In a New Study, Researchers Show a Quarter of Stars Like Our Sun Eat Their Planets

How unusual is our Solar System? In about 30 years since planets were first discovered orbiting stars besides our Sun, we have found that planetary systems are prevalent in the Galaxy. However, most of them are pretty different from the Solar System we know.

The worlds in our Solar System revolve around the Sun in stable and virtually circular paths, suggesting that the orbits have not altered much since the planets first appeared. However, many planetary systems orbiting around other stars have experienced a chaotic past.

Our international team of astronomers has addressed this issue in a study released in Nature Astronomy. We discovered that between 20% and 35% of Sun-like stars consume their planets, with one of the most likely figures being 27%.

This implies that a minimum of a quarter of planetary systems orbiting stars similar to the Sun has had a disorderly and dynamic past.

Chaotic histories and binary stars

Astronomers have seen many exoplanetary systems in which big or medium-sized worlds have moved significantly. The gravity of these migrating worlds may likewise have disturbed the other planets’ courses or even pushed them into unstable orbits.

In most of these highly dynamic systems, some planets have likely fallen into the host star. However, we did not understand precisely how common these chaotic systems are relative to quieter systems like ours, whose orderly architecture has promoted the development of life on Earth.

Even with one of the most precise astronomical instruments readily available, it would be tough to work this out by directly examining exoplanetary systems. Alternatively, we analyzed the chemical composition of stars in binary stars.

Binary stars are comprised of 2 stars in orbit around each other. Both stars are usually created simultaneously from the same gas, so we expect them to have the same mix of components.

Nevertheless, if a planet falls into one of the stars, it is liquified in the star’s external layer. This can change the star’s chemical composition, suggesting that we see even more of the elements that develop rocky worlds – such as iron than we otherwise would.

Traces of rocky planets

We verified the chemical composition of 107 binary systems made up of Sun-like stars by examining the spectrum of light they produce. From this, we determined the number of stars that contained more planetary material than their companion star.

We also found three things that add to the unambiguous proof that the chemical differences observed amongst binary pairs were caused by consuming planets.

First, we discovered that stars with a thinner outer layer are more likely to be richer in iron in comparison to their companion. This is consistent with planet-eating, as when planetary material is diluted in a thin outer layer, it makes a more considerable change to the layer’s chemical composition.

Second, stars richer in iron and various other rocky-planet elements likewise contain more lithium in comparison to their companions. Lithium is quickly degraded in stars, while it is preserved in the planets. So a suspiciously high level of lithium in a star was absorbed after the star was created, which fits with the concept that a planet carried the lithium until the star ate it.

Third, the stars containing more iron in comparison to their companions likewise have more than comparable stars in the Galaxy. Nonetheless, the very same stars have standard amounts of carbon, which is a volatile element because of this, it is not carried by rocks. Therefore these stars have been chemically supplemented by rocks from planets or planetary material.

The hunt for Earth 2.0

These results stand for discovery for stellar astrophysics and also exoplanet exploration. Not only have we discovered that consuming planets can transform the chemical composition of Sun-like stars, but likewise that a considerable fraction of their planetary systems underwent a chaotic past, unlike our solar system.

Finally, our research study opens up the opportunity of using chemical analysis to determine stars that are the most likely to host true analogs of our tranquil planetary system.

There are millions of reasonably close-by stars comparable to the Sun. Without a method to determine the most promising targets, the quest for Planet 2.0 will look like searching for a needle in a haystack.

Originally published on Life Science. Read the original article.

Originally written by Lorenzo Spina, Postdoctoral Research Fellow, Italian National Institute for Astrophysics, and formerly Research Fellow, Monash University.

Reference: “Chemical evidence for planetary ingestion in a quarter of Sun-like stars” by Lorenzo Spina, Parth Sharma, Jorge Meléndez, Megan Bedell, Andrew R. Casey, Marília Carlos, Elena Franciosini and Antonella Vallenari, 30 August 2021, Nature Astronomy.
DOI: 10.1038/s41550-021-01451-8