Enormous planet quickly orbiting a tiny, dying star

Thanks to a bevy of telescopes in space and on Earth — and even a pair of amateur astronomers in Arizona — a University of Wisconsin-Madison astronomer and his colleagues have discovered a Jupiter-sized planet orbiting at breakneck speed around a distant white dwarf star. The system, about 80 light years away, violates all common conventions about stars and planets. The white dwarf is the remnant of a sun-like star, greatly shrunken down to roughly the size of Earth, yet it retains half the sun’s mass. The massive planet looms over its tiny star, which it circles every 34 hours thanks to an incredibly close orbit. In contrast, Mercury takes a comparatively lethargic 90 days to orbit the sun. While there have been hints of large planets orbiting close to white dwarfs in the past, the new findings are the clearest evidence yet that these bizarre pairings exist. That confirmation highlights the diverse ways stellar systems can evolve and may give a glimpse at our own solar system’s fate. Such a white dwarf system could even provide a rare habitable arrangement for life to arise in the light of a dying star.

“We’ve never seen evidence before of a planet coming in so close to a white dwarf and surviving. It’s a pleasant surprise,” says lead researcher Andrew Vanderburg, who recently joined the UW-Madison astronomy department as an assistant professor. Vanderburg completed the work while an independent NASA Sagan Fellow at the University of Texas at Austin.

The researchers published their findings Sept. 16 in the journal Nature. Vanderburg led a large, international collaboration of astronomers who analyzed the data. The contributing telescopes included NASA’s exoplanet-hunting telescope TESS and two large ground-based telescopes in the Canary Islands.

Vanderburg was originally drawn to studying white dwarfs — the remains of sun-sized stars after they exhaust their nuclear fuel — and their planets by accident. While in graduate school, he was reviewing data from TESS’s predecessor, the Kepler space telescope, and noticed a white dwarf with a cloud of debris around it.

“What we ended up finding was that this was a minor planet or asteroid that was being ripped apart as we watched, which was really cool,” says Vanderburg. The planet had been destroyed by the star’s gravity after its transition to a white dwarf caused the planet’s orbit to fall in toward the star.

Ever since, Vanderburg has wondered if planets, especially large ones, could survive the journey in toward an aging star.

By scanning data for thousands of white dwarf systems collected by TESS, the researchers spotted a star whose brightness dimmed by half about every one-and-a-half days, a sign that something big was passing in front of the star on a tight, lightning-fast orbit. But it was hard to interpret the data because the glare from a nearby star was interfering with TESS’s measurements. To overcome this obstacle, the astronomers supplemented the TESS data from higher-resolution ground-based telescopes, including three run by amateur astronomers.

“Once the glare was under control, in one night, they got much nicer and much cleaner data than we got with a month of observations from space,” says Vanderburg. Because white dwarfs are so much smaller than normal stars, large planets passing in front of them block a lot of the star’s light, making detection by ground-based telescopes much simpler.

The data revealed that a planet roughly the size of Jupiter, perhaps a little larger, was orbiting very close to its star. Vanderburg’s team believes the gas giant started off much farther from the star and moved into its current orbit after the star evolved into a white dwarf.

The question became: how did this planet avoid being torn apart during the upheaval? Previous models of white dwarf-planet interactions didn’t seem to line up for this particular star system.

The researchers ran new simulations that provided a potential answer to the mystery. When the star ran out of fuel, it expanded into a red giant, engulfing any nearby planets and destabilizing the Jupiter-sized planet that orbited farther away. That caused the planet to take on an exaggerated, oval orbit that passed very close to the now-shrunken white dwarf but also flung the planet very far away at the orbit’s apex.

Over eons, the gravitational interaction between the white dwarf and its planet slowly dispersed energy, ultimately guiding the planet into a tight, circular orbit that takes just one-and-a-half days to complete. That process takes time — billions of years. This particular white dwarf is one of the oldest observed by the TESS telescope at almost 6 billion years old, plenty of time to slow down its massive planet partner.

While white dwarfs no longer conduct nuclear fusion, they still release light and heat as they cool down. It’s possible that a planet close enough to such a dying star would find itself in the habitable zone, the region near a star where liquid water can exist, presumed to be required for life to arise and survive.

Now that research has confirmed these systems exist, they offer a tantalizing opportunity for searching for other forms of life. The unique structure of white dwarf-planet systems provides an ideal opportunity to study the chemical signatures of orbiting planets’ atmospheres, a potential way to search for signs of life from afar.

“I think the most exciting part of this work is what it means for both habitability in general — can there be hospitable regions in these dead solar systems — and also our ability to find evidence of that habitability,” says Vanderburg.

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Coal-burning in Siberia after volcanic eruption led to climate change 250 million years ago

A team of researchers led by Arizona State University (ASU) School of Earth and Space Exploration professor Lindy Elkins-Tanton has provided the first ever direct evidence that extensive coal burning in Siberia is a cause of the Permo-Triassic Extinction, the Earth’s most severe extinction event. The results of their study have been recently published in the journal Geology.

For this study, the international team led by Elkins-Tanton focused on the volcaniclastic rocks (rocks created by explosive volcanic eruptions) of the Siberian Traps, a region of volcanic rock in Russia. The massive eruptive event that formed the traps is one of the largest known volcanic events in the last 500 million years. The eruptions continued for roughly two million years and spanned the Permian-Triassic boundary. Today, the area is covered by about three million square miles of basaltic rock.

This is ideal ground for researchers seeking an understanding of the Permo-Triassic extinction event, which affected all life on Earth approximately 252 million years ago. During this event, up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct.

Calculations of sea water temperature indicate that at the peak of the extinction, the Earth underwent lethally hot global warming, in which equatorial ocean temperatures exceeded 104 degrees Fahrenheit. It took millions of years for ecosystems to be re-established and for species to recover.

Among the possible causes of this extinction event, and one of the most long-hypothesized, is that massive burning coal led to catastrophic global warming, which in turn was devastating to life. To search for evidence to support this hypothesis, Elkins-Tanton and her team began looking at the Siberian Traps region, where it was known that the magmas and lavas from volcanic events burned a combination of vegetation and coal.

While samples of volcaniclastics in the region were initially difficult to find, the team eventually discovered a scientific paper describing outcrops near the Angara River. “We found towering river cliffs of nothing but volcaniclastics, lining the river for hundreds of miles. It was geologically astounding,” says Elkins-Tanton.

Over six years, the team repeatedly returned to Siberia for field work. They flew to remote towns and were dropped by helicopter either to float down rivers collecting rocks, or to hike across the forests. They ultimately collected over 1,000 pounds of samples, which were shared with a team of 30 scientists from eight different countries.

As the samples were analyzed, the team began seeing strange fragments in the volcaniclastics that seemed like burnt wood, and in some cases, burnt coal. Further field work turned up even more sites with charcoal, coal, and even some sticky organic-rich blobs in the rocks.

Elkins-Tanton then collaborated with fellow researcher and co-author Steve Grasby of the Geological Survey of Canada, who had previously found microscopic remains of burnt coal on a Canadian arctic island. Those remains dated to the end-Permian and were thought to have wafted to Canada from Siberia as coal burned in Siberia. Grasby found that the Siberian Traps samples collected by Elkins-Tanton had the same evidence of burnt coal.

“Our study shows that Siberian Traps magmas intruded into and incorporated coal and organic material,” says Elkins-Tanton. “That gives us direct evidence that the magmas also combusted large quantities of coal and organic matter during eruption.”

And the changes at the end-Permian extinction bear remarkable parallels to what is happening on Earth today, including burning hydrocarbons and coal, acid rain from sulfur, and even ozone-destroying halocarbons.

“Seeing these similarities gives us extra impetus to take action now, and also to further understand how the Earth responds to changes like these in the longer term,” says Elkins-Tanton.

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Materials provided by Arizona State University. Note: Content may be edited for style and length.

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Class of stellar explosions found to be galactic producers of lithium

A team of researchers, led by astrophysicist Sumner Starrfield of Arizona State University (ASU), has combined theory with both observations and laboratory studies and determined that a class of stellar explosions, called classical novae, are responsible for most of the lithium in our galaxy and solar system.

The results of their study have been recently published in the Astrophysical Journal of the American Astronomical Society.

“Given the importance of lithium to common uses like heat-resistant glass and ceramics, lithium batteries and lithium-ion batteries, and mood altering chemicals; it is nice to know where this element comes from,” says Starrfield who is a Regents Professor with ASU’s School of Earth and Space Exploration and a Fellow of the American Astronomical Society. “And improving our understanding of the sources of the elements out of which our bodies and the solar system are made is important.”

The team has gone on to determine that a fraction of these classical novae will evolve until they explode as supernovae of type Ia. These exploding stars become brighter than a galaxy and can be discovered at very large distances in the universe.

As such, they are being used to study the evolution of the universe and were the supernovae used in the mid-1990’s to discover Dark Energy, which is causing the expansion of the universe to accelerate. They also produce much of the iron in the galaxy and solar system, an important constituent of our red blood cells, which carry oxygen throughout the body.

Classical Novae

The formation of the universe, commonly referred to as the “Big Bang,” primarily formed the elements hydrogen, helium, and a little lithium. All the other chemical elements, including the majority of lithium, are formed in stars.

Classical novae are a class of stars consisting of a white dwarf (a stellar remnant with the mass of the Sun but the size of Earth) and a larger star in close orbit around the white dwarf.

Gas falls from the larger star onto the white dwarf and when enough gas has accumulated on the white dwarf, an explosion, or nova, occurs. There are about 50 explosions per year in our galaxy and the brightest ones in the night sky are observed by astronomers world-wide.

Simulations, Observations, and Meteorites

Several methods were used by the authors in this study to determine the amount of lithium produced in a nova explosion. They combined computer predictions of how lithium is created by the explosion, how the gas is ejected and what its total chemical composition should be, along with telescope observations of the ejected gas, to actually measure the composition.

Starrfield used his computer codes to simulate the explosions and worked with co-author and American Astronomical Fellow Charles E. Woodward of the University of Minnesota and co-author Mark Wagner of the Large Binocular Telescope Observatory in Tucson and Ohio State to obtain data on nova explosions using ground-based telescopes, orbiting telescopes, and the Boeing 747 NASA observatory called SOFIA.

Co-authors and nuclear astrophysicists Christian Iliadis of the University of North Carolina at Chapel Hill and W. Raphael Hix of the Oak Ridge National Laboratory and University of Tennessee, Knoxville provided insight into the nuclear reactions within stars that were essential to solving the differential equations needed for this study.

“Our ability to model where stars get their energy depends on understanding nuclear fusion where light nuclei are fused to heavier nuclei and release energy,” says Starrfield. “We needed to know under what stellar conditions we can expect the nuclei to interact and what the products of their interaction are.”

Co-author and isotope cosmochemist Maitrayee Bose of ASU’s School of Earth and Space Exploration analyzes meteorites and interplanetary dust particles that contain tiny rocks that formed in different kinds of stars.

“Our past studies have indicated that a small fraction of stardust in meteorites formed in novae,” says Bose. “So the valuable input from that work was that nova outbursts contributed to the molecular cloud that formed our solar system.” Bose further states that their research is predicting very specific compositions of stardust grains that form in nova outbursts and have remained unchanged since they were formed.

“This is ongoing research in both theory and observations,” says Starrfield. “While we continue to work on theories, we’re looking forward to when we can use NASA’s James Webb Space Telescope and the Nancy Grace Roman Telescope to observe novae and learn more about the origins of our universe.”

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IEEE Spectrum

Arizona Man Sues State Agency Over Right to Call Himself an Engineer

An Arizona man is suing the state’s technical registration board to protest being fined for working without an engineering license, which he maintains he doesn’t need because it doesn’t pertain to the type of work he performs.

It’s the latest case pitting engineers against state licensing agencies that by some accounts have become more aggressive in attempting to regulate who can call themselves an engineer, even as the use of that term becomes more widespread. Meanwhile, licensing proponents maintain it’s necessary for the public interest and point out that Arizona statutes have clear definitions of what an engineer is.


Using computational chemistry to produce cheaper infrared plastic lenses

Five years ago, when University of Arizona materials scientist Jeffrey Pyun presented his first generation of orange-tinted plastic lens to optical scientist Robert Norwood, he responded, “This isn’t the ’60s. No one wants orange glasses, man.”

In the years since, a team led by Puyn has refined the material and created the next generation of lenses. The plastic, a sulfur-based polymer forged from waste generated by refining fossil fuels, is incredibly useful for lenses, window and other devices requiring transmission of infrared light, or IR, which makes heat visible.

“IR imaging technology is already used extensively for military applications such as night vision and heat-seeking missiles,” said Pyun, a professor in the Department of Chemistry and Biochemistry who leads the lab that developed the polymer. “But for consumers and the transportation sector, cost limits high-volume production of this technology.”

The new lens material could make IR cameras and sensor devices more accessible to consumers, according to Norwood, a professor in the James C. Wyant College of Optical Sciences. Potential consumer applications include economical autonomous vehicles and in-home thermal imaging for security or fire protection.

The new polymers are stronger and more temperature resistant than the first-generation sulfur plastic developed in 2014 that was transparent to mid-IR wavelengths. The new lenses are transparent to a wider spectral window, extending into the long-wave IR, and are far less expensive than the current industry standard of metal-based lenses made of germanium, an expensive, heavy, rare and toxic material.

Because of germanium’s many drawbacks, Tristan Kleine, a graduate student in Puyn’s lab and first author on the paper, identified a sulfur-based plastic as an attractive alternative. However, the ability to make IR-transparent plastics is a tricky business.

The components that give rise to useful optical properties, such as sulfur-sulfur bonds, also compromise the strength and temperature resistance of the material. Moreover, the inclusion of additional organic molecules to give the material strength resulted in reduced transparency, since nearly all organic molecules absorb IR light, Kleine said.

To overcome the challenge, Kleine — in collaboration with chemistry graduate student Meghan Talbot and chemistry and biochemistry professor Dennis Lichtenberger — used computational simulations to design organic molecules that were not IR-absorbing and predicted transparency of candidate materials.

“It could have taken years to test these materials in the laboratory, but we were able to greatly accelerate new materials design using this method,” Kleine said.

Germanium requires temperatures greater than 1,700 degrees Fahrenheit to melt and shape, but because of its chemical makeup, the sulfur polymer lenses can be shaped at a much lower temperature.

“A major advantage of these new sulfur-based plastics is the ability to readily process these materials at much lower temperatures than germanium into useful optical elements for cameras or sensors, while still maintaining good thermomechanical properties to prevent cracking or scratches,” Pyun said. “This new material has just checked so many boxes we couldn’t before.”

“Its reliability is essentially equivalent to optical polymers that are routinely used for eyeglasses,” Norwood added.

The team is partnering with Tech Launch Arizona to translate the research into a viable technology.

“Humans light up like a Christmas tree in IR,” Pyun said. “So, as we think about the Internet of Things and human-machine interfaces, the use of IR sensors is going to be a really important way to detect human behavior and activity.”

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IEEE Spectrum

Algorithms Aid Search for Source of Spacetime Rumbles

A new, automated telescope search program in Arizona called SAGUARO hopes to catch neutron stars in the act of colliding