The orbit of an exoplanet around a star in a binary star system has been imaged in three dimensions for the first time. The planet orbits its star at a different angle to the plane of the two stars’ orbits, and this misalignment could provide clues about how planets form in binary systems.
The Exoplanet, GJ 896Ab (note the planet’s lower case b), discovered the binary system GJ 896AB (note the capital A and B of the two stars) located 20.3 light-years from Earth. Astronomers observed its motion Binary star system Additional data was collected by the Very Long Baseline Array (VLBA), a network of 10 radio telescopes across the United States, from 2006 to 2011, aided by archived optical observations from 1941 to 2017. The researchers also made new observations with the VLBA in 2020.
Discovered by astronomers led by Salvador Curiel of the National Autonomous University of Mexico (UNAM) the star GJ 896A moves through space, seemingly wobbly in its path. This wobble is caused by an orbit with 2.3 times the mass Thursday It completes one orbit every 284.4 Earth days. Between the planet and star is a common center of mass known as the barycenter; The motion of the star is the result of its motion around this common center of mass.
related to: 10 Surprising Exoplanet Discoveries
This technique of detecting the motion of stars through space and variations in that motion is called astrometry. Astronomy is the only way to interpret the orbits of a multi-star planetary system in three dimensions, as astronomers visually detect the motion and direction of the orbits.
Interestingly, the plane the planet orbits is misaligned by 148 degrees relative to the plane of the two stars’ orbits around each other.
“This means that the planet is moving around the main star in the opposite direction to the secondary star around the main star,” said Gisela Ortiz-Leon, an astronomer at UNAM and a team member at the Max Planck Institute for Radio Astronomy in Germany. Plan, said in a statement (opens in new tab).
Less than 4% of known exoplanets are in binary-star systems. This small ratio is partly because finding planets in binary systems is tricky, and models suggest that the existence of a companion star can truncate and destabilize a planet-forming disk.
“Maybe those models need to be adjusted,” said UNAM’s Joel Sánchez-Bermúdez.
One problem with forming such a system is that gas giants are thought to take 5 to 10 million years to release all their gas. Planetary disk around them. However, current models suggest that such a disk in a binary system can last less than 1 million years before gravitational tides from the companion star tear the disk apart.
And, in the case of GJ 896AB, two stars Red dwarfsThis results in the existence of a Gas giant planet More surprises in the system. Scientists think that red dwarfs lack the raw material needed to form giant planets, but the presence of a gas giant in this binary system suggests that planets form differently when there are two stars.
“More detailed studies of this and similar systems will help us gain important insights into how planets form in binary systems,” said Sánchez-Bermúdez.
There are currently two competing models for how binary systems and their planets form. One is called disc fragmentation, whereby the disc that originally formed a star and a planet becomes gravitationally unstable and splits into two separate discs, forming two stars and any planets around them.
Another model is called turbulent fragmentation. In this explanation, turbulence in the original cloud of gas leads to the formation of two or more dense masses of material that break apart to form stars and accompanying planets.
Now, these models require the GJ 896Ab to be misaligned by 148 degrees. Which is the best copy of the strange system that indicates how binary systems are formed.
The research was published on September 1 The Astronomical Journal.
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