NuSTAR discovers impossibly bright dead star - First ultraluminous pulsar

High-energy X-rays streaming from a rare and mighty pulsar (magenta), the brightest found to date, can be seen in this new image combining multi-wavelength data from three telescopes. 

The bulk of a galaxy called Messier 82 (M82), or the 'Cigar galaxy,' is seen in visible-light data captured by the National Optical Astronomy Observatory's 2.1-meter telescope at Kitt Peak in Arizona. 

Starlight is white, and lanes of dust appear brown. Low-energy X-ray data from NASA's Chandra X-ray Observatory are colored blue, and higher-energy X-ray data from NuSTAR are pink. 

Credit: NASA/JPL-Caltech/SAO/NOAO

Astronomers working with NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), led by Caltech's Fiona Harrison, have found a pulsating dead star beaming with the energy of about 10 million suns.

The object, previously thought to be a black hole because it is so powerful, is in fact a pulsar, the incredibly dense rotating remains of a star.

"This compact little stellar remnant is a real powerhouse. We've never seen anything quite like it," says Harrison, NuSTAR's principal investigator and the Benjamin M. Rosen Professor of Physics at Caltech.

"We all thought an object with that much energy had to be a black hole."

Dom Walton, a postdoctoral scholar at Caltech who works with NuSTAR data, says that with its extreme energy, this pulsar takes the top prize in the weirdness category. Pulsars are typically between one and two times the mass of the sun.

This new pulsar presumably falls in that same range but shines about 100 times brighter than theory suggests something of its mass should be able to.

"We've never seen a pulsar even close to being this bright," Walton says. "Honestly, we don't know how this happens, and theorists will be chewing on it for a long time."

Besides being weird, the finding will help scientists better understand a class of very bright X-ray sources, called ultraluminous X-ray sources (ULXs).

Harrison, Walton, and their colleagues describe NuSTAR's detection of this first ultraluminous pulsar in a paper that appears in the current issue of Nature.

"This was certainly an unexpected discovery," says Harrison. "In fact, we were looking for something else entirely when we found this."



This animation shows a neutron star, the core of a star that exploded in a massive supernova. 

This particular neutron star is known as a pulsar because it sends out rotating beams of X-rays that sweep past Earth like lighthouse beacons. 

Credit: NASA/JPL-Caltech

Earlier this year, astronomers in London detected a spectacular, once-in-a-century supernova (dubbed SN2014J) in a relatively nearby galaxy known as Messier 82 (M82), or the Cigar Galaxy, 12 million light-years away.

Because of the rarity of that event, telescopes around the world and in space adjusted their gaze to study the aftermath of the explosion in detail.

Besides the supernova, M82 harbours a number of other ULXs. When Matteo Bachetti of the Université de Toulouse in France, the lead author of this new paper, took a closer look at these ULXs in NuSTAR's data, he discovered that something in the galaxy was pulsing, or flashing light.

"That was a big surprise," Harrison says. "For decades everybody has thought these ultraluminous X-ray sources had to be black holes, but black holes don't have a way to create this pulsing."

More information: An Ultraluminous X-ray Source Powered by An Accreting Neutron Star, Nature, dx.doi.org/10.1038/nature13791189

NASA Kepler: The impossible triple star KIC 2856960

Credit: ESO/M. Kornmesser

There's news this week of an "impossible" triple star system recently discovered by astronomers.

One that "defies known physics."

Needless to say, there's no need to abandon physics quite yet.

It all comes from a new paper being published in MNRAS titled "KIC 2856960: the impossible triple star." Despite the overly-hyped title, it is interesting work.

It's based upon data gathered from the Kepler satellite, which looked at the brightness of stars over time looking for exoplanets.

Kepler finds exoplanets via the transit method, where the brightness of a star can be seen to dip when a planet passes in front of it but the method can also be used to study multiple star systems if they happen to have the right alignment.

Just as a planet can cause a star to dip in brightness when it passes in front, one star passing in front of another can have a similar effect.

The team looked at the data from KIC 2856960, for which Kepler gathered data over 4 years. In the data we see a small dip in brightness about 4 times a day, and a larger dip every 204 days.

From this, it looks like a close binary of smaller stars (with orbital periods of 0.26 days) orbiting a third star with a period of 204 days.

So it is a fairly common triple star system. Not a big deal, move on to other data.

But this team wanted to determine some of the characteristics of this system, such as their exact orbits and masses, so they looked at the data in more detail.

Determining the details of a system can be tricky. There are all sorts of things that can add to noise in your data, such as starspots and other stellar activity.

This is why exoplanets are divided into confirmed planets and candidate planets. Once you've eliminated the noise you can, you try to match the observed fluctuations to particular orbits, and then see if those orbits are stable. Sometimes the results can be deceiving.

What the team found was that the more they looked at the data for KIC 2856960, the more confusing things got.

At first glance it looks like a triple star system, but when they tested candidate orbits, none of them seemed to fit.

Several of them kind of fit, but there was always some unexplained fluctuation in the data. So the team tried other models, and found a 4-star system that basically worked, but it required the orbits one binary system to be in exact resonance with the other, which seems highly unlikely.

In other words, the Kepler data is inconclusive. It could be a strange 4-star system, or it could be a triple-star system with something else buried in the data. We can't be certain at this point.

This does not make KIC 2856960 an "impossible" system. There's no evidence that it is defying known physics, just that the data is odd and we don't understand it and that in itself makes it interesting. It is clear that this system is not a simple, boring triple system.

It's a mystery at the moment, but it's a mystery that could be solved with more work and more data. And that makes it a mission possible.

More information: T. R. Marsh, et al. "KIC 2856960: the impossible triple star." MNRAS (2014) arxiv.org/abs/1409.0722

ESO VLT: Weird Quantum Tunneling Enables 'Impossible' Space Chemistry

Chemical reactions thought to be impossible in space because of the extremely low temperatures there are actually happening often. 

In a July 2013 study, researchers suggest a strange phenomenon called quantum tunneling is the explanation.

CREDIT: ESO. Acknowledgement: VPHAS+ Consortium /Cambridge Astronomical Survey Unit

A weird quirk of quantum mechanics is allowing a chemical reaction thought to be impossible to occur in cold gas in outer space.

In the harsh environment of space, where the temperature is about minus 350 degrees Celsius (minus 210 degrees Fahrenheit), scientists had thought a certain reaction involving alcohol molecules couldn't take place, because at such low temperatures, there shouldn't be enough energy to rearrange chemical bonds.

But surprisingly, research has shown that the reaction occurs at a rate 50 times greater in space than at room temperature.

Now, by simulating the conditions of space in a laboratory, scientists have found a possible explanation for how the reaction occurs: quantum tunneling.

Tunneling depends on the odd rules of quantum mechanics, which state that particles don't usually have decided states, positions and speeds, but exist in hazes of probability.

This means that a particle might have a strong probability of being located on one side of a wall, but still retain a very small chance of actually being on the other side of it, allowing it, occasionally, to "tunnel" through a wall that would otherwise be an impassable barrier.

This tunneling ability might allow particles to undergo chemical reactions that should be impossible due to the lack of energy at the low temperatures of space.

Dwayne Heard

"The answer lies in quantum mechanics," chemist Dwayne Heard of the University of Leeds in the U.K., who led the research, said in a statement.

"Chemical reactions get slower as temperatures decrease, as there is less energy to get over the 'reaction barrier.' But quantum mechanics tells us that it is possible to cheat and dig through this barrier instead of going over it. This is called 'quantum tunneling.'"

Quantum tunneling states last only very, very briefly, making reactions taking advantage of them difficult but that's where the cold temperature might help, because some molecules formed during the reaction process might be transient at room temperature, but last slightly longer at very cold temperatures.

"We suggest that an 'intermediary product' forms in the first stage of the reaction, which can only survive long enough for quantum tunneling to occur at extremely cold temperatures," Heard said.

In a lab, Heard and his colleagues created the same cold conditions in space, and observed reactions of the alcohol methanol with an oxidizing chemical called a hydroxyl radical, and found that these gases react to create methoxy radicals.

Now, the scientists want to test other types of alcohol-related reactions under similar conditions.

"If our results continue to show a similar increase in the reaction rate at very cold temperatures, then scientists have been severely underestimating the rates of formation and destruction of complex molecules, such as alcohols, in space," Heard said.

The findings were published online June 30 in the journal Nature Chemistry.