The further away an object is in space, the further back in time an astronomer is looking. This phenomenon allows astronomers and cosmologists to see how the universe has evolved over time and is especially important when studying galaxy formation. Looking at galaxies from different distances from Earth, we can see galaxies in different stages of their development. As time wore on, we have been able to detect galaxies that are earlier and earlier in their stages of development and recently astronomers have made another huge step by discovering what is thought to be furthest object from us ever found: a galaxy named UDFy-38135539. This galaxy and others near it are so young that they have not developed quasars and may even hold the key to how supermassive black holes develop. As we discover more galaxies closer to the cosmological horizon, the more we can learn about the universe we live in.
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| UDFy-381335539 Image: NASA, ESA, G. Illingworth (UCO/ Lick Observatory and University of California, Santa Cruz) and the HUDF09 Team |
Every so often, astronomers will find an object that is further than any object ever spotted before. Sometimes this comes because of a technological advance such as a new telescope or sometimes it can be because the data has simply not been mined through. The most recent object that has taken the crown of furthest ever discovered is the galaxy UDFy-3135539, and this eclipsed a gamma-burst detected in 2009. UDFy-3135539 was discovered in a deep-space picture taken by the Hubble Space Telescope in 2009 with the new Wide Field Camera 3 or WFC3. Only now have astronomers discovered its redshift which is z ∼ 8.55. This number makes the galaxy 13 billion years old, only about 600 years since the big bang. (Matson) Even this young, the galaxy is thought to be the home of second or third generation stars; first generation stars were so big that they would have already exploded by this point in the universe’s history
UDFy-3135539 was part of a group of objects that were discovered with the WFC3 that were candidates for being extremely distant objects. It was unclear which object was the furthest until follow-up observations were conducted. The Very Large Telescope (VLT) in Chile assisted in providing data and showed that of these objects, UDFy-3135539 was the furthest and also happened to be the furthest object ever discovered.
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| VLT |
Seeing this far back in time may give clues to one of the biggest questions in astro-physics: how a super-massive black hole is formed. Astronomers do not know definitively how these black holes came to be; it is presumed that these supermassive black holes formed by first nucleating and then sucking in matter, but this sucking would be slow so they must have started with at least one hundred solar masses. (Matson) There are still questions about how exactly this could occur, but being able to see this far back in time may give astronomers the information necessary to find out. In the close universe, the largest black hole that a star can leave behind is about ten solar masses, an insufficient amount. The difference, however, is that today’s universe has much more heavy elements in it than in the distant past. As stated before, UDFy-3135539 probably consists of second or third generation stars, so it will have some heavier elements, but nowhere near the amount that today’s stars have because of the generations of recycling that has occurred since then. This key difference might be the answer to how these supermassive black holes formed early on: It may be that supermassive black holes are the remnants of exploded massive first generation “titans” or it could be that without heavier elements, gas clouds of a thousand solar masses or more could become gravitationally unstable and thus collapse into a black hole. (Musser) Neither of these things is possible today because of the presence of heavy elements, so seeing this far back in time is an excellent tool.
Another question that could be answered with this discovery is how galaxies are formed. Observing UDFy-3135539 shows that it is only 1% of the mass the Milky Way is today. Astronomers have also determined that the stars in this early galaxy are roughly 300 million years old, meaning they formed only 300 million years after the Big Bang. The galaxy’s star formation was only about a tenth of what it is today. Eventually in the course of the universe’s history star formation would pick up rapidly and then steadily decline until now. Having a sample of a galaxy that existed before this pick up in star formation rate could be useful in finding out how the universe developed and how future galaxies formed.
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| Milky Way (Image Courtesy of David Peralty) |
This early galaxy may be home to some of the first luminous sources, and thus may give clues to astronomers about the epoch of reionization. “The Epoch of Reionization (EOR) refers to the period in the history of the universe during which the predominantly neutral intergalactic medium was ionized.” (MIT Haystack Observatory) After the Big Bang occurred, the universe was too hot for electrons and protons to form, so there was no neutral hydrogen. After a few hundred thousand years, this was made possible and eventually the universe became neutral and opaque until the first galaxies formed. (MIT Haystack Observatory) Since we cannot see anything past this point, finding one of the first galaxies would be crucial for knowledge about the universe’s formation, and UDFy-3135539 may be that galaxy. By studying reionization, we can see how the structure of the universe has changed over the years; recent discoveries have shown that there was smooth matter distribution in the early times and since a redshift of z ∼ 6 there has been a structured universe filled with galaxies and clusters of galaxies. This time in the history of the universe remains largely unknown, but with the discovery of UDFy-3135539, more light may be shed on it.
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| Image Courtesy of MIT Haystack Observatory |
With every new discovery of a distant galaxy, astronomers can look closer to the beginning of the universe. With this knowledge, astronomers can see how supermassive black holes were formed, how galaxies were formed, and what the universe was like in its earliest stages. Newer technology is allowing astronomers to see more distant objects and is making scientists better judges of exactly how far these objects are. Newer and better telescopes can see distances we could only speculate decades ago. The James Webb Space Telescope is the next telescope in line of production, and it may be able to tell us ever more about the early universe. Until then, UDFy-38135539 is our best look at the early universe and it is a excellent discovery for astronomers.
Works Cited
Bouwens, R. J., G. D. Illingworth, P. A. Oesch, M. Stiavelli, P Van Dokkum, M. Trenti, D. Magee, I. Labbe, M. Franx, C. M. Carollo, and V. Gonzalez. "Discovery of Z 8 Galaxies in the Hubble Ultra Deep Field from Ultra-Deep WFC3/IR Observations." The Astrophysical Journal Letters. The American Astronomical Society, 1 Feb. 2010. Web.
"Epoch of Reionization." Haystack Observatory. MIT. Web.
Matson, John. "Early Bloomer: Faraway Galaxy Pushes Cosmic View Closer to the Dawn of the Universe: Scientific American." Scientific American. 20 Oct. 2010. Web. 08 Dec. 2010.
Matson, John. "Astronomical Artifact: Most Distant Object Yet Detected Carries Clues from Early Universe: Scientific American." Scientific American. 28 Oct. 2009. Web. 08 Dec. 2010.
Musser, George. "Observations: In Praise of Small Things: Second Dispatch from the American Astronomical Society Meeting." Scientific American. 14 Jan. 2010. Web. 08 Dec. 2010.
