Astronomers have made a rare discovery of a small, cold exoplanet and its massive outer companion – shedding light on its formation. The planets like the earth.

Exoplanet - ideal image.Exoplanet - ideal image.

Exoplanet – ideal image. Image Credit: Pixabay (Free Pixabay License)

These results include a planet with a radius and mass between Earth and Neptune, with a possible orbit around its host star of 146 days. The star system also has an outer, massive companion, 100 times the mass of Jupiter.

This is a rare discovery, as planets smaller and lighter than Neptune and Uranus are notoriously difficult to detect, with only a few identified to date. Such rare systems are particularly interesting for better understanding the formation and evolution of planets. They are considered an important step towards detecting Earth-like planets around stars.

A new planetary system has been discovered around the star HD88986. The star has a temperature similar to that of the Sun with a slightly larger radius and is bright enough to be seen by keen observers in dark sky locations across the UK, e.g. Brecon Beacons National Park.

The research, published in the journal Astronomy and Astrophysics, is led by Neda Haidari, an Iranian postdoctoral fellow at the Institut d’Astrophysic de Paris (IAP). In the UK, Thomas Wilson, a senior research fellow at the University of Warwick, co-led the analysis of satellite data, including the search for new planets. The team also includes researchers from 29 other institutions in nine countries, including Switzerland, Chile and the United States.

A cold, Neptune-like exoplanet

The planetary system includes a cold planet smaller than Neptune, a so-called sub-Neptune, HD88986b. This planet has the longest orbital period (146 days) among known exoplanets smaller than Neptune or Uranus with exact mass measurements.

Neda Hedari, IAP, explained: “Most of the planets we have discovered and measured their masses and radii have short orbits, typically less than 40 days. Our Solar System To provide a comparison, even Mercury, the closest planet to the Sun, takes 88 days to complete its orbit. How other systems and even our own solar system form and evolve.HD88986b, with its orbital period of 146 days, likely has the longest known orbit of the population of minor planets with accurate measurements.

Detected using HD88986b Sufi – A high-precision spectrograph (a machine that analyzes the wavelengths of light from exoplanets) at Haute-Provence Observatory, France. SOPHIE detects and characterizes exoplanets using the ‘radial velocity method’. Measurement of small motion variations of a star caused by planets orbiting the star.

These observations revealed the planet and allowed the team to estimate its mass to be about 17 times that of Earth.

Complementary observations obtained with NASA’s Space Telescope Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency (ESA) space telescope ExOPlanet satellite (CHOPS) indicates that the planet probably “transits” in front of its host star. This occurs when its orbit crosses the line of sight between Earth and the star, partially encircling the star – causing a decrease in its brightness that is observed and quantified. can go.

These observations from both satellites allowed the team to directly estimate the diameter of the planet, which is roughly twice that of Earth. The study’s findings rely on more than 25 years of observations, including data from the ESA. sang Satellite and cake Telescopes in Hawaii.

Additionally, with an ambient temperature of only 190 degrees Celsius, HD88986b provides a rare opportunity to study the composition of so-called “cold” atmospheres, since most atmospheres found for exoplanets are over 1,000 degrees Celsius. are

Due to the wide orbit of sub-Neptune HD88986b (as large as 60% of the distance from Earth to the Sun), HD88986b probably has rare interactions with other planets that may exist in the planetary system, and is massively exposed to strong ultraviolet. Less damage is done. The radiation from the central star may therefore have retained its original chemical composition, allowing scientists to explore possible scenarios for the formation and evolution of this planetary system.

Thomas Wilson, Department of Physics, University of Warwick, said: “HD88986b is essentially a mini-Neptune, between the orbits of Mercury and Venus. It is important to study its atmosphere to understand its similarities to our own planet Earth. becomes one of the best-studied small, cold exoplanets, paving the way for the . creates, in which Warwick plays an important role.”

Second, external partners

Astronomers also discovered a second, outer companion around the central star. This exoplanet is particularly massive (more than 100 times the mass of Jupiter), and has an orbital period of several tens of years. Further observations are needed to understand its nature and better determine its properties.

Thomas Wilson added: “We collected data from telescopes pointing at HD88986 for more than 25 years, making it one of the longest-studied exoplanet systems. This wealth of data extends beyond Jupiter. revealed a large second outer companion that could be important for the formation of a Neptune-like planet in our own solar system, similar to Jupiter.

A scientific article published in the journal Astronomy & Astrophysics by Heidari, Boisse, Hara, Wilson, Kiefer, Hebrard, Philipot et al. (2024), « The search for sophi northern exoplanets. XIX A system in which a cold sub-Neptune possibly transits the V = 6.5 star HD8898 [https://www.aanda.org/component/article? access=doi&doi=10.1051/0004-6361/202347897]

Source: University of Warwick