Swift has been keeping a close eye on the possible supernova (Image: NASA/GSFC)

The supernova world has a new brightness champ. A supernova discovered on 14 June appears to shine more than 400 billion times brighter than the sun would if they sat next to each other.

An ordinary supernova usually marks the death of a massive star, but a so-called superluminous supernova shines at least 10 times brighter and has more mysterious origins. The newly found explosion, called ASASSN-15lh, is at least 2.5 times brighter than any superluminous supernova seen before.

The (ASAS-SN), a suite of automated 14-centimetre telescopes that scour the sky for stellar explosions, discovered the bright object in the southern constellation of Indus.

Over the next few weeks, Subo Dong of The Kavli Institute for Astronomy and Astrophysics at Peking University in Beijing, China, and colleagues looked toward the supernova with several larger telescopes to determine how far away it is, what its peak brightness was and to check that it was indeed a supernova. NASA’s Swift space telescope also started observing it in ultraviolet light on 30 June.

Dong’s team found that the supernova was discovered nine days after its peak brightness, and that its light took more than 2.8 billion years to get to Earth. That means its luminosity is about 100 times brighter than normal supernovae and several times higher than any previous superluminous supernova found. The team posted a summary of their observations on website on 8 July.

Classification confusion

Not everyone is convinced that ASASSN-15lh is a superluminous supernova, however. “We don’t even really know that this is a supernova,” says of San Diego State University in California, who .

That’s because this blast’s light has only just started to lessen. As it fades, it will reveal more information about the explosion, which will help to confirm ASASSN-15lh’s true nature. But this will take time: extra bright supernovae take about 100 days to fade, a few times longer than regular supernovae.

Quimby points out that some objects can initially look like superluminous supernovae, but turn out to be something else. The most common impostors are stars that pass too near a black hole and get ripped apart. “Or we’ve got some new class of objects,” he adds. “That could be even more exciting.”

If it is a superluminous supernova, observing it could help illuminate a different kind of burst. Some astronomers are investigating a connection between these supernovae and huge blasts of gamma rays that signal the end of a massive star’s life, called gamma-ray bursts. A recent study further connects a superluminous supernova to a gamma-ray burst that shone for hours – adding more fuel to the idea’s bright fire.

References: ;

Update, 14 June 2015: Dong’s team have now

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The image of SN 1987A as observed by Hubble from 1995 to 2006 (Image: NASA)

STARGAZERS’ favourite explosion, a supernova known as SN 1987A, is starting to lose its lustre. It first appeared in 1987, and is prized by astronomers because it lies close enough to Earth to study in detail.

The blast’s shock wave lights up matter kicked out by the original star before it exploded. Some 15 years ago, it started colliding with 30 clumps of dense material that ring the blast site. This makes them shine like a necklace of pearls, but also destroys them, says of Stockholm University, Sweden.

His team examined images from the Hubble Space Telescope and the Very Large Telescope in Atacama, Chile, taken between 1994 and 2014 and found that the pearls along 1987A’s ring have begun fading, which means the shock wave has passed through. Fransson says the ring will vanish between 2020 and 2030.

But it’s not the end for 1987A. The team also found scattered bright spots outside of the ring, suggesting the supernova is lighting up previously unseen material. Studying these clumps could reveal more about the explosion’s origins ().

This article appeared in print under the headline “Famous supernova begins to fade”

A band of massive stars may have blown enormous smoke rings in Orion. A new three-dimensional map of one of the most well-studied regions of the constellation has uncovered a giant dust ring that has astronomers baffled.

The Orion nebula complex is a huge star-forming region of dust and gas about 1350 light years from Earth. It is centred on the famous constellation, but covers areas outside it as well. Eddie Schlafly of the Max Planck Institute for Astronomy in Heidelberg, Germany, and his colleagues used observations from Hawaii’s Pan-STARRS telescope and a 3D analysis technique to get a more detailed view of the dust in this region.

The group analysed the colours of some 23��million stars in a roughly 1,000-square-degree region of sky in the Orion constellation in order to measure the temperature and brightness of the stars, which reveals their distances from us.

Intervening dust can redden stars’ colours, so by comparing the distances, colours and brightnesses of those stars, the team could work out when dust lay between the stars and Earth or when it lay beyond the stars. “We’re using all those stars simultaneously to figure out how much dust there is close, how much dust there is at the distance to Orion, and how much dust there is farther away,” says Schlafly.

Rare ring

This technique allowed them to create a 3D map of the region, and a pattern stood out: a dust ring some 330 light years wide that includes the major star-forming regions in Orion.

The team thinks that massive stars, which spew enormous amounts of energy, carved a giant bubble in the region’s gas and dust, pushing dust to the edge of that bubble to appear as a ring. These stars drained their energy reserves in just 10 to 15 million years and have since burned out.

To test that idea, Schlafly wants to find the dead stars’ prodigal siblings. Those massive stars would have had many low-mass companions that should still be alive and have since wandered from their nursery. The astronomers hope to use upcoming data from the European Space Agency’s Gaia satellite to find those companions and trace their movements back millions of years, says Schlafly. “If they all form a nice, beautiful clump at the centre of the ring, that would be a really spectacular confirmation that this picture is correct.”

Journal reference:

William Ditto and his colleagues at the University of Hawaii, Manoa, compared the two strongest oscillations, or tones, made by the variable star KIC 5520878, using observations by NASA’s Kepler space telescope. They noticed that dividing the frequency of the secondary note by that of the primary, or lowest, note gives a value near the “golden ratio” – a number that shows up often in art and nature and is close to 1.618.

They then realised that its frequencies exhibited a fractal pattern: separating the tune into its constituent parts yielded more frequencies at weaker strengths, similar to the way coastlines retain their complexity as you zoom in. Three other pulsing stars with “golden” ratios also showed fractal patterns, while two non-golden stars did not. This could mean the golden songs could reveal insights into stellar physics.

Astronomers who study pulsating stars aren’t convinced the golden ratio finding is significant, however. “The fact that this period ratio (or its reciprocal) lies close to the golden ratio may be a coincidence,” says Robert Szabo of Konkoly Observatory in Hungary, “and in my opinion, more evidence is needed to demonstrate that it has a privileged role in the dynamics of [these] stars.”

Journal Reference: Physical Review Letters, in press (arXiv.org/abs/1501.01747)

The four spots of light around the bright galaxy blob in the middle all come from the same exploding star (Image: Patrick L. Kelly et al (arXiv:1411.6009 [astro-ph.CO]))

Seeing quadruple? For the first time, astronomers have seen an image of a single supernova split into four by a gravitational lens. The splintered stellar explosion may help calibrate distances across the universe.

Gravitational lenses are the result of massive celestial objects, like stars, galaxies or even dark matter, bending light as it passes near them. Sometimes gravitational lenses produce multiple images of a single object behind them. The effect is similar to looking at a candle through the base of a wine glass.

Exactly 50 years ago, Norwegian astrophysicist that if astronomers can find a supernova whose light had been bent in several directions by a gravitational lens, that might tell them how quickly the universe is expanding. Each image takes a different path to telescopes near Earth, depending on how much mass is in the way. The differences in the time it takes each image to reach Earth is proportional to the universe’s expansion rate.

Despite decades of searching, no such stellar explosions had turned up. But now, Patrick Kelly at the University of California, Berkeley and his colleagues say they’ve found one.

The MACS J1149.6+2223 galaxy cluster (Image: NASA, ESA, and M. Postman (STScI), and the CLASH team)

The supernova appeared in images of the galaxy cluster taken on 10 November by the Hubble Space Telescope. Around one of the giant galaxies in the cluster, the researchers saw the smeared arcs of a distorted, smaller spiral galaxy behind it. Embedded within those smears were four bright light sources. The wavelengths of the light in those arcs suggest a single origin, the same distance from Earth, meaning the bright light sources are probably all images of the same star within the spiral galaxy. Because the object did not appear in earlier images of the same galaxy cluster, the researchers think it is the bright, fatal explosion of a supernova.

“This is a fantastic discovery,” says at the University of Tokyo, Japan. “The authors make a good case that this is a supernova seen through a gravitational lens.”

Universal speed-up

Supernovae come in several varieties, but one kind, called a type Ia, has been an important tool for astronomers. These explosions put out nearly the same amount of light, no matter where in the universe they occur. So when scientists find a type Ia supernova, they can tell how far away it is by how much of this light makes it to Earth, or how bright it appears. These supernovae revealed to astronomers in the late 1990s that the universe’s expansion is speeding up – a discovery that received the 2011 Nobel prize in physics.

Kelly’s team doesn’t yet know what kind of supernova they found, but it could help put the strongest limits yet on cosmological parameters if it is. Because the images all come from the same supernova, comparing their time delays would give a more precise value of the supernova’s actual brightness than any distant type Ia supernova measured yet. That value would help them better gauge distances to all such blasts across the universe, and pin down the universe’s expansion rate.

It can also give an estimate of the mass of the lensing galaxy or cluster, and help map the distribution of matter in the cluster, says Brian Schmidt of the Australian National University, one of the 2011 Nobel laureates. That could give astronomers a bead on the nature of dark matter. “We can see if dark matter and atoms are distributed as expected,” he says. “Seriously cool discovery!”

Journal Reference: ArXiv: arxiv.org/abs/1411.6009, submitted to Science

Galaxies like to keep their distance – 30 million light years of it, to be precise. An analysis of thousands of galaxies finds that they are strung like pearls on a necklace, even on relatively small scales.

On large scales, the universe is comprised of empty voids, punctuated by narrow, winding filaments of dark matter that guide the growth of galaxies and galaxy clusters. This cosmic web, which has taken decades to map, holds a repeating pattern on the order of hundreds of millions of light years.

But when you zoom in, things were supposed to get messier. Now, and his student Maarja Bussov at Tartu Observatory in Estonia and their colleagues have found a small-scale pattern in cosmic structure.

Tempel initially assigned the project to Bussov as a student exercise, “to learn a technique”, he says. The pair started with observations of 588,193 individual galaxies and 82,458 groups containing at least two galaxies, from the Sloan Digital Sky Survey. The galaxies were up to about 2 billion light years away.

The pair wrote an algorithm to identify the ones that lie within 1.5 million light years of a filament in the large-scale cosmic web. That turned up 68,373 galaxies and 35,158 groups residing within relatively narrow cylinders.

Spaced out

When they compared the distances between those individual galaxies and groups, they got a surprise: these cosmic objects tended to lie either about 30 million light years, or less frequently, about 18 million light years from each other.

“I had small hope that something interesting might come out,” Tempel says. “I did not expect to discover anything like this.”

The more obvious 30 million light year separation that Tempel and colleagues saw could be a result of how galaxies grow, says Tempel. A forming galaxy can gravitationally gather material within a certain distance – but any matter that’s farther away is unattainable. Galaxies near one another can congregate together to form a cluster, again because of gravity.

Dark energy, a strange substance that opposes gravity, also affects the galaxy growth process and may serve to help keep galaxies apart. Previous research suggested that studying the details of how galaxies clump could help untangle the nature of the mysterious substance.

Cosmic evolution

The researchers stress that this is just one possibility, though, and they still don’t have an explanation for the 18 million light year pattern. They plan to run simulations to investigate further.

Not all astronomers are convinced the smaller separation pattern is real. , a theorist at New Mexico State University in Las Cruces who works with supercomputer simulations of cosmic evolution, suggests the small scaling pattern is a result of the way Tempel and his colleagues chose the galaxies to analyse, restricting them to falling within 1.5 million light years of a filament. “This right away gives a ‘typical scale’ of 15 million to 18 million light years without actually having one in the data,” he says

The next step is to search for the pattern at greater distances. The light reaching us from objects farther away from Earth shows galaxies as they were farther back in time, so studying galaxies and clusters at greater distances can help investigate how this characteristic scale evolves during the lifetime of the universe, says Tempel.

Journal reference: Astronomy & Astrophysics,

When the Rosetta spacecraft sends its lander to the surface of a comet on 12 November, the lander will follow pre-arranged orders from Earth to touch down safely and send data home for analysis. But future spacecraft may be able to do it all on their own.

and her colleagues at the Jet Propulsion Laboratory in Pasadena, California, have developed software that can identify a plume of water or vapour on a celestial body’s surface, with the goal of directing another instrument to make follow-up observations.

Comets, asteroids and icy moons have all shown signs of venting plumes into space. But because these bodies are far from Earth and the jets are not always active, exploring them remotely is challenging. “The more the spacecraft can do without waiting for communication with Earth, the better they can explore – especially when they encounter activity that may be short-lived or only within viewing range for a short time,” Wagstaff says.

The researchers tested the software on unprocessed images of comet Hartley 2 and Saturn’s moon Enceladus. “We want to replicate what the instrument sees,” says team member . The program looks for bright material outside the limb of the moon or comet, checks that the material meets up with the surface and is larger than a minimum size, and then determines if it is seeing a plume.

Wagstaff thinks an upcoming Europa orbiter mission would be a great opportunity to use this technology. But the software will be of even more benefit on future missions to the outer solar system and, eventually, planetary systems outside our solar system. “That will have to have to be an entirely autonomous operation,” she says.

Journal reference: The Astrophysical Journal, DOI: