November 12, 2010 Leave a comment
Admittedly, this post’s title comes from my favorite part of Pixar’s Finding Nemo, when the crazed fish in the dentist’s office fish tank flings himself onto the tiny treasure chest emitting air bubbles in an attempt to stop Nemo from touching “his bubbles”. Title aside, today’s post is about something pretty darn cool. NASA scientists have found giant “bubbles” (pictured below) of high-energy light called gamma rays that stretch almost 25,000 lightyears away from the center of our galaxy. Just to give you an idea of the size of these bubbles, the full diameter of the disc of our galaxy is roughly 100,000 lightyears, so these gamma ray bubbles are not small features in galactic size scales. To make the point even more explicit, 25,000 lightyears means that it takes light, the fastest thing in the universe at 670,616,629 mph, 25,000 years to travel from one end of the bubble to the other. The fastest spacecraft ever launched from Earth, New Horizons back in 2006, traveled at only 35,800 mph, meaning it would take almost 2 BILLION YEARS to travel across one of these bubbles. The bottom line is they’re huge.
The most interesting thing about these huge gamma ray bubbles though is that no one expected to see them. This week NASA released info that it’s Fermi Gamma Ray Space Telescope had successfully imaged these huge never-before-seen galactic structures. They are actually so large that if our eyes could see gamma ray light, they would take up half of the observable sky. So how did we miss such something so big? Well, to be frank we didn’t really know to look for them. Gamma Ray Bursts (GRBs) or large explosions of high-energy light have been a puzzle to scientists since their discovery nearly half a century ago. They are believed to be a result of ancient supernovae, the explosive high-energy death of supermassive stars that formed at the very early stages of the universe, but as far as we know, none of these types of supernovae do or can exist in our own galaxy, the Milky Way. Which is really good for us, because if any of these happened anywhere near our Solar System, the massive influx of energy could be disastrous for life on Earth. A sudden precipitation of photoelectric (light) energy could have really unexpected and unwanted consequences for Earth’s atmosphere.
The leading theories behind these bubbles is that they are resultant from a particle jets from the supermassive black hole at the center of the Milky Way. We have seen particle jets similar to these in other galaxies; they are created as matter in near the center of the galaxy falls toward a black hole at the heart of the galaxy. There’s no evidence that black hole we believe to be at the heart of the Milky Way (commonly referred to as Sagittarius A*) has such a jet currently, it may have in the past. If that’s true, then the bubbles we see might be leftover light that is just now reaching the Earth although the actual jets may have died out thousands of years ago. *This is one of the really cool things that you need to keep in mind when you think about astronomy. It takes a finite amount of time for light to travel large distances in the Universe, so many of the objects that we look at may not even exist anymore. The Andromeda Galaxy, our closest galactic neighbor for example, is approximately 2.5 million light years away from us. That means that we actually have no idea how the galaxy looks currently in 2010, that light won’t get to Earth for another 2.5 million years. So in essence when we look at very distant astronomical objects, we’re also looking back in time.* Another possibility is that the bubbles may have formed as a result of gas outflows from a rapid burst of star formation, perhaps the one that produced many massive star clusters near the Milky Way’s center several million years ago.
In any case this very cool and unexpected discovery just shows us how little we actually know about the universe (about our own home galaxy even) and how much cool stuff is still out there to be learned!