The discovery of two exoplanets orbiting the habitable zone about 16 light-years away | Sorae Portal site to space

A research team led by Alejandro Suárez Mascareño of the Canary Institute of Astrophysics (IAC) has discovered two exoplanets orbiting a relatively nearby star, about 15.8 light-years from Earth. Both planets are thought to orbit within the star’s habitable zone.

The research team reported the discovery of exoplanets “GJ 1002 b” and “GJ 1002 c” orbiting the red dwarf “GJ 1002” in the direction of “Cetacea”. The orbital period, minimum mass, and distance from the parent star (GJ 1002) for each planet are as follows.

● GJ 1002 b
Revolution period: about 10.3465 days
・ Minimum mass: about 1.08 times the mass of Earth
・ Distance from the main star: about 0.0457 AU

● GJ 1002 c
Revolution period: about 20.202 days
・ Minimum mass: about 1.36 times the mass of Earth
・ Distance from the main star: about 0.0738 AU

【▲ Comparison of planetary positions and habitable zones in the GJ 1002 system (top) and the solar system (bottom). The distances from the protostars to GJ 1002 b and GJ 1002 c are actually shorter than the average distance from the Sun to Mercury (about 0.39 AU), but this image has been resized to align with the habitable zones (IAC). Planets of the Solar System: NASA)]

The extent of the habitable zone varies from star to star. GJ 1002 b and GJ 1002 c both orbit very close to their parent star, GJ 1002 (less than 1/10th the distance from Earth to the Sun), but GJ 1002 has a mass about 0.12 times that of the Sun. A red dwarf star (spectral type M5.5 V) with a radius of about 0.14 times, a low surface temperature of about 3024 K (about 2751 °C), and the orbits of the two planets are in the habitable zone.

The newly discovered exoplanet is relatively close, about 15.8 light-years from Earth, so it may be possible to analyze the properties of GJ 1002 c’s atmosphere, in particular, by capturing the reflected light and thermal radiation from the planet. called . The European Extremely Large Telescope (ELT), which is under construction at the European Southern Observatory (ESO), will be used to check for the presence of oxygen in the atmosphere, said Junay González-Hernandy of IAC, who was involved in the study. of GJ 1002 c. We look forward to future observations by

■ The transit method and the radial velocity method used to monitor exoplanets

This time, the research team used two spectroscopic instruments, “Carmines” installed in the Observatory’s 3.5-m ColorAlto Telescope and “Espresso” installed in ESO’s “Very Large Telescope (VLT)”. We observed GJ 1002 using the radial velocity method (Doppler shift method) and discovered two exoplanets.

The “radial velocity method” is a method for indirectly detecting exoplanets based on the motion of the host star, which vibrates slightly in a circular motion during the rotation of an exoplanet. As the primary star oscillates with the planet’s orbit, the color of the light changes periodically, such as bluish when the primary star moves close to Earth and reddish when it moves away from Earth. Such changes in the star’s primary color can be detected by performing spectroscopic observations of the celestial body’s spectrum (the intensity of electromagnetic waves at each wavelength). In addition to the orbital period of an exoplanet, the minimum mass of an exoplanet can be obtained from observational data of the radial velocity method.

[فيديو يوضح كيف يتغير طيف النجم الرئيسي مع دوران كوكب خارج المجموعة الشمسية]
(Credit: ESO/L. Road)

Another “transit method” is to detect exoplanets based on small changes in the host star’s brightness that occur when an exoplanet crosses in front of the host star (the fixed star), which is an indirect detection method. By observing frequently occurring transits, we can tell the orbital period of an exoplanet from its period. It is also possible to obtain information such as the diameter of an exoplanet and the presence or absence of an atmosphere based on the transit star’s primary light curve (a curve showing the luminosity of a celestial body that changes over time).

[▲ فيديو يوضح كيف يتغير سطوع نجم بسبب عبور كوكب خارج المجموعة الشمسية]
(Credit: ESO/L. Road)

source

• Image credit: Alejandro Suarez Mascareno and Ines Bonet (IAC), NASA
• IAC – Espresso and Carmenes discover two potentially habitable outer Earths around a star near the sun
• INAF media – Two potentially habitable “Earths” 16 light years away
• A. Suárez Mascareño et al. Two moderately large Earth-mass planets orbit the nearby star GJ 1002 (astronomy and astrophysics)

Text / Takehiro Matsumura