Podcaster: Morgan Rehnberg
Title: Monthly News Roundup – To Mars We Go
Link : http://cosmicchatter.org
Gamma-ray burst: http://www.skyandtelescope.com/news/Monster-Gamma-Ray-Burst-Challenges-Theories-232889371.html
6-tailed asteroid: http://www.nasa.gov/press/2013/november/nasas-hubble-sees-asteroid-spouting-six-comet-like-tails/#.UpVdM1RDvqV
Black hole jets: http://astronomy.com/news/2013/11/black-hole-jets-pack-a-powerful-punch
Asteroid danger: http://www.space.com/23487-asteroid-threat-earth-russian-meteor-explosion.html
Cosmic Chatter: http://cosmicchatter.org
Description: In this episode of the Monthly News Roundup, we send a pair of spacecraft towards Mars. A strange asteroid is discovered and another hints at the dangers of space. Astronomers digest the largest gamma-ray burst ever observed and finally shed light on what’s in a black hole jet.
Bio: Morgan Rehnberg is a graduate student in astrophysics and planetary science at the University of Colorado – Boulder. When not studying the rings of Saturn, he develops software to help search for asteroids that might hit the Earth. He blogs and podcasts about astronomy and space science at http://cosmicchatter.org.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by — no one. We still need sponsors for many days in 2013, so please consider sponsoring a day or two. Just click on the “Donate” button on the lower left side of this webpage, or contact us at firstname.lastname@example.org.
You’re listening to the 365 Days of Astronomy podcast for November 30, 2013. I’m Morgan Rehnberg, here with Vivienne Baldassare, and this is the Monthly News Roundup. This episode was produced by Cosmic Chatter in Boulder, Colorado.
November was a banner month for Mars missions. Two nations launched probes which will join our growing fleet of Mars-observing spacecraft.
On November 5th, India launched their first ever Martian spacecraft, the Mars Orbiter Mission and minutes later it successfully reached Earth orbit. After a few weeks of system tests and other preparation, the probe will fire its rocket and head to Mars. Once in Martian orbit, the mission will study the surface and atmosphere of Mars with a suite of onboard instruments. Just as importantly for India, however, a successful mission will establish the country as a leading space power among developing nations. No space program has ever conducted a successful Mars mission on its first try, so this would be a real feather in India’s cap.
Less than two weeks later, it was NASA’s turn. The MAVEN mission blasted off aboard an Atlas V rocket on November 18 and began its ten-month journey to the red planet. Once it arrives, the probe is designed to study the Martian atmosphere. Scientists hope to answer questions about the origin, evolution, and loss of Mars’ atmosphere over the last few billion years. Combined with observations of the lower atmosphere from Curiosity and Opportunity, MAVEN astronomers will build the first global picture of the Martian atmosphere.
It’s not just coincidence that two missions to Mars launched in the same month. Both the Earth and Mars are orbiting the Sun, but at different rates. This means that sometimes the planets are close together, while other times they are much farther apart. It turns out certain configurations, which happen about every two years, lead to much more fuel-efficient missions. The advantages of launching in these windows are so great that mission just do not happen at other times. That means we won’t be seeing another trip to Mars until 2016 or 2018 – plenty of time for both MAVEN and the Mars Orbiter Mission to do their work!
Astronomers recently observed an extraordinarily bright gamma ray burst coming from a supernova, or the death of a massive star, in a far away galaxy. Gamma ray bursts, or large flashes of high energy light, are the brightest observed events in the universe. About once a day, light from a gamma ray burst reaches the Earth; these bursts typically last just a few seconds. Gamma ray burst 130427A lasted for 20 seconds, and stray light from the burst continued to come in for another 20 hours. Additionally, astronomers observed the two highest energy photons to ever be seen coming from a gamma ray burst. These photons were millions of times more energetic than those used by doctors to take x-ray images.
The burst was first seen by the Fermi Gamma-Ray Space Telescope. Very few gamma rays make it through the Earth’s atmosphere, so they must be observed from space. Fermi has two instruments, the Large Area Telescope, which observes one fifth of the sky at a time to search for high energy gamma rays, and the GLAST Burst Monitor, which monitors all of the sky not blocked by Earth. When a burst is detected, by either instrument, Fermi can move quickly to point itself directly at the source.
When Fermi detected burst 130427A, alerts were sent out to other telescopes. Swift, another space observatory, was observing the burst within four minutes. In all, 58 different telescopes, both in space and on Earth, observed this burst.
The high energy photons detected in this gamma ray burst have created a puzzle for astronomers. Our current models of how gamma ray bursts are generated inside dying stars cannot explain the formation of such high energy photons. Alternative explanations have been proposed, but none are testable yet. It may be some time before we fully understand gamma ray burst 130427A.
Astronomers announced this month the discovery of a rather unusual object – an asteroid with tails like a comet! Although the object was first observed by the PAN STARRS telescope back in August, it took researchers a while to figure out what they were looking at. With the help of the Hubble Space Telescope, they identified six distinct tails billowing off the surface. It’s actually common for comets to have two tails, but six was quite the surprise.
What’s causing these tails? It’s probably not what you imagine. These tails are actually not ice, but instead dust. This means that, unlike a comet, the material isn’t simply evaporating off into space. It’s also unlikely that the tails were formed by a collision with another asteroid, because that would throw up a big cloud, not a few tails. The most likely culprit is actually light. Although it weighs nothing, light actually does carry a tiny bit of energy. It’s such a small amount that all the light hitting your body combined is still completely unnoticeable, but, over time and in the absence of other forces, these collisions can add up. The net result is that an asteroid can start spinning simply because the Sun’s light is shining on it.
Many asteroids are not solid rocks. Instead, they are better described as rubble piles, or bunches of material held together only by their own gravity. Gravity is pretty weak in small amounts, so it doesn’t take a lot of spinning because the centrifugal force overpowers it. When this happens, material from the surface just floats away. The six tails observed for this asteroid likely represent the six places where gravity was the weakest.
Since many asteroids are rubble piles, this multi-tailed phenomenon is probably more common than we might think. But because the dust floats away after a few months, we just haven’t been lucky enough to catch the process in action until now.
Ever seen a picture of a black hole with big jets shooting out and wonder what was in them? So did scientists – until this month, when they found jets from one such system to be containing iron and nickel, two very heavy elements. The black hole responsible for these particular jets is a small one – just a few times the mass of our Sun – and it is swallowing up material from a star next to it. Scientists have observed one other black hole jet system containing heavy elements, but that system was unusual. This discovery is special in that these heavy elements were observed in jets coming from a black hole that is considered to be representative of black holes in general, so astronomers think that other black hole jets should contain these elements as well. These results should even apply to the supermassive black holes that reside in the centers of most galaxies, indicating that jets could help spread heavy elements throughout a galaxy.
The mechanism that generates these jets continues to elude astronomers. Jets could either be powered by the spinning of the black hole itself, or by the spinning of the black hole’s accretion disk, a disk of material that swirls around the black hole before it falls in. Finding heavy elements in the jet points towards the rotation of the accretion disk powering the jet, since astronomers expect that if the spin of the black hole was powering the jet, they would detect only light particles inside it.
Let’s end this month with a look at how safe we are from outer space. Perhaps you remember the meteor which exploded over the Russian city of Chelyabinsk back in February. I sure do – it’s not every day that one sees a giant explosion in the sky. But it seems as such events might be more frequent than we previously expected.
NASA astronomer Peter Jenniskens released his analysis of the Chelyabinsk meteor earlier this month in which he concluded the breakup of the asteroid released energy equal to approximately five hundred thousand tons of TNT. This amount of energy, equivalent to a medium-sized modern nuclear weapon, damaged thousands of homes and sent more than one thousand people to the hospital. Jenniskens estimated that an event as large or larger than Chelyabinsk should only have about a one in ten chance of occurring in any given twenty-year period. But in the last one hundred years, three such events have occurred and Chelyabinsk is, in fact, the smallest of them.
This suggests that impacts of this size could be as much as ten times as frequent as we previously expected. What can we do about this threat? Probably not a lot right now. Asteroids which can cause impacts of this variety are not particularly large in the grand scheme of things and we often do not discover them until mere days before impact. Some, like the one which struck Chelyabinsk, are never seen at all. Fortunately for us, two-thirds of the Earth is covered by water and much of the land is not inhabited by humans. The Earth’s atmosphere also acts like a protective shield, absorbing much of the incoming object’s energy.
Thanks for listening to this episode of the Monthly News Roundup. For more astronomy news and commentary, visit http://cosmicchatter.org or follow @cosmic_chatter on Twitter. As always, you can contact us with your comments and corrections at email@example.com. This episode also contained information about MAVEN, a spacecraft operated by my employer, the Laboratory for Atmospheric and Space Physics at the University of Colorado. See you in December!
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