Birthing place of stars captured in recent Spitzer Space Telescope imagery
During its 15 years of infrared observations, NASA’s Spitzer Space Telescope has provided scientists unprecedented insight into the process of star-formation and the stellar nurseries in which new stars are born.
Star formation occurs in thick clouds of gas and dust known as nebulae, which visible light cannot penetrate. Infrared light can see through these clouds, which is why Spitzer has been so useful in revealing their secrets.
Two of Spitzer‘s instruments, the Infrared Array Camera (IRAC) and the Multiband Imaging Photometer (MIPS), have been used in concert to form some of the most colorful pictures of these previously-hidden regions. An imaging camera that observes in infrared and near-infrared wavelengths, IRAC is a four-channel camera that is highly sensitive to a wide range of light wavelengths. MIPS observes in the far-infrared, which allows it to view and image reddish features in nebulae produced when dust is heated by both hot gas and the light of other stars in the region.
Combining images taken by IRAC and MIPS, Spitzer recently produced two stunning photographs of the Cat’s Paw Nebula, a star-forming region between 4,200 and 5,500 light years from Earth in the constellation Scorpius, so named because it is composed of several round red bubbles that make it resemble a cat’s paw.
Both images were taken by the Galactic Legacy Mid-Plane Survey Extraordinaire (GLIMPSE), a Spitzer project that produced the most accurate ever map of the Milky Way’s central bar. One of GLIMPSE‘s findings is that the entire galaxy is filled with gas bubbles like the ones that make up the Cat’s Paw Nebula.
Clearly visible in the first image are bright red bubbles surrounded by green regions, whose color is the result of a collision between radiation produced by hot stars and large molecules known as “polycyclic aromatic hydrocarbons.”
Newborn stars are produced by the collapse of gas and dust within star-forming nebulae. After these stars form, they heat up the nebular gas surrounding them, causing the gas to expand and form bubbles. Some of these bubbles eventually burst, producing U-shaped formations like the one in the pink region of the second image, taken by IRAC. Within that image, a dense region of gas and dust is visible as a dark filament cutting through the center.
Dark filaments like the one in this image are so thick with gas and dust that even infrared light cannot pass through them.
Neither Spitzer image shows the entirety of the Cat’s Paw Nebula, which scientists estimate extends between 80 and 90 light years, bordering another, similar-sized star-forming region to the left of the photos known as the Lobster Nebula or NGC 6357.
While the first image combines those taken by both IRAC and MIPS, the second uses only IRAC data and therefore does not show the dust in the nebula.
In 2014, GLIMPSE released a 20-gigapixel mosaic of the Milky Way composed of over two million infrared images captured by Spitzer. Unlike optical telescopes, Spitzer can look beyond the Galactic Center, which has so much gas and dust that optical light is blocked.
“Spitzer is helping us determine where the edge of the galaxy lies. We are mapping the placement of the spiral arms and tracing the shape of the galaxy,” said GLIMPSE co-leader Ed Churchwell of the University of Wisconsin-Madison.
The infrared telescope has also imaged many low-mass stars in the outer regions of the galaxy, which could not previously be seen, said GLIMPSE co-leader Barbara Whitney, also of the University of Wisconsin-Madison.
“Spitzer is sensitive enough to pick these up and light up the entire ‘countryside’ with star formation,” Whitney said.
Another star-formation region photographed by Spitzer is Rho Ophiuchi, a stellar nursery located just 407 light years from Earth close to the constellations Scorpius and Ophiuchus. More than 300 very young stars have been observed in this dark region composed of molecular hydrogen in X-ray and infrared wavelengths. These stars have a median age of just 300,000 years.
“Rho Oph is a favorite region for astronomers studying star formation. Because the stars are so young, we can observe them at a very early evolutionary stage, and because the Ophiuchus molecular cloud is relatively close, we can resolve more detail than in more distant clusters like Orion,” noted Lori Allen of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA.
The image of Rho Ophiuchi is in false color so scientists can distinguish the stars’ different temperatures and evolutionary states. Young stars still surrounded by disks appear red while older stars that no longer have disks look blue.
Launched in 2003 for a 2.5-year initial mission, Spitzer is now scheduled to operate through November of next year (2019).
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.