Object type: Exploding star
Location: 160,000 light years from Earth, in the Large Magellanic Cloud

“Once in a lifetime” barely begins to describe it – astronomers had literally been waiting centuries for such a spectacle. The supernova that blazed forth on 23 February 1987 was the brightest since the one Johannes Kepler spotted in 1604.

The explosion happened just an astronomical stone’s throw away, in a satellite galaxy of the Milky Way, which is why it was so bright it could be seen with the naked eye. No supernova so nearby had been seen since the invention of the telescope.

“There was a lot of excitement,” recalls of the University of Virginia in Charlottesville. “People started to call each other up, saying ‘This is it!'”

But even before telescopes detected any brightening, experiments in Japan and the US were hit by generated during the star’s death. In fact, SN 1987A remains the only supernova to explode close enough for its neutrinos to be detected on Earth.

So does the fact that the explosion’s neutrinos arrived faster than its light support the claim made last year that the subatomic particles might break the cosmic speed limit set by Einstein’s special theory of relativity? Surprisingly, no.

Birthday surprise

The neutrinos showed up just a few hours before the supernova appeared in telescopes. That slight time difference was expected, since neutrinos hardly interact with normal matter. They could just fly unimpeded through the stellar shrapnel, while the photons were waylaid by the exploding star stuff. Even setting off slower than light, the standoffish neutrinos could have made the trip faster.

If, on the other hand, the supernova’s neutrinos had been moving as fast as those reported by researchers on the OPERA experiment last year, they would have arrived at Earth years before the light from the explosion.

That, clearly, was not the case. So perhaps it was the ultimate birthday present for SN 1987A when the OPERA team said on Thursday – the 25th anniversary of the supernova’s appearance – that the faster-than-light claim might have been down to an instrumental glitch.

Morbid curiosity

Aside from boosting evidence for relativity, the supernova also shed light on a vexing problem for astronomers: what do stars look like just before they die? Supernovae usually pop off so far away that only their host galaxy can be made out – not individual stars.

SN 1987A, being in a neighbouring galaxy called the Large Magellanic Cloud, was different. Astronomers scoured archival images taken of the same region of sky and were able to spot a star at exactly the same spot. The only problem was – the star wasn’t what they were expecting at all.

Stars expand and cool as they age, so researchers thought they would find a bloated, tepid red giant. Instead they found a much hotter, blue star.

Stellar union

One possible explanation is that about 20,000 years before going supernova, the doomed star merged with a stellar partner. It shed its cool outer layers in the process – forming rings that are still visible today – and transformed into a hot blue star.

Astronomers have recently identified other, more distant and were likely also produced by blue stars. Studying their properties could help confirm or rule out the binary merger explanation.

And we’re still learning from SN 1987A itself as its expanding debris cloud continues to evolve. Recent observations show that the debris is starting to collide with the main ring of material ejected when the stars merged.

The collision is heating up the expanding supernova debris, making it glow, according to observations . By studying this glow, we can learn more about the innards of the star that went supernova, perhaps gaining new insights into its structure and composition.

“It’s a rare opportunity,” says Chevalier. “Every year we find lots of supernovae, but they’re typically at least a factor of 100 farther away. Having something this close by is an extremely special event.”

Journal references: ,

Read previous Astrophile columns: ‘Missing link’ black hole is stress eater, A-List black hole gets a face, Pinball planets get wild, deadly ride, Picture yourself on a sandboard on Titan, How to spot a dark-matter galaxy , Glimpse elusive matter in shattering star, Cool echoes from galaxy’s biggest star, Stopped clocks deepen pulsar enigmas, Wounded galaxy is crux of cosmic whodunnit, Did comet killing spark Christmas light show?, Blinged-out stars were born rich, Supercritical water world does somersaults, Attack of the mystery green blobs.

AN UNDERDOG dark-matter particle could explain why the universe seems strangely low on lithium. If the idea holds up, it will be a boon in the hunt for dark matter, the stuff needed to account for 80 per cent of the universe’s matter.

In the universe’s first few fiery minutes, nuclear reactions forged a host of light elements, including helium, deuterium and lithium, in a process called big bang nucleosynthesis. The amounts of these elements present in the early universe, gleaned from ancient stars and primordial gas clouds, match theory, except in one respect: they contain much less of the dominant form of lithium, lithium-7, than expected. There has never been a satisfactory explanation for this.

Now help comes in the shape of hypothetical dark-matter particles called axions. These light particles were dreamed up in the 1970s as part of a theory to explain why the , does not change if a particle is swapped for the antimatter counterpart of its mirror image. Axions are not the dominant theory for dark matter. That accolade goes to weakly interacting massive particles, or WIMPs. But as neither WIMPs nor axions have ever been observed, the jury is still out.

In the latest research, the underdog axions score a point. The rates of nuclear reactions that produced lithium-7 depend partly on the amount of energy that was present in the form of light. As we cannot tell how much light was there directly, we infer it from the cosmic microwave background (CMB), the echo of the big bang that emerged 380,000 years later. This is used to estimate how much lithium should be present: more light skews reaction rates and lowers expected levels of lithium.

Ozgur Erken of the University of Florida in Gainesville and colleagues suggest that something cooled photons between the synthesis of lithium and the emergence of the CMB, causing the photon energy to be underestimated, and inflating the expected amounts of lithium.

Born with very little kinetic energy, axions are a prime suspect. When their cooling power is accounted for, the predicted lithium abundance drops by half, the team calculate (Physical Review Letters, ). “We’re excited that it gives about the right correction,” says , Erken’s colleague.

“When axions’ cooling power is accounted for, the predicted lithium abundance drops by half”

Adding in axions also creates a problem, however. Without them, CMB measurements are consistent with about four types of neutrino, close to the three types glimpsed in experiments. But if axions are present, they would skew this measurement and imply about seven neutrino types, Erken’s team calculate. This makes of Ohio State University in Columbus, who was not involved in the study, sceptical of the axion explanation for the lithium-7 anomaly.

An answer should come in 2013 when much better measurements of the CMB are expected from the Planck satellite. Our best chance of glimpsing axions, meanwhile, lies in an upgraded version of , due to start up towards the end of this year. It may also be possible to infer their existence from at CERN near Geneva in Switzerland, where they should boost the production of Higgs bosons.

Iran’s nuclear prowess is growing, fuelling a range of global tensions. Are scientists’ abilities to sniff out covert nuclear weapons tests keeping up? Two new techniques could at least make it harder for countries to develop nuclear weapons on the sly.

Last week, the Iranian government flaunted its growing nuclear might, unveiling a for enriching uranium. Though it insists this is only for peaceful purposes like generating electricity, the US and other western nations have suggested Iran may be secretly developing nuclear weapons.

If Iran is, at some point it will have to test them. Existing sensors rely on monitoring for abnormal seismic activity and in the atmosphere. These are not foolproof.

Exploding a nuclear weapon in a , for example, can reduce the intensity of seismic waves and keep radioactive gases contained.

Ionospheric imprints

Such techniques could render the smallest nuclear explosions undetectable, and for larger blasts could be a way to conceal the total energy released, or yield – a sign of the extent of a nation’s nuclear capability. The two new tools could help flag tests that would otherwise go unnoticed and reveal more accurate information about yield.

One looks for disturbances in the ionosphere, the region of space just above the atmosphere. The force of a subterranean nuclear blast causes the earth above to instantly flex upwards, disturbing the air. The resulting waves ripple through the atmosphere all the way up to the ionosphere. As it contains lots of electrically charged particles, radio signals from GPS satellites get distorted by these waves.

Now Yu-Ming Yang of Purdue University in West Lafayette, Indiana, and colleagues have found ionospheric disturbances coinciding with two underground nuclear tests carried out by North Korea in 2006 and 2009, in .

Both tests were also big enough to have been detected previously by their seismic waves, but the ionospheric disturbances allow for a more detailed picture of the blast, says Yang’s colleague .

Ground swell

Further research on the ionospheric imprints might allow researchers to calculate the yield from them too, he says. Solar flares can also disturb the ionosphere so further work is needed to home in on nuclear disturbances.

For a much more subtle, long-term signature of nuclear tests, at Oregon State University in Corvallis and colleagues turned to satellite-based radar measurements of the Lop Nor underground nuclear test site in China.

These showed that the ground swelled in an area about 2 kilometres wide over several years in the 1990s. The team attributes this to tests carried out then – one in 1992 and two in 1995. The swelling was greatest at the centre of this zone, where the . The team suggests that colossal amounts of heat from the nuclear tests gradually warmed the rock above, causing it to swell.

Such swelling takes years to become noticeable, unlike the seismic and ionospheric signatures. Like the ionospheric technique though, in combination with other methods, swelling could help to calculate a device’s yield.

The US and other nations have tightened sanctions on Iran in recent weeks. Today, the UN’s International Atomic Energy Agency announced its team was leaving Tehran after two days of talks with Iranian officials that to Iran’s nuclear programme.

Journal references: Geophysical Research Letters and

Is there life on Mars? We might not find out for some time. The search has hit a major hurdle because NASA has cancelled plans for ambitious new missions to the Red Planet.

NASA and the (ESA) were planning a to Mars that could have made important strides in the search for past or present life.

The ExoMars Trace Gas Orbiter, which was to launch in 2016, would have followed up on hints of methane discovered in the Martian atmosphere by previous missions. The gas is of particular interest as it is commonly produced by microbes on Earth.

The ExoMars rover, which had been slated for launch in 2018, would have drilled beneath the Martian surface to get samples of pristine material, possibly including complex carbon-based molecules that could have provided clues to past Martian life.

But NASA has told ESA that it can no longer afford to participate in those missions, agency officials confirmed today.

Russian rescue?

The missions may end up being cancelled or at least drastically scaled back, although ESA is reportedly trying to on board instead.

NASA administrator Charles Bolden and other officials explained in press briefings today that they had to make tough choices in crafting NASA’s budget for 2013.

The White House’s was released on Monday 13 February along with those of all other departments and agencies.

If approved by Congress, the budget will give NASA $17.7 billion in 2013, about the same as it got in 2012, but around $1 billion less than it had been projecting for 2013 when making plans over the last few years.

No more flagship

The Mars budget was slashed as a result, with NASA’s contribution to the flagship ExoMars mission the main casualty.

“We just could not do another flagship right now,” Bolden said. “It was not in the cards … in these very difficult fiscal times.”

NASA still hopes to mount a less costly mission to Mars in 2018, but it might not land on the surface. The agency has not specified exactly where it would go, but orbiters tend to be less expensive than rovers.

The proposed budget also confirms that NASA plans to continue building the with a launch targeted for 2018, and continue payments to private space companies like to help them develop space taxis that could take crew to the International Space Station.

NASA wants $830 million for space taxi development in 2013. It asked for a similar amount in 2012, but Congress cut it by more than half, to about $400 million.

It has already broken the record for the most energetic particle collisions, but the world’s largest particle smasher is boosting its energy still further. Physicists at the Large Hadron Collider hope this will confirm or rule out tantalising hints of the elusive Higgs particle.

Although the Higgs is the LHC’s main quarry, the biggest advantage from the boost in energy goes to searches for signs of supersymmetry, or SUSY. Many researchers had hoped that by now this elegant theory would have left traces in LHC, which is at the CERN particle physics laboratory near Geneva, Switzerland.

The LHC has already seen many events that could be signs of the decay of the long-sought Higgs boson, which is thought to endow other particles with mass. But more mundane reactions can also produce such events, so more experiments are needed to confirm or rule out the Higgs explanation.

Now the LHC’s management has decided to get a better chance of flushing the Higgs out into the open.

Higgs boost

Last year, the LHC smashed two beams of protons together at an energy of 3.5 teraelectronvolts (TeV) each, resulting in collisions with a total energy of 7 TeV.

The machine’s managers have decided to increase the energy of collisions to 4 TeV per beam, for a total energy of 8 TeV.

The probability of a collision producing heavy particles rises very fast as its energy increases, so even a small rise in energy will provide a big boost to the number of Higgs bosons made – and therefore the probability of glimpsing them or other exotica.

Running at 8 instead of 7 TeV should boost the machine’s sensitivity to Higgs particles – assuming they are really there – by 30 to 40 per cent, says of Brown University in Providence, Rhode Island, who is involved in , one of the LHC’s two main detectors.

Heavy partners

The boost in energy also increases the chances that signs of SUSY will emerge.

The theory posits the existence of heavy partners for each of the subatomic particles already known. The move to 8 TeV could boost the production of these “superpartners” as much as four times, says Landsberg.

“We could get a little hint of existence at 7 TeV versus discovery at 8 TeV,” he says.

Researchers want to maximise the potential for new discoveries this year because at the end of it the LHC will shut down for two years. Upgrades will then allow it to run at its full design energy of 14 TeV.

The Higgs boson should have already been confirmed or ruled out before then. The higher energy will allow a thorough search for the heavy particles predicted by SUSY, among other things.

Object type: Black hole
Location: M87 galaxy, 50 million light years from Earth

Being photographed is pretty much a way of life for human celebrities. Not so astronomical ones. The most massive black hole ever measured, which lies at the heart of the galaxy M87, 50 million light years from Earth, is the closest thing we have to a celestial bigwig. Yet no picture of it, or any other black hole, has ever been snapped.

That’s not just a problem for fans lusting after a pin-up. Seeing the shadow of a black hole would provide the first direct evidence that these bizarre objects really do exist. What’s more, looking at the way light bends around the edges of the shadow could also turn up deviations from Einstein’s theory of general relativity, the reigning theory of gravity that some physicists want to replace.

The trouble is not that black holes are invisible: as great absorbers of light, they should appear as a black spot when viewed against a bright background. Rather, all known black holes are too far away for ordinary telescopes to make out the shadow. However, plans are afoot to take a picture of a black hole using radio telescopes set far apart on Earth but which together act like a single huge telescope thousands of kilometres across.

In the meantime, of the University of California in Berkeley and colleagues have created the next best thing – the most realistic preview yet of what the black hole at the heart of M87 looks like. As well as putting a face on this A-list object, their simulations reveal details that suggest glimpsing M87’s black hole for real may well be feasible.

Smeared jets

The team simulated how matter and light behave near M87’s black hole. Unlike previous efforts, their calculations fully incorporated general relativity and the effects of powerful magnetic fields near the black hole.

They simulated the disc of gas and dust that is swirling around it as well as the powerful jet of electrically charged particles shooting into space from the black hole’s vicinity.

Both the disc and jet emit radio waves. But rather than travelling in straight lines, the radio waves are bent by the black hole’s powerful gravity, which acts a little bit like a lens.

This would radically distort the appearance of the disc and jet in radio images, the researchers found, smearing them to make a bright crescent surrounding the dark shadow of the black hole.

In a real image, the existence of this shadow would provide direct evidence for an event horizon, the defining feature of a black hole. Once light, or anything else, passes inside this boundary, it can never escape.

Target: M87

The simulations suggest the black hole’s shadow should be observable with telescopes that researchers are planning to link up for this purpose. The researchers concluded this from calculations of the shadow’s size and the size of the smallest details discernable by such linked telescopes.

With a mass that was recently revised upwards to 6.4 billion times that of the sun, M87’s black hole seems like an ideal photographic target, because its shadow should look relatively large in the sky.

Though the black hole at the heart of our own galaxy would appear slightly larger because it is so much closer, M87’s position in the sky means it is easier to observe using some of the best radio telescopes. Its black hole could well be the first to be seen directly.

These images will be the next best thing to actually travelling across the event horizon into a black hole – an experience that has been simulated but will remain forever in the realms of science fiction.

Journal reference:

Read previous Astrophile columns: Pinball planets get wild, deadly ride, Picture yourself on a sandboard on Titan, How to spot a dark-matter galaxy , Glimpse elusive matter in shattering star, Cool echoes from galaxy’s biggest star, Stopped clocks deepen pulsar enigmas, Wounded galaxy is crux of cosmic whodunnit, Did comet killing spark Christmas light show?, Blinged-out stars were born rich, Supercritical water world does somersaults, Attack of the mystery green blobs, Undead stars rise again as supernovae, The sticky star cluster that’s mostly black hole.

In December 2011, the elusive Higgs boson was back in the limelight when hints of the particle emerged in the wreckage of proton collisions at the world’s most powerful particle smasher – the Large Hadron Collider (LHC) near Geneva, Switzerland.

There have been no new collisions since, but researchers from the LHC’s two main detectors have given the existing data a more careful look, culminating in two fresh Higgs analyses released on Tuesday. Here ��è����Ƶ disentangles what we can and can’t conclude about the particle that is swiftly becoming the people’s favourite

Remind me: what was the scoop in December?
The Higgs boson is the missing piece of the standard model of physics, the leading theory for how particles and forces interact. The Higgs is thought to endow others with mass but has yet to be positively observed, so its mass – and existence – are still unconfirmed.

In December, the LHC’s two main particle detectors, CMS and ATLAS, each reported excesses of events, such as the appearance of a pair of photons in the shrapnel from particle collisions. These excess events could be due to a Higgs with a mass of around 125 gigaelectron volts (GeV; particle masses and energy can be treated interchangeably).

Great. End of story?
Far from it. Since more mundane reactions can produce such events too, they do not provide definitive evidence for the Higgs.

By convention, researchers only declare a discovery when an anomaly reaches a statistical significance known as 5 sigma, which means there is less than a 1-in-a-million chance it is just a fluke. The size of the anomalies reported by the two detectors in seminar in December was 1.9 sigma for CMS and 2.5 sigma for ATLAS, which indicate a probability of a fluke of roughly 1 per cent.

So what’s the latest?
After taking a closer look at the data, ATLAS finds little need for revision, . But the CMS analysis reports some extra events that were not analysed in time for LHC’s December announcement. These events could be due to a Higgs boson of around 125 GeV decaying into a pair of photons – after being produced from the collision of two particles called W and Z bosons, that transmit the weak force.

Adding these events to the December analysis gives a small boost to the overall statistical significance of CMS’s Higgs hint, which . “It’s not a radically different picture,” says of Brown University in Providence, Rhode Island, who works on CMS.

What’s this about 4.3 sigma, then?
A blog post on the Nature website on Tuesday states that an unofficial synthesis of the two results gives a . But of ATLAS says it would be premature to reach that conclusion before the Moriond conference in La Thuile, Italy, in March. “Combining the two experiments may happen after the first week of March but not before,” she says. “Until then, it is anyone’s guess.”

Will combining the CMS and ATLAS results boost the significance?
Not necessarily, Landsberg says. The two detectors do not see an excess at exactly the same mass: CMS sees one at 124 GeV, ATLAS at 126 GeV. That might be due to errors in mass measurements by at least one of the detectors, in which case further analysis could bring the two masses into line.

The other possibility is that they are both seeing flukes that happened to show up at nearly the same mass. “You have to carefully sift through different sources of uncertainties,” warns Landsberg, to figure out which answer is more likely.

When will we know whether the Higgs is out there?
More data will be needed. The LHC will start up again in late March or early April after its winter shutdown. CERN officials are still trying to decide whether to boost the energy of this year’s collisions from 7000 GeV to 8000 GeV. A decision could be announced as early as Friday, says Laurent Serin of the French (CNRS/IN2P3).

If the Higgs exists, collisions at the higher energy would produce more Higgs particles, making it easier to spot. Either way, the LHC will confirm or rule out the Higgs by the end of 2012, says Landsberg. “It’s a very exciting year, and hopefully a year from now I can point to discovery papers.”

References: ;

Update on 13 February: Vega launched successfully today from Kourou in French Guiana, reaching a circular orbit at an altitude of 1450 kilometres. It released the LARES laser relativity satellite, which will put Einstein’s theory of relativity to the test.

Original article, posted 8 February 2012

You don’t have to be big to challenge Einstein. A pocked ball just 36 centimetres wide is the latest space probe tasked with measuring general relativity, one of the cornerstones of modern physics.

The , or LARES, is a tungsten sphere with reflectors mounted in 92 holes punched into its surface. It is due to launch from Kourou, French Guiana, on a new European Space Agency rocket called , designed to cheaply launch payloads of less than 2500 kilograms. The launch window opens on 13 February.

LARES’s orbit will be tracked by bouncing ground-based lasers off the reflectors. General relativity states that gravity arises from the curvature of space and time. If this is true, Earth should drag space-time around with it as it spins, slightly perturbing the orbits of satellites.

Though general relativity is the accepted theory of gravity, it might break down if measured with greater accuracy. The beleaguered Gravity Probe B satellite achieved an accuracy within 19 per cent of the expected orbit change; earlier satellites got within 10 per cent. Researchers hope to achieve 1 per cent with LARES, built by the Italian Space Agency.

Hot spaceport

Expect to see more launches from the Kourou spaceport, which is ESA-owned, in future. Vega is due to launch an in 2014 to test technologies – such as a heat shield – for a possible crewed mission.

Vega could also launch small astronomy and climate satellites, says of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

One of the few other small launchers, McDowell says, is the troubled , built by US-based Orbital Sciences Corporation. It has had two failed launches of climate satellites in recent years – NASA’s Orbiting Carbon Observatory and Glory spacecraft.

Vega will help make the European spaceport in Kourou a destination for all kinds of launches, since the powerful Ariane 5 and medium-class Soyuz also launch from there. “It’s rounding out European space technology,” McDowell says. “They can compete across the board.”

Update (8 February 2012): A previous version of this story listed the LARES launch date as 9 February – ESA has revised the date to 13 February.

All eyes are on commercial space companies in the wake of the latest setback for Russia’s space programme, which has delayed the launch of the next crew to the International Space Station. A recent flight of a private rocket bodes well for the fledgling industry, but the coming weeks should reveal whether the industry can really take off.

Russia’s space agency Roscosmos reported last week that the Soyuz capsule meant to take astronauts to the station on 30 March sprang a leak when the air pressure inside it was accidentally pumped too high during a test. Another Soyuz capsule is being prepared for launch in its place but will not be ready to fly until 15 May.

It’s just the latest in a string of problems for Russian space vehicles. In August, for example, an uncrewed Soyuz rocket crashed to Earth. That temporarily threw the space station’s future into doubt because the same type of rocket is the only craft used to launch crews to the outpost.

NASA says it remains confident in Roscosmos’s ability to fly astronauts, but says the problems highlight the importance of developing other means of sending crews to the station. “The Soyuz is probably one of the most reliable systems out there, but when you have a spacecraft as significant as the ISS, it makes sense to get more than one capability to get humans [there],” Mike Suffredini, NASA’s space station manager, said in a teleconference last week.

Upcoming tests

NASA has previously estimated that commercial space taxis could be ready to carry astronauts in 2017. But the date will depend partly on how much money NASA can spend to help private companies develop their vehicles. NASA received $406 million for this purpose in 2012, but had asked for $850 million.

The White House will tip its hand about future spending priorities when it releases its proposed 2013 budget for federal agencies, including NASA, next Monday.

The companies already receiving NASA funding are also set to show their stuff. California-based SpaceX has been working towards launching a space capsule called Dragon on a mission to dock with the station. That launch will likely occur in early April, Suffredini said.

That Dragon capsule will be uncrewed, but SpaceX hopes to win a contract to fly astronauts to the station on later Dragon flights.

Suborbital trips

Orbital Sciences Corporation, based in Dulles, Virginia, which has a NASA contract to fly cargo to the station on a spacecraft called Cygnus, is farther from launch. It was scheduled to fly a demonstration mission to the station in April or May but will probably be delayed, Suffredini said: “We’re working on a number of options with them” for later flight dates.

However another private rocket company, , recently made its highest flight yet, flying its uncrewed STIG-A rocket just shy of the 100-kilometre boundary of space on 28 January.

The company hopes to reach space for the first time by mid-2012, and aims to develop a more powerful launcher to fly people on suborbital trips. The recent flight “tested many of the core technologies needed for the proposed manned reusable suborbital vehicle”, Neil Milburn of Armadillo .

Object type: Planet
Host: One star in a widely separated stellar pair
Fate: Doomed

Slipping through a rift in space-time à la Doctor Who, you are dumped onto the surface of a planet very much like Earth. It is night-time, and although the landscape looks familiar, it is eerily bright. Raising your gaze, you see why – a brilliant star blazes with the light of five full moons, giving everything around you a ghostly glow.

That’s not all. A chill runs down your spine when you see it: a massive, Jupiter-like planet looms above you, as large as the Earth’s moon. Bands of rippling clouds and whirling storms roil its surface. This is too close, you think, and you are right – you have arrived on your planet’s doomsday.

The gas giant is on a near-collision course with your planet, thanks to gravitational tugs between the planets in your system. Such tugs may have shifted the orbits of the outer planets in our own solar system billions of years ago – perhaps even kicking a now-lost world into the cold depths of space in the process.

Things will not end well for the planet you find yourself on. At least you would get a spectacular naked-eye view of your tormentor, says of the University of Cambridge. “If the intruder was a bright-ringed planet like Saturn, then those rings would be clearly visible,” he says.

The larger planet will hurl its smaller sibling into a much wider orbit, about 100 times as wide as Pluto’s, where it will go into a deep freeze. In a single-star system, that would normally be the end of the story. In binary star systems like this one, though, the stars will play pinball with the poor planet before losing it forever, according to simulations by Moeckel and , also at Cambridge.

No direction home

In their simulations, two sun-like stars orbit one another at between 250 and 1000 times the Earth-sun distance in our solar system, with one or both stars having its own set of planets. In many cases, the alien solar system becomes unstable and one of its planets is flung into a very wide orbit where it is vulnerable to being captured by the second star’s gravity.

Its new orbit around the second star tends to be very wide as well, and the first star often recaptures the planet, which can shuttle back and forth between the stars many times. The planetary pinball effect is surprisingly common in the simulations, with more than half of all ejected planets bouncing back and forth between the stars.

Could such situations actually come to pass? Observations suggest so. In recent years, evidence has grown that binary star systems can host planets, and observations suggest that planet formation is common around both tight and widely separated binary stars.

Out in the cold

The new simulations suggest the pinball planet may disturb or even eject other planets from both solar systems. Its own outlook is also bleak. In a small number of the simulations, it eventually wound up in a stable orbit around one of the stars. However, the vast majority of ejected planets eventually escape from both stars forever, voyaging into a permanent deep freeze.

“Once a planet starts transitioning back and forth, it’s almost certainly at the beginning of a trip that will end in deep space,” says Moeckel.

Journal reference: ; the work will be published in a future edition of

Read previous Astrophile columns: Picture yourself on a sandboard on Titan, How to spot a dark-matter galaxy , Glimpse elusive matter in shattering star, Cool echoes from galaxy’s biggest star, Stopped clocks deepen pulsar enigmas, Wounded galaxy is crux of cosmic whodunnit, Did comet killing spark Christmas light show?, Blinged-out stars were born rich, Supercritical water world does somersaults, Attack of the mystery green blobs, Undead stars rise again as supernovae, The sticky star cluster that’s mostly black hole, The rebel star that broke the medieval sky.