Location of µ2 Scorpii in the night sky. Credit: Wikimedia Commons: Thorsten Bronger
Ninety percent of all exoplanets discovered so far (there are now more than 5,000) orbit stars the same size or smaller than our sun. Giant stars do not seem to have planetary satellites, and this fact has serious implications for the way we understand the formation of the solar system. But is the lack of planets around the big stars a true reflection of nature, or is there some kind of bias inherent in the way we look for exoplanets that makes us miss them? The recent discovery of two gas giants orbiting a giant star called µ2 Scorpii suggests it may be the last.
µ2 Scorpio is a star with the naked eye – you can go out and look for it yourself – it is part of the tail of the constellation Scorpio, not far below the bright star known as Antares. µ2 Scorpii is a B-type star nine times the mass of the sun – large enough to one day explode into a spectacular supernova before collapsing into a dense neutron star.
Astronomers recently studied µ2 Scorpii as part of the B-Star Exoplanet Abundance Study (BEAST) and discovered two gas giants – one yet to be confirmed – in orbit around the star. This is the first system of its kind known to us.
Finding these planets was not easy. There are several methods used to detect exoplanets. The transit method allows us to catch planets as they pass in front of their star, which causes a momentary decrease in the brightness of the star from a terrestrial perspective. This method is best for finding planets very close to your star (if a planet takes 12 years to orbit its star – as Jupiter does – it will take 12 years to see the light fall again. Many. it is easier to find stars with orbits measured in days or weeks).
Meanwhile, the radial velocity method captures planets by observing a star swaying as the planets pull it by gravity, slightly shifting the star’s light spectrum to red or blue. But radial velocity is also biased toward finding planets very close to their host star.
Large stars with distant giant gas planets would be easily missed by both radial velocity and transit methods.
Fortunately, in certain situations, direct discovery of planets is possible. For this to work, the planet must be far enough away from its star so that it is not obscured by the prevailing light of the star. The planet must also be massive enough to be seen, and it must be young enough to be bright (young planets glow hot). Finally, the entire star system must be close enough to Earth for our instruments to capture them. This is how BEAST managed to find the two planets orbiting µ2 Scorpio, which is part of a star cluster that is not very far away.
What are the consequences of this discovery? Well, this is early evidence that this type of planet is not as rare as the data on exoplanets so far. If BEAST continues to find more gas giants like those around µ2 Scorpii, we will have to rethink which ones we consider to be the most common planetary bodies in the galaxy.
In addition, our current models of planetary formation do not easily explain the formation of the type of planet orbiting µ2 Scorpio. The model of planet-forming nuclei, in which dust slowly collects in the planet’s core for millions of years, should not be possible around massive stars, where protoplanetary disks scatter faster. In another model known as Gravitational Instability (GI), the protoplanetary disk is massive enough to become unstable under its own weight, collapsing into giant planets. This could happen much faster than the accumulation of the nucleus and may explain the planets around massive stars, but, as researchers suggest, the accompanying planets of µ2 Scorpii are not expected according to the mass distribution of objects generated by current GI models. ” These planets do not fit the models, so the models may need to be updated.
To summarize the significance of this discovery, it is clear that the variety of existing exoplanets is greater than we can currently find. Systems like µ2 Scorpii hint at this diversity and will force us to rewrite our models of planetary formation. With each new exoplanet added to our databases, we learn more and more about the complexity of the solar systems in our galaxy and improve our understanding of the mechanisms that work when planets are born.
Two new exoplanets with a mass of Saturn have discovered More information: V. Squicciarini et al, Enlarged planetary system around a supernova ancestor. arXiv: 2205.02279v1 [astro-ph.EP]arxiv.org/abs/2205.02279 Contributed by Universe Today
Citation: Even stars doomed to die as supernovae may have planets (2022, May 9) extracted on May 9, 2022 from
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