"The surface of the Earth is the shore of the cosmic ocean... Recently, we've managed to wade a little way out, and the water seems inviting." - Carl Sagan
Starburst to star bust
New observations from the ALMA telescope in Chile have given astronomers the best view yet of how vigorous star formation can blast gas out of a galaxy and starve future generations of stars of the fuel they need to form and grow. The dramatic images show enormous outflows of molecular gas ejected by star-forming regions in the nearby Sculptor Galaxy.
Galaxies — systems like our own Milky Way that contain up to hundreds of billions of stars — are the basic building blocks of the cosmos. One ambitious goal of contemporary astronomy is to understand the ways in which galaxies grow and evolve, a key question being star formation: what determines the number of new stars that will form in a galaxy?
The Sculptor Galaxy, also known as NGC 253, is a spiral galaxy located in the southern constellation of Sculptor. At a distance of around 11.5 million light-years from our Solar System it is one of our closer intergalactic neighbours, and one of the closest starburst galaxies visible from the southern hemisphere. Using the Atacama Large Millimeter/submillimeter Array (ALMA) astronomers have discovered billowing columns of cold, dense gas fleeing from the centre of the galactic disc.
These results may help to explain why astronomers have found surprisingly few high-mass galaxies throughout the cosmos. Computer models show that older, redder galaxies should have considerably more mass and a larger number of stars than we currently observe. It seems that the galactic winds or outflow of gas are so strong that they deprive the galaxy of the fuel for the formation of the next generation of stars.
The researchers determined that vast quantities of molecular gas — nearly ten times the mass of our Sun each year and possibly much more — were being ejected from the galaxy at velocities between 150,000 and almost 1,000,000 kilometres per hour. The total amount of gas ejected would add up to more gas than actually went into forming the galaxy’s stars in the same time. At this rate, the galaxy could run out of gas in as few as 60 million years.
Image credit: ALMA (ESO/NAOJ/NRAO)/Erik Rosolowsky