The very small movement of a small star revealed the presence of an exoplanet, outside the solar system, orbiting close to a habitable place.
The planet is located only 36.5 light-years away (but too faint to be seen with the naked eye), and orbits a faint red dwarf called Ross 508. Astronomers confirmed the existence of a world 4 times the mass of Earth. Given what we know regarding the limits of planetary mass, this means that the outside world is likely terrestrial, or rocky, rather than gaseous.
It is unlikely that the exoplanet, called Ross 508b, is habitable as we know it, because there is a small chance of favorable conditions for the emergence of life on the surface of the planet discovered by the Japanese Subaru telescope.
However, the discovery, the first of its kind in a new survey using the National Astronomical Observatory of Japan’s Subaru Telescope (NAOJ) in Hawaii, demonstrates the effectiveness of techniques used to locate minor planets around fainter stars.
As of writing this report, 3,858 exoplanets have been confirmed using the transit method (when a planet passes in front of its host star, it blocks part of the light, and when it is observed from Earth, this change in light can be measured in order to discover the planet).
The second most fruitful method is the radial velocity method, also known as the wobble or Doppler method. When two objects are trapped in orbit, one does not rotate around the other, instead, they are orbiting around a mutual center of gravity. This means that the gravitational effect of any planets orbiting in its orbit causes a star, even the Sun, to instantly wobble slightly.
Thus, the starlight that reaches the Earth is shifted very slightly by the Doppler effect.
As it moves towards us, the light is compressed slightly to bluer wavelengths, and when it moves away, it is compressed to red wavelengths. This technique is better at detecting smaller exoplanets with wider orbits.
And in 2019, an international team of astronomers led by NAOJ set out to conduct a survey using the Subaru Telescope to search for dark red dwarf stars of exoplanets by identifying Doppler shifts in the infrared and near infrared. This allows searching for faint red dwarf stars, and therefore the oldest and most established ones.
Ross 508b, described in a research paper led by astronomer Hiroki Harakawa, using the Subaru telescope, appears to be a promising planet, regarding 4 times the mass of the Sun, orbiting its star every 10.75 days.
This is much faster than the Earth’s orbit around the sun, and as a result we are dealing with a star much smaller and cooler than the sun, and despite the much shorter distance between the two objects, the amount of radiation from the star that reaches the surface of “Ross 508b” is only 1.4 times that of the radiation The solar system that hits the Earth. So we can say that the planet is located at the inner edge of the habitable zone of its star.
We may soon learn more regarding the planet itself, as all indications are that Ross 508 b regularly passes in front of its star, which means, for example, that TESS will be able to see the resulting dips in it. Given the fact that TESS monitors this sector of the sky in April and May, scientists may already have data on the composition of the planet’s atmosphere.
Ross 508, which has a mass of 0.18 times the mass of the Sun, is currently one of the smallest and darkest stars around which a planet has been detected with radial velocity. So we might be overwhelmed with a whole wave of new exoplanet discoveries soon.
