The Atacama Large Millimeter/submillimeter Array (ALMA) is the world’s biggest and most complex astronomical instrument. Located at the European Southern Observatory on the Chajnantor plateau in northern Chile, the array of antennae is now operational even though it is still incomplete. Here is its first image to be released to the public.

Image of Antennae Galaxies

When Galaxies Collide (Image credit: ALMA (ESO/NAOJ/NRAO). Visible light image: the NASA/ESA Hubble Space Telescope)


In the southern sky constellation of Corvus (the Crow), we see the Antennae Galaxies (alias NGC 4038 and 4039). These are a pair of colliding spiral galaxies about 70 million light years (21.5 Mpc) away. This view is a combination of observations; it uses images made in two different millimetre and submillimetre wavelength ranges from just twelve of the antennae of the ALMA observatory with visible light observations from the Hubble Space Telescope (HST). Galactic collisions like this trigger the birth of new stars as gas clouds billions of times the mass of the Sun slam together.

This gorgeous picture is just a foretaste of the visions to come. ALMA observes at wavelengths much longer than those of visible light which currently makes it impossible to make images as sharp as those from the HST images.  However, as the ALMA observatory grows, the quality of its observations will improve dramatically as the array grows in size and more antennas are added. When the full ALMA array is completed its much larger aperture will give it vision ten times sharper than Hubble’s. ALMA will reveal parts of the Universe that cannot be seen with visible-light and infrared telescopes.


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