June 28, 2013

Three Planets in Habitable Zone of Nearby Star

A team of astronomers has combined new observations of Gliese 667C with existing data from HARPS at ESO’s 3.6-metre telescope in Chile, to reveal a system with at least six planets. A record-breaking three of these planets are super-Earths lying in the zone around the star where liquid water could exist, making them possible candidates for the presence of life. This is the first system found with a fully packed habitable zone.

Gliese 667C is a very well-studied star. Just over one third of the mass of the Sun, it is part of a triple star system known as Gliese 667 (also referred to as GJ 667), 22 light-years away in the constellation of Scorpius (The Scorpion). This is quite close to us — within the Sun’s neighbourhood — and much closer than the star systems investigated using telescopes such as the planet-hunting Kepler space telescope.

Previous studies of Gliese 667C had found that the star hosts three planets with one of them in the habitable zone. Now, a team of astronomers led by Guillem Anglada-Escudé of the University of Göttingen, Germany and Mikko Tuomi of the University of Hertfordshire, UK, has reexamined the system. They have added new HARPS observations, along with data from ESO's Very Large Telescope, the W.M. Keck Observatory and the Magellan Telescopes, to the already existing picture. The team has found evidence for up to seven planets around the star. 

These planets orbit the third fainter star of a triple star system. Viewed from one of these newly found planets the two other suns would look like a pair of very bright stars visible in the daytime and at night they would provide as much illumination as the full Moon. The new planets completely fill up the habitable zone of Gliese 667C, as there are no more stable orbits in which a planet could exist at the right distance to it. 

“We knew that the star had three planets from previous studies, so we wanted to see whether there were any more,” says Tuomi. “By adding some new observations and revisiting existing data we were able to confirm these three and confidently reveal several more. Finding three low-mass planets in the star’s habitable zone is very exciting!”

Three of these planets are confirmed to be super-Earths — planets more massive than Earth, but less massive than planets like Uranus or Neptune — that are within their star’s habitable zone, a thin shell around a star in which water may be present in liquid form if conditions are right. This is the first time that three such planets have been spotted orbiting in this zone in the same system.

“The number of potentially habitable planets in our galaxy is much greater if we can expect to find several of them around each low-mass star — instead of looking at ten stars to look for a single potentially habitable planet, we now know we can look at just one star and find several of them,” adds co-author Rory Barnes (University of Washington, USA).

Compact systems around Sun-like stars have been found to be abundant in the Milky Way. Around such stars, planets orbiting close to the parent star are very hot and are unlikely to be habitable. But this is not true for cooler and dimmer stars such as Gliese 667C. In this case the habitable zone lies entirely within an orbit the size of Mercury's, much closer in than for our Sun. The Gliese 667C system is the first example of a system where such a low-mass star is seen to host several potentially rocky planets in the habitable zone.

The ESO scientist responsible for HARPS, Gaspare Lo Curto, remarks: “This exciting result was largely made possible by the power of HARPS and its associated software and it also underlines the value of the ESO archive. It is very good to also see several independent research groups exploiting this unique instrument and achieving the ultimate precision.”

And Anglada-Escudé concludes: “These new results highlight how valuable it can be to re-analyse data in this way and combine results from different teams on different telescopes.”

Image Credit: ESO/M. Kornmesser
Explanation from: http://www.eso.org/public/news/eso1328/

June 27, 2013

Hubble Reveals the Ring Nebula's True Shape

In this composite image, visible-light observations by NASA's Hubble Space Telescope are combined with infrared data from the ground-based Large Binocular Telescope in Arizona to assemble a dramatic view of the well-known Ring Nebula.

Called a planetary nebula, the Ring Nebula is the glowing remains of a Sun-like star.

The object is tilted toward Earth so that astronomers see the ring face-on. The Hubble observations reveal that the nebula's shape is more complicated than astronomers thought. The blue gas in the nebula's center is actually a football-shaped structure that pierces the red doughnut-shaped material. Hubble also uncovers the detailed structure of the dark, irregular knots of dense gas embedded along the inner rim of the ring. The knots look like spokes in a bicycle. The Hubble images have allowed the research team to match up the knots with the spikes of light around the bright, main ring, which are a shadow effect.

The faint, scallop-shaped material surrounding the ring was expelled by the star during the early stages of the planetary nebula formation. This outer material was imaged by the Large Binocular Telescope.

Most Sun-like stars become planetary nebulae at the end of their lives. Once a star consumes all of its hydrogen, the nuclear fuel that makes it shine, it expands to a red giant. The bloated star then expels its outer layers, exposing its hot core. Ultraviolet radiation from the core illuminates the discarded material, making it glow. The smoldering core, called a white dwarf, is the tiny white dot in the center of the Ring Nebula.

The Ring Nebula is about 2,000 light-years away in the constellation Lyra. The nebula measures roughly one light-year across.

The Hubble observations were taken Sept. 19, 2011, by the Wide Field Camera 3. The Large Binocular Telescope data were taken June 6, 2010. In the image, the blue color represents helium; the green, oxygen; and the red, hydrogen.

Image Credit: NASA, ESA, C.R. O'Dell (Vanderbilt University), and D. Thompson (Large Binocular Telescope Observatory)
Explanation from: http://hubblesite.org/newscenter/archive/releases/2013/13/image/a/

Blue Marble Google Edition

Google said:

"To celebrate the sunny days of summer (in the northern hemisphere at least), today we're launching new satellite imagery for Google’s mapping products. This stunning global view is virtually cloud-free and includes refreshed imagery in more locations—giving you an even more accurate and comprehensive view of our planet's landscape. 

Our satellite imagery is usually created like a quilt: we stitch together imagery of different parts of the world. Using a process similar to how we produced the global time-lapse imagery of the Earth, we took hundreds of terabytes of data from the USGS's and NASA’s Landsat 7 satellite—sometimes dozens of photos of a single spot in the world—and analyzed the photos to compute a clear view of every place, even in tropical regions that are always at least partly cloudy.

The result is a single, beautiful 800,000 megapixel image of the world, which can be viewed in Earth and Maps when you're zoomed out to a global view. This global image is so big, if you wanted to print it at a standard resolution of 300 dots per inch you’d need a piece of paper the size of a city block! This image is then blended into our highest resolution imagery, giving a beautiful cloud-free global view and detailed images in the same seamless map."

Image Credit: NASA, USGS, Landsat 7 and Google
Explanation from: http://googleblog.blogspot.co.uk/2013/06/only-clear-skies-on-google-maps-and.html

June 26, 2013

Sunrise over the South Pacific Ocean

The Sun is about to come up over the South Pacific Ocean in this colorful scene photographed by one of the Expedition 35 crew members aboard the Earth-orbiting International Space Station between 4 and 5 a.m. local time, May 5, 2013.

The space station was at a point above Earth located at 27.4 degrees south latitude and 110.1 degrees west longitude, a few hundred miles east of Easter Island.

Image Credit: NASA
Explanation from: http://www.nasa.gov/multimedia/imagegallery/image_feature_2505.html

June 25, 2013

Colliding Galaxy Pair

This striking NASA Hubble Space Telescope image, which shows what looks like the profile of a celestial bird, belies the fact that close encounters between galaxies are a messy business.

This interacting galaxy duo is collectively called Arp 142. The pair contains the disturbed, star-forming spiral galaxy NGC 2936, along with its elliptical companion, NGC 2937 at lower left.

Once part of a flat, spiral disk, the orbits of the galaxy's stars have become scrambled due to gravitational tidal interactions with the other galaxy. This warps the galaxy's orderly spiral, and interstellar gas is strewn out into giant tails like stretched taffy.

Gas and dust drawn from the heart of NGC 2936 becomes compressed during the encounter, which in turn triggers star formation. These bluish knots are visible along the distorted arms that are closest to the companion elliptical. The reddish dust, once within the galaxy, has been thrown out of the galaxy's plane and into dark veins that are silhouetted against the bright starlight from what is left of the nucleus and disk.

The companion elliptical, NGC 2937, is a puffball of stars with little gas or dust present. The stars contained within the galaxy are mostly old, as evidenced by their reddish color. There are no blue stars that would be evidence of recent star formation. While the orbits of this elliptical's stars may be altered by the encounter, it's not apparent that the gravitational pull by its neighboring galaxy is having much of an effect.

Image Credit: NASA/ESA/Hubble Heritage Team
Explanation from: http://www.nasa.gov/multimedia/imagegallery/image_feature_2536.html