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Showing posts with label Solar System. Show all posts
Showing posts with label Solar System. Show all posts

Thursday, June 01, 2017

Nasa reveals Mission to 'Touch the Sun' for Groundbreaking Parker Solar in 2018

Nasa reveals historic 2018 mission to 'touch the sun' in an attempt to predict devastating solar storms


Nasa is set to announce its ambitious plans to launch a probe mission directly into the atmosphere of the sun in a world first. Dubbed the Parker Solar Probe (PSP), the mission will launch a spacecraft from Earth in the summer of 2018. It will reach an orbit within four million miles (6.5 million km) of the sun and will measure activity at its outer surface, known as the 'corona'. The craft will collect vital information about the life of stars and their weather events, and will help scientists improve how we predict dangerous solar flares.
The spacecraft, dubbed the Parker Solar Probe,
will see a spacecraft launched from Earth in the summer of 2018,
to reach an orbit within four million miles (6.5 million km) of the sun's surface.
This will be seven times closer than any spacecraft that has ventured before it
Nasa announced its plans during a live stream event, which was held at the University of Chicago's William Eckhardt Research Centre Auditorium and broadcast on NasaTV. To start the event off, Professor Rocky Kolb, dean of the Division of the Physical Sciences at the University of Chicago, explained how the idea to study the sun up close was first explored at the University of Chicago in 1958. 'So many fundamental questions about solar wind remain unanswered,' he said. ‘We wanted to take the challenge of going to the worst thermal environment in the solar system - and surviving it,' added Dr Thomas Zurbuchen, associate administrator of Nasa’s Science Mission Directorate in Washington. 'We want to measure the environment there and find what the heating processes are that make the corona hot, and what processes accelerate the solar wind.'

Dr Zurbuchen then announced, live on air, that the probe - originally dubbed the Solar Probe Plus - was to be renamed the Parker Solar Probe after University of Chicago scientist Eugene Parker, who pioneered solar wind science. Dr Parker, who was also speaking at the event, responded: 'I am extremely honoured to be associated with this heroic space mission.' Dr Nicola Fox, mission project scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, then took to the stage.

She said that until now, Nasa didn't have the advanced materials needed to make such a close trip to the sun's corona. She added that the corona is actually hotter than the sun's centre, and that finding out why is a key part of the probe mission. 'I like to think of this as the coolest, hottest mission,' she said. Dr Fox said that Dr Parker's original 1958 paper on solar winds will travel on the probe along with pictures of him and a plate with a comment of his choice. She presented Dr Parker with a model of the new probe to thank him for his work.
This image shows the planned route and flybys of the PSP craft on its six-year mission

She explained that Parker Solar Probe will gradually 'surf' closer and closer to the sun, into its corona. The craft will to withstand higher temperatures than any probe that has come before it. 'We will finally touch the sun,' she said. Answering questions from the audience, Dr Fox described some of the state-of-the-art equipment that the Parker Solar Probe will carry. The craft's kit includes a white light imager called Whisper, which will take images of solar waves as the craft propels through them at high speeds. To measure the 'bulk plasma' of solar winds - which Dr Fox described as the 'break and butter' of the flares - a set of magnetic imaging equipment will also be stored on board. To conclude the conference, Dr Fox added: 'We've really come as far as we can with looking at things and it's time to pay it a visit.'

While minor details of the groundbreaking mission had surfaced earlier this year, the agency's press event will reveal a host of new information about the mission. The spacecraft will swoop within 4 million miles (6.5 million km) of the sun's surface next year - bringing it seven times closer to the sun's surface than any spacecraft before it. The craft will face extremes in heat and radiation and will reach speeds of up to 450,000 miles per hour (725,000 kph) at its closest flyby of the star. It is hoped that PSP can help scientists to better understand solar flares - brief eruptions of intense high-energy radiation from the sun's surface that can knock out communications on Earth.

Sources : Daily Mail


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Thursday, January 29, 2015

NASA Launching Satellite Thursday to Track Earth's Dirt from Space

NASA's next Earth-observing satellite is ready to launch Thursday (Jan. 29), and it could vastly improve the way scientists monitor droughts around the world.
© NASA/Randy Beaudoin
The space agency's Soil Moisture Active Passive satellite (SMAP) is scheduled to launch from California's Vandenberg Air Force base atop a United Launch Alliance Delta II rocket at 9:20 a.m. EST (1420 GMT) on Jan. 29, and at the moment, weather is looking good ahead of liftoff. Officials are predicting an 80 percent chance of good conditions during the 3-minute launch window Thursday.

The SMAP satellite is designed to measure the moisture of Earth's dirt more accurately than ever before, according to NASA. The probe will make a global map of the planet's soil moisture levels every three days. This measurement is important because it can help scientists create more accurate weather models, learn more about drought conditions and even predict floods, NASA officials have said. [See images from the SMAP mission]

"What the soil measurements will do is improve our weather forecasts, improve our assessments of water availability and also address some issues dealing with long-term climate variability and assessments of the impact of human intervention in the global environment," Dara Entekhabi, SMAP science team leader, said during a news conference Tuesday (Jan. 27). "All of these come together and it's the metabolism, how it responds, just like a human body."

© NASA
You can watch live coverage of the SMAP satellite launch starting at 7 a.m. EST (1200 GMT) Thursday (Jan. 29) on Space.com via NASA TV.

The SMAP probe comes equipped with a huge mesh antenna, expected to be deployed sometime after launch. At nearly 20 feet (6 meters), the antenna is the largest of its kind that NASA has ever flown in space, officials have said. SMAP's antenna is designed to spin at about 14.6 revolutions per minute while mounted to the end of a long arm on the satellite's body.

The satellite is built to measure moisture in the top 2 inches (5 centimeters) of soil from its spot in orbit about 426 miles (685 kilometers) above Earth's surface, completing an orbit once every 98.5 minutes. The satellite's unprecedented soil information could help scientists learn more about how droughts spread and the places where they occur. By knowing the moisture in topsoil ahead of time, it could also help researchers better-predict where floods will happen.

"Soil moisture is a key part of the three cycles that support life on this planet: the water cycle, the energy cycle and the carbon cycle," NASA SMAP program executive Christine Bonniksen, said during the news conference. "These things affect human interest: flood, drought, disease control, weather."

The rocket carrying SMAP will also deliver four small cubesats into Earth's orbit during the launch as part of NASA's Educational Launch of Satellites program. One cubesat, called ExoCube, will monitor the upper atmosphere from orbit. Two Firebird satellites will investigate the radiation environment around Earth, and the GRIFEX satellite is a technology demonstration partially developed by NASA's Jet Propulsion Laboratory.  

The $916 million mission is expected to last about three years or more. SMAP is one of five NASA Earth-monitoring satellites originally scheduled for launch in 2014. Three of those missions — Orbiting Carbon Observatory-2 satellite, Global Precipitation Measurement Core Observatory and ISS-RapidScat — got off the ground last year. But SMAP and the recently launched Cloud-Aerosol Transport mission mounted to the International Space Station were delayed until 2015.

Quoted from MSN
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Published by Gusti Putra at: 7:47 AM
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Saturday, February 04, 2012

New Planet Found

A Super-Earth plus Triple Stars Equal Life

An artist depiction of the planet GJ667Cc and the three stars it orbits

The search for exoplanets, or worlds orbiting other stars, is evolving so fast that discoveries that seemed exotic just a few months ago have become commonplace. Multiple-planet solar systems? Astronomers expected to find just a handful; now we know of more than 200. Planets orbiting double or even triple stars? It was big news when just one was announced back in September; we've already got several more examples in hand. In short, the unexpected is something planet hunters have learned to expect — and in most cases, these surprises have tended to expand the possibilities for finding worlds where life might thrive.

It's just happened again: astronomers from the Carnegie Institution of Washington and the University of California, Santa Cruz, writing in the Astrophysical Journal Letters, have announced the discovery of yet another new world that defies everyone's expectations. Not only does the new planet orbit one of the suns in a triple-star system — rare enough in itself — but the stars in this system have surprisingly low levels of the heavy elements planets are made from. Theory suggests that such stars shouldn't form planets in the first place, so if this isn't a fluke, there may be many more planets in the Milky Way than anyone thought.


That's not all: the new planet, called GJ667Cc, is just 4.5 times Earth's mass. That's big enough to qualify it for the astronomical label "super-Earth" but still quite small by exoplanet standards. Indeed, it's so small that GJ667Cc is thought to be made of earthlike rock rather than gas — even if those rocks had to coalesce from a smaller supply of raw material circling the parent sun. Beyond that, it orbits in its star's habitable zone: if there's water there, that water could be in life-friendly liquid form. GJ667Cc whips around its star once every 28 days or so; in our solar system, that would put it so scorchingly close to the sun that water would boil off. But the star in this case is an M-dwarf, much dimmer and redder than our own. Given its mass and its temperature, says co-discoverer Steve Vogt, of UC Santa Cruz, "I think it's going to be pretty historic. We've been gnawing at the bone of an earthlike planet in the habitable zone for years now, and I think we're just about there."

Actually, this isn't the first time he's said something like that. A bit over a year ago, Vogt and Paul Butler, of Carnegie, announced a similarly earthlike planet they called Gliese 581g, but other astronomers were (and remain) dubious about the legitimacy of the find. "We haven't backed off," says Vogt, "but that one will always be controversial, because it's a difficult measurement."

This one, he says, is a much more clear-cut case. Along with Butler, lead author Guillem Anglada-EscudĂ© (now at the University of Göttingen, in Germany) and several others, Vogt combined data from three different ground-based telescopes, dating back 10 years, to come up with the solid signal of a planet. "We were basically able to say, stick a fork in this one and put it in a referred journal — it's done."


What's most exciting of all about GJ667Cc, though, is not just that it's a super-Earth in its star's habitable zone, nor that it was found in a solar system where planets have no right to be. It's that this new world is impressively close to our own Earth. The great majority of exoplanets known to date have been found by the Kepler space probe, but most of these are hundreds of light-years away. That's much too far away to search for even indirect signs of alien life — and that will continue to be true after the James Webb Space Telescope, Hubble's successor, launches in 2018.

But GJ667Cc is a mere 22 light-years away — practically next door — and while the planet can't be seen directly yet, it's not impossible that the next generation of ground or space telescopes could take readings of its atmosphere to look for telltale signs of life. And we have the technology today, says Vogt, "to send a Droid cell phone out there to take closeup images. It would take about 200 years, plus another 20 to send the pictures back."

Nobody's actually planning to do that, but the fact that it's even possible speaks volumes about how close astronomers are to finding and studying places in the universe where life might be thriving at this very moment. In the world of exoplanet science, the improbable things don't seem to stay improbable for very long.

Adapted from TimeMagazine


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Monday, January 02, 2012

NASA Probe Circling Moon on 2012 Eve

(PASADENA, Calif.) — As planet Earth rang in the new year, a different kind of countdown was happening at the moon.

After a 3 ½-month journey, a NASA spacecraft flew over the moon's south pole, fired its engine and dropped into orbit Saturday in the first of two back-to-back arrivals over the New Year's weekend.
NASA probe circling the moon on New Year's Eve
Mission control at the NASA Jet Propulsion Laboratory erupted in cheers and applause after receiving confirmation that the probe was healthy and circling the moon. An engineer was seen on closed-circuit television blowing a noisemaker to herald the New Year's Eve arrival.

"Everything went just as we hoped. The burn was spot-on," chief scientist Maria Zuber of the Massachusetts Institute of Technology said in a post-mission interview with The Associated Press.

The team toasted sparkling cider, but the celebration was brief. Despite the successful maneuver, the work was not over. Its twin still had to enter lunar orbit on New Year's Day.

The Grail probes — short for Gravity Recovery and Interior Laboratory — have been cruising independently toward their destination since launching in September aboard the same rocket on a mission to measure lunar gravity.

Hours before revelers in Times Square watched the ball drop, Grail-A approached the moon and fired its engine for about 40 minutes to get captured into orbit. Deep space antennas in the California desert and Madrid tracked every move and fed real-time updates to ground controllers. About 270 family members and friends of the mission team descended on the NASA campus to watch the drama unfold on a live feed.
"This is great, a big relief," deputy project scientist Sami Asmar told the jubilant crowd.

Grail is the 110th mission to target the moon since the dawn of the Space Age including the six Apollo moon landings that put 12 astronauts on the surface. Despite the attention the moon has received, scientists don't know everything about Earth's nearest neighbor.

Why the moon is ever so slightly lopsided with the far side more mountainous than the side that always faces Earth remains a mystery. A theory put forth earlier this year suggested that Earth once had two moons that collided early in the solar system's history, producing the hummocky region.

Grail is expected to help researchers better understand why the moon is asymmetrical and how it formed by mapping the uneven lunar gravity field that will indicate what's below the surface.

Previous lunar missions have attempted to study the moon's gravity — which is about one-sixth Earth's pull — with mixed results. Grail is the first mission devoted to this goal.
Once in orbit, the near-identical spacecraft will spend the next two months refining their positions until they are just 34 miles above the surface and flying in formation. Data collection will begin in March.
The $496 million mission will be closely watched by schoolchildren. An effort by Sally Ride, the first American woman in space, will allow middle school students to use cameras aboard the probes to zoom in and pick out their favorite lunar spots to photograph.

Despite the latest focus on the moon, NASA won't be sending astronauts back anytime soon. The Obama administration last year nixed a lunar return in favor of landing humans on an asteroid and eventually Mars.
A jaunt to the moon is usually speedy. It took the Apollo astronauts three days to zip there aboard the powerful Saturn V rocket. Since NASA wanted to economize by launching on a small rocket, it took Grail a leisurely 3 1/2 months to make a roundabout trip.

NASA's last moonshot occurred in 2009 with the launch of a pair of spacecraft — one that circled the moon and another that deliberately crashed into the surface and uncovered frozen water in one of the permanently shadowed lunar craters.

Adapted from TIME
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Spacecraft Twins Arrive at the Moon

The Moon is like an aging boxer, its face scarred and distorted by a lifetime of powerful blows. In the boxer's case, those blows are delivered over the course of a few decades. In the case of the Moon, the punishment has been going on for billions of years, courtesy of comets and asteroids that carved out craters and piled up mountains all over the lunar surface. The very birth of the moon was violent: planetary scientists are pretty sure our companion world was created when a Mars-size object slammed into Earth and ripped off a Moon-size chunk.

Artist concept of GRAIL mission.
Much of our understanding of that violent history comes from rocks hauled back by the Apollo missions four decades ago. But the astronauts who gathered that evidence literally just scratched just the surface — and many of the Moon's secrets are buried far deeper.

That's why the GRAIL mission, which successfully inserted itself into lunar orbit over the weekend, is so crucial. GRAIL, the Gravity Recovery And Interior Laboratory, will be probing deep beneath the Moon's surface to analyze its interior structure in unprecedented detail. Since that structure reflects how the Moon was originally formed and the violence done to it since, GRAIL will fill in all sorts of blanks about our satellite's birth and evolution.

That's the "what," but it's the "how" that's so ingenious and that deserves a bit of explanation. GRAIL is not one, but two identical satellites that will orbit in tandem, 35 miles above the surface — GRAIL A in front, GRAIL B following tens of miles behind. If the Moon were simply a featureless, homogenous sphere of rock, the distance between A and B wouldn't change. The Moon isn't featureless, though: in some places there's extra stuff piled on the surface (mountains, crater walls) and in others there are gaping pits — the craters themselves.

When GRAIL A approaches a mountain, the peak's extra gravity pulls on the probe, making it speed up just a bit, while GRAIL B, still out of range, doesn't yet feel the tug. The distance between the two spacecraft increases, and the probes' electronics record the increase, even when the gap widens by no more than the width of a red blood cell. When GRAIL A approaches a crater, by contrast, there's a little less gravity than usual to pull it along. A slows a little, B catches up slightly, and that change is recorded as well. GRAIL B will trail GRAIL A from pole to pole, the pair completing one orbit every two hours as the Moon rotates slowly underneath. Over the mission's three-month lifespan, the twin ships will make three complete gravity maps of the entire lunar globe.

But surface features aren't all the probes will study. There are also regions of higher and lower density buried beneath the lunar surface. These mass concentrations — or mascons — are the likely result of ancient volcanism or ancient impacts. They too exert differing gravitational pull, with the denser material pulling harder than the less dense, and those differences will be detected by the GRAILs as well. So sensitive are the spacecraft that they will effectively be able to see — gravitationally speaking — all the way down to the lunar core. All of these readings will be analyzed along with one other data stream: the slight flexing the entire moon undergoes as a result of the tidal pull of the Earth. The nature of the flexing will be partly determined by what the Moon's deep structure looks like — whether the core is solid or semi-solid or molten, for example.

Best of all, there isn't the slightest doubt that this twin-satellite concept can work: it's based on the wildly successful GRACE (Gravity Recovery And Climate Experiment) mission, which has been orbiting Earth since 2002. By noting changes in our planet's gravity, GRACE has, among other things, discovered a giant impact crater underneath the Antarctic ice sheet, measured ice loss in Greenland and Antarctica and noted depletion of groundwater during the recent U.S. drought. If GRAIL does half as well as GRACE — and there's every reason to think it will — the textbooks on selenology, or lunar geology, may have to undergo some major revisions.

Finally, it's worth noting yet another thing that makes the GRAIL mission so extraordinarily clever. Rather than take a direct route across the 250,000-mile Earth-Moon gap — a journey that took the Apollo astronauts just three days — GRAIL meandered through space on a loop-the-loop path known as a "weak boundary trajectory" that lasted more than three months, following the path of least resistance through the complex terrain created by the interacting gravitational fields of Earth, Moon and Sun. Going slow meant not only that the spacecraft needed less fuel, but also that engineers had longer to check out the probes' electronic health. Plus when GRAIL finally arrived, it took less energy to ease it into a lunar orbit .

Back in 1990, just such a "weak stability boundary" trajectory was first used to salvage the Japanese Hiten satellite, which failed in its original attempt to reach the Moon and didn't have enough fuel for a second try. In a brilliant bit of cosmic inventiveness, a mathematician-turned-rocket-scientist-turned artist named Ed Belbruno calculated a new slow, low-energy route for Hiten and saved the mission.

Fortunately, lunar experts, including MIT's Maria Zuber, GRAIL's lead scientist, won't have long to wait for the results of the mission. GRAIL should be all wrapped up by early summer, and by the time the one-year launch anniversary rolls around in September, we should know a lot more about the long and violent history of our nearest, but still largely unknown, cosmic neighbor.

Republished from TIME
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Published by Gusti Putra at: 1:51 PM
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Tuesday, December 06, 2011

NASA finds alien planet in 'habitable zone'

NASA finds alien planet in 'habitable zone'

Closed captioning of: Planet found in 'habitable zone'
video
story of course has to do with our current earth but we learned today there may be another one out there. astronomers report the discovery of what they are calling an earth-like planet 600 light years away from here. while it is very big it looks like us and they believe it has a temperate climate, perhaps in the 70s all the time. now imagine what we could do with this new place. it could be our chance to start fresh. a place where the chicago cubs always win, where there is always free parking, productive lawmakers and uninterrupted cell phone service. it's called kepler 22-b. while we can work on the name it doesn't hurt to dream.


A 'major milestone' in search for Earth's twin
NASA's Kepler telescope confirms first alien planet found in habitable zone

MOUNTAIN VIEW, Calif. — NASA's planet-hunting Kepler spacecraft has confirmed the discovery of its first alien world in its host star's habitable zone — that just-right range of distances that could allow liquid water to exist — and found more than 1,000 new exoplanet candidates, researchers announced Monday.
This diagram compares our own solar system to Kepler-22,
a star system containing the first "habitable zone" planet discovered by NASA's Kepler mission.

The new finds bring the Kepler space telescope's total haul to 2,326 potential planets in its first 16 months of operation. These discoveries, if confirmed, would quadruple the current tally of worlds known to exist beyond our solar system, which recently topped 700.

The potentially habitable alien world, a first for Kepler, orbits a star very much like our own sun. The discovery brings scientists one step closer to finding a planet like our own — one that could conceivably harbor life, scientists said.


"We're getting closer and closer to discovering the so-called 'Goldilocks planet,'" Pete Worden, director of NASA's Ames Research Center in Moffett Field, Calif., said during a news conference on Monday.

Hunting down alien planets 
The $600 million Kepler observatory launched in March 2009 to hunt for Earth-size alien planets in the habitable zone of their parent stars, where liquid water, and perhaps even life, might be able to exist.
Kepler detects alien planets using what's called the "transit method." It searches for tiny, telltale dips in a star's brightness caused when a planet transits — or crosses in front of — the star from Earth's perspective, blocking a fraction of the star's light.

The finds graduate from "candidates" to full-fledged planets after follow-up observations confirm that they're not false alarms. This process, which is usually done with large, ground-based telescopes, can take about a year.

The Kepler team released data from its first 13 months of operation back in February, announcing that the instrument had detected 1,235 planet candidates, including 54 in the habitable zone and 68 that are roughly Earth-size.

To date, just over two dozen of these potential exoplanets have been confirmed, but Kepler scientists have estimated that at least 80 percent of the instrument's discoveries should end up being the real deal.

More discoveries to come 
The newfound 1,094 planet candidates are the fruit of Kepler's labors during its first 16 months of science work, from May 2009 to September 2010. And they won't be the last of the prolific instrument's discoveries.

"This is a major milestone on the road to finding Earth's twin," Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington, said in a statement.

Mission scientists still need to analyze data from the last two years and on into the future. Kepler will be making observations for a while yet to come; its nominal mission is set to end in November 2012, but the Kepler team is preparing a proposal to extend the instrument's operations for another year or more.

Kepler's finds should only get more exciting as time goes on, researchers say.
"We're pushing down to smaller planets and longer orbital periods," said Natalie Batalha, Kepler deputy science team lead at Ames.

To flag a potential planet, the instrument generally needs to witness three transits. Planets that make three transits in just a few months must be pretty close to their parent stars; as a result, many of the alien worlds Kepler spotted early on have been blisteringly hot places that aren't great candidates for harboring life as we know it.

Given more time, however, a wealth of more distantly orbiting — and perhaps more Earthlike — exoplanets should open up to Kepler. If intelligent aliens were studying our solar system with their own version of Kepler, after all, it would take them three years to detect our home planet.

Sources MSN



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Published by Gusti Putra at: 11:52 PM
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Thursday, November 17, 2011

Calling All Astronauts: NASA Has a Job Opening For You


Astronauts! They’re just like us. Well, at least while they’re job hunting.

The International Space Station could be your new office.
The National Aeronautics & Space Administration has an opening for an astronaut based in the Lyndon B. Johnson Space Center. They’ve also gone the contemporary route for job recruitment by posting the position on the job website USAJobs. Folded in with ads for positions such as IT specialist and medical technologist, the open call posting is seeking candidates who have a “sense of daring” and a “probing mind” for a position that, unsurprisingly, could require “[f]requent travel.” Of course, there are more concrete requirements as well, including U.S. citizenship, a bachelor’s degree in engineering, science or math and at least three years worth of relevant professional experience.

Does this describe your skill set? Are you looking for work? Well, you could be one of the lucky applicants who are thoroughly vetted and selected to join the next class of astronauts expected to work on the International Space Station and, perhaps, beyond. The selection process is apparently quite stringent as NASA’s last recruitment round drew thousands of applications for only nine spots. Clearly, competition will be stiff.

“If you’re selected and you make it through that process, the experience is well worth the wait, I think,” Janet Kavandi, director of flight crew operations at Johnson Space Center told MSNBC. “Anyone who’s been to space can say that it was definitely worth all the hard work to get there.” NewsFeed, thwarted not by disinterest but by our useless liberal arts and humanities degrees, is already jealous of the future space jet-setters.

Quoted from TIME
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Wednesday, November 02, 2011

Pluto — No Longer a Planet — Has a Twin Sister


If Pluto's looking for someone — or something — to blame for being drummed out of the planetary corps back in 2006, it need look no further than Eris. The solar system's ninth planet had long had its detractors — purists who sniffed at its tiny size and irregular orbit — but it was in 2005 things came to a head.

An artist's rendering of the dwarf planet Eris
NASA
That was when Caltech astronomer Mike Brown found a tiny, frigid world orbiting some three times further out than Pluto. Brown had been finding similar objects in the Kuiper Belt — the massive band of comet-like bodies that circles the solar system — for years. But all of them were smaller than 2,320 km (1,440 miles) across, the modest dimensions of Pluto. Eris (which Brown nicknamed Xena, before the International Astronomical Union settled on its official name), though, was evidently a little larger — and that discovery set off an international furor. If Pluto was a planet, Eris obviously was too. And if so, why not Quaoar and Sedna, and several other worlds, which were smaller than Pluto, but not by much?

In the end, the astronomical union avoided the whole mess by demoting Pluto and the rest to the status of "dwarf planet," infuriating Pluto partisans around the world (an odd category, when you think about it: there are no rabid fan clubs for Jupiter or Mercury or Mars). Brown ultimately poked Pluto lovers again when he wrote a book titled How I Killed Pluto and Why It Had It Coming. The one hope Pluto fans had for revenge was that it was very tough to pin down Eris' size exactly. Maybe it would end up proving smaller than Pluto after all. That wouldn't restore Pluto to full planethood, but it would make them feel better, anyway.

Now a team of astronomers has finally nailed down Eris' size with high precision, and the answer is that it may be bigger than Pluto, or it may not — but the difference is probably pretty small either way. Much more significant, says Bruno Sicardy of the Paris Observatory, lead author of a paper on the discovery in the latest Nature, is that despite their comparable size, Eris is some 27% more massive than Pluto. What's more, it's prettier, with a surface Sicardy describes as "brighter than new fallen snow."

Measuring the size of something 24 billion km (15 billion miles) away is no mean feat. It is, says Sicardy, "like measuring a coin at a distance of 100 miles." Even with the Hubble telescope, Eris looks like a featureless pinpoint. The only way to gauge its size accurately was to wait for it to pass in front of a distant star, in what's known as an occultation. All you have to do then is time how long it takes the star to reappear on the other side and you can calculate the size of the obscuring object. Two years ago, Sicardy and his team found a good star in what seemed to be the right spot — but they couldn't be sure the two bodies would actually cross paths until it was about to happen. "You need to know the location of the star and the orbit of Eris very, very precisely."

Fortunately, they chose well. Last November, the occultation took place. "It's amazing it works!" says Sicardy, who knew better than anyone how hard it was to predict. "The star disappears and then reappears!"

If the occultation had been spotted from only one telescope, it wouldn't have been very useful, since the star might have barely skimmed Eris' edge rather than passed behind its fat middle. But two telescopes, both in Chile, managed to see the event take place. They were far enough apart and saw it from different enough angles that they captured different parts of Eris. Assuming the object is roughly spherical (not unreasonable), they could use those parts of the overall disc to trace out the rest and thus calculate its size. The answer they got: 2,326 km (1,445 miles), with an uncertainty of half a percent. That margin of error actually straddles Pluto's accepted dimensions. At its greatest possible size, Eris is bigger than Pluto; at its least, it's smaller.

Such exquisite mathematical ambiguity is made less certain still by the fact that unlike Eris, Pluto has a thin atmosphere, so when it goes in front of a star, the star doesn't wink out. It fades. Pluto may be a few tens of kilometers smaller than Eris, or a few tens of kilometers bigger.

Whatever Pluto's exact dimensions, the fact doesn't have much significance beyond cosmic bragging rights. What does matter a lot is Eris' surprisingly large mass, which means it has considerably more rock underneath its icy surface than Pluto. As Brown writes on his blog, "explaining why Pluto and Eris are so different is going to keep us busy for many years, I suspect."

Scientists also have to explain why Eris is so blindingly bright. Its surface should darken over the years as dust and cosmic rays mar its pristine whiteness, and yet it's kept its youthful sheen. The answer, the scientists suspect: when Eris comes closer to the sun in its highly elongated orbit, surface ice warms up to form a temporary atmosphere. When it recedes, the atmosphere condenses again to form a new coating of ice just a millimeter thick. "Unfortunately," says Sicardy, "we will have to wait 250 years to test this idea." But Pluto is currently moving further out, so the same thing might happen to it in reverse. "Within 20 years or so," he says "we could see Pluto begin to brighten" as its atmosphere starts to freeze out, confirming the hypothesis.

Astronomers won't have to wait that long to firm up their understanding of the outer solar system, though: Sicardy and his team already have occultations in hand from other Kuiper Belt objects. Measuring their size and density will help theorists figure out how these miniworlds came to be.

Brown, meanwhile, holds out an even more exciting prospect. "There are surely even larger dwarf planets out there," he writes. "It is only a matter of time before both Pluto and Eris are supplanted." Presumably, one hopes, before Eris develops a fan base of its own.

Sources: Science
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Monday, October 24, 2011

Astronauts go deep for undersea 'asteroid' trip

'Aquanauts' will spend nearly two weeks at a depth of 60 feet, off the coast of Florida

After waiting out stormy weather and rough seas, a team of astronauts successfully began a tough mission Thursday, but instead of launching into space, this crew is headed for the ocean floor on a mock asteroid trip.
NASA's NEEMO 15 expedition will simulate aspects of a mission to an asteroid.
In this illustration, a configured rock wall can be seen near the underwater Aquarius laboratory.
The six "aquanauts" splashed down at 2:15 p.m. EDT (1815 GMT) and will spend the next 13 days living inside a small laboratory called Aquarius on the ocean floor during their undersea mission to test different ways to explore an asteroid. The expedition was originally scheduled to begin Monday, Oct. 17, but heavy rain and storms in the area made the waters unsafe for the dive, NASA officials said.

This is NASA's 15th NEEMO (NASA Extreme Environment Mission Operations) voyage to test technology and innovative engineering solutions for future space missions. NEEMO 15, however, is the first to experiment with concepts of how to visit and explore an asteroid. [Gallery: Visions of NASA Asteroid Mission]

The weather delays alone make this a good simulation of real spaceflight, NEEMO 15 aquanaut David Saint-Jacques, of the Canadian Space Agency, joked to SPACE.com.

Working underwater 
For nearly two weeks, the NEEMO 15 crew will live and work at the Aquarius Underwater Laboratory, which sits 60 feet (18 meters) below the Atlantic Ocean, about 3 1/2 miles off the shore of Key Largo, Fla. The agency uses this lab to approximate the weightless conditions in space and on an asteroid.

"There are a lot of aspects to what we can do on NEEMO that are directly comparable to flying in space," NASA astronaut and NEEMO 15 commander Shannon Walker told SPACE.com. "For this particular mission, because we're on the ocean floor, we're able to be mutually buoyant. It's one of the few places where we can do tasks as if we're on an asteroid."

To train for spacewalks on the exterior of the International Space Station, astronauts don full spacesuits and meticulously rehearse the steps in a giant swimming pool called the Neutral Buoyancy Laboratory (NBL) at NASA's Johnson Space Center in Houston. For NEEMO missions, working on the ocean floor helps astronauts and engineers create more realistic simulations to test concepts and technology.


"A lot of what we do here could be done in the NBL, but it would not have the air of reality," Saint-Jacques said. "It wouldn't put the operational pressure on everybody to do things just like on an asteroid mission. Here, it's really like a space mission. We have a mobile mission control, and lots of technical support to make this work."
A diver anchoring to a simulated asteroid surface
created for NASA's underwater NEEMO 15 mission.
Furthermore, since the aquanauts will be living underwater for 13 days, they practice diving techniques that allow their bodies to adapt and become saturated in the underwater environment to avoid the dangers of decompression sickness, or the bends. This enables the crew to work longer hours on the ocean floor.
"Because we are saturated, it means we can do two or three hours of [extravehicular activities] a day," Saint-Jacques said. "That would be impossible in the NBL."

Stepping stones to an asteroid 
NEEMO 15 will test various concepts of how to anchor to an asteroid, travel around on its surface, and perform experiments. During the mission, aquanauts will work outside the Aquarius lab for two to three hours each day.

A mock asteroid landscape on the ocean floor was set up earlier this year for the NEEMO 15 expedition. A fiberglass wall will also enable the aquanauts to test different ways to drill anchors to the surface of an asteroid. [Video: Rock & Roll Asteroids]

"Once we go off to an asteroid, that's a huge undertaking that we want to be in the best position to do things efficiently and successfully," Walker said. "We want to test all these different combinations and see what's the most efficient way to accomplish science tasks. Along with that, we're going to have to figure out how to attach to it and maneuver around the asteroid."

NASA astronauts Stan Love, Richard Arnold and Mike Gernhardt will also be at the controls of a small submarine, called the DeepWorker submersible. The submarine will be used in place of the agency's Space Exploration Vehicle, which is a rover that is being developed for a future manned asteroid mission.

Future space missions 
The results of NEEMO 15 will help NASA plan for a future manned mission to a space rock.

"NASA's exploration branch is really keen on this mission," Saint-Jacques said. "They are waiting for the results to inform their engineering teams as to what are the good architectural solutions to pursue. It's a very smart way to work because before you get the big engineering team working and spend a lot of time, manpower and resources, you do these relatively cheap investigations to make sure you're on the right track."

Walker, Saint-Jacques and Takuya Onishi, of the Japan Aerospace Exploration Agency, will live aboard the Aquarius lab for 13 days. Noted Mars planetary scientist Steve Squyres and two veteran divers, James Talacek and Nate Bender of the University of North Carolina, Wilmington, will also provide support and work with the NEEMO 15 crew underwater.

Canadian astronaut Jeremy Hansen and Jeanette Epps of NASA will guide the NEEMO 15 crewmembers as capsule communicators in Mission Control.

As part of the agency's new direction, NASA is aiming to send humans on a mission to an asteroid by the year 2025. Walker said she is excited to play a role in planning such a mission, and would be keen on visiting an asteroid in the future.


"I would love to go wherever NASA wants to go," Walker said. "I might be near the end of my career, but I would still be interested."

The NEEMO mission is a joint venture between NASA, the National Oceanic and Atmospheric Administration (NOAA), which owns the Aquarius laboratory, and the University of North Carolina, Wilmington, which operates the underwater facility.

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Scientist: Satellite must have crashed into Asia

BERLIN (AP) — A defunct German research satellite crashed into the Earth somewhere in Southeast Asia on Sunday, U.S. scientist said — but no one is still quite sure where.

Undated artist rendering provided by EADS Astrium shows the scientific satellite ROSAT.
Andreas Schuetz, a spokesman for the German Aerospace Center, said Saturday Oct. 22, 2011
the best estimate is still that the ROSAT scientific research satellite
will impact sometime between late Saturday and Sunday 1200 GMT.
Photo: EADS Astrium / AP
Most parts of the minivan-sized ROSAT research satellite were expected to burn up as they hit the atmosphere at speeds up to 280 mph (450 kph), but up to 30 fragments weighing a total of 1.87 tons (1.7 metric tons) could have crashed, the German Aerospace Center said.

Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, said the satellite appears to have gone down over Southeast Asia. He said two Chinese cities with millions of inhabitants each, Chongqing and Chengdu, had been in the satellite's projected path during its re-entry time.
"But if it had come down over a populated area there probably would be reports by now," the astrophysicist who tracks man-made space objects told The Associated Press in a telephone interview.

Calculations based on data made available to scientists by the U.S. military indicate that satellite debris must have crashed somewhere east of Sri Lanka over the Indian Ocean, or over the Andaman Sea off the coast of Myanmar, or further inland in Myanmar or as far inland as China, he said.

The satellite entered the atmosphere between 0145 GMT to 0215 GMT Sunday (9:45 p.m. to 10:15 p.m. Saturday EDT) and would have taken 15 minutes or less to hit the ground, the German Aerospace Center said. Hours before the re-entry, the center said the satellite was not expected to land in Europe, Africa or Australia.

There were no immediate reports from Asian governments or space agencies about the fallen satellite.
The satellite used to circle the planet in about 90 minutes, and it may have traveled several thousand kilometers (miles) during its re-entry, rendering exact predictions of where it crashed difficult.

German space agency spokesman Andreas Schuetz said a falling satellite also can change its flight pattern or even its direction once it sinks to within 90 miles (150 kilometers) above the Earth.

Schuetz said the agency was waiting for data from scientific partners around the globe. He noted it took the U.S. space agency NASA several days to establish where one of its satellites had hit last month.

The 2.69-ton (2.4 metric ton) scientific ROSAT satellite was launched in Cape Canaveral, Florida, in 1990 and retired in 1999 after being used for research on black holes and neutron stars and performing the first all-sky survey of X-ray sources with an imaging telescope.

ROSAT's largest single fragment that could have hit is the telescope's heavy heat-resistant mirror.
"The impact would be similar to, say, an airliner having dropped an engine," said McDowell. "It would damage whatever it fell on, but it wouldn't have widespread consequences."

A dead NASA satellite fell into the southern Pacific Ocean last month, causing no damage but spreading debris over a 500-mile (800-kilometer) area.

Since 1991, space agencies have adopted new procedures to lessen space junk and having satellites falling back to Earth. NASA says it has no more large satellites that will fall back to Earth uncontrolled in the next 25 years.

Quoted from Seattlepi

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Astronauts' photographs from space flights and moon landing go on sale


They often used Hasselblad cameras from Sweden modified only by the addition of a bigger button to press, but then taking pictures when you are an astronaut in a bulky, pressurised suit is clearly tricky.
Buzz Aldrin walking on the moon during the Apollo 11 mission.
Neil Armstrong, the photographer, is reflected in Aldrin's visor. Photograph: Nasa/AFP/Getty Images
Many of the astronauts' early space photographs have become extremely famous, more for their otherworldly beauty than their scientific value.

And now some are to appear in the UK's first dedicated sale of vintage Nasa photographs.

Bloomsbury Auctions in London has announced details of the first specialist sale of images showing how man came to land on the moon.
"We are thrilled," said Sarah Wheeler, Bloomsbury's photographs specialist.

"What we are offering are historic artefacts – rare, iconic, vintage photographs taken by the astronauts themselves and printed within days of their return to Earth and very different from today's downloadable images."

More than 280 photographs, with estimated values ranging from £200 to £10,000, will be auctioned. They have been collected over decades by Frenchman Victor Martin-Malburet, who has exhibited them in Paris and Saint-Etienne.

Some of the most striking images in the collection are of Ed White's spacewalk in 1965, part of the Gemini 4 mission.

White was the first American to walk in space. His walk was photographed by fellow astronaut James McDivitt – who was looking out of the craft without really being able to see what he was shooting at.

"He was remarkably successful considering he couldn't really frame the pictures," said a Bloomsbury spokesman.

Other highlights include the first view of Earth from the moon, taken on 23 August 1966 and shown publicly on 10 September.

It is a grainy image but the technological feat of making it happen at all should not be underestimated – the pictures were taken by an unmanned satellite which also developed them and sent them back to Earth as radio waves.

There are also images of a Gemini 12 spacewalk by Buzz Aldrin in November 1966 including one taken by the astronaut himself – using his modified Hasselblad with the big button – which Bloomsbury has billed as the "first self-portrait in space".

One of the most recognisable images is Earthrise, taken by William Anders on Christmas Eve in 1968 from Apollo 8.

Anders explained that they had spent all their time on Earth studying the moon and when they got there, they could see a fragile and delicate-looking Earth.

"I was immediately almost overcome by the thought that we came all this way to the moon, and yet the most significant thing we're seeing is our own home planet, the Earth."

And of course there is Apollo 11 – the mission that landed the first men on the moon – and photographs by Aldrin of his footprints.

Because flight leader Neil Armstrong was often taking the photographs, there are not many pictures of him. But there is the famous image Armstrong took of Aldrin in which he is reflected in Aldrin's goldplated visor.

The photographs are all vintage prints – made soon after the event depicted. The more expensive ones are the large-format prints that were often presented to scientists or dignitaries. The sale takes place on 3 November.

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Published by Gusti Putra at: 12:46 AM
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Sunday, October 23, 2011

Dead satellite tumbles to Earth — but where?

Up to 30 fragments weighing a total of 1.87 tons could have hit the planet, experts believe


Scientists were trying to establish how and where a defunct research satellite returned to the Earth Sunday, after warning that some parts might survive re-entry and crash at up to 280 mph.
There was no immediate solid evidence to determine above which continent or country the ROSAT scientific research satellite entered the atmosphere, said Andreas Schuetz, spokesman for the German Aerospace Center.

Most parts of the minivan-sized German satellite were expected to burn up, but up to 30 fragments weighing a total of 1.87 tons could have hit the planet.
Citing officials, Space.com reported that ROSAT slammed into Earth's atmosphere sometime between 9:45 p.m. and 10:15 p.m. ET on Saturday.

Scientists were no longer able to communicate with the dead satellite and it must have traveled about 12,500 miles in the final 30 minutes before entering the atmosphere, Schuetz said.


Schuetz said it could take days to determine exactly where pieces of the satellite had fallen, but that the agency had not received any reports that it had hit any populated areas.
"We have no such information," he said Sunday.


Based on ROSAT's orbital path, these fragments could be scattered along a swath of the planet about 50 miles wide, German aerospace officials have said.

Scientists said hours before the re-entry into the atmosphere that the satellite was not expected to hit over Europe, Africa or Australia. According to a precalculated path it could have been above Asia, possibly China, at the time of its re-entry, but Schuetz said he could not confirm that.

The 2.69-ton scientific ROSAT satellite was launched in 1990 to study X-ray radiation from stars, comets, supernovas, nebulas and black holes, among other things. The satellite was originally designed for an 18-month mission, but it far outlived its projected lifespan. [Photos of Doomed ROSAT Satellite]


Heat-resistant mirror 

It retired in 1999 after performing the first all-sky survey of X-ray sources with an imaging telescope.

The largest single fragment of ROSAT that could hit into the earth is the telescope's heat-resistant mirror.

During its mission, the satellite orbited about 370 miles above the Earth's surface, but since its decommissioning it has lost altitude, circling at a distance of only 205 miles above ground in June for example, the agency said.

Even in the last days, the satellite still circled the planet every 90 minutes, making it hard to predict where on Earth it would eventually come down.

Mission controllers initially estimated that ROSAT could fall to Earth in November, but increased solar activity caused the satellite's orbit to decay faster than originally expected. As the sun's activity ramps up, it heats up and expands the atmosphere, which creates more drag on satellites in orbit.


'Catch them' 

ROSAT's fall from space shone a spotlight on the growing problem of debris in space.

"One option is we want to be able to catch uncontrolled satellites in the future," Jan Woerner, head of the executive board of the German Aerospace Center, told Space.com. "We're working on such a mission to catch them, depending on their state, and have a controlled re-entry or send them to a graveyard, in order to prevent this situation in the future."

A dead NASA satellite fell into the southern Pacific Ocean last month, causing no damage, despite fears it would hit a populated area and cause damage or kill people.


Experts believe about two dozen metal pieces from the bus-sized satellite fell over a 500-mile span.
The German space agency puts the odds of somebody somewhere on Earth being hurt by its satellite at one in 2,000 — a slightly higher level of risk than was calculated for the NASA satellite. But any one individual's odds of being struck are one in 14 trillion, given there are 7 billion people on the planet.

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Published by Gusti Putra at: 10:18 PM
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Thursday, October 20, 2011

Dark matter mystery deepens

Dark matter should be densely packed in the centers of galaxies. Instead, new measurements of two dwarf galaxies show that they contain a smooth distribution of dark matter.


Like all galaxies, our Milky Way is home to a strange substance called dark matter. Dark matter is invisible, betraying its presence only through its gravitational pull. Without dark matter holding them together, our galaxy’s speedy stars would fly off in all directions.
This artist's conception shows a dwarf galaxy
seen from the surface of a hypothetical exoplanet.
A new study finds that the dark matter in dwarf galaxies
 is distributed smoothly rather than being clumped
at their centers. This contradicts simulations
using the standard cosmological model known as lambda-CDM.
Credit: David A. Aguilar (CfA)

The nature of dark matter is a mystery — a mystery that a new study has only deepened.

“After completing this study, we know less about dark matter than we did before,” said Matt Walker from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

The standard cosmological model describes a universe dominated by dark energy and dark matter. Most astronomers assume that dark matter consists of “cold” (i.e. slow-moving) exotic particles that clump together gravitationally. Over time, these dark matter clumps grow and attract normal matter, forming the galaxies we see today.

Cosmologists use powerful computers to simulate this process. Their simulations show that dark matter should be densely packed in the centers of galaxies. Instead, new measurements of two dwarf galaxies show that they contain a smooth distribution of dark matter. This suggests that the standard cosmological model may be wrong.

“Our measurements contradict a basic prediction about the structure of cold dark matter in dwarf galaxies. Unless or until theorists can modify that prediction, cold dark matter is inconsistent with our observational data,” Walker said.

Dwarf galaxies are composed of up to 99 percent dark matter and only 1 percent normal matter like stars. This disparity makes dwarf galaxies ideal targets for astronomers seeking to understand dark matter.

Walker and Jorge Penarrubia from the University of Cambridge, United Kingdom, analyzed the dark matter distribution in two Milky Way neighbors — the Fornax and Sculptor dwarf galaxies. These galaxies hold one million to 10 million stars, compared to about 400 billion in our galaxy. The team measured the locations, speeds, and basic chemical compositions of 1,500 to 2,500 stars.

“Stars in a dwarf galaxy swarm like bees in a beehive instead of moving in nice, circular orbits like a spiral galaxy,” said Penarrubia. “That makes it much more challenging to determine the distribution of dark matter.”

Their data showed that in both cases, the dark matter is distributed uniformly over a relatively large region, several hundred light-years across. This contradicts the prediction that the density of dark matter should increase sharply toward the centers of these galaxies.

“If a dwarf galaxy were a peach, the standard cosmological model says we should find a dark matter “pit” at the center. Instead, the first two dwarf galaxies we studied are like pitless peaches,” said Penarrubia.

Some have suggested that interactions between normal and dark matter could spread out the dark matter, but current simulations don’t indicate that this happens in dwarf galaxies. The new measurements imply that either normal matter affects dark matter more than expected, or dark matter isn’t “cold.” The team hopes to determine which is true by studying more dwarf galaxies, particularly galaxies with an even higher percentage of dark matter.

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Published by Gusti Putra at: 10:36 PM
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VISTA finds new globular star clusters and sees right through the heart of the Milky Way

This survey has also turned up the first star cluster that is far beyond the center of the Milky Way on the other side of our galaxy.

This image from VISTA is a tiny part of the VISTA Variables
in the Via Lactea (VVV) survey that is systematically studying
the central parts of the Milky Way in infrared light.
On the right lies the globular star cluster UKS 1
and on the left lies a much less conspicuous new discovery,
VVV CL001 — a previously unknown globular.
The new globular appears as a faint grouping of
stars about 25% of the width of the image from the left edge,
and about 60% of the way from bottom to top.
Credit: ESO/D. Minniti/VVV Team
Two newly discovered globular clusters have been added to the total of just 158 known globular clusters in our Milky Way. They were found in new images from the European Southern Observatory’s (ESO) VISTA survey telescope as part of the variables in the Via Lactea (VVV) survey. This survey has also turned up the first star cluster that is far beyond the center of the Milky Way and whose light has had to travel right through the dust and gas in the heart of our galaxy to get to us.

The dazzling globular cluster called UKS 1 dominates the right-hand side of the image from ESO’s VISTA survey telescope at the Paranal Observatory in Chile. But if you can drag your gaze away, there is a surprise lurking in this rich star field — a fainter globular cluster that was discovered in the data from one of VISTA’s surveys. You will have to look closely to see the other star cluster, which is called VVV CL001 — it is a small collection of stars in the left half of the image.

But VVV CL001 is just the first of VISTA’s globular discoveries. The same team has found a second object, dubbed VVV CL002. This small and faint grouping may also be the globular cluster that is the closest known to the center of the Milky Way. The discovery of a new globular cluster in our Milky Way is rare. The last one was discovered in 2010, and only 158 globular clusters were known in our galaxy before the new discoveries.

These new clusters are early discoveries from the VVV survey that is systematically studying the central parts of the Milky Way in infrared light. Dante Minniti leads the VVV team from the Pontifica University of Chile and Philip Lucas from the University of Hertfordshire, United Kingdom.

As well as globular clusters, VISTA is finding many open, or galactic, clusters, which generally contain fewer, younger stars than globular clusters and are far more common. Another newly announced cluster, VVV CL003, seems to be an open cluster that lies in the direction of the heart of the Milky Way, but much further away, about 15,000 light-years beyond the center. This is the first such cluster to be discovered on the far side of the Milky Way.

Given the faintness of the newly found clusters, it is no wonder that they have remained hidden for so long; up until a few years ago, UKS 1, which easily outshines the newcomers, was actually the dimmest known globular cluster in the Milky Way. Because of the absorption and reddening of starlight by interstellar dust, these objects can only be seen in infrared light and VISTA, the world’s largest survey telescope that is ideally suited to searching for new clusters hidden behind dust in the central parts of the Milky Way.

One intriguing possibility is that VVV CL001 is gravitationally bound to UKS 1, making these two stellar groups the Milky Way’s first binary globular cluster pair. But this could just be a line-of-sight effect with the clusters actually separated by a vast distance.

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Published by Gusti Putra at: 10:22 PM
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Blue stragglers: Astronomers discover how mysterious stars stay so young

Scientists report that a mechanism known as mass transfer explains the origins of these old stars that still burn hot and blue.

Mysterious “blue stragglers” are old stars that appear younger than they should — they burn hot and blue. Several theories have attempted to explain why they don’t show their age, but, until now, scientists have lacked the crucial observations with which to test each hypothesis.

An artist's conception showing a blue straggler
 being created by mass transfer in a binary star system.
The giant star, seen in the upper left of the illustration,
 has lost hold of its outer envelope.
This material is pulled towards its partner,
forming an accretion disk, and is eventually
consumed by the "proto-blue straggler."
Soon the giant star will donate the remainder of
its envelope, leaving only the half-solar-mass
 white dwarf core
(shown peaking through the giant's tenuous envelope)
as the companion to the blue straggler.
Credit: Aaron M. Geller
Armed with such observational data, Aaron M. Geller from Northwestern University in Chicago, Illinois, and Robert Mathieu from the University of Wisconsin-Madison report that a mechanism known as mass transfer explains the origins of the blue stragglers. Essentially, a blue straggler eats up the mass, or outer envelope, of its giant-star companion. This extra fuel allows the straggler to continue to burn and live longer while the companion star is stripped bare, leaving only its white dwarf core.

The majority of blue stragglers in their study are in binaries — they have a companion star. “It’s really the companion star that helped us determine where the blue straggler comes from,” said Geller. “The companion stars orbit at periods of about 1,000 days, and we have evidence that the companions are white dwarfs. Both point directly to an origin from mass transfer.”

The astronomers studied the NGC 188 open cluster, which is in the constellation Cepheus, situated in the sky near Polaris, the North Star. This cluster is one of the most ancient open star clusters, but it features these mysterious, young-looking blue stragglers.

The cluster has around 3,000 stars, all about the same age, and has 21 blue stragglers. Geller and Mathieu are the first to use detailed observational data from the WIYN Observatory in Tucson, Arizona, of the blue stragglers in NGC 188.

They used the information to analyze and compare the three main theories of blue straggler formation: collisions between stars, mergers of stars, and mass transfer from one star to another. The only one left standing was the theory of mass transfer.

The light from the blue stragglers’ companion stars is not actually visible in Geller and Mathieu’s observations. While the companions haven’t been seen directly, their effect on the blue stragglers is evident: Each companion pulls gravitationally on its blue straggler and creates a “wobble” as it orbits, and this allows astronomers to measure the mass of the companion stars. The WIYN data show that each companion star is about half the mass of the Sun, which is consistent with a white dwarf.

The other two origin theories — collisions and mergers — require the companion stars to be more massive than what is observed. In fact, in both scenarios, some of the companion stars could be bright enough to be visible in the WIYN data, which is not the case.

“We think we have a good understanding of stellar evolution, but it doesn’t predict blue stragglers,” Geller said. “People have been trying to explain the origin of blue stragglers since their discovery in 1953, and now we have the detailed observations needed to identify how they were created. I’ve always enjoyed trying to get to the bottom of a mystery.”

“As so often happens in astronomy, it is the objects that you don’t see that provide the critical clues,” said Mathieu. “Now we will use the Hubble Space Telescope to search for the ultraviolet light in which white dwarf secondary stars shine.”

Geller, Mathieu, and their colleagues will have, in about a year’s time, observations from Hubble that will tell them if the blue stragglers’ companions are, indeed, white dwarfs.

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