Astronomers see giant galaxy being born

The Spiderweb Galaxy – which spans some 3 times the diameter of our Milky Way – is forming inside a cluster of protogalaxies, in a dense soup of molecular gas.

Artist's conception of the Spiderweb. In this image, the protogalaxies are shown in white and pink, and the blue indicates the location of the carbon monoxide gas in which the protogalaxies are immersed. Image via ESO/ M. Kornmesser/ NRAO.

Artist’s concept of the Spiderweb, a giant galaxy forming inside a cluster of protogalaxies, shown here in white and pink. Blue indicates carbon monoxide gas in which the system is immersed. Image via ESO/ M. Kornmesser/ NRAO.

The National Radio Astronomy Observatory (NROA) announced late last week (December 1, 2016) that astronomers used radio telescopes to scrutinize a giant galaxy forming at the center of a cluster of protogalaxies in the early universe. Their observations show the giant galaxy appears to be forming within what they say is a “surprisingly dense soup” of molecular gas. This is the Spiderweb Galaxy, not yet a single galaxy, but still a clustering of protogalaxies, or galaxies emerging from their cloud of cold gas. Astronomers see this cluster not as it appears today, but as it was more than 10 billion years ago, when the universe was approximately 3 billion years old.

The astronomers reported their findings in the December 2, 2016 issue of the peer-reviewed journal Science.

Bjorn Emonts of the Center for Astrobiology in Spain led the international research team. He said in a statement:

This is different from what we see in the nearby universe, where galaxies in clusters grow by cannibalizing other galaxies. In this cluster, a giant galaxy is growing by feeding on the soup of cold gas in which it is submerged.

And that’s just what you might expect in the very young universe, when some of the earliest stars and galaxies were just beginning to form.

The astronomers used the Australia Telescope Compact Array (ATCA) and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) to detect carbon monoxide gas. They explained:

The presence of [this gas] indicates a larger quantity of molecular hydrogen, which is much more difficult to detect. The astronomers estimated that the molecular gas totals more than 100 billion times the mass of the sun.

Not only is this quantity of gas surprising … but the gas also must be unexpectedly cold, about minus-200 degrees Celsius. Such cold molecular gas is the raw material for new stars.

The [carbon monoxide] in this gas indicates that it has been enriched by the supernova explosions of earlier generations of stars. The carbon and oxygen in the CO was formed in the cores of stars that later exploded.

The astronomers said that the ATCA observations revealed the total extent of the gas, and the VLA observations, much more narrowly focused, provided another surprise. Most of the cold gas was found, not within the protogalaxies, but instead between them. Astronomer Preshanth Jagannathan of the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico said:

This is a huge system, with this molecular gas spanning three times the size of our own Milky Way galaxy.

Earlier observations of the Spiderweb, made at ultraviolet wavelengths, have indicated that rapid star formation is ongoing across most of the region occupied by the gas. Jagannathan said:

It appears that this whole system eventually will collapse into a single, gigantic galaxy.

An earlier view of the Spiderweb galaxy - aka MRC1138-262 - from the Hubble Space Telescope in 2006. The newer observations give us a much-better look at the gas from which this giant galaxy is forming. Image via Wikimedia Commons.

An earlier view of the Spiderweb galaxy – aka MRC1138-262 – from the Hubble Space Telescope in 2006. The newer observations give us a much-better look at the gas from which this giant galaxy is forming. Image via Wikimedia Commons.

Bottom line: Radio astronomers studying the Spiderweb Galaxy – a giant galaxy forming inside a cluster of protogalaxies – saw that it is forming inside a “surprisingly dense soup” of molecular gas.

Via NRAO

Deborah Byrd