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).
Credits
NICMOS Image: NASA, ESA, M. Regan and B. Whitmore (STScI), and R. Chandar (University of Toledo);ACS Image: NASA, ESA, S. Beckwith (STScI), and the Hubble Heritage Team (STScI/AURA)
| About The Object | |
|---|---|
| Object Name | M51, Whirlpool Galaxy |
| Object Description | Face-on Spiral Galaxy |
| R.A. Position | 13h 29m 55.73s |
| Dec. Position | 47° 13' 53.43" |
| Constellation | Canes Venatici |
| Distance | About 31 million light-years (9.6 million parsecs) |
| Dimensions | This image is 3 arcminutes (20,000 light-years or 6,000 parsecs) wide. |
| About The Data | |
| Data Description | The Hubble optical image was created from HST data from proposal : 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). |
| Instrument | HST>ACS/WFC (left), HST>NICMOS and HST>ACS/WFC (right) |
| Exposure Dates | January 18-22, 2005, Exposure Time: 9 hours (left), November 28 - December 2, 2005, Exposure Time: 9 hours (right) |
| Filters | F435W (B), F555W (V), F658N (Halpha + [N II]), F814W (I) |
| About The Image | |
| Color Info | 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. |
| 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. |
