2013년 11월 27일 수요일

Weird Black Hole's Incredible Brightness Perplexes Scientists

A black-hole system in a neighboring galaxy is twice as bright as astronomers had thought possible, a new study reports.
The incredible luminosity of the system in question, which resides about 22 million light-years from Earth in the Pinwheel Galaxy, may force a rethink of the theories that explain how some black holes radiate energy, researchers said.

"As if black holes weren’t extreme enough, this is a really extreme one that is shining as brightly as it possibly can," study co-author Joel Bregman of the University of Michigan said in a statement. "It’s figured out a way to be more luminous than we thought possible."

The astronomers studied a system called ULX-1, which consists of a black hole and a companion star that orbit each other. As its name suggests — ULX is short for "ultraluminous X-ray source" — ULX-1 generates prodigious amounts of high-energy X-ray light, which is emitted by material spiraling down into the black hole's maw.

This light is so intense, in fact, that astronomers had suspected that ULX-1 contains an intermediate-mass black hole — one that harbors between 100 and 1,000 times the mass of the sun. But the new study suggests that the black hole is actually on the small side.

The research team, led by Jifeng Liu of the Chinese Academy of Sciences in Beijing, studied ULX-1 using the Gemini Observatory in Hawaii and two NASA spacecraft, the Hubble Space Telescope and the Chandra X-ray Observatory.

Spectroscopic analysis revealed that the companion star in ULX-1 is a big, hot type known as a Wolf-Rayet star. With this information in hand, the team could then infer the star's mass from its brightness, pegging it at 19 times the mass of the sun.

The researchers also found that the star and the black hole orbit each other once every 8.2 days. This allowed them to estimate the black hole's mass at between 20 to 30 times the mass of the sun.

ULX-1 thus apparently contains not an intermediate-mass black hole, but a stellar one — an object that forms after a star dies and collapses on itself. So astronomers have still not definitively found a middleweight black hole, which some researchers think may be the seeds of the supermassive monsters that lurk at the heart of most, if not all, galaxies.

"Our findings may turn the trend of taking ultraluminous X-ray sources as promising intermediate black hole candidates," Liu said in a statement.
The study team isn't sure how the ULX-1 system manages to emit so much light. It's possible, researchers said, that the black hole may be feeding off the companion's stellar wind — the stream of charged particles flowing from its atmosphere.

This mechanism had previously been regarded as too inefficient to power an ultraluminous X-ray source, but ULX-1 may send theorists back to the drawing board.
"Our work shows, based on our conclusion of a stellar mass black hole, that our understanding of the black hole radiation mechanism is incomplete and needs revision," Liu told SPACE.com via email.

Source of Article: Space.com

Figure Eights and Peanut Shells: How Stars Move at the Center of the Galaxy

Two months ago astronomers created a new 3D map of stars at the centre of our Galaxy (the Milky Way), showing more clearly than ever the bulge at its core. Previous explanations suggested that the stars that form the bulge are in banana-like orbits, but a paper published this week in Monthly Notices of the Royal Astronomical Society suggests that the stars probably move in peanut-shell or figure of eight-shaped orbits instead.

The difference is important; astronomers develop theories of star motions to not only understand how the stars in our galaxy are moving today but also how our galaxy formed and evolves. The Milky Way is shaped like a spiral, with a region of stars at the centre known as the "bar," because of its shape. In the middle of this region, there is a "bulge" that expands out vertically.

In the new work Alice Quillen, professor of astronomy at the University of Rochester, and her collaborators created a mathematical model of what might be happening at the centre of the Milky Way. Unlike the Solar System where most of the gravitational pull comes from the Sun and is simple to model, it is much harder to describe the gravitational field near the centre of the Galaxy, where millions of stars, vast clouds of dust, and even dark matter swirl about. In this case, Quillen and her colleagues considered the forces acting on the stars in or near the bulge.

As the stars go round in their orbits, they also move above or below the plane of the bar. When stars cross the plane they get a little push, like a child on a swing. At the resonance point, which is a point a certain distance from the centre of the bar, the timing of the pushes on the stars is such that this effect is strong enough to make the stars at this point move up higher above the plane. (It is like when a child on the swing has been pushed a little every time and eventually is swinging higher.) These stars are pushed out from the edge of the bulge.

The resonance at this point means that stars undergo two vertical oscillations for every orbital period. But what is the most likely shape of the orbits in between? The researchers showed through computer simulations that peanut-shell shaped orbits are consistent with the effect of this resonance and could give rise to the observed shape of the bulge, which is also like a peanut-shell.

Next month the European Space Agency will launch the Gaia spacecraft, which is designed to create a 3D map of the stars in the Milky Way and their motions. This 3D map will help astronomers better understand the composition, formation and evolution of our Galaxy."It is hard to look back into the past of our galaxy and know what was there, but simulations can give us clues," explained Quillen. "Using my model I saw that, over time, the resonance with the bar, which is what leads to these peculiarly shaped orbits, moves outwards. This may be what happened in our Galaxy."

"Gaia will generate huge amounts of data -- on billions of stars," said Quillen. This data will allow Quillen and her colleagues to finesse their model further. "This can lead to a better understanding of how the Milky Way might have evolved into the shape it has today."Quillen explained that there are different models as to how the galactic bulge was formed. Astronomers are interested in finding out how much the bar has slowed down over time and whether the bulge "puffed up all at once or slowly." Understanding the distributions of speeds and directions of motion (velocities) of the stars in the bar and the bulge might help determine this evolution.

"One of the predictions of my model is that there is a sharp difference in the velocity distributions inside and outside the resonance," Quillen said. "Inside -- closer to the galactic centre -- the disk should be puffed up and the stars there would have higher vertical velocities. Gaia will measure the motions of the stars and allow us to look for variations in velocity distributions such as these."

To be able to generate a model for the orbits of stars in the bulge, Quillen needed to factor in different variables. She first needed to understand what happens at the region of the resonance, which depends on the speed of the rotating bar and the mass density of the bar.

"Before I could model the orbits, I needed the answer to what I thought was a simple question: what is the distribution of material in the inner galaxy?" Quillen said. "But this wasn't something I could just look up. Luckily my collaborator Sanjib Sharma was able to help out."

Sharma worked out how the speed of circular orbits changed with distance from the galactic centre (called the rotation curve). Using this information, Quillen could compute a mass density at the location of the resonance, which she needed for her model.

Quillen was also able to combine the new orbit models with the speed of the bar (which is rotating) to get a more refined estimate of the mass density 3000 light years from the Galaxy centre (about one eighth of the distance from the centre of the Galaxy to Earth), which is where the edge of the bulge is.

Source of Article: Sciencedaily.com

2013년 11월 22일 금요일

Strange Discovery: Giant Dust Ring Found Near Venus Orbit

Scientists have found a huge, diffuse ring of dust near the orbit of Venus, marking the second time such a structure has been discovered in our solar system.

The dust ring stretches about 137 million miles (220 million kilometers) from end to end, though it's just 10 percent denser than the background cloud that pervades interplanetary space and produces the glow known as zodiacal light, researchers said.

"If we could see it unaided from Earth (which of course we can't because it is far too faint), it would stretch 45 degrees either side of the sun," study lead author Mark Jones, of The Open University in the United Kingdom, told SPACE.com via email. 

A similar ring was detected near Earth's orbit about 20 years ago, Jones added.
"So we have added to our knowledge of the 'geography' of the solar system," he said.
Several different space missions — including the Soviet Union's Venera 9 and 10 probes in the 1970s — have spotted hints of a dust ring near Venus, but the evidence had not been conclusive. So Jones and his colleagues set out to see if the structure could be confirmed.

They modeled the way a ring near Venus should scatter light, then looked for the feature in images captured by NASA's twin STEREO (Solar TErrestrial RElations Observatory) probes, which have been studying the sun since launching in late 2006.

The STEREO images did indeed reveal a dust ring. But, in something of a surprise, it looks significantly different than the ring near Earth's orbit, featuring two distinct "steplike" components. One of these steps is interior to Venus' orbit, while the other lies outside the planet's path around the sun, researchers said.

Such dust rings have arisen from the trapping of interplanetary dust into orbits resonant with those of Venus and Earth. (Resonant orbits are those whose periods are related by a ratio of two small integers, such as 2 and 3; such an orbital relationship often magnifies the gravitational influence two celestial bodies exert on each other.)

While the rings themselves are likely long-lived structures, the individual pieces that comprise them don't stick around for millions of years.

"The lifetime of dust trapped in the ring is only about 100,000 years, so it does not provide much of a clue to the formation of the solar system," Jones said. "However, the ring is very important in understanding what happens to interplanetary dust, which we know from other studies is formed from asteroid collisions and cometary dust."

Further study of the dust rings near Venus and Earth could also aid researchers peering beyond our solar system, he added.
"These rings will need to be understood for future missions which aim to image exoplanets using interferometers, because the rings can mask the signal from the exoplanet," Jones said.

Source of Article: Space.com

Brightest Explosion In the Universe Ever Seen Defies Astronomy Theories

A mysterious blast of light spotted earlier this year near the constellation Leo was actually the brightest gamma-ray burst ever recorded, and was triggered by an extremely powerful stellar explosion, new research reports.

On April 27, several satellites — including NASA's Swift satellite and Fermi Gamma-ray Space Telescope — observed an unusually bright burst of gamma radiation. The explosion unleashed an energetic jet of particles that traveled at nearly the speed of light, researchers said.

"We suddenly saw a gamma-ray burst that was extremely bright — a monster gamma-ray burst," study co-author Daniele Malesani, an astrophysicist at the Niels Bohr Institute at the University of Copenhagen in Denmark, said in a statement. "This [was] one of the most powerful gamma-ray bursts we have ever observed with the Swift satellite."

The gamma-ray burst was described in a series of studies published online today (Nov. 21) in the journal Science.

Gamma-ray bursts, or GRBs, are the most powerful type of explosions in the universe and typically mark the destruction of a massive star. The original stars are too faint to be seen, but the supernova explosions that signal a star's death throes can cause violent bursts of gamma radiation, researchers said.

Gamma-ray bursts are usually short but extremely bright. Still, ground-based telescopes have a tough time observing them because Earth's atmosphere absorbs the gamma radiation.

The extremely bright gamma-ray burst seen earlier this year, officially dubbed GRB 130472A, occurred in a galaxy 3.6 billion light-years away from Earth, which, though still far away, is less than half the distance at which gamma-ray bursts have previously been seen. 

This closer proximity to Earth enabled astronomers to confirm for the first time that one object can simultaneously create a powerful GRB and a supernova explosion.
"We normally detect GRBs at great distance, meaning they usually appear quite faint," study co-author Paul O'Brien, an astronomer at the University of Leicester in the United Kingdom, said in a statement. "In this case, the burst happened only a quarter of the way across the universe — meaning it was very bright. On this occasion, a powerful supernova was also produced — something we have not recorded before alongside a powerful GRB — and we will now be seeking to understand this occurrence."

The jet produced by the gamma-ray burst was formed when a massive star collapsed on itself and created a black hole at its center. This generated a blast wave that caused the stellar remnants to expand, producing a glowing shell of debris that was observed as an extremely bright supernova explosion.
After analyzing properties of the light produced by the gamma-ray burst, scientists determined that the original star was only three to four times the size of the sun, but was 20 to 30 times more massive. This extremely compact star was also rapidly rotating, the researchers said.

The GRB was the brightest and most energetic ever witnessed and triggered dynamic internal and external shock waves that are still not well understood. Though scientists have a clearer view of the violent explosion, mysteries remain. For instance, space telescopes detected more photons and more high-energy gamma-rays than theoretical models predicted for a gamma-ray burst of this magnitude.

Researchers are still investigating why the energy levels seen with GRB 130472A do not quite match predictions from existing models of gamma-ray bursts. Their results could lead to more refined theories about how particles are accelerated, which could help astronomers better predict the behavior of cosmic events.

"The really cool thing about this GRB is that because the exploding matter was traveling at [nearly] the speed of light, we were able to observe relativistic shocks," study co-author Giacomo Vianello, a postdoctoral scholar at Stanford University in California, said in a statement. "We cannot make a relativistic shock in the lab, so we really don't know what happens in it, and this is one of the main unknown assumptions in the model. These observations challenge the models and can lead us to a better understanding of physics."

Source of Article: Space.com

Neutrino Detector Finds Elusive Extraterrestrial Particles in 'Major Breakthrough'

For decades, scientists have been searching for ghostly neutrino particles from outer space, and now they have finally found them.

Using the IceCube Neutrino Observatory in Antarctica, researchers found the first evidence of neutrinos from outside the solar system since 1987. The findings open the door for a new era of astronomy that could reveal secrets of the strangest phenomena in the universe, scientists say. 

"It is a major breakthrough," said Uli Katz, a particle physicist at University of Erlangen-Nuremberg, in Germany, who was not involved with the research. "I think it is one of the absolute major discoveries in astro-particle physics," Katz told SPACE.com.

For the past century, scientists have pondered the source of cosmic rays, which contain the energy of a rifle bullet in a single atomic nucleus. It's thought that objects such as supernovas, black holes or gamma ray bursts mayproduce cosmic rays, but their origin is difficult to detect. Instead, scientists look for neutrinos — subatomic particles with no charge and very little mass — produced when cosmic rays interact with their surroundings. Billions of neutrinos pass through a square centimeter of Earth every second, and only a tiny fraction of them interact with matter.

IceCube is located inside a cubic kilometer of ice beneath the South Pole. The observatory consists of 5,160 digital optical modules suspended from 86 strings, which detect the tiny flashes of blue light emitted when neutrinos interact with molecules in the ice, known as Cherenkov radiation. Most neutrinos detected on Earth originate in Earth's atmosphere or the sun.

But in April 2012, IceCube detected two neutrino events with energies above 1 petaelectronvolt (PeV), the first definitively detected neutrinos from outside the solar system since 1987, during a supernova in the Large Magellanic Cloud. The new events, which scientists nicknamed "Bert" and "Ernie" (after the Sesame Street characters), were more than 1 million times the energies of the ones observed in 1987.

Deeper analysis revealed 28 high-energy neutrinos in IceCube data taken from May 2010 to May 2012. Each event was greater than 30 teraelectronvolts (TeV). The group reported preliminary results May 15 at the IceCube Particle Astrophysics Symposium at UW–Madison, and the full results were detailed online today (Nov. 21) in the journal Science.
"We have some really compelling evidence that we have neutrinos from beyond Earth's atmosphere and beyond the solar system," said study co-author Nathan Whitehorn, a physicist at the University of Wisconsin-Madison.

The number of events is too small to pinpoint the origin of the neutrinos, however.
"We do not yet have the number of neutrinos with which could paint a picture of the sky in the 'light of neutrinos,'" said Katz, who is leading the design of a rival neutrino observatory called KM3net, to be built underneath the Mediterranean Sea.

The next step will be answering questions such as where the neutrinos come from, what their energies are and what "flavor" they are (neutrinos come in three types). As IceCube gathers more data, " All of these questions are now starting to be addressed," Katz said.

Source of Article: Space.com

Mars Rover Curiosity Sidelined by Electrical Glitch

NASA's Mars rover Curiosity has stopped gathering data for a few days while engineers investigate an electrical problem that cropped up over the weekend.

On Sunday (Nov. 17), the mission team noticed a change in the voltage difference between the body of the Curiosity rover and its electricity-distributing power bus. They suspect that the culprit may be a "soft short," a sort of electrical leak through partially conductive material (as opposed to a "hard short," which can be caused by two exposed wires touching each other).
Curiosity is standing down temporarily while engineers try to understand what caused the problem, mission officials said.

"The vehicle is safe and stable, fully capable of operating in its present condition, but we are taking the precaution of investigating what may be a soft short," Curiosity project manager Jim Erickson, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement Wednesday (Nov. 20).

The voltage difference between Curiosity's chassis and its power bus had been about 11 volts since the rover touched down inside Mars' Gale Crater in August 2012. But the difference dropped to about 4 volts on Sunday, team members said.
If the cause was indeed a soft short, there could be more troubleshooting in Curiosity's future.

"Soft shorts reduce the level of robustness for tolerating other shorts in the future, and they can indicate a possible problem in whichever component is the site of the short," NASA officials wrote in a Curiosity status update Wednesday.

The issue appears to be unrelated to the software glitch that caused Curiosity to reboot its computer and go into a protective "safe mode" earlier this month, they added.
Curiosity's primary task is to determine if Mars has ever been capable of supporting microbial life. Mission scientists have already achieved this goal, finding that an area near the rover's landing site called Yellowknife Bay was indeed habitable billions of years ago.

The 1-ton robot is now embarked on a long drive from Yellowknife Bay to towering Mount Sharp, whose foothills hold a record of Mars' changing environmental conditions over time. If all goes according to plan, Curiosity should reach the mountain's base around the middle of next year, mission scientists have said.

Source of Article: Space.com

NASA Moon Dust Probe Begins Lunar Science Mission

NASA's newest lunar probe has officially begun its mission to study the moon's tenuous atmosphere like never before, as well as track how dust moves across the lunar sky.

The Lunar Atmosphere and Dust Environment Explorer, nicknamed LADEE for short, entered its science orbit on Wednesday (Nov. 20). The spacecraft now circles the moon once every two hours in an orbit, approaching within a mere 8 miles (12 kilometers) at its closest point and soaring 37 miles (60 km) overhead at its highest point, NASA officials said.

The $280 million LADEE spacecraft launched from a Virginia spaceport Sept. 6 and is expected to spend about 100 days probing the structure and composition of the thin atmosphere of the moon. 

"A thorough understanding of the characteristics of our lunar neighbor will help researchers understand other small bodies in the solar system, such as asteroids, Mercury, and the moons of outer planets," said LADEE program scientist Sarah Noble, at NASA Headquarters in Washington, in a statement Thursday (Nov. 21).

LADEE's orbit carries the car-size spacecraft around the moon's equator, allowing the probe repeatedly see the moon during lunar day and night. Scientists hope it will be able to see strange, glowing "rays and streamers" in the moon's atmosphere that were first seen in early unmanned lunar photographs and reports from Apollo lunar landing astronauts.
The spacecraft also carries a novel laser communications system to test high-speed data transmission technology for future space missions.

The LADEE spacecraft's low orbit around the moon requires meticulous attention to keep the probe from falling victim to the strange, lumpy lunar gravity.

"Due to the lumpiness of the moon's gravitational field, LADEE's orbit requires significant maintenance activity with maneuvers taking place as often as every three to five days, or as infrequently as once every two weeks," said Butler Hine, LADEE project manager at NASA's Ames Research Center in Moffett Field, Calif., said in a statement. "LADEE will perform regular orbital maintenance maneuvers to keep the spacecraft’s altitude within a safe range above the surface that maximizes the science return."

Source of Article: Space.com

How Humanity Could Deflect a Giant Killer Asteroid

Humanity has the skills and know-how to deflect a killer asteroid of virtually any size, as long as the incoming space rock is spotted with enough lead time, experts say.

Our species could even nudge off course a 6-mile-wide (10 kilometers) behemoth like the one that dispatched the dinosaurs 65 million years ago. We'd likely have to slam multiple spacecraft into a gigantic asteroid over a period of several decades to do the job, but the high stakes would motivate such a strong and sustained response, researchers say.

"If you can hit it with a kinetic impactor, you can hit it with 10 or 100 of them," former NASA astronaut Ed Lu, chairman and CEO of the nonprofit B612 Foundation, which is devoted to protecting Earth against asteroid strikes, said during a news conference last month.

"And I would submit to you that if we were finding an asteroid that's going to wipe out all life on Earth, or the majority of life on Earth, that funding is not an issue for launching 100 of them," Lu added.

Undiscovered asteroids

Lu and four other spaceflyers spoke Oct. 25 at the American Museum of Natural History in New York City. A primary purpose of the event was to draw attention to the danger asteroids pose to human civilization and life on Earth, and to discuss ways to mitigate the threat.

Earth has been pummeled by space rocks repeatedly over the eons and will continue to get hit, a reality that was reinforced in February when a 55-foot-wide (17 meters) space rock exploded in the atmosphere over the Russian city of Chelyabinsk, injuring more than 1,000 people.

The Russian meteor came out of nowhere, evading detection by the various instruments that are scanning the heavens for potentially hazardous objects. And there are many more such space rocks out there, gliding through deep space unknown and unnamed. 

To date, scientists have discovered about 10,000 near-Earth objects, or NEOs — just 1 percent of the 1 million or so asteroids thought to come uncomfortably close to our planet at some point in their orbits. So the top priority of any asteroid-defense effort should be a stepped-up detection campaign, Lu said.

"Our challenge is to find these asteroids first, before they find us," he said. "You cannot deflect an asteroid you haven't yet found."

To make progress on the detection front, the B612 Foundation is developing a privately funded infrared space telescope called Sentinel, which will search for asteroids from a Venus-like orbit. The group aims to launch Sentinel in 2018 and says it will likely find 500,000 NEOs in less than six years of operation.

Deflecting dangerous space rocks

Scientists hope Sentinel and other asteroid-hunting instruments will spot dangerous NEOs several decades before they could potentially slam into Earth.

That's enough lead time to mount a successful deflection effort, which would likely involve launching two separate space missions, former Apollo astronaut and B612 co-founder and chairman emeritus Rusty Schweickart told SPACE.com earlier this year.

The first mission, he said, would send a robotic probe on a collision course with the asteroid, knocking it off course via kinetic impact. The second would follow up, launching a "gravity tractor" spacecraft to fly along with the space rock, nudging it further via a tiny but consistent gravitational tug.

Such a strategy would probably work on asteroids up to 1,300 feet (400 m) wide, Schweickart said at the Oct. 25 press conference. Anything bigger than that likely demands a different response, he added, such as a series of kinetic impacts or blasting the asteroid with a nuclear bomb.

Infrequent events

Colossal asteroid impacts that cause mass extinctions are extremely rare events. For example, strikes like the one that killed off the dinosaurs (and roughly 80 percent of all Earth's species) 65 million years ago happen roughly once every 100 million years, Schweickart said.

But smaller (and much more frequent) strikes can still be devastating. In 1908, an object thought to be just 130 feet (40 m) wide, or perhaps even smaller, exploded above the Podkamennaya Tunguska River in Siberia, flattening roughly 770 square miles (2,000 square km) of forest.

Impacts like the "Tunguska Event" — which would have destroyed New York City, Tokyo or any other metropolis if they had been in the asteroid's crosshairs — occur once every 300 years on average, Schweickart said.

So it makes sense to focus on city-killers and other relatively small asteroids rather than the behemoths when thinking about how to deflect space rocks — especially since the true giants are so easy to spot.

"We're not going to be surprised by something that large," Schweickart said of asteroids like the dinosaur-killer. "We will have lots of time to worry about it, or mix our martinis, or whatever we're going to do."

Source of Article: Space.com

How to Photograph Comet ISON: A Skywatching Photo Guide

The incoming Comet ISON is undergoing dramatic brightening as it heads toward its Thanksgiving Day rendezvous with the sun, but if you are hoping to snap photos of the icy wanderer, you'll need to be prepared.
Officially known as C/2012 S1 (ISON), Comet ISON was discovered in September 2012 and has been billed by some as a potential "comet of the century" because of its potential to flare up into a brilliant night sky object. It is already visible to the naked eye for observers in dark-sky sites and is now sporting a long tail.

If this icy cosmic visitor survives its fiery solar encounter on Thursday (Nov. 28), when it swings within 730,000 miles (1.2 million kilometers) of the sun's surface, it could reappear in the dawn sky in early December as a potentially spectacular naked-eye object for skywatchers in the Northern Hemisphere.

But comets are notorious for their unpredictability, as shown by Comet Kohoutek C/1973 E1 in the early 1970s, which failed to meet predictions. As our good friend and famed comet discoverer David H. Levy likes to say, "Comets are like cats; they have tails, and they do precisely what they want."
This uncertainty, however, has failed to dampen the interest and excitement of the public and the media in Comet ISON. So if you want to capture your own souvenir portrait of this first-time visitor to our solar system, here are some tips to keep in mind to increase your chances of success:
  • Look for a site away from city lights that offers a clear, unobstructed view of the southeastern horizon about an hour or so before sunrise. With each passing day, the comet will plunge deeper and deeper into the brightening dawn sky as it makes its closest approach to the sun, called "perihelion," on Nov. 28. After it emerges from perihelion, the comet will climb higher and higher in the dawn sky, but at the same it will start to fade as it recedes from the sun and Earth.
WARNING:Do not attempt to observe or photograph Comet ISON when it is very close to the sun or is at perihelion. Staring directly at the sun, especially through a camera, telescope or binoculars without a proper, safe filter can result in serious eye injury or permanent blindness. No comet is worth losing your eyesight, so please be very careful!

Use a digital single-lens reflex DSLR camera to photograph the comet since it gives you more control on your focus and exposure settings. It also allows you to change lenses, from wide-angle to medium telephoto, to match the length of the comet’s tail.

  • Since the comet would require exposures lasting a few seconds or more, you would need a sturdy tripod or mount to steady your camera setup.
  • Switch your camera mode from Auto (A) to Manual (M) so you’ll be able to control its focus as well as lens aperture, shutter speed and white-balance settings. Set the camera to its highest resolution (RAW mode) so you can capture as much fine details and color information as possible. Consult your camera manual on how to change settings.
  • Comets are inherently fuzzy objects so don’t rely on them for focusing your camera. To ensure sharp images, pre-focus the camera on Mars, Mercury or Saturn, or the bright star Spica. Use your camera's Live View feature, if it has one, to achieve accurate focus.
  • You can minimize vibrations that can blur your images by using your camera’s mirror lock-up feature before each shot. You should also operate the shutter with an electronic cable release to eliminate camera shake.
  • Boost your camera’s sensitivity to ISO 800, or higher. You would want to keep your exposures relatively short, especially if you are using your DSLR on a plain, fixed tripod. This will not only prevent the images of the comet and background stars from trailing due to Earth’s rotation, but it will also keep the brightening dawn sky from washing out the scene.
  • Don’t forget to "bracket" your exposures — that is, take a series of shots of the comet at various shutter speeds and/or apertures. This will increase your chances of getting the correct exposure.
  • Make sure your camera battery is fully charged, and put your spare battery in your jacket's inside pocket to keep it warm — cold temperatures at dawn can cause your battery to quickly lose its charge.
  • When composing your shot, try to include some interesting visual elements in your foreground, such as a person, a tree or a monument silhouetted against the horizon.
If you want to capture detailed shots of the comet and record the full extent of its tail, you will need to use a more elaborate tracking system than the simple camera-on-tripod setup we just described, and may need binoculars or a telescope:
  • Use a zoom or telephoto lens with a focal length of 400 millimeters or more to give you a fairly large image of the comet and its tail in the camera frame.
  • The long-focus lens will magnify the comet's movement in the sky so you will have to mount your setup on a polar-aligned, motor-driven equatorial mount. The motor drive will “track” the comet and keep it centered in your camera’s field, allowing you to take exposures lasting several minutes.
  • Alternatively, you can use a ball-head mount or a bracket to mount your camera/lens setup securely to a hefty telescope on a heavy-duty mount. In this "piggyback" mode, the telescope serves as a stable tracking platform for the camera.
  • Use the camera’s Bulb (B) setting to take exposures longer than 30 seconds.
  • Depending on your sky brightness, you can shoot a single long exposure or take a series of short exposures that you can later “stack” together digitally using an image-editing program, such as Adobe Photoshop, to create effectively one long exposure.
  • For really close-up views of the comet’s head and tail structure, you need to shoot through a long-focus telescope on an equatorial drive. Attach the DSLR camera body securely to the telescope using a T-threaded adapter and a T-ring that is appropriate for your camera brand. Check your local camera supply store for these handy accessories.
  • At such high magnification, any inaccuracies in the telescope’s drive system or polar alignment will be evident. That is why deep-sky astrophotographers use an "autoguider," an automated electronic guiding system that attaches to the telescope’s off-axis guider or guidescope. The autoguider can "lock" onto the comet’s head or selected guide star, and it will make automatic adjustments to the telescope’s drive system continuously throughout the exposure to ensure accurate tracking.
Assuming Comet ISON doesn't disintegrate before reaching the sun, the comet will continue on its outbound journey into deep space, never to return again for a long, long time. So don't miss this once-in-a-lifetime opportunity to catch Comet ISON now.

Source of Article: Space.com

New US Space Transportation Policy Stresses Private Spacecraft, Heavy-Lift Rocket

The Obama administration has outlined its strategy for maintaining what it describes as the United States' global leadership role in spaceflight and exploration.

The White House's new national space transportation policy, released Thursday (Nov. 21), reinforces several previously stated administration priorities. It calls on federal agencies to continue supporting the development of private American spaceships to carry astronauts to and from low-Earth orbit, for example, and directs NASA to keep working on a heavy-lift rocket to send people much farther afield.

This plan makes a lot of sense for NASA, allowing the agency to put its limited financial resources to the best possible use, NASA chief Charles Bolden said.

"The development of a commercial space sector for low-Earth orbit transportation is freeing NASA to develop a heavy-lift launch capability to travel further into space than ever before," Bolden wrote in a blog post about the new policy Thursday.

"NASA has already made steady progress on the development of the next-generation heavy-lift launch vehicle, the Space Launch System (SLS)," he added. "NASA is also well on its way to developing the Orion crew capsule, which will take astronauts further into deep space than humans have ever explored."

The maiden Orion test flight is slated for next year, while the SLS is scheduled to get off the ground for the first time in late 2017. NASA wants the duo to be flying astronauts together by 2021.

That would allow the space agency to meet two objectives President Barack Obama laid out for NASA in his 2010 National Space Policy — to get astronauts to a near-Earth asteroid by 2025, then on to the vicinity of Mars by the mid-2030s.

While it works on this deep-space transportation system, NASA is also encouraging the growth of an emerging private spaceflight industry. Through its commercial crew program, the agency has most recently funded the development of three private manned spaceships — those being built by SpaceX, Boeing and Sierra Nevada Corp. — and hopes at least one of them is up and running by 2017.

Leaders in the commercial spaceflight industry were pleased to see continued support for this effort in the new policy.

"We appreciate this clear delineation of policy in favor of supporting American industry, creating the most effective and efficient space program possible and ensuring the nation retains its leadership and competitiveness in space," Michael Lopez-Alegria, president of Commercial Spaceflight Federation and a former NASA astronaut, said in a statement. "We are grateful for the Obama Administration’s support for the commercial space sector and look forward to many joint successes to come."

The newly released space transportation policy, which replaces a version announced in 2004, is a wide-ranging document touching on many different aspects of American space infrastructure.

Source of Article: Space.com

2013년 11월 16일 토요일

Stephen Hawking Says Not Finding Higgs Boson Would Be 'More Interesting'

The discovery of the once-elusive Higgs boson particle after a decades-long hunt is widely regarded as a major breakthrough, but legendary physicist Stephen Hawking thinks the field would actually be more "interesting" if the Higgs had remained a mystery.

"Physics would be far more interesting if it had not been found," Hawking told an audience at the Science Museum in London this week, according to The Guardian.

The Higgs boson is an elementary particle that is thought to explain why other fundamental particles have mass. Its discovery in July 2012, at the Large Hadron Collider housed at CERN's physics lab in Geneva, Switzerland, represented the final piece of the puzzle predicted by the Standard Model, the reigning theory of particle physics. 

Last month, the Royal Swedish Academy of Sciences awarded the Nobel Prize in physics to Francois Englert of Belgium and Peter Higgs of the United Kingdom, for their research in 1964 on the theory of particle masses, which established the foundation for the discovery of the Higgs particle.

But, had the Higgs not been found, physicists might have been required to rethink some of the prevailing ideas about the nature of particles, launching investigations into other "interesting" and tantalizingly unanswered questions, Hawking suggested.
Still, the search for the Higgs boson, and its subsequent discovery, received widespread attention, including early debates about whether the long-sought particle had actually been detected or not.
Hawking's initial doubts about the discovery ended up costing him. "I had a bet with Gordon Kane of Michigan University that the Higgs particle wouldn’t be found," Hawking said, as reported by The Guardian. "The Nobel prize cost me $100."
Hawking spoke at an event earlier this week to celebrate the opening of a new exhibit about the Large Hadron Collider, the world's largest atom smasher, at the Science Museum in London.
In addition to talking about the discovery of the Higgs particle, Hawking discussed some of the other theories he hopes will be probed by scientists at CERN.

One is supersymmetry, a popular theory based on the idea that all of the known subatomic particles have "superpartner" particles that have yet to be observed. If these superpartners do exist, scientists could begin to explain some of the most enigmatic riddles in physics, such as the nature of dark matter, which is an invisible substance thought to make up a quarter of the universe. Scientists think dark matter may be composed of as-yet-undetected supersymmetric particles.

"I think the discovery of supersymmetric partners for the known particles would revolutionize our understanding of the universe," Hawking said.

Source of Article: Space.com

NASA's MAVEN Mission to Mars: 5 Things to Know

NASA is all set to launch its next mission to Mars on Monday (Nov. 18), provided the weather cooperates and no unexpected glitches pop up.

The Mars Atmosphere and Volatile EvolutioN orbiter, or MAVEN for short, is slated to blast off atop an Atlas 5 rocket at 1:28 p.m. EST (1828 GMT) Monday from Florida's Cape Canaveral Air Force Station. You can watch MAVEN's launch on SPACE.com, courtesy of NASA TV.

As its name suggests, MAVEN will make detailed measurements of the Red Planet's atmosphere from orbit, helping scientists understand why and how Mars' climate has changed so dramatically over the last few billion years. It will take about 10 months to reach Mars, and arrive at the Red Planet in September 2014.

Here are some key facts to keep in mind about the MAVEN probe and its $671 million mission:

MAVEN is big

The solar-powered MAVEN spacecraft is pretty hefty. While the probe's body is a cube measuring 8 feet (2.4 meters) on a side, MAVEN spans a total of 37.5 feet (11.4 meters) with its solar panels deployed, making the craft as long as a school bus.
And MAVEN weighs 5,410 pounds (2,454 kilograms) — as much as a fully loaded sport utility vehicle.

Elliptical orbit

When MAVEN gets to Mars, the probe will insert into an elliptical orbit around the planet that brings it as close as 93 miles (150 kilometers) and reaches as far away as 3,728 miles (6,000 km).

In addition, MAVEN will make a handful of "deep dips" during the course of its mission, coming within 77 miles (124 km) of the Martian surface on five separate occasions. MAVEN will thus be able to sample the Red Planet's upper atmosphere directly and get a wider view of the entire planet from afar — a powerful combination, NASA officials say.

Solving a Martian mystery

Mars was a potentially habitable planet billions of years ago, with a thick atmosphere and large amounts of liquid water flowing across its surface. But then something happened, and the Red Planet transitioned to the cold and dry world we know today, with an atmosphere just 1 percent as dense as that of Earth.

Scientists hope MAVEN helps them get a better handle on this dramatic shift. The mission aims to determine how and why much of the Martian atmosphere was lost to space, and what role this loss played in Red Planet climate change over the last four billion years.
MAVEN will use eight different science instruments to study Mars' upper atmosphere and the solar wind, the stream of charged particles flowing from the sun that is thought to have stripped away much of the water and other volatile compounds in the Red Planet's air.

Not a Mars life hunt

While MAVEN's observations should help researchers better understand Mars' past and present habitability, the mission will not actively search for signs of life.
In fact, MAVEN is not equipped to sniff for methane, a gas that could be an indicator of extant life. (About 90 percent of Earth's methane is produced by living organisms.) MAVEN's budget could not support adding a methane-detection component, mission scientists have said.

Communications link

While NASA is most excited about the data MAVEN will gather, the spacecraft will also serve the space agency in another way — as a communications relay beween rovers on Mars and their handlers on Earth.

NASA currently has two rovers exploring the Red Planet's surface — the car-size Curiosity, which touched own in August 2012, and its smaller cousin Opportunity, which landed in January 2004. MAVEN will augment data relay from the two robots, which is currently provided by two NASA orbiters — Mars Odyssey, which launched in 2001, and the Mars Reconnaissance Orbiter (MRO), which blasted off in 2005.

This relay capability helped the MAVEN mission stay on track despite last month's government shutdown, which forced NASA to furlough 97 percent of its employees and cease most operations. While MAVEN launch preparations were halted at the beginning of the 17-day shutdown, the space agency granted the mission an emergency exception two days later, chiefly because of its importance as a communications link. (The agency has no relay orbiters on the books beyond MAVEN.)

Source of Article: Space.com

2013년 11월 11일 월요일

Incredible Technology: How Future Space Missions May Hunt for Alien Planets

NASA's Kepler space telescope revolutionized the study of alien worlds after launching in 2009, and a number of other missions now stand poised to carry the burgeoning field into the future.

Over the next decade, NASA and the European Space Agency (ESA) aim to launch a handful of spacecraft that should discover thousands of additional exoplanets and characterize some of the most promising — the most apparently Earthlike — new finds in detail.

These future missions are all following in the footsteps of Kepler, whose observations have revealed that the Milky Way galaxy is jam-packed with alien planets. The instrument has spotted more than 3,500 planet candidates to date; just 167 of them have been confirmed by follow-up observations so far, but mission scientists expect about 90 percent will end up being the real deal.

Kepler's original planet-hunting activities came to an end this past May when the second of its four orientation-maintaining reaction wheels failed, robbing the spacecraft of its ultra-precise pointing ability. But the instrument may continue its planet search in a modified and limited fashion, as part of a possible future mission dubbed K2.

NASA is expected to make a final decision about K2, and Kepler's ultimate fate, around the middle of next year. By then, the first member of the exoplanet new wave will already be aloft — Europe's Gaia mission.

Gaia: The billion-star surveyor

ESA's Gaia spacecraft is slated to blast off from French Guiana next month; its launch window extends from Dec. 17 through Jan. 5.

Gaia will head to a gravitationally stable spot about 900,000 miles (1.5 million kilometers) from Earth called the sun-Earth Lagrange Point 2. Over the next five years, the spacecraft will repeatedly measure the position, movement and brightness changes of more than 1 billion Milky Way stars — about 1 percent of the galaxy's total.

"This huge stellar census will provide the data needed to tackle an enormous range of important problems related to the origin, structure and evolutionary history of our galaxy," ESA officials write in a description of the Gaia mission.

Exoplanet science should be one of the fields that benefits. The Gaia mission, whose total cost is 740 million euros (about $990 million), could potentially detect tens of thousands of new planetary systems, researchers say.

Cheops: A follow-up machine

ESA will likely launch another exoplanet mission, called Cheops (short for CHaracterizing ExOPlanets Satellite), four years after Gaia gets off the ground.

Like Kepler, Cheops will watch for exoplanet "transits," gathering data when alien worlds cross the face of their parent stars from the instrument's perspective. But the similarities mostly end there. While Kepler stared at more than 150,000 stars simultaneously, Cheops will target one star at a time. And its chief aim is the follow-up study of known exoplanets, rather than the discovery of previously unknown worlds.

"Knowing when to look, and at which star, will make Cheops extremely efficient at providing first-step characterization of low-mass exoplanets by measuring accurate radii and densities," David Ehrenreich, of the University of Geneva, said Nov. 6 during a presentation at the second Kepler Science Conference at NASA's Ames Research Center in Moffett Field, Calif.

Another key goal of Cheops, Ehrenreich added, is "collecting the 'golden targets' for future in-depth characterization by, for instance, the James Webb Space Telescope."  
Cheops' total cost is about $134 million (100 milllion Euros), Ehrenreich said. Formal adoption of the mission is expected in the next few months, with launch targeted for late 2017.

The Transiting Exoplanet Survey Satellite

NASA is developing its own mission for launch in 2017. The agency'sTransiting Exoplanet Survey Satellite, or TESS, aims to look for planets crossing the face of about 500,000 stars during its planned two-year operational life.

While Kepler scanned stars 1,000 or so light-years away, the $200 million TESS mission will look much closer to home. It will focus on stars within 100 light-years of Earth, with the goal of finding planets that will be easier to study and characterize with future instruments such as NASA's James Webb Space Telescope (JWST).

And TESS should discover plenty of new worlds. Team members expect to find about 315 the size of Earth or a little larger, 710 planets a bit smaller than Neptune, 1000 Neptune-like worlds and 660 Jupiter analogs, mission principal investigator George Ricker of MIT said Nov. 6 at the Kepler Science Conference.

"It's really a bridge to the future," Ricker said of TESS. "We're really, obviously, following on from Kepler. And because of the way in which there's a focus on providing targets that are going to be optimal in place for the continuous viewing zone for JWST, there's clearly going to be a linkage between providing information that'll be useful to that mission."

Hubble's long-awaited successor: JWST

Researchers have high hopes for JWST, the $8.8 billion infrared-optimized telescope that NASA hopes to launch toward the end of 2018.

Scientists plan to point JWST at the most promising and intriguing exoplanets that have been discovered in Earth's cosmic neck of the woods, using the powerful instrument to scan these worlds' atmospheres for water vapor and gases that may have been produced by living organisms, such as oxygen, nitrous oxide and methane. 

JWST should also make contributions in many other arenas, NASA officials say, shedding light on the early history of the universe and improving researchers' understanding of the formation and evolution of stars, galaxies and planetary systems.


The outlook for space-based exoplanet science gets a little cloudy beyond JWST, but both NASA and ESA have some potential projects in the works.

NASA, for example, is working on a $1.6 billion observatory called the Wide-Field Infrared Survey Telescope. In 2010, the U.S. National Research Council deemed WFIRST the top priority for the next decade of astronomical research.

The current mission design, called WFIRST-AFTA (short for Astrophysics Focused Telescope Assets), calls for the observatory to incorporate one of two spy-satellite telescopes given to NASA by the U.S. National Reconnaissance Office in 2011.

The donated scopes are similar in size and appearance to NASA's iconic Hubble Space Telescope, sporting 8-foot-wide (2.4 meters) primary mirrors. The instruments are far from flight-ready spacecraft, however; they're basically just primary and secondary mirrors with associated support structures.

WFIRST-AFTA would probe the nature of mysterious dark energy and hunt for and study alien planets using two techniques: direct imaging and gravitational microlensing. In this latter method, astronomers watch what happens when a massive object passes in front of a star; the closer object's gravitational field bends and magnifies the star's light, acting like a lens.

The mission could find thousands of exoplanets using microlensing alone, said Matthew Penny of Ohio State University. Current plans call for WFIRST-AFTA to launch in 2023 or thereabouts, but the proposed mission remains in a sort of limbo at the moment, he added.
"There's going to be no funding for [other] large missions until JWST is launched," he said Nov. 6 at the Kepler Science Conference. "After that, NASA will have to ask Congress, I think, to fund the next large mission."


ESA may launch its own large-scale exoplanet mission at about the same time WFIRST-AFTA gets off the ground. The Europeans are developing a project called Plato (PLAnetary Transits and Oscillations of stars), with a possible liftoff in the 2022-2024 timeframe.

Like Kepler, Cheops and TESS, Plato will use the transit technique. The mission's main goal is to find and characterize large numbers of nearby planetary systems, getting accurate sizes and masses of alien worlds — many of which may lie in their host star's habitable zone, that just-right range of distances where liquid water can exist on a planet's surface.
"We want to completely characterize low-mass planets out to the habitable zone, being able to know about the internal composition, the density, the age of the system," Stephane Udry of the University of Geneva said Nov. 6 at the Kepler Science Conference.

Plato is one of five proposed "medium-class" missions — whose cost to ESA is capped at 470 million euros, or about $630 million — the agency is considering for the 2022-2024 launch slot. ESA will select one of these five in February 2014, officials have said.

Source of Article: Space.com