The reasons why stars twinkle are well understood. However, astronomers have been puzzled by why a few, but not all,quasars do something similar. A new explanation for this phenomenon still a long way from confirmed mayhave big implications for other areas of astronomy, from star formation to dark matter.

Quasars, or quasi-stellar objects, are the accretion disks around very active supermassive black holes in distant galaxies. Many have been observed to have slow fluctuations in brightness, but a small number change far more rapidly, in ways that cannot be attributed to variation in the quasars themselves. Instead, astronomers suspect that something in the line of sight between these quasars and Earth is getting in the way, but only erratically. The effect is similar to that seen when starlight is bent by variations in the temperature or density of the atmosphere.

However, the question of what it is that is doing the bending has remained a mystery, until a team of astronomers noticed that the fast-twinkling quasar PKS 1322-110 lies very close in the sky to the bright star Spica. Spica is only a 250 light-years away, while PKS 1322-110’s distance is measured in the billions of light-years. However,the light from PKS 1322-110 has to travel very close to Spica to get to Earth.

Dr Mark Walker of Manly Astrophysics, a charitably funded independent research entity, remembered that another small group of strongly twinkling quasars, J1819+3845, is similarly close to Vega in the sky. He thought this seemed an unlikely coincidence. Further investigation revealed that a third twinkler, PKS 1257-326, is within minutes of a degree of Alhakim, another, albeit less famous, hot star.

In a paper in the Astrophysical Journal,Walker and co-authors calculate that the chances of the twinkling quasars being so close to hot stars is less than one in 10million.

“We have very detailed observations of these two sources,” said co-author Dr Hayley Bignall of Australia’s CSIRO in a statement. “They show that the twinkling is caused by long, thin structures.” The authors conclude that hot stars that are A-type and brighter are surrounded by filaments of hydrogen gas that get ionized by the powerful ultraviolet radiation these stars put out.

We have seen these filaments around very old stars, such as in the Helix Nebula, where globules of gas the size of the Solar System and with long comet-like tails are observed. It had been thought that these globules were a product of the end of the stars’ lives, but the authors propose they exist much earlier in a star’s evolution, but only get illuminated so we can see them when the star reaches old age.

Bignall told IFLScience we still don’t know the source of these globules. They might be emitted by the star during formation, be associated with stellar winds, or form independently until being shaped by the star’s radiation. Most intriguingly, the paper raises the possibility that they represent a significant portion of the galaxy’s mass, possibly partly explaining the nature of dark matter.

The authors think very hot stars may have filaments extending out as far as sixlight-years, further than the distance between the Sun and the nearest stars. Bignall added that patches of hydrogen this size are so hard to detect, it is not surprising we have not seen them until now, but this won’t stop the team trying to find ways to confirm their existence.

Read more: http://www.iflscience.com/space/why-do-quasars-twinkle-the-answer-may-lie-around-hot-stars/

The search for mysterious fast radio bursts very brief but intense pulses of radio waves from outer space is heating up. Nobody knows what causes these powerful bursts, but some have even speculated that the signals could be transmitted by distant alien civilisations. In fact, astronomers are so perplexed by the phenomenon that it is driving a renaissance in radio astronomy.

Now an international team of astronomers has detected the brightest ever fast radio burst. Dubbed FRB 150807 after its discovery date, the burst of intense radio waves lasted less than half a millisecond that is 0.1% of the time it takes a human to blink. And the study, published in Science, has come closer than any before it to pinning down where the blip came from. The research comes just days after another study reported having seen a fast radio burst together with an outburst of gamma rays, extremely energetic electromagnetic radiation.

Despite their intensity, the nature and origin of fast radio bursts is still hotly debated. Some astronomers have suggested these brief, intense flashes are flares produced in the atmospheres of certain stars in our own Milky Way galaxy a process similar to solar flares. Others argue they are caused by cosmic collisions such as a neutron star (a collapsed core of a large star) colliding with a black hole in a distant galaxy, or speculated that they could be alien signals.

^{Huge flare from small star. NASA’s Goddard Space Flight Center/S. Wiessinger}

The first fast radio burst the Lorimer burst was discovered serendipitously by radio astronomers using Australias Parkes telescope to search for pulsed radio emissions from spinning neutron stars called pulsars. The Lorimer burst remained a curiosity until other fast radio bursts at different positions in the sky were discovered by other telescopes such as the giant Arecibo radio telescope in Puerto Rico and the 100-metre Greenbank dish in the US.

But progress in understanding this enigmatic phenomenon has been slow. This is partly down to the short duration of the bursts, the limited resolution provided by the telescopes and the uncertainty of the sky positions of the bursts. Trying to discover a burst and, at exactly the same time, pinpoint accurately where in the sky it comes from is difficult. If a radio signal could be backed up by telescopes that are searching for other kinds of electromagnetic radiation (such as X-rays or the kind of optical light that we can see), we could measure the distance and understand the physics processes driving these events. If the processes driving these bursts are similar to those responsible for other cosmic explosions, such as gamma ray bursts, astronomers suspect that radiation at other wavelengths is likely to be emitted in the same event that caused the fast radio bursts. But its proven difficult to catch.

Indirect estimates of distances have been made by measuring how the radio signal is smeared out. This can help infer the amount of material the light has travelled through. From this, the distance of the fast radio burst from Earth can be estimated, using a variety of assumptions such as the amount of matter between us. Such measurements have indicated that the origins of fast radio bursts lie far beyond our galaxy.

Tracing the blip

FRB 150807 is remarkable for its short duration, radio brightness and high degree of linear polarisation a property describing the plane of the vibrations that make up the waves. Combining these properties, the new study suggests that the burst occurred in a galaxy over a billion light years away, identified by the Visible and Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey. This is the closest weve ever got to pinpointing where a fast radio burst came from.

The polarisation of light is affected by magnetic fields surrounding it. So knowing that helped the researchers estimate the magnetic properties of the plasma through which the radio waves travelled. Their analysis suggests that theres only negligible magnetisation of plasma close to the burst site. Interestingly, if this is correct, it would rule out strongly magnetised objects such as young neutron stars, magnetars or other objects causing it favoured models so far.

^{Artists impression of the 5km diameter central core of antennas of the Square Kilometre Array, which will help shed light on fast radio bursts. Swinburne Astronomy Productions for SKA Project Development}

This study shows that as the small number of recorded fast radio bursts grows and their properties become better known, the exciting prospect of understanding what produces them becomes increasingly feasible. They could also be used to map out the magnetic fields in the universe something we know little about. The next breakthrough may come with the first detection of a visible counterpart or optical afterglow, from which we can measure an accurate distance.

It may happen sooner than you think, given the other recent studys tantalising report of possibly the first detection of a gamma-rays burst coinciding with a fast radio burst with NASAs Swift satellite. If the two bursts do indeed come from the same source that would be very exciting it could mean this source is lot more energetic than we had anticipated.

Analysis of FRB 150807 predicts that these events should not be rare with 190 occurring across the sky per day. Future facilities such as the Large Synoptic Survey Telescope which will survey the entire night sky every few days at optical wavelengths and the radio equivalent and the Square Kilometre Array will revolutionise our view and understanding of these mysterious blips and the violent, ever-changing universe in which they live.

Carole Mundell, Head of Physics, University of Bath

This article was originally published on The Conversation. Read the original article.

Read more: http://www.iflscience.com/space/are-aliens-trying-to-tell-us-something-brightest-burst-of-radio-waves-detected/

It’s just a little bit more than a year until NASA’s New Horizons will fly past 2014 MU69, its next target, and astronomers are combing the data to understand as much as possible about the object before the fateful encounter.

Just a few months ago, NASA announced that MU69 might actually be two objects orbiting really close to each other, or one peanut-shaped object, and a new analysis suggests that it might have a small moon. Over the summer, the space rock passed in front of a star and researchers used this event, called occultation, to learn more about MU69.

“We really won’t know what MU69 looks like until we fly past it, or even gain a full understanding of it until after the encounter,” New Horizons science team member Marc Buie, of the Southwest Research Institute, Boulder, said in a statement. “But even from afar, the more we examine it, the more interesting and amazing this little world becomes.”

The data suggesting a potential moon come from the Stratospheric Observatory for Infrared Astronomy (SOFIA), a telescope mounted inside an airplane. SOFIA observed the object on July 10 and among the observations, there was a “blip” in starlight. Analysis showed that the blip was another object around MU69.

“A binary with a smaller moon might also help explain the shifts we see in the position of MU69 during these various occultations,” Buie added. “It’s all very suggestive, but another step in our work to get a clear picture of MU69 before New Horizons flies by, just over a year from now.”

New Horizons has already recorded the most distant flyby on record when it flew past Pluto in 2015, and it will surpass that on January 1, 2019, when it reaches MU69, 6.5 billion kilometers (4 billion miles) from Earth. MU69 is estimated to be around 30 kilometers (20 miles) long.

“The occultation effort that Marc Buie and his team led for New Horizons has been invaluable in opening our eyes to the very real possibilities that MU69 is both a lot more complex than anyone suspected, and that it holds many surprises for us at flyby on New Year’s Eve and New Year’s Day, 2019,” added New Horizons Principal Investigator Alan Stern, also from the Southwest Research Institute. “The allure of its exploration is becoming stronger and stronger as we learn more and more about it. It’s just fantastic!”

While 2019 is getting closer, you can tide yourselves over by voting for a nickname for MU69.

Read more: http://www.iflscience.com/space/new-horizons-next-target-might-have-a-moon/

An international group of astronomers has used two of the worlds largest telescopes to create the most detailed map yet of the distribution of hydrogen in our galaxy.

The project, called HI4PI, required more than 1million individual observations of the sky and about 10 billion data points. Although hydrogen is the most abundant element in the universe and the main component of stars, it is detectable only viaradio waves, where theres plenty of interference from devices like mobile phones and broadcast stations.

Besides a careful calibration of the data, we also had to remove man-made noise from the data, explains Benjamin Winkel oftheMax Planck Institute for Radio Astronomy in Germany, and part of theHI4PI project,in a statement.This so-called radio frequency interference (RFI) is, for example, produced by telecommunication and broadcast stations, or military radarand pollutes the faint emission of the astronomical sources. The computational effort for the data processing was huge, adding to the thousands of hours of observations [and] thousands of hours of computing time.

The map shows the filaments and regions of neutral hydrogen, with the colors reflecting the movement of the gas: that moving towards us is purple/blue, while that moving away from us is orange/green. The brightness traces its amount, and in the lower corner it is possible to see the Large and Small Magellanic Cloudstwo of the Milky Way’s neighboringgalaxies.

The data is going to be publicly available and freely accessible, withtheir findings tobe published in the journalAstronomy & Astrophysics. Among those findings, theres the discovery of fine structures between the stars of the Milky Way.

Pilot studies of the HI4PI data show a wealth of filamentary structures never seen before, said co-author Professor Lister Staveley-Smith, from the International Centre for Radio Astronomy Research, in a separatestatement.Tiny clouds become visible that appear to have fuelled star formation in the Milky Way for billions of years. These objects are too dim and too small to be detected even in the other galaxies closest to us.

The project will also help with extragalactic observations.

Like the clouds at the sky, all observations we receive from the distant universe have to pass through hydrogen in our own Milky Way, said Winkel.The HI4PI data allows us to correct accurately for all these hydrogen clouds and clean the window we are watching through.

Read more: http://www.iflscience.com/space/astronomers-produce-detailed-map-of-hydrogen-in-the-milky-way/