NASA Webb's Autopsy of Planet Swallowed by Star Yields Surprise

Planetary Engulfment Illustration
Credits/Illustration: NASA, ESA, CSA, Ralf Crawford (STScI)

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Observations from NASA’s James Webb Space Telescope have provided a surprising twist in the narrative surrounding what is believed to be the first star observed in the act of swallowing a planet. The new findings suggest that the star actually did not swell to envelop a planet as previously hypothesized. Instead, Webb’s observations show the planet’s orbit shrank over time, slowly bringing the planet closer to its demise until it was engulfed in full.

“Because this is such a novel event, we didn’t quite know what to expect when we decided to point this telescope in its direction,” said Ryan Lau, lead author of the new paper and astronomer at NSF NOIRLab (National Science Foundation National Optical-Infrared Astronomy Research Laboratory) in Tucson, Arizona. “With its high-resolution look in the infrared, we are learning valuable insights about the final fates of planetary systems, possibly including our own.”

Two instruments aboard Webb conducted the post-mortem of the scene – Webb’s MIRI (Mid-Infrared Instrument) and NIRSpec (Near-Infrared Spectrograph). The researchers were able to come to their conclusion using a two-pronged investigative approach.

Constraining the How

The star at the center of this scene is located in the Milky Way galaxy about 12,000 light-years away from Earth.

The brightening event, formally called ZTF SLRN-2020, was originally spotted as a flash of optical light using the Zwicky Transient Facility at the Palomar Observatory in San Diego, California. Data from NASA’s NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer) showed the star actually brightened in the infrared a year before the optical light flash, hinting at the presence of dust. This initial 2023 investigation led researchers to believe that the star was more Sun-like, and had been in the process of aging into a red giant over hundreds of thousands of years, slowly expanding as it exhausted its hydrogen fuel. using a two-pronged investigative approach.

However, Webb’s MIRI told a different story. With powerful sensitivity and spatial resolution, Webb was able to precisely measure the hidden emission from the star and its immediate surroundings, which lie in a very crowded region of space. The researchers found the star was not as bright as it should have been if it had evolved into a red giant, indicating there was no swelling to engulf the planet as once thought.

Reconstructing the Scene

Researchers suggest that, at one point, the planet was about Jupiter-sized, but orbited quite close to the star, even closer than Mercury’s orbit around our Sun. Over millions of years, the planet orbited closer and closer to the star, leading to the catastrophic consequence.

“The planet eventually started to graze the star's atmosphere. Then it was a runaway process of falling in faster from that moment,” said team member Morgan MacLeod of the Harvard-Smithsonian Center for Astrophysics and the Massachusetts Institute of Technology in Cambridge, Massachusetts. “The planet, as it’s falling in, started to sort of smear around the star.

In its final splashdown, the planet would have blasted gas away from the outer layers of the star. As it expanded and cooled off, the heavy elements in this gas condensed into cold dust over the next year.

Inspecting the Leftovers

While the researchers did expect an expanding cloud of cooler dust around the star, a look with the powerful NIRSpec revealed a hot circumstellar disk of molecular gas closer in. Furthermore, Webb’s high spectral resolution was able to detect certain molecules in this accretion disk, including carbon monoxide.

“With such a transformative telescope like Webb, it was hard for me to have any expectations of what we’d find in the immediate surroundings of the star,” said Colette Salyk of Vassar College in Poughkeepsie, New York, an exoplanet researcher and co-author on the new paper. “I will say, I could not have expected seeing what has the characteristics of a planet-forming region, even though planets are not forming here, in the aftermath of an engulfment.”

The ability to characterize this gas opens more questions for researchers about what actually happened once the planet was fully swallowed by the star.

“This is truly the precipice of studying these events. This is the only one we've observed in action, and this is the best detection of the aftermath after things have settled back down,” Lau said. “We hope this is just the start of our sample.”

These observations, taken under Guaranteed Time Observation program 1240, which was specifically designed to investigate a family of mysterious, sudden, infrared brightening events, were among the first Target of Opportunity programs performed by Webb. These types of study are reserved for events, like supernova explosions, that are expected to occur, but researchers don’t exactly know when or where. NASA’s space telescopes are part of a growing, international network that stands ready to witness these fleeting changes, to help us understand how the universe works.

Researchers expect to add to their sample and identify future events like this using the upcoming Vera C. Rubin Observatory and NASA’s Nancy Grace Roman Space Telescope, which will survey large areas of the sky repeatedly to look for changes over time.

The team’s findings appear today in The Astrophysical Journal.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

Source: NASA's James Webb Space Telescope/News

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Astronomers Witness Star Devouring Planet: Possible Preview of the Ultimate Fate of Earth

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Artist Impression of a Star Devouring One of Its Planets

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Infographic of Star Engulfing a Planet 

 

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Infografía de una Estrella devorando un Planeta

 

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Videos

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Astronomers Witness Star Devouring Planet: Possible Preview of the Ultimate Fate of Earth

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Por primera vez astrónomos observan un planeta devorado por su estrella

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Gemini South captures first direct evidence of an exoplanet being swallowed by an ancient Sun-like star

Astronomers using the Gemini South telescope in Chile, operated by NSF’s NOIRLab, have observed the first evidence of a dying Sun-like star engulfing an exoplanet. The “smoking gun” of this event was seen in a long and low-energy outburst from the star — the telltale signature of a planet skimming along a star’s surface. This never-before-seen process may herald the ultimate fate of Earth when our own Sun nears the end of its life in about five billion years.

By studying countless stars at various stages of their evolution, astronomers have been able to piece together an understanding of the life cycle of stars and how they interact with their surrounding planetary systems as they age. This research confirms that when a Sun-like star nears the end of its life, it expands anywhere from 100 to 1000 times its original size, eventually engulfing the system’s inner planets. Such events are estimated to occur only a few times each year across the entire Milky Way. Though past observations have confirmed the aftermath of planetary engulfments [1], astronomers have never caught one in the act, until now.

With the power of the Gemini South Adaptive Optics Imager (GSAOI) on Gemini South, one half of the International Gemini Observatory, operated by NSF’s NOIRLab, [2] astronomers have observed the first direct evidence of a dying star expanding to engulf one of its planets. Evidence for this event was found in a telltale “long and low-energy” outburst from a star in the Milky Way about 13,000 light-years from Earth. This event, the devouring of a planet by an engorged star, likely presages the ultimate fate of Mercury, Venus, and Earth when our Sun begins its death throes in about five billion years.

“These observations provide a new perspective on finding and studying the billions of stars in our Milky Way that have already consumed their planets,” says Ryan Lau, NOIRLab astronomer and co-author on this study, which is published in the journal Nature.

For most of its life, a Sun-like star fuses hydrogen into helium in its hot, dense core, which allows the star to push back against the crushing weight of its outer layers. When hydrogen in the core runs out, the star begins fusing helium into carbon, and hydrogen fusion migrates to the star’s outer layers, causing them to expand, and changing the Sun-like star into a red giant.

Such a transformation, however, is bad news for any inner-system planets. When the star's surface eventually expands to engulf one of its planets, their interaction would trigger a spectacular outburst of energy and material. This process would also put the brakes on the planet's orbital velocity, causing it to plunge into the star.

The first hints of this event were uncovered by optical images from the Zwicky Transient Facility. Archival infrared coverage from NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), which is able to peer into dusty environments in search of outbursts and other transient events, then confirmed the engulfment event, named ZTF SLRN-2020. “Our team’s custom reanalysis of all-sky infrared maps from NEOWISE exemplifies the vast discovery potential of archival survey data sets,” said NOIRLab astronomer Aaron Meisner, another co-author on the paper.

Distinguishing a planetary-engulfment outburst from other types of outbursts, such as solar-flare-type events and coronal-mass ejections, is difficult and requires high-resolution observations to pinpoint the location of an outburst and long-term measurements of its brightness without contamination from nearby stars.

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More Information

Gemini South provided these essential data thanks to its adaptive-optics capabilities.

“Gemini South continues to expand our understanding of the Universe and these new observations support predictions for the future of our own planet,” said NSF Gemini Observatory program director Martin Still. “This discovery is a wonderful example of the feats we can accomplish when we combine world-class telescope operations and cutting-edge scientific collaboration.”

“With these revolutionary new optical and infrared surveys, we are now witnessing such events happen in real time in our own Milky Way — a testament to our almost certain future as a planet,” said Kishalay De, an astronomer at the Massachusetts Institute of Technology and lead author on the paper.

The outburst from the engulfment lasted approximately 100 days and the characteristics of its lightcurve, as well as the ejected material, gave astronomers insight into the mass of the star and that of its engulfed planet. The ejected material consisted of about 33 Earth masses of hydrogen and about 0.33 Earth masses of dust. “That's more star- and planet-forming material being recycled, or burped out, into the interstellar medium thanks to the star eating the planet,” said Lau. From this analysis, the team estimated that the progenitor star is about 0.8−1.5 times the mass of our Sun and the engulfed planet was 1−10 times the mass of Jupiter.

Now that the signatures of a planetary engulfment have been identified for the first time, astronomers have improved metrics they can use to search for similar events happening elsewhere in the cosmos. This will be especially important when Vera C. Rubin Observatory comes on line in 2025. For instance, the observed effects of chemical pollution on the remnant star when seen elsewhere can hint that an engulfment has taken place. The interpretation of this event also provides evidence for a missing link in our understanding of the evolution and final fates of planetary systems, including our own.

“I think there's something pretty remarkable about these results that speaks to the transience of our existence,” says Lau. “After the billions of years that span the lifetime of our Solar System, our own end stages will likely conclude in a final flash that lasts only a few months.”

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Links

• Research paper: “An infrared transient from a star engulfing a planet”
• Photos of the Gemini South telescope
• Videos of the Gemini South telescope

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Contacts:

Kishalay De
MIT Kavli Institute Postdoctoral Fellow
Email: kde1@mit.edu
Charles Blue
NSF’s NOIRLab
Tel: +1 202 236 6324
Email: charles.blue@noirlab.edu

Josie Fenske
NSF’s NOIRLab
Email: josie.fenske@noirlab.edu

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)/News

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Star Eats Planet, Brightens Dramatically Planetary Death Spiral

This artist's impression shows a doomed planet skimming the surface of its star. Astronomers used a combination of telescopes to spot the first direct evidence of an aging, bloated sun-like star, like the one pictured here, engulfing its planet. These telescopes included the Zwicky Transient Facility (ZTF) at Caltech's Palomar Observatory, the W.M. Keck Observatory, and NASA's NEOWISE mission. The aging star depicted here, called ZTF SLRN-2020, is roughly 10 billion years old. It had begun to inflate over hundreds of thousands of years as it transformed into a red giant, and, as a result, inched closer to its inner planet. According to astronomers, when the planet was almost touching the surface of the star, the increasing frictional forces caused the planet to rapidly spiral inward. Eventually, on timescales that are not certain, the planet plunged into the core of the star. When that happened, the star inflated to four times its size and brightened by a factor of more than a hundred. ZTF SLRN-2020 lies about 15,000 light-years away in the constellation Aquila. Credit: K. Miller/R. Hurt (Caltech/IPAC)

Planetary Death Spiral

ZTF and NEOWISE spot evidence for the first known case of a star engulfing its planet

For the first time, astronomers have caught a star in the act of swallowing a planet whole. The sun-like star, called ZTF SLRN-2020, lies about 15,000 light-years away in our galaxy and is thought to have engulfed a hot gas giant about the size of Jupiter or smaller. Scientists already knew that older stars will, as they puff up with age, ultimately ingest their inner orbiting planets. Our own sun is predicted to do so in 5 billion years, consuming Mercury, Venus, and likely Earth. But nobody had seen direct evidence for such a remarkable scenario until now.

"The confirmation that sun-like stars engulf inner planets provides us with a missing link in our understanding of the fates of solar systems, including our own," says Kishalay De (MS '18, PhD '21), a postdoctoral scholar at MIT and lead author of a new study about the findings in the journal Nature.

The plump star was first spotted by Zwicky Transient Facility, or ZTF, a National Science Foundation–funded instrument that scans the skies every night from Caltech's Samuel Oschin Telescope at Palomar Observatory near San Diego. ZTF observations showed that the star had dramatically brightened and begun to fade in a period of about a week. At first, De thought this variable star might have resulted from a nova explosion, which occurs when a dead star called a white dwarf steals matter from its companion star. But follow-up observations with the W. M. Keck Observatory atop Maunakea in Hawaiʻi revealed something else was going on.

"I had been looking for erupting stars called novae," De says. "But the Keck data indicated that the star was not lighting up hot gas as is expected for novae. I couldn't make any sense of it."

De, who was then a graduate student at Caltech, put the object aside to finish his PhD thesis and came back to it about a year later after he had moved to MIT. He and his colleagues then obtained infrared data from a camera at Palomar's Hale Telescope called WIRC (Wide-field Infrared Camera), "and that's when things got really interesting," he says.

Those observations showed that the star was brightening over time in not only optical light as ZTF had observed but also in infrared light, which indicates the presence of dust. The researchers then turned to NASA's NEOWISE space telescope in search of more clues. NEOWISE, formerly known as WISE (Wide-field Infrared Survey Explorer), has been scanning the skies regularly since shortly after its launch in 2009. NEOWISE detected the star brightening in infrared light about nine months before ZTF caught the extreme rise in optical light. Even now, after the optical light has faded, NEOWISE continues to pick up infrared light from the star.

"The infrared observations were one of the main clues that we were looking at a star engulfing a planet," says Viraj Karambelkar (MS '21), a grad student at Caltech and co-author of the study.

Once the science team put all the evidence together, they realized that the dust they were seeing with NEOWISE was being generated as a planet spiraled into the star's puffy atmosphere. Like other older stars, the star had begun to expand in size as it aged, bringing it closer to the orbiting planet. As the planet skimmed the surface of the star, it pulled hot gas off the star that then drifted outward and cooled, forming dust. In addition, material from the disintegrating planet blew outward, also forming dust.

What happened next, according to the astronomers, triggered the flare of optical light seen by ZTF.

"The planet plunged into the core of the star and got swallowed whole. As it was doing this, energy was transferred to the star," De explains. "The star blew off its outer layers to get rid of the energy. It expanded and brightened, and the brightening is what ZTF registered."

Some of this expanding stellar material then escaped from the star and traveled outward. Like the boiled-off layers of the star and planet that previously drifted outward, this material also cooled to form dust.

NEOWISE is detecting the infrared glow of all the newly minted dust.

"NEOWISE data are a treasure trove," says co-author Mansi Kasliwal (MS '07, PhD '11), professor of astronomy at Caltech and a co-investigator on the ZTF project. "ZTF caught the event, which is what it excels at, while NEOWISE and other telescopes all helped us figure out what is going on."

The planetary engulfment is similar to what happens when two stars merge, events called red novae. Stars in our universe often form in pairs. Over time, as one star ages and expands faster than its companion, it can essentially ingest its partner. Twenty of these star mergers have been detected to date by ZTF and other instruments, mostly in galaxies beyond the Milky Way.

"Star mergers are thousands of times brighter than this event," says Karambelkar, who has observed eight of these eruptions using ZTF as part of his PhD thesis. "This was another clue that we were looking at a planet being eaten by its star. The level of brightening was much fainter due to the small size of the planet."

"This is just spectacular," Kasliwal adds. "We are still amazed that we caught a star in the act of ingesting its planet, something our own sun will do to its inner planets. That's a long time from now, in five billion years, so we don't have to worry just yet."

The Nature study titled "An infrared transient from a star engulfing a planet," was funded by NASA, the National Science Foundation (NSF), and the Heising-Simons Foundation.

Caltech's ZTF is funded by the NSF and an international collaboration of partners. Additional support comes from the Heising-Simons Foundation and from Caltech. ZTF data are processed and archived by Caltech's IPAC. NASA supports ZTF's search for near-Earth objects through the Near-Earth Object Observations program.

Launched in 2009, the WISE spacecraft was placed into hibernation in 2011 after completing its primary mission. In September 2013, NASA reactivated the spacecraft with the primary goal of scanning for near-Earth objects, or NEOs, and the mission and spacecraft were renamed NEOWISE. The mission was selected competitively under NASA's Explorers Program managed by the agency's Goddard Space Flight Center in Greenbelt, Maryland. NEOWISE is a project of JPL, which is managed by Caltech for NASA, and the University of Arizona and is supported by NASA's Planetary Defense Coordination Office.

Written by
Whitney Clavin

Contact:

Whitney Clavin
(626) 395‑1944
wclavin@caltech.edu

Source: Caltech/News

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Kishaly De - Viraj Karambelkar and Mansi Kasliwal

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