[ad_1]
Nature loves patterns, both small and large. Take the Fibonacci sequence, for example – the repeating pattern of numbers in which each subsequent number sums the sum of the previous two. The formula appears in the spiral shells of Nautilus, but also in the arrangement of the planets of the solar system, whose distances roughly align with the ratios of the Fibonacci numbers.
But the approximate timing of our planets is nothing compared to the precise alignment of five newly discovered exoplanets, which orbit their parent star with such perfect harmony that it almost seems odd. According to a study published in the scientific journal Astronomy & Astrophysics, a solar system discovered by NASA’s Transiting Exoplanet Survey Satellite hosts at least six planets, five of which orbit the star – known as TOI-178 ( or TESS Object of Interest 178) – in a specific report. This is known as a “chain of resonances,” or a series of occasions in which planets orbit a star while maintaining a beat with each other.
“A resonance between two planets is what happens when one performs a certain integer number of orbits while the other also does,” wrote Dr Nathan Hara, an astrophysicist at the University of Geneva and co- author of the article, at Salon. “They therefore periodically find themselves in the same configuration and the strongest attraction between them is therefore always in the same direction.”
There are a few details that make the new discovery so striking. One is the fact that five planets are involved instead of two; as Hara explained, this makes it “one of the longest known chains” of resonant planets. In the case of the exoplanets surrounding TOI-178, they dance to the rhythm of 18: 9: 6: 4: 3. This means that each time the innermost planet in the chain makes 18 orbits around TOI-178, the next one in a row makes nine orbits, and the next one makes six orbits, and so on.
The discovery is also significant because “in known chains of resonance, the further the planet is from the star, the less dense it is, as in the solar system: Mercury, Venus and Earth, Mars, have a higher density than Jupiter , Saturn, Uranus and Neptune. “The stars orbiting TOI-178 in synchrony, on the other hand, have unusual comparative densities.
“The innermost planets are the densest, but then you have a planet with a very small density similar to Saturn, and then it rises and falls,” Hara told Salon. “It doesn’t shatter our understanding of planetary formation, but it is certainly confusing.”
He also told Salon that the discovery was useful to scientists because TOI-178 is an exceptionally bright star – in fact, the brightest star known to have resonant chains in transit.
“Here, ‘in transit’ means that the planet passes between the star and the observer, so that the stellar luminous flux measured by the observer periodically decreases,” Hara explained. “This way you also get an estimate of the radius of the planet. The fact that the star is brighter means that we can get information with other measurement techniques.”
Hara told Salon that, in addition to TESS, the discovery was made possible by recent advances in astronomical technology, including a European Space Agency telescope called CHEOPS, which launched in 2019, and a spectrograph from tip known as ESPRESSO which has been operational since 2018.
“This one measures the speed of the star in the direction of the line of sight and has unprecedented precision,” Hara explained. “We could not have performed mass measurements of the planets in the system with the previous generation of spectrographs, or at the cost of extremely long campaigns.”
As to how the resonant chain on the planets exists, Hara told Salon he has a partial guess.
“The formation of resonant chains is believed to result from formations of planets at wider separations of the star which then migrate together inward and are trapped in resonance with each other,” Hara wrote. “As to the fact that densities don’t monotonically decrease as you move away from the star, we don’t really have a convincing explanation yet.
[ad_2]
Source link