National Aeronautics and Space Administration’s (NASA) hubble space telescope captured two dramatically different face-on views of the spiral galaxy Messier 51 or M51, dubbed the Whirlpool Galaxy.
Researchers constructed the image by combining visible-light exposures from Jan. 18 to 22, 2005, with the Advanced Camera for Surveys (ACS), and pictures taken in December 2005 with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).
The Whirlpool Galaxy is located at a distance of about 30 million light-years from the Milky Way Galaxy in the constellation Canes Venatici, which is one of the 88 official modern constellations. A constellation is an internationally defined area of the celestial sphere.
M51, whose name comes from being the 51st entry in Charles Messier's catalog, is considered to be one of the classic examples of a spiral galaxy. It is also one of the brightest spirals in the night sky.
The image attributed as ACS in the 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 have 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.
However, the near-infrared view revealed more starlight as near-infrared light penetrates dust. Then the researchers subtracted the total amount of starlight from both images to see the galaxy's dust structure.
In the near-infrared image, the red color traces the dust that 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 as 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.
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope and the Space Telescope Science Institute conducts Hubble science operations.