Category: Extrasolar Planets

The study of extrasolar planets has led to some astounding discoveries, many of which have defied the expectations of astronomers and challenged our notions about the forms planetary systems can take. For example, the discovery of Jupiter-sized planets that orbit closely to their stars (“Hot Jupiters”) defied what astronomers suspected about gas giants. Previously, the general consensus was that gas giants form beyond the “Frost Line” – the boundary beyond which volatile elements (like water) freeze solid – and remain there for the rest of their lives.

Interestingly, this will happen when our Sun leaves its main sequence phase and enters its Red Giant Branch (RGB) phase. This raises the question of what happens to Hot Jupiters when their parent stars expand to become Red Giants. Using advanced 3D simulations, a team of researchers led by the Compact Object Mergers: Population Astrophysics and Statistics (COMPAS) consortium simulated how red giants will expand to engulf Hot Jupiters. Their findings could answer another mystery confronting astronomers, which is why some binary systems have one rapidly-rotating star with strange chemical compositions.

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 sampling 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 these have been discovered using indirect methods – like the Transit Method (Transit Photometry) and the Radial Velocity Method (Doppler Spectroscopy) – while the remainder has 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) network to detect a Jupiter-like planet orbiting 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. Moreover, this method allowed the team to create the first 3-dimensional architecture of a binary system and a planet that orbits one of its stars.

In the search for extrasolar planets, astronomers and astrobiologists generally pursue a policy of “follow the water.” This comes down to searching for planets that orbit with a star’s circumsolar habitable zone (HZ), where conditions are warm enough that liquid water can flow on its surface. The reason is simple: water is the only known solvent capable of supporting life and is required by all life on Earth. However, since the 1970s, scientists have speculated that there may be a class of rocky planets in our Universe that are completely covered in water.

With the explosion in confirmed exoplanets, scientists have been eager to find examples of this type of planet, so they study them more closely. Thanks to an international team of researchers led by the Institute for Research on Exoplanets (iREx) at the Université de Montréal, an exoplanet orbiting within its system’s HZ was recently discovered that could be completely covered in deep oceans. This “ocean world” (aka. “Waterworld”) could reveal things about the nature of habitability when it is the subject of follow-up observations using the James Webb Space Telescope (JWST).