Tuesday, June 14, 2011

Are sunspots going away?

A press conference today announced three research projects that suggest that our sun's familiar sunspot cycle might be heading toward a major change or even a pause.  You can read good summaries of the findings in this post from space.com and this article on Universe Today; I'll wait while you do that and then give you my first thoughts on this news.

Done reading?  Good.  First, let me state that I am not a solar physicist, and I do not claim to be an authority on the research being done.  So feel free to take my opinions with a grain of salt.

A new type of supernova?

Image Credit: Caltech / Robert Quimby / Nature
Last week, a group of astronomers led by Caltech astronomer Robert Quimby announced that they had learned a few crucial pieces of information about these enigmatic sources.  This new evidence suggests that we are seeing a new type of stellar explosion, though we still don't know exactly what we are seeing.

Two years ago, I attended a conference on supernovae (exploding stars), and I blogged about weird objects that we could not explain.  In apparently blank parts of the sky, a couple of "new stars" had appeared and slowly faded away, just like supernovae.  Only these new objects changed their brightness on much longer time scales than normal supernovae, they did not appear to be located inside another galaxy, and their spectra showed weird features that could not be identified with certitude.  Many different explanations were proposed, from white dwarf stars in our own Milky Way Galaxy to carbon stars being shredded by black holes halfway across the Universe.

Friday, June 10, 2011

A supernova in the Whirlpool Galaxy

Supernova 2011dh in the Whirlpool Galaxy.  Image Credit: Peter Edwards
Supernovae, the explosive end of the life of some stars, are among the most powerful and most spectacular events in the universe.  They are also very rare.  Our Milky Way galaxy, with tens of billions of stars, sees one of them explode every 100 years or so.  The last known supernova in our galaxy was seen in 1604 and was studied by the famous astronomer Johannes Kepler.  Since that time, we think that at least two stars may have exploded in the Milky Way, with the explosions veiled by some of the Milky Way's many thick, opaque clouds of dust and gas.  But none have been seen.

Thankfully, there are lots of galaxies in the universe.  So, when astronomers want to study supernovae, they look at a lot of galaxies.  Such surveys for supernovae are turning up new explosions in distant galaxies all the time.  Still, many of these galaxies are fairly far away, and it is rare to find a supernova in our neck of the woods.

Enter the Whirlpool Galaxy, also called Messier 51.  The Whirlpool is nearby, as far as galaxies go – "only" 26 million light-years away.  It is also a favorite target of amateur astronomers, because it is a beautiful face-on spiral galaxy, and its spiral arms can be glimpsed by modest-sized telescopes in dark places.  Last week, sometime before the evening of May 31, a star exploded in one of the spiral arms.  The picture at the top of this post shows a picture with the supernova (the "new star" marked by white lines on the left picture) and a picture of the galaxy taken a couple of months ago, before the star exploded.