This artist’s impression shows Proxima d, a planet candidate recently found orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The planet is believed to be rocky and to have a mass about a quarter that of Earth. Two other planets known to orbit Proxima Centauri are visible in the image too: Proxima b, a planet with about the same mass as Earth that orbits the star every 11 days and is within the habitable zone, and candidate Proxima c, which is on a longer five-year orbit around the star. Credit: ESO/L. Calçada
In August of 2016, astronomers with the European Southern Observatory (ESOCreated in 1962, the European Southern Observatory (ESO), is a 16-nation intergovernmental research organization for ground-based astronomy. Its formal name is the European Organisation for Astronomical Research in the Southern Hemisphere.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>ESO) announced that they had discovered an exoplanetAn exoplanet (or extrasolar planet) is a planet that is outside the Solar System, orbiting around a star other than the Sun. The first suspected scientific detection of an exoplanet occurred in 1988, with the first confirmation of detection coming in 1992.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>exoplanet orbiting in neighboring Proxima Centauri. Based on Radial Velocity measurements (aka. Doppler Photometry), the discovery team estimated that the planet was roughly the same size and mass as Earth and orbited with Proxima Centauri’s Circumsolar Habitable Zone (HZ). In 2020, this planet was confirmed by follow-up observations.
In that same year, a second exoplanet (Proxima c) roughly seven times the mass of Earth (a Super-Earth or mini-NeptuneNeptune is the farthest planet from the sun. In our solar system, it is the fourth-largest planet by size, and third densest. It is named after the Roman god of the sea.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Neptune) was confirmed. As if that wasn’t enough, an international team of astronomers with the ESO recently announced that they detected a third exoplanet around Proxima Centauri – Proxima d! This MarsMars is the second smallest planet in our solar system and the fourth planet from the sun. Iron oxide is prevalent in Mars' surface resulting in its reddish color and its nickname "The Red Planet." Mars' name comes from the Roman god of war.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Mars-sized planet orbits about halfway between its host star and Proxima b and is one of the lightest exoplanets ever discovered.
The research team responsible for this discovery includes astrophysicists from the National Institute for Astrophysics (INAF), the Instituto de Astrofísica de Canarias (IAC), the Consejo Superior de Investigaciones Científicas (CSIC), the Institute of Astrophysics and Space Sciences (IACE), and multiple universities and research institutes in Spain, Portugal, Switzerland, Italy, Canada, and Chile. The paper that describes their findings was published in the February 10th issue of the journal Astronomy & Astrophysics.
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According to the discovery team, Proxima d’s existence was first hinted at in 2020 when astronomers conducted follow-up observations of Proxima Centauri using a new instrument on the ESO’s Very Large Telescope (VLT) – the SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO). In addition to confirming the existence of Proxima b, astronomers spotted the first hints of a signal corresponding to an object with a five-day orbit.
Since the signal was so weak, the team had to conduct follow-up observations with ESPRESSO to confirm that it was due to a planet. Similar to Proxima b and c, the planet was confirmed using the Radial Velocity Method, where slight changes in a star’s position indicate the possible presence of planets. As João Faria, a researcher at the Instituto de Astrofísica e Ciências do Espaço and the lead author on the paper, explained in a recent ESO press release:
“After obtaining new observations, we were able to confirm this signal as a new planet candidate. I was excited by the challenge of detecting such a small signal and, by doing so, discovering an exoplanet so close to Earth. This result clearly shows what ESPRESSO is capable of and makes me wonder about what it will be able to find in the future.”
According to their results, Proxima d has a minimum mass of 0.26 Earth masses (twice the mass of Mars), making it the lightest exoplanet ever measured using the Radial Velocity Method. Because Proxima b is so light, its gravitational influence is so small that it only causes Proxima Centauri to move back and forth at around 40 cm per second (1.44 km/h; 0.89 mph). They also confirmed that it orbits its star at a distance of about 0.029 AU – 4 million km; 2,485,485 mi – or less than a tenth of Mercury’s distance from the Sun.
The ESPRESSO instruments collects light from all four 8.2 m telescopes of the ESO’s Very Large Telescope in Chile. Credit:
ESO/L. Calçada
The Proxima Centauri star system consists of three confirmed exoplanets, with orbital periods of five days (Proxima d), eleven days (Proxima b), and five years (Proxima c). As Pedro Figueira, an ESPRESSO instrument scientist at ESO in Chile, indicated:
“This achievement is extremely important. It shows that the radial velocity technique has the potential to unveil a population of light planets, like our own, that are expected to be the most abundant in our galaxy and that can potentially host life as we know it.“
This discovery not only demonstrates the way exoplanet studies have grown by leaps and bounds in recent years. It has also made Proxima Centauri even more appealing to astronomers. With three exoplanets (in six years) discovered around this closest stellar neighbor, the research potential is immeasurable. These activities will benefit tremendously from the James Webb Space TelescopeThe James Webb Space Telescope (JWST or Webb) is an orbiting infrared observatory that will complement and extend the discoveries of the Hubble Space Telescope. It covers longer wavelengths of light, with greatly improved sensitivity, allowing it to see inside dust clouds where stars and planetary systems are forming today as well as looking further back in time to observe the first galaxies that formed in the early universe.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>James Webb Space Telescope (JWST), which will start gathering light.
In addition, exoplanet surveys using the ESPRESSO instrument will benefit from the Extremely Large Telescope (ELT), which is scheduled to become operational by 2027. Between its 39.3 m (130 ft) primary mirror, 4.2 m (14 ft) secondary mirror, and an advanced suite of instruments – which includes a spectrograph, coronograph, and adaptative optics (AOs) – the ELT will play a vital role in expanding the exoplanet census.
Originally published on Universe Today.
For more on this discovery, see New Planet Detected Nearby – Orbiting Around Star Closest to the Sun.
Source: SciTechDaily
