Tag Archives: astronomy

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Exoplanet Exploration

It wasn’t too long ago that astronomers found the first indirect evidence of a planet beyond our solar system. They inferred the presence of an exoplanet (extrasolar planet) from the periodic dimming or wiggle of its parental star, rather than much more difficult direct observation. Since the first confirmed exoplanet was discovered in 1995 (51 Pegasi b), researchers have definitively  catalogued around 800, and identified another 18,000 candidates. And, the list seems to now grow daily.

If that wasn’t amazing enough researchers now have directly observed several exoplanets and even measured their atmospheric composition.

[div class=attrib]From ars technica:[end-div]

The star system HR 8799 is a sort of Solar System on steroids: a beefier star, four possible planets that are much bigger than Jupiter, and signs of asteroids and cometary bodies, all spread over a bigger region. Additionally, the whole system is younger and hotter, making it one of only a few cases where astronomers can image the planets themselves. However, HR 8799 is very different from our Solar System, as astronomers are realizing thanks to two detailed studies released this week.

The first study was an overview of the four exoplanet candidates, covered by John Timmer. The second set of observations focused on one of the four planet candidates, HR 8799c. Quinn Konopacky, Travis Barman, Bruce Macintosh, and Christian Marois performed a detailed spectral analysis of the atmosphere of the possible exoplanet. They compared their findings to the known properties of a brown dwarf and concluded that they don’t match—it is indeed a young planet. Chemical differences between HR 8799c and its host star led the researchers to conclude the system likely formed in the same way the Solar System did.

The HR 8799 system was one of the first where direct imaging of the exoplanets was possible; in most cases, the evidence for a planet’s presence is indirect. (See the Ars overview of exoplanet science for more.) This serendipity is possible for two major reasons: the system is very young, and the planet candidates orbit far from their host star.

The young age means the bodies orbiting the system still retain heat from their formation and so are glowing in the infrared; older planets emit much less light. That makes it possible to image these planets at these wavelengths. (We mostly image planets in the Solar System using reflected sunlight, but that’s not a viable detection strategy at these distances). A large planet-star separation means that the star’s light doesn’t overwhelm the planets’ warm glow. Astronomers are also assisted by HR 8799’s relative closeness to us—it’s only about 130 light-years away.

However, the brightness of the exoplanet candidates also obscures their identity. They are all much larger than Jupiter—each is more than 5 times Jupiter’s mass, and the largest could be 35 times greater. That, combined with their large infrared emission, could mean that they are not planets but brown dwarfs: star-like objects with insufficient mass to engage in hydrogen fusion. Since brown dwarfs can overlap in size and mass with the largest planets, we haven’t been certain that the objects observed in the HR 8799 system are planets.

For this reason, the two recent studies aimed at measuring the chemistry of these bodies using their spectral emissions. The Palomar study described yesterday provided a broad, big-picture view of the whole HR 8799 system. By contrast, the second study used one of the 10-meter Keck telescopes for a focused, in-depth view of one object: HR 8799c, the second-farthest out of the four.

The researchers measured relatively high levels of carbon monoxide (CO) and water (H2O, just in case you forgot the formula), which were present at levels well above the abundance measured in the spectrum of the host star. According to the researchers, this difference in chemical composition indicated that the planet likely formed via “core accretion”— the gradual, bottom-up accumulation of materials to make a planet—rather than a top-down fragmentation of the disk surrounding the newborn star. The original disk in this scenario would have contained a lot of ice fragments, which merged to make a world relatively high in water content.

In many respects, HR 8799c seemed to have properties between brown dwarfs and other exoplanets, but the chemical and gravitational analyses pushed the object more toward the planet side. In particular, the size and chemistry of HR 8799c placed its surface gravity lower than expected for a brown dwarf, especially when considered with the estimated age of the star system. While this analysis says nothing about whether the other bodies in the system are planets, it does provide further hints about the way the system formed.

One final surprise was the lack of methane (CH4) in HR 8799c’s atmosphere. Methane is a chemical component present in all the Jupiter-like planets in our Solar System. The authors argued that this could be due to vigorous mixing of the atmosphere, which is expected because the exoplanet has higher temperatures and pressures than seen on Jupiter or Neptune. This mixing could enable reactions that limit methane formation. Since the HR 8799 system is much younger than the Solar System—roughly 30 million years compared with 4.5 billion years—it’s uncertain how much this chemical balance may change over time.

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]One of the discovery images of the system obtained at the Keck II telescope using the adaptive optics system and NIRC2 Near-Infrared Imager. The rectangle indicates the field-of-view of the OSIRIS instrument for planet C. Courtesy of NRC-HIA, C. Marois and Keck Observatory.[end-div]

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Shedding Some Light On Dark Matter

Cosmologists theorized the need for dark matter to account for hidden mass in our universe. Yet, as the name implies, it is proving rather hard to find. Now astronomers believe they see hints of it in ancient galactic collisions.

[div class=attrib]From New Scientist:[end-div]

Colliding clusters of galaxies may hold clues to a mysterious dark force at work in the universe. This force would act only on invisible dark matter, the enigmatic stuff that makes up 86 per cent of the mass in the universe.

Dark matter famously refuses to interact with ordinary matter except via gravity, so theorists had assumed that its particles would be just as aloof with each other. But new observations suggest that dark matter interacts significantly with itself, while leaving regular matter out of the conversation.

“There could be a whole class of dark particles that don’t interact with normal matter but do interact with themselves,” says James Bullock of the University of California, Irvine. “Dark matter could be doing all sorts of interesting things, and we’d never know.”

Some of the best evidence for dark matter’s existence came from the Bullet clusterMovie Camera, a smash-up in which a small galaxy cluster plunged through a larger one about 100 million years ago. Separated by hundreds of light years, the individual galaxies sailed right past each other, and the two clusters parted ways. But intergalactic gas collided and pooled on the trailing ends of each cluster.

Mass maps of the Bullet cluster showed that dark matter stayed in line with the galaxies instead of pooling with the gas, proving that it can separate from ordinary matter. This also hinted that dark matter wasn’t interacting with itself, and was affected by gravity alone.

Musket shot

Last year William Dawson of the University of California, Davis, and colleagues found an older set of clusters seen about 700 million years after their collision. Nicknamed the Musket Ball cluster, this smash-up told a different tale. When Dawson’s team analysed the concentration of matter in the Musket Ball, they found that galaxies are separated from dark matter by about 19,000 light years.

“The galaxies outrun the dark matter. That’s what creates the offset,” Dawson said. “This is fitting that picture of self-interacting dark matter.” If dark matter particles do interact, perhaps via a dark force, they would slow down like the gas.

This new picture could solve some outstanding mysteries in cosmology, Dawson said this week during a meeting of the American Astronomical Society in Long Beach, California. Non-interacting dark matter should sink to the cores of star clusters and dwarf galaxies, but observations show that it is more evenly distributed. If it interacts with itself, it could puff up and spread outward like a gas.

So why doesn’t the Bullet cluster show the same separation between dark matter and galaxies? Dawson thinks it’s a question of age – dark matter in the younger Bullet simply hasn’t had time to separate.

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image: An overlay of an optical image of a cluster of galaxies with an x-ray image of hot gas lying within the cluster. Courtesy of NASA.[end-div]

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Next Potential Apocalypse: 2036

Having missed the recent apocalypse said to have been predicted by the Mayans, the next possible end of the world is set for 2036. This time it’s courtesy of aptly named asteroid – Apophis.

[div class=attrib]From the Guardian:[end-div]

In Egyptian myth, Apophis was the ancient spirit of evil and destruction, a demon that was determined to plunge the world into eternal darkness.

A fitting name, astronomers reasoned, for a menace now hurtling towards Earth from outerspace. Scientists are monitoring the progress of a 390-metre wide asteroid discovered last year that is potentially on a collision course with the planet, and are imploring governments to decide on a strategy for dealing with it.

Nasa has estimated that an impact from Apophis, which has an outside chance of hitting the Earth in 2036, would release more than 100,000 times the energy released in the nuclear blast over Hiroshima. Thousands of square kilometres would be directly affected by the blast but the whole of the Earth would see the effects of the dust released into the atmosphere.

And, scientists insist, there is actually very little time left to decide. At a recent meeting of experts in near-Earth objects (NEOs) in London, scientists said it could take decades to design, test and build the required technology to deflect the asteroid. Monica Grady, an expert in meteorites at the Open University, said: “It’s a question of when, not if, a near Earth object collides with Earth. Many of the smaller objects break up when they reach the Earth’s atmosphere and have no impact. However, a NEO larger than 1km [wide] will collide with Earth every few hundred thousand years and a NEO larger than 6km, which could cause mass extinction, will collide with Earth every hundred million years. We are overdue for a big one.”

Apophis had been intermittently tracked since its discovery in June last year but, in December, it started causing serious concern. Projecting the orbit of the asteroid into the future, astronomers had calculated that the odds of it hitting the Earth in 2029 were alarming. As more observations came in, the odds got higher.

Having more than 20 years warning of potential impact might seem plenty of time. But, at last week’s meeting, Andrea Carusi, president of the Spaceguard Foundation, said that the time for governments to make decisions on what to do was now, to give scientists time to prepare mitigation missions. At the peak of concern, Apophis asteroid was placed at four out of 10 on the Torino scale – a measure of the threat posed by an NEO where 10 is a certain collision which could cause a global catastrophe. This was the highest of any asteroid in recorded history and it had a 1 in 37 chance of hitting the Earth. The threat of a collision in 2029 was eventually ruled out at the end of last year

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Graphic: This graphic shows the orbit of the asteroid Apophis in relation to the paths of Earth and other planets in the inner solar system. Courtesy of MSNBC.[end-div]

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Planets From Stardust

Stunning images captured by Atacama Millimetre-submillimetre Array (ALMA) radio telescope in Chile show the early stages of a planet forming from stardust around a star located 450 light-years from Earth. This is the first time that astronomers have snapped such a clear picture of the process, confirming long-held theories of planetary formation.

[div class=attrib]From Independent:[end-div]

The world’s highest radio telescope, built on a Chilean plateau in the Andes 5,000 metres above sea level, has captured the first image of a new planet being formed as it gobbles up the cosmic dust and gas surrounding a distant star.

Astronomers have long predicted that giant “gas” planets similar to Jupiter would form by collecting the dust and debris that forms around a young star. Now they have the first visual evidence to support the phenomenon, scientists said.

The image taken by the Atacama Millimetre-submillimetre Array (ALMA) in Chile shows two streams of gas connecting the inner and outer disks of cosmic material surrounding the star HD 142527, which is about 450 light-years from Earth.

Astronomers believe the gas streamers are the result of two giant planets – too small to be visible in this image – exerting a gravitational pull on the cloud of surrounding dust and gas, causing the material to flow from the outer to inner stellar disks, said Simon Casassus of the University of Chile in Santiago.

“The most natural interpretation for the flows seen by ALMA is that the putative proto-planets are pulling streams of gas inward towards them that are channelled by their gravity. Much of the gas then overshoots the planets and continues inward to the portion of the disk close to the star, where it can eventually fall onto the star itself,” Dr Casassus said.

“Astronomers have been predicting that these streams exist, but this is the first time we’ve been able to see them directly. Thanks to the new ALMA telescope, we’ve been able to get direct observations to illuminate current theories of how planets are formed,” he said.

[div class=attrib]Read the entire article following the jump.[end-div]

[div class=attrib]Image: Observations (left) made with the ALMA telescope of the young star HD 142527. The dust in the outer disc is shown in red. Dense gas in the streams flowing across the gap, as well as in the outer disc, is shown in green. Diffuse gas in the central gap is shown in blue. The gas filaments can be seen at the three o’clock and ten o’clock positions, flowing from the outer disc towards the centre. And (right) an artist’s impression. Courtesy of Independent.[end-div]

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Rivers of Methane

The image shows what looks like a satellite picture of a river delta, complete with tributaries. It could be the Nile or the Amazon river systems as seen from space.

However, the image is not of an earthbound river at all. It’s a recently discovered river on Titan, Saturn’s largest moon. And, the river’s contents are not even water, but probably a mixture of liquid ethane and methane.

[div class=attrib]From NASA:[end-div]

This image from NASA’s Cassini spacecraft shows a vast river system on Saturn’s moon Titan. It is the first time images from space have revealed a river system so vast and in such high resolution anywhere other than Earth. The image was acquired on Sept. 26, 2012, on Cassini’s 87th close flyby of Titan. The river valley crosses Titan’s north polar region and runs into Ligeia Mare, one of the three great seas in the high northern latitudes of Saturn’s moon Titan. It stretches more than 200 miles (400 kilometers).

Scientists deduce that the river is filled with liquid because it appears dark along its entire extent in the high-resolution radar image, indicating a smooth surface. That liquid is presumably ethane mixed with methane, the former having been positively identified in 2008 by Cassini’s visual and infrared mapping spectrometer at the lake known as Ontario Lacus in Titan’s southern hemisphere. Though there are some short, local meanders, the relative straightness of the river valley suggests it follows the trace of at least one fault, similar to other large rivers running into the southern margin of Ligeia Mare (see PIA10008). Such faults may lead to the opening of basins and perhaps to the formation of the giant seas themselves.

North is toward the top of this image.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The RADAR instrument was built by JPL and the Italian Space Agency, working with team members from the US and several European countries. JPL is a division of the California Institute of Technology in Pasadena.

[div class=attrib]Read the entire article following the jump.[end-div]

[div class=attrib]Image courtesy of NASA/JPL-Caltech/ASI.[end-div]

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The Habitable Exoplanets Catalog

The Habitable Exoplanets Catalog is a fascinating resource for those who dream of starting a new life on a distant world. Only into its first year, the catalog now lists 7 planets outside of our solar system and within our own Milky Way galaxy that could become a future home for adventurous humans — complaints from existing inhabitants notwithstanding. Although, the closest at the moment at a distance of just over 20 light years — Gliese 581g — would take around 200,000 years to reach using current technology.

[div class=attrib]From the Independent:[end-div]

An ambitious project to catalogue every habitable planet has discovered seven worlds inside the Milky Way that could possibly harbour life.

Marking its first anniversary, the Habitable Exoplanets Catalog said it had far exceeded its expectation of adding one or two new planets this year in its search for a new earth.

In recent years scientists from the Puerto Rico-based Planetary Habitability Laboratory that runs the catalogue have sharpened their techniques for finding new planets outside our solar system.

Chile’s High Accuracy Radial Veolocity Planet Searcher and the orbiting Kepler Space Telescope are two of the many tools that have increased the pace of discoveries.

The Planetary Habitability Laboratory launched the Habitable Exoplanets Catalog last year to measure the suitability for life of these emerging worlds and as a way to organise them for the public.

It has found nearly 80 confirmed exoplanets with a similar size to Earth but only a few of those have the right distance from their star to support liquid surface water – the presence of which is considered essential to sustain life.

Seven potentially habitable exoplanets are now listed by the Habitable Exoplanets Catalog, including the disputed Gliese 581g, plus some 27 more from NASA Kepler candidates waiting for confirmation.

Although all these exoplanets are superterrans are considered potentially habitable, scientists have not yet found a true Earth analogue.

[div class=attrib]Read the entire article following the jump.[end-div]

[div class=attrib]Image: Current Potential Habitable Exoplanets. Courtesy of CREDIT: PHL @ UPR Arecibo.[end-div]

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A Star is Born, and its Solar System

A diminutive stellar blob some 450 million light years away seems to be a young star giving birth to a planetary system much like our very own Solar System. The developing protostar and its surrounding gas cloud is being tracked astronomers at the National Radio Astronomy Observatory in Charlottesville, Virginia. Stellar and planetary evolution in action.

[div class=attrib]From New Scientist:[end-div]

Swaddled in a cloud of dust and gas, the baby star shows a lot of potential. It is quietly sucking in matter from the cloud, which holds enough cosmic nourishment for the infant to grow as big and bright as our sun. What’s more, the star is surrounded by enough raw material to build at least seven planetary playmates.

Dubbed L1527, the star is still in the earliest stages of development, so it offers one of the best peeks yet at what our solar system may have looked like as it was taking shape.

The young star is currently one-fifth of the mass of the sun, but it is growing. If it has been bulking up at the same rate all its life, the star should be just 300,000 years old – a mere tyke compared to our 4.6-billion-year-old sun. But the newfound star may be even younger, because some theories say stars initially grow at a faster rate.

Diminutive sun

The cloud feeding the protostar contains at least as much material as our sun, says John Tobin of the National Radio Astronomy Observatory in Charlottesville, Virginia.

“The key factor in determining a star’s characteristics is the mass, so L1527 could potentially grow to become similar to the sun,” says Tobin.

Material from the cloud is being funnelled to the star through a swirling disc that contains roughly 0.5 per cent the mass of the sun. That might not sound like a lot, but that’s enough mass to make up at least seven Jupiter-sized planets.

Previous observations of L1527 had hinted that a disk encircled the star, but it was not clear that the disk was rotating, which is an essential ingredient for planet formation. So Tobin and his colleagues took a closer look.

Good rotations

The team used radio observations to detect the presence of carbon monoxide around the star and watched how the material swirled around in the disc to trace its overall motion. They found that matter nearest to the star is rotating faster than material near the edge of the disc – a pattern that mirrors the way planets orbit a star.

“The dust and gas are orbiting the protostar much like how planets orbit the sun,” says Tobin. “Unfortunately there is no telling how many planets might form or how large they will be.”

[div class=attrib]Read the entire article following the jump.[end-div]

[div class=attrib]Protostar L1527. Courtesy of NASA / JPL, via tumblr.[end-div]

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Flowing Water on Mars?

NASA’s latest spacecraft to visit Mars, the Mars Reconnaissance Orbiter, has made some stunning observations that show the possibility of flowing water on the red planet. Intriguingly,  repeated observations of the same regions over several Martian seasons show visible changes attributable to some kind of dynamic flow.

[div class=attrib]From NASA / JPL:[end-div]

Observations from NASA’s Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.

“NASA’s Mars Exploration Program keeps bringing us closer to determining whether the Red Planet could harbor life in some form,” NASA Administrator Charles Bolden said, “and it reaffirms Mars as an important future destination for human exploration.”

Dark, finger-like features appear and extend down some Martian slopes during late spring through summer, fade in winter, and return during the next spring. Repeated observations have tracked the seasonal changes in these recurring features on several steep slopes in the middle latitudes of Mars’ southern hemisphere.

“The best explanation for these observations so far is the flow of briny water,” said Alfred McEwen of the University of Arizona, Tucson. McEwen is the principal investigator for the orbiter’s High Resolution Imaging Science Experiment (HiRISE) and lead author of a report about the recurring flows published in Thursday’s edition of the journal Science.

Some aspects of the observations still puzzle researchers, but flows of liquid brine fit the features’ characteristics better than alternate hypotheses. Saltiness lowers the freezing temperature of water. Sites with active flows get warm enough, even in the shallow subsurface, to sustain liquid water that is about as salty as Earth’s oceans, while pure water would freeze at the observed temperatures.

[div class=attrib]More from theSource here.[end-div]

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Seven Sisters Star Cluster

The Seven Sisters star cluster, also known as the Pleiades, consists of many, young, bright and hot stars. While the cluster contains hundreds of stars it is so named because only seven are typically visible to the naked eye. The Seven Sisters is visible from the northern hemisphere, and resides in the constellation Taurus.

[div class=attrib]Image and supporting text courtesy of Davide De Martin over at Skyfactory.[end-div]

This image is a composite from black and white images taken with the Palomar Observatory’s 48-inch (1.2-meter) Samuel Oschin Telescope as a part of the second National Geographic Palomar Observatory Sky Survey (POSS II). The images were recorded on two type of glass photographic plates – one sensitive to red light and the other to blue and later they were digitized. Credit: Caltech, Palomar Observatory, Digitized Sky Survey.

In order to produce the color image seen here, I worked with data coming from 2 different photographic plates taken in 1986 and 1989. Original file is 10.252 x 9.735 pixels with a resolution of about 1 arcsec per pixel. The image shows an area of sky large 2,7° x 2,7° (for comparison, the full-Moon is about 0,5° in diameter).

[div class=attrib]More from theSource here.[end-div]

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Happy Birthday Neptune

One hundred and sixty-four years ago, or one Neptunian year, Neptune was first observed by telescope. Significantly, it was the first planet to be discovered deliberately; the existence and location of the gas giant was calculated mathematically. Subsequently, it was located by telescope, on 24 September 1846, and found to be within one degree of the mathematically predicted location. Astronomers hypothesized Neptune’s existence due to perturbations in the orbit of its planetary neighbor, Uranus, around the sun, which could only be explained by the presence of another object in nearby orbit. A triumph for the scientific method, and besides, it’s beautiful too.

[div class=attrib]Image courtesy of NASA.[end-div]

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Nick Risinger’s Photopic Sky Survey

Big science covering scales from the microscopic to the vastness of the universe continues to deliver stunning new insights, now on a daily basis. I takes huge machines such as the Tevatron at Fermilab, CERN’s Large Hadron Collider, NASA’s Hubble Telescope and the myriad other detectors, arrays, spectrometers, particle smashers to probe some of our ultimate questions. The results from these machines bring us fantastic new perspectives and often show us remarkable pictures of the very small and very large.

Then there is Nick Risinger’s Photopic Sky Survey. No big science, no vast machines — just Nick Risinger, accompanied by retired father, camera equipment and 45,000 miles of travels capturing our beautiful night sky as never before.

[div class=attrib]From Nick Risinger:[end-div]

The Photopic Sky Survey is a 5,000 megapixel photograph of the entire night sky stitched together from 37,440 exposures. Large in size and scope, it portrays a world far beyond the one beneath our feet and reveals our familiar Milky Way with unfamiliar clarity.

It was clear that such a survey would be quite difficult visually hopping from one area of the sky to the next—not to mention possible lapses in coverage—so this called for a more systematic approach. I divided the sky into 624 uniformly spaced areas and entered their coordinates into the computer which gave me assurance that I was on target and would finish without any gaps. Each frame received a total of 60 exposures: 4 short, 4 medium, and 4 long shots for each camera which would help to reduce the amount of noise, overhead satellite trails and other unwanted artifacts.

And so it was with this blueprint that I worked my way through the sky, frame by frame, night after night. The click-clack of the shutters opening and closing became a staccato soundtrack for the many nights spent under the stars. Occasionally, the routine would be pierced by a bright meteor or the cry of a jackal, each compelling a feeling of eerie beauty that seemed to hang in the air. It was an experience that will stay with me a lifetime.

A truly remarkable and beautiful achievement. This is what focus and passion can achieve.

[div class=attrib]More from theSource here.[end-div]