April 18, 2015

ALMA image of the gravitationally lensed galaxy SDP 81

SDP 81 Galaxy

The bright orange central region of the ring (ALMA's highest-resolution observation ever) reveals the glowing dust in this distant galaxy. The surrounding lower-resolution portions of the ring trace the millimetre-wavelength light emitted by carbon dioxide and water molecules.

Image Credit: ALMA (NRAO/ESO/NAOJ); B. Saxton NRAO/AUI/NSF
Explanation from: http://www.eso.org/public/images/ann15028a/

April 17, 2015

NGC 2146

NGC 2146

A galaxy being stretched out of shape has been imaged by the NASA/ESA Hubble Space Telescope. Known as NGC 2146, it has been severely warped and deformed so that an immense dusty arm of glittering material now lies directly in front of the centre of the galaxy, as seen in the image.

NGC 2146 is classified as a barred spiral due to its shape, but the most distinctive feature is the dusty spiral arm that has looped in front of the galaxy's core as seen from our perspective. The forces required to pull this structure out of its natural shape and twist it up to 45 degrees are colossal. The most likely explanation is that a neighbouring galaxy is gravitationally perturbing it and distorting the orbits of many of NGC 2146’s stars. It is probable that we are currently witnessing the end stages of a process which has been occurring for tens of millions of years.

NCG 2146 is undergoing intense bouts of star formation, to such an extent that it is referred to as a starburst galaxy. This is a common state for barred spirals, but the extra gravitational disruption that NGC 2146 is enduring no doubt exacerbates the situation, compressing hydrogen-rich nebulae and triggering stellar birth.

Measuring about 80 000 light-years from end to end, NGC 2146 is slightly smaller than the Milky Way. It lies approximately 70 million light-years distant in the faint northern constellation of Camelopardalis (The Giraffe). Although it is fairly easy to see with a moderate-sized telescope as a faint elongated blur of light it was not spotted until 1876 when the German astronomer Friedrich Winnecke found it visually using just a 16 cm telescope.

This picture was created from images taken with the Wide Field Channel of Hubble’s Advanced Camera for Surveys. Images through a near-infrared filter (F814W, coloured blue and orange/brown) were combined with images taken in a filter that isolates the glow from hydrogen gas (F658N, coloured red). An additional green colour channel was also created by combining the two to help to create a realistic colour rendition for the final picture from this unusual filter combination. The total exposure times were 120 s and 700 s respectively and the field of view is covers 2.6 x 1.6 arcminutes.

Image Credit: ESA/Hubble & NASA
Explanation from: http://www.spacetelescope.org/images/potw1134a/

NGC 6388: White Dwarf May Have Shredded Passing Planet

NGC 6388NGC 6388 X-rayNGC 6388 Optical

What is it?
A globular cluster about 35,000 light years from Earth.

How Far Away is it?
About 35,000 light years.

How is it Made?
X-rays from the Chandra X-ray Observatory and optical data from Hubble.

How Big is it?
About 38 light years.

What do the Colors Mean?
X-rays are pink and optical are red, green and blue.

Where is it Located?
In the constellation Scorpius.

  • A planet may have been ripped apart by a white dwarf star in the outskirts of the Milky Way.
  • A white dwarf is the dense core of a star like the Sun that has run out of nuclear fuel.
  • Combining data from Chandra and several other telescopes, researchers think a "tidal disruption" may explain what is observed.

The destruction of a planet may sound like the stuff of science fiction, but a team of astronomers has found evidence that this may have happened in an ancient cluster of stars at the edge of the Milky Way galaxy.

Using several telescopes, including NASA's Chandra X-ray Observatory, researchers have found evidence that a white dwarf star - the dense core of a star like the Sun that has run out of nuclear fuel - may have ripped apart a planet as it came too close.

How could a white dwarf star, which is only about the size of the Earth, be responsible for such an extreme act? The answer is gravity. When a star reaches its white dwarf stage, nearly all of the material from the star is packed inside a radius one hundredth that of the original star. This means that, for close encounters, the gravitational pull of the star and the associated tides, caused by the difference in gravity's pull on the near and far side of the planet, are greatly enhanced. For example, the gravity at the surface of a white dwarf is over ten thousand times higher than the gravity at the surface of the Sun.

Researchers used the European Space Agency's INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) to discover a new X-ray source near the center of the globular cluster NGC 6388. Optical observations had hinted that an intermediate-mass black hole with mass equal to several hundred Suns or more resides at the center of NGC 6388. The X-ray detection by INTEGRAL then raised the intriguing possibility that the X-rays were produced by hot gas swirling towards an intermediate-mass black hole.

In a follow-up X-ray observation, Chandra's excellent X-ray vision enabled the astronomers to determine that the X-rays from NGC 6388 were not coming from the putative black hole at the center of the cluster, but instead from a location slightly off to one side. A new composite image shows NGC 6388 with X-rays detected by Chandra in pink and visible light from the Hubble Space Telescope in red, green, and blue, with many of the stars appearing to be orange or white. Overlapping X-ray sources and stars near the center of the cluster also causes the image to appear white.

With the central black hole ruled out as the potential X-ray source, the hunt continued for clues about the actual source in NGC 6388. The source was monitored with the X-ray telescope on board NASA's Swift Gamma Ray Burst mission for about 200 days after the discovery by INTEGRAL.

The source became dimmer during the period of Swift observations. The rate at which the X-ray brightness dropped agrees with theoretical models of a disruption of a planet by the gravitational tidal forces of a white dwarf. In these models, a planet is first pulled away from its parent star by the gravity of the dense concentration of stars in a globular cluster. When such a planet passes too close to a white dwarf, it can be torn apart by the intense tidal forces of the white dwarf. The planetary debris is then heated and glows in X-rays as it falls onto the white dwarf. The observed amount of X-rays emitted at different energies agrees with expectations for a tidal disruption event.

The researchers estimate that the destroyed planet would have contained about a third of the mass of Earth, while the white dwarf has about 1.4 times the Sun's mass.

While the case for the tidal disruption of a planet is not iron-clad, the argument for it was strengthened when astronomers used data from the multiple telescopes to help eliminate other possible explanations for the detected X-rays. For example, the source does not show some of the distinctive features of a binary containing a neutron star, such as pulsations or rapid X-ray bursts. Also, the source is much too faint in radio waves to be part of a binary system with a stellar-mass black hole.

Image Credit: X-ray: NASA/CXC/IASF Palermo/M.Del Santo et al; Optical: NASA/STScI
Explanation from: http://chandra.harvard.edu/photo/2015/ngc6388/

April 16, 2015

The Eyes Galaxies: NGC 4438 • NGC 4435

Eyes Galaxies: NGC 4038 • NGC 4039

This striking image, taken with the FORS2 instrument on the Very Large Telescope, shows a beautiful yet peculiar pair of galaxies, NGC 4438 and NGC 4435, nicknamed The Eyes. The larger of these, at the top of the picture, NGC 4438, is thought to have once been a spiral galaxy that was strongly deformed by collisions in the relatively recent past. The two galaxies belong to the Virgo Cluster and are about 50 million light-years away.

Image Credit: ESO
Explanation from: http://www.eso.org/public/images/eso1131a/

April 15, 2015

Panorama of the Milky Way Galaxy

Milky Way Panorama

This 360-degree panoramic image covers the entire southern and northern celestial sphere.

Image Credit: ESO/S. Brunier

April 14, 2015

Moons of Mars: Deimos

Moons of Mars: Deimos

Deimos is the smaller of Mars' two moons. Being only 15 by 12 by 11 km in size, Deimos whirls around Mars every 30 hours.

Like Phobos, Deimos is a small lumpy, heavily cratered object. Its craters are generally smaller than 2.5 km in diameter, however, and it lacks the grooves and ridges seen on Phobos. Typically when a meteorite hits a surface, surface material is thrown up and out of the resulting crater. The material usually falls back to the surface surrounding the crater. However, these ejecta deposits are not seen on Deimos, perhaps because the moon's gravity is so low that the ejecta escaped to space. Material does appear to have moved down slopes. Deimos also has a thick regolith, perhaps as deep as 100 m, formed as meteorites pulverized the surface.

Deimos is a dark body that appears to be composed of C-type surface materials, similar to that of asteroids found in the outer asteroid belt.

Discovery: Deimos was discovered on 11 August 1877 by Asaph Hall.

How Deimos Got its Name: Hall named Mars' moons for the mythological sons of Ares, the Greek counterpart of the Roman god, Mars. Deimos, whose name means dread, is the brother of Phobos.

Deimos: Facts

Deimos: Facts and Figures

Image Credit: NASA/JPL-Caltech/University of Arizona
Explanation from: http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Deimos

Moons of Mars: Phobos

Moons of Mars: Phobos

Phobos, gouged and nearly shattered by a giant impact crater and beaten by thousands of meteorite impacts, is on a collision course with Mars.

Phobos is the larger of Mars' two moons and is 27 by 22 by 18 km in diameter. It orbits Mars three times a day, and is so close to the planet's surface that in some locations on Mars it cannot always be seen.

Phobos is nearing Mars at a rate of 1.8 m every hundred years; at that rate, it will either crash into Mars in 50 million years or break up into a ring. Its most prominent feature is the 6-mile crater Stickney, its impact causing streak patterns across the moon's surface. Stickney was seen by Mars Global Surveyor to be filled with fine dust, with evidence of boulders sliding down its sloped surface.

Phobos and Deimos appear to be composed of C-type rock, similar to blackish carbonaceous chondrite asteroids. Observations by Mars Global Surveyor indicate that the surface of this small body has been pounded into powder by eons of meteoroid impacts, some of which started landslides that left dark trails marking the steep slopes of giant craters.

Measurements of the day and night sides of Phobos show such extreme temperature variations that the sunlit side of the moon rivals a pleasant winter day in Chicago, while only a few kilometers away, on the dark side of the moon, the climate is more harsh than a night in Antarctica. High temperatures for Phobos were measured at 25 degrees Fahrenheit (-4 degrees Celsius) and lows at -170 degrees Fahrenheit (-112 degrees Celsius). This intense heat loss is likely a result of the fine dust on Phobos' surface, which is unable to retain heat.

Phobos has no atmosphere. It may be a captured asteroid, but some scientists show evidence that contradicts this theory.

Discovery: Phobos was discovered on 17 August 1877 by Asaph Hall.

How Phobos Got its Name: Hall named Mars' moons for the mythological sons of Ares, the Greek counterpart of the Roman god, Mars. Phobos, whose name means fear or panic, is the brother of Deimos.

Phobos: Facts

Phobos: Facts and Figures

Image Credit: NASA/JPL/University of Arizona
Explanation from: http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos

April 13, 2015

What it would look like if Saturn-like planet was the same distance away from the Earth as the Moon is?

If Saturn was as close to Earth as the Moon
if saturn was as close as the moonif saturn was as close as moonif saturn as close as the moonif saturn were as close as the moonif saturn was the moonif saturn was moon

April 12, 2015

Horsehead Nebula Disappears in Infrared Light

Horsehead Nebula in Infrared Light
Horsehead Nebula in Infrared Light

Sometimes a horse of a different color hardly seems to be a horse at all, as, for example, in this released image from NASA's Spitzer Space Telescope. The famous Horsehead nebula makes a ghostly appearance on the far right side of the image, but is almost unrecognizable in this infrared view. In visible-light images, the nebula has a distinctively dark and dusty horse-shaped silhouette, but when viewed in infrared light, dust becomes transparent and the nebula appears as a wispy arc.

The Horsehead is only one small feature in the Orion Molecular Cloud Complex, dominated in the center of this view by the brilliant Flame nebula (NGC 2024). The smaller, glowing cavity falling between the Flame nebula and the Horsehead is called NGC 2023. These regions are about 1,200 light-years away.

The two carved-out cavities of the Flame nebula and NGC 2023 were created by the destructive glare of recently formed massive stars within their confines. They can be seen tracing a spine of glowing dust that runs through the image.

The Flame nebula sits adjacent to the star Alnitak, the easternmost star in Orion’s belt, seen here as the bright blue dot near the top of the nebula.

In this infrared image from Spitzer, blue represents light emitted at a wavelength of 3.6-microns, and cyan (blue-green) represents 4.5-microns, both of which come mainly from hot stars. Green represents 8-micron light and red represents 24-micron light. Relatively cooler objects, such as the dust of the nebulae, appear green and red. Some regions along the top and bottom of the image extending beyond Spitzer's observations were filled in using data from NASA's Wide-field Infrared Survey Explorer, or WISE, which covered similar wavelengths across the whole sky.

Image Credit: NASA/JPL-Caltech/ESO
Explanation from: http://www.nasa.gov/jpl/spitzer/horsehead-different-color/