The sport of hunting planets or exoplanets around other star systems has a new featherweight champion – a tiny world with about half the mass of Earth, designated GJ 367 b. GJ 367 b, the lightest exoplanet ever found, orbits its parent star in just 7.7 days and appears to be made of unusually dense, almost pure iron.
The existence of the light entity, called “super Mercury” because of its location and composition, challenges some aspects of planet formation theories. It may be implying that miniature worlds are much more diverse than previously believed.
“It’s absolutely wonderful to have found such a planet,” said Diana Valencia, an astrophysicist at the University of Toronto Scarborough who was not involved in the discovery. “It’s mind-blowing.”
GJ 367 b orbits a cool red star about 31 light-years from Earth. Researchers initially detected it using this. NASA’s Transiting Exoplanet Survey Satellite (TESS), a space telescope that finds nearby worlds by measuring how dark the stellar hosts dim as the stars move in front of their faces. Because this eclipse creates a small pit in the light from a star, astronomers can use it to estimate the size of a planet.
The newly discovered earth is about 5,700 miles wide, which is about three-quarters of our planet. Follow-up observations with the High Accuracy Radial Velocity Planet Searcher (HARPS) in a telescope at La Silla Observatory in Chile allowed the researchers to find its mass.
The HARPS detector looks for subtle wobbles induced in their host stars by exoplanets that get stronger as the planet gets heavier.
With its mass and diameter in hand, the scientists calculated the density of GJ 367 b, showing it to be an outlier compared to most exoplanets. It is closer in size to Earth or Venus, but has a composition like Mercury, which is primarily iron.
“It’s a strange ball,” said Kristine WF Lam, an astronomer at the German Aerospace Center in Berlin. An article published Thursday in the journal Science.
Because it sits so close to its parent, one side of GJ 367 b is probably always facing the shining star. Dr. Lam added that daytime temperatures should rise to 2,700 degrees Fahrenheit, hot enough to melt rock and metal, making it a potential lava world.
GJ 367 b offers scientists a way to study how worlds closer to the stars form. The leading theory for how a place like Mercury was created is that early in solar system history, a rocky Earth-like planet formed near the Sun. The massive space rocks then punched this entity and grazed the earth from its crust and mantle. This means Mercury is actually a gigantic planetary core sitting by the fiery sun.
However, Dr. Valencia said the problem with such a scenario is that it doesn’t work completely. Collisions may have removed the outer layers of proto-Mercury, but the material doesn’t get very far. Trapped by the sun’s gravity, rocks and metals would stay close in orbit and eventually return to the object’s surface.
Dr. It’s possible to resort to special cases as to why this didn’t happen, but the presence of GJ 367 b and similar objects means that such planets aren’t exactly rare, Valencia said.
“We have to think about how you can reliably produce a SuperMercury and not the occasional one,” he added.
One possibility is that there is still something missing in the planetary creation models. Dr. Perhaps dense elements like iron somehow got closer to a star during his younger days, Valencia said. While worlds like GJ 367 b are starting to nudge scientists in such a direction, such an idea remains speculative for now, he added.
The team that discovered the small planet is already planning to make more observations about the system. They also want to use a giant telescope to pick up light from GJ 367 b, potentially revealing whether it has an atmosphere or whether its surface has actually melted.
Larger worlds have always been easier to detect than smaller ones, and researchers have found a number of giant Jupiter-like entities with all sorts of composition and orbital characteristics. Bizarre small objects like GJ 367 b continue to emerge as advanced telescope techniques usher in exploration at the other end of the size spectrum.
“It wakes you up to remember that these planets have their own stories,” said Jonathan Fortney, a planetary scientist at the University of California at Santa Cruz, who was also not involved in the study. “Another way to show that the ultimate planetary consequences can be very diverse.”