I am very pleased to write that the Nobel Prize for physics this year has been awarded to three astronomers for their discovery of dark energy — a still-mysterious phenomenon that is causing the expansion of the Universe to accelerate.
Saul Perlmutter, Brian Schmidt, and Adam Riess are sharing the award. Back in 1998, Saul and Brian headed up two rival teams trying to observe very distant exploding stars, hoping they would yield better numbers for how fast the Universe expanded. Adam was on Brian’s team, and led the work on finding a way to try to understand the behavior of the supernovae. To everyone’s surprise, the data indicated the Universe was not just expanding, but expanding faster every day — it was accelerating.
Something must be pushing on the very fabric of space itself, causing it to expand ever-faster. We don’t now what it is, exactly, but we call it dark energy, and over the past 12 years, more and more observations have piled up showing that this stuff really is out there.
If you want background info on all this, see the Related Posts section below; there are plenty of links to articles I’ve written on this topic. The folks at Hubble also created a video describing dark energy and what it means for the Universe.
This is very exciting for lots of reasons. First, of course, it’s nice to see an astronomical topic win what is considered the top prize in science. Second, because I predicted it would years ago (not that this was all that difficult to see coming!). And third, for personal reasons, because I know all three of these men. I worked with Brian and Adam back in the day; the project Brian headed up to observe distant supernovae was part of a project using Hubble to observe supernovae in general, and I worked on a different aspect of it. Adam and I were both grad students at the time; after I got my PhD I went to work on a different Hubble project, and Adam stayed with the team, cracked the supernova code, and now has a Nobel Prize.
I suspect that was the right move for him.
All three of these men have worked for a long, long time on this problem, essentially devoting their lives to it. It’s very, very nice to see that pay off. It’s richly deserved!
– The Universe is expanding at 73.8 +/- 2.4 km/sec/megaparsec! So there.
– News: dark energy stunts your growth
– The Universe is expanding at 74.2 km/sec/Mpc
– Hitting the gas
– The Universal expansion revisited
– What astronomers do
– AAS Post #6: The cosmological not-so-constant
In 1998, two teams of astronomers independently reported amazing and bizarre news: the Universal expansion known for decades was not slowing down as expected, but was speeding up. Something was accelerating the Universe.
Since then, the existence of this something was fiercely debated, but time after time it fought with and overcame objections. Almost all professional astronomers now accept it’s real, but we still don’t know what the heck is causing it. So scientists keep going back to the telescopes and try to figure it out.
[Click to galactinate, or grab the cosmic 3500 x 4000 pixel browser bruiser.]
This gorgeous image is of the nearby spiral galaxy NGC 5584, where of course "nearby" to an astronomer means 72 million light years. This galaxy is loaded with a specific type of variable star — called Cepheids — which are very important: the way they change their brightness depends on how luminous they are. Measure the change, and you measure the luminosity, and if you measure how bright they appear in the sky you get their distance. It’s a bit like judging how far away a car is by gauging how bright its headlights are. Except in this case astronomers use Hubble instead of their eyes. It’s a tad more accurate.
It so happens that in 2007, NGC 5584 was the host of a Type Ia supernova, the Golden Standard of distance indicators. These are so bright they can be seen clear across the Universe! By knowing the distance to the one in NGC 5584, we can then use that to get the distances to supernovae much, much farther away.
It’s a bootstrappy way of measuring the cosmic distance scale.
But it appears to work. Read More