суббота, 28 ноября 2015 г.

Gravity's Grin

Albert Einstein's general theory of relativity, published 100 years ago this month, predicted the phenomenon of gravitational lensing. And that's what gives these distant galaxies such a whimsical appearance, seen through the looking glass of X-ray and optical image data from the Chandra and Hubble space telescopes. Nicknamed the Cheshire Cat galaxy group, the group's two large elliptical galaxies are suggestively framed by arcs. The arcs are optical images of distant background galaxies lensed by the foreground group's total distribution of gravitational mass dominated by dark matter. In fact the two large elliptical "eye" galaxies represent the brightest members of their own galaxy groups which are merging. Their relative collisional speed of nearly 1,350 kilometers/second heats gas to millions of degrees producing the X-ray glow shown in purple hues. Curiouser about galaxy group mergers? The Cheshire Cat group grins in the constellation Ursa Major, some 4.6 billion light-years away. via NASA http://ift.tt/1HskNFu

пятница, 27 ноября 2015 г.

Planets of the Morning

Planet Earth's horizon stretches across this recent Solar System group portrait, seen from the southern hemisphere's Las Campanas Observatory. Taken before dawn it traces the ecliptic with a line-up familiar to November's early morning risers. Toward the east are bright planets Venus, Mars, and Jupiter as well as Regulus, alpha star of the constellation Leo. Of course the planets are immersed in the faint glow of zodiacal light, visible from the dark site rising at an angle from the horizon. Sometimes known as the false dawn, it's no accident the zodiacal light and planets both lie along the ecliptic. Formed in the flattened protoplanetary disk, the Solar System's planet's all orbit near the ecliptic plane, while dust near the plane scatters sunlight, the source of the faint zodiacal glow. via NASA http://ift.tt/1NvB8f9

четверг, 26 ноября 2015 г.

Unusual Pits Discovered on Pluto

Why are there unusual pits on Pluto? The indentations were discovered during the New Horizons spacecraft's flyby of the dwarf planet in July. The largest pits span a kilometer across and dip tens of meters into a lake of frozen nitrogen, a lake that sprawls across Sputnik Planum, part of the famous light-colored heart-shaped region named Tombaugh Regio. Although most pits in the Solar System are created by impact craters, these depressions look different -- many are similarly sized, densely packed, and aligned. Rather, it is thought that something has caused these specific areas of ice to sublimate and evaporate away. In fact, the lack of overlying impact craters indicates these pits formed relatively recently. Even though the robotic New Horizons is now off to a new destination, it continues to beam back to Earth new images and data from its dramatic encounter with Pluto. via NASA http://ift.tt/1QHXIRV

среда, 25 ноября 2015 г.

Aurora over Clouds

Auroras usually occur high above the clouds. The auroral glow is created when fast-moving particles ejected from the Sun impact the Earth's magnetosphere, from which charged particles spiral along the Earth's magnetic field to strike atoms and molecules high in the Earth's atmosphere. An oxygen atom, for example, will glow in the green light commonly emitted by an aurora after being energized by such a collision. The lowest part of an aurora will typically occur at 100 kilometers up, while most clouds usually exist only below about 10 kilometers. The relative heights of clouds and auroras are shown clearly in the featured picture from Dyrholaey, Iceland. There, a determined astrophotographer withstood high winds and initially overcast skies in an attempt to capture aurora over a picturesque lighthouse, only to take, by chance, the featured picture along the way. via NASA http://ift.tt/1IdvuGN

вторник, 24 ноября 2015 г.

A 212 Hour Exposure of Orion

The constellation of Orion is much more than three stars in a row. It is a direction in space that is rich with impressive nebulas. To better appreciate this well-known swath of sky, an extremely long exposure was taken over many clear nights in 2013 and 2014. After 212 hours of camera time and an additional year of processing, the featured 1400-exposure collage spanning over 40 times the angular diameter of the Moon emerged. Of the many interesting details that have become visible, one that particularly draws the eye is Barnard's Loop, the bright red circular filament arcing down from the middle. The Rosette Nebula is not the giant red nebula near the top of the image -- that is a larger but lesser known nebula known as Lambda Orionis. The Rosette Nebula is visible, though: it is the red and white nebula on the upper left. The bright orange star just above the frame center is Betelgeuse, while the bright blue star on the lower right is Rigel. Other famous nebulas visible include the Witch Head Nebula, the Flame Nebula, the Fox Fur Nebula, and, if you know just where to look, the comparatively small Horsehead Nebula. About those famous three stars that cross the belt of Orion the Hunter -- in this busy frame they can be hard to locate, but a discerning eye will find them just below and to the right of the image center. via NASA http://ift.tt/1YplPWR

понедельник, 23 ноября 2015 г.

Phobos: Doomed Moon of Mars

This moon is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These martian moons may well be captured asteroids originating in the main asteroid belt between Mars and Jupiter or perhaps from even more distant reaches of the Solar System. The larger moon, Phobos, is indeed seen to be a cratered, asteroid-like object in this stunning color image from the robotic Mars Reconnaissance Orbiter, recorded at a resolution of about seven meters per pixel. But Phobos orbits so close to Mars - about 5,800 kilometers above the surface compared to 400,000 kilometers for our Moon - that gravitational tidal forces are dragging it down. A recent analysis of the long grooves indicates that they may result from global stretching caused by tides -- the differing force of Mars' gravity on different sides of Phobos. These grooves may then be an early phase in the disintegration of Phobos into a ring of debris around Mars. via NASA http://ift.tt/1XiNczv

воскресенье, 22 ноября 2015 г.

Recycling NGC 5291

Following an ancient galaxy-galaxy collision 200 million light-years from Earth, debris from a gas-rich galaxy, NGC 5291, was flung far into intergalactic space. NGC 5291 and the likely interloper, also known as the "Seashell" galaxy, are captured near the center of this spectacular scene. The sharp, ground-based telescopic image looks toward the galaxy cluster Abell 3574 in the southern constellation Centaurus. Stretched along the 100,000 light-year long tidal tails, are clumps resembling dwarf galaxies, but lacking old stars, apparently dominated by young stars and active star forming regions. Found to be unusually rich in elements heavier than hydrogen and helium, the dwarf galaxies were likely born in intergalactic space, recycling the enriched debris from NGC 5291 itself. via NASA http://ift.tt/1jcVCee