One in ten stars ate a Jupiter-sized planet, suggests paper

In space, cataclysmic occasions occur to stars on a regular basis. Some explode as supernovae, some get torn aside by black holes, and a few undergo different fates. However relating to planets, stars flip the tables. Then it is the celebs who get to inflict destruction.

Increasing red giant stars eat and destroy planets that get too shut, and a brand new examine takes a deeper take a look at the method of stellar engulfment.

Stars like our sun will ultimately change into pink giants. By nuclear fusion, they convert mass into vitality (E=mc², proper?) Over their lifetimes, they shed a lot mass as vitality that they ultimately develop and switch pink. For planets which are too shut to those swollen spheres, it spells the top. They’re ultimately engulfed and utterly destroyed.

Quite a lot of analysis has delved into the planetary engulfment course of, and a brand new examine calculated one in ten advanced stars within the Milky Way will swallow Jupiter-mass planets.

The examine is titled “Large planet engulfment by advanced giant stars: gentle curves, asteroseismology, and survivability.” The primary creator is Christopher O’Connor. O’Connor is a Ph.D. pupil on the Division of Astronomy at Cornell College. The examine has not been peer-reviewed but and is out there on the arXiv server.

The examine focuses on two varieties of advanced stars which are intently associated: pink large department (RGB) stars and asymptotic large department (AGB) stars. The 2 are comparable, and actually, RGB stars can change into AGB stars. The time period advanced star is descriptive sufficient to cowl each, and on this work, the vital factor is that RGB stars and AGB stars have each left the primary sequence.

As these advanced stars lose mass, they develop, and at this stage, any planets in close proximity are in peril. The star’s convective envelope swells and ensnares the planet. This creates drag, which causes the planet to spiral inward towards the star. Astronomers know this, and on this work, the authors examined the frequency of those occasions and the way the celebs reply.

They describe a sun-like star as a star with 1 to 2 solar plenty. About 10% of those stars will engulf a planet between 1 to 10 Jupiter plenty. For these mass relationships, the in-spiral will take between 10 and 100 years or between 100 and 1000 orbits.

To find out these ranges and the way the star responds, the researchers used an open-source astronomy software program software known as MESA (Modules for Experiments in Stellar Astrophysics.) “We use the Modules for Experiments in Stellar Astrophysics (MESA) software program instrument to trace the stellar response to the vitality deposition whereas concurrently evolving the planetary orbit,” they clarify. MESA revealed how the totally different advanced stars responded to engulfing planets with totally different plenty.

Whereas many astrophysical occasions play out over 1000’s, hundreds of thousands, and even tons of of hundreds of thousands of years, planetary engulfment is a a lot faster course of. However earlier than the planet and star come into contact, two issues draw them collectively: stellar growth and orbital decay. That is the primary phase of the engulfment, the place tidal friction causes the planet’s orbital decay. The authors clarify that the tidal friction is “most definitely as a result of turbulent dissipation within the star’s convective envelope.” At this level within the course of, drag from the stellar corona and the stellar wind are minimal.

As soon as the star and planet begin to come into contact with each other, issues change. Tidal friction takes a again seat to pull forces. The authors name this the “grazing” phase. “The ‘grazing’ hydrodynamical interplay of the star and planet is complicated and three-dimensional,” they write. The complexities within the grazing phase can embrace phenomena just like the expulsion of matter from the star and optical and X-ray transients triggered by shocks. However this examine leaves these phenomena apart for now. “We concentrate on the later ‘inspiral’ phase of engulfment, when the planet is totally immersed within the envelope,” they write.

When a planet is within the inspiral phase, it deposits warmth into the star. The latter a part of this phase is known as the late inspiral phase, and the warmth added to the star throughout this phase is essentially answerable for the star’s response. The mass of the planet is a figuring out think about how a lot warmth is deposited.

The engulfments trigger the stellar envelope to develop and contract, although not monotonically. A given mass shell can develop and contract a number of instances throughout the occasion. The researchers say the planet may be visualized as an area warmth supply within the shell, and the supply is shifting towards the star’s heart. This motion, and different properties of the star, create diversified expansions and contractions.

This analysis agrees with earlier analysis displaying that planet engulfment results in optical and infrared bursts in luminosity. The facility and length of those bursts are largely decided by the mass of the planet and the star, although different elements like rotation can come into play. The researchers discovered that for all RGB stars, and for AGB stars engulfing planets as much as 5 Jupiter plenty, the star brightens significantly in just a few years.

The researchers’ total outcomes present that for each varieties of advanced stars engulfing a planet on the low aspect of the vary, as much as three Jupiter plenty, the modifications to the stellar construction are delicate to reasonable. The star’s brightness rises by as much as one magnitude in just a few years. Brighter stars can expertise a double peak.

For stars within the later phases of the AGB, the engulfed planet can create a serious disturbance within the star’s outer layers. It may well set off supersonic growth of the star’s outer layers. On this case, the celebs can resemble Luminous Purple Novae (LRN) as they produce vivid, pink, dusty eruptions.

No matter the kind of star, the mass of the planet, and the way the star responds to the engulfment, the planet’s destiny is at all times the identical: tidal disruption.

This examine has restricted applicability to our solar system. Our sun will change into a pink large in just a few billion years, however until one thing extraordinarily disruptive occurs earlier than then, Jupiter is out of attain. As a substitute, the interior rocky planets face engulfment.

This examine relies on simulations slightly than observations, however the simulations might assist astronomers establish the true factor when it occurs. Engulfments are transient occasions, and a few current and future telescopes and observatories focus solely on transients and time-domain astronomy. When the Vera Rubin Observatory comes on-line round August 2024, it will spot a large number of transient occasions, a few of which shall be advanced stars engulfing Jupiter-mass planets.

The outcomes of this examine might assist spot them.