SPACE TECH ENVIRONMENT HEALTH

suspiciously regular pulses of radiation were detected coming from space

2011-12-31T23:06:00.000-08:00

In 1967, suspiciously regular pulses of radiation were detected coming from space – so regular that their discoverers thought they could be signals from an alien civilisation. That hypothesis was soon abandoned and the source was named a pulsar, or pulsing star. Since then, the metronomic emissions of gamma rays, X-rays or radio waves from pulsars has made them cosmic chronometers.

That's why Fernando Camilo, an astronomer at Columbia University in New York, was astounded when the radio pulsar he had discovered and had been observing for a year – PSR J1841-0500 – suddenly stopped beaming its regular bursts. "At first I had a hard time believing what I was seeing," he recalls. "For the past year, the pulsar had been so reliable, pulsing brightly once every 1.9 seconds. I thought there must be an error with the equipment."

Intrigued, Camilo kept observing the star at 5-minute intervals once a month either at the CSIRO Parkes Observatory in New South Wales, Australia, where it had been discovered, or at the National Radio Astronomy Observatory in Green Bank, West Virginia. A year and a half later, his hard work paid off when the star came back to life, pulsing just as brightly as before.

Other pulsars have switched off for short periods, but Camilo's has taken by far the longest break ever seen, raising new questions about just how reliable these cosmic clocks are. The finding also adds to the mystery surrounding pulsars, as exactly what makes them tick in the first place isn't well understood either.
Celestial lighthouses

A pulsarMovie Camera is a spinning neutron star – the dense neutron-rich core left over when a dying star explodes in a supernova. It has a very strong magnetic field, stronger than that of any known object in the universe.

Details are elusive, but we know that the rotating magnetic field accelerates charged particles on the star's surface, somehow producing a beam of radiation along the magnetic field axis. This axis is at an angle to the pulsar's rotational axis, so it sweeps through space like the light in a lighthouse. If Earth lies in the beam's path, a pulse of radiation flashes in our sky once every rotation.

The beam of some X-ray-emitting pulsars is so regular that they rival atomic clocks for precision. This property is useful when searching for the effects of gravitational wavesMovie Camera and in satellite navigation.

Some pulsars go dark, though, and Camilo's was not the first. In the 1970s, some regular pulsars were spotted switching off for a few seconds to a few minutes, a phenomenon known as "nulling". And in the past decade, a new class of pulsars has been found , in which the silences can range from minutes to a few hours. They were dubbed rotating radio transients, or RRATs. Around the same time, a pulsar was found that pulsed for about a week and then switched off for about a month before repeating the cycle.

Discovered by NASA's Kepler space telescope, the planets orbit a sun-like star about 950 light years away

2011-12-31T23:04:00.000-08:00

The smallest exoplanets yet found around a normal star span just 1.03 and 0.87 times the Earth's diameter. The worlds, which are probably rocky like Earth, are too close to their host star to harbour life as we know it, but if they formed farther out as is thought, they may once have been habitable.

Discovered by NASA's Kepler space telescope, the planets orbit a sun-like star about 950 light years away called Kepler-20. They smash the previous record for the smallest exoplanet around a living star, a planet 1.4 times as wide as Earth known as Kepler-10b.

"We've crossed the Earth-sized threshold," says Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

The discovery comes just two weeks after the announcement of Kepler's first confirmed planet in the habitable zone around a star of the same type as the sun – though at 2.4 times Earth's width, that planet may be gassy like Neptune. The habitable zone is the region around a star where temperatures are right for liquid water to exist on an object's surface.

That find and the current one "are two big checkmarks" for the Kepler mission, says team member Sara Seager of the Massachusetts Institute of Technology in Cambridge.

Since the only planet known to host life is small and rocky rather than big and gaseous like Jupiter, exoplanet hunters have been searching for such worlds. Kepler's goal is to find true twins of Earth: Earth-sized planets in the habitable zone of their stars. "Now we just have to combine those" two recent finds to find a Goldilocks world like ours, says Seager.
Uncertain mass

It is not clear how massive the two planets are. Kepler finds its quarry by watching the minute dimming of stars as planets cross in front of, or transit, them. But other transiting objects – such as stars or star-like objects known as brown dwarfs – can also dim the target stars.

To distinguish true planets from impostors, the Kepler team uses other telescopes to look for signs that the host star is wobbling due to gravitational tugs from orbiting planets. This wobbling reveals the planets' masses.

But Kepler-20 e, the smaller of the two new planets, and its sibling Kepler-20 f, are too small for their tugs to make a noticeable difference – especially given that three larger planets also whip around the same star on tight orbits. That means e must weigh less than 3 Earth masses and f must be under 14 Earth masses. When theoretical models that include how the planets formed and evolved are taken into account, those upper limits drop to 1.67 and 3.04 Earth masses, respectively.

Those masses, combined with the planets' sizes, suggest the worlds are rocky, says Seager. Both probably have bulk compositions similar to Earth's, with an iron core and a silicate mantle.

But the lack of a measurement of the star's wobble due to these planets means the new finds cannot be officially confirmed as planets. Instead, Fressin and colleagues painstakingly "validated" the finds by modelling all other possible explanations, including brown dwarfs, on NASA's fastest supercomputer. They also checked that no nearby stars could be the culprit and double-checked the transit signal with the infrared Spitzer Space Telescope.

moving boulders about on the surface of Mars, causing curious clumps near the northern ice cap

2011-12-31T23:01:00.000-08:00

Something has been moving boulders about on the surface of Mars, causing curious clumps near the northern ice cap. Now it seems the culprit is not Martians, but a seasonal shell of carbon dioxide ice that encases the boulders in winter.

You would expect boulders to be sprinkled across the Martian surface more or less randomly. So it was surprising when high-resolution images from NASA's Mars Reconnaissance Orbiter revealed that they were clustered near the edges of polygon-shaped patterns on the surface, at high northern latitudes.

The polygon shapes themselves are thought to be created when the ground repeatedly contracts and expands every winter and summer. A similar process has been observed in polar latitudes on Earth.

The arrangement of Martian boulders suggests they have moved over time. To find out how quickly the rocks are shifting, Travis Orloff at the University of California, Santa Cruz, and colleagues estimated the age of the surfaces on which the boulders rest by measuring how eroded local impact craters are. They found that the craters are between 10,000 and 1 million years old. The polygons are 5 to 20 metres across, "so boulders must have moved microns to a millimetre a year", says team member Erik Asphaug of UCSC. That may sound sluggish but it's quite a pace for a Martian boulder.
Icy slab

So what is moving them? Well, the boulders lie in a region where they are covered by a metre-thick layer of carbon dioxide frost during the winter. The team suggests that heat from buried soil, which is warmer than the surface in winter, could rise and vaporise the bottom of this icy CO2 layer, detaching it from the ground. The icy slab traps the boulders, holding them in place as the underlying soil cools and the polygons shrink.

Then, in the spring, heat from above the slab vaporises the ice and dumps the boulders back on the ground. The boulders are now closer to the edges of the polygons than they were before. The process then repeats itself each year, and the boulders are gradually moved towards the outer edge of the polygons. They tend to stop when they reach the edges of the polygons because of the cracks between the shapes, which act as a brake to the motion.

Giant planets like Jupiter and Saturn are thought to have begun their lives as solid bodies of rock and ice.

2011-12-31T22:58:00.000-08:00

The work could help explain why its core appears smaller and its atmosphere richer in heavy elements than predicted.

Giant planets like Jupiter and Saturn are thought to have begun their lives as solid bodies of rock and ice. When they grew to about 10 times the mass of Earth, their gravity pulled in gas from their birth nebula, giving them thick atmospheres made mainly of hydrogen.

Curiously, some studies have suggested that Jupiter's core may weigh less than 10 Earths, while the core of its smaller sibling Saturn packs a bigger punch at 15 to 30 Earths. Last year, researchers led by Shu Lin Li of Peking University in China offered a grisly explanation – a rocky planet bigger than Earth slammed into Jupiter long ago, vaporising most of the giant planet's core.

That scenario could also explain another mystery – why Jupiter's atmosphere contains a higher fraction of heavy elements than the sun, whose composition is thought to mirror that of the nebula that gave birth to the solar system's planets.

Now Hugh Wilson and Burkhard Militzer of the University of California, Berkeley, suggest a competing – though no less macabre – explanation: Jupiter's core has gradually been dissolving since its formation 4.5 billion years ago.
Quantum calculations

Other researchers had propoposed that the intense pressures and temperatures at Jupiter's heart might cause its core to dissolve into the surrounding atmosphere, which is at such high pressure that it behaves somewhat like a liquid.

"We sat down to figure out, does this actually happen?" says Wilson.

The researchers used the equations of quantum mechanics to see how the mineral magnesium oxide – thought to be a constituent of Jupiter's core – behaves at Jupiter-like pressures of about 40 million Earth atmospheres and temperatures of 20,000 °C. Such conditions cannot be recreated in Earth labs – some experiments can approximate the pressures but overshoot the temperatures by factors of a hundred or so.

Variable dark energy could explain old galaxy clusters

2011-12-31T22:54:00.000-08:00

Variable dark energy could explain old galaxy clusters

Does dark energy change over time? An alternative model of the as yet undetected entity that is thought to be accelerating the universe's expansion could explain some puzzling observations of galaxy clusters. But it will have to jump many more hurdles to compete with the simplest and so far most successful model of the elusive entity.

That model, called the cosmological constant, holds that there is a certain amount of repulsive energy in every cubic centimetre of space, and that amount stays the same over time. As the universe expands, more space exists, and so the expansion accelerates.

Now Edoardo Carlesi of the Autonomous University in Madrid, Spain, and his colleagues have simulated a universe where the amount of repulsive energy per unit of volume changes with time.

They say the model can explain how several galaxy clusters grew to weigh as much as a quadrillion (1015) suns by the time the universe was just 6 billion years old. That's a puzzle because some researchers say 6 billion years would not have been enough time for gravity to amass such large structures.
Standard recipe

The puzzle arises if the standard "recipe" for the universe is used. The ingredients for that recipe are a large amount of dark energy, in the form of a cosmological constant, and a dollop of matter. Their ratio has been calculated by studying the cosmic microwave background, radiation that reveals the distribution of matter and energy in the early universe.

Looking at the cosmic microwave background data through the lens of a different dark energy model can produce different ratios of ingredients. The cosmological constant model allows for matter to make up 27 per cent of the universe's energy density, whereas the dark energy model studied by Carlesi's team provides a more generous helping: 39 per cent.

Massive clusters can form up to 10 times as often using this recipe, the researchers say. "You can explain current observations within a model that allows much more matter," says Carlesi. As a result, galaxies attract other galaxies through their gravitational pull, so massive clusters form faster.

ASTRONAUTS will soon be able to stay fit thanks to a body tracking camera system built into Microsoft's Kinect gaming sensor

2011-12-31T22:53:00.000-08:00

ASTRONAUTS will soon be able to stay fit thanks to a body tracking camera system built into Microsoft's Kinect gaming sensor, which helps calculate their weight in zero gravity.

Even during missions that last just a few weeks space farers can lose up to 15 per cent of their body mass because their muscles atrophy due to lack of use. To prevent this physical decline, crew aboard the International Space Station (ISS) typically spend 2 hours exercising per day.

Monitoring weight in space is not easy, though, since traditional scales don't work in orbit.

The problem was partially solved in 1965 by William Thornton, an American astronaut and doctor who came up with a way to measure objects using oscillating springs. Astronauts still use a similar device today, in which they have to mount a stool fitted with a spring that raises and lowers the stool at a frequency that depends on the mass it is acting against.

The trouble is that this system is bulky and a lot of energy is required to power the moving stool, using up two of the space station's most limited resources. Now Carmelo Velardo, a computer scientist at Eurecom in Alpes-Maritimes, France, says his new system could simply be integrated into the station itself.

"Something that you could easily put inside the walls of the space station would free up the space for other equipment or experiments," Velardo says.

Along with colleagues at the Italian Institute of Technology's Center for Human Space Robotics in Torino, he used the Kinect's depth-sensing ability to create a 3D model of an astronaut. Then the team ran their calculation using a statistical model that links weight to body measurements based on a database of 28,000 people. Velardo's estimates are 97 per cent accurate, corresponding to an average error of just 2.7 kilograms, which is comparable to the current method used on board the ISS.

"This technique appears feasible, although not without some effort," says John Charles, chief scientist on NASA's human research programme in Houston, Texas. He says that microgravity shifts water around inside astronauts' bodies, which means their density may not match the assumptions in the model.

Charles adds that combining the idea with the existing weighing system might prove more beneficial, as the Kinect measures body volume while the stool measures mass. "The combination would provide insights into changes in body density that might be illuminating," Velardo agrees.

space tourist, preparing for lift-off. Yet rather than a deafening roar

2011-12-31T22:52:00.000-08:00

Imagine you're a space tourist, preparing for lift-off. Yet rather than a deafening roar, followed by shaking and shuddering as the rocket engine fires up, you experience a serene stillness as the countdown continues.

"5, 4, 3, 2, 1..." And you're away. You are pressed into your seat as the spacecraft ascends into the sky. But it's a gentle push, not a blood-draining, face-distorting squeeze. And apart from the voices of the pilots beside you and the rush of air around the capsule, there is only silence. Outside, the darkening sky outlines the steadily growing curvature of the Earth. Before long, the sky is completely black, while the planet below has turned blue. You have reached the edge of space, and there's not a rocket in sight.

Several companies hope to make their fortune by opening up space travel to people with the right stuff - money, in this case. Almost all the firms plan to do so using rockets, though, and rockets are dangerous. Of the 500-odd people launched into space so far, 18 have died. For some people, the risk is surely part of the attraction. But what if you wanted the serene experience of looking at the blue marble without the risk of meeting a sticky end? José Mariano López-Urdiales thinks he has the answer: space ballooning.

The company he founded, Zero2Infinity, based in Barcelona, Spain, hopes to start taking people up to near-space as early as 2013. Balloons cannot go as high as rockets, but in theory at least they should be far safer, since passengers won't be sitting on tonnes of explosives. Their environmental impact is also far lower than that of smoke-belching rockets.

López-Urdiales was inspired by his father, an atmospheric physicist who was involved in sending probes to Titan and Mars. "I've always seen him working, seen all the excitement of years of work going into a flight. That's what got me excited about space in general," he says. Then, in 2000, his father told him about how the Huygens probe that explored Titan was tested by dropping a prototype from a balloon around 40 kilometres up. "After our conversation, I thought if there's going to be space tourism, then let's try this way," he says.

There is no doubt that it is possible, because it has been done many times before. In the 1950s and 1960s, more than a dozen crewed balloons journeyed to near-space. In 1957, for instance, Joe Kittinger of the US air force ascended to a height of 29 kilometres in a capsule attached to a helium balloon. He enjoyed the ride so much that when ordered to descend, he replied: "Come and get me."

Zero2Infinity hopes to spread that joy to the civilian population. The company has carried out several test flights of uncrewed balloons, and earlier this year got the funding needed to carry out its first flight carrying people.

The plan is to use a massive helium "bloon", as the company likes to call it, to carry a pressurised capsule with space for two pilots and two passengers up to 34 kilometres above the Earth. You can book now - but at €110,000 per ticket, you'll need a little spare cash.

Will all that money really get you into space? According to one widely accepted definition, space begins 100 kilometres above the Earth's surface, so most space tourism groups, such as Virgin Galactic, aim to take their passengers that far up.

That is more than twice the height a balloon can reach, and Zero2Infinity's website uses the term "near-space" rather than "space". López-Urdiales, however, points out that there is no clear physical boundary. At 34 kilometres, you are above more than 99 per cent of the atmosphere, he told attendees last October at a sustainability symposium in the Maldives. And even 400 kilometres up, at the height of the International Space Station, there is still a very thin atmosphere.

The balloon's altitude is not the only issue. Passengers will also miss out on the thrill of high g-forces and subsequent weightlessness. But is the point of space travel to get funfair thrills that you could experience far more cheaply by taking a plane ride on a weightlessness-producing "vomit comet"?

López-Urdiales thinks the defining experience of space travel isn't the vomiting, weightlessness or g-forces. It's the "overview effect" - the blissful sense of connection so many astronauts report after gazing down at our blue planet from above. According to anecdotal reports, this experience has lasting effects on those who experience it.

NASA has launched two probes that will study the moon's internal structure

2011-12-31T22:42:00.000-08:00

The man in the moon is about to have his innards' scanned. NASA has launched two probes that will study the moon's internal structure in unprecedented detail, shedding light on whether a second moon crashed into it long ago.

The probes, together called GRAIL (Gravity Recovery and Interior Laboratory), lifted off on Saturday at 0908 EDT from Cape Canaveral Air Force Station in Florida. Lift-off was originally set for 8 September but was postponed due to high winds.

After they reach the moon in about four months' time, the probes will measure slight variations in the strength of the moon's gravity, which isn't uniform due to the uneven distribution of matter inside it.