A Galactic Spectacle

NGC 4038/4039 - Antennae Galaxies

Credit: NASA, ESA, SAO, CXC, JPL-Caltech, and STScI

Acknowledgment: G. Fabbiano and Z. Wang (Harvard-Smithsonian CfA),

and B. Whitmore (STScI)

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A beautiful new image of two colliding galaxies has been released by NASA's Great Observatories. The Antennae galaxies, located about 62 million light-years from Earth, are shown in this composite image from the Chandra X-ray Observatory (blue), the Hubble Space Telescope (gold and brown), and the Spitzer Space Telescope (red). The Antennae galaxies take their name from the long antenna-like "arms," seen in wide-angle views of the system. These features were produced by tidal forces generated in the collision.

The collision, which began more than 100 million years ago and is still occurring, has triggered the formation of millions of stars in clouds of dusts and gas in the galaxies. The most massive of these young stars have already sped through their evolution in a few million years and exploded as supernovas.

The X-ray image from Chandra shows huge clouds of hot, interstellar gas that have been injected with rich deposits of elements from supernova explosions. This enriched gas, which includes elements such as oxygen, iron, magnesium, and silicon, will be incorporated into new generations of stars and planets. The bright, point-like sources in the image are produced by material falling onto black holes and neutron stars that are remnants of the massive stars. Some of these black holes may have masses that are almost one hundred times that of the Sun.

The Spitzer data show infrared light from warm dust clouds that have been heated by newborn stars, with the brightest clouds lying in the overlapping region between the two galaxies.

The Hubble data reveal old stars and star-forming regions in gold and white, while filaments of dust appear in brown. Many of the fainter objects in the optical image are clusters containing thousands of stars.

The Chandra image was taken in December 1999. The Spitzer image was taken in December 2003. The Hubble image was taken in July 2004, and February 2005.

For additional information, contact:

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-4673
whitney.clavin@jpl.nasa.gov

Cheryl Gundy
Space Telescope Science Institute, Baltimore, Md.
410-338-4707
gundy@stsci.edu

Antennae Galaxies move closer

Credit: NASA, ESA, and the Hubble Heritage Team
(STScI/AURA)-ESA/Hubble Collaboration

Merging system's interaction sets standard for galaxy evolution.
Provided by European Space Agency

The Antennae Galaxies are among the closest known merging systems. Also known as NGC 4038 and NGC 4039, the two began interacting a few hundred million years ago, creating one of the most impressive sights in the night sky. They are used by scientists as a standard against which to validate theories of galactic evolution.

An international group of scientists led by Ivo Saviane from the European Southern Observatory used Hubble's Advanced Camera for Surveys and Wide Field Planetary Camera 2 to observe individual stars spawned by the colossal cosmic collision in the Antennae Galaxies. By measuring the colors and brightnesses of red giant stars in the system, the scientists found that the Antennae are much closer than previously thought: 45 million light-years instead of the previous best estimate of 65 million light-years.

The team targeted a region in the relatively quiescent outer regions in the southern tidal tail, away from the active central regions. This tail consists of material thrown from the main galaxies as they collided. The scientists needed to observe regions with older red giant stars to derive an accurate distance. Red giants are known to reach a standard brightness, which can then be used to infer their distance.

The previous distance to the Antennae Galaxy was about 65 million light-years, although values as high as 100 million light years have been used. Our Sun is only 8 light-minutes away from us, so the Antennae Galaxies may seem rather distant. But if we consider that we already know of galaxies more than 10 billion light-years away, the two galaxies are really our neighbors.

The new, smaller distance makes the Antennae Galaxies less extreme in terms of the physics needed to explain the observed phenomena. For instance, its infrared radiation is now that expected of a standard early merging event rather than that of an ultraluminous infrared galaxy. The size of the star clusters formed as a consequence of the Antennae merger now agree with those of clusters created in other mergers instead of being 1.5 times as large.

The Antennae Galaxies are named for the two long tails of stars, gas and dust that resemble the antennae of an insect. These "antennae" are a physical result of the collision between the two galaxies. Studying their properties gives us a preview of what may happen when our Milky Way Galaxy collides with the neighboring Andromeda galaxy in several billion years.

Astronomy.com

Fire Within the Antennae Galaxies - Courtesy Nasa/JPL - Caltech/Z

Interacting Antennae Galaxies

Credit: NASA/JPL-Caltech/Z.Wang (Harvard-Smithsonian CfA)

This false-color image from NASA's Spitzer Space Telescope reveals hidden populations of newborn stars at the heart of the colliding "Antennae" galaxies. These two galaxies, known individually as NGC 4038 and 4039, are located around 68 million light-years away and have been merging together for about the last 800 million years. The latest Spitzer observations provide a snapshot of the tremendous burst of star formation triggered in the process of this collision, particularly at the site where the two galaxies overlap.