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Although not yet complete, the world's most sensitive astronomical radio telescope ALMA (Atacama Large Millimeter/sub-millimeter Array) took a remarkable first photograph. The image released by the National Radio Astronomy Observatory (NRAO) to celebrate the launch of the new facility shows in sensational detail the violet collision between two galaxies.

The image is of NGC 4038 and 4039, two faint 11th magnitude galaxies also known as the Antennae Galaxies, in the constellation of Corvus. They are a pair of distorted spiral galaxies between 45 and 65 million light-years distant. It is predicted that within the next 400 million years the nuclei of the two galaxies will join together to become a single core. Eventually, observations and computer modeling suggest that the Antennae Galaxies will settle into one giant elliptical galaxy.

While visible light shows us the stars in the galaxies, ALMA's view reveals something that cannot be seen in visible light: the clouds of dense cold gas from which new stars form. This is the best submillimeter-wavelength image ever made of the Antennae Galaxies.

Multiwavelength composite of interacting galaxies NGC 4038/4039, the Antennae, showing their namesake tidal tails in radio (blues), past and recent starbirths in optical (whites and pinks), and a selection of current star-forming regions in mm/submm (orange and yellows). Inset: ALMA's first mm/submm test views, in Bands 3 (orange), 6 (amber) and 7 (yellow), showing detail surpassing all other views in these wavelengths. Credit: (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); HST (NASA, ESA, and B. Whitmore (STScI)); J. Hibbard, (NRAO/AUI/NSF); NOAO/AURA/NSF.

Considering the project is not yet completed the initial image is astonishing and only a taste of what's to come. ALMA Director Thijs de Graauw said "We are living in a historic moment for science and particularly for astronomy, and perhaps also for the evolution of humanity, because we start to use the greatest observatory under construction at the moment"

Once construction is finished, the final array will consist of 66 12-meter and 7-meter diameter radio telescopes on the 5000 metres altitude Chajnantor plateau in Chile's Atacama Desert. With a total cost of more than a billion US dollars, it is the most expensive ground-based telescope to date and is scheduled to be fully operational by the end of 2012.

The Antennae Galaxies (NGC 4038 and 4039) finder chart

The Antennae Galaxies are not the brightest galaxies when viewed from Earth but are easily within the range of medium size amateur telescopes. They are visible in apertures as small as 100mm (4-inch) with the best views reserved for instruments 150mm (6-inch) and larger. Through a 150mm telescope, the galaxies hint at their unusual nature and more and more intriguing details are visible through larger scopes.

The chart below pinpoints the position of the galaxies in Corvus.

Antennae Galaxies (NGC 4038/4039) finder chart

Antennae Galaxies (NGC 4038/4039) finder chart - pdf format

Antennae Galaxies Data Table

NameNGC 4038NGC 4039
Other designationCaldwell 60Caldwell 61
Constellation CorvusCorvus
RA (J2000)12h 01m 53.0s 12h 01m 53.6s
DEC (J2000)-18d 52m 10s-18d 53m 11s
Distance (light-years)45 to 65 Million45 to 65 Million
Apparent size (arc mins)5.2 x 3.13.1 x 1.6
Apparent magnitude11.211.1