VLBA's Innovative Technique

The presence of TVLM 513b was confirmed using an astrometric technique, which involves detecting the star's “wobble” caused by the gravitational influence of the orbiting planet. A continent-wide array of radio telescopes was assembled specifically for this study, marking the first successful application of this method by radio astronomers in the search for exoplanets.

In June 2018, an 18-month observation campaign was initiated to study the star TVLM 513–46546, an ultra-cool star with less than one-tenth the mass of the Sun. This research integrated data from earlier studies conducted between March 2010 and August 2011. The wobble in the star's position indicated a Saturn-like planet orbiting it more closely than Mercury does in our solar system.

The Very Long Baseline Array, a network of radio telescopes stretching from Hawaii to St. Croix, provides astronomers with unparalleled resolving power, allowing for intricate detail observation. Image credit: J. Hellermann, NRAO/AUI/NSF

“Giant planets, such as Jupiter and Saturn, are typically rare around small stars like this one. The astrometric technique is generally better suited for identifying Jupiter-like planets in wider orbits, so discovering a lower mass, Saturn-like planet in a tighter orbit was unexpected,” explained Salvador Curiel from the National Autonomous University of Mexico.

To date, over 4,200 exoplanets have been discovered through various methods. The radial velocity technique analyzes the Doppler shift as stars move slightly closer or further away from Earth due to the gravitational pull from companion planets. Meanwhile, the transit technique observes dips in starlight as planets pass in front of their stars from our perspective on Earth.

James Maynard stands on the dish of a 25-meter radio telescope at Kitt Peak, one of the ten telescopes that comprise the VLBA network. Image credit: The Cosmic Companion.

“Our method complements the radial velocity technique, which is more adept at detecting planets in close orbits, while ours excels at identifying massive planets in wider orbits. Indeed, previous techniques have only identified a few planets with characteristics similar to the one we discovered. We believe that the VLBA and astrometric technique could uncover many more similar planets,” stated Gisela Ortiz-Leon from the Max Planck Institute for Radio Astronomy in Bonn, Germany.

As early as the 19th century, astronomers posited that it would be theoretically feasible to detect planets orbiting other stars using astrometry. While earlier attempts using this technique yielded inaccurate results, this recent discovery marks only the second confirmed exoplanet found through this method.

“The VLBA, with antennas separated by distances up to 5,000 miles, provided the exceptional resolving power and high precision necessary for this groundbreaking discovery,” said Amy Mioduszewski of the National Radio Astronomy Observatory.

James Maynard, the founder and publisher of The Cosmic Companion, is a native of New England who now resides in Tucson with his wife, Nicole, and their cat, Max.

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