UA Camera Helps Capture Spitzer Image That Celebrates IYA2009

Galaxy M33

This new portrait of Galaxy M33 was taken by two cameras on NASA's Spitzer Space Telescope, the MIPS built by astronomers at UA's Steward Observatory and Spitzer's Infrared Array Camera. (NASA/JPL-Caltech/Spitzer Space Telescope/UA)

The new portrait of famous Galaxy M33 was taken with infrared light.

By Lori Stiles, University Communications April 3, 2009

University of Arizona astronomers' Multiband Imaging Photometer helped capture a new image of an iconic galaxy, M33, which NASA Spitzer Space Telescope scientists released today in celebration of the International Year of Astronomy, or IYA2009.

UA Regents' Professor of Astronomy George Rieke is principal investigator for the Multiband Imaging Photometer, or "MIPS," a far-infrared camera that gives the Spitzer telescope is ability to see very cold dust. Rieke and his group developed the first large format array of far-infrared detectors at Steward Observatory.

The new M33 galaxy image combines light from MIPS and Spitzer's Infrared Array Camera. It is the best image of M33 ever taken at infrared wavelengths, said MIPS team member Joannah Hinz of the UA's Steward Observatory.

M33, also known as the Triangulum Galaxy, is a member of what's known as our Local Group of galaxies. Along with our own Milky Way, this group travels together in the universe, as they are gravitationally bound.

M33 is one of the few galaxies that is moving toward the Milky Way despite the fact that space itself is expanding, causing most galaxies in the universe to grow farther and farther apart.

When viewed with Spitzer's infrared eyes, this elegant spiral galaxy sparkles with color and detail. Stars appear as glistening blue gems, several of which are actually foreground stars in our own galaxy, while dust rich in organic molecules glows green.

The diffuse orange-red glowing areas indicate star-forming regions, while small red flecks outside the spiral disk of M33 are most likely distant background galaxies.

This new image shows M33 to be surprising large - bigger than its visible-light appearance would suggest. With its ability to detect cold, dark dust, Spitzer can see emission from cooler material well beyond the visible range of M33's disk. Exactly how this cold material moved outward from the galaxy is still a mystery, but winds from giant stars or supernovas may be responsible.

M33 is located about 2.9 million light-years away in the constellation Triangulum.

The last time M33 had a good infrared portrait taken from space was by ISO, a European space satellite, in 2003 – the year Spitzer was launched into space, Hinz said. The European satellite didn't have the sensitivity or resolution that Spitzer does, she added.

"We knew that looking at M33 would be important for Spitzer," Hinz said. "It's a face-on galaxy, and one our nearest galaxies."

The MIPS instrument studies dust in nearby galaxies and is able to resolve different temperatures of dust, which tells astronomers about the physical dynamics of galaxies.

"By looking at the remnants of colder dust we can tell what happened in a star's lifetime," Hinz said. "We've discovered there's a much bigger component of cold dust to galaxies that we ever thought."