floor of a cavern – are composed of interstellar hydrogen gas and dust, which act as incubators for new stars. Inside the columns and on their surface astronomers have found knots or globules of denser gas, called EGGs ("Evaporating Gaseous Globules"). Stars are being formed inside some of these. X-ray images from the Chandra observatory compared with Hubble's "Pillars" image have shown that X-ray sources (from young stars) do not coincide with the pillars, but rather randomly dot the nebula. Any protostars in the pillars' EGGs are not yet hot enough to emit X-rays. Evidence from the Spitzer Space Telescope originally suggested that the pillars in M16 may be threatened by a "past supernova". Hot gas observed by Spitzer in 2007 suggested they were already – likely – being disturbed by a supernova that exploded 8,000 to 9,000 years ago. Due to the distance the main blast of light would have reached Earth for a brief time 1,000 to 2,000 years ago. A more slowly moving, theorized, shock wave would have taken a few thousand years to move through the nebula and would have blown away the delicate pillars. However, in 2014 the pillars were imaged a second time by Hubble, in both visible light and infrared light. The images being 20 years later provided a new, detailed account of the rate of evaporation occurring within the pillars. No supernova is evidenced within them, and it is estimated in some form they still exist – and will appear for at least 100,000 more years. Gallery See also List of Messier objects References External links The Eagle's EGGs – ESO Photo Release ESO: An Eagle of Cosmic Proportions incl. Photos & Animations ESO: VST Captures Three-In-One incl. Photos & Animations M16 @ Seds.org, SEDS Messier page on M16 Spacetelescope.org, Hubble telescope images on M16 Darkatmospheres.com, Eagle Nebula M16 (wide) NASA.gov, APOD February 8, 2009 picture Eagle Nebula Eagle Nebula (Messier 16) at Constellation Guide Carina–Sagittarius Arm Messier objects Serpens (constellation) Open clusters NGC objects H II regions Sharpless objects 17451231 Star-forming regions