Friday, March 29, 2013
A Gorgeous Galaxy Like our Own
We live in an enormous "island" of stars called the Milky Way galaxy -- a collection of over 200 billion stars (and probably billions of planets). Since we are inside the Milky Way, it's hard to take a complete picture of it. It's like trying to take a picture of yourself from inside your gall bladder -- the view is not too clear. But we can learn about our own galaxy by observing others that are like us in size and shape.
In this beautiful picture, assembled from a Hubble Space Telescope image, as well as color information from a Japanese telescope and other observers, you can see a near cousin of the Milky Way located at a distance of about 50 million lightyears. (That means the light from this great "city of stars" took 50 million years to reach us!)
This galaxy doesn't have a name (like most galaxies), but simply referred to by a catalog number -- NGC 7331. Like our Milky Way, it is a spiral-shaped assemblage of stars and cosmic gas and dust. It contains about the same amount of material as our galaxy. We see it tilted to our line of sight, accounting for its oval (rather than circular) appearance.
It appears from other observations that NGC 7331 has a giant black hole at the center that has swallowed much more material than the black hole at the heart of the Milky Way. We are no longer surprised when we find giant black holes at the cores of galaxies -- it appears most grown-up galaxies have them.
Above and to the left of NGC 7331 are two other galaxies, which are about 10 times farther away! They just happen to be in the frame of the picture, like movie extras behind the actor whom our attention is focused on. Billions upon billions of galaxies make up the observable universe.
This gorgeous picture was assembled from different sources by Dr. Robert Gendler, a physician on the East Coast, whose passion is astronomical photography and whose skill at computer rendering of our skies is extra-ordinary. As many students and teachers travel or rest for spring vacation around this time of year, here is a celestial tourist sight for your enjoyment.