miércoles, 23 de julio de 2014

Today's Astronomy Picture

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IC 4603: Reflection Nebula in Ophiuchius
Image Credit & Copyright: Rolf Olsen

Explanation: Why does this starfield photograph resemble an impressionistic painting? The effect is created not by digital trickery but by large amounts of interstellar dust. Dust, minute globs rich in carbon and similar in size to cigarette smoke, frequently starts in the outer atmospheres of large, cool, young stars. The dust is dispersed as the star dies and grows as things stick to it in the interstellar medium. Dense dust clouds are opaque to visible light and can completely hide background stars. For less dense clouds, the capacity of dust to preferentially reflect blue starlight becomes important, effectively blooming the stars blue light out and marking the surrounding dust. Nebular gas emissions, typically brightest in red light, can combine to form areas seemingly created on an artist's canvas. Photographed above is the central part of the nebula IC 4603 surrounding the bright star SAO 184376 (actually 8th magnitude) which mostly illuminates the blue reflection nebula. IC 4603 can be seen near the very bright star Antares (1st magnitude) toward the constellation of Ophiuchus.

Poll: Topics for APOD 2015 Wall Calendars
Tomorrow's picture: open space


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martes, 22 de julio de 2014

Today's Astronomy Picture

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Cave with Aurora Skylight
Image Credit & Copyright: Ingólfur Bjargmundsson

Explanation: Yes, but have you ever seen aurora from a cave? To capture this fascinating juxtaposition between below and above, astrophotographer Bjargmundsson spent much of a night alone in the kilometer-long Raufarhólshellir lava cave in Iceland during late March. There, he took separate images of three parts of the cave using a strobe for illumination. He also took a deep image of the sky to capture faint aurora, and digitally combined the four images later. The 4600-year old lava tube has several skylights under which stone rubble and snow have accumulated. Oh -- the person standing on each mound -- it's the artist.

Tomorrow's picture: dust impression


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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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lunes, 21 de julio de 2014

Today's Astronomy Picture

Astronomy Picture of the Day

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Spacecraft Rosetta Shows Comet has Two Components
Image Credit: ESA/Rosetta/MPS for OSIRIS Team; MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Explanation: Why does this comet's nucleus have two components? The surprising discovery that Comet 67P/Churyumov–Gerasimenko has a double nucleus came late last week as ESA's robotic interplanetary spacecraft Rosetta continued its approach toward the ancient comet's core. Speculative ideas on how the double core was created include, currently, that Comet Churyumov–Gerasimenko is actually the result of the merger of two comets, that the comet is a loose pile of rubble pulled apart by tidal forces, that ice evaporation on the comet has been asymmetric, or that the comet has undergone some sort of explosive event. Pictured above, the comet's unusual 5-km sized comet nucleus is seen rotating over the course of a few hours, with each frame taken 20-minutes apart. Better images -- and hopefully more refined theories -- are expected as Rosetta is on track to enter orbit around Comet Churyumov–Gerasimenko's nucleus early next month, and by the end of the year, if possible, land a probe on it.

Tomorrow's picture: view from a cave


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viernes, 18 de julio de 2014

Today's Astronomy Picture

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Ou4: A Giant Squid Nebula
Image Credit: Romano Corradi (IAC),
Nicolas Grosso, Agnès Acker, Robert Greimel, Patrick Guillout

Explanation: A mysterious, squid-like apparition, this nebula is very faint, but also very large in planet Earth's sky. In the mosaic image, composed with narrowband data from the 2.5 meter Isaac Newton Telescope, it spans some 2.5 full moons toward the constellation Cepheus. Recently discovered by French astro-imager Nicolas Outters, the remarkable nebula's bipolar shape and emission are consistent with it being a planetary nebula, the gaseous shroud of a dying sun-like star, but its actual distance and origin are unknown A new investigation suggests Ou4 really lies within the emission region SH2-129 some 2,300 light-years away. Consistent with that scenario, the cosmic squid would represent a spectacular outflow of material driven by a triple system of hot, massive stars, cataloged as HR8119, seen near the center of the nebula. If so, this truly giant squid nebula would physically be nearly 50 light-years across.

Tomorrow's picture: moon breams


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jueves, 17 de julio de 2014

Today's Astronomy Picture

Astronomy Picture of the Day

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3D Homunculus Nebula
Science Credit: W. Steffen (UNAM), M. Teodoro, T.I. Madura,
J.H. Groh, T.R. Gull, A. Mehner, M.F. Corcoran, A. Damineli, K. Hamaguchi

Image Credit: NASA, Goddard Space Flight Center/SVS - Inset: NASA, ESA, Hubble SM4 ERO Team

Explanation: If you're looking for something to print with that new 3D printer, try out a copy of the Homunculus Nebula. The dusty, bipolar cosmic cloud is around 1 light-year across but is slightly scaled down for printing to about 1/4 light-nanosecond or 80 millimeters. The full scale Homunculus surrounds Eta Carinae, famously unstable massive stars in a binary system embedded in the extensive Carina Nebula about 7,500 light-years distant. Between 1838 and 1845, Eta Carinae underwent the Great Eruption becoming the second brightest star in planet Earth's night sky and ejecting the Homunculus Nebula. The new 3D model of the still expanding Homunculus was created by exploring the nebula with the European Southern Observatory's VLT/X-Shooter. That instrument is capable of mapping the velocity of molecular hydrogen gas through the nebula's dust at a fine resolution. It reveals trenches, divots and protrusions, even in the dust obscured regions that face away from Earth. Eta Carinae itself still undergoes violent outbursts, a candidate to explode in a spectacular supernova in the next few million years.

Tomorrow's picture: nebula unknown


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miércoles, 16 de julio de 2014

Today's Astronomy Picture

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The Moon Eclipses Saturn
Image Credit & Copyright: Carlos Di Nallo

Explanation: What happened to half of Saturn? Nothing other than Earth's Moon getting in the way. As pictured above on the far right, Saturn is partly eclipsed by a dark edge of a Moon itself only partly illuminated by the Sun. This year the orbits of the Moon and Saturn have led to an unusually high number of alignments of the ringed giant behind Earth's largest satellite Technically termed an occultation, the above image captured one such photogenic juxtaposition from Buenos Aires, Argentina that occurred early last week. Visible to the unaided eye but best viewed with binoculars, there are still four more eclipses of Saturn by our Moon left in 2014. The next one will be on August 4 and visible from Australia, while the one after will occur on August 31 and be visible from western Africa at night but simultaneously from much of eastern North America during the day.

Tomorrow's picture: open space


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martes, 15 de julio de 2014

Today's Astronomy Picture

Astronomy Picture of the Day

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A Blue Bridge of Stars between Cluster Galaxies
Image Credit: NASA, ESA, G. Tremblay (ESO) et al.;
Acknowledgment: Hubble Heritage Team (STScI/AURA) - ESA/Hubble Collaboration

Explanation: Why is there a blue bridge of stars across the center of this galaxy cluster? First and foremost the cluster, designated SDSS J1531+3414, contains many large yellow elliptical galaxies. The cluster's center, as pictured above by the Hubble Space Telescope, is surrounded by many unusual, thin, and curving blue filaments that are actually galaxies far in the distance whose images have become magnified and elongated by the gravitational lens effect of the massive cluster. More unusual, however, is a squiggly blue filament near the two large elliptical galaxies at the cluster center. Close inspection of the filament indicates that it is most likely a bridge created by tidal effects between the two merging central elliptical galaxies rather than a background galaxy with an image distorted by gravitational lensing. The knots in the bridge are condensation regions that glow blue from the light of massive young stars. The central cluster region will likely undergo continued study as its uniqueness makes it an interesting laboratory of star formation.

Tomorrow's picture: missing saturn


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