Astronomy Now Home
Home Magazine Resources Store

On Sale Now!

The October 2014 issue of Astronomy Now is on sale! Order direct from our store (free 1st class post & to UK addresses). Astronomy Now is the only astronomy magazine specially designed to be read on tablets and phones. Download the app from Google Play Store or the Apple App Store.

Top Stories

Earthshine used to test life detection method
...By imagining the Earth as an exoplanet, scientists observing our planet's reflected light on the Moon with ESO's Very Large Telescope have demonstrated a way to detect life on other worlds...

Solid buckyballs discovered in space
...Astronomers using NASA’s Spitzer Space Telescope have detected a particular type of molecule, given the nickname “buckyball”, in a solid form for the first time...

Steamy water-world gets the Hubble treatment
...Hubble Space Telescope observations of a 7 Earth-mass planet find an unusual water-rich world swathed in a thick, steamy atmosphere...

Watching a galaxy blow
itself to old age

Posted: 12 January 2011

Bookmark and Share

A lenticular-shaped galaxy 100 million light years away is expelling all its star-forming molecular gas, setting itself up for an infertile future where it will form no more stars and become ‘red and dead’.

Two types of disc galaxy inhabit the Universe: spiral galaxies like our Milky Way that have blue arms glowing with star formation, and dusty red discs, termed lenticular galaxies, where star formation has long since ceased and the only stars that remain are the old, cool, red stars. Until now, however, the link between the two – how a spiral evolves into a dusty red galaxy – has been a mystery.

On the left is a greyscale optical image of NGC 1266, but infrared and millimetre-wave observations of the galaxy’s inner regions reveal a dense disc of molecular gas that is being expelled from NGC 1266 at a tremendous rate. This outflow appears as two lobes, indicated by contour lines, in the zoomed-in image on the right. Click on the image to see a larger version. Image: Katherine Alatalo/UC Berkeley.

Astronomers at the University of California, Berkeley took a closer look at the lenticular galaxy NGC 1266, a magnitude +14 object in the constellation of Eridanus, with the aid of data from the ATLAS3D ( – a multi-telescope, multi-wavelength survey of 263 galaxies in a volume of space within 140 million light years. What they found was surprising: all the galaxy’s molecular hydrogen gas, which is the gas that can form stars, has wound up in a dense rotating disc 300 light years in diameter circling the core of the galaxy, where a supermassive black hole lurks. This disc of gas is 100 times more dense than a typical molecular cloud such as the Orion Nebula. Furthermore, this gas is being expelled by a powerful 400-kilometre per second outflow at a rate of 13 solar masses (the Sun’s mass is 1.98 x 1030 kilograms) per year. If the galaxy keeps up this current rate of outflow, NGC 1266 will have exhausted all its molecular gas within 85 million years, leaving it ‘red and dead’.

However, the lack of a clear explanation for the outflow prevents astronomers from saying whether such behaviour happens to all galaxies evolving from blue spirals to red lenticulars, or whether this is a one-off case unique to NGC 1266. Despite intensive searching no companion galaxies that could forcibly eject the gas though tidal forces have been found. A intense area of star formation inside the inner disc could produce enough energy to drive the outflow, but there is no evidence of such a ‘starburst’ taking place in NGC 1266. “We find that we are seeing fewer stars form than we would expect,” says Katherine Alatalo, a graduate student at the University of California, Berkeley. “In particular, the gas in the inner disc should form about ten solar masses a year, but instead is forming at most three solar masses per year if we assume that all the far-infrared flux is coming from star formation, which is an unrealistic assumption in the presence of an active galactic nuclei. More realistically it is 1.5 solar masses per year using the more accurate 24 micron emission observed by the Spitzer Space Telescope.”

Rather than star formation, jets from the supermassive black hole at the heart of NGC 1266 are the chief suspect. An active black hole is termed an active galactic nuclei, or AGN. “We don’t yet know if the AGN is powering the molecular winds directly or whether the molecular gas is entrained by narrow jets that that have yet to be observed,” says Professor Leo Blitz of the University of California, Berkeley. Jets such as those seen in M87 in Virgo can remain switched on long enough to drive out all the molecular gas.

The research is to be published in the Astrophysical Journal;, and was presented at the 217th meeting of the American Astronomical Society, taking place this week in Seattle. Does the research imply a link between all AGN and red and dead galaxies? Possibly. “However,” cautions Blitz, “It would be best to first find a few more examples of NGC 1266-type galaxies and see whether their outflows are all powered by AGN.”

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!


© 2014 Pole Star Publications Ltd.