Fermi’s Gamma-ray Moon


If you could only see gamma-rays, photons with up to a billion or more times the energy of visible light, the Moon would be brighter than the Sun! That startling notion underlies this novel image of the Moon, based on data collected by the Fermi Gamma-ray Space Telescope’s Large Area Telescope (LAT) instrument during its first seven years of operation (2008-2015). Fermi’s gamma-ray vision doesn’t distinguish details on the lunar surface, but a gamma-ray glow consistent with the Moon’s size and position is clearly found at the center of the false color map. The brightest pixels correspond to the most significant detections of lunar gamma-rays. Why is the gamma-ray Moon so bright? High-energy charged particles streaming through the Solar System known as cosmic rays constantly bombard the lunar surface, unprotected by a magnetic field, generating the gamma-ray glow. Because the cosmic rays come from all sides, the gamma-ray Moon is always full and does not go through phases. The first gamma-ray image of the Moon was captured by the EGRET instrument onboard the Compton Gamma-ray Observatory, launched 25 years ago.

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A Dust Angel Nebula


The combined light of stars along the Milky Way are reflected by these cosmic dust clouds that soar some 300 light-years or so above the plane of our galaxy. Dubbed the Angel Nebula, the faint apparition is part of an expansive complex of dim and relatively unexplored, diffuse molecular clouds. Commonly found at high galactic latitudes, the dusty galactic cirrus can be traced over large regions toward the North and South Galactic poles. Along with the refection of starlight, studies indicate the dust clouds produce a faint reddish luminescence, as interstellar dust grains convert invisible ultraviolet radiation to visible red light. Also capturing nearby Milky Way stars and an array of distant background galaxies, the deep, wide-field 3×5 degree image spans about 10 Full Moons across planet Earth’s sky toward the constellation Ursa Major.

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Omega Centauri: The Brightest Globular Star Cluster


This huge ball of stars predates our Sun. Long before humankind evolved, before dinosaurs roamed, and even before our Earth existed, ancient globs of stars condensed and orbited a young Milky Way Galaxy. Of the 200 or so globular clusters that survive today, Omega Centauri is the largest, containing over ten million stars. Omega Centauri is also the brightest globular cluster, at apparent visual magnitude 3.9 it is visible to southern observers with the unaided eye. Cataloged as NGC 5139, Omega Centauri is about 18,000 light-years away and 150 light-years in diameter. Unlike many other globular clusters, the stars in Omega Centauri show several different ages and trace chemical abundances, indicating that the globular star cluster has a complex history over its 12 billion year age.

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NGC 6872: A Stretched Spiral Galaxy


What makes this spiral galaxy so long? Measuring over 700,000 light years across from top to bottom, NGC 6872, also known as the Condor galaxy, is one of the most elongated barred spiral galaxies known. The galaxy‘s protracted shape likely results from its continuing collision with the smaller galaxy IC 4970, visible just above center. Of particular interest is NGC 6872’s spiral arm on the upper left, as pictured here, which exhibits an unusually high amount of blue star forming regions. The light we see today left these colliding giants before the days of the dinosaurs, about 300 million years ago. NGC 6872 is visible with a small telescope toward the constellation of the Peacock (Pavo).

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Simeis 147: Supernova Remnant


It’s easy to get lost following the intricate strands of the Spaghetti Nebula. A supernova remnant cataloged as Simeis 147 and Sh2-240, the glowing gas filaments cover nearly 3 degrees — 6 full moons — on the sky. That’s about 150 light-years at the stellar debris cloud’s estimated distance of 3,000 light-years. This sharp composite includes image data taken through a narrow-band filter to highlight emission from hydrogen atoms tracing the shocked, glowing gas. The supernova remnant has an estimated age of about 40,000 years, meaning light from the massive stellar explosion first reached Earth about 40,000 years ago. But the expanding remnant is not the only aftermath. The cosmic catastrophe also left behind a spinning neutron star or pulsar, all that remains of the original star’s core.

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M16: Pillars of Star Creation


Newborn stars are forming in the Eagle Nebula. This image, taken with the Hubble Space Telescope in 1995, shows evaporating gaseous globules (EGGs) emerging from pillars of molecular hydrogen gas and dust. The giant pillars are light years in length and are so dense that interior gas contracts gravitationally to form stars. At each pillars’ end, the intense radiation of bright young stars causes low density material to boil away, leaving stellar nurseries of dense EGGs exposed. The Eagle Nebula, associated with the open star cluster M16, lies about 7000 light years away. The pillars of creation were imaged again in 2007 by the orbiting Spitzer Space Telescope in infrared light, leading to the conjecture that the pillars may already have been destroyed by a local supernova, but light from that event has yet to reach the Earth.

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