Discoveries
Too early for Census results? Not if you're interested in galaxies!
The past six billion years of the universe's 13.8-billion-year history may have been more exciting than people thought.
If an international team of astronomers is correct, galaxy collisions and mergers happened far more frequently during that period than previous research has indicated.
The team, led by Paris Observatory astronomer Francois Hammer, found that 6 billion years ago, the universe contained far more "peculiar" galaxy shapes than appear in more recent times. In effect, the population of these oddballs declined at the same time the proportion of spiral galaxies like the Milky Way increased significantly.
The farther out in space you look, the older the objects are, because light travels at a constant speed. The team based its results on images of 148 galaxies whose distances correspond to the universe as it was about 6 billion years ago. And the group examined images of 116 local galaxies. The images the astronomers used to came from the Sloan Digital Sky Survey and NASA's Great Observatories Origins Deep Survey.
The results: Some 6 billion years ago, peculiar-shaped galaxies held the majority, at some 52 percent of the galaxy types in the sample. Spirals accounted for only 31 percent. Today, spirals make up some 72 percent of the sample, versus 10 percent for the peculiars. The proportion of the population in each sample accounted for by elliptical galaxies and spiral-elliptical hybrids remained virtually constant.
The dramatic drop in the number of peculiar galaxies was a surprise, according to Rodney Delgado-Serrano, a member of the team and the lead author of one of two papers reporting the results in a recent issue of the journal Astronomy and Astrophysics. You can find a plain-English version of the results here.
The results not only suggest that mergers and collisions, which would have led to the cosmic population shift, occurred more frequently more recently than previously thought. It also suggests mergers between peculiars and spirals – if both parties are rich in the gases from which stars form – appear to lead to the formation of large spiral galaxies, rather than ellipticals. In effect the disrupted disk rebuilds itself around its nucleus. That could be one reason why the local universe hosts so many spirals, the team suggests.
Has the Hubble Space Telescope spied asteroid-on-asteroid collision debris?
Astronomers appear to have offered iron-clad proof that two asteroids cannot occupy the same spot simultaneously.
That was never really in doubt, of course. But when you can grab an image of what appears to be fresh collision debris, it makes for an "oh, wow" moment.
Astronomer David Jewitt enlisted the help of the Hubble Space Telescope to observe the apparent collision debris -- a feature first detected in early January by the Lincoln Near-Earth Asteroid Research effort. (The US Air Force foots the bill for LINEAR, which is operated by MIT's Lincoln Laboratory in Lexington, Mass.) If Dr. Jewitt's interpretation holds up, it represents the first time astronomers have seen such a collision, or at least the recent aftermath of a collision.
The aftermath of ancient collisions? You can see it on very dark evenings in a feature called zodiacal light. The sun's rays bounce of space dust that appears along the orbital plane of the solar system's planets and contains tiny fragments from comets and from asteroid collisions. (For classic-rock fans, Queen lead guitarist Brian May finally got his PhD in astrophysics in 2007 on the strength of his studies of zodiacal dust.)
The new feature, dubbed P/2010 A2, looks a lot like a comet's tail, acknowledges Jewitt, a researcher at the University of California at Los Angeles. But it displays striking differences as well.
In effect, it's a headless tail -- it has no relatively uniform halo, or "coma," of dust at the leading end. The remains of the one of the asteroids -- now a kind of nucleus -- appears outside the halo, rather than inside. And spectroscopic studies using ground-based telescopes reveal no gases. Comets, on the other hand, spew copious amounts of gas as they approach the sun and the ices they contain turn from ice to a gas in a flash (do not pass liquid phase, do not collect $200).
Finally, Jewitt points out, the feature is orbiting the sun just inside the inner boundary of the main asteroid belt, between Mars and Jupiter.
Such collisions are very rare events within the life span of an astronomer. But over longer time spans? The two victims of this collision are believed to belong to a family of asteroids, touchingly named the Flora family. Astronomers trace this group's origin to a larger collision some 100 million years ago.
For all the asteroid belts sci-fi movies serve up -- densely packed obstacle courses that white-knuckled rocket jockeys try to negotiate -- our solar system's main asteroid belt is so diaphanous that you have to intentionally aim a spacecraft at one to stand a high chance of hitting it.
A little math with some very crude assumptions -- like a perfectly flat asteroid belt, and an even distribution of asteroids, among others -- helps make the point (bear with me here). By some estimates, there are some 1.7 million objects in the asteroid belt at least 1 kilometer (0.62 miles) across. So let's just go for the big ones.
The highest concentration of asteroids falls within a swath of space ranging from 2.1 and 3.3 astronomical units (AU) from the sun. So that band comprises an area of roughly 20 square AU. One AU, the average distance between the Earth and sun, is about 93,000,000 miles. Take the math all the way to the end, and you get one asteroid in that size class for every 102 billion square miles -- or only one kilometer-plus-sized rock for every imaginary box nearly 320,000 miles on a side.
Lots of room to miss.
Jewelry: so easy a cave man can do it
Move over Tiffanys. It seems even a Neanderthal can make jewelry. The right shells, a little pigment, and, voilà, shell beads.
A team led by University of Bristol archaeologist João Zilhão has uncovered what it interprets as evidence that Neanderthals made rudimentary jewelery from sea shells and pigments – up to now a level of symbolic art associated with early modern humans. Many have held that Neanderthals were too mentally primitive to develop symbolic art before they vanished from the scene.
The team reports that it found several examples, all of which date to about 50,000 ago. The dating is important, the researchers say. Other workers have found what they claimed was evidence of Neanderthal adornment. But those finds were roughly 40,000 years old – dating to a period where Neanderthals and modern humans would have shared the European continent. This has led other researchers to argue that the purported Neanderthal artifacts represented mindless imitation or were from later periods, but they somehow got mixed into the wrong soil layers of the archaeological digs where they were uncovered. These latest artifacts, however, date to a time before modern humans arrived, the team reports.
They team says it found several similarities between the sites where symbolic art – again, body adornments – as appeared among early-modern humans and Neanderthals. In both cases, the sites were near ancient shorelines, where shells would have been abundant. And the sites are at relatively high elevations compared with the shorelines of the day. So whatever poked holes in the shells to be worn, it is highly unlikely that the holes came from wind and wave processes or from the actions of animals.
At one of the two sites the team worked, the artifacts are associated with a time when Neanderthals had all but vanished. So those don't dodge the overlap argument critics ave leveled at other finds. The second batch of artifacts, however, came from deposits dated to 50,000 years ago. "The association of this material with the Neanderthals is, literally, rock solid," the team writes in presenting its results in the upcoming issue of the Proceedings of the National Academy of Science.
In trying to piece together the story of humans' intellectual evolution, the team concludes, their finds add weight to the argument that modern anatomy and modern behavior do not necessarily go hand in hand. The emergence of modern behavior s more likely caused by a combination of technological development, population increases, and increasing social complexity.
Biggest news you've never heard: Earth isn't warming
How do you reconcile the early snow in Minneapolis, ski resorts already opening in Nevada, and that August chill in North Dakota with expert warnings about a warming climate?
You don’t. Why? The Earth isn’t warming right now, is why. It may even be cooling down somewhat.
Five major climate centers around the world agree that average global temperatures have not risen in the past 11 years, according to the BBC. In fact, in eight of those years, global average temperatures dipped a tad.
Yes, there have been several record heat spikes during that time period. The Southern Hemisphere this summer saw the highest land and water temperatures ever recorded, for instance. But overall? Steady as she goes.
Reasons cited range from a slightly cooling Pacific -- a major global heat trap -- as well as renewed questions about the sun’s role in warming (about which there is much debate). Also, it’s possible, some say, that warming itself causes CO2 levels -- which are associated with warming -- instead of the other way around.
As a result, “The depth of the cold of the coming winters will change the social and political climate in ways that only nature can orchestrate,” predicts meteorologist Art Horn.
To be sure, it’s way too early to close one’s ears to those who predict more global warming and sea level rises. The UN's climate agency predicts that from 2010 to 2015 at least half the years will be hotter than the current hottest year on record, which was 1998. And as most of us know, the Earth warmed at historic rates in the latter half of the 20th century, leading to ice cap melts and ecological implications around the globe.
But the warming stall, some experts say, is giving at least some credence to the contrarian (and not always scientifically sound) notion that it may be natural and solar forces contributing as much, or more, than man-made CO2. At the very least, a delay in warming even as total CO2 emissions increase, throws some doubt on the cause-and-effect relationship between mankind’s activities and mean global temperatures.
Climate specialists say their models incorporate all this, and insist their predictions for continued warming will still hold true. (Here’s some data from the Guardian about why the “global warming is taking a break” theme may be off-base.)
Meteorologists at the UK’s Hadley Centre, for instance, point out that global temperatures aren’t linear, and that all data sets -- including solar phenomenon and ocean temperatures -- indicate that warming will soon pick up again.
But as Paul Hudson, the BBC’s environment reporter, points out, Mojib Latif, a member of the UN’s Intergovernmental Panel on Climate Change, agrees that the Earth may, in fact, continue to cool for another 10 to 20 years. Mr. Latif says that doesn’t make him a climate change skeptic, just a scientist. Eventually, he says, “the overwhelming force of man-made global warming reasserts itself,” according to the BBC.
Obviously, climate change has global ecological and political implications. The cap-and-trade bill and new auto emissions rules in the US are direct responses to climate implications of CO2. December’s Copenhagen climate conference will try to seek renewed global commitment to CO2 reduction.
Taken together, what does it all mean?
“Climate change -- no matter how benign or severe a course it takes -- makes legislating during the 21st century one of the most complicated and complex tasks for elected officials in human history,” writes Morgan Josey Glover in the Greensboro, N.C., News-Record newspaper.
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NASA moon bombing successful. Did we find water?
NASA did it. NASA bombed the moon.
Its LCROSS mission punched two new craters in the moon this morning, and only about a minute behind schedule (see video below).
As for whether LCROSS kicked up evidence for water on the moon (the object of the exercise), the jury is still out.
It will take scientists a couple of weeks to figure out if the shadowed area of Cabeus crater holds any water ice. Visually, not much seemed to happen. Michael Bicay, the science director a NASA's Ames Research Center said: "It's hard to tell what we saw here."
But if the science team does find water? How do you get at it, especially if it's covered with moon dust? Just nuke it in a microwave!
That's an approach Ed Ethridge and his colleagues are experimenting with at NASA's Marshall Space Flight Center in Hunstville, Ala. It's a way of turning radio waves into a wringer.
Using simulated moon dirt, they found that under very cold, moon-like temperatures and in a vacuum, a standard household microwave oven would heat the lunar soil, causing ice that had condensed on the soil's grains to change directly from solid directly to gas. By trapping and cooling the gas, they got liquid water.
The approach clearly isn't ready for prime time, Dr. Ethridge cautioned during a phone chat. But it is a proof of principle, he says.
If it works on real lunar soil, it could eliminate the need to dig up icy soil with heavy machinery and run it through energy-hunger water-removal equipment.
Typically, when you cook with a microwave, he says, the microwaves are heating up the water molecules in the food -- cooking from the inside out. But heating ice itself is a different issue. Take that frozen chicken you defrosted as an example. It took several minutes. That's because the oven is operating at less than full power. But it also takes time because ice doesn't respond to microwaves as readily as liquid water does, Ethridge explains.
In the case of lunar soil, the microwaves heated it just enough, even at liquid-nitrogen temperatures, to warm the ice, which then vaporized.
Dr. Etheridge's team extracted 99 percent of the simulated soil's water content.
With data from the experiment well in hand, Ethridge says his group wants to measure the properties of true lunar soil archived at the Johnson Space Center. Then the team can plug that information into their computer models to gage how lunar soil would respond to microwaves.
Lunar-outpost designs call for recycling virtually everything possible, Ethridge notes. But those designs still envision loses -- to the tune of about a ton of water and a ton of oxygen a year.
If microwaving lunar soil proves practical, it could provide a relatively simple way to replenish those losses. And, he adds, "we wouldn't have to strip-mine the moon to do it."
Asteroid 'Apophis' will miss us this time; but 2068? Stay tuned
The asteroid Apophis is very unlikely to smack Earth in 2036. That's the good news from a large group of planetary scientists meeting this week in Puerto Rico (nice gig if you can get it!).
Astronomers discovered the asteroid in 2004. At the time, it looked as if it had a 2.7 percent chance of hitting us in 2029. Additional tracking enabled scientists to refine their calculations of the asteroid's orbit. Those calculations ruled out a smack-down in 2029, but left Apophis with a 1 in 45,000 chance of connecting with Earth in 2036.
New numbers released yesterday, however, now put the odds for an impact in 2036 at 1 in 250,000. As astronomers continue to track the asteroid, they say they expect the odds to shrink further.
At some 0.27 kilometers (about 0.2 miles) across, the object would be capable of widespread destruction on a regional scale, according to calculations made by scientists at the Sandia National Laboratory in Albuquerque, N.M.
"The refined orbital determination further reinforces that Apophis is an asteroid we can look to as an opportunity for exciting science and not something that should be feared," notes Don Yeomans, who heads the Near-Earth Object Program Office at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
What about 2068? Astronomers are now keeping a close eye on the asteroid for any potential 2068 encounter. At the moment, they're giving it one chance in 3 million of nicking the third rock from the sun.
But University of Hawaii astronomer David Tholen says there's an interesting difference in the 2068 encounter.
To understand that difference, journey with me if you will to William Tell's archery range. We have an apple, and in lieu of a youngster's head to mount it on, we'll imagine it sitting somewhere in front of a target with its colorful concentric rings.
The likelihood that an arrow will hit the bulls-eye and split the apple depends on a couple of things: the accuracy of the archer's aim, and where the apple is located in relation to the bulls-eye.
In astronomical terms, the target and its rings represent what researchers call the uncertainty region. It's the circle in space where the asteroid is calculated to pass on a certain date and at a certain time, plus or minus a few target rings. That bit of slop-over exists because scientist may not have enough observations of the asteroid's travels across the sky to be able to shrink the uncertainty region.
If each new batch of observations and calculations put the Earth father and farther outside this region of uncertainty, the asteroid becomes a great night-time show for anyone with a telescope or set of binoculars.
But if additional calculations go the other way, pushing Earth into the uncertainty region, the probability of an unpleasant encounter starts to rise.
Based on what astronomers know now, "Earth is more nearly centered in the 2068 uncertainty region," Dr. Tholen explained in an email exchange. "So if further observations improve the orbit without changing it significantly, then the uncertainty region will shrink with Earth still inside it." If that's true, it could spell bad news for our planet's inhabitants.
When Apophis swings by in 2029, the earth's gravitational pull will significantly change the asteroid's orbit, he continues. "A tiny error in the orbit will get magnified a lot after 2029," he writes. "To know where it will be with reasonable accuracy in 2068, we need to know where it is now to incredibly high accuracy, and that's tough to do with only four years of observations."
For the record, Dr. Tholen and his colleagues made the observations on which Apophis's newest collision probabilities are based. And you can bet he and others will be doing more of the same. The next opportunity for observations comes next year, but only for a week because the asteroid is moving behind the sun. Conditions for observers get a bit easier in 2011, he writes.
In the end, many astronomers expect new observations to further reduce the likelihood of a 2068 encounter.
If you're interested in more information on near-Earth objects, visit the NEO page at NASA's Jet Propulsion Laboratory. You can check out projected close encounters for the next few months here.
Dust storm in Australia turns Sydney into Mars
When dust storms blow through Australia's outback, it's par for the course. When they turn Sydney into a Mars look-alike, it's time to sit up and take note.
A swath of eastern Australia labored Wednesday (Aussie time) under the worst dust storm in more than 70 years. Check out this photo gallery we put together.
Any way you look at it, the event is pretty extraordinary. According to Reuters, the storm carried an estimated 5 million tons of dust from the continent's interior to the east coast. A fair bit of that is priceless farm topsoil, according to the report. At one point, the storm was dumping an estimated 75,000 tons an hour into the Pacific off Sydney.
The country's eastern portion, particularly the farmland watered (at least at one time) by the Murray and Darling Rivers, is in its 12th year of severe drought. And forecasters say that it is likely to continue as El Nino strengthens through the rest of the year.
As for the virtually inevitable global-warming question: Researchers and forecasters are loathe to attribute any single storm to climate change. But the storm does represent one kind of weather phenomenon that is expected to become more frequent as the climate warms.
Once it's kicked up, the dust itself has effects on regional and local climate. The particles reflect sunlight back into space, cooling temperatures underneath it somewhat. Scientists at NASA's Goddard Space Flight Center in Greenbelt, Md., published a study two years ago suggesting that dust-triggered cooling over the North Africa and the eastern Atlantic can affect sea-level air pressure and temperatures thousands of miles away. Others have noted that North African dust storms can retard hurricane formation in the Atlantic because its parasol effect keeps the ocean surface cooler than it might otherwise be.
Northeastern Asia, with dry regions such as the Gobi Desert, represent another big source of atmospheric dust. North Africa sends dust out across the Atlantic, over the Caribbean, and into the eastern Pacific Ocean. In the United States, the single largest source for mineral dust smaller than 10 microns is eastern California's Owens Lake, according to the US Geological Survey. Los Angeles emptied the lake, once criss-crossed by steamboats, during the first half of the 20th century.
Arctic continues to skate on thin ice
The Arctic Ocean's summertime sea-ice melt season is ending, and the ice's expanse fell to the third lowest level since satellites began tracking sea-ice conditions in 1979.
Scientists with the National Snow and Ice Data Center in Boulder, Colo., noted this week that this year's retreat of summer sea ice was not as bad as last year's for two reasons: The summer there was cooler this year than last, especially so in a couple of specific regions; and wind patterns favored a smaller loss of summer ice.
Good news? Signs that global warming is over, if it ever was happening in the first place? Not so fast, scientists say. Yes, 2009 is shaping up to be the second year in a row where summer sea-ice extent has grown compared with the previous year -- following its satellite-record low in 2007. You can find the trends plotted on the second image in the series of images at the top of the page.
But before anyone breaks out the confetti or wags an I-told-you-so finger, the peak extent this summer is still some 24 percent below the 1997-2000 average. And it's 20 percent below the 1979-2008 average.
Moreover the ice that's there consists mostly of relatively thin ice rather than the thick multi-year ice that is less vulnerable to a complete meltdown during the summer. NASA's ICESat satellite has been tracking those trends. You can see the results in the third of the series of images at the top of the page.
Why does the ice matter? From a climate standpoint, all that white reflects sunlight back into space. If ice covers less ocean surface during the summer, the 24/7 sunlight heats more of the ocean. That heat content slows the return of ice in the fall and can continue to thin the remaining ice from underneath.
And while the water is exposed, the oceans warmth can take the chill off well inland (think about the Gulf Stream's moderating effect on temperatures during European winters). Researchers are increasingly concerned that this moderating effect from warmer coastal waters could reinforce the melting of permafrost on land, releasing methane -- molecule for molecule, a far more potent greenhouse gas than carbon dioxide.
Astronomers find 'super Earth' around another star; call it Rocky
Quick! Before you begin reading, drop down to the bottom of the post, activate the YouTube link, then quickly scroll back up here (all you really need is the sound).
Laydeeezzz and gentlemun, boyzzz and girlzzz, an international team of astronomers on the Third Rock from the sun gives you the best evidence yet for a rocky planet -- not too much bigger than Earth -- orbiting another star.
The planet is called CoRoT-7b. And it appears to have a sibling super-Earth, CoRoT-7c, though much less is known about it. This makes the system the first dual super-Earth system astronomers have found. The team summarized its findings today at the European Planetary Science Congress, meeting this week in Postdam, Germany.
You can find a lay-language summary here. You can find a PDF of the formal results, accepted for publication in the journal Astronomy and Astrophysics, here.
CoRoT-7b is the smallest exoplanet found so far. It's slightly more than 1.5 times as large as Earth. But any vague resemblance stops there.
The parent star -- 500 light-years away in the constellation Monoceros -- is some 1.5 billion years old. The planet orbits its star at a distance of less then 2 million miles, giving it a "year" that lasts about 20 hours.
With an orbit that close, the team estimates that the temperatures on the planet's surface range somewhere between 1,527 to 2,327 degrees Celsius on the sunlit portion (think molten on the surface) and a frosty -200 degrees C on the night portion.
The team first announced it had discovered the planet in February. But it took additional measurements from ground-based telescopes to provide enough data for astronomers to estimate the planet's mass and its radius. For now, the best the team can do is give a maximum estimate for the mass -- somewhere around 15 times Earth's mass. CoRoT-7b's radius is slightly more than 1.7 times Earth's radius.
Given those two clues, the team estimates that the planet's density is similar to Earth's. Ergo, it's a rocky planet.
A second team flipped on its computers and with some clever modeling came up with estimates of the planet's composition, as well as their own mass estimate. Based on their calculations, CoRoT-7b is likely to be made largely of iron and silicates, perhaps with a thin atmosphere of vaporized silicate. This team estimates that the planet's mass likely falls between 7 and 15 times Earth's mass. You can find the formal report of their results here. Their work, too, is slated to appear in Astronomy and Astrophysics.
Perhaps as intriguing are the range of possibilities for how the planet formed. It could have originated as a terrestrial-like planet, the team posits. Or it could be the remnant core of what once was a ice or gas giant that migrated too close to the star to retain its gases or ices.
For the record, CoRoT is the acronym for a French planet-hunting, star-studying satellite launched at the end of December 2006. The "7" refers to where this new solar system ranks on the list of systems CoRoT has found. And the "b" refers to the planet itself. Oh yes, there is no "a." If there was, it would be the star itself, but the star is known merely as CoRoT-7.
Jupiter captures a comet, briefly
In July, when an object hurtled into Jupiter's clouds and scarred its cloud tops for all to see, humans had another chance to thank their lucky planet that Jupiter orbits where it does. It can act as a kind of one-planet offensive line, protecting the inner-planet backfield.
Now, a team of Japanese and British astronomers is reporting -- again* -- that Jupiter also can turn these objects into moons, at least or a few years.
The team found that from 1949 to 1961, Jupiter captured comet 147P/Kushisa-Muramatsu, which fell into an irregular orbit around the gas giant. It marked the fifth incident astronomers have uncovered so far where Jupiter has gained, then quickly lost, a potential moon.
The comet in question made two full trips around the planet before it beat cosmic feet and headed out again.
Based on the other four instances where Jupiter has briefly captured an object that completes at least one full Jovian orbit, such events occur on average about once every 10 years, the astronomers calculate.
The results imply that "impacts on Jupiter and temporary satellite-capture events may happen more frequently than we previously expected," according to David Asher, a scientist with the Armagh Observatory in Britain.
What sort of objects be these? A likely source is a group of comets known as quasi-Hilda comets.
Who's Hilda? Actually, an asteroid (yep, not a comet) in the belt of asteroids that orbit the sun between Mars and Jupiter. Discovered in 1875, the object had an unusual orbit for a main-belt asteroid. Similar discoveries followed, leading astronomers to group them into a family known as the Hilda family.
They are main-belt objects that are the closest to Jupiter. They orbit the sun at a pace that carries a unique mathematical relationship to Jupiter's orbital period. (They show a 3:2 orbital resonance with Jupiter, for the astronomically picky.)
The quasi-Hilda comets are a subgroup of comets that never travel farther from the sun than Jupiter. And they have orbital traits relative to Jupiter's that are similar to the Hilda asteroids' traits.
*The results were first reported formally last year in the journal Astronomy and Astrophysics Review. You can find a PDF "preprint" of the article here. The team reprised the results at this week's meeting of the European Planetary Science Congress in Potsdam, Germany.
