For the first time in astronomical history, scientists have taken an actual snapshot of an exoplanet in the midst of formation. Located about 337 light-years from Earth, the protoplanet, which will eventually resemble something like Jupiter, is completely surrounded by a massive ring of gas and dust. The photo was taken by astronomers using the European Southern Observatory's Very Large Telescope in Chile.
The discovery marks the first time that scientists have been able to observe the formation of a planet directly. Prior to this, scientists have used computer simulations to show that these kinds of cosmic processes are possible. Astronomers Sascha Quanz, Julien Girard, and colleagues had their paper published in the Astrophysical Journal Letters.
An artistic impression of HD100546. Illustration: ESO/L. calçada.
The astronomers made the discovery by analyzing the unusually large circumstellar disk that surrounds the HD100546 solar system. Normally, these disks are about 200 AU in diameter, but this one's 700 AU, making it an intriguing candidate for analysis — and one that's considerably easier to study with a telescope.
A few years ago, scientist noticed that the disk displayed strange asymmetrical properties. Hoping to catch a glimpse inside this disk, Quanz and his team used a high-resolution camera at the Very Large Telescope called the Apodising Phase Plate (APP). It's a system they developed themselves, and it works by minimizing the distribution of starlight. This allows them to study the object's immediate surroundings.
And that's how they discovered something at a distance of 70 AU from its parent star.
But they weren't entirely sure what it was at first. Assuming their calculations were correct, it would be an object that's 20 times the mass of Jupiter. This presented a problem. Something that big should create a large gap in the circumstellar disk as it sucks in material over the course of time. But no gap could be found. As a consequence, the researchers were forced to posit two different explanations in their paper.
First, they speculate that it's a very, very young protoplanet — one that's only about 100,000 years old. This bright and hot planet, they argue, may still be actively absorbing and compressing mass, what's called the accretion phase.
Alternatively — and they're less certain about this one — is that a second planet might exist within 10 AU of the star. In this scenario, two planets would have competed with each other, resulting in the smaller one being ejected. The scientists just happened to observe this solar system at the right time to observe the remnants of this, what they admit would be a tremendous coincidence given the 20-year window for this kind of discovery. Moreover, there's absolutely no evidence to support the second planet hypothesis.
But what they do have is stronger case in support of the idea that it's a gas giant in the making. The astronomers will keep their eye on this protoplanet just to make sure.
You can read the entire study, which was published in Astrophysical Journal Letters, here (pdf).
Top image: ESO.