These four dwarf galaxies waited billions of years to come together, setting off a fireworks show as thousands of new star clusters come to life. The distorted galaxies are quickly producing massive, hot, young stars that are pumping out ultraviolet radiation, heating up surrounding gas clouds, and causing them to glow.
Such encounters between dwarf galaxies are normally seen billions of light-years away and therefore occurred billions of years ago. But these galaxies, members of Hickson Compact Group 31, are relatively nearby, only 166 million light-years away.
In this composite image of the galaxy grouping, the bright, distorted object at middle, left, is actually two colliding dwarf galaxies. Myriad star clusters have formed in the streamers of debris pulled from the galaxies and at the site of their head-on collision. The cigar-shaped object above the galaxy duo is another member of the group. A bridge of star clusters connects the trio. A long rope of bright star clusters points to the fourth member of the group, at lower right. The bright object in the center is a foreground star. The image was composed from observations made by the Hubble Space Telescope's Advanced Camera for Surveys, NASA's Spitzer Space Telescope, and the Galaxy Evolution Explorer (GALEX).
Astronomers used Hubble's Advanced Camera for Surveys to resolve the youngest and brightest of star clusters, which allowed them to calculate the clusters' ages, map the star-formation history, and determine that the galaxies are starting the final stages of galaxy assembly. Hubble reveals that the brightest clusters, hefty groups each holding at least 100,000 stars, are less than 10 million years old.
Astronomers say the interacting galaxies will form a large elliptical galaxy in another billion years.
The Advanced Camera for Surveys data were taken on Aug. 8, 2006. The principal investigator was Jane Charlton of Pennsylvania State University, University Park.
The Spitzer observations were made on Feb. 22, 2005. The principal investigator was Kelsey Johnson of the University of Virginia and the National Radio Astronomy Observatory, both in Charlottesville.
The GALEX data were taken on Dec. 27, 2004.
Credits
NASA, ESA, S. Gallagher (The University of Western Ontario), and J. English (University of Manitoba)| About The Object | |
|---|---|
| Object Name | Hickson Compact Group 31, HCG 31 |
| Object Description | Galaxy Group |
| R.A. Position | 05h 1m 38.74s |
| Dec. Position | -4° 15' 34.1" |
| Constellation | Eridanus |
| Distance | 166 million light-years (51 million parsecs) |
| Dimensions | This image is 3.2 arcminutes (156,000 light-years or 48,000 parsecs) wide. |
| About The Data | |
| Data Description | This image was created from HST data from proposal : J. Charlton (Pennsylvania State University), A. Zabludoff (University of Arizona), M. de Oliveira (University of São Paulo, Brazil), J. Hibbard (AURA/NRAO), S. Zonak (University of Maryland), A. Hornschemeier (NASA/GSFC), P. Hickson (University of British Columbia), J. Mulchaey (Carnegie Institution of Washington), K. Johnson (University of Virginia), A. Maybhate (STScI), R. Chandar (University of Toledo), S. Gallagher (The University of Western Ontario), C. Palma, S. Hunsberger, N. Brandt, and M. Eracleous (Pennsylvania State University), P. Durrell (Youngstown State University), J. English (University of Manitoba), B. Whitmore (STScI), D. Elmegreen (Vassar College), and K. Knierman (Arizona State University). The science team comprises: S. Gallagher (The University of Western Ontario), P. Durrell (Youngstown State University), D. Elmegreen (Vassar College), R. Chandar (University of Toledo), J. English (University of Manitoba), J. Charlton, C. Gronwall, and J. Young (Pennsylvania State University), P. Tzanavaris (NASA/GSFC), K. Johnson (University of Virginia/NRAO), M. de Oliveira (University of São Paulo, Brazil), B. Whitmore (STScI), A. Hornschemeier (NASA/GSFC), et al. |
| Instrument | HST>ACS/WFC, HST>WFPC2, Spitzer>IRAC, and GALEX |
| Exposure Dates | August 8, 2006, Exposure Time: 1.1 hours (HST), February 22, 2005 (Spitzer), and December 27, 2004 (GALEX) |
| Filters | HST>ACS: F435W (B), F606W (V), and F814W (I) HST>WFPC2: F439W (B), F555W (V), F675W (R), and F814W (I) Spitzer>IRAC: 8 micron GALEX: NUV Imaging Channel |
| About The Image | |
| Color Info | Note: Spitzer and GALEX data were combined with the Hubble data to create the composite image. The Spitzer data were taken February 22, 2005 (PI: K. Johnson, University of Virginia/NRAO). The GALEX data were taken December 27, 2004 (archival data). A small amount of WFPC2 data (proposal 5900, PI: P. Conti) taken on October 7, 1995, was used to fill in a portion of the ACS/WFC chip gap in this composite image of HCG 31. This image is a composite of separate exposures acquired by three separate space telescopes. Exposures in the optical range of the spectrum were acquired with ACS and WFPC2 instruments on the Hubble Space Telescope (HST). The near-ultraviolet light was acquired by the Galaxy Evolution Explorer (GALEX), while near-infrared emission was captured by the IRAC instrument on the Spitzer Space Telescope (SST). Several filters were used to sample these wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are: Red: ACS F814W (I) + WFPC2 F814W (I) Yellow/green: ACS F606W (V) + WFPC2 F555W (V) + WFPC2 F675W (R) Blue: ACS F435W (B) + WFPC2 F439W (B) Orange: IRAC 8 micron Purple: GALEX NUV Imaging Channel |
| Compass Image |  |
| About The Object | |
|---|---|
| Object Name | A name or catalog number that astronomers use to identify an astronomical object. |
| Object Description | The type of astronomical object. |
| R.A. Position | Right ascension – analogous to longitude – is one component of an object's position. |
| Dec. Position | Declination – analogous to latitude – is one component of an object's position. |
| Constellation | One of 88 recognized regions of the celestial sphere in which the object appears. |
| Distance | The physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs. |
| Dimensions | The physical size of the object or the apparent angle it subtends on the sky. |
| About The Data | |
| Data Description |
|
| Instrument | The science instrument used to produce the data. |
| Exposure Dates | The date(s) that the telescope made its observations and the total exposure time. |
| Filters | The camera filters that were used in the science observations. |
| About The Image | |
| Image Credit | The primary individuals and institutions responsible for the content. |
| Publication Date | The date and time the release content became public. |
| Color Info | A brief description of the methods used to convert telescope data into the color image being presented. |
| Orientation | The rotation of the image on the sky with respect to the north pole of the celestial sphere. |
