Astronomers Find a 3 Million Year Old Planet

Astronomers have just found one of the youngest planets ever. At only 3 million years old, planet TIDYE-1b (also known as IRAS 04125+2902 b) is practically in its infancy. By comparison, Earth is 4.5 billion years old: that’s 1500 times older. The discovery of a planet this young can teach scientists a lot about the early stages of planet formation, and the peculiarities of this particular one have scientists re-evaluating their models of planetary birth.

“Astronomy helps us explore our place in the Universe — where we came from and where we might be going. Discovering planets like this one allows us to look back in time, catching a glimpse of planetary formation as it happens,” said Madyson Barber, lead author of a new paper and graduate student at UNC-Chapel Hill.

Barber discovered TIDYE-1b using the transit method, where a planet passes in front of its star, dimming the light and revealing itself to the observer – in this case, NASA’s TESS telescope. Previously, more than a dozen young planets in the 10-40 million-year-old range have been found via transit, but TIDYE-1b surpasses them all.

It’s a rare find because, under normal circumstances, such young planets are usually obscured by gas and dust that make up the ‘protoplanetary disc’, a debris field orbiting a star like a ring, out of which new planets are built.

“Planets typically form from a flat disk of dust and gas, which is why planets in our Solar System are aligned in a ‘pancake-flat’ arrangement,” explains Andrew Mann, associate professor at UNC-Chapel Hill. “But here, the disk is tilted, misaligned with both the planet and its star — a surprising twist that challenges our current understanding of how planets form.” 

Since TIDYE-1b orbits its star at a different angle than the main protoplanetary disc, it was visible despite its youth. It can often take more than five million years for such a disc to clear out in a young star system, so this was a lucky break without which the astronomers would not have been able to see the planet.

The planet is very close to its star, orbiting around it about once every nine days. The researchers believe it is a young example of what will someday become a ‘super-Earth or a ‘sub-Neptune, a planet type missing in our solar system but which seems common in the wider Milky Way galaxy. TIDYE-1b is not as dense as the Earth is, but it is about 11 times larger in diameter.

The discovery provides conclusive evidence that planets can form earlier than previously known – the lack of examples of planets younger than 10 million years found so far is not because they don’t exist. It’s just because they tend to be hidden from view.