Cold’s Greenish Glow

Credit: NASA, ESA and Moham­mad Heydari-Malayeri (Obser­va­toire de Paris, France)

Cold doesn’t actu­ally have a color; well, maybe blue lips in the win­ter­time. To help us see new stars being born deep within the thick dust of neb­u­lae, astronomers use spe­cial tele­scopes to see the star’s glow.

Explore the green­ish mist sur­round­ing GL 490 in this image from NASA’s Spitzer Space Tele­scope. Besides the green­ish streaks, what else do you see in the green cloud? Tell us in the com­ment area below.

Zoom into GL 490, glow­ing in the mid­dle right of the image. The fog sur­round­ing the bright stars in this image are made up of hydro­gen and car­bon com­pounds called PAHs, short for poly­cyclic aro­matic hydro­car­bons. You can go out today and see PAHs for your­self in the form of sooty car exhaust and the sticky soot on a char­coal grill. While PAHs aren’t green in space, astronomers give them that color so they can see and study them. In space, PAHs make up the dark clouds of star-forming neb­u­lae. The neb­u­lae are very cold, but the stars cause PAHs to warm up slightly and glow in infrared light; a part of the light spec­trum that we can­not see. We can feel it how­ever, in the form of heat.

Explore the area around the upper bright star. Streaks around the star at the top left are prob­a­bly dust grains lined up with the star’s mag­netic field, sim­i­lar to how iron dust forms lines on paper when a mag­net is held under­neath. This dust lies between Earth and the star. Instead of glow­ing, this dust is prob­a­bly reflect­ing the light of the back­ground star. The yel­low­ish color isn’t real either. Sci­en­tists use col­ors to help them track tem­per­a­ture in the cloud. Yel­low is just a bit warmer than the sur­round­ing colder green dust. Also find sev­eral blobby bub­bles. These globs of stretched out gas indi­cate the mak­ing of young, mas­sive stars. This mate­r­ial, blown out from both ends of the star, may one day fall back toward the star to form planets.

GL490 is about 3,000 light-years from Earth which makes it rel­a­tively close for astronomers to study. This image is part of the new GLIMPSE360 sky sur­vey and is a com­bi­na­tion of data taken from Spitzer and the Two Micron All Sky Sur­vey (2MASS)