520 light years away, astronomers saw a massive, nascent world still embedded in its star’s protoplanetary disk.

A young, nascent world lies close to its parent star, transiting it from our perspective into this artist’s concept. Credit: NASA/JPL-Caltech/R. Injured, K. Miller (Caltech/IPAC)

Not far from Earth, a nascent planet has just begun to live. And by peeking beneath the thick cocoon of material that surrounds it, astronomers could have a rare chance to observe a world for which our solar system has no equivalent settling in early his life.

The planet orbits closely around the star IRAS 04125+2902, located about 520 light years away. The star is very young, around 3 million years old, and only makes up about 70% of the Sun’s mass. Its young age means that its protoplanetary disk – the thick covering of dust and debris that makes up the building blocks of planets – has not been completely removed.

In this disk, astronomers witnessed something never seen before: a transiting exoplanet. (Transiting planets are those that appear to pass in front of their parent stars from our perspective.) Astronomers dubbed it TIDYE-1 b, derived from “TESS Investigation – Demographics of Young Exoplanets.” Madyson Barber, a graduate researcher at the University of North Carolina at Chapel Hill, says this strange moniker is “an alternative to IRAS 04125+2902 b (which is a mouthful).”

Barber and his colleagues today published the discovery of the planet in Nature.

Envelope

Not only is TIDYE-1 a small planet, but it could also transform into a type of planet we don’t have in our solar system, called sub-Neptune. Sub-Neptunes (and their related siblings, super-Earths) are objects with masses between that of Earth and Neptune, and astronomers are still trying to piece together what they look like. Depending on their mass, they can resemble a mini-ice giant (sub-Neptune) or an immense terrestrial planet (super-Earth).

Related: Where is the super-Earth of our solar system?

TIDYE-1 b will not reveal its true nature in our lifetime. It is still enveloped in the hydrogen envelope that often surrounds embryonic planets, which gives it a current mass of about 0.3 Jupiter masses – something closer to a mini-Saturn, weight-wise. But because a planet of this mass still enveloped in a hydrogen envelope is doomed to lose these outer layers over time, the planet itself will be much smaller during its adolescence.

“This mass is not consistent with the mature population of hot Jupiter (massive gas giants rotating near their stars), and young planets are thought to shrink with age, so we think the planet will likely end up in this Earth radius of 2 to 4”. range once it finishes evolving,” says Barber.

Rapid development

That the planet could be seen was a pretty impressive discovery. In most scenarios, it would be difficult to peer into a protoplanetary disk, since it is like trying to spot the stars in the sky on a very cloudy day. But the disk around the planet’s parent star is slightly misaligned, which allowed the team to see TIDYE-1 b.

Barber says the planet shows that some exoplanets can form quite quickly, as TIDYE-1 b is in “cohesive form” in just under a third of the time it took our Earth to form. This could partly be due to its proximity to its star: the planet completes an IRAS 04125+2902 orbit in 8.83 days.

It probably didn’t form there, Barber says, but instead migrated, because “it’s difficult to form large planets close to the star because the disk dissipates first from closest to the star.” star, so there is not enough material to form large planets. so quickly.

There is no evidence (yet) for the existence of other planets in the system, but there could be others. Meanwhile, Barber says TIDYE-1 b’s large radius and low mass could make it an ideal candidate for follow-up observations with the James Webb Space Telescope (JWST). JWST can see in the infrared, where young, hot worlds shine brightest, allowing it to examine the exoplanet and discover more about its composition and how it formed.

Barber’s thesis research aims to learn more about young exoplanets that transit their stars. TIDYE-1 b is therefore perfectly suited to its work. According to Barber, the next youngest planet in his data set is about 10 million years old. “I hope our survey will increase this figure to allow statistical comparisons of planets by age,” she says.