Astronomers have discovered not one but two planetary systems with sun-like stars at their hearts.
Both systems contain mini-Neptune planets and one is home to a huge “super-Jupiter” world, all of which are many times more massive than Earth. Studying these realms could lead to a better understanding of how planets form and evolve around Sun-like stars – also known as ‘solar analogs’.
The discovery of the two systems was made using NASA’s Transiting Exoplanet Survey Satellite (TESS) and the 1.93-meter telescope at the Observatoire de Haute-Provence (OHP) in southern France. The OHP telescope has a good reputation when it comes to detecting extrasolar planets, or ‘exoplanets’. It is the instrument that astronomers use Michel Burgemeester and Didier Queloz In 1995, 51 Pegasi b was discovered, the first exoplanet to orbit a Sun-like star.
These two newly discovered systems are home to at least three exoplanets, named TOI-1736 b, TOI-1736 c and TOI-2141 b, each joining a exoplanet catalog that has grown to more than 5,500 entries since the mid-1990s.
“We report the detection and characterization of two planetary systems around the solar analogs TOI-1736 and TOI-2141 using TESS photometry data and spectroscopic data obtained with the SOPHIE instrument on the OHP’s 1.93 m telescope,” Institute of Astrophysics in Paris scientist and lead researcher Guillaume Hébrard wrote with his co-authors in an article published in the journal Astronomy and astrophysics. ‘We performed a detailed spectroscopic analysis of these systems to determine the precise radial velocities and physical properties of their host stars.’
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TOI-2141: A planetary system around an old star
The first planetary system discovered by Hébrard and colleagues is TOI-2141, located about 250 light-years from Soil and centered on a star similar in size to the sun but appears to be older than our star. We know this because TOI-2141’s star lacks chemical elements heavier than hydrogen and helium, which are known as “metals.” Our 4.6 billion year old sun, on the other hand, is highly enriched in such metals. With some calculations, the team realized that the metal ratio indicates that the newly studied star is about 7.5 billion years old.
The planet in this system, TOI-2141 b, was spotted crossing, or ‘transiting’, the side of its parent star, blocking some of the light coming from the star, obscuring the star from the telescope’s vintage point started to dim. The team was able to determine that this planet is about three times as wide as Earth, with a mass about 24 times that of our planet, making it a mini-Neptune exoplanet.
TOI-2141 b is about 20 million kilometers from its star, which is about 13% of the distance between Earth and the Sun. This means that mini-Neptune completes an orbit about every 18.3 Earth days, with this proximity also sending the temperature to about 840 degrees Fahrenheit (450 degrees Celsius).
This planet’s density and hot surface temperature indicate that it consists of a rocky core surrounded by an atmosphere filled with water vapor. So far, TOI-2141 b is the only planet found in the TOI-2141 system, but the team has not yet ruled out the possibility of other smaller planets orbiting the Sun-like star.
And as impressive as this first system is, the second planetary system discovered by the team is slightly more unique.
The exotic TOI-1736
Located around 290 light years from Earth, TOI-1736 is slightly more exotic than TOI-2141. At first glance, its primary star is unremarkable: it is about the same age as the Sun, about 4.9 billion years old, about the same size as the Sun, only 15% larger than our star, and even around the same temperature.
However, the TOI-1736 system is extraordinary because its main star is a second, smaller companion star, making this a binary system.
Enormous stars are commonly found in binary systems, but this dual lifestyle is rarer for Sun-sized stars, with only about 44% of solar analogs found with a companion. What’s even stranger is that TOI-1736’s companion star is so far from the main star that the exoplanets the team found actually only orbit the system’s main star.
More specifically, Hébrard and colleagues found two planets in this exotic galaxy. The first is another mini-Neptune with a width about 2.5 times that of Earth and a mass 13 times that of our planet. This planet, TOI-1736 b, orbits its star at a distance of only 10.5 million kilometers, which is about 7% of the distance between Earth and the Sun, completing an orbit in about 7.1 Earth days. TOI-1736 b’s proximity to its star means its temperature is around 800 degrees Celsius.
The system’s second planet, TOI-1736 c, is a so-called ‘super-Jupiter’ with a mass of about 2,800 times that of Earth and a width of about 9 times that of Earth. Jupitermaking it a whopping 99 times wider than Earth.
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TOI-1736 c is about 200 million kilometers from its star, which is about 1.3 times the distance between Earth and the Sun. This means that it completes an orbit around the Earth approximately once every 570 Earth days. This distance also places the planet in the habitable zone from its parent star – the distance at which water can exist in a liquid state. TOI-1736c is one gas giantso it doesn’t have a solid surface, but it could have moons with an atmosphere that allows liquid water to be present on the surface – perhaps making them habitable?
The answers to such questions will arrive time; Meanwhile, the team is focusing on some signs of a third planet that appears to lie around TOI-1736. Soon they plan to investigate this clue with the SOPHIE spectrograph at the OHP.