The
AKARI spacecraft made new observations of galaxy M101, revealing differing
populations of stars spread across its spiral arms. This composite image shows M101,
a spiral galaxy 170 thousand light years in diameter.
AKARI
observed the galaxy at four infrared wavelengths (65, 90, 140, and 160 micrometers)
using the Far-Infrared Surveyor (FIS) instrument. The image displays cold
(blue) and warm (red) dust overlaid on the visible (green, showing distribution
of stars) and far-ultraviolet (cyan, indicating the location of young stars)
images of M101.
Many
young high-temperature stars populate the spiral arms, revealing the areas of
star formation and warming the interstellar dust. This makes the galaxy shine
at shorter infrared wavelengths. In contrast, the longer wavelengths show the "cold"
dust. Normal stars, typically like our own Sun, warm this dust.
When
researchers compared FIS data to an image of the galaxy in the visible and
far-ultraviolet, it showed that the warm dust is distributed along the spiral
arms, with many hot spots located along the outer edge of the galaxy. These
spots correspond to giant star-forming regions. This is considered unusual
because star formation is generally more active in the central parts of spiral
galaxies.
This
new information suggests M101 experienced a close encounter with a companion
galaxy in the past, dragging out gas from its companion. The gas now falls onto
the outer edge of M101 at approximately 93 miles/sec (150 km/s), triggering active
star formation.
--ESA and SPACE.com Staff
Credit: Composite: JAXA, visible
(green): the National Geographic Society, far-ultraviolet (cyan): GALEX/NASA
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