Giant planets cast a deadly shadow

Gas giant planets can be agents of chaos and ensure that nothing lives on their Earth-like neighbors around other stars. New studies show that in some planetary systems, giants tend to knock smaller planets out of orbit and wreak havoc on their climates.

Jupiter, by far the largest planet in our solar system, plays an important protective role. Its huge gravitational field deflects comets and asteroids that might otherwise hit Earth, helping to create a stable environment for life. However, giant planets elsewhere in the universe do not necessarily protect life on their smaller, rocky neighbors.

New Astronomical Journal the paper details how the pull of massive planets in a nearby star system is likely to eject their Earth-like neighbors from the “habitable zone.” This zone is defined as the range of distances from the star that are warm enough for liquid water to exist on the planet’s surface, making life possible.

Unlike most other known solar systems, the four giant planets in HD 141399 are farther from their star. This makes it a good model for comparison with our solar system, where Jupiter and Saturn are also relatively far from the Sun.

“It’s like they have four Jupiters that act like wrecking balls and blow everything out of nothing,” said Stephen Kane, a UC Riverside astrophysicist and author of the journal article.

Kane took into account data about the system’s planets and ran several computer simulations to understand the effect of the four giants. Specifically, he wanted to look at the habitable zone in this star system and see if Earth could remain in a stable orbit there.

“The answer is yes, but it’s highly unlikely. There are only a select few areas where the gravitational pull of the giants wouldn’t knock a rocky planet out of its orbit and send it flying right out of the zone,” Kane said.

While this paper shows giant planets outside the habitable zone destroying the chances of life, a second related paper shows how a single large planet in the middle of the zone would have a similar effect.

Also published in Astronomical Journal, this second paper examines a star system just 30 light-years from Earth called GJ 357. By comparison, the galaxy is estimated to be 100,000 light-years across, so the system is “definitely in our neighborhood,” Kane said.

Earlier studies found that the planet in the system, named GJ 357 d, resides in the system’s habitable zone and was measured to be about six times the mass of Earth. However, in this documentary titled “Agent of Chaos”, Kane shows that the mass is likely much greater.

“It’s possible that GJ 357 d has up to 10 Earth masses, which means it’s probably not terrestrial, so you can’t have life on it,” Kane said. “Or at least it wouldn’t be able to host life as we know it.

In the second part of the paper, Kane and his collaborator, UCR planetary science postdoctoral fellow Tara Fetherolf, demonstrate that if the planet is much larger than previously believed, it is certain to prevent multiple Earth-like planets from living side by side in the habitable zone. it.

Although there are also a few select locations in this system’s habitable zone where Earth could potentially reside, their orbits would be highly elliptical around the star. “In other words, the orbits would create crazy climates on these planets,” Kane said. “This paper is really a warning when we find planets in the habitable zone not to assume that they are automatically capable of hosting life.”

Ultimately, these two papers show how unusual it is to find the right set of circumstances for life elsewhere in the universe. “Our work gives us more reasons to be very grateful for the particular planetary configuration we have in our solar system,” Kane said.

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