Stunning Pinwheel Nebula Is a Cosmic Cataclysm in the Making

(THIS ARTICLE IS COURTESY OF GIZOMODO SCIENCE SITE)

 

Stunning Pinwheel Nebula Is a Cosmic Cataclysm in the Making

Apep, the first Wolf-Rayet star system to be discovered in the Milky Way.
Image: ESO/Callingham et al.

This image of a dusty, gas-rich nebula looks pretty, but appearances can be deceiving. Known as a Wolf-Rayet star system, it’s poised to unleash a catastrophic gamma-ray burst when it finally goes supernova. What’s remarkable about this particular Wolf-Rayet system, however, is that it’s the first to be discovered in our own galaxy. Cue the ominous music…

This Wolf-Rayet star system is formally known as 2XMM J160050.7-514245, but to the researchers who recently investigated this enigmatic object, it’s simply “Apep”—an exotic object named for the serpentine ancient Egyptian god of chaos. In a press release, Joseph Callingham, the lead author of the new study and an astronomer at the Netherlands Institute for Radio Astronomy (ASTRON), said “it’s the first such system to be discovered in our own galaxy”—a system he never expected to find “in our own backyard.” The details of this research were published today in Nature Astronomy.

Indeed, astronomers have observed Wolf-Rayet stars before, but only in other galaxies. These massive star systems are on the verge of entering into their death throes, at which time they’ll generate a type of supernova that emits an extremely powerful and narrow jet of plasma—the dreaded gamma-ray burst.

Apep is one such gamma-ray progenitor system, featuring a massive triple star system at its core—a binary pair and a lone star—and vast spiral arms composed of gas and dust. The system is located around 8,000 light-years from Earth, which is uncomfortably close given its explosive potential.

“This was a very fun project to do in some ways, in the sense that Joe found this object and first showed it to me in 2012 when we were officemates as undergrads in Sydney—and it took us six years to gather all the data to reveal this surprising story,” Benjamin Pope, a NASA Sagan fellow at New York University’s Center for Cosmology and Particle Physics and a co-author of the new study, told Gizmodo. “Sometimes science is slow! But I remember when last year, the day before my PhD defense in Oxford, he was visiting and showed me the picture of the Apep spiral—I literally gasped, it was so shocking. There’s really nothing quite like this.”

Using the VISIR mid-infrared camera on the European Southern Observatory’s Very Large Telescope, Pope, Callingham, and their colleagues measured the velocity of the dust within the spiral arms. At this end-stage of their brief life cycle (these systems only last a few hundred thousand years—a blink of the eye in cosmological terms), stars within Wolf-Rayet systems spin rapidly, producing stellar winds that move at horrendous speeds. These winds carry significant portions of stellar material into space, and they’re responsible for forming the majestic plumes of dust particles. In the case of Apep, its spiral arms measure several light-years across.

By measuring the rotational speeds within this nebula, the researchers concluded that at least one of the three stars within the system is spinning fast enough such that it’ll trigger a long-duration gamma-ray burst when it finally explodes as supernova (the exact timing is still impossible to predict). The speed of gas within the nebula was clocked at 12 million kilometers per hour, but the dust is moving at “just” 570 million kilometers per hour. The researchers say this discrepancy is indicative of a star approaching near-critical rotation.

“Apep’s dust pinwheel moves much slower than the wind in the system,” said Callingham. “One way this can occur is if one of the massive stars is rotating so quickly that it is nearly tearing itself apart. Such a rotation means that when it runs out of fuel and begins to explode as a supernova, it will collapse at the poles before the equator, producing a gamma-ray burst.”

The significance of this finding, said Pope, is that nobody had observed rapidly rotating Wolf-Rayet systems in our galaxy before. Moreover, many astronomers assumed these objects couldn’t even exist in a galaxy like ours; the Milky Way is old and metal-rich, containing an abundance of heavy stars that should spin down quickly. The new result suggests our understanding of how massive stars die is still incomplete.

“Wolf-Rayet star systems are thought to be the progenitors of long gamma-ray bursts, so if there’s one in our galaxy that’s an exciting find,” Pope told Gizmodo. “Even if not—something deeply weird is happening to this star system and this is the best explanation we have.”

Artist’s impression of a gamma-ray burst.
Image: NASA/Dana Berry/Skyworks Digital

As noted, gamma-ray bursts are among the most powerful explosions known to astronomers. Lasting from between two seconds and a few hours, long-duration gamma-ray bursts release as much energy as the Sun does over the course of its entire lifetime. Disturbingly, some scientists theorize that the Ordovician-Silurian extinction—a mass extinction event that happened on Earth some 440 million years ago—was caused by a gamma-ray burst within our own galaxy. Physicist Adrian Melott from the University of Kansas speculates that a “dangerously near GRB should occur on average two or more times per billion years.”

Pope said it would be “pretty bad” if one were to go off nearby, but he’s not particularly concerned.

“In terms of why we have nothing to worry about, the best I can offer is that it’s highly uncertain whether Apep will go off as a gamma-ray burst at all, and if it does, it is unlikely to be in the very near future.”

As another point of encouragement, gamma-ray bursters are highly directional, spewing their concentrated, high-energy rays in a specific direction. So for Apep to pose a threat, it would not only have to go supernova, it would also have to be pointed in our general direction.

Regardless, there’s nothing we can really do about it except to learn more about Wolf-Rayet systems. It might also be useful to speak the ancient Egyptian incantation to rid the world of Apep’s destructive powers:

Spitting upon Apep, Defiling Apep with the left foot, Taking a lance to smite Apep,Fettering Apep, Taking a knife to smite Apep, Putting fire upon Apep…

[Nature Astronomy]

New Evidence That Supermassive Black Holes Eventually Suck the Life out of Big Galaxies

(THIS ARTICLE IS COURTESY OF GIZOMDO)

 

New Evidence That Supermassive Black Holes Eventually Suck the Life out of Big Galaxies

The Centaurus A galaxy, showing the characteristic jets of gas thrown off by a supermassive black hole. (Image: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray))

At the core of each large galaxy lies a supermassive black hole with the mass of 1 million suns. New research shows that these celestial vacuum cleaners do more than just devour nearby objects—they also grow to a size that eventually suppresses a galaxy’s ability to churn out new stars, effectively rendering them sterile.

Young galaxies are absolutely bursting with bright, newly formed stars. As time passes, however, star formation eventually grinds to a halt. A new study published in Nature shows that supermassive black holes play a critical role in determining when large galaxies stop producing new stars, a process known as “quenching.”

Stars form out of cold gas, so when a galaxy runs out of cold gas it’s effectively quenched. One possible way this could happen—at least for galaxies with supermassive black holes—is that the gas that pours onto a supermassive black hole triggers the production of high-energy jets. The energy released by these jets can expel cold gas out of the galaxy, causing star formation to shut down.

At least that’s the theory. This idea has been around for quite some time, but no observational evidence existed to support the alleged correlation between supermassive black holes and star formation. The new study, led by Ignacio Martín-Navarro from the University of California Santa Cruz, now fills this gap in our knowledge.

Using data collected by the Hobby-Eberly Telescope Massive Galaxy Survey, Martín-Navarro’s team analyzed the spectra of light coming from distant galaxies. This allowed them to separate and measure the varying wavelengths of light coming from these distant objects. The scientists used this data to create a historical snapshot of a galaxy’s star formation history. They then compared this history with black holes of different masses, which resulted in some striking differences—differences that correlated with black hole mass, but not the shape, size, or other properties of black holes.

“The subsequent quenching of star formation takes place earlier and more efficiently in galaxies that host higher-mass central black holes,” wrote the researchers. “The observed relation between black-hole mass and star formation efficiency applies to all generations of stars formed throughout the life of a galaxy, revealing a continuous interplay between black-hole activity and… cooling.”

As Martín-Navarro clarified in an accompanying statement, for galaxies with the same mass of stars, but with a different black hole mass in the center, “those galaxies with bigger black holes were quenched earlier and faster than those with smaller black holes.” This means that star formation will last longer in galaxies with smaller central black holes. “[…Accretion onto more massive black holes leads to more energetic feedback from active galactic nuclei, which would quench star formation faster,” he said.

It’s an exciting result, but there’s still lots of work to do. While the researchers managed to produce observational evidence showing that black hole mass can be connected to the quenching of star formation, they’re still unclear about the exact mechanical processes involved. As study co-author Aaron Romanowsky explained, “There are different ways a black hole can put energy out into the galaxy, and theorists have all kinds of ideas about how quenching happens, but there’s more work to be done to fit these new observations into the models.”

Our galaxy, the Milky Way, features its own super massive black hole and is not immune to this process. It is currently transitioning from star-forming mode to a passive, sterile existence. Eventually, a few billion years from now, all the stars in the Milky Way will be extinguished, and the super massive black hole at center will evaporate into nothing. It’s a grim prospect, but such is the way of the indifferent cosmos.

NASA Captures Stunning Close-Up Photos of Antarctica’s Massive Iceberg

(THIS ARTICLE IS COURTESY OF THE WEBSITE OF ‘GIZMODO’)

 

NASA Captures Stunning Close-Up Photos of Antarctica’s Massive Iceberg

The edge of A-68, the iceberg the calved from the Larsen C ice shelf in July 2017. (Image: NASA/Nathan Kurtz)

Back in July, satellite images showed an iceberg bigger than the state of Delaware calving and drifting away from Antarctica’s Larsen C ice shelf. Well, it’s summertime now in Antarctica, which means scientists are finally able to view this behemoth from up close—and the pictures are just as spectacular as we imagined.

Known as iceberg A-68, the gigantic slab of ice weighs about a trillion tons and features a surface area of 2,240 square miles (5,800 square kilometers). The berg is slowly drifting away from the Larsen C ice shelf, possibly heading towards the South Georgia and the South Sandwich Islands. As it floats away from the Antarctic Peninsula, A-68 is splintering and forming more icebergs in the process.

This past Sunday, November 12th, members of Operation Icebridge—a NASA-led initiative to produce detailed 3D maps of Antarctic and Arctic polar ice—flew a P-3 aircraft armed with a sophisticated array of measuring instruments to take a closer look.

A remarkable shot of A-69, revealing the extent of its size. (Image: NASA/John Sonntag)

“Perhaps you know the feeling: that moment when you see with your eyes something you have previously only seen in pictures,” wrote science writer Kathryn Hansen, who participated in the trip, in an article penned for NASA’s Earth Observatory. “Before today, I knew the Larsen C ice shelf only from the satellite images we have published since August 2016.”

A wide view showing iceberg A-68B (front), iceberg A-68A (middle) and the Larsen C ice shelf (back). (Image: NASA/Nathan Kurtz)

Hansen said she wasn’t prepared for the enormity of the iceberg, as most bergs she’s seen were relatively small and blocky.

“A-68 is so expansive it appears if it were still part of the ice shelf,” she said. “But if you look far into the distance you can see a thin line of water between the iceberg and where the new front of the shelf begins. A small part of the flight today took us down the front of iceberg A-68, its towering edge reflecting in the dark Weddell Sea.”

Who’s up for a swim!? Larsen C ice shelf (left) and iceberg A-68A (right). (Image: NASA/Nathan Kurtz)

In addition to taking photos, the Operational Icebridge scientists sought to measure the depth of water below iceberg, which they did using radar and a gravimeter.

IceBridge project scientist Nathan Kurtz and Sebastián Marinsek from Instituto Antártica Argentino observe Larsen C from a window on the P-3 aircraft. (Image: NASA/Kathryn Hansen)

Scientists now have the clearest picture yet of A-68, which will help them track and study its progress moving forward.

[NASA Earth Observatory]

ABOUT THE AUTHOR

George Dvorsky

George is a contributing editor at Gizmodo and io9.

This Exoplanet’s Hellish Atmosphere Is a Big Deal in the Search For Alien Life

(THIS ARTICLE IS COURTESY OF GIZMODO)

 

Why This Exoplanet’s Hellish Atmosphere Is a Big Deal in the Search For Alien Life

How observers on Earth can detect molecules on entirely other planets. (Image: ESO education and Public Outreach)

By all accounts, the exoplanet known as WASP-19b is a pretty inhospitable place. As one of the closest known hot-Jupiters to its star—orbiting just two percent of the distance between the Earth and the Sun—it’s home to a scorchingly hot, violent atmosphere. The side of the planet which always faces the star churns with massive convection currents, dredging up heavier molecules from the planet’s lower layers.

Unsuitable for life as it may be, WASP-19b’s proximity to its star happened to make it a perfect candidate for atmospheric observation. A paper published Wednesday in the journal Nature has found the very first evidence of titanium oxide on any known exoplanet, in the upper atmosphere of WASP-19b. And that’s significant for a number of reasons.

“We will be able to constrain models and understand the structure of these atmospheres [and] where they were formed,” Elyar Sedaghati, European Southern Observatory astronomer and co-author of the study, told Gizmodo. “Because if we know what’s in the atmosphere, we can turn the clock back a little bit.”

WASP-19 is a pretty average star about 815 light years away from us, located in the Vela constellation. Its only known planet, WASP-19b, was detected by the Wide Angle Search for Planets in 2009, and it only takes three quarters of a day to orbit its star. That proximity made it a perfect target for a spunky little spectrograph called FORS2 (FOcal Reducer and low dispersion Spectrograph), which was originally installed to the Very Large Telescope in Chile in 1999, almost 20 years ago. But there was work to do before observations could begin.

“[The instrument] had to be upgraded,” said Sedaghati. “All that meant was basically replacing these two prisms that correct for some atmospheric distortions as the star goes near the horizon. These were causing some issues in the exoplanet observations that we were doing with this. So, in November 2014 we made the exchange.” He also hopes with these initial promising results, they go back and do even more improvements on the venerable device.

If you wanted to check on WASP-19b yourself, start here in the Vela constellation (Image: ESO education and Public Outreach)

The researchers began peering at WASP-19b around that time, and they got some intriguing data in something called a light curve, which is the measure of how much the light dims when a planet transits a star. Spectrographs work by observing the light emitted by an object and breaking it into its spectra, much like when you shine white light through a prism and it turns into a rainbow. Using this data, you can determine what kind of chemicals are present in whatever the light is shining through. Because this particular planet is so close to its star, the researchers could see the spectra of its ferociously roiling atmosphere, which extends way further into space than, say, the atmosphere of a more distant gas giant like Jupiter does.

Getting better at decoding the atmospheres of exoplanets, even inhospitable ones like WASP-19b, will contribute to the holy grail of exoplanet research: hunting for signs of life. “Methane — that could be in combination with other molecules, a sign of life — will have very similar absorption features with titanium oxide. This basically gives us hope for future observations for example with the James Webb Telescope,” said Sedaghati.

There are still a lot of steps before that moment, as the JWST won’t launch until the latter half of 2018, and then will need to time scan the skies. But these WASP-19b results are nonetheless encouraging.

“It’s a very nice result,” said Sara Seager, a professor of planetary sciences and physics at MIT, in an email. “I can say this is an outstanding achievement from a ground-based telescope and nature delivered us a fantastic hot planet atmosphere. So far, too many planets are literally “clouded out” and we can’t observe any spectral features. [Titanium Oxide] seems obscure, but is actually a very strong absorber—kind of like a skunk smell, only a tiny amount can make a difference.”

Seager says planets like WASP-19b have a “treasure trove” of features which are really useful to observe.

“It’s an amazing relief to see that planet atmospheres are behaving as expected. Hot planet atmospheres can be nearly as hot as cool star atmospheres and the cool stars are dominated by TiO,” she said.

Jonathan Fortney, an expert in exoplanet atmospheres at UC Santa Cruz, actually predicted that metal oxides would be present in nearby hot-Jupiters. But he admits discoveries in the field will be slow for now because most “general use” instruments can’t pick up the level of detail required for terrestrial exoplanetary atmospheric analysis. Even though the FORS2 tool has been really successful in this project, it was installed before we had even discovered exoplanets using the transit method.

“To me this shows that understanding exoplanet atmospheres is an extremely challenging observational field,” he said. “We must be thoughtful in how we design instruments to detect and understand exoplanet atmospheres. And we must be patient. I really think that this long time lag will be repeated, likely on an even longer time scale, for the atmospheres of temperate terrestrial planets.”

As the study of exoplanet atmospheres continues, be prepared to see stories of successful characterization where the evidence is a little sketchy, Fortney warns.

“People will make claims about these atmospheres, some will end up being correct, some will end up not being correct, and it will take a lot of time for the field to settle out, to correct itself. It will be exciting, but not clear-cut in the first findings,” said Fortney.

Bryson is a freelance storyteller who wants to explore the universe with you.

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