Is the Universe a big fat couch potato, expanding by the hour? Maybe the Universe might learn something from Betelgeuse, who’s losing mass and gas thanks to Weightlessness Watchers. A salad might help too!
Listen here [2:30m]:
What’s the facts:
Astronomers have recently estimated the effective diameter of the Universe to be at least 156 billion light-years across, but we also know the Universe is expanding over a time, at a rate measured by Hubble’s constant. It’s even accelerating in its expansion thanks to the repulsive force of Dark Energy. But not everything in the Universe is expanding. Betelgeuse, a bright red star that’s in the shoulder of the constellation Orion, has shrunk by about 15% over the past 15 years. Betelgeuse is still a huge star, almost 1000 times wider than our Sun; indeed, if it was in the place of our Sun it would engulf the planets Mercury, Venus, Earth, and Mars. Astronomers classify Betelgeuse as a red supergiant, 135,000 times brighter and 20 times more massive than the Sun.
DARK MATTER helped bring the bullet cluster together!
Are you a flabby galaxy, tired of being pushed around by the bigger galaxies in your local group? Need to bulk up in a hurry so you can be gravitationally attractive? Then you need DARK MATTER! Listen to our infomerical to find out how dark matter has helped galaxies like the Milky Way and M33, and what it can do for you.
Listen here [6:12m]:
What’s the facts:
Dark matter is a mysterious substance that we cannot see, touch, smell, hear, or taste (although it might not taste so bad). Yet there is about 6 times more of it in the Universe than normal matter, stuff like protons, electons, and neutrons that the stars, planets, and people are made of. If we can’t see it, how do we know dark matter is out there? Well, dark matter still has a gravitational force associated with it, and it is that “extra attraction” that reveals its existence. The motion of galaxies in clusters and the orbits of stars around the centers of galaxies (including our own) both reveal the presence of dark matter. Perhaps more spectacularly, a large amout of dark matter – say, associated with a whole cluster of galaxies – acts as a gravitational lens, focusing and warping light from galaxies behind the cluster like a fun house mirror (for an interesting example, see this picture of Abell 2218). Despite not being able to see dark matter, scientists know quite a bit about its properties – that its probably not just “dim” normal matter (like neutrinos or brown dwarfs); that it is mostly “cold” (not moving close to the speed of light); that it interacts very weakly with regular matter (as illustrated with the Bullet Cluster collision); and that it is distributed over large length scales like the size of a galaxy, as opposed to the size of a planet (sorry, no pulling dark matter tricks on your little brother at home). Because it is makes up so much of the known Universe, there are many experiments now underway to try to detect dark matter through their infrequent collisions with other regular matter particles. Hopefully, within the next few years we may have our first detection of the stuff that makes up most of the mass in the Universe!
Happy birthday Universe! Unfortunately, its hard to see the cake beneath all 13.7 billion candles… [0:24m]
What’s the facts?
Yes, we actually know the age of our Universe! But how do we know? One helpful clue is that our Universe is expanding. We see this from the fact that distant galaxies in all directions are moving away from us, and the most distant galaxies are moving the fastest. Trace back all that motion to one point in space and time – the Big Bang – and you can figure out how long the Universe has been around. However, this type of age estimate makes an assumption as to how the Universe formed and how the expansion rate has changed over time – in astronomer-speak, it’s a “model-dependent” age. But other direct age estimates, such as the radioactive decay of heavy elements and the ages of the oldest stars and star clusters, give similar numbers. Astronomers now estimate that the Universe is 13,700,000,000 years old – now that’s a birthday cake!