- By Georgina Rannard
- Climate and science reporter
Confused by a mysterious planet that should have been destroyed, scientists believe they have discovered why it survived.
The planet – 8 Ursae Minoris b – was identified in the Milky Way in 2015.
But we’ll never see it, because it must have been engulfed by a nearby dying star.
Researchers now believe that 8 Ursa Minoris B escaped that fate because the dying star once had a companion that halted its growth.
“No planetary system like this has been discovered before. It’s a first, it’s very special,” explains Dimitri Veras, an astrophysicist at the University of Warwick who assisted lead researcher Mark Han from the University of Hawaii.
Scientists explain their theories about the fate of our own solar system.
Earth and the other planets in our solar system revolve around the Sun, a star filled with burning gases.
The sun is currently called a yellow dwarf and burns hydrogen but one day it will start to die. When that happens, it will become a red giant and expand significantly, consuming Mercury, Venus, and possibly Earth.
The extinction of the expanding star must have happened exactly to 8 Ursae Minoris b.
But a companion star appears to have saved the planet, explains Mark Hahn, who made the observations using the TESS space telescope.
Scientists believe that the planet once orbited two stars that were in different stages of life.
One is a red giant, which burns hydrogen until its helium core heats up and it begins to contract. The other is an old star, a white dwarf burning helium.
Researchers believe the helium core in the red giant ignited as it swallowed its companion star, halting its vigorous expansion prematurely.
8 Ursae Minoris b was then free to continue orbiting the attached star.
“The idea of a binary star merger came from effectively piecing together a puzzle,” explains Dr. Hahn.
After his observations, theorist Dimitri Veras and a team of about 40 scientists came up with possible explanations for the planet’s survival.
Another theory put forward by scientists is that the planet formed from material violently ejected by the merger of two stars.
But they say this is a very speculative idea.
“Most stars are in binary systems, but we still do not fully understand how planets can form around them. It is plausible that many more strange planetary systems may exist due to the influence of binary companions,” explains Dr. Hahn.
The findings are published in the journal Science Nature.