Astronomers Produce 3-D View of Binary Star-Planet System

Researchers have found a Jupiter-like planet orbiting a nearby star, which is part of a binary pair, by precisely tracing a small, almost imperceptible wobble in its motion through space.

Astronomers have spotted a Jupiter-like planet orbiting a nearby binary star by tracing a small, almost imperceptible wobble in its motion through space. Through the use of the Very Long Baseline Array (VLBA) of the National Science Foundation, they were able to determine the entire 3-dimensional orbit structure of a binary star pair and its planet. As a result of this discovery, astronomers said they might be able to gain valuable new insights into planet formation.

Astrometry, which produced this discovery, has been used to discover only three extrasolar planets so far. To date, there are well over 5,000 confirmed planets, according to NASA. Salvador Curiel, of the National Autonomous University of Mexico (UNAM) explained that other exoplanet discovery methods could not be used to determine the 3D architecture of a binary-star system that includes a planet.

Considering that most stars form planets in binary or multiple systems, Curiel explained, understanding systems such as this will help us understand planet formation in general.

In terms of astronomical distance, the two stars, together known as GJ 896AB, are only about 20 light-years apart. Both suns are red dwarfs star, one of the most common types of stars within the Milky Way. Among them, the bigger one, around which the planet orbits, has 44 percent of our Sun’s mass, while the smaller one has 17 percent. They orbit each other about every 229 years and are separated by about the same distance as Neptune is from the Sun.

GJ 896AB was studied using optical observations made between 1941 and 2017 in combination with VLBA observations from 2006 to 2011. A new set of VLBA observations was made in 2020. Because of the super-sharp resolution of VLBA’s continent-wide network, the stars’ movements were measured extremely precisely over time. Astronomers analyzed the data extensively to determine the orbital motions of the stars and their common motion through space.

An in-depth analysis of the larger star’s motion revealed a slight wobble indicating the presence of the alien world. Planetary gravitational effects cause the star to wobble. Throughout their orbits, stars and planets share a common center of mass. It is possible to detect the star’s motion around its barycenter when it is sufficiently far from the star.

Astronomers calculated that the planet orbits the star every 284 days and has twice the mass of Jupiter. The distance between it and the star is slightly less than that between Venus and the Sun. Its orbit is inclined by roughly 148 degrees from that of the two stars.

According to Gisela Ortiz-León, of UNAM and the Max Planck Institute for Radioastronomy, the planet orbits the main star in the opposite direction to the secondary star. “This is the first time that such dynamical structure has been observed in a planet associated with a compact binary system that presumably was formed in the same protoplanetary disk,” she added.

A detailed study of this and similar binary systems can provide important insights into the formation of planets in binary systems. A number of theories exist for the formation mechanism, and more data may be able to indicate which one is most likely, said UNAM researcher Joel Sanchez-Bermudez. Currently, models suggest that such a large planet is very unlikely to be the companion of such a small star, so perhaps those models should be adjusted,” he suggested.

As a result, astronomers hope to characterize more planetary systems using the astrometric technique. “The Next Generation VLA (ngVLA) is going to allow us to do much more work like this,” said Amy Mioduszewski of the National Radio Astronomy Observatory. “With it, we should be able to detect planets as small as the Earth.”

Astronomers reported their findings in The Astronomical Journal on September 1