Seeing stars and a lot more: Photos of nearby galaxy open new era of discovery

05/28/04



The Spitzer telescope is being used to study how galaxies build up, destroy and recycle the building blocks of stars and planets.

Full size image available here

MINNEAPOLIS / ST. PAUL--Like nosy neighbors, astronomers are spying on one of the nearest galaxies to our Milky Way in search of clues to how our own galaxy and others are born, live and die. Known by its catalog listing, M33, this neighboring galaxy is in the northern sky not too far from the famous Andromeda galaxy. Using infrared pictures from NASA's Spitzer Space Telescope, astronomers from the University of Minnesota, the Harvard-Smithsonian Center for Astrophysics (CfA) and the University of Arizona have seen features of the galaxy never before visible. Elisha Polomski, a postdoctoral fellow at the University of Minnesota, will present the pictures at 9:30 a.m. MDT Tuesday, June 1, in the Colorado Convention Center during a meeting of the American Astronomical Society.

The work is the first in a planned series of observations of M33, a galaxy three million light-years from the Milky Way. About 50,000 light-years across, M33 is half the diameter of the Milky Way. (Its name is derived from its shape: the Pinwheel Galaxy.) Although smaller and dimmer than its more famous cousin, M33 faces Earth more squarely, so more of its activity is visible. Andromeda, M33 and the Milky Way are the "Big Three" of what astronomers call the Local Group of about 35 galaxies.



This three-color image of the Pinwheel Galaxy, a close neighbor of the Milky Way, was made with the new NASA Spitzer Space Telescope by astronomers at the University of Minnesota, the Harvard-Smithsonian Center for Astrophysics and the University of Arizona.

Full size image available here

"M33 is a gigantic laboratory where you can watch dust being created in [exploding stars called] novae and supernovae, being distributed in the winds of giant stars and being reborn in new stars," said Polomski. "You can see the universe in a nutshell."

Because it operates at infrared wavelengths, the Spitzer Space Telescope detects details hidden to the human eye and to telescopes that operate in visible light. For example, the moon is relatively cool and does not show up in visible light unless illuminated by the sun or reflections from Earth. But even cold objects emit long-wavelength infrared light, and an infrared camera can detect them as long as they are warmer than their surroundings. The Spitzer Telescope detects light at wavelengths measured in microns--millionths of a meter. The Minnesota-Smithsonian-Arizona team is observing M33 at wavelengths ranging from 10 to 30 times longer than visible light, giving them a window on objects that are much colder than stars. The new pictures were taken in light at wavelengths ranging from 3.5 to 24 microns.

"At 3.5 microns we see stars," said University of Minnesota astronomy professor Robert Gehrz, leader of the M33 observation team. "At eight, we see warm dust that's about 100 degrees Fahrenheit. At 24 microns we're picking up cool dust that's between minus 100 and minus 190 degrees Fahrenheit." Spitzer cameras also operate at 70 and 160 microns--wavelengths that can't penetrate Earth's atmosphere. The ability to detect those wavelengths allows Spitzer to "see" objects invisible to ground-based telescopes.

Observations of M33's cool components are expected to reveal much about the "metabolism" of galaxies. A galaxy is akin to a living body, in which food substances are broken down to build the body, and the waste and decomposition products of a body are recycled to feed new life. For example, the iron in Earth's core was forged in the bellies of large, luminous stars, and the heavier elements--all the way to uranium, the heaviest naturally occurring element--were created in supernova explosions. The deaths of those stars sprayed interstellar space with dust and gas, some of which clumped together in a disk that coalesced to form the sun and its planets.

Along with Steven Willner and Pauline Barmby of CfA and George Rieke, Joannah Hinz and Karl Gordon of the University of Arizona, Polomski and Gehrz will examine the M33 galaxy in detail for the next two-and-a-half years, studying the processes that circulate energy and chemical elements through the galaxy to build up, destroy and recycle the building blocks of stars and planets. The researchers expect to identify new star-forming regions, red giant stars, novae and supernovae, mapping out the evolutionary process of the birth, old age and death of stars in M33 and comparing it to the process in our own galaxy. The team has assembled thousands of images from the telescope and is now planning follow-up studies of objects in M33. They plan further study of four objects: the remnant of a supernova explosion, two star-forming regions and a mysterious dust-shrouded object visible at the long wavelengths only Spitzer can see.

Source: Eurekalert & others

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