Thanks to raised telescopes, like the James Webb Space Telescope, we now know our photo voltaic system isn’t distinctive — there are thousands and thousands of different planets in our galaxy.
But we’re nonetheless teasing out clues about what they’re truly like.
One thriller is a sort of planet referred to as a “mini-Neptune.” These are smaller than Neptune and appear to be very common. They’re made of rock and metallic, with thick atmospheres full of hydrogen, helium and perhaps water and different molecules. Strangely, we don’t have any planets like this in our photo voltaic system, so scientists are nonetheless attempting to determine them out.
But a new study, revealed in the Astrophysical Journal Letters and co-led by Matthew Nixon at Arizona State University, provides a brand new wrinkle to our greatest picture but of these distant worlds.
Scientists used to assume these planets had been lined in oceans of molten rock, however Nixon and his staff discovered that many would possibly even have stable surfaces.
Even so, these planets wouldn’t be pleasant locations to go to. Their stable surfaces solely exist as a result of the thick ambiance exerts such a powerful drive. All that air above creates tremendous excessive temperatures and pressures.
“The pressure can be so high that the rock turns solid again,” mentioned Nixon, 51 Pegasi b Fellow in the School of Earth and Space Exploration. “It’s a bit like how carbon turns into diamond deep beneath the Earth’s surface.”
Mass and magma
Planets outdoors our photo voltaic system, referred to as exoplanets, are so far-off that our telescopes can’t see them straight. Instead, scientists search for tiny dips in a star’s gentle when a planet passes in entrance of it.
But scientists have discovered intelligent methods to collect info. For instance, they’ll guess what’s in a planet’s air by the gentle that passes via it. They can even work out how heavy a planet is by watching the way it pulls on its star.
Finding so many mini-Neptunes stunned scientists who noticed them round close by stars, given their complete absence from our personal neighborhood.
Because these planets are so sizzling and have thick atmospheres, scientists thought that they had seas of molten rock on their surfaces, like early Earth. Some even believed these magma oceans may “eat” components of the ambiance, stopping the planet from rising greater.
But digging deeper into the knowledge, a staff of researchers, together with Nixon (who was then an undergraduate scholar at the University of Maryland), Bodie Breza and University of Chicago Professor Eliza Kempton, realized the story may be extra sophisticated.
The group first realized the potential twist whereas analyzing a planet referred to as GJ 1214 b, which orbits a distant star in the constellation Ophiuchus. Recent knowledge from the James Webb Space Telescope suggests this planet’s ambiance could include bigger molecules than easy hydrogen and helium, which means the ambiance could be heavier than beforehand thought — a lot, a lot bigger than Earth’s skinny shell.
This stunned the scientists, in order that they made laptop fashions of totally different sorts of planets. They discovered that many mini-Neptunes as soon as considered lava worlds would possibly even have stable surfaces.
“It’s an either-or,” Kempton mentioned. “You can have this ‘the-floor-is-lava’ scenario or a solid surface, and you’re going to have to take into account a number of other factors about a planet’s atmosphere to try to figure out which regime it falls under.”
Revising the story
These mini-Neptune planets are of particular curiosity to scientists as a result of of their sheer numbers and what they indicate about how planets kind.
“Before we found any exoplanets, we had a nice, neat story about how solar systems form based on how our own solar system formed. We thought that would apply to other systems,” Nixon mentioned. “Following that logic, other solar systems should look like ours. But they don’t.”
Scientists, subsequently, wish to perceive how mini-Neptunes kind and what they appear like now to construct a extra full picture of how planets kind in basic. This can information, amongst different issues, the seek for liveable planets.
The School of Earth and Space Exploration is main the cost in understanding these unusual worlds.
“What excites me about working on this research at SESE is the breadth of expertise — not just in astronomy, but also in geology and mineral physics, which are really fundamental for our understanding both of other planets and of our own,” Nixon mentioned.
This study is supported by funding from the Alfred P. Sloan Foundation, NASA and the Heising-Simons Foundation.
This article was written by Louise Lerner of the University of Chicago, with contributions from Kim Baptista of ASU’s School of Earth and Space Exploration.