Space

A stunning sighting around a nearby star offers a glimpse of our own solar system billions of years ago

With some 2,000 planets now known to orbit stars beyond the Sun and thousands more in the can waiting for confirmation, the once-exotic term “exoplanet” is so commonplace it requires no definition for many people. The term “exocomet,” by contrast, is a bit more obscure. Astronomers have known for years that comets orbit other stars—in particular, the relatively nearby star β Pictoris, which lies about 63 light-years from Earth, in the constellation Pictor.

But a new paper in Nature is more than a little mindblowing nevertheless. A team of astronomers is reporting the detection of nearly 500 individual comets that passed in front of β Pictoris between 2003 and 2011. And that’s not even remotely a complete sample. “We had only a couple of nights of observing time per year,” says lead author Flavien Kiefer, now at the University of Tel Aviv. “If we’d been looking constantly, we would have seen many thousands.”

There are a lot of reasons all of this seems slightly crazy. To start with, there’s the notion that you can see something as relatively tiny as a comet from nearly 300 trillion miles away. And in fact, you can’t. But when comets approach the heat of a star, some of their substance boils off to form an enormous cloud of gas and dust, and sometimes a tail as well. And when that cloud moves in front of the star, it distorts the starlight in ways you can see with sufficiently powerful instruments.

In this case, the scientists used the High-Accuracy Radial-Velocity Planet Searcher (HARPS), located at the European Southern Observatory, in Chile. As the name implies, it was designed to find planets—and it has. HARPS does so by looking for subtle changes in starlight created as the star wobbles in response to an orbiting planet’s gravitational tug. The distortions caused by an intervening comet are different, but HARPS can find those too.

The technique isn’t easy, says Aki Roberge, an astronomer with NASA’s Goddard Spaceflight Center, in Maryland who has studied β Pictoris as well, and who wrote a commentary in Nature on the new results, but it clearly works. “We always knew this would be a powerful technique,” she says, “They’ve done a really amazing job.”

The sheer number of comets also seems unlikely at first, until you realize that β Pictoris is extremely young—about 22 million years old compared with the Sun’s 4.6 billion. If we could see our own Solar System at that age, it wouldn’t look all that much different: a thick disk of gas and dust surrounding the central star, with planets just assembling themselves out of chunks of rock and ice. In fact, β Pictoris has at least one young planet already, but there’s still an awful lot of debris flying around.

And that’s what makes this discovery so important, not just as a technical tour de force, but also scientifically. “We can now begin to study a newly forming solar system in detail,” says Kiefer, “and perhaps get an understanding of how our own Solar System was born.”

It probably won’t be the last chance to do so, either. Roberge has her eye on a star called 49 Ceti, which she says is very similar to β Pic in many ways. Kiefer, meanwhile, is conducting preliminary surveys of no fewer than 30 promising stars. With powerful instruments like HARPS on the case, the word “exocomet” could become a lot more familiar before long.

A shower of 20 meteors-per-hour began Tuesday at 8 p.m. ET

Slooh Community Observatory is tracked the Comet Siding Spring, which skimmed past Mars midday Sunday at an unprecedented proximity, in a second live stream that played on Sunday evening

Hot off the presses

A detailed new image of the sun is providing NASA with information about the sun’s atmosphere.

The photos, taken by NASA’s Interface Region Imaging Spectograph (IRIS), help explain how the sun’s atmosphere is hotter than its surface, what causes solar wind, and what mechanisms accelerate particles that power solar flares, NASA said in a release.

Some of the more noteworthy findings identified heat pockets of 200,000 degrees Fahrenheit that exist in the solar atmosphere, which scientists refer to as “heat bombs.”

Just because you've reached the edge of the solar system doesn't mean you've run out of worlds to visit. NASA's New Horizons spacecraft is set to make that point

When it blasted off for Pluto back in 2006, NASA’s New Horizons probe was poised to achieve several major milestones at once. It would be visiting the last planet still unexplored at close quarters (and yes, Pluto was still a planet when the mission began). It would also be the first mission to explore a class of planet vastly different from the Solar System’s rocky inner worlds, and also from the gas giants further out. Even after it was demoted to “dwarf planet,” Pluto represented the nearest of the ice worlds that lurk at the edges of the Sun’s influence. Understanding their true nature called for a close encounter—and New Horizons was designed to provide it.

But once the probe whips past Pluto and its moon Charon next July, it will still have functioning instruments and fuel to burn. And now, says NASA, it may have someplace to go and another scientific milestone to achieve. An intensive search with the Hubble Space Telescope has revealed three icy bodies more or less along New Horizons’ post-Pluto path and a billion miles (1.6 billion km) further out. Sometime in 2018 or 2019 the probe could be getting a close look at one of these so-called Kuiper Belt Objects (KBO)—a primordial remnant left from the very earliest days of the Solar System.

“The objects Hubble has identified are much smaller than Pluto,” says Alan Stern, a planetary scientist with the Southwest Research Institute, in Boulder, CO, and New Horizons’ Principal Investigator. “They’re the building blocks Pluto was made of.”

Hubble got this discovery in just under the wire. The rocket burn that will readjust New Horizons trajectory to intercept one of the KBO’s won’t happen until after the Pluto encounter. But in order to calculate that complicated maneuver, ground controllers need to know precisely how the KBO’s themselves are moving. “We need to make a series of observations,” says Stern, “to connect the dots.” And if they didn’t have a first set of observations by now, they wouldn’t have enough dots to connect.

In one sense, researchers have already gotten a close look at a KBO: Europe’s Rosetta probe went into orbit around a comet in August, with plans to set down a lander on its surface on November 9—and a comet is essentially a KBO that has wandered into the inner Solar System.

But that means it’s been exposed to the Sun’s heat, so unlike its cousins further out, it’s not truly primordial. Beyond that, these three new objects are between 15 and 35 miles (24 and 56 km) across. That’s about ten times bigger and a thousand times more massive than Rosetta’s comet, while still a thousand times less massive than Pluto. Whichever KBO New Horizons visits will therefore fill in a huge gap, helping scientists understand how Pluto itself formed.

It will, that is, if NASA approves the extended mission, funding the probe for longer than was originally planned. That kind of second act is not unusual—Hubble itself has had its mission extended several times, and so did the Spirit and Opportunity rovers on Mars. It’s not guaranteed, though. “We have to make a proposal,” says Stern, “but at least we now have something concrete to propose.”

Even if the mission is green-lit and that second encounter comes off, New Horizons still might not be done. “We’re going to keep looking for other KBO’s even farther out,” says Stern. If they’re close enough to New Horizons’ path, and if there’s enough fuel left for another trajectory adjustment, next July’s Pluto flyby could be just the start of an extraordinary series of close encounters with the most remote colonies in the Sun’s cosmic empire.

Mission Selfie: Accomplished

Europe’s Rosetta spacecraft took a selfie published Tuesday that is, quite literally, out of this world.

Rosetta’s mission is to land on comet 67P/Churyumov–Gerasimenko. The spacecraft is very close to its target, enough that the comet appears in the background of this image only 16km away.

Rosetta, dubbed Europe’s “comet chaser,” went into space in 2004. It had many things on its to-do list, including eventually landing on 67P. But for now, Mission Selfie accomplished.

A new analysis of Mars One's plans to colonize the Red Planet finds that the explorers would begin dying within 68 days of touching down

Hear that? That’s the sound of 200,000 reservations being reconsidered. Two hundred thousand is the announced number of intrepid folks who signed up last year for the chance to be among the first Earthlings to colonize Mars, with flights beginning as early as 2024. The catch: the trips will be one way, as in no return ticket, as in farewell friends, family, charbroiled steaks and vodka martinis, to say nothing of such everyday luxuries as modern hospitals and, you know, breathable air.

But the settlers in Jamestown weren’t exactly volunteering for a weekend in Aspen either, and in both cases, the compensations—being the first people on a distant shore—seemed attractive enough. Now, however, the Mars plan seems to have run into a teensy snag. According to a new analysis by a team of grad students at MIT, the new arrivals would begin dying within just 68 days of touching down.

The organizers of the burn-your-boats expedition is a group called Mars One, headed by Bas Lansdorp, a Dutch entrepreneur and mechanical engineer. As Lansdorp sees things, habitat modules and other hardware would be sent to the Red Planet in advance of any astronauts, who would arrive in four-person crews at two-year intervals—when Mars and Earth make their closest approach, which holds the outbound journey to a brief (relatively speaking) eight months. The crew-selection process would be part of (yes) a sponsored reality show, which would ensure a steady flow of cash—and since the settlers would grow their own food onsite, there would be little to carry along with them. All that would keep the overall cost of the project to a shoestring (relative again) $6 billion.

So what could go wrong? That’s what the four MIT students set out to find out, and the short answer is: a lot.

The biggest problem, the students discovered, concerns that business of breathable air. One of the things that’s always made Earth such a niftily habitable place to live is that what animals exhale, plants inhale, and vice versa. Since the Martian astronauts and their crops would be living and respiring in the same enclosed habitats, a perfect closed loop should result in which we provide them all the carbon dioxide they need and they return the favor with oxygen.

Only it doesn’t, the MIT students found. The problem begins with the lettuce and the wheat, both of which are considered essential crops. As lettuce matures, peaking about 30 days after planting, it pushes the 02 level past what’s known as .3 molar fractions, which, whatever it means, doesn’t sound terribly dangerous — except it’s also the point at which the threat of fire rises to unacceptable levels. That risk begins to tail off as the crop is harvested and eaten, but it explodes upward again, far past the .3 level, at 68 days when the far gassier wheat matures.

A simple answer would be simply to vent a little of the excess O2 out, which actually could work, except the venting apparatus is not able to distinguish one gas from another. That means that nitrogen—which would, as on Earth, make up the majority of the astronauts’ atmosphere—would be lost too. That, in turn, would lower the internal pressure to unsurvivable levels—and that’s what gets your 68-day doomsday clock ticking.

There is some question too about whether the hardware that Mars One is counting on would even be ready for prime time. The mission planners make much of the fact that a lot of what they’re planning to use on Mars has already been proven aboard the International Space Station (ISS), which is true enough. But that hardware is built to operate in microgravity—effectively zero g—while Mars’s gravity is nearly 40% of Earth’s. So a mechanical component that would weigh 10 lbs. on Earth can be designed with little concern about certain kinds of wear since it would weigh 0 lbs. in orbit. But on Mars it would be 4 lbs., and that can make all the difference.

“The introduction of a partial gravity environment,” the grad students write, “will inevitably lead to different [environmental] technologies.”

For that and other reasons, technical breakdowns are a certainty. The need for replacement parts is factored into Mars One’s plans, but probably not in the way that they should be. According to the MIT team, over the course of 130 months, spare parts alone would gobble up 62% of the payload space on resupply missions, making it harder to get such essentials as seeds, clothes and medicine—to say nothing of other crew members—launched on schedule.

Then too, there is the question of habitat crowding. It’s easy to keep people alive if you feed them, say, a single calorie-dense food product every day. But energy bars forever means quickly losing your marbles, which is why Mars One plans for a variety of crops—just not a big enough variety. “Given that the crop selection will significantly influence the wellbeing of the crew for the entirety of their lives after reaching Mars,” the authors write, “we opt for crop variety over minimizing growth area.”

Then there is the question of cost—there’s not a space program in history whose initial price tag wasn’t badly lowballed—to say nothing of maintaining that biennial launch schedule, to say nothing of the cabin fever that could soon enough set the settlers at one another’s throats. Jamestown may not have been a picnic, but when things got to be too much you could always go for a walk by the creek.

No creeks here, nor much of anything else either. Human beings may indeed colonize Mars one day, and it’s a very worthy goal. But as with any other kind of travel, the best part of going is often coming home.

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