They discover a planet that is “impossibly large” relative to its star

An “impossible” planet.

It is therefore the most massive planet known in an extremely cold dwarf orbit, and the least massive and hottest star in the universe. The new world, which likely has the same composition as Neptune, cannot be explained by current theories of planet formation, and is the first time a planet of such high mass has been discovered orbiting a low-mass star.

“This discovery – says astrophysicist Suvrath Mahadevan, co-author of the article – really shows how little we know about the universe. “We did not expect such a heavy planet to exist around a low-mass star.”

We know that stars form as a result of the gravitational collapse of large clouds of gas and dust. Then, some of that material stays around the star, forming a disk from which planets eventually form.

But, according to Mahadevan, “the protoplanetary disk around the star LHS 3154 is not expected to have enough solid mass to form such a planet. Yet it exists, so we now need to re-examine what we thought we knew about how planets and stars form.”

In search of cool stars

The new world, called LHS 3154b, was discovered thanks to an astronomical spectrometer built in Pennsylvania itself by a team of scientists led by Mahadevan. The tool is called Habitable zone planet discoverer The HPF instrument is specifically designed to detect planets orbiting the coldest stars in our environment, with the potential for liquid water, an essential element for life, on their surfaces.

While these planets are extremely difficult to detect around large, hot stars like our Sun, the low temperature of ultracool stars means that worlds capable of liquid water are much closer to them than Earth is to the Sun. He explains that, combined with the low mass of ultracool stars, it produces a detectable signal that makes it possible to detect the planet’s presence.

“Think of it as if the star were a blazing fire,” says the astrophysicist. The colder the fire gets, the closer you will have to stand to stay warm. The same applies to planets. If the star were cooler, the planet would need to be closer to that star to be hot enough to contain liquid water. If a planet has an orbit close enough to its ultracool star, we can detect it by observing a very slight change in the color or light of the star’s spectra when it is pulled by an orbiting planet.

“What we have discovered – concludes Mahadevan – provides an extreme test case for all existing theories about planet formation. “This is exactly what we built the HPF to do: discover how the most common stars in our Galaxy form planets and find them.”