Sometimes galaxies form groups. For example, our own Milky Way Galaxy [ http://antwrp.gsfc.…] is part of the Local Group of Galaxies [ http://www.seds.org…]. Small, compact groups, like Hickson Compact Group [ http://crystal.ipac…] 87 (HCG 87) shown above [ http://heritage.sts…], are interesting partly because they slowly self-destruct. Indeed, the galaxies of HCG [ http://adsbit.harva…] 87 are gravitationally stretching each other during their 100-million year orbits around a common center. The pulling creates colliding gas that causes bright bursts of star formation [ http://antwrp.gsfc.…] and feeds matter into their active galaxy [ http://imagine.gsfc…] centers. HCG 87 [ http://heritage.sts…] is composed of a large edge-on [ http://antwrp.gsfc.…] spiral galaxy [ http://antwrp.gsfc.…] visible on the lower left, an elliptical galaxy [ http://www.seds.org…] visible on the lower right, and a spiral galaxy [ http://www.windows.…] visible near the top. The small spiral near the center might be far in the distance. Several stars from our Galaxy [ http://www.damtp.ca…] are also visible in the foreground. The above picture was taken in July by the Hubble Space Telescope [ http://antwrp.gsfc.…]'s Wide Field Planetary Camera 2 [ http://www.stsci.ed…]. Studying groups like HCG 87 allows insight into how all galaxies form and evolve [ http://ngst.gsfc.na…].
Explanation
Sometimes galaxies form groups. For example, our own Milky Way Galaxy [ http://antwrp.gsfc.…] is part of the Local Group of Galaxies [ http://www.seds.org…]. Small, compact groups, like Hickson Compact Group [ http://crystal.ipac…] 87 (HCG 87) shown above [ http://heritage.sts…], are interesting partly because they slowly self-destruct. Indeed, the galaxies of HCG [ http://adsbit.harva…] 87 are gravitationally stretching each other during their 100-million year orbits around a common center. The pulling creates colliding gas that causes bright bursts of star formation [ http://antwrp.gsfc.…] and feeds matter into their active galaxy [ http://imagine.gsfc…] centers. HCG 87 [ http://heritage.sts…] is composed of a large edge-on [ http://antwrp.gsfc.…] spiral galaxy [ http://antwrp.gsfc.…] visible on the lower left, an elliptical galaxy [ http://www.seds.org…] visible on the lower right, and a spiral galaxy [ http://www.windows.…] visible near the top. The small spiral near the center might be far in the distance. Several stars from our Galaxy [ http://www.damtp.ca…] are also visible in the foreground. The above picture was taken in July by the Hubble Space Telescope [ http://antwrp.gsfc.…]'s Wide Field Planetary Camera 2 [ http://www.stsci.ed…]. Studying groups like HCG 87 allows insight into how all galaxies form and evolve [ http://ngst.gsfc.na…].
