It’s rare to discover a newborn baby exoplanet. It’s even rarer to discover one that lives so close to its sun it can race all the way around it in just five days.
But two newfound exoplanets do just that. Not only are they some of the youngest, strangest planets astronomers have discovered; scientists say their discovery could help demystify the process of planet formation.
New Found Baby Exoplanet
The younger of the two new planets was found orbiting the star V830 Tau about 430 light years away from Earth. V830 Tau is just 2 million years old (a fraction of our own sun’s 4.6 billion years), meaning it had hardly any time at all to acquire a planet.
And yet astronomers at the Canada-France-Hawaii telescope on Hawaii’s Mauna Kea noticed that the star showed a noticeable “wobble” every 4.9 days — a telltale sign that something very large was orbiting around the star and tugging it ever so slightly with its gravity. Further study revealed what scientists call a “hot Jupiter.” These are large, Jupiter-sized planets that are very close to their star and have incredibly high surface temperatures.
The “Super Neptune”
From a different telescope on the same mountain, gazing at a different corner of the universe at the same time, a separate team noticed that the star K2-33 seemed to dim at regular intervals, indicating that a planet was passing in front of it. That’s how they found the “super Neptune” K2-33b, which is six times the size of Earth and between 500 and 1,000 times younger. It’s also very, very hot, being 20 times closer to its sun than Earth is to ours, and it completes an entire orbit in just five days.
“These two papers are probably the first solid evidence that you can find planets close to their stars at such a young age,” Trevor David, an astronomer at the California Institute of Technology and a co-author of the K2-33b study, told the Guardian.
That’s important, because much of what we know about planet formation comes from older planets; of the more than 3,000 exoplanets discovered in the past three decades, the vast majority are hosted by middle-aged stars like our own sun. That makes the effort to understand how these planets came to be, a NASA statement noted, like trying to understand human development by only studying adults.
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Faster migration of large Jupiter-sized baby Exoplanet?
These two new examples are the planetary equivalent of several-week-old infants, and they could explain a phenomenon that has kept scientists confused for years. When new exoplanets were first being discovered, it was thought that large Jupiter-sized planets could only form far away from their star — much as Jupiter itself did. The cloud of gas and dust that swirls around new stars, called the “protoplanetary disk,” is much cooler and more rich with material out there, making it a good place for big new planets to form.
Then astronomers started to find more and more large exoplanets close to their parent stars; they realized that these “hot Jupiters” must develop farther out and then “migrate” in. But that process was thought to take hundreds of millions of years — far longer than these two exoplanets have existed.
Either hot Jupiters must be migrating a lot faster than scientists expected, or they really can form close to stars.
The researchers studying V830 Tau say their discovery supports the first explanation. They believe that their newfound planet began to form at the edge of the protoplanetary disk and drifted inward very early on, most likely because of interactions with the gas in the disk.
David, the Caltech astronomer, said that both possibilities were on the table for K2-33b. The “in situ” formation theory is “not as wild as it once seemed,” he said in a NASA statement, but a rapid migration could also explain its unusually early appearance so close to its star.
Whatever the cause, we should be grateful that the same phenomenon never happened in our solar system, said astronomer Andrew Mann. He is an astronomer at the University of Texas at Austin who is also studying K2-33b.
“If Jupiter or Neptune had migrated inward after the terrestrial planets formed,” Mann said in a release from the National Optical Astronomy Observatory. “It seems unlikely that our solar system would have an Earth, or any of the terrestrial planets at all.”
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