David Hamed

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APOD: M16: Pillars of Creation (2012 Jul 22) Image Credit: J. Hester, P. Scowen (ASU), HST, NASA http://apod.nasa.gov/apod/ap120722.html Explanation: It was one of the most famous images of the 1990s. 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. http://hubblesite.org/news/1995/44 Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=120722 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=0722

APOD: The Milky Way Over Monument Valley (2012 Aug 01) Image Credit & Copyright: Wally Pacholka (AstroPics.com, TWAN) http://apod.nasa.gov/apod/ap120801.html Explanation: You don't have to be at Monument Valley to see the Milky Way arch across the sky like this -- but it helps. Only at Monument Valley USA would you see a picturesque foreground that includes these iconic rock peaks called buttes. Buttes are composed of hard rock left behind after water has eroded away the surrounding soft rock. In the above image taken about two months ago, the closest butte on the left and the butte to its right are known as the Mittens, while Merrick Butte can be seen just further to the right. High overhead stretches a band of diffuse light that is the central disk of our spiral Milky Way Galaxy. The band of the Milky Way can be spotted by almost anyone on almost any clear night when far enough from a city and surrounding bright lights. http://www.twanight.org/pacholka http://www.astropics.com/ Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=120801 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=0801

APOD: Hurricane Paths on Planet Earth (2012 Sep 04) Image Credit & Copyright: John Nelson, IDV Solutions http://apod.nasa.gov/apod/ap120904.html Explanation: Should you be worried about hurricanes? To find out, it is useful to know where hurricanes have gone in the past. The above Earth map shows the path of every hurricane reported since 1851, Although striking, a growing incompleteness exists in the data the further one looks back in time. The above map graphically indicates that hurricanes -- sometimes called cyclones or typhoons depending on where they form -- usually occur over water, which makes sense since evaporating warm water gives them energy. The map also shows that hurricanes never cross -- or even occur very near -- the Earth's equator, since the Coriolis effect goes to zero there, and hurricanes need the Coriolis force to circulate. The Coriolis force also causes hurricane paths to arc away from the equator. Although incompleteness fogs long term trends and the prevalence of hurricanes remains a topic of research, evidence is accumulating that hurricanes are, on the average, more common and more powerful in the North Atlantic Ocean over the past 20 years. http://www.blogger.com/profile/05293746895235613547 http://www.idvsolutions.com/Company/AboutUs.aspx http://www.flickr.com/photos/idvsolutions/7840356344/ Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=120904 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=0904

APOD: Simeis 147: Supernova Remnant (2012 Oct 09) Image Credit & Copyright: Rogelio Bernal Andreo (Deep Sky Colors) http://apod.nasa.gov/apod/ap121009.html Explanation: It's easy to get lost following the intricate filaments in this detailed mosaic image of faint supernova remnant Simeis 147 (S147). Also cataloged as Sh2-240, it covers nearly 3 degrees or 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. Anchoring the frame at the right, bright star Elnath (Beta Tauri) is seen towards the boundary of the constellations Taurus and Auriga, almost exactly opposite the galactic center in planet Earth's sky. 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 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. http://blog.deepskycolors.com/ Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=121009 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=1009

APOD: The Hubble eXtreme Deep Field (2012 Oct 14) Image Credit: NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (UCSC), R. Bouwens (Leiden Obs.), HUDF09 Team http://apod.nasa.gov/apod/ap121014.html Explanation: What did the first galaxies look like? To help answer this question, the Hubble Space Telescope has just finished taking the eXtreme Deep Field (XDF), the deepest image of the universe ever taken in visible light. Pictured above, the XDF shows a sampling of some of the oldest galaxies ever seen, galaxies that formed just after the dark ages, 13 billion years ago, when the universe was only a few percent of its present age. The Hubble Space Telescope's ACS camera and the infrared channel of the WFPC3 camera took the image. Combining efforts spread over 10 years, the XDF is more sensitive, in some colors, than the original Hubble Deep Field (HDF), the Hubble Ultra Deep Field (HUDF) completed in 2004, and the HUDF Infrared completed in 2009. Astronomers the world over will likely study the XDF for years to come to better understand how stars and galaxies formed in the early universe. http://hubblesite.org/news/2012/37 http://www.spacetelescope.org/news/heic1214/ http://www.youtube.com/watch?v=gu_VhzhlqGw Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=121014 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=1014

APOD: The Horsehead Nebula (2012 Oct 21) Credit & Copyright: Nigel Sharp (NOAO), KPNO, AURA, NSF http://apod.nasa.gov/apod/ap121021.html Explanation: One of the most identifiable nebulae in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s. The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming. Light takes about 1,500 years to reach us from the Horsehead Nebula. The above image was taken with the 0.9-meter telescope at Kitt Peak National Observatory. http://www.noao.edu/image_gallery/html/im0057.html Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=121021 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=1021

APOD: NGC 6357's Cathedral to Massive Stars (2012 Nov 18) Image Credit: NASA, ESA and J. M. Apellániz (IAA, Spain) http://apod.nasa.gov/apod/ap121118.html Explanation: How massive can a normal star be? Estimates made from distance, brightness and standard solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, nearly making it the record holder. This star is the brightest object located just above the gas front in the above image. Close inspection of images taken with the Hubble Space Telescope, however, have shown that Pismis 24-1 derives its brilliant luminosity not from a single star but from three at least. Component stars would still remain near 100 solar masses, making them among the more massive stars currently on record. Toward the bottom of the image, stars are still forming in the associated emission nebula NGC 6357. Appearing perhaps like a Gothic cathedral, energetic stars near the center appear to be breaking out and illuminating a spectacular cocoon. http://www.spacetelescope.org/news/heic0619/ http://hubblesite.org/news/2006/54 Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=121118 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=1118

APOD: A Year on the Sun (2013 Apr 26) Image Credit: NASA, Solar Dynamics Observatory http://apod.nasa.gov/apod/ap130426.html Explanation: Our solar system's miasma of incandescent plasma, the Sun may look a little scary here. The picture is a composite of 25 images recorded in extreme ultraviolet light by the orbiting Solar Dynamics Observatory between April 16, 2012 and April 15, 2013. The particular wavelength of light, 171 angstroms, shows emission from highly ionized iron atoms in the solar corona at a characteristic temperatures of about 600,000 kelvins (about 1 million degrees F). Girdling both sides of the equator during the approach to maximum in its 11-year solar cycle, the solar active regions are laced with bright loops and arcs along magnetic field lines. Of course, a more familiar visible light view would show the bright active regions as groups of dark sunspots. Three years of Solar Dynamics Observatory images are compressed into this short video. http://www.nasa.gov/mission_pages/sdo/news/first-light-3rd.html http://www.youtube.com/watch?v=dHvPJp9YFfY Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=130426 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=0426

APOD: NGC 6960: The Witch's Broom Nebula (2013 May 29) Image Credit & Copyright: Martin Pugh http://apod.nasa.gov/apod/ap130529.html Explanation: Ten thousand years ago, before the dawn of recorded human history, a new light would have suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was from a supernova, or exploding star, and record the expanding debris cloud as the Veil Nebula, a supernova remnant. This sharp telescopic view is centered on a western segment of the Veil Nebula cataloged as NGC 6960 but less formally known as the Witch's Broom Nebula. Blasted out in the cataclysmic explosion, the interstellar shock wave plows through space sweeping up and exciting interstellar material. Imaged with narrow band filters, the glowing filaments are like long ripples in a sheet seen almost edge on, remarkably well separated into atomic hydrogen (red) and oxygen (blue-green) gas. The complete supernova remnant lies about 1400 light-years away towards the constellation Cygnus. This Witch's Broom actually spans about 35 light-years. The bright star in the frame is 52 Cygni, visible with the unaided eye from a dark location but unrelated to the ancient supernova remnant. http://www.martinpughastrophotography.id.au/ Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=130529 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=0529

APOD: The Milky Trail (2013 Jun 01) Image Credit & Copyright: Wally Pacholka (AstroPics.com, TWAN) http://apod.nasa.gov/apod/ap130601.html Explanation: Have you ever hiked the Queen's Garden trail in Bryce Canyon, Utah, USA, planet Earth? Walking along that path in this dark night skyscape, you can almost imagine your journey continues along the pale, luminous Milky Way. Of course, the name for our galaxy, the Milky Way (in Latin, Via Lactea), does refer to its appearance as a milky band or path in the sky. In fact, the word galaxy itself derives from the Greek for milk. Visible on moonless nights from dark sky areas, though not so bright or quite so colorful as in this image, the glowing celestial band is due to the collective light of myriad stars along the plane of our galaxy, too faint to be distinguished individually. The diffuse starlight is cut by dark swaths of obscuring galactic dust clouds. Four hundred years ago, Galileo turned his telescope on the Milky Way and announced it to be "... a congeries of innumerable stars ..." http://twanight.org/pacholka http://astropics.com/ Starship Asterisk* • APOD Discussion Page http://asterisk.apod.com/discuss_apod.php?date=130601 Starship Asterisk* • On This Day in APOD http://asterisk.apod.com/view_retro.php?date=0601