Finding massive planets is nothing new these days. But finding them orbiting each other instead of orbiting a star is unprecedented. An object initially thought to be a single brown dwarf is actually a pair of giant worlds. It’s not yet clear how this binary system formed, but the discovery may help redefine the line between planets and brown dwarfs – failed stars with tens of times the mass of Jupiter.

This pair of planets is made up of two balls of gas the size of Jupiter but almost four times more massive, separated by some 600 million kilometres, and slowly circling each other once per century or so. The young couple only emits light at infrared wavelengths, with residual heat from their formation, just 10 million years ago.

Observations with the 10-metre Keck II telescope, by a team led by William Best of the University of Hawaii, uncovered the binary system, with the help of adaptive optics that correct for the blurring effects of Earth’s atmosphere.

“This is a careful piece of work and a very nice discovery,” says David Latham of the Harvard-Smithsonian Center for Astrophysics.

Two planets, no sun

No one really understands the formation of rogue worlds that don’t orbit a star. So a binary system is even harder to understand, according to Gibor Basri of the University of California at Berkeley.

Gravitational interactions may slingshot single planets out of their solar systems, but the newly found pair of planets most likely formed from the fragmentation of a condensing protostar.

According to Alex de Koter of the University of Amsterdam, the discovery shows that various scenarios to produce free-floating planetary-mass objects are at work in the universe. Because they’re small and faint, they can only be discovered in our cosmic neighbourhood. This new find – called 2MASS J1119−1137 – is only 85 light years away, and the team thinks there may be many more similar planetary-mass binaries out there.

But are they really planets? Maybe not. In the past, the dividing line between planets and brown dwarfs was generally placed at 14 Jupiter masses, when nuclear fusion of deuterium in the object’s core sets in.

But Latham argues that the best way to distinguish between the two is not by their mass but by how they form: brown dwarfs result from collapsing clouds of gas and dust, while planets form out of a stellar disk.

‘The highest mass planets can be more massive than the lowest mass brown dwarfs,’ he says. ‘This binary is the nicest example that I know of for the overlap of planetary and brown dwarf masses.’

And if other brown dwarfs are similar – that is, if they’re not brown dwarfs at all but sneaky double bodies – we may have underestimated how many free-floating planets there are in our universe.

Journal Reference:

Secret destination

SOFIA is the world’s largest airborne observatory (Image: NASA)

The race is on. In a few hours, Pluto’s shadow will tear across Earth’s surface at 25 times the speed of a bullet. Our task: to manoeuvre a jumbo jet through the night sky so that it coincides with the shadow’s path at the point that will gives us the best view of an exceptional astronomical event. And the latest calculations suggest we are going to fall 332 kilometres short.

of the Lowell Observatory in Flagstaff, Arizona, appears worried by the news. “It’s an unexpectedly large shift.”

We are in , a converted Boeing 747SP that is the largest airborne observatory in the world. The re-fitters have clearly been busy: gone are the familiar rows of airline seats and overhead bins, ripped out to make room for a multitude of computer monitors – and a German-built 2.5-metre telescope. There are no flight attendants, no movies, no free whisky. I even had to bring my own food.

SOFIA is flying for a special reason. Tonight – 29 June – Pluto will pass in front of a star in the constellation Sagittarius. As it does so, the weak starlight that normally reaches Earth will fade and temporarily disappear. The event is called an “occultation“.

Astronomers can use this change in starlight to learn about the pressure and temperature at various altitudes in Pluto’s extremely thin atmosphere. “These measurements nicely complement the observations that NASA’s space probe New Horizons will carry out when it flies past Pluto on 14 July,” says SOFIA deputy programme scientist , who sits next to me at one of the consoles.

High speed shadow

Making the measurements isn’t easy, though. Earth’s orbital motion around the sun will take us through Pluto’s shadow at high speed – somewhere in the order of 85,000 kilometres per hour. The occultation will be over in just 90 seconds.

But SOFIA’s total flight time will be almost 8.5 hours. We took off from Christchurch International Airport in New Zealand late in the evening, . So far, most of the 30-plus scientists and engineers on board have spent the flight testing and calibrating their instruments – photometers that will measure the changing brightness of the star every second or so. I walk around and take pictures, although the rear of the cabin, where the most sensitive instruments are located, is forbidden territory.

The instruments of SOFIA’s telescope (Image: Govert Schilling)

Now, as midnight ticks by and SOFIA flies above the ocean somewhere between New Zealand and Antarctica, comes the news that has unsettled Dunham. Instrument scientist has been in contact with astronomer at the Massachusetts Institute of Technology to get the latest information on the precise location of the “central line” of the occultation, where astronomers hope to observe a flash of refracted starlight at mid-eclipse.

From ground-based measurements of Pluto’s position made just hours ago in Arizona and Chile, Bosh calculated that the central line lies 332 kilometres further north than had been thought. “I hope Amanda is right,” says Dunham.

Mission Director 2 Karina Leppik works out a new flight plan. Despite network problems, a lost memory stick and a printer that has run out of paper, it reaches Jeff Wilson, the navigator on the flight deck, in time. SOFIA changes course.

Rapid light show

Next comes what Roellig calls “the calm before the storm”, as SOFIA works its way towards the new interception point, eating up the night sky at 900 kilometres per hour. With little to do but wait, some people take a nap. Leppik plays an arcade game on her iPad.

A few hours pass, and the tension increases again. Then, as we approach 4:53 am, it’s all eyes on the computer screens. Pluto and the star already appear as one blob of light. Then, at the predicted time, the star starts to dim. “Amazing! This is so cool! ” exclaim scientists all around me.

żìĂš¶ÌÊÓÆ”s on SOFIA await their first measurements (Image: Govert Schilling)

The show lasts 90 seconds – and straight away, the analysis begins. A plot of brightness measurements made by the guiding camera of the telescope shows a beautiful central flash, indicating that SOFIA had been smack in the right place at the right time. The plot also reveals two intriguing short-duration blips. “In principle, they could indicate the presence of ring arcs around Pluto,” says Dunham – back in 1977, as a graduate student, Dunham had been part of the team that discovered the rings of Uranus during a stellar occultation. On this occasion, though, he thinks the blips are probably a spurious artefact.

For 15 minutes or so, I secretly hold the hope of having witnessed the discovery of a Plutonian ring system. But then data from one of SOFIA’s main instruments comes in, confirming Dunham’s hunch: there are no rings. There is another surprise, though: an indication of a possible sudden temperature change at a certain altitude in Pluto’s atmosphere. It’s too early to know what it might mean, says MIT astronomer .

One hundred minutes after the occultation, just before dawn, SOFIA touches back down at Christchurch airport. “Let’s make some history,” pilot Ace Beall had said as we took off. And we have done. But there’s more to follow on 14 July. Man, would I like to be on board New Horizons during its Pluto flyby.

Solitary Sedna (Image: NASA/JPL-Caltech)

Our sun is a thief. Over four billion years ago, it stole hundreds of frozen mini-planets from a passing star – and the peculiar planetoid Sedna is one of them.

With its extremely elongated orbit taking it 200 times further from the sun than Neptune every 11,400 years, Sedna has been a mystery ever since its discovery in 2003. Its nearest neighbours, the thousand-plus “ice dwarfs” that populate the Kuiper belt beyond Neptune, are believed to be the frozen remnants of our solar system’s formation.

But Sedna, and a dozen other objects with similarly wonky orbits, are harder to explain. A gravitational kick from a planet in our solar system could never have thrown them into such orbits.

One idea was that Sedna could have been jolted out of place by a passing star, but there was little evidence to back it up.

Now Lucie Jílková of Leiden Observatory in the Netherlands and her colleagues claim that the passing star wasn’t a trouble-maker but a victim: Sedna and its siblings were actually stolen from it when it ventured too close to the sun.

Using a low-cost, custom-built supercomputer, the team simulated over 10,000 possible encounters to find out which combination of a star’s mass, fly-by distance and velocity would lead to ice dwarfs being gravitationally captured into Sedna-like orbits.

They conclude that the passing star would have been 80 per cent more massive than the sun, and that it came as close as 34 billion kilometres – 51 times Neptune’s distance. The encounter probably took place when the sun was very young and still a member of a newly born star cluster.

You rob me, I’ll rob you

The passing star would itself have stolen hundreds of ice dwarfs from the sun’s Kuiper belt, and flung hundreds more into interstellar space.

Scott Kenyon of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who together with Ben Bromley of the University of Utah in Salt Lake City was one of the first to propose the idea, says the simulations are “pretty convincing”.

But Bromley points out that the orbits of Sedna-like objects show a persistent alignment that is hard to explain without the “shepherding” effect of a larger planet lurking in the outer solar system. Such a planet doesn’t seem to sit comfortably within the passing-star scenario.

“It remains to be shown that the massive shepherd – or its building blocks – could have survived the fly-by,” he says. “A big piece of the puzzle is still missing.”

If we could show that Sedna-like objects have a different chemical make-up from the rest of the Kuiper belt, that would be convincing evidence that they were stolen from another star. But as the first spacecraft to visit the Kuiper belt is only just about to reach Pluto after a nine-year journey, it may be a long time before the Sedna mystery is settled.

Journal reference:

Would the detection of gravitational waves from just after the big bang finally prove your theory of cosmic inflation?
If primordial gravitational waves were indeed detected by the BICEP2 telescope, they almost certainly would have been generated just after the big bang. But the media hyped this as the first evidence for inflation. That just isn’t true: there has been a lot of independent support. I don’t like the way gravitational waves are being treated as a smoking gun.

If we found no gravitational waves, it wouldn’t mean inflation is wrong. In many versions of the theory, the amplitude of the gravitational waves is miserably small, so they would not be detectable.

The BICEP2 team used an unpublished map of cosmic dust in the Milky Way to correct for dust in their results. Was this good science?
Criticising this is silly. You have to use all available data. If they had not used this information, that would have been bad science. Maybe, despite the dust correction, they were a bit over-optimistic, and claiming the discovery of gravitational waves may have been premature. But to the best of their knowledge at the time, it was unlikely that 100 per cent of that signal was due to Milky Way dust.

Many cosmologists say the results won’t stand the test of time. Do you agree?
I have no judgement about the likely outcome – nature can work either way. But it’s a pity that the debate is becoming a bit too emotional. I find the way in which the BICEP2 team has been attacked a bit shameful. At the end of the day, if we put our emotions behind us, everyone will gain.

Will the European Space Agency’s Planck satellite mission settle the debate?
In a few months, there will be a big data release from Planck. But there are rumours of an earlier publication of dust-related results – any time now. Planck and BICEP2 are very different experiments, so it will be hard to integrate the results, and even together they may not be 100 per cent conclusive. Most likely, other ground-based experiments are still necessary. But it’s a very important first step.

If the finding is verified, what would that mean for the theory of cosmic inflation?
It would be tremendously important, and rule out many versions of inflation. Also, by showing that the gravitational field isn’t smooth but quantised, like space itself, it would point toward a theory of quantum gravity, the long-sought reconciliation of general relativity with quantum mechanics.

These observations go back to when the universe was only 10-35 seconds old. Will we ever be able to explain the true beginning?
It’s absolutely possible. It took the universe 13.8 billion years to bring us here, and only a century ago did we discover that there’s more to it than our own Milky Way galaxy. Thirty years from now, we will have charted the most important features of the observable universe, like seafarers charted the Earth a couple of centuries ago. This is truly the age of the great cosmological discoveries.

This article appeared in print under the headline “Making cosmic waves”

What is happening with the Kepler space telescope?
After four years of successful operation, Kepler lost the second of its four reaction wheels in May 2013. It can’t be accurately pointed at the original field of view any more, so it hasn’t been collecting any new data. But we still have huge amounts of data to analyse – enough for another two or three years of discoveries. In fact, colleagues just announced they had found 715 exoplanets.

But you are still working on a K2 mission that will have Kepler collecting data once more.
Last summer, we asked the global astronomical community to suggest ways to use the crippled telescope to do valuable research. We received 42 proposals on extrasolar planets, galaxies, solar system science – everything you can name. Based on those proposals and the spacecraft’s abilities, we designed the K2 mission concept.

Would K2 cover all those things?
Obviously we won’t be able to do everything that was suggested, but K2 will be able to accomplish almost all of them. As for exoplanets, K2 won’t be able to do a long-term survey, but we will search for planets orbiting nearby red dwarf stars or stars bright enough to be visible to the naked eye. We hope to begin finding planets that are suitable for detailed follow-up studies with large ground-based telescopes.

How can you aim the telescope with only two of its reaction wheels still functioning?
We won’t regain the original pointing accuracy, but by reorientating Kepler in such a way that the minute pressure of sunlight is distributed evenly over the spacecraft, we can get pretty close. As deputy project manager Charlie Sobeck says, it’s a bit like stabilising a kayak upstream in a river.

In a sense, we’re using the pressure of sunlight as a third reaction wheel. To achieve this, Kepler has to be oriented more or less tangentially to its orbit, pointing to the plane which contains the 12 constellations of the zodiac and in which the planets orbit the sun. We know that this method works because the telescope recently spotted a known transiting exoplanet, WASP-28b.

What new possibilities does pointing the telescope in this way offer?
Some of the time the spacecraft will look away from our own Milky Way, which means we will be able to observe many more distant galaxies. Also, observing in the ecliptic will vastly increase the number of rocky asteroids and icy Kuiper Belt objects that can be studied.

It’s still up in the air whether Kepler will be kept alive for the K2 mission. Are you confident that NASA will give the green light?
A decision on funding the mission will be made between mid-May and early June. K2 will have to compete with other NASA astrophysical missions, but we think our chances are very high. This has been such an incredibly successful mission, and K2 is an extraordinary way to build on Kepler’s legacy. I’d give it a 150 per cent chance.

This article appeared in print under the headline “Down but not out”

Bright lights and sizzling sounds accompanied the fall of the meteorite on 27 October 1873 in the village of Diepenveen in the Netherlands, according to a contemporary handwritten note. Two witnesses to the fall dug up the small, warm stone and gave it to the local schoolmaster. It remained a school specimen until 2009, when it was given to a collector. Dutch amateur astronomer Henk Nieuwenhuis then “rediscovered” the 5-centimetre-wide space rock when he examined the collection last year.

“It is very unusual for a space rock to remain unnoticed by astronomers and geologists for such a long time,” says , a geologist at the Naturalis Biodiversity Center.

The Diepenveen, as the meteorite is now officially called, is only the fifth to have fallen in the Netherlands as far as we know. The find is all the more remarkable because the meteorite turns out to be of a very rare, carbon-rich type known as a CM carbonaceous chondrite – the same type as the one that triggered a meteorite hunt when it fell to Earth in California last year.

“CMs comprise less than 1 per cent of all known meteorites,” says geologist of the Free University in Amsterdam, where the Diepenveen underwent its first analysis.

CM carbonaceous chondrites contain up to 2 per cent carbon, often in the form of microscopic diamonds. They also contain organic matter like amino acids, which some researchers believe brought the building blocks of life to Earth.

“It is very interesting news,” says meteorite researcher of the University of Western Ontario in London, Canada. “CM meteorite falls are indeed rare. If the meteorite has been stored well and not subjected to too much terrestrial contamination it could be quite interesting.”

However, fellow meteorite researcher of NASA’s Johnson Space Center in Houston, Texas, is more cautious. “It will be thoroughly contaminated in any case, so only results for non-terrestrially occurring amino acids may be believable,” he says.

Tiny samples of the brittle and porous meteorite are now being studied at laboratories in California, New Mexico and Switzerland. “We hope to publish our analysis results sometime next year,” says Langbroek.

Brief and bright, fast and furious, uncommonly pure. Fast radio bursts have baffled astronomers since their discovery six years ago, but now they are revealing their true nature.

Two new studies suggest that FRBs are as common as dirt, that they produce more energy in a millisecond than the sun does in a million years, and that their single, intense flash of radio waves may be created when a neutron star is severed from its magnetic field as it collapses into a black hole. This explanation has also led to a more evocative name – blitzars – after the German word blitz for lightning.

In 2007, Duncan Lorimer and David Narkevic of West Virginia University in Morgantown discovered the first fast radio burst . Although many pulsars – spinning magnetic stars – give off brief periodic flashes of radio waves, the “Lorimer burst” was a singular event, lasting just a few milliseconds. What’s more, it seemed to originate a few billion light years away, much more distant than the furthest pulsars that we can detect, suggesting that it must be exceptionally powerful.

The plot thickened in 2012 when , now at the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleague .

Today Dan Thornton of the University of Manchester, UK, and colleagues have taken the total count to six in one fell swoop. In the journal Science, they report the discovery of four more FRBs using the 64-metre radio telescope in Parkes, Australia.

Sun outdone

With this many FRBs to observe, they were able to glean more details than previous studies did. The extent to which the radio waves are slowed by electrons in space reveals that they have travelled for billions of light years, confirming that FRBs are exceptionally powerful. The team concludes that they emit as much energy in a few milliseconds as the sun does in a million years.

Their comparative analysis also suggests that FRBs are frequent, with one being produced in every galaxy in the universe roughly every 1000 years. The fact that only six have been detected so far reflects their very short lifetime and the fact that astronomers can’t keep an eye on the whole sky all the time.

So what could give rise to an FRB? Several ideas have been put forward, including a collision between neutron stars – the ultradense, magnetic remains of supernova explosions – but most theories fail to explain why FRBs emit purely at radio wavelengths. Other energetic cosmic explosions shine across a much broader spectrum, including in visible light, x-rays and gamma rays..

But another study, posted online today, details a scenario that can account for this. of Radboud University in Nijmegen, the Netherlands, and of the Max Planck Institute for Gravitational Physics in Potsdam, Germany, suggest that an FRB occurs when the supernova explosion of a giant star leaves behind a compact neutron star that is slightly overweight.

Delayed collapse

The object’s own gravity would cause it to collapse into a black hole, the researchers say, if not for the centrifugal effect of its fast rotation. But within a few million years, the interaction of the neutron star’s magnetic field with the surrounding interstellar material slows the spin. Eventually, gravity wins and the star turns into a black hole after all.

“When the black hole forms, the magnetic field will be cut off from the star and snap like rubber bands,” explains Falcke. “This can produce the observed giant radio flashes.” By contrast, other types of radiation, which would come from the star itself rather than around it, cannot escape the gravitational collapse.

Thornton doesn’t want to comment on Falcke and Rezzolla’s idea before the paper has been accepted for publication in a refereed journal. “Our favourite explanation for FRBs is a giant burst from a magnetar – a highly magnetised type of neutron star,” he says. These explosions are expected to happen more or less as frequently as the mysterious radio bursts.

But Falcke and Rezzolla have already coined the term “blitzar” to describe FRBs.

Reference: , DOI: 10.1126/science.1236789; and