Wednesday, July 27, 2011

Earth's First Asteroid Companion Discovered

This is an amazing discovery. Up until now, companion asteroids that more or less share an orbit with Earth have been theoretical. This class of asteroids is known as Trojans; Jupiter has them, and so do Mars and Neptune. Now Earth joins the club with 2010 TK7, an asteroid approximately 300 meters (1000 feet) across and 80 million km (50 million miles) from Earth.
Asteroid 2010 TK7 is circled in green, in this single frame taken by NASA's Wide-field Infrared Survey Explorer, or WISE. Image credit: NASA/JPL-Caltech/UCLA

NASA’s Wide-field Infrared Survey Explorer (WISE) managed to notice the small asteroid. WISE sees in the infrared, where warmer objects are easier to spot. 2010 TK7 is probably about the freezing point of water, which is pretty warm to astronomers. It also orbits such that it is mostly in the sky during daylight hours from Earth, so your typical amateur astronomer isn't going to be able to go out and spot this.

WISE was an asteroid hunting satellite that stopped operating back in February. Astronomers discovered 2010 TK7 by looking through the vast amount of data collected by WISE and confirmed it with Earth-based telescopes. This gives hope that other Earth Trojans might be buried in the data waiting to be found. Where there is one, there may be many.

What makes a Trojan, a companion asteroid, special, is that they orbit what is called a Lagrangian point. Five special spots between two astronomical bodies where gravity is essentially neutral. The points remain stable relative to where the one body is along its orbit around the other. The graph above maps out the locations of where these points would be.

2010 TK7 orbits Earth's L4 point, rather than remaining stable at the point or orbiting the Earth itself. It also has a kind of funky orbit that takes it closer and further away from the Earth, but it is still roughly 60 degrees in front of us and of no danger to the Earth. It just won't ever get close enough.
This artist's concept (not to scale) illustrates the first known Earth Trojan asteroid, discovered by WISE. The asteroid is gray and its extreme orbit is shown in green. Image credit: Paul Wiegert, University of Western Ontario, Canada

It is a tantalizing discovery because it opens the door to several new questions. We know little about this asteroid. It may be a candidate for future exploration, but because of it's odd orbit (it goes well above and below the orbital plane), it would be difficult to reach. But you can bet astronomers are going race to find more Earth Trojans. They have been looking for them for some time already, so it was only a matter of time.

And being an object of some importance, it will also need to be named. Coeus or Crius, the Titan sons of Gaia have been mentioned, but there are other sons of hers. Personally I wouldn't my the cyclopes sons of Gaia; Brontes ("thunderer"), Steropes ("lightning") and the "bright" Arges. But I guess we'll have to see.

Monday, July 25, 2011

The Largest, Most Distant Water Reservoir Found

This artist's concept illustrates a quasar, or feeding black hole, similar to APM 08279+5255, where astronomers discovered huge amounts of water vapor. Image credit: NASA/ESA 
More than 12 billion light years away sits a massive body of water surrounding a large, feeding black hole. The amount of water is equivalent to 140 trillion times all the water on Earth. It also shows an early abundance of water in the Universe, being 12 billion light years away means that the light from this event is 12 billion years old. Early for a 13.75 billion year old Universe.

Black holes that are active like this one are known as quasars. Known as APM 08279+5255, the black hole at the center is some 20 billion times more massive than our Sun. It also produces the energy of a thousand trillion suns, and early powerhouse in the Universe.

The water exists in the form of water vapor, a gas, around the black hole and its distribution can reveal details about the nature of the quasar. They can determine how the radiation from the quasar is heating the surrounding gas, which, by astronomical standards, is unusually warm and dense. At several hundred light years across, it is one order of magnitude or two denser and about 5 times hotter than water vapor found in a typical galaxy. It is still far from the comfort of Earth's atmosphere though, at a freezing -63 degrees Fahrenheit (-53 Celsius) and 300 trillion times less dense than the Earth's atmosphere.

[How can water that cold be a gas? That is entirely because of the density, since the particles of water are so far spread apart, they do not condense as the would into a solid under higher pressures (like the Earth's atmosphere).]

There is enough gas in this cloud for the black hole to grow about six times its current size. However, it is unclear if it would reach that far, some gas may be ejected from the quasar or form into stars.

The research is partially funded by NASA and the astronomer teams will be having their paper published in the Astrophysical Journal Letters later this year. You can read a little bit more about it in the NASA release.