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Sometimes if you aren’t watching the heavens (or the news) closely enough, you miss a major astronomical discovery. For example last summer, astronomers discovered a galaxy which formed only one or two billion years after the Big Bang (so I guess it is unclear whethter I missed this story by one year or by 12 billion). At any rate, the galaxy hunters used the Hubble space telescope to peer through a powerful gravitational lense far away in space. Gravitational lenses are areas where timespace is warped like a huge lense by high-gravity phenomena, and a viewer can use them like a huge lense to see far-away objects. By using the Hubble telescope together with the gravitational lense they were able to see back a dozen billion years in time to the edge of the universe…as it once was not long after creation. What they saw perplexed them.
There is a fundamental difference between galaxies. Galaxies where stars are being formed tend to be blue and spiral shaped (like our own beloved Milky Way!). Galaxies where stars have largely stopped forming are “red and dead” since the remaining stars tend to be long lived red dwarf stars and the bright young (short-lived) blue stars are mostly gone. These red galaxies are not shaped like spirals, but tend to be elliptical shaped (like an egg or a football, not like one of those evil gym machines).
The ancient galaxy at the edge of the universe was neither of those colors or shapes. It was a dense yellow disk. Stars formed in an (enormous) accretion disk but then, for some reason, new star formation stopped. The blue stars burned out (“the light that shines twice as bright etc, etc..”), but the yellow middle aged stars were still burning. The galaxy had three times the mass of the Milky Way but scrunched into a pancake of much smaller area.
So do galaxies always form as disks and then either become self-renewing blue spirals (maybe by colliding with other galaxies or clouds of dust)or dead red footballs? Or was this early yellow disk galaxy an abberation? Or is our own galaxy truly new (well…newish…being only a few billion years old)? I do not understand astrophysics well enough to answer these questions or even formulate them properly (although I get the sense some of these questions may not yet be answered by anyone in any comprehensive way), but I would love to hear what people can add to this rudimentary yet compelling story of shapes and colors.
A Composite Image of M104–The Sombrero Galaxy–taken from the Hubble Space Teelscope in Summer of 2003 (click on the image for a full-sized version)
Today I am posting some pictures of what I think is the most beautiful deep space object. The Sombrero Galaxy (M104) is a nearby galaxy which is visible edge-on in the constellation of Virgo. Actually, calling it an object might be a bit misleading since M104 consists of more than 400 billion stars–not to mention numerous associated globular clusters, innumerable planets, immense clouds of gas & gas, and a supermassive black hole which lies in the center. The black hole in the center of M104 isn’t a mild mannered & quiescent black hole like the one in the center of the Milky Way either. Based on the speed of revolution of the stars near the middle of M104, astronomers calculate that the central black hole has a billion times the mass of the sun.
An Infrared false-color image of the Sombrero Galaxy
In cosmic terms, the Sombrero galaxy is nearby—which is to say it is merely 28-odd million light years away. The galaxy was discovered in the late eighteenth century by Pierre Méchain . Other prominent 18th century astronomers subsequently observed and studied M104, including Charles Messier (which is the reason the galaxy is included in the “Messier” catalog and has a M-designation) and the redoubtable William Herschel who noted a “dark-stratum” bounding the luminous central bulge. We now know that this ring around M104 is a toroid dust lane of vast proportions which halos the galaxy. Astronomers initially thought that the Sombrero Galaxy was an unbarred spiral galaxy, but thanks to observations from NASA’s Spitzer space telescope (an infrared scope orbiting Earth), the scientific community has revised their estimation of its size upward. It lies somewhere between a spiral galaxy and an elliptical galaxy. In other words, when you look at the Sombrero Galaxy, you are looking at something vast beyond human comprehension—a galaxy bigger than our own filled with who knows what things we will never know. And yet if you expand the Hubble photo at the top of this post, you will see that all of the little stars shining around M104 are other galaxies farther away.
Olé!
ferrebeekeeper 