Compared to our planet, exoplanet K2-33b is pretty much still an infant.

This Neptune-sized planet, which is considered the youngest fully formed exoplanet ever detected by NASA's Kepler Space Telescope, is only about 5 to 10 million years old.

Earth, on the other hand, is 4.5 billion years old.

Why is the discovery of this baby exoplanet so important? Astronomers say such young planets could teach us more about planetary formation, which is a very complex and tumultuous process.

The ABC's Of Planetary Formation

So far, NASA scientists have discovered at least 3,000 exoplanets, but nearly all of them are hosted by "middle-age" stars that are about a billion years old or more.

This is going to be a problem for astronomers who attempt to understand the life cycles of planetary systems through existing planets.

Doing so is like trying to comprehend how humans go through their own life cycle — from babies to children to teenagers — but only by studying them as adults. They do not have sufficient data.

Erik Petigura, co-author of the study and a scientist from the California Institute of Technology (Caltech), says this is why baby exoplanet K2-33b could help them better understand how planets form.

This could also allow them to understand the processes that led to the formation of the Earth, he says.

Formation Phase

Planets are usually formed out of protoplanetary disks or thick dicks of dust and gas that surround young stars.

In this case, NASA's extended K2 mission found a periodic dimming of light from a certain star.

Scientists say this is an indication that an orbiting planet could regularly be passing in front of the host star and blocking the light. This confirmed the presence of K2-33b.

The Spitzer Space Telescope then took infrared measurements and discovered that there is indeed a protoplanetary disk surrounding the host star.

This suggests that the young exoplanet's formation phase is nearing its end.

Anne Marie Cody, Petigura's co-author and a postdoc fellow at NASA's Ames Research Center, says the material may initially obscure any forming planets, but after a few million years, the dust begins to dissipate.

"It is during this time window that we can begin to detect the signatures of youthful planets with K2," says Cody.

In Situ Theories

What scientists found very surprising is how close exoplanet K2-33b is to its parent star.

The baby exoplanet is about 10 times nearer to its parent star than the planet Mercury is close to the sun, making it extremely hot.

Some scientists suspect that it takes hundreds of millions of years before a planet from a distant orbit to become close to its host star, so they cannot explain why young K2-33b is close.

There are two theories that attempt to understand this baffling finding, however. The first one suggests that K2-33b may have migrated through a process called disk migration, which takes thousands of years. The second theory says the K2-33b may have formed in situ or right where it is located.

This has led scientists to move on to another data point to ponder.

Trevor David, lead author of the study, says after the initial discoveries of huge exoplanets about two decades ago, scientists thought that these exoplanets could absolutely not have formed there.

However, in recent years, the thinking has shifted. David says momentum has grown for in situ theories. Now, the question they want to answer is this: did exoplanets take a long time to get into their hot orbits or could they have actually been there since their early stages?

David says that at least in the case of K2-33b, it has been there since the beginning phases.

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