The rediscovery of the ‘lost’ world is a step towards the search for habitable planets

The rediscovery of a lost planet could pave the way for the detection of a world within the habitable “Goldilocks zone” in a distant solar system.

The planet, the size and mass of Saturn with a thirty-five-day orbit, is one of hundreds of “lost” worlds that University of Warwick astronomers are promoting a new method of tracking and characterizing in hopes of find colder planets like those in our solar system, and even potentially habitable planets.

Reported in Astrophysical charts, the planet named NGTS-11b orbits a star 620 light-years away and is five times closer to its sun than Earth.

The planet was originally found on a planet search in 2018 by the Warwick-led team using data from NASA’s TESS telescope. This uses the transit method to detect planets, scanning the telltale drop in starlight that indicates an object has passed between the telescope and the star. However, TESS only scans most sections of the sky for 27 days. This means that many of the longer period planets only transit once in the TESS data. And without a second observation, the planet is effectively lost. The team led by the University of Warwick followed one of these ‘lost’ planets using the telescopes at the Next-Generation Transit Survey (NGTS) in Chile and observed the star for seventy-nine nights, and eventually caught the planet in transit by second time almost a year after the first detected transit.

Dr. Samuel Gill of the Department of Physics at the University of Warwick said: “By chasing that second downward transit we have found a longer period planet. It is the first of many of these findings that pushes for longer periods. These discoveries are rare but important, as they allow us to find planets of longer periods than other astronomers are discovering. Planets of longer periods are colder, more like planets in our own solar system. NGTS-11b has a temperature of only 160 ° C, colder than Mercury and Venus, although it is still too hot to support life as we know it, it is closer to the Goldilocks zone than many previously discovered planets, which often have temperatures above 1000 ° C “.

The Goldilocks zone refers to a range of orbits that would allow a planet or moon to withstand liquid water: too close to its star and it will be too hot, but too far and too cold.

Co-author Dr. Daniel Bayliss of the University of Warwick said: “This planet is in a thirty-five day orbit, which is a much longer period than we generally encounter them. It is exciting to see the area of Goldilocks within our eyes. “

Co-author Professor Pete Wheatley of the University of Warwick said: “The original transit appeared only once in the TESS data, and it was our team’s painstaking detective work that allowed us to find it again a year later with NGTS. NGTS has twelve states – State-of-the-art telescopes, which means we can monitor multiple stars for months, searching for lost planets. Traffic light fall is only 1% deep and occurs only once every 35 days, turning it off within reach of other telescopes. “

Dr. Gill adds: “There are hundreds of individual transits detected by TESS that we will be monitoring using this method. This will allow us to discover cooler exoplanets of all sizes, including planets more like those of our own solar system. Some of these will be small rocky planets in the Goldilocks zone that are cold enough to host oceans of liquid water and potentially extraterrestrial life. ”