Kepler-68d

Transcription

Space Fans and welcome to the first Space Fan News of 2012. First up, the SETI astronomers have started pointing their telescopes at the Kepler planet candidates that you may remember were announced in 2011. It is generally thought, that in our search for extra terrestrial intelligence, it makes sense to look for those signs from planets that are more like the Earth. This doesn't mean that life can't form in strange planets with harsh environments, but when starting out, we should look in places where we know live can evolve into a civilization - places like the Earth. While the Kepler team has not confirmed all of these candidates - also called Kepler Objects of Interest - as being Earth sized planets within a habitable zone, the SETI team started looking anyway. Specifically, they are looking in a region of the radio spectrum called the Terrestrial Microwave Window. These are the radio frequencies that can penetrate the noise of both interstellar space and our own atmosphere. They are looking in a special narrow range of frequencies within this window known as the “Water Hole,” which if you watched the movie 'Contact' you will find it significant that these frequencies are around 21 cm where spectral lines that are associated with the disassociation of water are located. The argument goes like this: since water is presumed to be necessary for life to exist, an alien civilization might choose to broadcast their existence at this wavelength in an attempt to find others. That assumes, of course, that they are looking in the first place and want to be found. I know, it's a long shot, but hey, based on what we know about life in the universe so far, which is nothing, it's worth a try! Anyway, after spending some months sifting through data, they are publishing some of the results. They are not reporting any alien signals, but they are finding some interesting characteristics of some of the signals. These are the results from KOI 817 and 812. What's interesting about them, according to the SETI team, is that these signals, while nothing more than interference they are careful to say, look similar to what we can expect to see from a broadcasting civilization. For example, The signals have a narrow frequency as you can see from the very thin line, much thinner than atmospheric noise, and they are drifting in frequency over time, which make them look like diagnonal lines in these plots. This is the signal shifting towards longer or shorter wavelengths due to the doppler effect of the motions between us and the Kepler planets. If you look carefully you can see that the frequency starts in one location, then as time passes, ends up at another frequency. Which way this diagonal line points depends on the actual motion of the planet at the time these were recorded: if the planet is moving towards us, the line drifts toward shorter wavelengths, going away, towards longer wavelengths. So, while these signals are nothing but interference, probably from us, these results are promising because they are a confirmation that the algorithms they are using to find these telltale signs of life appear to be working as they continue their analysis on other Kepler Objects of Interest. Next, astronomers have discovered that there were supermassive black holes in the universe much earlier than expected, as early as 700 million years after the Big Bang. What's surprising about this is that supermassive black holes become supermassive only after lots and lots of galaxy collisions, with the black hole getting bigger after each collision as the previously two black holes merge into one. When the universe was a few hundred million years old, the first stars and galaxies were just forming. Everything was just starting out: stars, galaxies, even black holes. It has always been thought that most black holes from this period in the universe's history would be small because they wouldn't have had a chance to gobble up enough material to become supermassive. Well, it turns out that is not the case. Using observations from the Sloan Digital Sky Survey, astronomers found supermassive black holes at a time when the universe was less than 1 billion years old. They were the same size as today's most massive black holes, which have had 13.6 billion years to form. So this was strange. How could there be such big black holes from so early when it takes the whole age of the universe for others to reach the same mass? So this discovery was very surprising. For those who don't know, there are two main classes of black holes: stellar-sized ones that are around 30 times larger than the Sun and are roaming around inside our galaxy. The second type is way more massive. These are usually found in the centers of galaxies and are billions of times larger than the mass of the Sun. These supermassive black holes are the largest in the universe and are believed to form from the collisions of galaxies when their central black holes combine into a larger one. As more collision occur, the black hole gets larger and larger. The problem though, is that in the first few millions of years after the Big Bang, galaxies were too few and too far apart to merge. So to find out how these black holes could form so early, astronomers ran a massive simulation to try to understand the observations from Sloan. This simulation was so sophisticated that it allowed them to zoom in on interesting events occurring while the simulation ran. As they zoomed in to the creation of the first supermassive black holes in their simulation, they saw something unexpected. Normally, in supermassive black holes we see today, when cold gas flows toward a black hole it collides with other gas in the surrounding galaxy. This causes the cold gas to heat up and then cool back down before it enters the black hole. This process, called shock heating, would stop black holes in the early universe from growing fast enough to reach the masses found in these observations. Instead, no shock heating was occuring in the early black holes. They saw in their simulation thin streams of cold dense gas flowing along the filaments that give structure to the universe and straight into the center of the black holes at very high speed, feeding them at a fast rate, with no shock heating. This uncontrolled consumption caused the black holes to grow exponentially faster than the galaxies in which they reside. So that's one possible explanation as to how there could be such large black holes so early in the universe. One more cool thing came out of this: since a galaxy forms when a black hole forms, these results could also shed light on how the first galaxies formed, giving us even more clues as to how the universe came to be. That's it for this week Space Fans, don't forget next week is the AAS where I will post a video a day from Monday to Thursday to talk about the amazing discoveries and science that's sure to come out of the meeting. I can't believe we've been doing this for an entire year! Well, thanks for watching and, as always, keep looking up!