The Hunt for Elusive Gravity Waves Heats Up

In the next five years or so, scientists are poised to discover proof that space and time can wrinkle in the form of gravitational waves. These waves were predicted almost 100 years ago by Albert Einstein's general theory of relativity, but have yet to be seen.

That could change soon when the latest, most sensitive experiments hunting gravitational waves come online. "There's so much activity and excitement in the field right now," said Mansi M. Kasliwal, an astronomer at the Observatories of the Carnegie Institution for Science in Pasadena, Calif. "The momentum is really building."

Kasliwal is the author of a paper published online today (May 2) in the journal Science describing the burgeoning field of gravitational wave studies. 

According to general relativity, massive objects warp space and time around them, like a bowling ball dropped onto a sheet of rubber, causing passing objects, and even light, to travel along curved paths. When two extremely dense objects, such as neutron stars (stars so dense the protons and electrons in their atoms collapse to form neutrons) or black holes, orbit each other in binary pairs, their interactions should create ripples in the fabric of space-time called gravitational waves. The most powerful waves would arise when two neutron stars or black holes merge together.

Those waves should be detectable by experiments called Advanced LIGO (Laser Interferometer Gravitational Wave Observatory) and Advanced Virgo, set to come online in 2017. They will each use giant L-shape detectors in Louisiana, Washington and Italy to search for minute changes in the lengths of the detectors' arms caused when gravity waves pass through. At the corner of the "L," a laser is split into two beams that travel back and forth down the length of the two arms (each between 1.2 miles, or 2 kilometers, and 2.5 miles, or 4 kilometers, long), bouncing off mirrors at each end. If a gravitational wave passed through, it would stretch and compress these lengths, depending on its orientation, creating a small but detectable difference in the length of the two arms.

Initial versions of LIGO and Virgo are already operating, but aren't yet sensitive enough to detect gravitational waves. When they are upgraded to higher sensitivities, though, they should reveal hidden gravitational waves for the first time. These observations wouldn't just prove the existence of gravitational waves, they would offer unprecedented information about the rare and extreme cosmic phenomena that create them.

"I think the confidence level is quite high" that the advanced experiments will see gravitational waves, Kasliwal told SPACE.com. "The sensitivity is now such that if Einstein's general relativity is right, then we should see these things." She estimated that the experiments are likely to detect between four and 400 gravitational waves a year. "But zero would be quite a disaster. We'd need to rethink our understanding of gravity."

When a gravitational wave is spotted, it will likely trigger a global collaboration to attempt to find the source of the wave in the sky. By comparing the signals seen at the various detectors around the world, scientists can get a better idea of which direction the wave came from. Then they can point telescopes toward that spot and search for light that flared at the same time, potentially finding more clues about what happens when black holes collide.

"If you see spatial coincidence and temporal coincidence, this is something truly new that we haven’t seen before," Kasliwal said.

Source of Article : space.com

Why Is Our Solar System Such a Cosmic Weirdo?

The solar system that humans call home may be a strange oddity when compared with the incredible diversity of planetary systems researchers are discovering in the Milky Way, astronomers say.

Scientists now estimate the Milky Way galaxy contains at least as many planets as it does stars. So far, researchers have detected nearly 900 of these so-called exoplanets already, and several thousand more candidates are under investigation.

The number of distant worlds that astronomers have discovered in the past 15 years or so has skyrocketed recently due to new advances such as NASA's Kepler mission, which can detect planets as small as Earth's moon. Analyzing the orbits, masses, diameters and compositions of these exoplanets has revealed that an extraordinary variety of them exist, such as so-called "hot Jupiters," gas giants orbiting closer to their stars than Mercury does the sun.

Super-Earths

In the last five years, researchers have unexpectedly discovered the most common type of exoplanet seen to date is one missing from the solar system — a world between the sizes of Earth and Neptune. Planets like these apparently substantially outnumber larger, Jupiter-size planets, at least relatively close to their stars.

"These are sometimes called 'super-Earths,'" study author Andrew Howard, an astronomer at the University of Hawaii at Manoa, told SPACE.com.

Super-Earths are part of the most commonly seen class of exoplanetary systems. These involve one or more planets between one to three times the size of Earth orbiting much closer to their stars than one astronomical unit, the distance from Earth to the sun.

The composition of the exoplanetary systems that researchers have observed so far may solve a key mystery regarding which of two competing models of how planets form is correct. The core accretion model of planetary formation suggests worlds grow when gas accumulates relatively quickly onto a solid planetary core, while the mechanism known as gravitational instability has a planet's interior and atmosphere born simultaneously.

The core accretion model predicts that giant planets should be more common around massive stars that are rich in "metals" — that is, elements heavier than helium — since these stars have discs surrounding them dense in the dust and ice that could go into a planet's core. So far, it looks as if metal-rich stars are in fact more likely to host giant planets within five astronomical units of them, suggesting the core accretion model is how planets are generally created.

Exoplanet mysteries

Still, other mysteries abound when it comes to exoplanets. For instance, much remains unknown about super-Earths.

"What are the compositions of these super-Earths?" Howard asked. "Are they really scaled-up rocky, Earth-like planets? Are they water worlds with cometlike compositions? Are they scaled-down Neptune-like planets with rock, water and atmospheres of hydrogen and helium?

In addition, the origins of super-Earths are a puzzle. "Did they form in place?" Howard asked. "Did they form in more distant orbits and migrate inward to close orbits?"

All in all, a great deal is uncertain about what exoplanets are like because the current techniques for detecting large numbers of exoplanets see only certain kinds of alien worlds — planets Earth-size or larger orbiting less than one astronomical unit from their stars, and gas giants orbiting within several astronomical units.

"We only have a soda straw view of exoplanets," Howard said. "Smaller planets or planets orbiting more distantly are very hard to detect."

Habitable planets

A major goal now of exoplanet research is to detect Earth-size worlds orbiting in their stars' habitable zones, where temperatures are just right for oceans of liquid water to survive on the surfaces of those planets. These exoplanets might be home to life as we know it, since there is life virtually wherever there is water on Earth.

"Kepler will keep pushing toward smaller planets in more distant orbits," Howard said. "Assuming the satellite keeps working, it will likely discover the first Earth-size planet in the habitable zone. A few years later, we'll have several of these planets and then we can start to calculate how common they are."

Still, Howard cautioned that habitable zones remain difficult to define, since more than just a planet's distance from its star underlies whether or not it might have water on its surface — for instance, the nature of its atmosphere is another key factor as to whether it retains just the right amount of heat to keep surface oceans stable.

"And the habitable zone doesn't mean it's inhabited," Howard said. "It just means that the temperature is right for liquid water if water exists at all on that planet."

Source of Article : space.com

'Adopt-an-Alien Planet' Campaign Launches Today

A new campaign aims to start giving popular names to the hundreds of alien planets that have been discovered around the Milky Way galaxy.

The space-funding company Uwingu announced this "Adopt-a-Planet" effort today (May 1), asking the public to propose and vote on names for the many and varied worlds now known beyond our solar system.

Any moniker that receives at least 1,000 votes earns its nominator the chance to "adopt" (and name) the exoplanet of his or her choice. Such winners will also receive an adoption certificate, links to detailed information about the adopted planet and $100 in Uwingu store credits, company officials said.

Adopt-a-Planet is similar to a month-long contest Uwingu staged recently to give a people's-choice name to Alpha Centauri Bb, the closest known exoplanet to Earth at just 4.3 light-years away.

The new adoption effort, however, is open-ended and seeks names for many different alien worlds.

"We're happy to have winner after winner after winner," Uwingu CEO Alan Stern, a former NASA science chief who also heads the agency's New Horizons mission to Pluto, told SPACE.com. "There are plenty of exoplanets out there."

Nominating a name costs $4.99, and voting will set you back 99 cents. Uwingu (whose name means "sky" in Swahili) will use the money raised by Adopt-a-Planet to fund grants in space exploration, research and education, which is the company's main purpose, Stern added.

Uwingu also sees the campaign as a fun way to get people more interested and involved in science.

"We're engaging the public with the sky and astronomy in a way that's never been possible before," Stern said.

The names people propose for Adopt-a-Planet won't become the alien worlds' "official" astronomical names, Uwingu officials say. Rather, they'll be common monikers, much like "The Milky Way" or "The Whirlpool Galaxy."

The International Astronomical Union has traditionally approved official names for celestial bodies. So far, the organization has not moved to change the planet-naming status quo, in which alien worlds take the name of their host star along with a lowercase letter. The first planet discovered in a particular system is designated "b" (since the star is implicitly "a"), the second "c" and so on.

Astronomers first confirmed an alien planet orbiting a sunlike star in 1995. Since then, they've discovered more than 700 exoplanets (or more than 800, depending on whose tally is consulted), with thousands more awaiting confirmation by follow-up observations.

Source of Article : space.com

Quantum Mechanics Trick May Detect Invisible Gravity Waves

The existence of gravitational waves, or ripples in space and time, has long been predicted, but the elusive phenomenon has eluded scientists for decades. Now researchers are proposing a new method to detect these cosmic wrinkles that relies on the quantum nature of atoms.

Gravitational waves are a consequence of Einstein's general theory of relativity, which posits that massive objects warp the space-time around them, causing other objects, and even light, to travel along curved paths when they pass nearby. Objects with very strong gravitational fields, such as black holes or dense stars orbiting in binary pairs, should create gravitational waves so powerful they are detectable here on Earth.

However, no experiment has yet found definitive proof that gravity waves exist. A group of physicists led by Stanford University's Peter Graham hopes to change that, though, with a new detection method they call "atom interferometry." 

"No one's yet seen a gravitational wave, but that's not the reason most of us are really excited about it," Graham told SPACE.com. "We're all basically certain gravitational waves are there. But you could build a gravitational wave telescope and use gravitational waves to look at the whole universe."

By studying the information embedded in these space-time wrinkles, he explained, scientists could learn about the objects that made them, and probe exotic phenomena such as black holes, neutron stars and other dense objects. They could also explore the mysteries of gravity, which is still not well understood.  "You might learn something about gravity in what's called the 'strong field regime,' where gravity is far beyond the strength of anything we can make in the lab," Graham said.

Gravity wave detectors

Current experiments hunting gravity waves look for distortions to the lengths of long walls caused when space-time ripples pass through them. The most sensitive gravity wave detector is LIGO (the Laser Interferometer Gravitational Wave Observatory), which comprises three detectors in Louisiana and Washington. Each has two arms, between 1.2 miles (2 kilometers) and 2.5 miles (4 kilometers) long, that are perpendicular to each other.

If a gravitational wave passed through, it should stretch one arm, while shortening the other, depending on its orientation. Using sensitive lasers whose light is split — one beam down one arm, another down the other — LIGO is equipped to detect minute changes to the length of its walls. However, this detection method, called laser interferometry, is very susceptible to laser noise, or random fluctuations in laser light, that could simulate the effects of gravity waves.

To get around the problem of laser noise, Graham and his colleagues want to use atoms instead of lasers. Instead of splitting a laser beam in two, the scientists plan to essentially split an atom — a prospect made possible by quantum mechanics. According to this theory, particles are less like tiny marbles and more like hazy clouds of probability described by equations called wave functions. They don't definitively exist in a certain place at a certain time unless pinned down by direct measurements.

Splitting the atom

For atom interferometry, the wave function of an atom is split. "The atom is in a weird quantum mechanical combination of here and there," Graham said. "If a gravity wave flies through this interferometer, then the two halves of the atom will accelerate with respect to each other because of this gravity wave."

To measure this acceleration, the experiment would use lasers, potentially introducing the laser noise problem all over again. To avoid this difficulty, the researchers want to launch two atom interferometers on two satellites that would orbit a set distance apart. "If you shine the same laser beam simultaneously on the two atom interferometers, then you get the same noise read into both of the atoms, but the gravitational wave signal is not the same at the two spots, so that's the key," Graham said, adding that the laser noise can be compared and subtracted out of the signal.

The experiment works best on spacecraft, rather than on the ground, because the normal vibrations and shaking of the Earth could contaminate measurements made in ground-based detectors.

The researchers estimate such a mission would cost between $100 million and $1 billion — not a bargain, though significantly cheaper than proposed space-based laser interferometers, which would require three satellites, not two. A planned joint U.S.-European gravity wave-hunting laser interferometer space mission called LISA (the Laser Interferometer Space Antenna) was canceled in 2011 due to lack of funding.

Source of Article : space.com

Europe Gets Serious About Space Junk Menace

Hundreds of scientists, engineers and space-law experts are gathering this week to discuss the growing problem of space debris, and will propose ways to curb the accumulation of new junk in orbit.

The 6th European Conference on Space Debris is being held April 22-25 at the European Space Operations Center in Darmstadt, Germany. More than 300 representatives, ranging from researchers to policymakers, are expected to attend the four-day event, according to officials at the European Space Agency (ESA).

Conference attendees will discuss the buildup of potentially harmful debris in orbit, and address possible ways to remove defunct satellites and other pieces of errant space hardware.

More than 170 million pieces of space junk are currently orbiting Earth, including 29,000 objects that are larger than 4 inches (10 centimeters), according to ESA estimates. As they speed through space at 17,000 mph (27,000 km/h), these objects pose collision risks to both other satellites in orbit and the International Space Station.

"Any of these objects can harm an operational spacecraft," Heiner Klinkrad, head of ESA's Space Debris Office, said in a statement.

Roughly two-thirds of the known pieces of debris were created by explosions in orbit or collisions, ESA officials said.

In 2009, a U.S. Iridium communications satellite was struck by a defunct Russian Cosmos military satellite in what became a wake-up call for the industry. The crash destroyed the two spacecraft and left a huge cloud of debris.

Then, in 2007, China intentionally destroyed one of its aging weather satellites in a controversial anti-satellite test that littered Earth’s orbit with more than 2,500 scraps of space junk.

Since then, researchers and satellite operators have tried to tackle the issue of sustainability in space.

"Space-debris mitigation measures, if properly implemented by satellite designers and mission operators, can curtail the growth rate of the debris population," Klinkrad said. "Active debris removal, however, has been shown to be necessary to reverse the debris increase."

But finding any solution to the space-debris problem will require a collaborative approach.

"As this is a global task, active removal is a challenge that should be undertaken by joint efforts in cooperation with the world's space agencies and industry," Thomas Reiter, ESA's director of human spaceflight and operations, said in a statement.

Source of Article : space.com

Hubble Telescope Photographs Potential 'Comet of the Century'

NASA's iconic Hubble Space Telescope has snapped stunning new photos of Comet ISON, which could become one of the brightest comets ever seen when it zips through the inner solar system this fall.

Hubble captured the new photos on April 10, when Comet ISON was slightly closer than Jupiter. At the time the icy wanderer was about 386 million miles (621 million kilometers) from the sun and 394 million miles (634 million km) from Earth.

The new images are already helping astronomers take a bead on the mysterious Comet ISON, which may shine as brightly as the full moon when it makes its closest pass by the sun in late November. (The comet poses no threat to Earth, NASA has said.) 

For example, the Hubble telescope photos show that ISON is already becoming quite active, though it's still pretty far from our star. The comet's dusty head, or coma, is about 3,100 miles (5,000 km) wide, and its tail is more than 57,000 miles (92,000 km) long, astronomers said. And ISON sports a dust-blasting jet that extends at least 2,300 miles (3,700 km).

Yet the comet's nucleus is surprisingly small — no more than 3 or 4 miles (4.8 to 6.5 km) across.

This small core makes the comet's behavior on its trip around the sun, which will bring ISON within 730,000 miles (nearly 1.2 million km) of the solar surface on Nov. 28, especially tough to predict, researchers said. Also complicating the forecast is the fact that ISON is apparently making its first trip through the inner solar system from the distant, icy Oort cloud.

So it's difficult to know if ISON will live up to its billing or fizzle out like Comet Kohoutek — another possible "comet of the century" — did in 1973.

But Comet ISON's relatively pristine state has a real upside to astronomers, who will study the material that sublimates off the comet to gain insight into its composition.

"As a first-time visitor to the inner solar system, Comet C/ISON provides astronomers a rare opportunity to study a fresh comet preserved since the formation of the solar system," Jian-Yang Li of the Planetary Science Institute in Tucson, Ariz., who led a team that imaged the comet, said in a statement. "The expected high brightness of the comet as it nears the sun allows for many important measurements that are impossible for most other fresh comets."

NASA has organized a Comet ISON Observing Campaign to coordinate the efforts of observatories on the ground and in space. Hubble is seen as a key player in this campaign, along with a number of other instruments.

Comet ISON is officially designated as C/2012 S1 (ISON) and was discovered in September 2012 by Russian amateur astronomers Vitali Nevski and Artyom Novichonok.

Hubble's new ISON photos were taken just two weeks before the telescope's 23rd anniversary. The Hubble Space Telescope, a collaboration between NASA and the European Space Agency, launched aboard the space shuttle Discovery on April 24, 1990.

Source of Article : space.com

Cosmonauts May Carry Olympic Torch and 'Flame' on Spacewalk

Russia may shift its rocket launch and spacewalk schedule to send the torch — and maybe even the flame — for next year's Olympics to the International Space Station (ISS), according to Russia's federal space agency and local media reports.

Set to host the 2014 Winter Games in Sochi on the Black Sea coast, Russia plans to launch the traditional Olympic torch relay later this year on Oct. 7. As the flame passes between runners in 2,900 towns and cities spread across the country, a replica of the torch and perhaps an imitation of its flame will lift off on a Soyuz spacecraft with the next crew members for the space station.

"No decision has been made so far whether an imitation of the Olympic flame or a torch without fire would be moved into outer space," a source in Russia's rocket industry told the Interfax-AVN news service. "No member of the state commission will assume responsibility for moving an open flame close to the Soyuz spacecraft or the ISS." 

Flame or no flame, Russia's space agency Roscosmos is planning to do more than deliver the torch to the orbiting outpost, a feat that has been achieved before. The idea is to have cosmonauts carry the torch outside the station on a spacewalk prior to it returning to Earth.

According to the Interfax report, the Olympic torch will be "moved into open space" by cosmonauts Oleg Kotov and Sergei Ryazansky, who will arrive at the space station in late September.

To choreograph the orbital torch relay, Roscosmos and its International Space Station partners, including NASA, will need to agree on adjustments to the schedule of launches and spacewalks.

To deliver the lit or unlit torch to the space complex, the planned Nov. 25 liftoff of Soyuz TMA-11M would need to launch almost three weeks earlier on Nov. 7. Roscosmos cosmonaut Mikhail Tyurin, NASA's Rick Mastracchio and Japanese astronaut Koichi Wakata would fly to the space station with the torch.

The spacewalk, which would include other, more routine maintenance tasks for the two cosmonauts to complete in addition to carrying the torch, would then take place during the brief time between the arrival of Soyuz TMA-11M and the departure of Soyuz TMA-09M.

Under the proposed plan, Roscosmos cosmonaut Fyodor Yurchikhin, NASA astronaut Karen Nyberg and European Space Agency (ESA) astronaut Luca Parmitano will stay in space at least a day longer than originally scheduled to return to Earth with the torch on Nov. 11.

The torch's handoff between crews would also result in a short period when nine people would be aboard the space station, a departure from what has in recent years become the norm for crew changes, when the prior crew of three would leave before the next crew arrives.

One of the key symbols of the Games, the torch for the 2014 Sochi Olympics was designed by a team of famous Russian designers and engineers. The aluminum and red torch — red being the traditional color of Russian sports — was crafted to evoke the feathers of a Phoenix, which folklore says brings good fortune and happiness.

How the torches on the ground — there are 14,000 being produced — will differ from the one launching into space, and how the flame will be simulated or safely achieved in orbit, if it is flown, has yet to be released.

If approved, the torch's trip will mark the second time the Olympic torch has arrived aboard the International Space Station. In May 2000, the space shuttle Atlantis launched the STS-101 mission to the orbiting outpost with a replica of the Sydney Summer Olympics torch.

Four years earlier on shuttle Columbia's STS-78 mission, the crew carried an unlit torch into orbit and then took part in the ground-based torch relay soon after landing back on Earth.

The Olympic flame, without the torch, also made its way through space in the form of an electric signal. As part of the 1976 relay, the flame was sent from Greece to Ottawa via satellite. Heat sensors in Greece detected the flame, the signal was transmitted overseas and a laser beam lit the torch.

Source of Article : space.com