Astronomers affectionately name planets discovered around other stars after those in our solar system. For instance, the sun is referred to when a giant gas giant orbits a star, known as a Hot Jupiter. On the other hand, planets that are massive icy and gaseous entities located further from their star system are called Cold Neptune. Scientists have a keen interest in exoplanets that are several times larger than Earth, referred to as Super Earth.
Super Earths do not necessarily bear a resemblance to our planet. They do not have to reside in the habitable zone of their respective planetary systems, nor must they support life similar to Earth. Rather, they are defined by their dimensions; these super-Earths are larger than our planet yet smaller than Neptune, which is the smallest gas giant in our solar system. They can generally be rocky or icy, but may also possess gaseous characteristics.
In 2020, a group of scientists observed a star, dubbed TOI512, which is roughly twice as old and massive as our sun and appears slightly red. Their observations were conducted using the TESS satellite, which indicated that it contained two exoplanets. TESS works by monitoring selected stars over extended periods to analyze variations in their brightness. Scientists plot this brightness against time, analyzing the light curve to interpret periodic dips in brightness, indicating that an object passes in front of the star. By measuring the time between dips, astronomers can determine how quickly a planet orbits its star and how much light from the star is obscured.
Recently, an international team of scientists argued that TESS’s observations of TOI512 support different interpretations. They confirmed the existence and characteristics of a single Super Earth in the TOI-512 system instead of two exoplanets. Their interpretation of the light curve indicates that the exoplanet is located at approximately 7% the distance the Sun is from Earth. They suggested that regular dips in the TESS data for TOI512 occur about seven days apart, implying that the light blockage corresponds to a super-Earth about 1.5 times the size of our planet.
However, the light curve provides limited information about the exoplanet. To gather more details regarding its mass and composition, scientists examine how it exerts gravitational influence on its host star, observing the effect on the star’s emitted light through radial velocity measurements. They noted that the stronger the gravitational pull on the star, the larger the exoplanet. Consequently, this team followed TESS observations with radial velocity measurements from the ESPRESSO echelle spectrograph for rocky exoplanets.
By combining data from TESS and ESPRESSO, astronomers determined that the exoplanet orbiting TOI512 is approximately 3.6 times the size of Earth, with a similar density and an almost circular orbit. They estimated its surface temperature to be around 1,000 Kelvin, which is 736°C or 1357°F!
The team then modeled the composition of planets with these characteristics using statistical simulation techniques. In their model, scientists posited that the planets consist of four layers of varying sizes, including an outer gas envelope, an iron core, a silicate mantle, and water shells made of hydrogen and helium. They tested the model by generating 5,000 simulated stars that matched the properties of TOI-512, along with 2,000 simulated planets around each star.
Their findings revealed that the model could not replicate the properties of the TOI-512 exoplanet unless it featured a significant amount of surface water and a deep steam atmosphere. They suggested that this discovery challenges previous models of planetary layers, which assumed that rocky planets near stars lose both their atmospheres and water.
They proposed that this contradiction might imply that the planet is still actively shedding water, as earlier researchers have indicated that rocky planets can retain up to 20% of their original water for as long as a billion years. The team concluded that TOI512 is an excellent candidate for follow-up observations to determine if it is a steam planet or a model for future exoplanet studies.
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Source: sciworthy.com
