NASA's Hubble Space Telescope

Astronomers Uncover an Overheated Early Universe

If you think global warming is bad, 11 billion years ago the entire universe underwent, well, universal warming.The consequence was that fierce blasts of radiation from voracious black holes stunted the growth of some small galaxies for a stretch of 500 million years.
This diagram traces the evolution of the universe from the big bang to the present. Two watershed epochs are shown. Not long after the big bang, light from the first stars burned off a fog of cold hydrogen in a process called reionization. At a later epoch quasars, the black-hole-powered cores of active galaxies, pumped out enough ultraviolet light to reionize the primordial helium.

This diagram traces the evolution of the universe from the big bang to the present. Two watershed epochs are shown. Not long after the big bang, light from the first stars burned off a fog of cold hydrogen in a process called reionization. At a later epoch quasars, the black-hole-powered cores of active galaxies, pumped out enough ultraviolet light to reionize the primordial helium.

This is the conclusion of a team of astronomers who used the new capabilities of NASA's Hubble Space Telescope to probe the invisible, remote universe.

Using the newly installed Cosmic Origins Spectrograph (COS) they have identified an era, from 11.7 to 11.3 billion years ago, when the universe stripped electrons off from primeval helium atoms — a process called ionization. This process heated intergalactic gas and inhibited it from gravitationally collapsing to form new generations of stars in some small galaxies. The lowest-mass galaxies were not even able to hold onto their gas, and it escaped back into intergalactic space.

Michael Shull of the University of Colorado and his team were able to find the telltale helium spectral absorption lines in the ultraviolet light from a quasar — the brilliant core of an active galaxy. The quasar beacon shines light through intervening clouds of otherwise invisible gas, like a headlight shining through a fog. The beam allows for a core-sample probe of the clouds of gas interspersed between galaxies in the early universe.

The universe went through an initial heat wave over 13 billion years ago when energy from early massive stars ionized cold interstellar hydrogen from the big bang. This epoch is actually called reionization because the hydrogen nuclei were originally in an ionized state shortly after the big bang.

But Hubble found that it would take another 2 billion years before the universe produced sources of ultraviolet radiation with enough energy to do the heavy lifting and reionize the primordial helium that was also cooked up in the big bang.

This radiation didn't come from stars, but rather from quasars. In fact the epoch when the helium was being reionized corresponds to a transitory time in the universe's history when quasars were most abundant.

The universe was a rambunctious place back then. Galaxies frequently collided, and this engorged supermassive black holes in the cores of galaxies with infalling gas. The black holes furiously converted some of the gravitational energy of this mass to powerful far-ultraviolet radiation that would blaze out of galaxies. This heated the intergalactic helium from 18,000 degrees Fahrenheit to nearly 40,000 degrees. After the helium was reionized in the universe, intergalactic gas again cooled down and dwarf galaxies could resume normal assembly. "I imagine quite a few more dwarf galaxies may have formed if helium reionization had not taken place," said Shull.

So far Shull and his team only have one sightline to measure the helium transition, but the COS science team plans to use Hubble to look in other directions to see if the helium reionization uniformly took place across the universe.

The science team's results will be published in the October 20 issue of The Astrophysical Journal.

Source: Hubblesite
» print article
Related articles:
This image shows the entire region around supernova 1987A. The most prominent feature in the image is a ring with dozens of bright spots. A shock wave of material unleashed by the stellar blast is slamming into regions along the ring's inner regions, heating them up, and causing them to glow. The ring, about a light-year across, was probably shed by the star about 20,000 years before it exploded.
Shocked Region Around SN 1987A

New Hubble Observations of Supernova 1987A Trace Shock Wave

» go to article
A cosmic concoction in NGC 2467
Hubble Space Telescope image of NGC 2467

Hubble snaps sharp image of cosmic concoction

» go to article
This broad vista of young stars and gas clouds in our neighbouring galaxy, the Large Magellanic Cloud, was captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS). This region is named LHA 120-N 11, informally known as N11, and is one of the most active star-forming regions in the nearby Universe. This picture is a mosaic of ACS data from five different positions and covers a region of about 6 arcmin across.
The Large Magellanic Cloud

Hubble captures bubbles and baby stars

» go to article
The core of the star cluster in NGC 3603 is shown in great detail in an image from the Wide Field Planetary Camera 2 (WFPC2) camera on the NASA/ESA Hubble Space Telescope. The image is a colour composite of observations in the WFPC2 filters F555W (blue), F675W (green) and F814W (red). This view shows the second of two images taken ten years apart that were used to detect the motions of individual stars within the cluster for the first time. The field of view is about 20 arcseconds across.
Surprising signs of unrest in massive star cluster

Hubble catches stars on the move

» go to article
This craggy fantasy mountaintop shrouded by wispy clouds looks like a bizarre landscape from Tolkien’s The Lord of the Rings. The NASA/ESA Hubble Space Telescope image, which is even more dramatic than fiction, captures the chaotic activity atop a pillar of gas and dust, three light-years tall, which is being eaten away by the brilliant light from nearby bright stars. The pillar is also being assaulted from within, as infant stars buried inside it fire off jets of gas that can be seen streaming from towering peaks.
Hubble Space Telescope

Hubble celebrates 20 years of awe and discovery

» go to article
The illustration shows the redshift of the spectral lines of a far-away super galaxy cluster (BAS11). Compared to those of the Sun (top), the spectral lines of the galaxy cluster (bottom) are shifted into the red.
Redshift

How quickly is the Universe expanding?

» go to article
Search
Astronomy Software

Redshift iphone Neu

Redshift for iPhone, iPad and iPod touch

The award winning Astronomy Software Redshift is now available for iPhone, iPod touch and iPad. » more

Redshift Astronomie

Redshift Astronomy - Download Edition

Redshift for iOS has been consistently voted five of five stars and featured in Apple’s 2011 rewind!
The Mac version Redshift Astronomy with even more features is now available for Mac! » more