Astronomers see a star eating a planet – an astrophysicist on the team explains first-of-its-kind discovery

For the first time, astronomers have captured images that show a star consuming one of its planets. Named ZTF SLRN-2020, the star is located in the constellation Aquila in the Milky Way Galaxy. As the star swallowed its planet, the star became 100 times brighter than its normal size, allowing the team of 26 astronomers I worked with. Find this event as it happens.

I am a theoretical astrophysicist, and I created computer models that our team uses to interpret the data we collect from the telescopes. Although we see the effects of the star directly and not the planet directly, our team believes that the phenomenon we observed is a star swallowing its planet. Seeing such a phenomenon for the first time confirmed the long-held assumption that stars swallow their planets and explained how this fascinating process works.

The Swicky Transient Facility in Southern California was one of the observatories that captured the glow of light caused by the star consuming its planet.
Caltech/Palomar, CC BY-NC

Detecting a flash in a dynamic night sky

The group I work with is looking for explosions of light and gas that occur when two stars merge into a large, single star. To do this, we are using data Swiggy is a static facility, a telescope located on Mount Palomar in Southern California. It takes nighttime images of vast swaths of the sky, and astronomers can compare these images to detect stars that change in brightness over time, or so-called astronomical transients.

Finding stars that change in brightness isn’t the challenge—it’s sorting out the reason behind any particular change in a star. As my colleague Kishale Te Likes to say, „There are many things that go up in the sky.” The trick to identifying star mergers is to combine visible light — such as data collected in a palomar — with infrared data. NASA’s WISE Space TelescopeIt has been studying the whole sky for the past decade.

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In 2020, the star ZTF SLRN-2020 suddenly became 100 times brighter in visible light in just 10 days. Then it slowly began to fade back to its normal brightness. About nine months ago, the same object started emitting a lot of infrared light. When two stars converge, everything is reduced, with one important difference. The event’s brightness and total energy were a thousand times smaller than any merging star pair astronomers have seen to date.

When a star swallows its planets

The idea that stars can engulf some of their planets has been a long-standing hypothesis in astronomy. Astronomers have long known when stars Hydrogen is depleted in their coresThey are bright and start Increase in size.

Many planets are in orbit smaller than the final size of their parent stars. So, when a star runs out of fuel and begins to expand, nearby planets are inevitably consumed.

A graph showing two lines rising to a peak at the same time, one rising in a very short period of time.
The star ZTF SLRN-2020 increased in brightness in both visible and infrared wavelengths of light, peaking on May 24, 2020.
M. MacLeod, CC BY-ND

Description of a star flash

In the ZTF SLRN-2020 burst, our team never saw the planet itself, only brightening since the star absorbed the planet. This is where theoretical models can be combined with observational data to understand what telescopes have captured.

Combining two stars into one larger star a Drama event It throws matter into the interstellar neighborhood. Most of my career has been focused Modeling the way stellar gas moves It is during these moments of intense contact that one collapses into oneself and is expelled.

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My work shows that the total mass of matter ejected in a merger event is proportional Quantity of items in the attachment. When two equally massive stars merge, you see a large perturbation. Combine a star with a very small companion, and this event can eject a small fraction of the star’s total mass.

The energy released during the explosion of ZTF SLRN-2020 was a thousand times less than is typical for a two-star merger. This means that the material associated with the star is about a thousand times less massive than a normal star. This clue pointed our team toward a gas giant planet—like Jupiter in our own solar system, which weighs about a thousand times less than the Sun.

However, compared to Jupiter, this planet must be orbited very close to the starOne revolution around the star takes only a few days. About 1% are stars Share this system of a massive planet orbiting incredibly close to its parent star.

Also, I think this configuration of a large planet close to its star is important in creating the phenomenon our team saw. My past research suggests that small planets — or those in distant orbits that are only consumed once a star has grown massive — might be. Swallowed with no detectable flash.

The planet around ZTF SLRN-2020 skimmed the stellar surface before eventually falling into the star.

Learning from the real thing

With our data and modeling for ZTF SLRN-2020, our team has been able to draw very clearly how stars and planets interact. First, the planet passes over the star’s surface over many years, slowly heating it up and ejecting material from the star’s atmosphere. As this gas expands and cools, some of it forms molecules and dust. This dust cloud gradually reddens the star and emits large amounts of infrared radiation.

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For ZTF SLRN-2020, the planet’s orbit contracted slowly at first, then got faster and faster as the planet broke through the thick layers of the star’s atmosphere. Eventually, over a few final days, the planet fell below the surface of the star and was torn apart by the heat and force of the collision. This rapid infusion of energy fueled ZTF SLRN-2020’s 10-day, hundredfold increase in brightness. Following this climactic moment, the star began to fade, telling our team that the planet-swallowing process was over and that the star was going about business as usual.

Although the devastating event has passed, there is still much to learn. Next week our team will begin analyzing the data The James Webb Space Telescope Now ZTF hopes to learn about the chemistry of the gas surrounding SLRN-2020.

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