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The Two-faced Whirlpool Galaxy
These images by NASA's Hubble Space Telescope show off two dramatically different face-on views of the spiral galaxy M51, dubbed the Whirlpool Galaxy.
The image at left, taken in visible light, highlights the attributes of a typical spiral galaxy, including graceful, curving arms, pink star-forming regions, and brilliant blue strands of star clusters.
In the image at right, most of the starlight has been removed, revealing the Whirlpool's skeletal dust structure, as seen in near-infrared light. This new image is the sharpest view of the dense dust in M51. The narrow lanes of dust revealed by Hubble reflect the galaxy's moniker, the Whirlpool Galaxy, as if they were swirling toward the galaxy's core.
To map the galaxy's dust structure, researchers collected the galaxy's starlight by combining images taken in visible and near-infrared light. The visible-light image captured only some of the light; the rest was obscured by dust. The near-infrared view, however, revealed more starlight because near-infrared light penetrates dust. The researchers then subtracted the total amount of starlight from both images to see the galaxy's dust structure.
The red color in the near-infrared image traces the dust, which is punctuated by hundreds of tiny clumps of stars, each about 65 light-years wide. These stars have never been seen before. The star clusters cannot be seen in visible light because dense dust enshrouds them. The image reveals details as small as 35 light-years across.
Astronomers expected to see large dust clouds, ranging from about 100 light-years to more than 300 light-years wide. Instead, most of the dust is tied up in smooth and diffuse dust lanes. An encounter with another galaxy may have prevented giant clouds from forming.
Probing a galaxy's dust structure serves as an important diagnostic tool for astronomers, providing invaluable information on how the gas and dust collapse to form stars. Although Hubble is providing incisive views of the internal structure of galaxies such as M51, the planned James Webb Space Telescope (JWST) is expected to produce even crisper images.
Researchers constructed the image by combining visible-light exposures from Jan. 18 to 22, 2005, with the Advanced Camera for Surveys (ACS) and near-infrared-light pictures taken in December 2005 with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).
About the Object
- R.A. PositionR.A. PositionRight ascension – analogous to longitude – is one component of an object's position.13h 29m 55.73s
- Dec. PositionDec. PositionDeclination – analogous to latitude – is one component of an object's position.47° 13' 53.43"
- ConstellationConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.Canes Venatici
- 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.About 31 million light-years (9.6 million parsecs)
- DimensionsDimensionsThe physical size of the object or the apparent angle it subtends on the sky.This image is 3 arcminutes (20,000 light-years or 6,000 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.The Hubble optical image was created from HST data from proposal 10452 : S. Beckwith (STScI), R. Kennicutt, Jr. (University of Cambridge), and H. Bond, C. Christian, L. Frattare, F. Hamilton, Z. Levay, M. Mutchler, K. Noll, and T. Royle (Hubble Heritage Team, STScI/AURA). NICMOS observations were made with the HST proposal 10501: R. Chandar (University of Toledo), D. Calzetti (University of Massachusetts), R. Kennicutt, Jr. (University of Cambridge), M. Regan and B. Whitmore (STScI), and E. Schinnerer (Max Planck Institute for Astronomy, Heidelberg).
- InstrumentInstrumentThe science instrument used to produce the data.HST>ACS/WFC (left), HST>NICMOS and HST>ACS/WFC (right)
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.January 18-22, 2005, Exposure Time: 9 hours (left), November 28 - December 2, 2005, Exposure Time: 9 hours (right)
- FiltersFiltersThe camera filters that were used in the science observations.F435W (B), F555W (V), F658N (Halpha + [N II]), F814W (I)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.M51, Whirlpool Galaxy
- Object DescriptionObject DescriptionThe type of astronomical object.Face-on Spiral Galaxy
- Release DateJanuary 13, 2011
- Science ReleaseThe Two-faced Whirlpool Galaxy
- Credit
This image is a composite of many separate exposures made by the ACS instrument on the Hubble Space Telescope. 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: F658N (Halpha + [N II]) + F814W (I) This image, which was obtained by aligning data from both the NICMOS and ACS detectors and dividing the NICMOS brightness values by the ACS values, was originally black and white. These brightness values were translated into a range of reddish hues. Such color "maps" can be useful in helping to distinguish subtly varying brightness in an image.
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Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
