Friday, November 30, 2012

lanck spots hot gas bridging galaxy cluster pair



Galaxy clusters connected by gas bridge
ESA’s Planck space telescope has made the first conclusive detection of a bridge of hot gas connecting a pair of galaxy clusters across 10 million light-years of intergalactic space.

Planck’s primary task is to capture the most ancient light of the cosmos, the Cosmic Microwave Background, or CMB. As this faint light traverses the Universe, it encounters different types of structure including galaxies and galaxy clusters – assemblies of hundreds to thousands of galaxies bound together by gravity.

If the CMB light interacts with the hot gas permeating these huge cosmic structures, its energy distribution is modified in a characteristic way, a phenomenon known as the Sunyaev–Zel’dovich (SZ) effect, after the scientists who discovered it.
This effect has already been used by Planck to detect galaxy clusters themselves, but it also provides a way to detect faint filaments of gas that might connect one cluster to another.
In the early Universe, filaments of gaseous matter pervaded the cosmos in a giant web, with clusters eventually forming in the densest nodes.
Much of this tenuous, filamentary gas remains undetected, but astronomers expect that it could most likely be found between interacting galaxy clusters, where the filaments are compressed and heated up, making them easier to spot.
Planck’s discovery of a bridge of hot gas connecting the clusters Abell 399 and Abell 401, each containing hundreds of galaxies, represents one such opportunity.
The presence of hot gas between the billion-light-year-distant clusters was first hinted at in X-ray data from ESA’s XMM-Newton, and the new Planck data confirm the observation.
It also marks Planck’s first detection of inter-cluster gas using the SZ effect technique.
By combining the Planck data with archival X-ray observations from the German satellite Rosat, the temperature of the gas in the bridge is found to be similar to the temperature of the gas in the two clusters – on the order of 80 million degrees Celsius.
Early analysis suggests the gas could be mixture of the elusive filaments of the cosmic web mixed with gas originating from the clusters.
A more detailed analysis and the possible detection of gas bridges connecting other clusters will help to provide a more conclusive answer.
The new finding highlights the ability of Planck to probe galaxy clusters to their outskirts and beyond, examining their connection with the gas that permeates the entire Universe and from which all groups of galaxies formed.  
 

Sunday, November 25, 2012

Born-again star foreshadows fate of Solar System


Abell 30: a born-again planetary nebula

Astronomers have found evidence for a dying Sun-like star coming briefly back to life after casting its gassy shells out into space, mimicking the possible fate our own Solar System faces in a few billion years.
 
This new picture of the planetary nebula Abell 30, located 5500 light-years from Earth, is a composite of visible images from the NASA/ESA Hubble Space Telescope and X-ray data from ESA’s XMM-Newton and NASA’s Chandra space telescopes.
‘Planetary nebula’ is the name given to the often-concentric shells of stellar material cast into space by dying stars. To astronomers of the 18th century, these objects looked like the colourful ‘blob’ of a planet through their telescopes, and the name stuck.
Astronomers now know that as a star with less than eight times the mass of the Sun swells into a red giant towards the end of its life, its outer layers are expelled via pulsations and winds.
Ultraviolet radiation shining out from the stripped-down hot stellar core then lights up the ejected shells, resulting in intricate artworks that can be seen by modern telescopes.
The star at the heart of Abell 30 experienced its first brush with death
12 500 years ago – as seen from Earth – when its outer shell was stripped off by a slow and dense stellar wind.
Optical telescopes see the remnant of this evolutionary stage as a large, near-spherical shell of glowing material expanding out into space.
Then, about 850 years ago, the star suddenly came back to life, coughing out knots of helium and carbon-rich material in a violent event.
The star’s outer envelope briefly expanded during this born-again episode, but then very rapidly contracted again within 20 years.
This had the knock-on effect of accelerating the wind from the star to its present speed of 4000 kilometers per second – over 14 million kilometers per hour.
As this fast stellar wind catches up and interacts with the slower wind and clumps of previously ejected material, complex structures are formed, including the delicate comet-like tails seen near the central star in this image.
The stellar wind bombarding dense clumps of material provides a chilling look at the possible fate of Earth and its fellow planets in our own Solar System in a few billion years’ time.
When our Sun emits its final gasps of life at the heart of a planetary nebula, its strong stellar wind and harsh radiation will blast and evaporate any planets that may have survived the red giant phase of stellar evolution.
If any distant civilization is watching with high-power telescopes at the time, they might see the glowing embers of the planets light up in X-rays as they are engulfed in the stellar wind.  
 

Wednesday, November 21, 2012

Lanka’s inaugural satellite launch on Thursday


The much awaited Sri Lanka’s inaugural and the regions third communication satellite launch would take place 2012.11.22 Thursday from Beijing China at 3 30 p.m. Sri Lankan time. The Supreme Group is a fast growing Sri Lankan home grown company with a special focus on Sri Lanka and regional satellite communication opportunities. They have already invested US $ 100 million.
Chairman, Supreme Group, R. M. Manivannan (inset) and images of the satellite being installed in China
In addition they had already invested US $ 20 million for a satellite training and transmitting station in Kandy. The funds for this historic venture are being mobilized through MIL Bank.
Chairman, Supreme Group, R. M. Manivannan speaking to Daily News Business said that they would further invest US $ 60 million next year for further development of the project.
“Our main strength and revenue base is bulk commodity trading which includes large scale contracts of urea, coal, bitumen, PVC, iron ore. In addition we are also involved in reinsurance, investments, oil exploration, mining and consultancy. After the huge success the company enjoyed doing large scale regional business, we wanted to do something big and beneficial to Sri Lanka and this is the reason we decided to launch a satellite for Sri Lanka.”
“Being a patriot this launch of the satellite would once again prove that “nothing is impossible” for a Sri Lankan.”Subsequent to the launch in China the satellite would be positioned right over Sri Lanka and after programming it would be ready by early next year. Manivannan said he has opened doors for a new industry in Sri Lanka and this will trigger a positive attitude especially within the private sector and investor community thus brings in similar large scale, Sri Lankan initiated innovative projects into Sri Lanka.”
“When we made our initial efforts to design, manufacture and launch a satellite owned by us, none of the western manufacturers took us seriously and we have proved our critics wrong by scheduling the launch of the satellite on Thursday.”
With the capital raised and firm plans in place, it was still an uphill task to find the suitable partner who would be willing to offer us the technology support. This is when we contacted the Chinese state owned, China Great Wall Industry Corporation who was a tower of strength for this operation,” he said.
“This project, while commercially creating a whole new industry in Sri Lanka, and would also bring in a total of US $ 320 million within the next three to five years. In addition there will be foreign exchange earnings along with high technology employment generation.”
He also said in a few months the local telecommunication and TV viewing industry would see a major transformation with numerous benefits being offered to them for better quality and lower price.
“Eventually this will lead to technology transfer and we can provide employment and a knowledge base to Sri Lankans who wish to venture into the space industry.”

Tuesday, November 20, 2012

Orbiting in the Habitable Zone of Two Suns



This diagram compares our own solar system to Kepler-47, a double-star system containing two planets, one orbiting in the so-called "habitable zone." This is the sweet spot in a planetary system where liquid water might exist on the surface of a planet.

Unlike our own solar system, Kepler-47 is home to two stars. One star is similar to the sun in size, but only 84 percent as bright. The second star is diminutive, measuring only one-third the size of the sun and less than one percent as bright. As the stars are smaller than our sun, the systems habitable zone is closer in.

The habitable zone of the system is ring-shaped, centered on the larger star. As the primary star orbits the center of mass of the two stars every 7.5 days, the ring of the habitable zone moves around.

This artist's rendering shows the planet comfortably orbiting within the habitable zone, similar to where Earth circles the sun. One year, or orbit, on Kepler-47c is 303 days. While not a world hospitable for life, Kepler-47c is thought to be a gaseous giant, slightly larger than Neptune, where an atmosphere of thick bright water-vapor clouds might exist.

The discovery demonstrates the diversity of planetary systems in our galaxy and provides more opportunities to search for life as we know it.


Sunday, November 18, 2012

Hubble Sees an Unexpected Population of Young-Looking Stars



 

The NASA/ESA Hubble Space Telescope offers an impressive view of the center of globular cluster NGC 6362. The image of this spherical collection of stars takes a deeper look at the core of the globular cluster, which contains a high concentration of stars with different colors.

Tightly bound by gravity, globular clusters are composed of old stars, which, at around 10 billion years old, are much older than the sun. These clusters are fairly common, with more than 150 currently known in our galaxy, the Milky Way, and more which have been spotted in other galaxies.

Globular clusters are among the oldest structures in the Universe that are accessible to direct observational investigation, making them living fossils from the early years of the cosmos.

Astronomers infer important properties of globular clusters by looking at the light from their constituent stars. For many years, they were regarded as ideal laboratories for testing the standard stellar evolution theory. Among other things, this theory suggests that most of the stars within a globular cluster should be of a similar age.

Recently, however, high precision measurements performed in numerous globular clusters, primarily with the Hubble Space Telescope, have led some to question this widely accepted theory. In particular, certain stars appear younger and bluer than their companions, and they have been dubbed blue stragglers. NGC 6362 contains many of these stars.

Since they are usually found in the core regions of clusters, where the concentration of stars is large, the most likely explanation for this unexpected population of objects seems to be that they could be either the result of stellar collisions or transfer of material between stars in binary systems. This influx of new material would heat up the star and make it appear younger than its neighbors.

NGC 6362 is located about 25 000 light-years from Earth in the constellation of Ara (The Altar). British astronomer James Dunlop first observed this globular cluster on 30 June 1826.

This image was created combining ultraviolet, visual and infrared images taken with the Wide Field Channel of the Advanced Camera for Surveys and the Wide Field Camera 3. An image of NGC 6362 taken by the MPG/ESO 2.2-meter telescope will be published by the European Southern Observatory on Wednesday.



Friday, November 16, 2012

Sun Releases Slow Moving CME



On the left is an image of a CME from Nov. 9, 2012, as captured by the joint ESA/NASA Solar Heliospheric Observatory (SOHO) at 10:48 a.m. EST. The CME can be seen as the light band that appears to be spreading away from the dark disk at the center, which is used to block the bright light from the sun in order to observe the dimmer solar atmosphere. The right image is what’s called a “difference” image, which helps highlights recent changes in any given image, thus making the CME stand out. Credit: ESA&NASA/SOHO/GSFC

On Nov. 9, 2012, at 10:24 a.m. EST, the sun emitted an Earth-directed coronal mass ejection (CME). A CME is a solar phenomenon that can send billions of tons of solar particles into space and can reach Earth one to three days later. CMEs can affect electronic systems in satellites and on the ground.


Experimental NASA research models based on observations from NASA's Solar Terrestrial Relations Observatory (STEREO) and the joint ESA/NASA Solar Heliospheric Observatory (SOHO) show that the CME left the sun traveling at 350 miles per second, which is a slow to average speed for CMEs.



Geomagnetic storms can occur when certain types of CMEs connect up with the outside of the Earth's magnetic envelope, the magnetosphere, for an extended period of time. In the past CMEs of this magnitude have tended to have a relatively weak impact, perhaps causing auroras near the poles, but not causing damage to electrical systems on Earth or interfering with GPS or satellite-based communications systems.



Tuesday, November 13, 2012

Asteroid Belts of Just the Right Size are Friendly to Life


Solar systems with life-bearing planets may be rare if they are dependent on the presence of asteroid belts of just the right mass, according to a study by Rebecca Martin, a NASA Sagan Fellow from the University of Colorado in Boulder, and astronomer Mario Livio of the Space Telescope Science Institute in Baltimore, Md.


They suggest that the size and location of an asteroid belt, shaped by the evolution of the sun's protoplanetary disk and by the gravitational influence of a nearby giant Jupiter-like planet, may determine whether complex life will evolve on an Earth-like planet.

This might sound surprising because asteroids are considered a nuisance due to their potential to impact Earth and trigger mass extinctions. But an emerging view proposes that asteroid collisions with planets may provide a boost to the birth and evolution of complex life.

Asteroids may have delivered water and organic compounds to the early Earth. According to the theory of punctuated equilibrium, occasional asteroid impacts might accelerate the rate of biological evolution by disrupting a planet's environment to the point where species must try new adaptation strategies.

The astronomers based their conclusion on an analysis of theoretical models and archival observations of extrasolar Jupiter-sized planets and debris disks around young stars. "Our study shows that only a tiny fraction of planetary systems observed to date seem to have giant planets in the right location to produce an asteroid belt of the appropriate size, offering the potential for life on a nearby rocky planet," said Martin, the study's lead author. "Our study suggests that our solar system may be rather special."

The findings will appear today in the Monthly Notices of the Royal Astronomical Society.

This illustration shows three possible scenarios for the evolution of asteroid belts. In the top panel, a Jupiter-size planet migrates through the asteroid belt, scattering material and inhibiting the formation of life on planets. The second scenario shows our solar-system model: a Jupiter-size planet that moves slightly inward but is just outside the asteroid belt. In the third illustration, a large planet does not migrate at all, creating a massive asteroid belt. Material from the hefty asteroid belt would bombard planets, possibly preventing life from evolving.  (Credit: NASA/ESA/A. Feild, STScI)


Martin and Livio suggest that the location of an asteroid belt relative to a Jupiter-like planet is not an accident. The asteroid belt in our solar system, located between Mars and Jupiter, is a region of millions of space rocks that sits near the “snow line," which marks the border of a cold region where volatile material such as water ice are far enough from the sun to remain intact. At the time when the giant planets in our solar system were forming, the region just beyond the snow line contained a dense mix of ices, rock and metals that provided enough material to build giant planets like Jupiter.

When Jupiter formed just beyond the snow line, its powerful gravity prevented nearby material inside its orbit from coalescing and building planets. Instead, Jupiter's influence caused the material to collide and break apart. These fragmented rocks settled into an asteroid belt around the sun.

"To have such ideal conditions you need a giant planet like Jupiter that is just outside the asteroid belt [and] that migrated a little bit, but not through the belt,” Livio explained. "If a large planet like Jupiter migrates through the belt, it would scatter the material. If, on the other hand, a large planet did not migrate at all, that, too, is not good because the asteroid belt would be too massive. There would be so much bombardment from asteroids that life may never evolve."

In fact, during the solar system's infancy, the asteroid belt probably had enough material to make another Earth, but Jupiter's presence and its small migration towards the sun caused some of the material to scatter. Today, the asteroid belt contains less than one percent of its original mass. Using our solar system as a model, Martin and Livio proposed that asteroid belts in other solar systems would always be located approximately at the snow line. To test their proposal, Martin and Livio created models of protoplanetary disks around young stars and calculated the location of the snow line in those disks based on the mass of the central star.

They then looked at all the existing space-based infrared observations from NASA’s Spitzer Space Telescope of 90 stars having warm dust, which could indicate the presence of an asteroid belt-like structure. The temperature of the warm dust was consistent with that of the snow line. "The warm dust falls right onto our calculated snow lines, so the observations are consistent with our predictions," Martin said.

The duo then studied observations of the 520 giant planets found outside our solar system. Only 19 of them reside outside the snow line, suggesting that most of the giant planets that may have formed outside the snow line have migrated too far inward to preserve the kind of slightly-dispersed asteroid belt needed to foster enhanced evolution of life on an Earth-like planet near the belt. Apparently, less than four percent of the observed systems may actually harbor such a compact asteroid belt.

"Based on our scenario, we should concentrate our efforts to look for complex life in systems that have a giant planet outside of the snow line," Livio said.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.


Saturday, November 10, 2012

Hubble Sees Violent Star Formation Episodes in Dwarf Galaxies



The NASA/ESA Hubble Space Telescope has imaged the faint irregular galaxy NGC 3738, a starburst galaxy. The galaxy is in the midst of a violent episode of star formation, during which it is converting reservoirs of hydrogen gas located in the galaxy’s center into stars. Hubble spots this gas glowing red around NGC 3738, one of the most distinctive signs of ongoing star formation.
Lying in the constellation of Ursa Major (The Great Bear), NGC 3738 is located about 12 million light-years from the sun, and belongs to the Messier 81 group of galaxies. This galaxy — first observed by astronomer William Herschel back in 1789 — is a nearby example of a blue compact dwarf, the faintest type of starburst galaxy. Blue compact dwarfs are small compared to large spiral galaxies — NGC 3738 is around 10,000 light-years across, just one tenth of the size of the Milky Way.

This type of galaxy is blue in appearance by virtue of containing large clusters of hot, massive stars, which ionize the surrounding interstellar gas with their intense ultraviolet radiation. They are relatively faint and appear to be irregular in shape. Unlike spirals or elliptical galaxies, irregular galaxies do not have any distinctive features, such as a nuclear bulge or spiral arms. Rather, they are extremely chaotic in appearance. These galaxies are thought to resemble some of the earliest that formed in the Universe and may provide clues as to how stars appeared shortly after the Big Bang.

This image was created by combining visual and infrared images taken with the Wide Field Channel of the Advanced Camera for Surveys aboard the Hubble Space Telescope. The field of view of the Wide Field Channel is approximately 3.4 by 3.4 arcminutes wide.

Saturday, November 3, 2012

Monster Galaxy May Have Been Stirred Up By Black-hole Mischief


The giant elliptical galaxy in the center of this Hubble image is the most massive and brightest member of the galaxy cluster Abell 2261. Spanning a little more than one million light-years,the galaxy is about 10 times the diameter of our Milky Way galaxy. The bloated galaxy is a member of an unusual class of galaxies with a diffuse core filled with a fog of starlight. Abell 2261 is located three billion light-years away. The observations were taken March to May 2011. Credit: NASA; ESA; M. Postman, STScI; T. Lauer, NOAO, Tucson; CLASH team.
Astronomers using NASA's Hubble Space Telescope have obtained a remarkable new view of a whopper of an elliptical galaxy that may have been puffed up by the actions of one or more black holes in its core.

Spanning a little more than one million light-years, the galaxy is about 10 times the diameter of our Milky Way galaxy. The bloated galaxy is a member of an unusual class of galaxies with a diffuse core filled with a fog of starlight where there would normally be a concentrated peak of light around a central black hole. Viewing the core is like seeing a city with no downtown, just houses sprinkled across a vast landscape.

Astronomers used Hubble's Advanced Camera for Surveys and Wide Field Camera 3 to measure the amount of starlight across the galaxy, dubbed A2261-BCG. The Hubble observations revealed that the galaxy's puffy core, measuring about 10,000 light-years, is the largest yet seen.

A galaxy's core size typically is correlated to the dimensions of its host galaxy, but in this case, the central region is much larger than astronomers would expect for the galaxy's size. In fact, the bloated core is more than three times larger than the center of other very luminous galaxies. Located three billion light-years away, the galaxy is the most massive and brightest galaxy in the Abell 2261 cluster.

Astronomers have proposed two possibilities for the puffy core. One scenario is that a pair of merging black holes gravitationally stirred up and scattered the stars. Another idea is that the merging black holes were ejected from the core. Left without an anchor, the stars began spreading out even more, creating the puffy-looking core.

Previous Hubble observations have revealed that supermassive black holes, weighing millions or billions times more than the sun, reside at the centers of nearly all galaxies and may play a role in shaping those central regions.

"Expecting to find a black hole in every galaxy is sort of like expecting to find a pit inside a peach," explained astronomer Tod Lauer of the National Optical Astronomy Observatory in Tucson, Ariz., a co-author of the Hubble study. "With this Hubble observation, we cut into the biggest peach and we can't find the pit. We don't know for sure that the black hole is not there, but Hubble shows that there's no concentration of stars in the core."

Team leader Marc Postman of the Space Telescope Science Institute in Baltimore, Md., said the galaxy stood out in the Hubble image. "When I first saw the image of this galaxy, I knew right away it was unusual," Postman explained. "The core was very diffuse and very large. The challenge was then to make sense of all the data, given what we knew from previous Hubble observations, and come up with a plausible explanation for the intriguing nature of this particular galaxy."

The paper describing the results appeared in the Sept. 10 issue of The Astrophysical Journal. The astronomers expected to see a slight cusp of light in the galaxy's center, marking the location of the black hole and attendant stars. Instead, the starlight's intensity remained fairly even across the galaxy.

One possibility for the puffy core may be due to two central black holes orbiting each other. These black holes collectively could have been as massive as several billion suns. Though one of the black holes would be native to the galaxy, a second black hole could have been added from a smaller galaxy that was gobbled up by the massive elliptical.

In this scenario, stars circling in the giant galaxy's center came close to the twin black holes. The stars were then given a gravitational boot out of the core. Each gravitational slingshot robbed the black holes of momentum, moving the pair ever closer together, until finally they merged, forming one supermassive black hole that still resides in the galaxy's center.

Another related possibility is that the black-hole merger created gravity waves, which are ripples in the fabric of space. According to the theory of general relativity, a pair of merging black holes produce ripples of gravity that radiate away. If the black holes are of unequal mass, then some of the energy may radiate more strongly in one direction, producing the equivalent of a rocket thrust. The imbalance of forces would have ejected the merged black hole from the center at speeds of millions of miles an hour, resulting in the rarity of a galaxy without a central black hole. "The black hole is the anchor for the stars," Lauer explained. "If you take it out, all of a sudden you have a lot less mass. The stars don't get held down very well and they expand out, enlarging the core even more."

The team admits that the ejected black-hole scenario may sound far-fetched, "but that's what makes observing the universe so intriguing — sometimes you find the unexpected," said Postman.

Added Lauer: "This is a system that's interesting enough that it pushes against a lot of questions. We have thought an awful lot about what black holes do. But we haven't been able to test our theories. This is an interesting place where a lot of the ideas we've had can come together and can be tested, fairly exotic ideas about how black holes may interact with each other dynamically and how they would affect the surrounding stellar population."

The team is now conducting follow-up observations with the Very Large Array radio telescope (VLA) in New Mexico. The astronomers expect material falling onto a black hole to emit radio waves, among other types of radiation. They will compare the VLA data with the Hubble images to more precisely pin down the location of the black hole, if it indeed exists.

The Abell 2261 cluster is part of a multi-wavelength survey, led by Postman, called the Cluster Lensing And Supernova survey with Hubble (CLASH). The survey probes the distribution of dark matter in 25 massive galaxy clusters.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington.