Phil Plait at Slate has picked “The Best Astronomy Images of 2012”. He narrowed it down to his favorite 21. They are all good; here I’ve copied my favorite four. See the Slate article for more complete descriptions, and the other 17 images.
Huge Solar Arch – On August 31, 2012, a big arch of material blasted off the Sun’s surface. By “big” we mean 200,000 miles (300,000 km) across, which is 25 times the diameter of the Earth. More such emanations are expected as the Sun’s magnetic cycle peaks in coming months.
Self-Portrait of “Curiosity” Mars Rover
NASA/JPL-Caltech/Malin Space Science Systems.
Twin Jets From Black Hole Disk – - A large black hole, with 2.5 billion times the mass of the Sun, lies in the heart of galaxy Hercules A. Nearby material falls into it and gets ripped apart and sucked into the black hole. On its way in, this material forms a superheated disk where some of it expands violently. Various forces focus this expanding material into two jets that shoot out for hundreds of thousands of light years before they slow down and puff into twin lobes of matter.
NASA, ESA, S. Baum and C. O’Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA).
Deep Field of Galaxies- – This is an image assembled from photos by the Hubble space telescope totaling 23 days of exposure. The target area (“Hubble Extreme Deep Field”) is a region of the sky that seems to be empty, according to normal observation. But this long exposure by Hubble’s eagle eye detects thousands of objects here. Nearly every object in this shot is actually a galaxy, each containing billions of stars. Extrapolation from this image indicates that there are hundreds of billions of such galaxies in the Universe, most of them billions of light-years away.
NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa Cruz), R. Bouwens (Leiden University), and the HUDF09 Team.
As a follow-up, this article zooms into the photo above, and identifies several galaxies that are around 13 billion years old. For one of these galaxies, estimated at 13.3 billion years old, we are seeing light from something that dates to only about 400 million years after the Big Bang itself.