Astronomers unveil the first 3D model of a planet orbiting a binary system

To date, 5,084 extrasolar planets have been confirmed in 3,811 planetary systems, with another 8,912 candidates awaiting confirmation.

These discoveries have provided astronomers with a detailed sample of the types of planets that exist in our Universe, ranging from gas giants several times the size of Jupiter to smaller rocky bodies like Earth.

So far, the vast majority of them have been discovered using indirect methods – such as the transit method (transit photometry) and the radial velocity method (Doppler spectroscopy) – while the rest have been detected using various other means.

In a recent study, an international team of astronomers used the National Science Foundation’s (NSF) Very Long Baseline Array (VLBA) to detect an orbiting Jupiter-like planet in a binary system (GJ 896AB) located about 20 light years from Earth. .

Using a method known as Astrometry, the team managed to detect this planet by the “wobble” it makes as it orbits the larger of the system’s two stars. Additionally, this method allowed the team to create the first three-dimensional architecture of a binary system and a planet that orbits one of its stars.

The research team was led by Salvador Curiel Ramirez, a researcher at the Institute of Astronomy of the National Autonomous University of Mexico (UNAM). He was joined by colleagues from UNAM and researchers from the Max Planck Institute for Radio Astronomy (MPIFR) and the National Radio Astronomy Observatory (NRAO).

The paper describing their research, titled “3D Orbital Architecture of a Dwarf Binary System and Its Planetary Companion,” was published September 1 in The Astronomical Journal.

The system under study, GJ 896AB, is made up of two red dwarf stars orbiting each other. The larger of the two, the one whose orbit is that of the Jupiter-like exoplanet (GJ 896 Ab), is about 44% as massive as our Sun, while the smaller is about 17% as massive.

They are separated by a distance close to the distance between Neptune and the Sun (~30 AU) and have an orbital period of 229 years. As Curiel explained in an NRAO press release, the 3D mapping they performed could not be done with other methods of exoplanet discovery.

“Since most stars are in binary or multiple systems, being able to understand systems like this will help us understand planet formation in general,” he said.

Additionally, M-type stars (red dwarfs) are the most common in the Universe, accounting for about 75% of the stars in the Milky Way alone.

These low-mass, dimmer stars can remain in their main-sequence phase for up to 10 trillion years and are notable for supporting smaller rocky planets – such as Proxima b and d and the TRAPPIST seven-planet system -1.

For their study, Curiel and his colleagues combined VLBA data obtained between 2006 and 2011 (and new data obtained in 2020) with observations made of the system between 1941 and 2017.

The resolution provided by the ten VLBA telescopes across the United States has produced extremely accurate measurements of star positions over time.

They then carried out an in-depth analysis of the data which revealed the orbital motions of the stars and their common motions in space. This process, where the position and proper motion of stars are measured, is known as Astrometry.

Their detailed assessment of the larger star’s motion showed a slight wobble resulting from a gravitational effect on the star, which revealed the existence of the planet orbiting it. Based on the level of gravitational influence, the team calculated that this planet is a gas giant, about twice the mass of Jupiter.

They also determined that it orbits its parent star at a distance slightly less than that of Venus from the Sun, has an orbital period of 284 days, and is included within about 148 degrees of the orbits of the two stars.

“This means that the planet is moving around the main star in the opposite direction to the secondary star around the main star,” said co-author Gisela Ortiz-León, a researcher at UNAM and at MPIA.

“This is the first time that such a dynamic structure has been observed in a planet associated with a compact binary system that presumably formed in the same protoplanetary disk.”

The astrometric technique will be a valuable tool for characterizing more planetary systems, which will benefit from observatories like the Next Generation Very Large Array (ngVLA) project.

This massive array will consist of 244 18-meter (59ft) dishes spread over a distance of 8,860km (5,505 miles), with an additional short-spaced array of 19 6-meter (20ft) dishes at the heart of the telescope.

The improved sensitivity will allow astronomers to detect smaller rocky planets that orbit closer to their stars – where “Earth-like” planets are most likely to reside. Says co-author Joel Sanchez-Bermudez of UNAM:

“Further detailed studies of this and similar systems can help us gain important insights into how planets form in binary systems. There are other theories for the mechanism of formation, and more data may possibly indicate which is the most probable.

In particular, current models indicate that such a large planet is very unlikely to accompany such a small star, so perhaps these models need to be adjusted.”

This article was originally published by Universe Today. Read the original article.