There are too few telescopes on Earth to satisfy the requirements of all the astronomers, which is why telescope observation time is a precious resource. So you can imagine that something exciting was happening when a group of astronomers made a request for the Very Large Telescope (VLT) to be pointed at one spot in the sky for an entire night.
The astronomical phenomenon that these astronomers hoped to see would be the first of its kind to ever be discovered: the birth of a new planet, just 355 light-years away. First observed in 2013, this planet, called HD 100546, is a gas giant with similarities to Jupiter, our solar system's gas giant.
This young planet orbits a young star that is surrounded by an epic disk of gas and dust (called a circumstellar disk). The planet is nestled within this dusty disk. The formation of such a planet starts when a dense region of gas draws itself more tightly together with the power of the gas particles' gravity. Eventually, the mass of swirling gas draws enough material towards itself that the matter coalesces into a gas planet.
Initial observations of this new planet suggest that its radius is seven times larger than Jupiter's. The observations also predict its temperature to be over 600oC (1112oF).
However, there could be another explanation for what scientists are seeing: The planet may instead be an older gas planet that was formed further towards the center of the disc. In this situation, the only reason we're seeing it now is because it's been hurled outwards. "It's a scenario we still can't rule out completely," first author Sascha Quanz of ETH Zurich noted. "But it's much less likely than our explanation, which suggests that what we're seeing is the birth of a planet."
Determining which scenario is the correct one is what made the data gathered by the telescope so valuable. If this planet is an old one that's been flung out of its circumstellar disk, then it would need to be following a precise trajectory to emerge from the disk somewhere that astronomers can see it now. The chance of this happening is smaller than that of the planet just being born in this location.
The data were also valuable for confirming that the signal was actually coming from just outside the circumstellar disk and not from a background source. This was a concern in the past, but the new data have given scientists enough confidence to say that the source of the signal is indeed from the disk and not elsewhere.
The study, published in the Astrophysical Journal, concluded: "The best explanation for the observed phenomena is that a new planet is actually in the process of formation, embedded in the disk surrounding its parent star."
The finding is exciting as astronomers think that there is another planet located closer to this central star. It would be remarkable to confirm the existence of this second planet in the future.
The Birth of a Giant Planet? - Candidate protoplanet spotted inside its stellar womb. ESO.