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New Light On Galactic Pair – M81 and M82

A WISE Look At Messier 81 and Messier 82

Almost every amateur astronomer has viewed the ghostly glow of galactic pair, Messier 81 and Messier 82. They’re easily visible in small binoculars from a dark sky site and reveal wonderful details in a telescope as aperture increases. We’ve marveled over M81’s smooth, star-rich structure and the disturbed spindle-shaped structure of M82. We know the pair have interacted and the huge spiral has ingested stars from its companion – but today we know a whole lot more…

According to today’s press release from the American Astronomical Society, when the pair swept by each other, gravitational interactions triggered new bursts of star formation. In the case of Messier 82, also known as the Cigar Galaxy, the encounter has likely triggered a tremendous wave of new star birth at its core. Intense radiation from newborn massive stars is blowing copious amounts of gas and smoky dust out of the galaxy, as seen in the WISE image in yellow hues. The Cigar Galaxy is pictured above Messier 81. “What’s unique about the WISE view of this duo is that we can see both galaxies in one shot, and we can really see their differences,” said Ned Wright of UCLA, the principal investigator of WISE. “Because the Cigar Galaxy is bursting with star formation, it’s really bright in the infrared, and looks dramatically different from its less active companion.”

The WISE mission completed its main goal of mapping the sky in infrared light in October 2010, covering it one-and-one-half times before its frozen coolant ran out, as planned. During that time, it snapped pictures of hundreds of millions of objects, the first batch of which will be released to the astronomy community in April 2011. WISE is continuing its scan of the skies without coolant using two of its four infrared channels — the two shorter-wavelength channels not affected by the warmer temperatures. The mission’s ongoing survey is now focused primarily on asteroids and comets. Because WISE has imaged the entire sky, it excels at producing large mosaics like this new picture of Messier 81 and Messier 82, which covers a patch of sky equivalent to three-by-three full Moons, or 1.5 by 1.5 degrees.

It is likely these partner galaxies will continue to dance around each other, and eventually merge into a single entity. They are both spiral galaxies, but Messier 82 is seen from an edge-on perspective, and thus appears in visible light as a thin, cigar-like bar. (To me it has always looked like a child’s dirty kite string wrapped around a stick, eh?) When viewed in infrared light, Messier 82 is the brightest galaxy in the sky. It is what scientists refer to as a starburst galaxy because it is churning out large numbers of new stars. “The WISE picture really shows how spectacular Messier 82 shines in the infrared even though it is relatively puny in both size and mass compared to its big brother, Messier 81,” said Tom Jarrett, a member of the WISE team at the California Institute of Technology in Pasadena.

In this WISE view, infrared light has been color coded so that we can see it with our eyes. The shortest wavelengths (3.4 and 3.6 microns) are shown in blue and blue-green, or cyan, and the longer wavelengths (12 and 22 microns) are green and red. Messier 82 appears in yellow hues because its cocoon of dust gives off longer wavelengths of light (the yellow is a result of combining green and red). This dust is made primarily of polycyclic aromatic hydrocarbons, which are found on Earth as soot.

Messier 81, also known as Bode’s Galaxy, appears blue in the infrared image because it is not as dusty. The blue light is from stars in the galaxy. Knots of yellow seen dotting the spiral arms are dusty areas of recent star formation, most likely triggered by the galaxy’s encounter with its rowdy partner. “It’s striking how the same event stimulated a classic spiral galaxy in Messier 81, and a raging starburst in Messier 82,” said WISE Project Scientist Peter Eisenhardt of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “WISE is finding the most extreme starbursts across the whole sky, out to distances over a thousand times greater than Messier 82.”

Next time you view M81 and M82, perhaps you’ll see them in a new light?

Original Source: American Astronomical Society Press Release – WISE Image Credit: NASA
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About 

Tammy is a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She’s received a vast number of astronomy achievement and observing awards, including the Great Lakes Astronomy Achievement Award, RG Wright Service Award and the first woman astronomer to achieve Comet Hunter's Gold Status.

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  • Aqua January 13, 2011, 4:10 PM

    Messier 81 and Messier 82 are always hard to locate with my fork mounted S/C… To look anywhere near the pole the eyepiece tends to interfere with the mount and the controls seem less effective? I always end up sweeping to pick them up when I know I’m in the right neighborhood. Rotating the eyepiece and squinching down and then leaning over to view M81 and M82 are always a worthy astro yoga! HO!

    • Aqua January 13, 2011, 4:22 PM

      Got clouds? I do…. should clear up soon? Maybe April? Dzzzz… Of course there will always be those occasional EXCEPTIONALLY CLEAR and cold winter nights… say, right after a storm? so I WILL get a chance at going up the mountain a take a lil ol peeky poo here and there and have to be okay with that?

  • Tammy Plotner January 13, 2011, 5:46 PM

    ssssh… don’t tell the polar alignment police, but i have been known to simply pick up an EQ mount and turn it around so i am comfortable. sure, you gotta’ hand track, but who cares? ;)

    • Aqua January 13, 2011, 6:44 PM

      The polar alignment police…. Ha ha ha ha… I did similar with one of my german eq. mounts when the tube collided with the R.A. drive gear… this while on a comet search… Then I packed up and went home. One new moon later and I’m back at it but can’t figure out what the heck’s wrong with the stupid set up – it’s upside down? WHO’s been messing with my scope? DuhOH! Oh yeah… sheepish grin, I finally remember that I’d done this the month before and flip the mount back over and get back to biz! Oh that ‘silly’ feeling…. you know the one I’m talking about? The one that gets to you at 3 am.?

  • santafedog January 14, 2011, 11:15 AM

    Probably my favorite pair of galaxies. Somehow, i always feel kind of proud of them when i show them in one eyepiece at star tours, but somehow, i never realized they are really a double sta….double galaxy system. This is making me start to get an itch for astrophotography and filter use. Thank you WISE!

  • Torbjorn Larsson OM January 15, 2011, 2:55 AM

    “See, these two galaxies meet in the night…”

    FWIW, I don’t think PAHs are as much soot, as a major component in most or all sorts. But soot is a sort of “dark matter” [sic!] as far as references go, the reviews are hard to get to from home.

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