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Astronomers Find Hyperactive
Galaxies in the Early Universe
Galaxies in the Early Universe
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"Victoria crater" Image Credit: NASA/JPL/Cornell SPACE
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Credit NASA
Looking almost 11 billion years into the past, astronomers have measured the motions of stars for
the first time in a very distant galaxy and clocked speeds upwards of one million miles per hour,
about twice the speed of our Sun through the Milky Way.
The fast-moving stars shed new light on how these distant galaxies, which are a fraction the size of
our Milky Way, may have evolved into the full-grown galaxies seen around us today. The results will
be published in the August 6, 2009 issue of the journal Nature, with a companion paper in the
Astrophysical Journal.
“This galaxy is very small, but the stars are whizzing around as if they were in a giant galaxy that we
would find closer to us and not so far back in time,” says Pieter van Dokkum, professor of
astronomy and physics at Yale University in New Haven, Conn., who led the study. It is still not
understood how galaxies like these, with so much mass in such a small volume, can form in the
early universe and then evolve into the galaxies we see in the more contemporary nearby universe
that is about 13.7 billion years old.
The work by the international team combined data collected using NASA’s Hubble Space
Telescope with observations taken by the 8-meter Gemini South telescope in Chile. According to
van Dokkum, “The Hubble data, taken in 2007, confirmed that this galaxy was a fraction the size of
most galaxies we see today in the more evolved, older universe. The giant 8-meter mirror of the
Gemini telescope then allowed us to collect enough light to determine the overall motions of the
stars using a technique not very different from the way police use laser light to catch speeding
cars.” The Gemini near-infrared spectroscopic observations required an extensive 29 hours on the
sky to collect the extremely faint light from the distant galaxy, which goes by the designation 1255-0.
“By looking at this galaxy we are able to look back in time and see what galaxies looked like in the
distant past when the universe was very young,” says team member Mariska Kriek of Princeton
University in Princeton, N.J. 1255-0 is so far away that the universe was only about 3 billion years
old when its light was emitted.
Astronomers confess that it is a difficult riddle to explain how such compact, massive galaxies form,
and why they are not seen in the current, local universe. “One possibility is that we are looking at
what will eventually be the dense central region of a very large galaxy,” explains team member
Marijn Franx of Leiden University in the Netherlands. “The centers of big galaxies may have formed
first, presumably together with the giant black holes that we know exist in today’s large galaxies that
we see nearby.”
To witness the formation of these extreme galaxies astronomers plan to observe galaxies even
further back in time in great detail. By using the Wide Field Camera 3, which was recently installed
on the Hubble Space Telescope, such objects should be detectable. “The ancestors of these
extreme galaxies should have quite spectacular properties as they probably formed a huge amount
of stars, in addition to a massive black hole, in a relatively short amount of time,” says van Dokkum.
This research follows recent studies revealing that the oldest, most luminous galaxies in the early
universe are very compact yet surprisingly have stellar masses similar to those of present-day
elliptical galaxies. The most massive galaxies we see in the local universe (where we don’t look
back in time significantly) which have a mass similar to 1255-0 are typically five times larger than a
young compact galaxy. How galaxies grew so much in the past 10 billion years is an active area of
research, and understanding the dynamics in these young compact galaxies is a key piece of
evidence in eventually solving this puzzle.
Source NASA.GOV
the first time in a very distant galaxy and clocked speeds upwards of one million miles per hour,
about twice the speed of our Sun through the Milky Way.
The fast-moving stars shed new light on how these distant galaxies, which are a fraction the size of
our Milky Way, may have evolved into the full-grown galaxies seen around us today. The results will
be published in the August 6, 2009 issue of the journal Nature, with a companion paper in the
Astrophysical Journal.
“This galaxy is very small, but the stars are whizzing around as if they were in a giant galaxy that we
would find closer to us and not so far back in time,” says Pieter van Dokkum, professor of
astronomy and physics at Yale University in New Haven, Conn., who led the study. It is still not
understood how galaxies like these, with so much mass in such a small volume, can form in the
early universe and then evolve into the galaxies we see in the more contemporary nearby universe
that is about 13.7 billion years old.
The work by the international team combined data collected using NASA’s Hubble Space
Telescope with observations taken by the 8-meter Gemini South telescope in Chile. According to
van Dokkum, “The Hubble data, taken in 2007, confirmed that this galaxy was a fraction the size of
most galaxies we see today in the more evolved, older universe. The giant 8-meter mirror of the
Gemini telescope then allowed us to collect enough light to determine the overall motions of the
stars using a technique not very different from the way police use laser light to catch speeding
cars.” The Gemini near-infrared spectroscopic observations required an extensive 29 hours on the
sky to collect the extremely faint light from the distant galaxy, which goes by the designation 1255-0.
“By looking at this galaxy we are able to look back in time and see what galaxies looked like in the
distant past when the universe was very young,” says team member Mariska Kriek of Princeton
University in Princeton, N.J. 1255-0 is so far away that the universe was only about 3 billion years
old when its light was emitted.
Astronomers confess that it is a difficult riddle to explain how such compact, massive galaxies form,
and why they are not seen in the current, local universe. “One possibility is that we are looking at
what will eventually be the dense central region of a very large galaxy,” explains team member
Marijn Franx of Leiden University in the Netherlands. “The centers of big galaxies may have formed
first, presumably together with the giant black holes that we know exist in today’s large galaxies that
we see nearby.”
To witness the formation of these extreme galaxies astronomers plan to observe galaxies even
further back in time in great detail. By using the Wide Field Camera 3, which was recently installed
on the Hubble Space Telescope, such objects should be detectable. “The ancestors of these
extreme galaxies should have quite spectacular properties as they probably formed a huge amount
of stars, in addition to a massive black hole, in a relatively short amount of time,” says van Dokkum.
This research follows recent studies revealing that the oldest, most luminous galaxies in the early
universe are very compact yet surprisingly have stellar masses similar to those of present-day
elliptical galaxies. The most massive galaxies we see in the local universe (where we don’t look
back in time significantly) which have a mass similar to 1255-0 are typically five times larger than a
young compact galaxy. How galaxies grew so much in the past 10 billion years is an active area of
research, and understanding the dynamics in these young compact galaxies is a key piece of
evidence in eventually solving this puzzle.
Source NASA.GOV
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