Universe Update February 2013
By Ryan Wyatt
The third Thursday of every month, Morrison Planetarium hosts “Universe Update” at the 6:30 planetarium shows during NightLife. I select my favorite astronomy stories from the past month, and I give a brief run-down of current discoveries while taking audiences on a guided tour of the Universe. The planetarium sports a tricked-out three-dimensional atlas of the Universe, so I can take you places virtually while talking about the latest astronomy news.
At any rate, I always start at Earth and work my way out to cosmological distances, so I’ll list the news stories in the same order—from closest to farthest from home.
You certainly can’t get much closer to home than the meteorite that sped through the sky above Chelyabinsk, Russia, in the early morning hours of 15 February. Upon entering Earth’s atmosphere, it caused a shockwave that ended up injuring more than 1,000 locals. A helpful NASA page gives the estimated size of the object (before it entered our atmosphere, that is) as 55 feet (17 meters) and its estimated mass around 10,000 tons. It released approximately 500 kilotons of energy as it slammed into our atmosphere—nearly 40 times the explosive power of the bomb dropped on Hiroshima! “We would expect an event of this magnitude to occur once every 100 years on average,” said Paul Chodas of NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory.
The videos of the event give a real sense of the, um, impact. The New York Times collected some of the best videos on a single page, which offers a range of reactions from tedium to terror. (Evidently, drivers in Russia frequently mount video cameras on their dashboard to capture imagery that can help out in the aftermath of an accident or altercation, providing visual evidence for courts and insurance companies. As an added bonus, watching the YouTube videos you also get a sense of what Russians listen to on the radio…) The Times also presented a nice summary of the details of the event.
Weirdly, the arrival of the Russian meteor coincided with the flyby of Asteroid 2012 DA14, a small near-Earth object about 150 feet (45 meters) in diameter. As its name suggests, the asteroid was discovered last year, and careful calculation of its trajectory allowed us to predict its passage relatively close to home. It ended up passing a mere 17,200 miles (27,700 kilometers) above Earth’s surface, which amounts to about two Earth diameters’ distance. Fairly close in astronomical terms.
And the two objects showing up at approximately the same time? Purely coincidental, really! According to the same NASA web page above:
The trajectory of the Russian meteor was significantly different than the trajectory of the asteroid 2012 DA14, which hours later made its flyby of Earth, making it a completely unrelated object. The Russia meteor is the largest reported since 1908, when a meteor hit Tunguska, Siberia.
And yeah, it’s the whole hitting thing that makes us nervous, of course. Our friends at the B612 Foundation have invested a lot of energy into figuring out how to destroy an Earth-bound asteroid, and recently, the foundation has also proposed launching a privately-funded space-based telescope to detect literally hundreds of thousands of asteroids (check out the TEDx talk by B612’s CEO Ed Lu for more details). A team at the University of Hawaii used the meteorite-and-asteroid coincidence to issue a press release about the Asteroid Terrestrial-impact Last Alert System (ATLAS), a distressingly-named “asteroid detection system that will patrol the visible sky twice a night looking for faint objects moving through space.” And scientists at UC Santa Barbara went one better, proposing a space-based system that would vaporize any potential asteroid threats from afar…
In less terrifying news, a recent NASA press release describes the kind of advance that speaks to the challenges of modern science: the publication of a set of equations that help describe the behavior of the solar wind. This doesn’t normally capture people’s attention (indeed, the press release came out a full two and a half months after the publication of the research), but it represents the kind of important, incremental work that eventually changes our understanding of the Universe. So, you go, Aaron Roberts! Great work!
The Apollo missions may have ended more than forty years ago, but the samples the astronauts brought home continue to teach us about our nearest neighbor in space. A University of Michigan researcher and his colleagues just announced the results of their analysis of the “Genesis Rock,” a lunar sample collected during the Apollo 15 mission. Believed to be a piece of the moon’s primordial crust, “crystallized from a magma ocean on a mostly molten early moon,” this unassuming rock should show basically no signs of water… And yet, the researchers detected good ol’ H2O! Not exactly devastating news, but a surprise. Scientists are still sorting out the story of how the Moon formed, and water in its primordial crust provides an additional constraint on the theories.
Moving on to Mars, NASA’s Curiosity mission can usually steal the show (this month, we have the spiffy image of “the first sample ever collected from the interior of a rock on another planet”), but I noticed a more mundane take on the Mars topic… Two researchers from Brown University studied “the world’s saltiest pond,” Antarctica’s Don Juan Pond, and they announced new ideas on how the water stays saline, with implications for similar environments on Mars:
Using time lapse photography and other data, the researchers show that water sucked out of the atmosphere by parched, salty soil is the source of the saltwater brine that keeps the pond from freezing. Combine that with some fresh water flowing in from melting snow, and you’ve got a pond able to remain fluid in one of the coldest and driest places on Earth. And because of the similarities between the Dry Valleys and the frozen desert of Mars, the findings could have important implications for water flow on the Red Planet both in the past and maybe in the present.
Enough with the Solar System! Time to look farther afield for new discoveries…
I delight in the way astronomers push the boundaries of imaging techniques, allowing us to see what’s going on quadrillions of miles away. This month, an international team of astronomers released an infrared image of a disk surrounding a star 470 light years away, revealing enough interior structure to deduce “the probable existence of unseen planets.” Amazing.
Planets form out of dusty disks, y’see, and these disks are a tell-tale sign of possible planet formation. So when the European Space Agency announced observations of star past its prime that nonetheless seems to have a massive disk of material surrounding it, it raised a few eyebrows. “We didn’t expect to see so much gas around this star,” said Edwin Bergin of the University of Michigan. “Typically stars of this age have cleared out their surrounding material, but this star still has enough mass to make the equivalent of 50 Jupiters.” Well, that doesn’t sound too scandalous, but another important thing to note is that this accurate accounting of the mass in a disk represents a leap forward in figuring out how much gas exists in these systems, and the gas plays a critical role in planet formation.
So what happens once those planets form? Well, we would like to think that some of them go on to develop the infestation known as life, and in typically selfish thinking, we then start to wonder if any extraterrestrial life might want to talk to us. (Okay, I skipped a lot of steps, but still…) Thus, the Search for Extraterrestrial Intelligence (SETI): we start looking for signals from other worlds. Since the Kepler mission excels at planet-finding these days, scientists at UC Berkeley decided to take a look around 86 of the stars around which Kepler detects evidence for a planet or planets. Having discovered no signals, the team made a statistical argument to suggest “that fewer than one in a million stars in the Milky Way Galaxy have planetary civilizations advanced enough to transmit beacons we could detect.” That doesn’t sound too promising, but when you realize that our galaxy probably contains a few hundred billion stars, the odds start to look a little better… That still means a few hundred thousand civilizations could be waiting to talk to us! (Of course, the one-in-a-million statistic probably represents an upper limit: the odds are probably much worse.)
I rarely make it through an entire Universe Update without mentioning the Hubble Space Telescope, and this month is no exception. A press release describes that precise measurements reveal “the sideways motions of a small sample of stars located far from the galaxy’s center,” which in turn suggests that the stars once inhabited a galaxy gobbled up by the Milky Way. We know that galaxies collide relatively frequently in the scheme of things (creating some great astronomy photo ops, as Wired noted several months ago), and indeed, galaxy collisions may be responsible for the formation of spiral structure and other familiar aspects of galaxies. This handful of stars represents further evidence of how collisions shaped our own home galaxy.
Astronomers have long suspected that galaxy collisions could contribute to another spectacular phenomenon—the supermassive black holes that reside at the centers of practically all large galaxies. A recent announcement from the University of Central Lancashire (of all places) suggests that such black holes grow faster than expected:
Until recently astronomers had thought that black holes grow mostly when galaxies crash into each other, at which time a large concentration of gas forms around the black hole and gets very hot, shining very brightly in what is known as an active galactic nucleus.
Instead, it seems that these supermassive black holes gain mass just fine all by their lonesome. As the press release notes, “Even the black hole in our own Milky Way Galaxy, which otherwise appears very quiet, has probably been consuming the equivalent of one Sun every 3,000 years.” Doesn’t quite sound like the Jenny Craig plan, but that’s about an octillion pounds a year!
That’s all for this month. Join us in March for more Universe Update.