NASA scientists confirm the explosive origin of the immense empty bubble in space that surrounds Earth's solar system
Thursday, August 28, 2014, 12:17 PM - A supernova is one of the most spectacular explosions in the universe, and consequently one of the most dangerous. In our galaxy alone, one or two go off every century, and while Earth is in no danger from any that may go off in the future, scientists have discovered that, millions of years ago, a cluster of them went off reasonably close, blowing a huge bubble in the interstellar gases that surround our solar system.
This new video, produced by NASA ScienceCasts, discusses the science behind the this find, how the researchers went about discounting other possible explanations for observatories were seeing in the galactic medium around our solar system, and the implications of the discovery:
With the gases in this interstellar bubble having temperatures measured at around a million degrees (according to the video), it might seem like our solar system would be cooked and life here would be impossible. However, as the video says, the gases inside the bubble are not only hot, but they're extremely diffuse - with only one atom for every cubic decimeter of space. By comparison, the same volume of air of Earth's atmosphere, at 15 Celcius and sea level pressure, has roughly 25 sextillion (25,000,000,000,000,000,000,000) molecules.
Heat that sample of Earth's atmosphere to a million degrees and it would glow like the Sun. In fact, the Sun's corona is just about that temperature. However, when a gas is very diffuse, it can be extremely hot and you wouldn't feel it, because it takes interaction between atoms and molecules to transfer heat. If you stuck your hand in a cube that was 10 centimetres on a side, with only one (extremely hot) atom bouncing around in side it, you wouldn't feel any difference in temperature at all. Not only wouldn't there be enough interactions between that one atom and your hand to transfer enough heat for you to feel it, but without any other molecules or atoms of gas in the box, your hand wouldn't radiate any of its heat away. The only way that you would know the temperature of the atom is by measuring the radiation coming off of it, which at one million degrees would be in extreme ultraviolet range (approaching x-ray energies).
The study conducted by the researchers, which led to this discovery, was published in the journal Nature (click here).