TIME space

Voyager 1 Surfs a Cosmic Tsunami

Wow, Voyager: 12 billion miles from home and still very much in the game
Wow, Voyager: 12 billion miles from home and still very much in the game NASA/JPL

Earth's only Interstellar spacecraft is rocked by a storm from the sun

Planetary scientists have pretty much stopped haggling over whether Voyager 1, the space probe launched in 1977 to explore Jupiter and Saturn, has finally entered interstellar space. The tough little ship is still going strong, but there isn’t exactly a signpost that marks the heliopause—the place where particles streaming from the Sun bang into the thin gas that lies between the stars. As a result, there’s been some confusion about when the spacecraft actually crossed that invisible boundary—though there’s no confusion over the fact that it did. (There’s no confusion either about whether it’s left the Solar System: despite last year’s breathless headlines, it hasn’t. Comets in the Oort Cloud, which are definitely under the Sun’s gravitational influence, are much farther out than the heliopause.)

But the fact that Voyager 1 is now firmly in interstellar space is evident just by the change in its surroundings, says Don Gurnett, of the University of Iowa, whose plasma wave instrument aboard the probe is the final arbiter. “It’s extremely quiet out there,” Gurnett says. “The magnetic fields are constant, the flux of cosmic rays is constant”—a sharp contrast to the turmoil of the so-called termination shock, where particles racing outward at a million m.p.h. (1.6 million k/h) slam into the relatively stationary particles that make up the interstellar medium.

But the comparative quiet of distant space does not mean there’s nothing going on out there. At this very moment, in fact, as Gurnett explained at a talk at the American Geophysical Union’s annual meeting in San Francisco this week, the sparse interstellar gas is reeling from a powerful blast of solar particles that smashed into it last February. The eruption began its life as a coronal mass ejection or CME, a huge burst of hot plasma fired into space during a solar storm. When they hit the Earth, CMEs can disrupt electronic communications and even cause blackouts.

Their impact further away is much greater, causing a kind of cosmic tsunami—huge pressure waves that make the interstellar gas vibrate like a ringing bell. Indeed, a recording the spacecraft made and NASA released reveals that the phenomenon even sounds like a bell. “This shows us how much influence the Sun can have on the surrounding area,” says Caltech physicist Ed Stone, who has been the Voyager project scientist since 1972, “and it’s very likely to be the same with other stars.”

Voyager detected its first cosmic tsunami back in the 1990’s when the impact of a CME colliding with the heliopause created a blast of radio waves. They’re too faint to be picked up from Earth, says Stone. “You need to be out by Saturn, at least, to detect them.” By 2012, the spacecraft was close enough to the heliopause to experience a later tsunami directly, recording a steep increase in the density of the gas it was flying through. It felt another in 2013, and the probe is now in the midst of its third, which was still going nine months later—a period during which Voyager 1 traveled a quarter of a billion miles (.4 billion km). No one knows how far into space the tsunami will travel before it fades out, says Gurnett. “I’m guessing it could be another hundred astronomical units or more.”

That, by the way, is a whole lot. An astronomical unit is the equivalent of the distance between the Earth and the sun—or 93 million mi. (150 million km). A hundred of those is 9.3 billion miles—or 15 billion km. Voyager 1 is currently at 130 A.U., or about 12 billion miles; it will have to reach 21.3 billion just to catch up with the outer reach of the tsunami—a journey that will take decades.

Stone, Gurnett and the other Voyager scientists won’t have to wait that long for another big event, however. The Voyager 2 probe, which lagged behind its sister ship so it could take a look at Uranus and Neptune, is currently at 109 A.U. from the Sun, and approaching its own rendezvous with the heliopause. “We’re hoping it will happen in the next couple of years,” says Stone.

If it’s hard to imagine what it’s like for Stone to watch the Voyager probes continue to make discoveries more than four decades after he took over the project, he offers a single, simple word of explanation: “Wonderful.”

TIME space

Odds For Life on Mars Tick Up—a Little

High-tide: layering in a Mars rock photographed by Curiosity suggests the movement of long-ago water
High-tide: layering in a Mars rock photographed by Curiosity suggests the movement of long-ago water NASA/JPL

New findings about both methane and water boost the chances for biology

September of 2013 was a bad time for those who hope there’s life on Mars. We’ve had evidence for decades that water flowed freely across the surface of the Red Planet billions of years ago, and that evidence has only gotten stronger and stronger the closer we look. Not only was there potentially life-giving water back then: Mars also had the right kind of geology to support mineral-eating microbes. And while all of that was in the distant past, the detection of methane in the Martian atmosphere by Earth-based telescopes and Mars orbiters raised hopes that bacteria might still be thriving below the surface—not unreasonable, both because all manner of Earthly critters do perfectly well below-ground and because the vast majority of methane in our own atmosphere results from biological activity. Mars’s methane might come from a similar source.

But when the Curiosity rover sniffed the Martian air directly last year, it smelled…nothing. At most, there were just three parts per billion (ppb) of methane wafting around, and possibly much less than that. “We kind of thought we’d closed that chapter,” says Christopher Webster of the Jet Propulsion Laboratory, lead scientist for the instrument that did the sniffing. “A lot of people were very disappointed.”

Not any more, though. Just weeks after that dismal reading, Curiosity’s Tunable Laser Spectrometer (TLS) picked up a whiff of methane at a concentration of 5.5 parts per billion. “It took us by surprise,” says Webster, and over the next two months, he says, “every time we looked there was methane. Indeed, the concentrations even rose, to an average of 7.2 ppb over that period, he and his colleagues report in a new paper in Science.

And then, six weeks later, the methane was gone, and hasn’t been sniffed since. “It’s a fascinating episodic increase,” Webster says.

What he and his colleagues can’t say is where the methane is coming from. Because it’s transient, they think it’s probably from a fairly local source. But whether it’s biological or geological in origin, they don’t know. It’s wise to be cautious, however, says Christopher Chyba, a professor of astrophysics and international affairs at Princeton. “Hopes for biology on Mars have had a way of disappearing once Martian chemistry has been better understood. But figuring out what’s responsible for the methane is clearly a key astrobiological objective—whatever the answer turns out to be.”

That’s not the only important Mars-related paper in Science this week, either. Another, also based on Curiosity observations, concerns Mars’s long-lost surface water, and one of the most important points is that there’s a lot more of it left than most people realize—”enough,” says Jet Propulsion Laboratory scientist Paul Mahaffy, lead author of the paper, “to cover the surface to a depth of 50 meters [about 165 ft].” That doesn’t mean it’s accessible: it’s nearly all locked up in ice at the planet’s poles, but some is also entrained in the clay Curiosity dug into when it was prowling the Yellowknife Bay area of Gale Crater.

Some of that water, says Mahaffy, is tightly chemically bound to the clay and is not a big player in Mars’s modern environment. Some is not quite so locked down and has been interacting with the tenuous Martian atmosphere for the past three billion years. The hydrogen in Martian water, as in Earthly water, may contain both a single proton and a single electron, or a proton and electron plus a neutron—so-called heavy hydrogen, or deuterium. As the Martian atmosphere has thinned over the eons, the ratio of hydrogen to deuterium in the water has gradually been dropping, as the lighter version escapes more easily into space. Since the modern water is twice as rich in deuterium as the water from billions of years ago, that suggests that there was about twice as much surface water in total at the earlier time, but its hydrogen residue has vanished.

“That’s a fair bit of water,” says Mahaffy, “but it’s a lower limit. There could be much more beneath the surface today that we haven’t seen. It was a really interesting time. There were a lot of aqueous processes going on, and a lot of flowing water.”

Where there is (or was) water, there could be (or could have been) life. For Mars enthusiasts, that’s why December of 2014 is a lot better than September of 2013.

TIME dinosaurs

Here’s What Really Killed the Dinosaurs

dinosaur volcano
Elena Kalistratova—Getty Images

It wasn't just an asteroid

At the start of the 1980s, the question of what forced dinosaurs and huge numbers of other creatures to become extinct 65 million years ago was still a mystery. By the decade’s end, that mystery was solved: a comet or asteroid had slammed into Earth, throwing so much sun-blocking dust into the air that the planet plunged into a deep-freeze. The discovery of a massive impact crater off the coast of Mexico, of just the right age, pretty much sealed the deal in most scientists’ minds.

But a second global-scale catastrophe was happening at much the same time: a series of ongoing volcanic eruptions that dwarf anything humans have ever seen. They were so unimaginably powerful that they left nearly 200,000 square miles (518,000 sq. km) of what’s now India buried in volcanic basalt up to a mile and a half thick. And the gases and particulate matter spewed out by those eruptions, argue at least some scientists, could have played a big role in the dinosaurs’ doom as well.

How big a role, however, depends on exactly when the eruptions began and how long they lasted, and a new report in Science goes a long way toward answering that question. “We can now say with confidence,” says Blair Schoene, a Princeton geologist and lead author of the paper, “that the eruptions started 250,000 years before the extinction event, and lasted for a total of 750,000 years.” And that, he says, strengthens the idea that the eruptions could have contributed to the mass extinction of multiple species.

Schoene and his co-authors don’t claim volcanoes alone wiped out the dinosaurs; only that they changed the climate enough to put ecosystems under stress, setting them up for the final blow. “We don’t know the exact mechanism,” he admits. Volcanoes emit carbon dioxide, which could have triggered an intense burst of global warming, but they also emit sulfur dioxide, which could have caused global cooling. “What we do know,” Schoene says, “is that earlier mass extinctions were caused by volcanic eruptions alone.” The new dates, he and his co-authors believe, will help scientists understand what role these volcanoes played in the dinosaurs’ demise.

If there was such a role, that is, and despite this new analysis, plenty of paleontologists still doubt it seriously. The dating of the eruptions, based on widely accepted uranium-lead measurement techniques, is not an issue, says Brian Huber, of the Smithsonian Institution. “That part of the science is great,” he says. “It moves things forward.”

But the link between eruptions and the disappearance of species, he thinks, is invalid. “The case of the mass extinctions being caused by an impact is overwhelming,” says Huber. “One of the wonderful things about these arguments is that they’ve forced us to look really carefully at the fossil evidence, on land and at sea. We’ve accumulated a really detailed data set.”

And those data, Huber says, make it clear that the extinction rate for the 250,000 years leading up to the asteroid impact wasn’t especially large. Then, at the time of the impact: whammo. The idea that volcanoes played a significant role in this extinction event keeps coming up every so often, and in Huber’s view, “the argument has gotten very tiresome. I no longer feel the need to put any energy into it. It’s from a minority arguing against overwhelming evidence.”

For onlookers, that might seem harsh—not to mention overconfident. Sometimes a vocal scientific minority turns out to be right in its challenge to the scientific mainstream, as when Alfred Wegener argued, to much ridicule, that continents move around the Earth. And sometimes it’s dead wrong—Sir Fred Hoyle’s futile campaign against the Big Bang theory, for example.

In both cases, however, it was the accumulation of evidence that ultimately vindicated one argument and torpedoed the other. So far, the volcanic impact people have most of the torpedoes on their side.

Read next: Newly Discovered Fossils Reveal Goofy-Looking Dinosaur

TIME space

You Can Quit Thanking Comets for Your Water

Comet 67P: Does this thing look like it could quench your thirst?
Comet 67P: Does this thing look like it could quench your thirst? ESA

A new finding from the Rosetta spacecraft upsets a longstanding theory

There was no shortage of drama when the European Space Agency’s probe Philae set down on a comet last month—the first such landing in history. First Philae bounced, then it bounced again, ending up with one of its three legs sticking up in the air, and in the shadow of a cliff that prevented its solar panels from recharging its batteries. For two days, the probe hurried to complete whatever science it could….and then everything went black.

But that hardly spelled the end of the mission. Philae’s mother ship, Rosetta, has continued to orbit comet 67P/Churyumov–Gerasimenko, as it’s been doing since August, taking measurements and images of unprecedented quality. And with nearly a year of close-up observations to go, Rosetta has already come up with one result, described in a new paper in Science, that chief scientist Matt Taylor, of the European Space Agency, labeled “fantastic”: Earth’s oceans, the scientists have concluded, were evidently not created by impacts from comets rich with water ice, despite earlier evidence to the contrary. “We have to conclude instead,” said lead author Kathrin Altwegg, a planetary scientist at the University of Bern, at a press conference, “that the water came from asteroids.”

That’s a big reversal from what scientists were thinking just a few years ago. Back in 2011, the European Herschel space telescope took a hard look at Comet Hartley 2 and determined that its own cache of water, detected as vapor boiling away as Hartley approached the Sun, had a chemical composition very similar to what we see on Earth. It’s all H2O, but some of the H is a rare form of hydrogen known as deuterium, whose atoms carry not just a proton like the ordinary stuff, but a neutron as well. Water molecules made with deuterium are known as “heavy water,” and about three in a thousand water molecules on Earth’s surface are the heavy kind.

Measurements of Halley’s Comet back in the mid-80’s showed a deuterium-to-hydrogen ratio about twice that high, which argued against the idea that comets delivered water to a bone-dry Earth early in the Solar System’s history. But Halley’s came from the Oort Cloud, a spherical swarm of proto-comets orbiting at the far edges of the Solar System. Hartley 2 came from the Kuiper Belt of comets, which lies just beyond Neptune–not exactly nearby, but a whole lot closer. Given what Herschel found at Hartley 2, it appeared that Kuiper belt comets are chemically different from those that hail from the Oort cloud. If so, our water could have cometary origins after all.

The new results from Rosetta say no: Comet 67P, which also comes from the Kuiper belt, has an even greater proportion of heavy water than Halley’s and other Oort cloud objects. Even if significant numbers of comets do have Earthlike water, some clearly don’t—and even a relative few would have made Earth’s proportion of heavy water higher than it is. It’s arguable that 67P is pretty much unique among its Kuiper Belt brethren in having so much deuterium. “That’s not impossible,” said Altwegg dubiously “but….”

If comets didn’t bring us water, and if the Earth was too hot in its youth to hold on to what surface water it might have started out with, there’s still one plausible water carrier. “Today, said Taylor at the press conference, “we know asteroids have very little water, but that was probably not always the case.” The solar system was bombarded by asteroids early in its history, and if they were indeed wetter than they are now, that explains where the water in our oceans, in our seltzer bottles, in our bodies and everywhere else comes from.

Important as this new finding is, it’s likely to be only the first of many Rosetta will make as it rides along with 67P for the next year or so, watching carefully as the warming rays of the Sun bring the comet to life. “It’s a nice start to the science phase of the mission,” Taylor said.

And if you think you’ve heard the last of the Philae lander, think again. Mission controllers are still trying to pinpoint Philae’s precise location on 67P’s surface. That will allow scientists to do at least one more experiment: they’ll send radio pings from Rosetta through body of the comet to bounce off Philae and back to Rosetta. By examining how the radio beams are altered en route, they will be able to figure out whether 67P’s insides are rock-solid or held together relatively loosely.

Locating Philae would also allow scientists to calculate whether the lander might be brought back from the dead six months from now. It’s just possible, said Taylor, that a change in 67P’s orientation could bring Philae back into the sunlight, allowing its solar panels to recharge its batteries. If that happens, the prospects for extraordinary science from this already wildly successful mission will be even greater.

TIME space

Here Are 5 Cool Things You Didn’t Know About Pluto

Denis Scott—Corbis

Principal New Horizons scientist answers all your burning queries

Correction appended Dec. 9, 2014

On Saturday, the New Horizons space probe was roused from hibernation for the last time before its July close encounter with Pluto. TIME caught up with mission’s principal investigator, Alan Stern of the Southwest Research Institute, and asked him to come up with five cool things we’ll learn about Pluto during the encounter, and five cool things you should know about the space probe itself.

Given that Stern has been thinking about Pluto for decades, and working on New Horizons for nearly 15 years, it should come as no surprise that he rattled off his top 10 without breaking a sweat.


Does Pluto have craters?

You’d think so, since Pluto, once believed to be all alone at the edge of the Solar System, is just part of the Kuiper Belt, a swarm of billions, or even trillions, of icy bodies that lie out beyond Neptune. The smaller ones have presumably been peppering Pluto for billions of years. But Pluto’s surface might consist of a thick layer of nitrogen ice, which would be soft, mushy and unlikely to form long-lasting craters. There could even be liquid nitrogen on the surface, which could smooth out any impact craters.

Does Pluto have an ocean?

It just might, down below the surface. “The deeper you go, the higher the pressure,” Stern said. That makes the interior warmer than the surface, which means it could get warm enough for ice to melt into water. New Horizons could detect the ocean indirectly, by measuring Pluto’s shape to high accuracy and by looking for cracks that might signal a solid crust flexing atop an underground ocean.

How many moons does Pluto have?

“We know it’s got five, based on observations from Earth,” Stern said. “But how many more are there? Another five? Fifteen? Fifty? All of these are possible. However many there are, they might have been captured when they ventured too close to the planet, or they might have been created in a huge impact that created Pluto’s large moon, Charon, or it might be a combination. New Horizons could answer that question too.

Does Pluto have rings?

Could be. You can’t tell from Earth, but Pluto’s moons Nix and Hydra have weak enough gravity that impacts from smaller objects could kick up dust that would fly off into space and potentially form rings about Pluto itself.

Does Pluto have geysers, volcanoes or other geological activity?

You’d think a world that averages 3.67 billion miles away from the sun would be deep-frozen, but if there’s an underground ocean, it could trigger geysers like those on Saturn’s moon Enceladus, volcanoes like those on Jupiter’s moon Io, or some sort of plate tectonics, as on Jupiter’s moon Europa.


Is Pluto a planet?

Depends on who you ask, and that’s not likely to change after the encounter. If you ask Stern, it definitely is. He’s more than fine with your calling it a dwarf planet. In fact, he points out, “I invented the term.” What he doesn’t get is why the International Astronomical Union came out with a new definition of “planet” back in 2006 (and just a few months after New Horizons launched) that excluded dwarf planets. “Does that mean a dwarf evergreen should be considered an evergreen?” asks Stern, pointedly? In a recent debate at Harvard, the best explanation the IAU’s representative could come up with for keeping dwarf planets out of the ranks of planets was basically that otherwise there would be too many planets to remember. Which might be true, but it’s not all that persuasive.


It’s smaller and much simpler than the Voyager probes that visited Jupiter, Saturn and the other outer worlds (except Pluto!) in the 1970s and 1980s.

“It’s like a modern tablet compared with an old mainframe computer,” says Stern

It was approved by NASA after five earlier Pluto missions failed to make the cut.

“It was mostly due to cost overruns,” says Stern. “They kept adding extra capabilities like ornaments on a Christmas tree.”

It’s the fastest spacecraft ever to leave Earth.

New Horizons took off for Pluto at a record 36,000 m.p.h.

During closest approach, about 8,000 miles from Pluto’s surface, New Horizons’ cameras will be able to see objects just two miles across.

That’s pretty darned small.

Pluto may not be New Horizons’ last stop.

Pending NASA approval, the probe should still have enough fuel to reach a second, smaller Kuiper Belt object a couple of years after the Pluto encounter. At least two potential targets have already been identified.

The original version of this story misstated the minimum size of the objects New Horizons can see. They are less than 100 yards across.

TIME Longevity

Want to Live Forever? These Men Say They Can Help

It’s not always easy to tell whether the new documentary titled The Immortalists is sympathetic to its two primary characters or whether it’s making fun of them. The men in question, Bill Andrews and Aubrey de Grey, are scientists who have independently vowed to cure aging and vanquish death. That alone suggests they belong in the fruitcake bin, along with the better known Ray Kurzweil, who intends to have his brain uploaded to a computer in 2045 in an event he calls the Singularity.

The impression becomes stronger when directors David Alvarado and Jason Sussberg delve into Andrews’ and de Grey’s lives and backgrounds, in an attempt to help viewers understand what motivates them. The bottom line: they disapprove of death. “This wasn’t supposed to happen,” says a tearful Andrews at one point of a colleague who died of cancer at a relatively young age. “We were on the same mission.” Biology evidently hadn’t gotten the memo. De Gray, meanwhile, walking through a cemetery, declares, “I don’t want to get Alzheimer’s and end up in a place like this.”

Most of us agree that death seems unfair, unless we believe in a redemptive afterlife, which neither Andrews nor de Grey seems to—and even religious folks would generally like a few more decades of life before going to the Great Beyond. Most of us also believe bad things shouldn’t happen to good people—a sort of “All I Really Need to Know I Learned in Kindergarten” philosophy that’s as appealing as it is unanchored in any sort of rationality.

Both Andrews and de Gray are scientists, though, and their parallel quests to defeat aging have at least a plausible scientific basis. The key, they believe, lies with the telomere, a sort of protective endcap on our chromosomes that shortens every time a cell divides. When the telomere gets too short, the cell’s number is up. But a natural enzyme called telomerase can protect the telomere from damage, which suggests that having more of the enzyme could stave off aging and death.

So far so good, and scientists worldwide are looking into the details of exactly what telomerase does and how it does it—and whether boosting it artificially might help stave off aging. Those details could prove to be devilish, though. Back in the late ’70s scientists were intrigued with a natural substance called interferon, which showed promise as a magic bullet against cancer. It wasn’t. In the late ’90s there was lots of excitement about anti-angiogenesis drugs, also meant to wipe out cancer. But despite early promise, they too have failed to impress.

Most scientists are more careful now about making dramatic pronouncements about magic cures even for single diseases, let alone aging and death itself. But not Andrews or deGray. As it happens, legitimate, independent scientists are few and far between in The Immortalists, and those who do appear are less than effusive. “I find Aubrey’s position quite difficult to pin down,” says Colin Blakemore, a neuroscientist at the University of London. “He made a statement that the first person who will live to 1,000 is alive today. I think that’s foolish.” William Bains, meanwhile, a biotech entrepreneur admires de Gray for being able to drink prodigious amounts of alcohol and still think serious scientific thoughts. I’d take an anti-aging cure created by a guy like that. Wouldn’t you?

The directors want us to understand both de Gray and Andrews as visionaries whose own private lives exemplify their maverick attitudes toward conventional wisdom. That part certainly works: we see Andrews running a 100-mile-plus ultramarathon across the Himalayas and we get to watch de Gray frolic nude on a blanket with his wife. (de Gray is polyamorous; his wife is not amused).

The film itself, which premiered last week in New York and opens December 11 in Los Angeles, artfully leaves it up to viewers whether de Gray and Andrews are crackpots or whether they’re outside-of-the-box thinkers who truly might help us live forever.

My vote: they should have stayed in the box.

TIME space

You’ve Heard of Shooting Stars, but This is Ridiculous

Coming soon (sort of): The Andromeda Galaxy (above) will produce lots of free-range stars when it merges with the Milky Way—in two billion years.
Coming soon (sort of): The Andromeda Galaxy (above) will produce lots of free-range stars when it merges with the Milky Way—in two billion years. T Ware Jason; Getty Images/Photo Researchers RM

A new theory predicts a new breed of cosmic wanderers

The idea that stars live in galaxies has been astronomy’s conventional wisdom since the 1920’s. It took a serious hit recently, though, when observers concluded that as many as half the stars in the universe might actually hover outside galaxies, flung off into the intergalactic void as collateral casualties when smaller galaxies merge to become large ones.

But while that discovery was startling, a new prediction posted online takes the finding to a whole new level. A significant number of stars, say Avi Loeb and James Guillochon, of the Harvard-Smithsonian Center for Astrophysics, should not just be floating through intergalactic space: they should be screaming across the cosmos at absurdly high speeds. “We calculate that there should be more than a trillion stars in the observable universe moving at velocities of more than a tenth the speed of light,” says Loeb. That’s about 67 million m.p.h. (108 million k/h). And about ten million of those stars, he says, are moving at least five times faster than that.

High-velocity stars are not without precedent. Astronomers already knew of a handful of stars in the Milky Way that are moving at a million m.p.h (1.6 million k/h) or so, and which should eventually leave our galaxy. But this new class of speedsters—if they’re confirmed—would make those so-called hypervelocity stars look like garbage trucks lumbering along in the cosmic slow lane.

There’s reason to hope that the findings are validated, beyond the mere wow factor of the work. Astronomers currently study the origin and development of the universe by trapping particles in telescopes and detectors—photons of light, mostly, and also, more recently, the ghostly particles called neutrinos, which bear information about the stars, galaxies and quasars in which they originated. Superfast stars would be another sort of “particles,” albeit huge, shining ones, which could tell astronomers plenty about the conditions they’ve encountered since they escaped their galactic homes. “They give us the opportunity to do cosmology in an entirely new way,” he says, “with massive objects moving at near lightspeed across the universe.”

How they got moving so fast is the core of Loeb’s and Guillochon’s idea. Most galaxies harbor huge black holes in their cores, and when two galaxies merge to form one, those black holes end up circling each other in a tight do-si-do. Eventually, they too will merge into a single object, but as they approach each other, the complex gravitational interplay between them and the stars that orbit them exerts incredible force—and impart incredible speed. (Black hole interactions also give rise to hypervelocity stars within the Milky Way, but here there’s just a single black hole, and thus a lot less energy available.)

As the free-range, extra-galactic stars fly across the universe, their trajectories are bent by the gravity of galaxies they pass along the way. “It’s like a ball moving through a pinball machine,” says Loeb. “If we can reconstruct their trajectories back to their original host galaxies, we can test whether General Relativity [Einstein’s theory of gravity] acts the way we expect.”

You can do this only if you actually find the speeding stars—but Loeb is convinced it’s possible. “It’s challenging,” he admits, “but they could be detected with upcoming instruments.” Among them: the Large Synoptic Survey Telescope, the James Webb Space Telescope, the Thirty Meter Telescope and more, all of which are expected to come online by the end of this decade.

“The most exciting aspect,” Loeb continues, is that these need not be single stars.” They could be double stars, or even stars with planets. “If these planets are habitable,” says Loeb, “these would be the most exhilarating roller-coaster rides in the universe.”

While none of this can happen in our own galaxy at the moment, that’s just a temporary situation. The giant spiral galaxy M31, also known as Andromeda, is slowly approaching the Milky Way. In two billion years or so, they’ll smash together. When they do, the new, gigantic galaxy that emerges will at last be equipped with the twin black holes you need to build a cosmic slingshot.

What happens after that is anybody’s guess.



TIME space

Watch a Black Hole Get Evicted From a Galaxy

A dramatic study—and an equally dramatic video simulation—reveal a cataclysmic cosmic event

A couple of years ago, astronomer Michael Koss was searching the heavens for active galactic nuclei (AGN). In plain English, those are giant black holes, lurking in the cores of galaxies, which swallow matter so voraciously that the gas they gobble heats up to an incandescence visible billions of light-years away. And he wasn’t looking for just any AGN; he was looking for twin AGNs, which occur when two AGN-bearing galaxies merge into one.

Then, says Koss, “I found this thing.”

The thing was just a single spot of light, labeled SDSS1133, nestled in a dwarf galaxy called Markarian 177, located in the bowl of the Big Dipper, about 90 million light-years from Earth. It looked just like an AGN—except it wasn’t in the galaxy’s core. It was off-center by about 2,600 light-years. So maybe it wasn’t an AGN after all, but an unusual type of exploding star.

But when Koss went back to earlier observations, some made by NASA’s Swift satellite, the bright spot was there, at least as far back as the 1950’s. Since stars don’t usually take a half-century to explode, Koss and several colleagues were forced to consider a much stranger possibility: the mystery object could be an AGN after all, but one that was somehow booted from the center of its galaxy. Their report appears in the November 21 Monthly Notices of the Royal Astronomical Society.

You might imagine it would be touch difficult to boot a black hole anywhere, especially one that weighs millions of times as much as a star. There is, however, one thing that could do the job: a second black hole. Sort of. “We suspect we’re seeing the aftermath of a merger of two small galaxies and their central black holes,” said co-author Laura Blecha, of the University of Maryland, in a statement.

The idea goes like this. Astronomers know that galaxies that wander too close to each other get trapped by their mutual gravity, and merge into one; it happens all the time, in fact. Since virtually all galaxies have huge black holes inside, the new, combined galaxy ends up with twin black holes in their cores (some of which turn into the double AGN’s Koss was looking for in the first place).

But the black holes themselves can merge as well. When that happens, the cataclysm sends gravitational waves rippling across the universe. If the black holes have different masses and different spins, those waves can shoot out more powerfully in one direction than another—and that can kick the new, single black hole right out of the galaxy’s core. “That’s our most plausible case,” Koss says.

It’s not the only case, however: the scientists haven’t ruled out the idea that the bright spot is an exploding star after all. If so, the light seen in earlier images from the 1950s could have come from violent eruptions on the star, which culminated in an explosion back in 2001, when SDSS1133 brightened visibly. It’s not unheard of: a nearby star in our own galaxy, Eta Carinae, is erupting in what astronomers think could be a prelude to a full-fledged supernova explosion.

But SDSS1133 shines brightly in ultraviolet as well as visible light, even though the ultraviolet light from supernovas tends to fade quickly. Followup observations with the Hubble Space Telescope a year or so from now could clear up the question for good.

In the meantime, it’s natural to wonder whether SDSS1133 will eventually fly out of its host galaxy entirely and begin to roam the universe as a naked black hole. The answer, says Koss, is “it’s hard to say.” The galaxy itself is small, so it doesn’t have a lot of gravity to hold SDSS1133 back. But the original kick wasn’t all that hard, so the black hole might not have reached escape velocity.

In short, we’ll know one way or another whether SDSS is a black hole within the year. To learn whether it will escape Markarian 177—well, that’ll take a couple million.

TIME space

Strange Visitors From the Edge of the Solar System

Sometimes a comet isn't a comet
Sometimes a comet isn't a comet Art Montes De Oca; Getty Images

A pair of sort-of comets pose a puzzle for astronomers

The term “Oort Cloud” may be obscure for many people, but it’s familiar terrain for astronomy buffs. It’s a giant spherical swarm of trillions of proto-comets, lurking at the outer fringes of the Solar System, so far away that it may stretch a quarter of the way to the nearest star. They’re proto because they’re not technically comets unless they get knocked out of orbit and fall toward the heat of the Sun, whose warmth turns their long-frozen ices into a halo of dusty gas and, sometimes, a tail as well.

A pair of very unusual objects announced at last week’s Planetary Science Meeting in Tucson, however, have complicated this seemingly straightforward story. The first, found in 2013, has an orbit that clearly shows it came from the Oort Cloud—but while it resembles a comet in some ways, it didn’t light up like one even after it warmed. The second, found just this past September, also came from the fringes of the Solar System. This one doesn’t even resemble a comet, let alone act like one: it looks more like a rocky asteroid.

Except asteroids aren’t supposed to live in the Oort Cloud—and that creates just the sort of mystery scientists love. “We’re all very excited,” admits Karen Meech, of the University of Hawaii, who led the discovery team. But while both objects surprised researchers, both turn out to confirm two pieces of cosmic wisdom, one from a half-century ago and the other much more recent.

The old wisdom comes from Jan Oort himself, the mid-20th-century Dutch astronomer the Oort cloud is named for. He theorized that long-period comets, with highly elongated orbits lasting more than 200 years, came from a distant, spherical cloud that surrounds the Solar System. “He figured this out based on just 13 comets,” says Meech. “It’s really amazing.”

The idea is that the comets formed closer in, along with the rest of the Solar System, but that many were flung outward in gravitational interactions with Neptune and other giant planets. That notion was reinforced long after Oort’s time, when planetary scientists realized that the giant planets might have changed their orbits significantly soon after they were born; that motion would have ejected icy bodies in vast numbers.

Oort also suggested that the objects that eventually fell in again would be especially bright the first time around, since they’d have lots of ice on their surfaces—precisely what happened when Comet Hale-Bopp showed up in 1997. “On their very first passage through the inner Solar System,” says Meech, “all of that sublimates away, so after that you just don’t see them.”

The object discovered in 2013, she says, which is known as (deep breath) C/2013 P2 Pan-STARRS, fits the profile of what an Oort cloud comet should look like on a second or later return to the inner Solar System, and, says Meech “it may be proof at last that Oort was correct.”

Even as the astronomers were trying to figure out what they were seeing, though, the second object, C/2014 S3 Pan-STARRS, showed up (in both cases, the objects were found by the Pan-STARRS1 telescope, atop Mauna Kea, in Hawaii). It didn’t act like a comet either, but unlike the first object, it also didn’t much resemble one, as a close look at its composition revealed.

And that seems to support an idea advanced back in 2011 by Kevin Walsh, of the Southwest Research Institute, along with several colleagues. Their computer models of the newborn Solar System found that the giant planets should indeed have migrated from their original positions, moving first in toward the Sun, then out to where they are today. As they moved out, says Meech, “they would have dragged about fourteen Earth masses worth of material with them and thrown it outward.”

That material, in the form of asteroids, could have ended up in the Oort Cloud along with the proto-comets. Even as recently as a decade ago, this theory would have seemed crazy. Now—as so often happens—the very old solar system is teaching us something very new.

TIME space

Since You Wondered, Here’s Why Jupiter’s Great Red Spot Isn’t White

NASA says it's likely "a sunburn, not a blush"

The giant cyclonic storm that swallowed Alaska last week has nothing on Jupiter’s Great Red Spot. The GRS is a cyclone, too, but one so immense it could gulp down the Earth in one shot and still have room for Mars. It’s been swirling for centuries, at the very least, and while it’s smaller than it used to be, nobody thinks it’s going away.

All of this is pretty well known to planetary scientists. What they don’t know is the answer to a very simple question: Why is the Red Spot, well, red? “There are some other places on Jupiter that are reddish,” says Kevin Baines of NASA’s Jet Propulsion Laboratory (JPL), “although they’re more of a reddish-brown.” The spot’s color, however, is pretty much unique and thus pretty mysterious. In fact, Baines adds, “back in the 1970’s, when we were trying to sell the Galileo mission to Congress, it really resonated that we were going to try and answer that question.”

Now Baines and two JPL colleagues may have finally done it — not with data from Galileo, which orbited Jupiter and its moons from 1995 to 2003, but from the Cassini probe, which took a few snapshots en route to Saturn. Those images, supplemented by laboratory experiments, suggest that the red color is just a thin dusting on the very top of swirling clouds that are otherwise white. “I call it the creme brulee model,” Baines says, “or the strawberry frosting model.”

Cassini was essential to solving the mystery because its instruments were sensitive to a broader range of light wavelengths than Galileo’s, and could thus show that the very center of the Red Spot is redder than the rest. The center is also at the highest altitude of what’s already an unusually high-altitude feature. “It reaches something like 50,000 feet higher than the surrounding clouds,” says Baines.

That exposes the swirling clouds to more intense ultraviolet light from the sun than most of Jupiter’s clouds. And when the JPL scientists did lab experiments to test the effects of ultraviolet rays on chemicals such as ammonia, acetylene and various hydrocarbons, which are abundant in Jupiter’s atmosphere, they got the same red colors seen on the giant planet itself. (They did eventually, anyway. At first, they did their tests with ammonium hydrosulfide, another chemical abundant on Jupiter, and recreated what Baines calls the “Great Green Spot. We were faked out,” he says.)

This isn’t the only evidence that the Spot’s red is created from above rather than coming from reddish gases upwelling from below, which is the leading alternate theory: There actually are some other tiny spots of red dotted around Jupiter, and they also coincide with clouds of unusually high altitude.

The Red Spot, in short, as a JPL press release cutely puts it, represents “a sunburn, not a blush,” on the face of the Solar System’s largest planet.

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