The least massive galaxy in the known universe has been measured by UC Irvine scientists, clocking in at just 1,000 or so stars with a bit of dark matter holding them together.
This image shows a standard prediction for the dark matter distribution within about 1 million light years of the Milky Way galaxy. Image credit: Garrison-Kimmel, Bullock (UCI)The findings, made with the W. M. Keck Observatory and published today in The Astrophysical Journal, offer tantalizing clues about how iron, carbon and other elements key to human life originally formed. But the size and weight of Segue 2, as the star body is called, are its most extraordinary aspects.
“Finding a galaxy as tiny as Segue 2 is like discovering an elephant smaller than a mouse,” said UC Irvine cosmologist James Bullock, co-author of the paper. Astronomers have been searching for years for this type of dwarf galaxy, long predicted to be swarming around the Milky Way. Their inability to find any, he said, “has been a major puzzle, suggesting that perhaps our theoretical understanding of structure formation in the universe was flawed in a serious way.”
Two hungry young galaxies that collided 11 billion years ago are rapidly forming a massive galaxy about 10 times the size of the Milky Way, according to UC Irvine-led research conducted on the W. M. Keck Observatory and other research facilities around the world. The results will be published today in the journal Nature.
The image at right shows a close-up of the colliding galaxies in red and green. The red data show dust-enshrouded regions of star formation. The green data show gas in the merging galaxies. The blue spots are visible-light observations of galaxies located much closer to us. Credit: JPL-Caltech/UC Irvine/Keck Observatory/STScI/NRAO/SAO/ESA/NASACapturing the creation of this type of large, short-lived star body is extremely rare – the equivalent of discovering a missing link between winged dinosaurs and early birds, said the scientists, who relied primarily on data from Keck Observatory’s NIRC2 fitted with the laser guide star adaptive optics (LGSAO) system. The new mega-galaxy, dubbed HXMM01, is the brightest, most luminous and most gas-rich submillimeter-bright galaxy merger known.
HXMM01 is fading away as fast as it forms, a victim of its own cataclysmic birth. As the two parent galaxies smashed together, they gobbled up huge amounts of hydrogen, emptying that corner of the universe of the star-making gas.
“These galaxies entered a feeding frenzy that would quickly exhaust the food supply in the following hundreds of million years and lead to the new galaxy’s slow starvation for the rest of its life,” said lead author Hai Fu, a UC Irvine postdoctoral scholar.
The discovery solves a riddle in understanding how giant elliptical galaxies developed quickly in the early universe and why they stopped producing stars soon after. Other astronomers have theorized that giant black holes in the heart of the galaxies blew strong winds that expelled the gas. But cosmologist Asantha Cooray, the UC Irvine team’s leader, said that they and colleagues across the globe found definitive proof that cosmic mergers and the resulting highly efficient consumption of gas for stars are causing the quick burnout.
A photo taken from my driveway of NGC1365 and supernova 2012fr. It is a bright supernova in a classic barred spiral galaxy. I had observed NGC1365 in mid-October with the 18″, noting the beautiful spiral structure. The supernova appeared about two weeks later. I have since observed it in a couple telescopes, including Cliff’s 24″.
The nova seems to be fading now, it peaked around 12th magnitude in November. Currently about 14.5 magnitude, but still easy with the AT6RC and Canon 20Da camera.
Astronomers using the Canada-France-Hawaii and W. M. Keck Observatory telescopes on the summit of Mauna Kea, Hawaii have been amazed to find a group of dwarf galaxies moving in unison in the vicinity of the Andromeda Galaxy. The structure of these small galaxies lies in a plane, analogous to the planets of the Solar System. Unexpectedly, they orbit the much larger Andromeda galaxy en masse, presenting a serious challenge to our ideas for the formation and evolution of all galaxies.
The findings are being reported on the cover the upcoming issue of the journal, Nature.
While Persian astronomers were the first to catalogue the Andromeda galaxy, only in the last five years that we have studied in exquisite detail the most distant suburbs of the Andromeda galaxy via the Pan-Andromeda Archaeological Survey (PAndAS), undertaken with the Canada-France-Hawaii Telescope and measured with the Keck Observatory, providing our first panoramic view of our closest large companion in the cosmos.
The study culminates many years of effort by an international team of scientists who have discovered a large number of the satellite galaxies, developed new techniques to measure their distances, and have used the Keck Observatory with colleagues to measure their radial velocities, or Doppler shifts (the speed of the galaxy relative to the Sun). While earlier work had hinted at the existence of this structure, the new study has demonstrated its existence to a high level of statistical confidence (99.998%).
New research using the world’s largest telescope at the Keck Observatory in Hawaii has revealed two distinct populations of star clusters surrounding galaxies that have radically different chemical compositions.
M22 or NGC6656 in Sagittarius, a classic globular clusterAn international team, led by Swinburne astronomers Christopher Usher and Professor Duncan Forbes, has measured the chemical composition of more than 900 star clusters in a dozen galaxies.
“This is ten times the number of star clusters previously examined, allowing us to confirm the existence of two chemically-distinct star clusters,” Mr Usher said.
A comprehensive study of hundreds of galaxies observed by the Keck telescopes in Hawaii and NASA’s Hubble Space Telescope has revealed an unexpected pattern of change that extends back 8 billion years, or more than half the age of the universe.
“Astronomers thought disk galaxies in the nearby universe had settled into their present form by about 8 billion years ago, with little additional development since,” said Susan Kassin, an astronomer at NASA’s Goddard Space Flight Center in Greenbelt, Md., and the study’s lead researcher. “The trend we’ve observed instead shows the opposite, that galaxies were steadily changing over this time period.”
Today, star-forming galaxies take the form of orderly disk-shaped systems, such as the Andromeda Galaxy or the Milky Way, where rotation dominates over other internal motions. The most distant blue galaxies in the study tend to be very different, exhibiting disorganized motions in multiple directions. There is a steady shift toward greater organization to the present time as the disorganized motions dissipate and rotation speeds increase. These galaxies are gradually settling into well-behaved disks.
This plot shows the fractions of settled disk galaxies in four time spans, each about 3 billion years long. Credit: Credit: NASA’s Goddard Space Flight Center
Blue galaxies—their color indicates stars are forming within them—show less disorganized motions and ever-faster rotation speeds the closer they are observed to the present. This trend holds true for galaxies of all masses, but the most massive systems always show the highest level of organization.
Researchers say the distant blue galaxies they studied are gradually transforming into rotating disk galaxies like our own Milky Way.
“Previous studies removed galaxies that did not look like the well-ordered rotating disks now common in the universe today,” said co-author Benjamin Weiner, an astronomer at the University of Arizona in Tucson. “By neglecting them, these studies examined only those rare galaxies in the distant universe that are well-behaved and concluded that galaxies didn’t change.”
So a little telescope called Hubble takes a picture of a galaxy, a really distant galaxy over 10 billion lightyears away. Odd, it looks like this galaxy has gotten it’s act together and become a spiral galaxy, a lot earlier than we thought proper spiral galaxies would form. What do you do? Get some time on a bigger telescope and get some more data… Using Keck the OSIRIS spectrograph astronomers show that this is indeed a proper spiral galaxy, 10.7 billion light years away, which means 10.7 billion years in the past. The universe has just served up another surprise for astronomers, this is the sort of stuff we love.
HST/Keck false colour composite image of galaxy BX442. Credit: David Law; Dunlap Insitute for Astronomy & AstrophysicsBetter yet, Keck gets a bit of good press for the discovery.
Along with the sensible headlines there are those that play up the “This can’t be” angle of the discovery. For the most part the articles are fairly good, it is just the headlines that seem a little off, something to blame on the editors who write the headlines…
Headlines are always an issue in science reporting. Written by editors with a tendency to the excessive and sensational. Editors who often have little understanding of the science. We have seen what that can lead to, something that has been pleasantly rare with this latest discovery.
Is this the “first” spiral? We have no way of knowing. I have found no such quote from the astronomers involved with the discovery. The reason we study the early universe is that we do not know. This discovery shows that there could be others, perhaps even older.
There are other headlines, predictable headlines from the usual suspects. Every time science turns up some surprise, something that does not fit a simplistic view of the universe, those with an ideological agenda attempt to use the discovery to push their views… “Look at this! It disproves everything!!”, ” The scientists have it all wrong!!” Quite predictable…
And of course, scientists will need to look for other exceptions to the rule. If an inexplicable and significant number of premature spirals are found, then the Big Bang theory will need to be rewritten, or disposed of altogether, no matter how beloved it is today. After all, it is just a theory.
Yes, again you see the “It is Just a Theory” gambit, the creationists favorite canard. All a discovery like this proves is that the universe is a complex and fascinating place and that we still have much to learn.
“BX442 represents a link between early galaxies that are much more turbulent than the rotating spiral galaxies that we see around us. Indeed, this galaxy may highlight the importance of merger interactions at any cosmic epoch in creating grand design spiral structure.” – Alice Shapely of UCLA, co-discoverer of BX442
In the beginning, galaxies were hot and clumpy – too hot to settle down and form grand spirals like the Milky Way and other galaxies seen in the nearby universe today. But astronomers have now been surprised by the discovery of a solitary grand design spiral galaxy in the early universe which could hold clues to how spirals start to take shape. The find was announced in a report in the July 19 edition of the journal Nature.
The ancient spiral, called BX442, was found by astronomers who first surveyed 300 distant galaxies using the Hubble Space Telescope, then followed up and confirmed using detailed observations and analyses from the W. M. Keck Observatory in Hawaii.
HST/Keck false colour composite image of galaxy BX442. Credit: David Law; Dunlap Insitute for Astronomy & Astrophysics
“As you go back in time to the early universe — about three billion years after the Big Bang; the light from this galaxy has been travelling to us for about 10.7 billion years —galaxies look really strange, clumpy and irregular, not symmetric” said astronomer Alice Shapley of UCLA. “The vast majority of old galaxies look like train wrecks. Our first thought was, why is this one so different, and so beautiful?”
Not only was the spiral shape clearly visible, but by using Keck’s OSIRIS instrument (OH-Suppressing Infrared Imaging Spectrograph), astronomers were able to study different parts of BX442 and determine that it is, in fact, rotating and not just two unrelated disk galaxies along the same line of sight that give the appearance of being a single spiral galaxy.
“We first thought this could just be an illusion and that perhaps we were being led astray by the picture,” said Shapley, a coauthor on the Nature paper. “What we found when we took spectra of this galaxy is that the spiral arms do belong to this galaxy; it wasn’t an illusion. Not only does it look like a rotating spiral disk galaxy; it really is. We were blown away.”
