In the study of planets, there's always something bigger.
A newly discovered planet called "b Cen (AB)b" is unnervingly large, with a mass greater than 10 Jupiters combined, which means it's one of the most massive planets ever witnessed by humans. But according to the current consensus on how much mass can exist in a solar system, the colossal gas giant shouldn't exist at all, according to a recent study published in the journal Nature.
It's so bizarre that this discovery is leading scientists to rethink what we know about how planets form.
A gigantic planet implies an 'astounding diversity' of exoplanets
The massive alien world orbits the two stars that make up the b Centauri binary system, which is 325 light-years from Earth. Combined, the solar system has a mass of nearly 10 suns. And the planet is 52 billion miles from its host stars, placing it in one of the most distant orbits ever witnessed. Pluto, for comparison, orbits our sun at roughly 3.3 billion miles. It took New Horizons, one of the fastest spacecraft ever built by NASA, nearly ten years to reach Pluto. All to say that the newly discovered giant planet is unconscionably far from its host stars.
Every other planet discovered by scientists was found orbiting star systems that weighed less than three solar masses. Astronomers didn't think planets could come into being in solar systems with excess mass, which means we have to have a serious rethink on what circumstances allow or preclude the formation of alien worlds beyond our solar system. But, the most exciting thing about this new finding is the "astounding diversity" of exoplanetary systems implied by the existence of such a planet, according to Astronomer Markus Janson of Stockholm University, who is the first author of the study.
If planets can form around more massive stars, maybe life can, too
"It seems that no matter where we look — around small or big stars, single stars or binary stars, alive stars or dead stellar remnants — we always find planets in some form, even in places we didn't think possible," said Janson in a report from Gizmodo. It's difficult to overstate how baffling this discovery is to the scientific community. Young stars form with protoplanetary disks surrounding them, which serve as the material that collects into planets. But hot star systems like b Centauri, generally don't give birth to planets, since there's such an unimaginable abundance of X-ray and ultraviolet radiation. Yes, it's very deadly, and "tends to destroy the disks in a very short time."
This is why it was believed "that this wouldn't give planets enough time to form in the disk before it disappeared," explained Janson in the report. But there it is, a fully formed planet just existing in the b Centauri system. It was found using the SPHERE exoplanet imager stationed at the Very Large Telescope in Chile, under the purview of the European Southern Observatory, on March 20 in 2018, and then later, on April 10, 2021. High-imaging contrast enabled the astronomers to distinguish the planet's faint signature from the unreasonably bright light emanating from its two host stars. Sadly, this new planet is "possibly one of the worst places in the galaxy to host life," said Janson in the Gizmodo report. The combined X-ray and ultraviolet radiation "would sterilize any surface that is exposed to it". But there could be life in vast subterranean oceans on the gigantic alien world. And it also expands the spectrum of possible circumstances in which planets can form, which might also signal a broader range of habitable worlds beyond our solar system, waiting for us to discover.