Astronomers are pioneering a new way to find alien planets orbiting far-away stars. It led them to 6 unusual, vaporizing worlds.
The band of the Milky Way stretches across the sky above the 2.2-meter telescope at the La Silla Observatory in Chile. This is where astronomers watched three stars to find vaporizing planets in their orbits.
- Astronomers used a new technique to identify three stars with a total of six planets in their orbits that are slowly vaporizing.
- Three of these exoplanets are super-Earths that might have once been Neptune-sized but shed material due to the heat of their stars.
- By looking for stars shrouded in the gas that these planets give off, astronomers can use telescopes more efficiently.
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Six unusual, vaporizing planets have shown scientists a new way to find alien worlds around other stars.
The new method of planet hunting involves seeking out stars surrounded by gas clouds. Such stars likely have planets in their orbits that circle too close and slowly vaporize from the heat - a process called ablation.
A group of astronomers at The Open University in England has pinpointed three such stars surrounded by gas clouds, and discovered exoplanets (the term for planets outside our solar system) circling all three. A trio of papers published Monday in the journal Nature Astronomy details the findings.
"This looks to be the most successful method yet for predicting the presence of planets," Jessie Christiansen, a NASA exoplanet scientist who did not work on this research, told Business Insider.
What's more, the clouds of gas these vaporizing worlds leave behind can give scientists some unprecedented data about the planets' makeup and structure.
"These are planets where we can get really high-quality, detailed follow-up information," Carole Haswell, an astrophysicist who led the new research, told Business Insider. "They should be particularly informative planets in forming a bigger picture of 'What are planets generally like in the galaxy?'"
The 'Neptunian desert'NASA/JPL
Neptune's Great Dark Spot and its companion bright smudge, as seen by Voyager 2 from 4.4 million miles away.
Across the cosmos, there seems to be a region close to stars in which rocky planets form, but scientists do not find any Neptune-sized planets - worlds roughly four times the size of Earth and 17 times its mass. This is called the "Neptunian desert." (Scientists found the first Neptune-sized planet ever seen in this region in May.)
These newly discovered vaporizing planets could offer clues about why that is.
All six of the exoplanets orbit their stars closer than Mercury orbits the sun. Scientists think the closest part of this region is so hot that it's difficult for any planet to retain a gaseous atmosphere like Neptune's.
"One of the ways that desert might be formed is, when you have a really hot, giant planet, it could lose its outer layers because the atmosphere is being heated and it's sort of boiling off," Haswell said.
An artist's concept of our solar system gives a sense of the planets' size scale and distance from the sun.
She added that the six planets her team recently found are "all sort of around the edge of that desert," but researchers could one day use this new search method to find a vaporizing planet in the missing size range.
Three super-Earths and a planet that shouldn't exist
Three of the six new planets are rocky super-Earths (planets larger than Earth but not large enough to be Neptune-like), which could be the remaining cores of once-giant planets that crossed the Neptunian desert.
Haswell's team also found a Neptune-sized planet orbiting further out, possibly too far to vaporize, and a planet with half the mass of Jupiter.
When they peered at the third star, they spotted a planet with 2.6 times the mass of Earth.
"And then we discovered that it's actually got a tiny star orbiting around it," Haswell said. "It was a surprise. We didn't expect to find a binary star system."
That's what astronomers call a system with two stars bound together by gravity. Astronomers estimate that up to 85% of all stars have at least one other star in their orbit.
In this particular system, the smaller of the two stars is on the brink of being too small to be considered a star at all and has an oval-shaped orbit that brings it very close to the larger star. It gets so close, in fact, that there would not have been enough room for rocks and gases to coalesce into a planet in between the two stars. Yet somehow, the super-Earth passes between them.
"Our ideas about planetary formation suggest that that planet could not have formed in the binary system as we see it today," Haswell said.
Haswell thinks the small star's orbit might have changed since the super-Earth formed.
The new planet-hunting method could help astronomers make the most of limited telescope time
An artist's impression of the European Extremely Large Telescope (E-ELT) at night whilst observations are in progress.
It's not easy to get time with high-quality telescopes that peer into deep space - astronomers must submit applications for short windows and use the time as efficiently as possible. Searching for ablation, however, could help them ensure they're looking for the right planets around the right stars.
"I knew what kind of planets to look for and designed the observations to be sensitive to them, so we've made particularly efficient use of telescope time," Haswell said. "We're finding planets sort of faster and easier than it's typically done."
What's more, astronomers can collect rich data about the composition of vaporizing planets. By analyzing how light passes through the gas clouds they leave behind, researchers can determine which kinds of molecules are in that gas.
"Because we're looking through that shroud of gas, we can actually work out what chemicals there are making up the surface layers of the planet that's losing mass," Haswell said.
With more traditional methods of analysis, they can also calculate the mass and size of the exoplanets. Piecing together all these factors can help scientists determine the planet's underlying structure: whether it has a solid core surrounded by molten liquid and layers of rock like Earth, or miles of thick, swirling gas with a liquid hydrogen ocean near the center, like Jupiter.
"That then allows you to get more detail filled in in our ideas about how planets form and evolve, which then allows us to put our solar system in context better than we've been able to so far," Haswell said.
Her team will spend 10 more nights observing the exoplanets she found with a powerful telescope early next year. She hopes to find even more planets orbiting the stars. After that, she plans to observe dozens more stars that are likely to have vaporizing planets in close orbits.
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