SPACE - Cosmic spider is good mother

Hanging above the Large Magellanic Cloud (LMC) – one of our closest galaxies – in what some describe as a frightening sight, the Tarantula nebula is worth looking at in detail. Also designated 30 Doradus or NGC 2070, the nebula owes its name to the arrangement of its brightest patches of nebulosity that somewhat resemble the legs of a spider. This name, of the biggest spiders on the Earth, is also very fit-ting in view of the gigantic proportions of the celestial nebula - it measures nearly 1,000 light years across! The Tarantula nebula is the largest emission nebula in the sky and also one of the largest known star-forming regions in all the Milky Way's neighbouring galaxies. Located about 170,000 light-years away, in the southern constellation Dorado (The Swordfish), it can be seen with the unaided eye.

As shown in this image obtained with the FORS1 multi-mode instrument on Eso's Very Large Tele-scope, its structure is fascinatingly complex, with a large number of bright arcs and apparently dark areas in between. Inside the giant emission nebula lies a cluster of young, massive and hot stars, denoted R 136, whose intense radiation and strong winds make the nebula glow, shaping it into the form of a giant arachnid. The cluster is about 2 to 3 million years old, that is, almost from 'yesterday' in the 13.7 billion year history of the Universe.

Several of the brighter members in the immediate surroundings of the dense cluster are among the most massive stars known, with masses well above 50 times the mass of our Sun. The cluster itself contains more than 200 massive stars.

In the upper right of the image, another cluster of bright, massive stars is seen. Known to astronomers as Hodge 301, it is about 20 million years old, or about 10 times older than R136. The more massive stars of Hodge 301 have therefore already exploded as supernovae, blasting material away at tremendous speed and creating a web of entangled filaments. More explosions will come soon – in astronomical terms – as three red supergiants are indeed present in Hodge 301 that will end their life in the gigantic firework of a supernova within the next million years.

While some stars are dying in this spidery cosmic inferno, others are yet to be born. Some structures, seen in the lower part of the image, have the appearance of elephant trunks, not unlike the famous and fertile "Pillars of Creation" at the top of which stars are forming. In fact, it seems that stars form all over the place in this gigantic stellar nursery and in all possible masses, at least down to the mass of our Sun. In some places, in a marvellous recycling process, it is the extreme radiation from the hot and massive stars and the shocks created by the supernova explosions that has compressed the gas to such extent to allow stars to form.

To the right and slightly below the central cluster, a red bubble is visible. The star that blows the mate-rial making this bubble is thought to be 20 times more massive, 130 000 times more luminous, 10 times larger and 6 times hotter than our Sun. A fainter example of such a bubble is also visible just above the large red bubble in the image.

Earlier colour composite images of the Tarantula nebula have been made with other instruments and/or filters at Eso's telescopes, e.g. PR Photo 05a/00 in visual light with FORS2 at the VLT at Paranal, and PR Photos 14a-g/02 and 34a-h/04 with the Wide-Field Imager at the ESO/MPG 2.2-m telescope at La Silla.

Crashing into the moon...on purpose

It might sound hard to believe, but dozens of spacecraft have crashed themselves onto the surface of the Moon. All in the name of science. The first was the Soviet spacecraft Luna 2, which smashed into the lunar surface in 1959. Well, an upcoming mission is all set to do it again. NASA’s Lunar CRater Observation and Sensing Satellite (LCROSS) will launch in 2008 together with the Lunar Reconnaissance Orbiter. Its booster rocket will smash into the Moon first, carving out a large crater, and then the smaller Shepherding spacecraft will smash into the same spot, analyzing the debris cloud before it’s destroyed too.

In 1959, a spaceship fell out of the lunar sky and hit the ground near the Sea of Serenity. The ship itself was shattered, but its mission was a success. Luna 2 from the Soviet Union had became the first manmade object to “land” on the Moon.

This may seem hard to believe, but Luna 2 started a trend: Crash landing on the Moon, on purpose. Dozens of spaceships have done it.

NASA’s first kamikazes were the Rangers, built and launched in the early 1960s. Five times, these car-sized spaceships plunged into the Moon, cameras clicking all the way down. They captured the first detailed images of lunar craters, then rocks and soil, then oblivion. Data beamed back to Earth about the Moon’s surface were crucial to the success of later Apollo missions.

Even after NASA mastered soft landings, however, the crashing continued. In the late 1960s and early 70s, mission controllers routinely guided massive Saturn rocket boosters into the Moon to make the ground shake for Apollo seismometers. Crashing was much easier than orbiting, they discovered. The Moon’s uneven gravity field tugs on satellites in strange ways, and without frequent course corrections, orbiters tend to veer into the ground. Thus the Moon became a convenient graveyard for old spaceships: All five of NASA’s Lunar Orbiters (1966-1972), four Soviet Luna probes (1959-1965), two Apollo sub-satellites (1970-1971), Japan’s Hiten spacecraft (1993) and NASA’s Lunar Prospector (1999) ended up in craters of their own making.

All this experience is about to come in handy. NASA researchers have a daring plan to find water on the Moon and they’re going to do it by–you guessed it–crash landing. The mission’s name is LCROSS, short for Lunar CRater Observation and Sensing Satellite. Team leader Tony Colaprete of NASA Ames explains how it’s going to work:

“We think there’s frozen water hiding inside some of the Moon’s permanently-shadowed craters. So we’re going to hit one of those craters, kick up some debris, and analyze the impact plumes for signs of water.”

The experiment couldn’t be more important. NASA is returning to the Moon, and when explorers get there, they’ll need water. Water can be split into hydrogen for rocket fuel and oxygen for breathing. It can be mixed with moondust to make concrete, a building material. Water makes an excellent radiation shield, and when you get thirsty you can drink it. One option is to ship water directly from Earth, but that’s expensive. A better idea would be to mine water directly from the lunar soil.

But is it there? That’s what LCROSS aims to find out.

The quest begins in late 2008 when LCROSS leaves Earth tucked inside the same rocket as Lunar Reconnaissance Orbiter (LRO), a larger spacecraft on a scouting mission of its own. After launch, the two ships will split up and head for the Moon, LRO to orbit, LCROSS to crash.

Actually, says Colaprete, “we’re going to crash twice.” LCROSS is a double spacecraft: a small, smart mothership and a big, not-so-smart rocket booster. The mothership is called the “Shepherding Spacecraft” because it shepherds the booster to the Moon. They’ll travel to the Moon together, but hit separately.

The booster strikes first, a savage blow transforming 2-tons of mass and 10 billion joules of kinetic energy into a blinding flash of heat and light. Researchers expect the impact to gouge a crater ~20 meters wide and throw up a plume of debris as high as 40 km.

Close behind, the Shepherding Spacecraft will photograph the impact and then fly right through the debris plume. Onboard spectrometers can analyze the sunlit plume for signs of water (H2O), water fragments (OH), salts, clays, hydrated minerals and assorted organic molecules. “If there’s water there, or anything else interesting, we’ll find it,” says Colaprete.

The Shepherd then begins its own death plunge. Like the old Rangers, it will dive toward the lunar surface, cameras clicking. Back on Earth, mission controllers will see the booster’s glowing crater swell to fill the field of view–an exhilarating rush.

Until the very end, the Shepherd’s spectrometers will keep sniffing for water. “We’ll be able to monitor the data stream down to 10 seconds before impact,” says Colaprete. “And we should have enough control to land within 100 meters of the booster’s crash site.”

The Shepherd is 1/3rd lighter than the booster, so its impact will be proportionally smaller. Nevertheless, the Shepherd will make its own crater and plume, adding to those of the booster. Astronomers hope the combined plumes will be visible from Earth, allowing observations to continue even after the Shepherd is destroyed.

Many readers will remember the crash of Lunar Prospector in 1999. Mission controllers guided the ship into Shoemaker crater near the Moon’s south pole in hopes of kicking up water—just like LCROSS. But no water was found.

“LCROSS has a better chance of success,” says Colaprete. For one thing, LCROSS delivers more than 200 times the impact energy of Lunar Prospector, excavating a deeper crater and throwing debris higher where it can be plainly seen. While Lunar Prospector’s plume was observed only by telescopes on Earth a quarter-million miles away, LCROSS’s plume will be analyzed by the Shepherding Spacecraft at point blank range, using instruments specifically designed for the purpose.

Only one question remains: Where will LCROSS strike?

“We haven’t decided,” he says. The best places are probably polar craters with shadowy bottoms where water deposited by comets long ago may have frozen and survived to the present-day. Less orthodox choices include canyons, rilles and lava tubes. “There are many candidates. We’re convening a meeting of researchers to debate the merits of various sites and, finally, to pick one.”

Earth sized planets could be nearby

Nearly all of the extrasolar planets discovered so far have been huge, Jupiter-sized and above. The question is: could smaller, Earth-sized planets last in the same star systems? Researchers created a simulation where tiny planets were put into the same system as larger planets to see if they could gather enough material to become as large as the Earth. They found that one nearby system - 55 Cancri - could have formed terrestrial planets, with substantial water in the habitable zone.

The steady discovery of giant planets orbiting stars other than our sun has heightened speculation that there could be Earth-type worlds in nearby planetary systems capable of sustaining life. Now researchers running computer simulations for four nearby systems that contain giant planets about the size of Jupiter have found one that could have formed an Earth-like planet with the right conditions to support life.

A second system is likely to have a belt of rocky bodies the size of Mars or smaller. The other two, the models show, do not have the proper conditions to form an Earth-size planet. Each system lies within 250 light years of Earth (a light year is about 5.88 trillion miles). Astronomers already have found evidence that each system contains at least two giant planets about the mass of Jupiter, which have migrated close to their stars, perhaps as close as Mercury is to the sun.

For each of the four systems, the researchers conducted 10 computerized simulations that placed small planet embryos, or protoplanets, in the system to see if they are able to gather more material and form a true planet the size of Earth. Each simulation assumed the same conditions in the planetary system except that the position and mass of each protoplanet was altered slightly, said Sean Raymond, a postdoctoral researcher at the University of Colorado, who took part in the work while he was an astronomy doctoral student at the University of Washington.

Raymond is lead author of a paper describing the research published in June in the Astrophysical Journal. Co-authors are Rory Barnes, a postdoctoral researcher at the University of Arizona who also took part in the work while a UW astronomy doctoral student, and Nathan Kaib, a UW doctoral student in astronomy. The work was funded by the National Aeronautics and Space Administration, NASA’s Astrobiology Institute and the National Science Foundation.

“It’s exciting that our models show a habitable planet, a planet with mass, temperature and water content similar to Earth’s, could have formed in one of the first extrasolar multi-planet systems detected,” Barnes said.

Recent studies show many known extrasolar planetary systems have regions stable enough to support planets ranging from the mass of Earth to that of Saturn. The UW models tested planet formation in systems called 55 Cancri, HD 38529, HD 37124 and HD 74156. The researchers assumed the systems are complete and the orbits of their giant planets are well established. They also assumed conditions that might allow formation of small bodies that could develop into rocky, Earth-like planets.

In the models, the scientists placed moon-sized planet embryos between giant planets and allowed them to evolve for 100 million years. With those assumptions, they found terrestrial planets formed readily in 55 Cancri, sometimes with substantial water and orbits in the system’s habitable zone. They found HD 38529 is likely to support an asteroid belt and Mars-sized or smaller bodies but no notable terrestrial planets. No planets formed in HD 37124 and HD 74156.

“What surprised me the most was to see the system that only formed planets the size of Mars or smaller,” Raymond said. “Anything that grew too big would be unstable, so there was an accumulation of a lot of smaller protoplanets maybe one-tenth the size of Earth”

It was significant, Kaib said, that the models showed conditions could remain stable enough for 100 million years so that a planetary embryo would have a chance to gather more substance and develop into a body the size of the moon or Mars. “In our early system, that’s probably what our inner solar system looked like, with hundreds of bodies that size,” he said

Extrasolar planets have been discovered with increasing frequency in recent years because of techniques that detect giant planets by their gravitational effect on their parent stars. It is uncertain how the giant planets evolve, but they are thought to form far away from their host stars and then migrate inward, pushed by the gas discs from which they formed. If the migration occurs late in the system’s development, the giant planets might destroy most of the materials needed to build Earth-like planets, Raymond said. He noted that while the presence of giant planets is fairly well established, it will be some time before it is possible to detect much smaller Earth-sized planets around other stars.

For another recent paper, Raymond ran more than 450 computer simulations to map giant planet orbits that allow Earth-like planets to form. If a giant planet is too close it will prevent rocky material from amassing into an Earth-sized planet. That study showed that only about 5 percent of the known giant-planet systems are likely to have Earth-like planets. But because of long observation times and sensitive equipment needed to detect planets the size of Saturn and Jupiter, it is possible there could be many planetary systems such as ours in this galaxy, he said.

Electrical dust storms could make life on mars impossible

New research is suggesting that planet-wide dust storms on Mars could create a snow of corrosive chemicals toxic to life. These Martian storms generate a significant amount of static electricity, and could be capable of splitting carbon dioxide and water molecules apart. The elements could then reform into hydrogen peroxide molecules, and fall to the ground as a snow that would destroy organic molecules associated with life. This toxic chemical might be concentrated in the top layers of Martian soil, preventing life from surviving.

The planet-wide dust storms that periodically cloak Mars in a mantle of red may be generating a snow of corrosive chemicals, including hydrogen peroxide, that would be toxic to life, according to two new studies published in the most recent issue of the journal Astrobiology.

Based on field studies on Earth, laboratory experiments and theoretical modeling, the researchers argue that oxidizing chemicals could be produced by the static electricity generated in the swirling dust clouds that often obscure the surface for months, said University of California, Berkeley, physicist Gregory T. Delory, first author of one of the papers. If these chemicals have been produced regularly over the last 3 billion years, when Mars has presumably been dry and dusty, the accumulated peroxide in the surface soil could have built to levels that would kill “life as we know it,” he said.

“If true, this very much affects the interpretation of soil measurements made by the Viking landers in the 1970s,” said Delory, a senior fellow at UC Berkeley’s Space Sciences Laboratory. A major goal of the Viking mission, comprised of two spacecraft launched by NASA in 1975, was testing Mars’ red soil for signs of life. In 1976, the two landers aboard the spacecraft settled on the Martian surface and conducted four separate tests, including some that involved adding nutrients and water to the dirt and sniffing for gas production, which could be a telltale sign of living microorganisms.

The tests were inconclusive because gases were produced only briefly, and other instruments found no traces of organic materials that would be expected if life were present. These results are more indicative of a chemical reaction than the presence of life, Delory said.

“The jury is still out on whether there is life on Mars, but it’s clear that Mars has very chemically reactive conditions in the soil,” he said. “It is possible there could be long-term corrosive effects that would impact crews and equipment due to oxidants in the Martian soil and dust.”

All in all, he said, “the intense ultraviolet exposure, the low temperatures, the lack of water and the oxidants in the soil would make it difficult for any microbe to survive on Mars.”

The article by Delory and his colleagues appearing in the June issue of Astrobiology demonstrates that the electrical fields generated in storms and smaller tornadoes, called dust devils, could split carbon dioxide and water molecules apart, allowing them to recombine as hydrogen peroxide or more complicated superoxides. All of these oxidants react readily with and destroy other molecules, including organic molecules that are associated with life.

A second paper, coauthored by Delory, demonstrates that these oxidants could form and reach such concentrations near the ground during a storm that they would condense into falling snow, contaminating the top layers of soil. According to lead author Sushil K. Atreya of the Department of Atmospheric, Oceanic, and Space Sciences at the University of Michigan, the superoxidants not only could destroy organic material on Mars, but accelerate the loss of methane from the atmosphere.

Coauthors of the two papers are from NASA Goddard Space Flight Center; the University of Michigan; Duke University; the University of Alaska, Fairbanks; the SETI Institute; Southwest Research Institute; the University of Washington, Seattle; and the University of Bristol in England.

Delory and his colleagues have been studying dust devils in the American Southwest to understand how electricity is produced in such storms and how the electric fields would affect molecules in the air - in particular, molecules like those in the thin Martian atmosphere.

“We are trying to look at the features that make a planet habitable or uninhabitable, whether for life that developed there or for life we bring there,” he said.

Based on these studies, he and his colleagues used plasma physics models to understand how dust particles rubbing against one other during a storm become positively and negatively charged, much the way static electricity builds up when we walk across a carpet, or electricity builds in thunderclouds. Though there’s no evidence for lightning discharges on Mars, the electric field generated when charged particles separate in a dust storm could accelerate electrons to speeds sufficient to knock molecules apart, Delory and his colleagues found.

“From our field work, we know that strong electric fields are generated by dust storms on Earth. Also, laboratory experiments and theoretical studies indicate that conditions in the Martian atmosphere should produce strong electric fields during dust storms there as well,” said co-author Dr. William Farrell of NASA’s Goddard Space Flight Center in Greenbelt, Md.

Since water vapor and carbon dioxide are the most prevalent molecules in the Martian atmosphere, the most likely ions to form are hydrogen, hydroxyl (OH) and carbon monoxide (CO). One product of their recombination, according to the second study, would be hydrogen peroxide (H2O2). At high enough concentrations, the peroxide would condense into a solid and fall out of the air.

If this scenario has played out on Mars for much of its history, the accumulated peroxide in the soil could have fooled the Viking experiments looking for life. While the Labeled Release and the Gas Exchange experiments on the landers detected gas when water and nutrients were added to Martian soil, the landers’ Mass Spectrometer experiment found no organic matter.

At the time, researchers suggested that very reactive compounds in the soil, perhaps hydrogen peroxide or ozone, could have produced the measurements, imitating the response of living organisms. Others suggested a possible source for these oxidants: chemical reactions in the atmosphere catalyzed by ultraviolet light from the sun, which is more intense because of Mars’ thin atmosphere. The predicted levels were far lower than needed to produce the Viking results, however.

Production of oxidants by dust storms and dust devils, which seem to be common on Mars, would be sufficient to cause the Viking observations, Delory said. Thirty years ago, some researchers considered the possibility that dust storms might be electrically active, like Earth’s thunderstorms, and that these storms might be a source of the new reactive chemistry. But this had been untestable until now.

“The presence of peroxide may explain the quandary we have had with Mars, but there is still a lot we don’t understand about the chemistry of the atmosphere and soils of the planet,” he said.

The theory could be tested further by an electric field sensor working in tandem with an atmospheric chemistry system on a future Mars rover or lander, according to the team members.

The team includes Delory, Atreya, Farrell, and Nilton Renno & Ah-San Wong of the University of Michigan; Steven Cummer of Duke University, Durham, N.C.; Davis Sentman of the University of Alaska; John Marshall of the SETI Institute in Mountain View, Calif.; Scot Rafkin of the Southwest Research Institute in San Antonio, Texas; and David Catling of the University of Washington.

The research was funded by NASA’s Mars Fundamental Research Program and by NASA Goddard internal institutional funds.

Galaxy evolution in cyber universe

Scientists at the University of Chicago have bolstered the case for a popular scenario of the big bang theory that neatly explains the arrangement of galaxies throughout the universe. Their supercomputer simulation shows how dark matter, an invisible material of unknown composition, herded luminous matter in the universe from its initial smooth state into the cosmic web of galaxies and galaxy clusters that populate the universe.
Previous studies by other researchers had already verified the main features of this scenario, called the cold dark matter model. The Chicago team further extended this work by comparing the results of their supercomputer simulations to the newest, most detailed astronomical observations available today. They found an excellent fit, and they did so without basing their simulations on a lot of complex assumptions.

"The model we use is really, really simple," said Andrey Kravtsov, Associate Professor in Astronomy & Astrophysics. "We want to see how well this framework can do with a minimum number of assumptions."

A paper co-authored by Kravtsov, Charlie Conroy and Risa Wechsler describing these findings will be published in the June 20 issue of the Astrophysical Journal. The research was funded by a grant from the National Science Foundation, with additional support from the National Aeronautics and Space Administration.

Simulations that Kravtsov's team conducted two years ago had predicted that galaxies of different luminosity or brightness would cluster differently when the universe was young than they do today. The team's Astrophysical Journal paper verifies that prediction and shows that similar differences appear in the recent data.

"In the early stages of evolution of the universe, each galaxy has a high probability of having a close neighbor of similar luminosity," Kravtsov said, much more so than galaxies today. "That was what was predicted and that's what the observations now seem to show us."

The data that Kravtsov's team compared to its simulations came from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) survey, and from the Sloan Digital Sky Survey.

Using the Keck 10-meter telescopes in Hawaii, DEEP2 took detailed observations of how galaxies were clustered seven billion years ago, when the universe was approximately half its current age. The Sloan Survey, meanwhile, provided additional data regarding galaxy clustering from more recent epochs in the history of the universe.

"We essentially have data on the distribution of galaxies over most of the evolution of the universe, and the data are accurate," Kravtsov said. "Although the measurements at earlier epochs have larger errors, due to smaller data sets, their accuracy and power to constrain theoretical models is quite remarkable."

The Chicago scientists based their supercomputer simulations on the assumption that galaxies form in the center of dark-matter halos.

According to this scheme, gravity causes the dark matter in these regions to collapse into halos. These halos provide a central location where normal matter consisting of hydrogen, helium and a small amount of heavier elements would collect in gaseous form. Once this gas had cooled and condensed, it achieved sufficient density for star formation to begin on a galactic scale.

When the Chicago team compared the distribution of galaxies in its cyber universe to the real one, "that scheme turned out to work extremely well," Kravtsov said. "It wasn't guaranteed that it would actually work so well in reproducing the data."

Some fields of astrophysics are less fortunate: they have a large body of data but no way to explain it. "The data just kind of hang there. Nobody quite understands what it's telling us or how to interpret it."

But the Chicago simulations further support the idea that the universe behaves the way the cold dark matter scenario tells them it should, that galaxies tend to form in high-density regions of dark matter.

"We understand the distribution of these dark-matter halos, and the implication of this analysis is that we also understand how the properties of these halos are related to galaxy luminosity, how bright the galaxy is," Kravtsov said.

Brighter galaxies also are found in more pronounced large-scale structures. "If you look at fainter galaxies, their distribution becomes more diffuse. We can still see structure, but it's not as pronounced."

Additional data continues to become available. For example, the Sloan Survey has gone beyond mapping the galaxies to include measurements of the dark matter that surrounds them. And other new, high-quality data regarding the distribution of galaxies from the very early stages in the evolution of the universe are becoming available. The first comparisons of the theory's predictions with that data indicate good agreement over the span of about 12 billion years, Kravtsov said.

Gravity tractobeam for asteroids

Forget about nuclear weapons, if you need to move a dangerous asteroid, you should use a tractor beam. Think that’s just Star Trek science? Think again. A team of NASA astronauts have recently published a paper in the Journal Nature. They’re proposing an interesting strategy that would use the gravity of an ion-powered spacecraft parked beside an asteroid to slowly shift it out of a hazardous orbit. Dr. Stanley G. Love is member of the team and speaks to me from his office in Houston.

Fraser Cain: Dealing with asteroids that are going to hit the Earth, now as I understand it, you need to find a crew of top quality oil miners. And you need to put them on the Space Shuttle and send them with a bunch of nuclear bombs to the asteroid to blow it up. Now you’re telling me that maybe this isn’t the best way?

Dr. Stanley G. Love: Well, it depends on what your goal is. If your goal is to make a movie that’s going to make a ton of money, then go wild; that’s exactly the right way to do it. If your goal is to actually prevent an impact with the Earth, though, we’re hoping there might be a simpler method of dealing with this.

Fraser: All right, so what’s the simpler method that you’re suggesting?

Love: Well, the method that we’re suggesting is to send a relatively large and heavy spacecraft - not so large and heavy that we can’t imagine it - to the asteroid, and instead of trying to blow up the asteroid, or land on it and push the thing aside (both of those ideas have been suggested, but they have some difficulties), we’re suggesting you just park the spacecraft next to it and let it hover there. And if you let it hover there for something like a year, very very gradually, the tiny gravitational pull between the asteroid and the spacecraft is going to pull the asteroid over in the direction of the spacecraft. The spacecraft is hovering in a constant distance from the asteroid, and what this means is that it’s very gradually pulling the asteroid off course using gravity as sort of a tow line. And if you can get enough warning on your asteroid - if you know it’s coming 20 years or so before it’s going to hit - then you can get the spacecraft out there and have it pull for about a year, you can pull it enough so that instead of hitting the Earth, it will miss the Earth.

Fraser: Now all the media, and all of those disaster movies revolve around some astronomer spotting a dangerous asteroid three months before it’s going to hit. It sounds like your solution is more in the 20 year range. Do you think that’s the more realistic scenario now these days?

Love: It’s hard to know. We haven’t really discovered all of the asteroids that could potentially hit the Earth yet. We’ve got a lot of people very busily working on that problem; there are searches going on every night. I think a lot of them are automated, and not some lonely guy on a mountaintop with his eye to the lens of a telescope there. And it is possible that tomorrow we could realize that there’s something coming that could hit us that we didn’t know about and it could be three months away from impacting the Earth. That would be certainly unfortunate. But in the future we are likely to know all these things; know all their orbits, and we can predict a hit long before it’s going to hit us. And that’s the sort of scenario that our solution will be able to deal with.

Fraser: And so what size of asteroids would you be able to deal with?

Love: A couple hundred metres in size. So the size of a football stadium or convention center.

Fraser: And what would the spacecraft itself look like? What kind of components would it have on it?

Love: When we came up with the idea for our little paper, we pulled a spacecraft design essentially off the shelf. It’s NASA’s Prometheus project, where they were going to send a large nuclear powered spacecraft to orbit Jupiter’s moon Europa, and do a lot of interesting science there. It’s a 20-ton spacecraft with electric thrusters, that is it uses electric power to heat a gas to extremely high temperatures and squirt it out the back. You get marvelous fuel economy; a lot of ability to move a spacecraft with a small amount of fuel, but the thrust is really low. You can only get a newton, or so (a fifth of a pound) of force. So you have a large electric propulsion, nuclear powered spacecraft - this is probably going to be a long skinny thing, because you’ll need a lot of radiators to reject the waste heat from the nuclear reactor. It’s going to have a set of thrusters, a fuel tank, and some guidance and navigation components. Depending on how you set this spacecraft up, we decided that if you put the reactor, which is heavy, and the fuel tank, which is heavy, down close to the asteroid - hanging from the thrusters - then you get more mass close to the asteroid, and that increases your gravitational pull as gravitational pull decreases rapidly as you increase the distance between the two masses. And it also helps stabilize your spacecraft and just helps you all around if you put your heavy components hanging down by the asteroid with the thrusters up at the top.

Fraser: Oh, I see, it would almost be if you had a ball at the end of a rope, hanging down with the heavy part - the reactor and all the fuel - hanging as close to the asteroid as you can, while all the thrusters are further up the rope pulling it away.

Love: That’s exactly right. Of course you need to tip your thrusters out away so the plume of hot gas coming out of them doesn’t hit the asteroid. It does no good trying to pull an asteroid closer to you with gravity and at the same time that you are pushing at it with your thruster plumes. So you need those outward so the plumes miss the asteroid and that will help improve your towing force.

Fraser: Now do you have any targets that you think might be a good victim of this kind of movement strategy?

Love: We were sort of developing the idea as a generic idea, and fly to anything. However, there’s Asteroid 99942 Apophis which is supposed to make a close pass of the Earth I think in 2029. And if that asteroid happens to pass through exactly the right point in space as it goes past the Earth, it has a chance to come back in 7-8 years and hit us, which would be bad. And that asteroid is an excellent target for this kind of a mission. If we can get to it before that first Earth flyby, that would line it up for impact the second time around. And the reason for that is that these flybys warp the path of the asteroid so that a tiny tiny change in the flight direction before the flyby gives a huge change in the flight direction after the flyby. So it’s like a bank shot in pool. A little tiny mistake on the first part, after the bounce, the mistake gets multiplied. So you could use a gravitational tractor that wasn’t nuclear powered and didn’t weight 20 tons. You could use a 1-ton, chemical-propelled gravity tractor to pull this asteroid just slightly off course before that Earth flyby so the asteroid is going no where near us.

Fraser: I see, if you have an asteroid that coming towards us 20 years out, you could move your big ion engine-powered tractor. How long would you need to have it spend next to the asteroid?

Love: About a year.

Fraser: But if it’s just about to do the flyby, you could give it a very small change and it would still kick it out of the bad orbit and into a good orbit.

Love: Right, you’re going to use that flyby of the Earth to multiply the tiny effect you put on the asteroid with your spacecraft before the flyby. And then after the flyby, the effect is much greater.

Fraser: So what’s the stage of your proposal now? What’s the future for it right now?

Love: Well it hard to know. Right now we’ve made a proposal, we’ve gotten the idea out there, and people are talking about it. My co-author, Ed Lu and I have written many scientific papers for publication, and none of them have received even a tenth as much attention as this one. So the idea’s out there, and we’ll see what happens. I think the debate will become much more pointed if we actually do discover an asteroid that’s on a collision path with the Earth. Then we’ll really need to get together and decide what we’re going to do about it.

Fraser: Well that’s my concern with the whole process of protecting the Earth from asteroids. There’s a lot of uncertainty in predicting when and where an asteroid is going to hit. The better you can mark the orbit, the better you can know if it’s going to be a risk. In many cases, if you’ve got these ones that are 30 years out, decision makers and lawmakers might say: well, let’s wait until we know better. And yet, the more you know better, the less chance you have of changing its orbit.

Love: Yes, that’s always true, and human nature plays into this a lot. Nobody’s every suffered an asteroid strike, so it’s hard to compare it to things that we have suffered, like tsunamis and hurricanes to take a couple of recent examples. The things that we know about and experience in a person’s lifetime are always easier to visualize and understand. And to get people to pay attention to something that seems kind of esoteric and science fictiony; is this real, or are people just making it up? I don’t know a good solution to that, but the fact that people are talking about the idea and thinking about it - and not just in the elevated circles of academia - all over the world, I think is a good sign. At least we’re thinking about the problem and how to solve it.

Inflatible habitat reaches orbit

Robert Bigelow’s dream of a thriving space tourism industry took a significant step forward today with the launch of the Genesis 1 experimental spacecraft. Bigelow Aerospace reported that the prototype habitat was successfully lofted into orbit atop a converted Russian inter-continental ballistic missile. Once in orbit, it extended its solar panels and began to inflate. The rocket launched at 6:53 pm Moscow Time, and the company released a series of statements over the course of the day reporting that everything’s going well.

Bigelow Aerospace is a space tourism company located in Las Vegas, Nevada. Its long-term goal is to develop a space-based hotel to give wealthy space tourists an orbital experience. Since space stations are so heavy and expensive to carry into orbit, Bigelow Aerospace has been pioneering the concept of inflatable habitats. These are carried into orbit in a compressed state and then inflated to provide a large volume of space for astronauts (and space tourists).

The company took its first step today with the launch of Genesis 1. When compressed, the habitat measures 5 metres (15 feet) in length and 1.9 metres (6.2 feet) in diameter. Once in orbit, it’s designed to inflate to roughly twice its compressed width.

It was carried into space on board an ISC Kosmotras Dnepr rocket - a Cold-War era ICBM - from the Yasny Launch Base.

By Wednesday evening, Bigelow Aerospace confirmedthat Genesis-1 had successfully expanded and deployed its solar arrays:

5:20 PST
Bigelow Aerospace has received confirmation from the Genesis I spacecraft that it has successfully expanded.

We have also confirmed that all of the solar arrays have been deployed.

4:15 PST
Bigelow Aerospace mission control has begun to acquire information from the Genesis I spacecraft. The ISC Kosmotras Dnepr rocket has flawlessly delivered the Genesis I into the target orbit of 550km altitude at 64 degrees inclination. The internal battery is reporting a full charge of 26 volts, which leads us to believe that the solar arrays have deployed.

The internal temperature of the spacecraft is reported to be 26 degrees Celsius and we have acquired the spacecraft’s Global Positioning System (GPS) signal that will enable us to track the ship in flight.

We have initiated communication with the ship’s onboard computers and expect to download more information over the next few hours.

The spacecraft is carrying staff photographs and memorabilia, as well as insects that will allow Bigelow to study how well the habitat holds up.

If everything goes well, it’ll stay in orbit for 5 years, giving engineers time to study its performance and to gather data for the next phases of the program. It’ll be exposed to years of solar radiation and cosmic rays, and should get peppered with orbital debris.

Bigelow expects to follow up the launch with Genesis-2; built to the size. It will have improvements based on the data gathered by Genesis-1, and could launch as early as late 2006 or 2007.

After the Genesis-class habitats will come the Galaxy class, and then finally the BA-330, which will contain 330 cubic metres of usable volume (the International Space Station has 425 cubic meters).

Squadrens of planet hunters could find life

The Hubble Space Telescope demonstrated that the best viewing is outside the Earth’s atmosphere. Over the years, a series of new telescopes have been lofted into space, and expanded this view into other wavelengths: Spitzer, Chandra, Compton, etc. Next up is the James Webb Space Telescope, with a mirror 6 times larger than Hubble, due for launch in 2013. But these observatories will pale in comparison when squadrons of space telescopes reach orbit. Both NASA and ESA are working on next generation space-based interferometers. They could answer one of the most fundamental questions of science: is there other life in the Universe?

One of the holy grails of astronomy is to find evidence of life outside the Earth, and one strategy is to find evidence of large quantities of oxygen in the atmosphere of another planet. Oxygen is extremely reactive, so large quantities in the atmosphere would mean some source - life - is continuously replenishing it.

In order to sense the atmosphere of another planet, you need an enormous telescope, with a view unobstructed by the Earth’s atmosphere, and some way to block the overpowering light from the planet’s star. The telescope would need to be huge, at least 30 metres across, and launched into space to get above the atmosphere. Since the cost of a single, huge telescope would be enormous, astronomers have developed a strategy where the light from several smaller telescopes could be combined. This called an interferometer.

Interferometers have made huge advances here on Earth. The twin Keck telescopes atop Mauna Kea in Hawaii are separated by a distance of 85 metres. Even though each telescope is only 10 metres across, their light can be combined to give them the resolving power of an 85 metre telescope. But even with this power, the Kecks and other Earth-based interferometers suffer from the distortions of the Earth’s atmosphere.

To make the best interferometers, you’ve got to get out into space. Both NASA and ESA are working on missions to launch a squadron medium-sized observatories. Connected together in a rigid structure, or flying in formation, they would add their light together to act as a much larger instrument. And without the obscuring effect of the Earth’s atmosphere, they would have unprecedented resolving power.

NASA’s space interferometer will be the Terrestrial Planet Finder. This would consist of 3-4 6.5+ metre telescopes to gather light. This light would then be funneled into another spacecraft that contains a special device - called a coronograph - capable of dimming the light from the central star. With such powerful resolution, and without the light from the central star, dimmer objects, such as Earth-sized planets should be visible.

Unfortunately, the mission has been put on hold indefinitely, as part of recent NASA science cutbacks. Let’s hope it doesn’t get completely canceled, and returns to service.

ESA has a space-based interferometer in development called Darwin. This would be a flotilla of three space telescopes, at least 3 metres in diameter, that could combine their light into a fourth telescope equipped with a coronograph as well. It would be able to dim the light from the central star by a factor of millions or even billions to allow faint objects to show up.

ESA and the European Southern Observatory have already developed a nulling interferometer as part of the Very Large Telescope array, which consists of four 8-metre telescopes and a collection of smaller telescopes. Darwin is scheduled for launch in 2015. Darwin will easily see Jupiters orbiting other stars, and should be able to pick out Earth-sized planets as well.

A recent paper by researchers from the Harvard-Smithsonian Center for Astrophysics and the European Space Agency outlined the different telescope configurations that could be used for Darwin or the Terrestrial Planet Finder.

The commet with the broken heart

Comet P73/Schwassmann-Wachmann 3 (SW 3) is a body with a very tormented past. This comet revolves around the Sun in about 5.4 years, in a very elongated orbit that brings it from inwards the Earth's orbit to the neighbourhood of giant planet Jupiter. In 1995, when it was coming 'close' to the Earth, it underwent a dramatic and completely unexpected, thousand-fold brightening. Observations in 1996, with ESO's New Technology Telescope and 3.6-m telescope, at La Silla, showed that this was due to the fact that the comet had split into three distinct pieces. Later, in December 1996, two more fragments were discovered. At the last comeback, in 2001, of these five fragments only three were still seen, the fragments C (the largest one), B and E. No new fragmentations happened during this approach, apparently.
Things were different this time, when the comet moved again towards its closest approach to the Sun – and to the Earth. Early in March, seven fragments were observed, the brightest (fragment C) being of magnitude 12, i.e. 250 fainter than what the unaided can see, while fragment B was 10 times fainter still. In the course of March, 6 new fragments were seen.

Early in April, fragment B went into outburst, brightening by a factor 10 and on 7 April, six new fragments were discovered, confirming the high degree of fragmentation of the comet. On 12 April, fragment B was as bright as the main fragment C, with a magnitude around 9 (16 times fainter than what a keen observer can see with unaided eyes). Fragment B seems to have fragmented again, bringing the total of fragments close to 40, some being most probably very small, boulder-sized objects with irregular and short-lived activity.

The new observations reveal that this new small fragment has split again! The image clearly reveals that below the main B fragment, there is a small fragment that is divided into two and a careful analysis reveals five more tiny fragments almost aligned. Thus, this image alone shows at least 7 fragments. The comet has produced a whole set of mini-comets!

Will the process continue? Will more and more fragments form and will the comet finally disintegrate? How many new fragments will have appeared before the comet reaches its closest approach to the Sun, around 7 June, and how bright will they be when the comet will be the closest to the Earth, on 11 to 14 May?

Fragment C of the comet should be the closest to Earth on 11 May, when it will be about 12 million km away, while fragment B will come as 'close' as 10 million km from Earth on 14 May. Although this is the closest a comet ever approached Earth in more than twenty years – even Comet Hyakutake's smallest distance was 15 million km - this is still 26 times the distance between the Earth and the Moon and therefore does not pose any threat to our planet.

If nothing else happens, at the time of closest approach, fragment B will be just visible with unaided eye by experienced observers. It should be an easy target however to observe with binoculars. If we are lucky, however, fragment B presents another outburst, becoming a magnificent sight in the night sky. On the other hand, it could just as well fade away into oblivion. But then, the main fragment C should still be visible, even possibly with the unaided eye.

ESO telescopes will observe the comet in the greatest detail at the end of May, when it is best observed from Chile and is brighter. These observations will obtain invaluable information, especially as the fragmentation process is revealing all the pristine material buried below the crust of the comet. As such, these observations will prove an ideal complement to the most comprehensive observation campaign made with ESO telescopes of Comet Tempel 1 when it was being bombarded by the Deep Impact spacecraft, on 4 July 2005.

More information

About 30 comets have been observed to split in historical times and this process is almost always accompanied by a significant brightening. For instance, the nucleus of comet Shoemaker-Levy 9 broke up into at least 21 individual pieces when it passed very close to Jupiter on July 8, 1992; this was the reason that it became bright enough to be detected some eight months later. In the case of SW-3, the opening of rifts and the subsequent splitting took place far from any planet and must in some way have been caused by increased solar heating. It is possible that major cracks and rifts opened in the irregularly shaped icy nucleus already before perihelion as the surface temperature began to increase. Completely ''fresh'' cometary material was thereby exposed to the solar light and the evaporation rate increased quickly, releasing more gas and dust into space. In the course of this process, the rifts gradually widened until the definitive breakage occurred somewhat later.

Comet Schwassmann-Wachmann 3 was discovered on May 2, 1930, on a photographic plate obtained at the Hamburg Observatory (Germany) by two astronomers at this institution, Arnold Schwassmann and Arthur Arno Wachmann. The subsequent observations showed that the comet moved in an elliptical orbit with a revolution period of somewhat more than 5 years. Great efforts were expended to observe the comet during the next returns, but it was not recovered until nearly 50 years and eight revolutions later, when its faint image was found of a plate obtained in August 1979 with a telescope at the Perth Observatory in Western Australia. It was missed in 1984, but was sighted again in 1989 and since then, it is observed at each close approach. Thus this comet has only been observed during six out of fifteen approaches since 1930. While this may be partly due to a less advantageous location in the sky at some returns, it is also a strong indication that the comet behaves unpredictably and must have a quite variable brightness. Orbital calculations have shown that it was inserted into the present, short-period orbit by the strong gravitational pull of Jupiter during several, relatively close encounters with this giant planet. For instance, it passed Jupiter at a distance of about 30 million kilometres in 1882 and 1894, and again at 40 million kilometres in 1965. SW-3 belongs to the so-called ''Jupiter family'' of comets.

The observations were done with the FORS1 multi-mode instrument on Kueyen, the second 8.2-m Unit Telescope of the Very Large Telescope located at Cerro Paranal (Chile). The fragment was observed in four bands (B, V, R, and I) for a total of 30 minutes by Emmanuel Jehin, Olivier Hainaut, Michelle Doherty, and Christian Herrera, all from ESO. The astronomers had the telescope track the comet, which explains why the stars appear as trails of coloured dots, each colour corresponding to the order in which the observations were done in the various filters. At the time of the observations, the comet was 26.6 million km away from the Earth, in the constellation Corona Borealis. The seeing was 1.5" as the comet was observed when it was rather low on the horizon as seen from Paranal. The final processing of the image was done by Olivia Blanchemain and Haennes Heyer (ESO).

More observations of the comet are foreseen from 20 till 30 May, with ESO telescopes on the three sites of La Silla (NTT, 3.6m), Paranal (VLT) and Chajnantor (APEX). These observations will study aspects as diverse as the presence of organics in the dust, the composition of this dust, the structure of the coma, and the presence of deuterated water.

Unlikely wormholes

Wormholes are a mainstay in science fiction, providing our heroes with a quick and easy way to instantly travel around the Universe. Enter a wormhole near the Earth and you come out on the other side of the galaxy. Even though science fiction made them popular, wormholes had their origins in science - distorting spacetime like this was theoretically possible. But according to Dr. Stephen Hsu from the University of Oregon building a wormhole is probably impossible.

Fraser Cain: Now, I’ve watched my share of Star Trek episodes. How well has this prepared me for the actual scientific understanding of a wormhole?

Dr. Stephen Hsu: In Star Trek they don’t really use wormholes, but maybe the best treatment in sci-fi for wormholes was in the movie Contact, which is based on a book by Carl Sagan. And actually historically, when Sagan was writing the novel - Sagan was an astronomy professor - he contacted an expert in General Relativity, a guy named Kip Thorne, at Caltech, and wanted to make sure that the way wormholes were treated in Contact was actually as close to being scientifically correct as possible. And that actually stimulated Thorne to do a lot of research on wormholes. Our work is actually an extension of things that he did.

Fraser: So if you wanted to build a wormhole, theoretically, what would you do?

Hsu: You need to have a very weird or exotic kind of matter and that matter has to have highly negative pressure. It turns out that to stabilize the throat or the tube of the wormhole you need very strange matter and our work has to do with how possible that kind of matter would be in models of particle physics.

Fraser: Let’s say you build a tear in spacetime and you fill it with exotic matter to keep it open, and then you could move the two end points of the wormhole around the Universe and they would connect both in space and in time.

Hsu: But in some science fiction stories they postulate that there are just some wormholes left over from the Big Bang, and we would just discover one and start using it. But the constructive model is that humans, or some alien civilization, actually build their own, and in that case the two ends of the wormhole probably are pretty close together at the beginning but then you pull them apart.

Fraser: Where has your research led you to look at wormholes?

Hsu: We were studying fundamental constraints on something called the “equation of state of matter” - what properties, like pressure or energy density can matter have. We found some very strong constraints, and it turns out those constraints are very negative for the possibility of building a wormhole.

Fraser: What effect will they have on the wormhole?

Hsu: To get the very weird exotic matter that I mentioned before with very negative pressure, it turns out the equations show that when you force the pressure to be that negative, there always some unstable mode in the matter, which means that if you were to bump your apparatus, you might find the exotic matter - which is stabilizing the wormhole - just collapses into a bunch of photos or something.

Fraser: Is it a matter of not bumping your apparatus, or is it theoretically impossible to reach a stable point?

Hsu: I would say it’s theoretically impossible to build classical matter which is stable and can stabilize a wormhole. You might ask, well maybe I’ll just avoid bumping the thing, but if you were to send a person through the wormhole, that itself would provide a bump and would very likely cause the whole thing to fall apart.

Fraser: Let’s say you didn’t want to send people, you just wanted some way of sending information - talking back in time.

Hsu: That’s not excluded. It turns out the constraints we derive have to do with matter in which quantum effects are relatively small. If you have matter in which quantum effects are very big, then you could still have a stable wormhole. The wormhole itself would be fuzzy in a quantum way. The tube of the wormhole would be fluctuating like a quantum state. Now, that doesn’t prevent you from sending a message back in time; you might have to try to send the message many times to get it to go where you want it to go. But, perhaps you could still send a message. Sending a person might be dangerous if the wormhole is fluctuating because the person might end up in the wrong place or the wrong time.

Fraser: I’d heard estimations that building a wormhole would require more energy than the entire Universe. Have you got some kind of calculations to that effect?

Hsu: Our calculations don’t necessarily show that. It does take a tremendous amount of energy density to create a wormhole which is big enough for a human to fit through. But, usually considering this kind of problem, you assume that whatever civilization is trying to do this has arbitrarily advanced technology. What we’re trying to understand is whether there’s a limitation not coming from technology but really coming from the fundamental laws of physics.

Fraser: And where will your research lead you from this point on? Is there something that you’re still a little unsure about?

Hsu: Our result mainly has to deal with the classical wormholes, or wormholes whose spacetime is not very quantum mechanical, and we’re still interested to see if we can extend our results to cover wormholes in which spacetime is fuzzy.

Fraser: There’s some new work on dark energy where they’re saying that the dark energy effect seems to be happening in the Universe, that it’s accelerating. Either there’s a new form of energy that’s not been seen before, or maybe it’s a breakdown in Einstein’s theories at a large level. If some of that work starts to show that maybe Einstein’s relativity isn’t able to explain it at the larger level, will it have an implication on the classical understanding of what a wormhole is?

Hsu: In the context of dark energy, since it’s something that affects the large scale structure of the Universe, the behaviour of the Universe on length scales of megaparsecs, it’s always possible that General Relativity as a theory is modified at very large distances and because we haven’t been able to test it on those distances. So it’s always possible that conclusions you get from Relativity are just not applicable. In our case, the length scale over which we’re using General Relativity is on the size of a human. So, it would be somewhat surprising if General Relativity were to break down already at those length scales, though it’s possible.

Fraser: So it’s more on the small side what you’re looking at. It still explains things quite nicely at this scale.

Hsu: Right, there are stronger experimental tests of General Relativity, or at least Newtonian gravity, on length scales of metres than on megaparsecs. So we’re a little more confident that the mathematical formulation of gravity that we’re using is correct.

Fraser: If I wanted to get across the Universe quite rapidly, I should look perhaps to the warp drive instead, or maybe just plain old moving in regular space.

Hsu: I’m a huge science fiction fan, and have been since I was a kid, but as a scientist, I’d have to say it’s looking like our Universe seems to not be constructed in a very convenient way for humans to get from star to star. And the sci-fi which we end up staying close to our Sun, but we do amazing things with bioengineering or information technology or A.I. seem more likely to be realizable with our physical laws, than Star Trek.