November 15, 2012
Newly Discovered Galaxy Breaks Most Distant Record
Lee Rannals for redOrbit.com — Your Universe Online
The newly discovered galaxy, named MACS0647-JD, is only a tiny fraction of the size of our Milky Way galaxy, and is observed at 420 million years after the big bang.
MACS0647-JD offers a glimpse into what the universe was like when it was just three percent of its present age of 13.7 billion years old.
Astronomers had to use massive galaxy clusters as a cosmic telescope to magnify distant galaxies behind them, which is an effect called gravitational lensing.
About 8 billion years into its journey, the light from MACS0647-JD crossed around the massive galaxy cluster MACS J0647+7015. NASA said without this cluster's magnification powers, astronomers would not have been able to see this remote galaxy.
The research team was able to observe three magnified images of MACS0647-JD with the Hubble Space Telescope. The cluster's gravity helped boost the light from the galaxy, making the image appear about eight, seven, and two times brighter than they otherwise would have shown up to astronomers without the cluster.
"This cluster does what no manmade telescope can do," Marc Postman of the Space Telescope Science Institute said in a statement. "Without the magnification, it would require a Herculean effort to observe this galaxy."
The galaxy is so small, that it could be the first steps of forming a larger galaxy. An analysis shows it is less than 600 light-years wide. A typical galaxy of a similar age would be about 2,000 light-years wide, according to NASA. Our Milky Way galaxy is 150,000 light-years across.
"This object may be one of many building blocks of a galaxy," the study's lead author, Dan Coe of the Space Telescope Science Institute, said in the statement. "Over the next 13 billion years, it may have dozens, hundreds, or even thousands of merging events with other galaxies and galaxy fragments."
The galaxy was observed with 17 filters and was discovered in February while looking over a catalog of thousands of gravitationally lensed objects found in Hubble observations.
"So either MACS0647-JD is a very red object, only shining at red wavelengths, or it is extremely distant and its light has been 'redshifted' to these wavelengths, or some combination of the two," Coe said. "We considered this full range of possibilities."
The team spent months systematically ruling out other alternative explanations for the object's identify, including red stars, brown dwarfs, and red galaxies. They determined a very distant galaxy was the correct explanation.
MACS0647-JD is too far away for any current telescope to confirm the distance based on spectroscopy, but Coe is confident in the team's analysis.
"All three of the lensed galaxy images match fairly well and are in positions you would expect for a galaxy at that remote distance when you look at the predictions from our best lens models for this cluster," Coe said in the statement.
The discovery beats out a previously found galaxy by the same group of astronomers announced earlier this year. This galaxy was 490 million years old, 70 million years younger than the new galaxy.
The researchers will be publishing their findings in the December 20 issue of The Astrophysical Journal.