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EI2GYB > ASTRO 02.11.23 14:52l 111 Lines 5581 Bytes #999 (0) @ WW
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Subj: Giant planets cast a deadly pall
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Giant planets cast a deadly pall
How they can prevent life in other planetary systems
Date:
October 31, 2023
Source:
University of California - Riverside
Summary:
Giant gas planets can be agents of chaos, ensuring nothing lives on their
Earth-like neighbors around other stars. New studies show, in some planetary
systems, the giants tend to kick smaller planets out of orbit and wreak havoc
on their climates.
Giant gas planets can be agents of chaos, ensuring nothing lives on their
Earth-like neighbors around other stars. New studies show, in some planetary
systems, the giants tend to kick smaller planets out of orbit and wreak havoc
on their climates.
Jupiter, by far the biggest planet in our solar system, plays an important
protective role. Its enormous gravitational field deflects comets and asteroids
that might otherwise hit Earth, helping create a stable environment for life.
However, giant planets elsewhere in the universe do not necessarily protect
life on their smaller, rocky planet neighbors.
A new Astronomical Journal paper details how the pull of massive planets in a
nearby star system are likely to toss their Earth-like neighbors out of the
"habitable zone." This zone is defined as the range of distances from a star
that are warm enough for liquid water to exist on a 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 as if they have four Jupiters acting like wrecking balls, throwing
everything out of whack," said Stephen Kane, UC Riverside astrophysicist and
author of the journal paper.
Taking data about the system's planets into account, Kane ran multiple computer
simulations to understand the effect of these four giants. He wanted
specifically to look at the habitable zone in this star system and see if an
Earth could remain in a stable orbit there.
"The answer is yes, but it's very unlikely. There are only a select few areas
where the giants' gravitational pull would not 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 for life, a second, related paper shows how one big planet in the
middle of the zone would have a similar effect.
Also published in the Astronomical Journal, this second paper examines a star
system only 30 light years away from Earth called GJ 357. For reference, the
galaxy is estimated to be 100,000 light years in diameter, so this system is
"definitely in our neighborhood," Kane said.
Earlier studies found that a planet in this system, named GJ 357 d, resides in
the system's habitable zone and has been measured at about six times the mass
of the Earth. However, in this paper titled "Agent of Chaos," Kane shows the
mass is likely much bigger.
"It's possible GJ 357 d is as much as 10 Earth masses, which means it's
probably not terrestrial, so you couldn't have life on it," Kane said. "Or at
least, it would not be able to host life as we know it."
In the second part of the paper, Kane and his collaborator, UCR planetary
science postdoctoral scholar Tara Fetherolf, demonstrate that if the planet is
much larger than previously believed, it is certain to prevent more Earth-like
planets from residing in the habitable zone alongside it.
Though there are also a select few locations in the habitable zone of this
system where an Earth could potentially reside, their orbits would be highly
elliptical around the star. "In other words, the orbits would produce crazy
climates on those planets," Kane said. "This paper is really a warning, when we
find planets in the habitable zone, not to assume they are automatically
capable of hosting life."
Ultimately, the pair of papers shows how uncommon it is to find the right set
of circumstances to host 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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