Category Archives: Space
MESSENGER’s First (Mercury) Day
From NASA – Astronomy Picture of the Day
Explanation: One solar day on a planet is the length of time from noon to noon. A solar day lasts 24 hours on planet Earth. On Mercury a solar day is about 176 Earth days long. And during its first Mercury solar day in orbit the MESSENGER spacecraft has imaged nearly the entire surface of the innermost planet to generate a global monochrome map at 250 meters per pixel resolution and a 1 kilometer per pixel resolution color map. Examples of the maps, mosaics constructed from thousands of images made under uniform lighting conditions, are shown (monochrome at left), both centered along the planet’s 75 degrees East longitude meridian. The MESSENGER spacecraft’s second Mercury solar day will likely include more high resolution targeted observations of the planet’s surface features. (Editor’s note: Due to Mercury’s 3:2 spin-orbit resonance, a Mercury solar day is 2 Mercury years long.)
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Astronomers Find Elusive Planets in Decade-Old Hubble Data
The left image shows the star HR 8799 as seen by Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) in 1998. The center image shows recent processing of the NICMOS data with newer, sophisticated software. The processing removes most of the scattered starlight to reveal three planets orbiting HR 8799. Based on the reanalysis of NICMOS data and ground-based observations, the illustration on the right shows the positions of the star and the orbits of its four known planets. (Credit: NASA; ESA; STScI, R. Soummer)
In a painstaking re-analysis of Hubble Space Telescope images from 1998, astronomers have found visual evidence for two extrasolar planets that went undetected back then.
Finding these hidden gems in the Hubble archive gives astronomers an invaluable time machine for comparing much earlier planet orbital motion data to more recent observations. It also demonstrates a novel approach for planet hunting in archival Hubble data.
Four giant planets are known to orbit the young, massive star HR 8799, which is130 light-years away. In 2007 and 2008 the first three planets were discovered in near-infrared ground-based images taken with the W.M. Keck Observatory and the Gemini North telescope by Christian Marois of the National Research Council in Canada and his team. Marois and his colleagues then uncovered a fourth innermost planet in 2010. This is the only multiple exoplanetary system for which astronomers have obtained direct snapshots.
In 2009 David Lafreniere of the University of Montreal recovered hidden exoplanet data in Hubble images of HR 8799 taken in 1998 with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). He identified the position of the outermost planet known to orbit the star. This first demonstrated the power of a new data-processing technique for retrieving faint planets buried in the glow of the central star.
A new analysis of the same archival NICMOS data by Remi Soummer of the Space Telescope Science Institute in Baltimore has recovered all three of the outer planets. The fourth, innermost planet is 1.5 billion miles from the star and cannot be seen because it is on the edge of the NICMOS coronagraphic spot that blocks the light from the central star.
By finding the planets in multiple images spaced over years of time, the orbits of the planets can be tracked. Knowing the orbits is critical to understanding the behavior of multiple-planet systems because massive planets can perturb each other’s orbits. “From the Hubble images we can determine the shape of their orbits, which brings insight into the system stability, planet masses and eccentricities, and also the inclination of the system,” says Soummer.
These results are to be published in the Astrophysical Journal.
The three outer gas-giant planets have approximately 100-, 200-, and 400-year orbits. This means that astronomers need to wait a very long time to see how the planets move along their paths. The added time span from the Hubble data helps enormously. “The archive got us 10 years of science right now,” he says. “Without this data we would have had to wait another decade. It’s 10 years of science for free.”
Story Continues -> Astronomers Find Elusive Planets in Decade-Old Hubble Data
Close-up mission to sun gets green light
by Emma Woollacott
The European Space Agency (ESA) has approved a mission to get nearer to the sun than ever before.
Solar Orbiter will get within 26 million miles of the sun, aiming to gather data on how the sun generates and propels the solar wind – the flow of charged particles out towards the planets.
“Solar Orbiter will help scientists to understand processes, such as coronal mass ejections, that affect Earth’s citizens by disrupting, for example, radio communication and power transmission,” says Alvaro Giménez, ESA’s director of science and robotic exploration.
The probe will get close enough to sample this solar wind very soon after it’s been ejected, while at the same time observing in great detail how the wind is accelerated on the sun’s surface.
It should capture detailed images of the sun’s far side when it’s not visible from Earth, as well as the polar regions.
Launch is planned for 2017 from Cape Canaveral with a NASA-provided Atlas launch vehicle.
The project is one of two to be selected by ESA, the other being Euclid. Essentially a space telescope, the mission will map out the large-scale structure and evolution of the Universe with greater accuracy than ever before.
Thown out, at least for now, is the Plato mission to search for planets around other stars. But, says ESA, there’s a chance it’ll get the green light at a future date.
“It was an arduous dilemma for the Science Programme Committee to choose two from the three excellent candidates,” says Fabio Favata, head of the Science Program’s planning office.
“All of them would produce world-class science and would put Europe at the forefront in the respective fields.”
One-Third of Sun-Like Stars Have Earth-Like Planets In Habitable Zone
Astronomers have calculated the likelihood of finding Earth-like planets around other stars using the latest data from the Kepler mission.
The Kepler orbiting observatory is specifically designed to find Earth-like planets around nearby stars.
Earlier this year, the Kepler team released the mission’s first 136 days of data and it has turned out to be a veritable jackpot. In that time Kepler looked at some 150,000 target stars and found evidence for 1,235 potential exoplanets. That’s quite a haul.
Since then, most of the work on this database has been to identify the characteristics of all these exoplanets. But such a large dataset also allows for statistical analyses too, from which various projections can be made.
Today, Wesley Traub at the California Institute of Technology in Pasadena, reveals the results of just such a study. Traub has looked only at the stars that are most similar to the Sun, namely those with the classification F, G or K and worked out often various types of planets occur.
The results are straightforward to state. Traub says that mid-size planets are just as likely to be found around faint stars and bright ones. By contrast, far fewer small planets show up around faint stars. That’s almost certainly because small planets are more difficult for Kepler to see.
It’s also easier for Kepler to see planets that are closer to their stars because it looks for the tiny changes in brightness that these transits cause. That’s why almost a third of all Kepler’s detections orbit their star in less than 42 days. For the most part, these planets orbit too closely to be in the habitable zone.
What interests most astronomers is how many exoplanets orbit at a greater distance, inside the habitable zone. Most of these planets are too far away from their stars to have been picked up by Kepler yet. But Traub says his data analysis provides a way to work out how many their ought to be.
That’s because he’s found a power law that describes how the number of stars with a given orbital period. So all he has to do is assume a longer orbital period equivalent to being in the habitable zone to work out how many planets there ought to be at this distance.
Here’s the answer: “About one-third of FGK stars are predicted to have at least one terrestrial, habitable-zone planet,” he says.
So by this measure, there are plenty of other Earths out there.
Ref: arxiv.org/abs/1109.4682: Terrestrial, Habitable-Zone Exoplanet Frequency from Kepler
One-Third of Sun-Like Stars Have Earth-Like Planets In Habitable Zone
Was the Space Shuttle a Mistake?
Shuttle assembly: NASA’s first space shuttle, Columbia, was assembled at Kennedy Space Center in Florida in November 1980. It completed 27 missions before breaking apart during reentry into Earth’s atmosphere in 2003.
Credit: NASA
The program’s benefits weren’t worth the cost—and now the U.S. is in jeopardy of repeating the same mistake, says a leading space policy expert.
By John M. Logsdon
Forty years ago, I wrote an article for Technology Review titled “Shall We Build the Space Shuttle?” Now, with the 135th and final flight of the shuttle at hand, and the benefit of hindsight, it seems appropriate to ask a slightly different question—”Should We Have Built the Space Shuttle?”
After the very expensive Apollo effort, a low-cost space transportation system for both humans and cargo was seen as key to the future of the U.S. space program in the 1980s and beyond. So developing some form of new space launch system made sense as the major NASA effort for the 1970s, presuming the United States was committed to continuing space leadership. But it was probably a mistake to develop this particular space shuttle design, and then to build the future U.S. space program around it.
The selection in 1972 of an ambitious and technologically challenging shuttle design resulted in the most complex machine ever built. Rather than lowering the costs of access to space and making it routine, the space shuttle turned out to be an experimental vehicle with multiple inherent risks, requiring extreme care and high costs to operate safely. Other, simpler designs were considered in 1971 in the run-up to President Nixon’s final decision; in retrospect, taking a more evolutionary approach by developing one of them instead would probably have been a better choice.
The shuttle does, of course, leave behind a record of significant achievements. It is a remarkably capable vehicle. It has carried a variety of satellites and spacecraft to low-Earth orbit. It serviced satellites in orbit, most notably during the five missions to the Hubble Space Telescope. On a few flights, the shuttle carried in its payload bay a small pressurized laboratory, called Spacelab, which provided research facilities for a variety of experiments. That laboratory was a European contribution to the space shuttle program. With Spacelab and the Canadian-provided robotic arm used to grab and maneuver payloads, the shuttle set the precedent for intimate international cooperation in human spaceflight. The shuttle kept American and allied astronauts flying in space and opened up the spaceflight experience to scientists and engineers, not just test pilots. The space shuttle was a source of considerable pride for the United States; images of a shuttle launch are iconic elements of American accomplishment and technological leadership.
The Story Continues -> http://www.technologyreview.com/computing/37981/?p1=A1&a=f
Star Caught Eating Another Star, X-Ray Flare Shows
A clump of matter from a blue supergiant star (left) heads toward a companion neutron star, depicted with its strong magnetic field lines.
Illustration courtesy ESA/AOES Medialab
Andrew Fazekas
Published July 5, 2011
A tiny cannibal has been caught in the act, thanks to a superbright flash of x-rays spied by cosmic hunters.
The culprit is what’s known as a neutron star, the tiny but very dense corpse of a massive star that died in a supernova blast. Sitting 16,000 light-years away, this particular neutron star is normally among the faintest objects in the x-ray sky.
But during recent observations with the European Space Agency’s XMM-Newton space telescope, the star unexpectedly surged to 10,000 times its original brightness.
“A companion blue supergiant star is believed to have thrown off a gigantic clump of superheated gas from its surface, [which] got attracted by the intense gravitational field of the much smaller and denser neutron star orbiting nearby,” said study leader Enrico Bozzo, an astronomer with the ISDC Data Centre for Astrophysics in Geneva, Switzerland.
The lump of wayward stellar matter measured an estimated 9.9 million miles (16 million kilometers) across and took up about a hundred billion times the volume of the moon.
As it became part of the neutron star, the material was heated to millions of degrees, generating a brilliant x-ray flare that lasted for four hours.
(Related: “Black Hole Caught Eating a Star, Gamma-Ray Flash Hints.”)
Story Continues -> http://news.nationalgeographic.com/news/2011/07/110705-star-eating-star-x-rays-xmm-newton-bozzo-space-science/
Skylon spaceplane gets ESA approval
by Emma Woollacott
After nearly thirty years on the drawing board, a revolutionary British spaceplane has received approval for the next stage of development.
The Skylon vehicle would be able to take off from a runway and reach orbit in a single stage. The idea was derived from the Hotol spacecraft design from British Aerospace and Rolls Royce in the 1980s, which was later abandoned because of technical problems.
It would be capable of delivering payloads of up to 15 tonnes into low Earth orbit – around 200 miles – at about 1/50th of the cost of traditional expendable launch vehicles, such as rockets, says the UK Space Agency.
Its Sabre engines use liquid hydrogen combined with oxygen from the air at altitudes up to 26km and speeds of up to Mach 5, before switching over to on-board liquid oxygen for the final stage of ascent.
Story Continues -> Skylon spaceplane gets ESA approval
Brilliant but Solitary Superstar Discovered in Nearby Galaxy
This view shows part of the very active star-forming region around the Tarantula Nebula in the Large Magellanic Cloud, a small neighbor of the Milky Way. At the exact center lies the brilliant but isolated star VFTS 682 and to its lower right the very rich star cluster R 136. The origins of VFTS are unclear — was it ejected from R 136 or did it form on its own? The star appears yellow-red in this view, which includes both visible-light and infrared images from the Wide Field Imager at the 2.2-meter MPG/ESO telescope at La Silla and the 4.1-meter infrared VISTA telescope at Paranal, because of the effects of dust. (Credit: ESO/M.-R. Cioni/VISTA Magellanic Cloud survey. Acknowledgment: Cambridge Astronomical Survey Unit)
An international team of astronomers [1] has used ESO’s Very Large Telescope to carefully study the star VFTS 682 [2] in the Large Magellanic Cloud, a small neighbouring galaxy to the Milky Way. By analysing the star’s light, using the FLAMES instrument on the VLT, they have found that it is about 150 times the mass of the Sun. Stars like these have so far only been found in the crowded centres of star clusters, but VFTS 682 lies on its own.
“We were very surprised to find such a massive star on its own, and not in a rich star cluster,” notes Joachim Bestenlehner, the lead author of the new study and a student at Armagh Observatory in Northern Ireland. “Its origin is mysterious.”
This star was spotted earlier in a survey of the most brilliant stars in and around the Tarantula Nebula in the Large Magellanic Cloud. It lies in a stellar nursery: a huge region of gas, dust and young stars that is the most active star-forming region in the Local Group of galaxies [3]. At first glance VFTS 682 was thought to be hot, young and bright, but unremarkable. But the new study using the VLT has found that much of the star’s energy is being absorbed and scattered by dust clouds before it gets to Earth — it is actually more luminous than previously thought and among the brightest stars known.
Red and infrared light emitted by the star can get through the dust, but the shorter-wavelength blue and green light is scattered more and lost. As a result the star appears reddish, although if the view were unobstructed it would shine a brilliant blue-white.
As well as being very bright, VFTS 682 is also very hot, with a surface temperature of about 50 000 degrees Celsius [4]. Stars with these unusual properties may end their short lives not just as a supernova, as is normal for high-mass stars, but just possibly as an even more dramatic long-duration gamma-ray burst [5], the brightest explosions in the Universe.
Story Continues -> Brilliant but Solitary Superstar Discovered in Nearby Galaxy
How to Learn a Star’s True Age
Artist’s conception of a hypothetical exoplanet. Gyrochronology is a promising new method to learn the ages of isolated stars, including all stars known to have planets. (Credit: David A. Aguilar (CfA))
For many movie stars, their age is a well-kept secret. In space, the same is true of the actual stars. Like our Sun, most stars look almost the same for most of their lives. So how can we tell if a star is one billion or 10 billion years old? Astronomers may have found a solution — measuring the star’s spin.
“A star’s rotation slows down steadily with time, like a top spinning on a table, and can be used as a clock to determine its age,” says astronomer Soren Meibom of the Harvard-Smithsonian Center for Astrophysics.
Meibom presented his findings May 24, 2011 in a press conference at the 218th meeting of the American Astronomical Society.
Knowing a star’s age is important for many astronomical studies and in particular for planet hunters. With the bountiful harvest from NASA’s Kepler spacecraft (launched in 2009) adding to previous discoveries, astronomers have found nearly 2,000 planets orbiting distant stars. Now, they want to use this new zoo of planets to understand how planetary systems form and evolve and why they are so different from each other.
“Ultimately, we need to know the ages of the stars and their planets to assess whether alien life might have evolved on these distant worlds,” says Meibom. “The older the planet, the more time life has had to get started. Since stars and planets form together at the same time, if we know a star’s age, we know the age of its planets too.”
Learning a star’s age is relatively easy when it’s in a cluster of hundreds of stars that all formed at the same time. Astronomers have known for decades that if they plot the colors and brightnesses of the stars in a cluster, the pattern they see can be used to tell the cluster’s age. But this technique only works on clusters. For stars not in clusters (including all stars known to have planets), determining the age is much more difficult.
Using the unique capabilities of the Kepler space telescope, Meibom and his collaborators measured the rotation rates for stars in a 1-billion-year-old cluster called NGC 6811. This new work nearly doubles the age covered by previous studies of younger clusters. It also significantly adds to our knowledge of how a star’s spin rate and age are related.
Story Continues -> How to Learn a Star’s True Age
The Mystery of Jupiter’s Rings
In 1979 the Voyager 1 spacecraft saw that Jupiter has rings like Saturn too, albeit a much fainter system primarily made up of dust. The particles in Jupiter’s ring are smaller than those in Saturn’s rings and do not reflect light as well. In the case of Jupiter, physical models suggest that the particles should not be able to remain in the rings very long, thus the rings should dissolve over time.
Therefore, it is suspected that the ring systems of the giant planets may be relatively young—only a few hundred million years old — compared to the nearly 5 billion year old age of the planets themselves.
These rings seem to come from material shed when meteors impact four of Jupiter’s tiny inner moons: Ejected stuff from Thebe and Amalthea create the two thick, outer “gossamer” rings, while Adrastea and Metis feed the thin, narrow main ring and the faint inner halo.
The last detailed studies of Jupiter’s rings took place in the 1990s, when NASA’s Galileo spacecraft was orbiting the planet. But now the wealth of highly detailed data imaged from Cassini’s ongoing studies of Saturn is paying off for Jupiter: Using pictures of a wave-like pattern detected in Saturn’s rings, scientists went back to older Galileo shots of Jupiter’s rings and found a wave.
Enter SETI astronomer and Jupiter ring sleuth Mark Showwalter. While everyone knows about Saturn’s spectacular ring system, it’s often forgotten that Jupiter, Uranus, and Neptune are also encircled by fainter and narrower rings. Each of these systems interacts closely with a family of small, inner moons. Showalter works on some of NASA’s highest-profile missions to the outer planets, including Cassini, now orbiting Saturn, and New Horizons, which flew past Jupiter en route to its 2015 encounter with Pluto. He has also searched for the rings of Mars, although so far with no success. Known for his persistence in planetary image analysis, His work on the earlier Voyager mission led to his discovery of Jupiter’s faint, outer “gossamer” rings and Saturn’s tiny ring-moon, Pan.
“Something funny is going on, as if the tip of the ring is flapping in a breeze,” says Showalter. For Saturn, the current theory is that “something” disrupts the rings, briefly tilting them out of the equatorial plane, until the planet’s gravity snaps the rings back into place. This gravitational action starts a ripple through the rings — which Cassini sees as a pattern of light and dark that changes over time.
When Showalter and colleagues looked at Galileo shots of Jupiter’s rings from 1996, they again saw this odd waving pattern. They were able to calculate the length of each oscillation, allowing them to see that the wave moving through the rings must have been started by two separate events: Something disrupted the rings in 1990 and again in 1994 – the year the pieces of broken comet Shoemaker-Levy 9 smacked into the giant planet, leaving black scars the size of the Pacific Ocean in its atmosphere.
Story Continues -> The Mystery of Jupiter’s Rings
