Three images from NASA’s Spitzer Space Telescope show pairs of galaxies on the cusp of cosmic consolidations.

Though the galaxies appear separate now, gravity is pulling them together, and soon they will combine to form new, merged galaxies. Some merged galaxies will experience billions of years of growth. For others, however, the merger will kick off processes that eventually halt star formation, dooming the galaxies to wither prematurely.

Only a few percent of galaxies in the nearby universe are merging, but galaxy mergers were more common between 6 billion and 10 billion years ago, and these processes profoundly shaped our modern galactic landscape. For more than 10 years, scientists working on the Great Observatories All-sky LIRG Survey, or GOALS, have been using nearby galaxies to study the details of galaxy mergers and to use them as local laboratories for that earlier period in the universe’s history. The survey has focused on 200 nearby objects, including many galaxies in various stages of merging. The images above show three of those targets, imaged by Spitzer.

In these images, different colors correspond to different wavelengths of infrared light, which are not visible to the human eye. Blue corresponds to 3.6 microns, and green corresponds to 4.5 microns — both strongly emitted by stars. Red corresponds to 8.0 microns, a wavelength mostly emitted by dust.

Merging galaxies in the nearby universe appear especially bright to infrared observatories like Spitzer. GOALS studies have also relied on observations of the target galaxies by other space-based observatories, including NASA’s Hubble and Chandra space telescopes, the European Space Agency’s Herschel satellite, as well as facilities on the ground, including the Keck Observatory, the National Science Foundation’s Very Large Array and the Atacama Large Millimeter Array.

JPL manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space in Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech.



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