ALMA pinpoints early galaxies at record speed

ALMA pinpoints early galaxies at record speed

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Imagine a meadow with a few hundred chirping crickets. You can only hear them if your ears are really good – they need to be sensitive enough to pick up the soft sound. But even then, it’s hard to know exactly where the crickets are: your ears are not so good in resolving their precise locations.

In space it’s more or less the same. Some distant galaxies are so faint that you need very good sensitivity to pick up their light at all. And even then, you need very good resolution to know exactly where they are.

Normal telescopes have pretty good resolution, meaning they are able to see fine detail. But most telescopes that measure millimetre and submillimeter waves from space don’t have this eagle-eyed vision. And you need those telescopes to find distant, dusty galaxies where many new stars are being born.

ALMA is changing all that. Even with less than a quarter of the final 66 antennas in place, the new observatory is much more sensitive than earlier millimetre and submillimeter telescopes. ALMA also has a much higher resolution. As a result, it can detect and pinpoint distant starburst galaxies at a very high rate.

Using ALMA, astronomers have now detected and pinpointed over a hundred distant starburst galaxies in just a few hours. Thanks to its super-sharp vision, ALMA also discovered that some starburst galaxies are really two or three galaxies close together.

The light from the distant galaxies has taken billions of years to reach Earth. So when astronomers look at these distant galaxies, they see them as they appeared billions of years ago, when the Universe was still young. That means that the new ALMA observations reveal a lot about star formation in the early days of the Universe.


ALMA observed very distant galaxies in a region of space known as the Chandra Deep Field Sound. This region, in the southern constellation Fornax (the Furnace) has also been studied in much detail by other telescopes. Thus, astronomers can compare the new ALMA measurements to other observations, for instance at optical, infrared and X-ray wavelengths.


The distant starburst galaxies haven been carried out by a very big international group of astronomers, led by Jacqueline Hodge of the Max-Planck-Institute for Astronomy in Germany and Alexander Karim and Ian Smail of Durham University in the United Kingdom. Jaqueline, Alexander, Ian and their colleagues wrote two articles about the new results. They were published in The Astrophysical Journal and in a journal known as the Monthly Notices of the Royal Astronomical Society.