidates circling red dwarf stars. Of those, three orbit within the habitable zone (marked in green) — the distance at which they should be warm enough to host liquid water on the surface. Those three planetary candidates (marked with blue dots) are 0.9, 1.4, and 1.7 times the size of Earth. In this graph, light received by the planet increases from left to right, and therefore distance to the star decreases from left to right. Planet size increases from bottom to top. Image released Feb. 6, 2013.CREDIT: C. Dressing (CfA)
Dressing and her colleagues then determined that Kepler has spotted three roughly Earth-size exoplanet candidates in the habitable zones of their parent red dwarfs. One of these worlds is Kepler Object of Interest (KOI) 1422.02. This candidate's newly calculated size is 90 percent that of Earth, and it circles its star every 20 days. If the planet (and these characteristics) are confirmed, KOI 1422.02 may be the first "alien Earth" ever discovered.
The other two candidates are KOI 2626.01, another potential Earth twin that's 1.4 times bigger than Earth and has a 38-day orbit; and KOI 854.01, a world 1.7 times the size of Earth with a 56-day orbit. All three candidates are located between 300 and 600 light-years from Earth and circle stars with surface temperatures between 5,700 and 5,900 degrees Fahrenheit (3,150 and 3,260 degrees Celsius), researchers said. (For comparison, the Earth's sun has a surface temperature of about 10,000 degrees Fahrenheit, or 5,540 degrees Celsius.)
Billions of Earth-like planets
The team further determined that about 6 percent of the Milky Way's red dwarfs should harbor roughly Earth-size planets in their habitable zones, meaning that at least 4.5 billion such worlds may be scattered throughout our galaxy. "We now know the rate of occurrence of habitable planets around the most common stars in our galaxy," co-author David Charbonneau, also of CfA, said in a statement. "That rate implies that it will be significantly easier to search for life beyond the solar system than we previously thought." [9 Exoplanets That Could Host Alien Life] That search may bear fruit right in Earth's backyard, researchers said.
"According to our analysis, the closest Earth-like planet is likely within 13 light-years, which is right next door in terms of astronomical distances," Dressing told SPACE.com via email.
"The knowledge that another an Earth-like planet might be so close is incredibly exciting and bodes well for the next generation of missions designed to detect nearby Earth-like planets," she added. "Once we find nearby Earth-like planets, astronomers are eager to study them in detail with the James Webb Space Telescope and proposed extremely large ground-based telescopes like the Giant Magellan Telescope."
Red dwarfs are also longer-lived than stars like the sun, suggesting that some planets in red dwarf habitable zones may harbor life that's been around a lot longer than that on Earth, which first took root about 3.8 billion years ago. "We might find an Earth that’s 10 billion years old," Charbonneau said.
When it's young, a red dwarf star frequently erupts with strong ultraviolet flares as shown in this artist's conception. Some have argued that life would be impossible on any planet orbiting in the star's habitable zone as a result. However, the planet's atmosphere could protect the surface, and in fact such stresses could help life to evolve. And when the star ages and settles down, its planet would enjoy billions of years of quiet, steady radiance. Image released Feb. 6, 2013.CREDIT: David A. Aguilar (CfA)
The nearest red dwarf is Proxima Centauri, part of the three-star Alpha Centauri system that's just 4.3 light-years or so from Earth. Late last year, astronomers announced the
discovery of an Earth-size planet orbiting the system's Alpha Centauri B, but it's far too hot to host life as we know it. Scientists have also detected five planetary candidates circling the star Tau Ceti, which lies 11.9 light-years away. Two of these potential planets may reside in the habitable zone, but they are at least 4.3 and 6.6 times as massive as Earth, scientists say.
Friday, February 8, 2013
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