Astronomers now have a pretty good idea how the giant planet was created

Mar 15, 2013 10:47 GMT  ·  By

A few days ago, astronomers revealed some amazing discoveries about four exoplanets relatively nearby. Using new techniques, they were able to observe the four planets directly, a rare feat, and even discover details about their chemical makeup, an even rarer one.

Now, a new paper focuses in even greater detail on one of the four exoplanets that make up the HR 8799 system. Using the Keck II telescope in Hawaii, astronomers looked at HR 8799c, the second most farther out planet in the system.

They were trying to determine the makeup of the atmosphere of the giant planet, 10 times bigger than Jupiter, and they found it to be a mixture of water and carbon monoxide.

This is the most detailed data astronomers have ever been able to get for an exoplanet.

A mixture of the right technology and the right conditions made this possible. For one, the star system is relatively close, at just 130 light years away.

It's also fairly big, all of the exoplanets are several times bigger than Jupiter. In fact, astronomers were trying to determine if they even are planets and not brown dwarfs, or failed stars.

They are also very young, maybe just 30 million years old, meaning they haven't cooled off entirely after their creation. This made it possible for astronomers to observe them in greater detail in infrared.

One of the reasons why they focused on this planet is to test theories on planetary formation. There are two big ones, core accretion and gravitational instability.

The first says that planets form gradually, over time, by accumulating material from the surrounding gas and dust.

This model wouldn't allow for planets to form as far out as HR 8799c, which orbits its planet at about the distance Pluto orbits the sun, if only because there would be less material the farther you got from the star.

The second model predicts that planets form a lot faster, almost instantaneously, from the gas and dust clouds surrounding new stars. This model predicts planets farther out, but also a lot more planets than the four discovered around HR 8799.

The chemical makeup of a planet's atmosphere can hold clues to how it formed, which is why the data from HR 8799c is important.

One telltale clue is that astronomers didn't see any methane in the atmosphere of the planet, alongside the water and carbon monoxide. The ratio of water compared to the other chemicals was also a clue.

Astronomers believe that HR 8799c formed first from ice crystals that lumped together.

When this ice rock became large enough, it started to attract gas, which eventually formed its atmosphere. These findings indicate that HR 8799c formed via core accretion.

This new data means that scientists can now tweak the core accretion model to better suit reality, resulting in a more accurate mathematical model.

Photo Gallery (3 Images)

Artist rendition of HR 8799c
The HR 8799 systemThe HR 8799 system compared to the solar system
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