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Super Star Clusters in Dust-Enshrouded Galaxy
The sharp eye of the Hubble Space Telescope's Advanced Camera for Surveys has uncovered more than 200 mammoth star clusters in the heart of the galaxy Arp 220.
The clusters are the bluish-white dots scattered throughout the image. The heftiest Arp 220 cluster - about 10 million solar masses - is twice as massive as any comparable star cluster in the Milky Way Galaxy. Arp 220 collided with another galaxy about 700 million years ago, fueling the frenzy of star birth in a small region about 5,000 light-years across. The galaxy is a nearby example of the aftermath of two colliding galaxies.
The clusters are so compact, however, that even at their moderate distance they look to Hubble like brilliant single stars. Astronomers know the clusters are not stars because they are much brighter than a star would be at that distance, 250 million light-years away in the constellation Serpens.
The massive clusters seen in this visible-light image are just the tip of the iceberg. More star clusters are not visible because they are obscured by the dust that engulfs this galaxy. In fact, much of the visible light in this photo is reddened by dust, like Earth's sky at sunset. Because of this dust, Arp 220 shines brightest in infrared light and is called an ultra-luminous infrared galaxy (ULIRG). ULIRGs are the products of mergers between galaxies, which can create firestorms of star birth. Starlight from the new stars heats the surrounding dust, causing the galaxies to glow brilliantly in infrared light.
The Advanced Camera observations were taken in visible light in August 2002.
About the Object
- R.A. PositionR.A. PositionRight ascension – analogous to longitude – is one component of an object's position.15h 34m 57s.21
- Dec. PositionDec. PositionDeclination – analogous to latitude – is one component of an object's position.+23° 30' 9".5
- ConstellationConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.Serpens
- DistanceDistanceThe 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.250 million light-years (77 Megaparsecs)
- DimensionsDimensionsThe physical size of the object or the apparent angle it subtends on the sky.Roughly 24 arcseconds (29,000 light-years or 8,900 parsecs) wide
About the Data
- Data DescriptionData DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.This image was created from HST data from proposal 9396: C. Wilson, S. Brooks, and W. Harris (McMaster University), and N. Scoville (California Institute of Technology). - InstrumentInstrumentThe science instrument used to produce the data.HST>ACS/HRC
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.August 11, 2002, Exposure Time: 6.6 hours
- FiltersFiltersThe camera filters that were used in the science observations.F435W (B), F555W (V), F814W (I)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.Arp 220
- Object DescriptionObject DescriptionThe type of astronomical object.Active Galaxy
- Release DateJune 13, 2006
- Science ReleaseHubble Eyes Star Birth in the Extreme
- Credit
This image is a composite of many separate exposures made by the ACS instrument on the Hubble Space Telescope using several different filters. Three filters were used to sample broad wavelength ranges. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: Blue: F435W (B) Green: F555W (V) Red: F814W (I)
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Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
