Astronomy

A report published in the scientific journal Nature of results from the Cassini probe indicates the discovery of the existence of liquid water on Saturn’s moon Enceladus, and with it the possibility of extraterrestrial life.

Analysis of ice particles once thought to be emitted by geysers from the moon revealed the presence of sodium salt in the ice. As on Earth, the most plausible explanation of the presence of salt water is the prolonged contact of liquid water with mineral bearing rocks.

The currently understood scientific model of how life occurs requires the presence of three elements: the existence of complex organic molecules, liquid water and a source of energy. All three appear to be present on Enceladus.

The possibility of discovering a global ocean on the moon has receded, and has been replaced by the idea of large subterranean caverns with large pools or lakes of water, created by tidal forces acting upon Enceladus, and it is from these mist filled caverns that the water evaporates into the atmosphere in a steady jet. However, until further flybys and missions can be carried out other mechanisms for the presence of salt water ice cannot yet be dismissed.

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When the crew of the Space Shuttle Atlantis released the Hubble Space Telescope to return to orbit, concluding the final astronaut mission to upgrade and repair Hubble, astronomy fans around the world rejoiced. Hubble, renewed and equipped with new cameras, would now return to its work of revealing the universe.

But after the furor and high-profile feats of a servicing mission, Hubble sinks into silence. This time, a three-month hiatus will take place between the mission and any new images.

The quiet belies the intense activity going on behind the scenes. Engineers and scientists are conducting a slow, painstaking process of Servicing Mission Observatory Verification (SMOV) — bringing the telescope to full functionality, making the adjustments and gathering the information that will allow them to provide the best, clearest, cleanest images. Once that’s accomplished, Hubble will begin taking its Early Release Observations (EROs), images intended to demonstrate the telescope’s new technology. Read full entry »

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Hubble Space Telescope has been launched by the shuttle Discovery in 1990. It released into an orbit 304 nautical miles above the Earth. Since then it’s circled Earth more than 97,000 times and provided more than 4,000 astronomers access to the stars not possible from inside Earth’s atmosphere. Hubble has helped answer some of science’s key questions and provided images that have awed and inspired the world.

Since then, four shuttle missions has been flying to the telescope, to replacing and repairing failed and faulty components and added new and improved cameras and scientific equipment. Now the fifth and also last mission has done the same again. Atlantis spacecraft’s crew - launched on May 11 - has been successfully installing several new scientific instruments.

The Cosmic Origins Spectrograph will observe the light put out by extremely faint, far-away quasars and see how that light changes as it passes through the intervening gas between distant galaxies. In this way scientists will learn what that gas is made of, how it’s changed over time and how it affects the galaxies around it. New Wide Field Camera 3 (WFC3) will allow Hubble to take large-scale, extremely clear and detailed pictures over a very wide range of colors. At ultraviolet and infrared wavelengths the WFC3 represents a dramatic improvement in capability over all previous Hubble cameras. It is also a very capable visible light camera, though by design not quite as capable at visible wavelengths as Hubble’s Advanced Camera for Surveys (ACS). The WFC3 and ACS are designed to work together in a complementary fashion.

The new camera and spectrograph are designed to complement the scientific instruments already on the telescope – specifically the Advanced Camera for Surveys and the Space Telescope Imaging Spectrograph. But pieces of those instruments have failed in past years – not the entire instrument, but specific pieces inside of them. The crew will replace only the pieces that have failed.

NASA hopes the final service will keep the telescope operate for another five to 10 years, before it is steered to reenter earth’s atmosphere and plunges into the ocean. A sad ending actually, for such a precious and one of the greatest scientific instruments ever built.

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Over the past 19 years Hubble has taken dozens of exotic pictures of galaxies going “bump in the night” as they collide with each other and have a variety of close encounters of the galactic kind. Just when you thought these interactions couldn’t look any stranger, this image of a trio of galaxies, called Arp 194, looks as if of the galaxies has sprung a leak. The bright blue streamer is really a stretched spiral arm full of newborn blue stars. This typically happens when two galaxies interact and gravitationally tug at each other gravitationally.

This interacting group contains several galaxies, along with a “cosmic fountain” of stars, gas and dust that stretches over 100,000 light years. Resembling a pair of owl’s eyes, the two nuclei of the colliding galaxies can be seen in the process of merging at the upper left. The bizarre blue bridge of material extending out from the northern component looks as if it connects to a third galaxy but in reality the galaxy is in the background and not connected at all. The blue “fountain” is the most striking feature of this galaxy troupe and it contains complexes of super star clusters that may have as many as dozens of individual young star clusters in them.

Resembling a pair of owl’s eyes, the two nuclei of the colliding galaxies can be seen in the process of merging at the upper left. The bizarre blue bridge of material extending out from the northern component looks as if it connects to a third galaxy but in reality this galaxy is in the background and not connected at all. Hubble’s sharp view allows astronomers to try and sort out visually which are the foreground and background objects when galaxies, superficially, appear to overlap.

The blue “fountain” is the most striking feature of this galaxy troupe and it contains complexes of super star clusters that may have as many as dozens of individual young star clusters in them. It formed as a result of the interactions among the galaxies in the northern component of Arp 194. The gravitational forces involved in a galaxy interaction can enhance the star formation rate and give rise to brilliant bursts of star formation in merging systems.

Arp 194, located in the constellation of Cepheus, resides approximately 600 million light-years away from Earth. Arp 194 is one of thousands of interacting and merging galaxies known in our nearby Universe. These observations were taken in January 2009 with the Wide Field Planetary Camera 2. Blue, green and red filters were composited together to form this rather picturesque image of a galaxy interaction.

This picture was issued to celebrate the 19th anniversary of the launch of the Hubble Space Telescope. Since its launch aboard the space shuttle Discovery in 1990, Hubble has made more than 880.000 observations and snapped over 570.000 images of 29.000 celestial objects over the past 19 years.

Image Credits: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

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The most crowded collision of galaxy clusters has been identified by combining information from three different telescopes. This result gives scientists a chance to learn what happens when some of the largest objects in the universe go at each other in a cosmic free-for-all. Using data from NASA’s Chandra X-ray Observatory, Hubble Space Telescope, and the Keck Observatory in Hawaii, astronomers were able to determine the three-dimensional geometry and motion in the system MACS J0717.5+3745 (or MACS J0717, for short), located about 5.4 billion light-years from Earth.

This composite image showing MACS J0717, where four separate galaxy clusters have been involved in a collision — the first time such a phenomenon has been documented. Hot gas is shown in an image from NASA’s Chandra X-ray Observatory, and galaxies are shown in an optical image from NASA’s Hubble Space Telescope. The hot gas is color-coded to show temperature, where the coolest gas is reddish purple, the hottest gas is blue, and the temperatures in between are purple.

The repeated collisions in MACS J0717 are caused by a 13-million-light-year-long stream of galaxies, gas, and dark matter — known as a filament — pouring into a region already full of matter. A collision between the gas in two or more clusters causes the hot gas to slow down. However, the massive and compact galaxies do not slow down as much as the gas does, and so move ahead of it. Therefore, the speed and direction of each cluster’s motion — perpendicular to the line of sight — can be estimated by studying the offset between the average position of the galaxies and the peak in the hot gas.

MACS J0717 is located about 5.4 billion light-years from Earth. It is one of the most complex galaxy clusters ever seen. Other well-known clusters, like the Bullet Cluster and MACS J0025.4-1222, involve the collision of only two galaxy clusters and show much simpler geometry.

Image credits: NASA, ESA, CXC, C. Ma, H. Ebeling, and E. Barrett (University of Hawaii/IfA), et al., and STScI

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NASA recently publish first images (or “first lights”, as astronomer says) taken from Kepler spacecraft. It is the mission specifically designed to survey our region of the Milky Way galaxy to discover hundreds of Earth-size and smaller planets in or near the habitable zone and determine the fraction of the hundreds of billions of stars in our galaxy that might have such planets.

These pictures are taken just at the day after cover release. It shows a glittering array of millions of stars stretching across the field of view. Also in the field are star clusters, background galaxies beyond the Milky Way and three stars that are known to have “hot Jupiters” orbiting them. Kepler will observe these stars for an early confirmation of the planet detection capability of the analysis software to be used on all of Kepler’s target stars.

Analysis of the images taken over the past several days shows that the telescope is well within the focus requirements levied on the instrument. The data were taken under stable temperature conditions and with the spacecraft in the highest pointing stability mode, called fine point. Engineers are now working with the science team to determine whether optimizing the focus further would provide a significant improvement in science return. If so, the 1.4-meter (55-inch) primary mirror assembly will be adjusted to fine-tune the alignment.

Launched on March 6, 2009, the scientific goal of the Kepler Mission is to explore the structure and diversity of planetary systems, with a special emphasis on the detection of Earth-size planets. It will survey the extended solar neighborhood to detect and characterize hundreds of terrestrial and larger planets in or near the “habitable zone,” defined by scientists as the distance from a star where liquid water can exist on a planet’s surface. The results will yield a broad understanding of planetary formation, the frequency of formation, the structure of individual planetary systems, and the generic characteristics of stars with terrestrial planets.

Some of the first images from Kepler can be found here.

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Physicist John Wheeler is widely credited with coining the term black hole in his 1967 public lecture Our Universe: the Known and Unknown. He used the term to avoid him repeatedly using sentence “gravitationally completely collapsed star” on his lecture. However, Wheeler insisted that someone else at the conference had coined the term and he had merely adopted it as useful shorthand.

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Sometimes objects in the sky that appear strange, or different from normal, have a story to tell and prove scientifically very rewarding. This was the idea behind Halton Arp’s catalogue of Peculiar Galaxies that appeared in the 1960s. One of the oddballs listed there is Arp 261, which has now been imaged in more detail than ever before using the FORS2 instrument on ESO’s Very Large Telescope. The image proves to contain several surprises.

Arp 261 lies about 70 million light-years distant in the constellation of Libra, the Scales. Its chaotic and very unusual structure is created by the interaction of two galaxies that are engaged in a slow motion, but highly disruptive close encounter. Although individual stars are very unlikely to collide in such an event, the huge clouds of gas and dust certainly do crash into each other at high speed, leading to the formation of bright new clusters of very hot stars that are clearly seen in the picture. The paths of the existing stars in the galaxies are also dramatically disrupted, creating the faint swirls extending to the upper left and lower right of the image. Both interacting galaxies were probably dwarfs not unlike the Magellanic Clouds orbiting our own galaxy.

The images used to create this picture were not actually taken to study the interacting galaxies at all, but to investigate the properties of the inconspicuous object just to the right of the brightest part of Arp 261 and close to the centre of the image. This is an unusual exploding star, called SN 1995N, that is thought to be the result of the final collapse of a massive star at the end of its life, a so-called core collapse supernova. SN 1995N is unusual because it has faded very slowly — and still shows clearly on this image more than seven years after the explosion took place! It is also one of the few supernovae to have been observed to emit X-rays. It is thought that these unusual characteristics are a result of the exploding star being in a dense region of space so that the material blasted out from the supernova ploughs into it and creates X-rays.

Apart from the interacting galaxy and its supernova the image also contains several other objects at wildly different distances from us. Starting very close to home, two small asteroids, in our Solar System between the orbits of Mars and Jupiter, happened to cross the images as they were being taken and show up as the red-green-blue trails at the left and top of the picture. The trails arise as the objects are moving during the exposures and also between the exposures through different coloured filters. The asteroid at the top is number 14670 and the one to the left number 9735. They are probably less than 5 km across. The reflected sunlight from these small bodies takes about fifteen minutes to get to the Earth.

The next closest object is probably the apparently bright star at the bottom. It may look bright, but it is still about one hundred times too faint to be seen with the unaided eye. It is most likely a star rather like the Sun and about 500 light-years from us — 20 million times further away than the asteroids. Arp 261 itself, and the supernova, are about 140 000 times further away again than this star, but still in what astronomers would regard as our cosmic neighbourhood. Much more distant still, perhaps some fifty to one hundred times further away than Arp 261, lies the cluster of galaxies visible on the right of the picture. There is no doubt, however, that a much more remote object lies, unrecognised, amongst the faint background objects seen in this marvellous image. (Image credit: ESO)

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On Oct. 5, 2008, just after coming within 25 kilometers (15.6 miles) of the surface of Enceladus, NASA’s Cassini captured this stunning mosaic as the spacecraft sped away from this geologically active moon of Saturn.

Craters and cratered terrains are rare in this view of the southern region of the moon’s Saturn-facing hemisphere. Instead, the surface is replete with fractures, folds, and ridges–all hallmarks of remarkable tectonic activity for a relatively small world. In this enhanced-color view, regions that appear blue-green are thought to be coated with larger grains than those that appear white or gray. Near the top, the conspicuous ridges are Ebony and Cufa Dorsae. Portions of the tiger stripe fractures, or sulci, are visible along the terminator at lower right, surrounded by a circumpolar belt of mountains. The icy moon’s famed jets emanate from at least eight distinct source regions, which lie on or near the tiger stripes. However, in this view, the most prominent feature is Labtayt Sulci, the approximately one-kilometer (0.6 miles) deep northward-trending chasm located just above the center of the mosaic.

This false-color mosaic was created from 28 images obtained at seven footprints, or pointing positions, by Cassini’s narrow-angle camera. At each footprint, four images using filters sensitive to ultraviolet, visible and infrared light (spanning wavelengths from 338 to 930 nanometers) were combined to create the individual frames. The mosaic is an orthographic projection centered at 64.49 degrees south latitude, 283.87 west longitude, and it has an image scale of 196 kilometers (122.5 miles) per pixel. The original images ranged in resolution from 180 meters (594 feet) to 288 meters (950 feet) per pixel and were acquired at distances ranging from 30,000 to 48,000 kilometers (18,750 to 30,000 miles) as the spacecraft receded from Enceladus. The view was acquired at a Sun-Enceladus-spacecraft, or phase, angle of 73 degrees. (credits: NASA/JPL/Space Science Institute)

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Galaxies and the giant black holes at their hubs fit together as if they were made for one another. Did the holes come first and guide the formation of their galaxies, did the galaxies come first and build up holes, or did some common factor sculpt both?

As reported on March 2009 edition of Scientific American Magazine, Christopher Carilli of the National Radio Astronomy Observatory and his colleagues argued that the holes came first. On the American Astronomical Society meeting in January they presenting their finding that galaxies in the early universe were 30 times more massive than their black holes, whereas present-day galaxies are 1,000 time heavier. “Black holes came first and somehow—we don’t know how—grew the galaxy around them,” Carilli said.

Other astronomers were skeptical, wondering whether the ancient galaxies seem undersized merely because of a statistical selection effect. Even if true, the study does not explain how a black hole can nurture a galaxy; if anything, it should tear it apart.

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