Nigerian Astrophysicist Identifies Possible Case Of Rings Around An Exoplanet.

Babatunde Akinsanmi (PhD student at the Institute of Astrophysics and Space Sciences (IA) and the Faculty of Sciences of the University of Porto)

Rings have not yet been discovered around exoplanets despite their prevalence around the giant planets of the solar system. However, an international team of researchers, led by Babatunde Akinsanmi (PhD student at the Institute of Astrophysics and Space Sciences (IA) and the Faculty of Sciences of the University of Porto) found statistical evidence that indicates that the exoplanet HIP 41378 f is similar to Uranus with a ring system around it, inclined by about 25 degrees, and extending from 1.05 to 2.59 times the diameter of the planet.

The work now revealed had the main objective of explaining the unexpectedly low density of the exoplanet HIP 41378 f making it seem as though it is made from cotton candy.

“These ‘cotton candy’ planets are a rare class of exoplanets, with densities much lower than that of the giant planets in the Solar System. It is difficult to explain these very low densities and that is why we decided to investigate what was happening ”, explained the Nigerian astrophysicist.

In fact, HIP 41348 f has the longest orbital period of the least dense exoplanets discovered to date and is estimated to be eight times less dense than Saturn (whose average density is already less than that of water), which would make it highly abnormal.

“What we found was that the presence of rings around this planet can explain the observed low density. The rings make the planet’s diameter look much larger when it passes in front of the star (during transit), ”explains Babatunde Akinsanmi. “When this information is combined with an estimate of planet’s mass, it leads to a very low density for the planet”, explains the astrophysicist, who is developing his research under a PhD:: SPACE grant.

Artistic Impression of the ring around the ExoPlanet. CREDIT: TÂNIA CUNHA/PLANETÁRIO DO PORTO – CIÊNCIA VIVA CENTER) / IA

For Susana Barros (IA), “HIP 41378 f is currently the best candidate we have for a planet with rings outside the solar system. And even if we are yet to “confirm the existence of these rings observationally”, the investigator believes that it is something that can be achieved “soon”. “Furthermore, this planetary system is very interesting because it has five planets in transit, with different sizes and possibly different compositions”, she adds.

“Our result for HIP 41378 f shows that the ringed planet hypothesis is just as plausible as the model suggesting it is the only planet, but the existence of rings makes the planet more ‘normal’ with a physically intuitive density. The rings around this planet might, however, need to be composed of porous rocky materials which are still speculative as it is different from the icy rings we have around the solar system giant planets. Therefore, extending this investigation to other ‘cotton candy’ exoplanets may reveal more ‘hidden’ rings, ”adds Akinsanmi.

Nuno Cardoso Santos (IA and Department of Physics and Astronomy at FCUP) further clarifies that “although at this moment we do not have a complete proof in hand, the observations and models we have developed suggest that it is quite possible that, for the first time, a ringed exoplanet has been discovered. A discovery that, while not being entirely unexpected, makes us dream. ”

The article can be found on the pre-print server and the journal link

About Babatunde Akinsami

Babatunde Akinsanmi obtained his Bachelor’s degree in Physics from the Federal University of Technology Akure in 2010. He was awarded the M.Sc. in Astronomy by the University of Porto in 2017 and has since begun a PhD in Astronomy at the same university in collaboration with the Institute of Astronomy in Porto (IA). He completed a 2-year Data science fellowship by the Large Synoptic Survey Telescope Corporation in 2019.

His main research interest is in the field of exoplanets involving the search and characterisation of exoplanets using the transit and radial velocity methods. He specifically works on detecting novel exoplanetary features such as rings, tidal deformation and rotation-induced oblateness in exoplanets.

He is a scientific officer at the Nigerian National Space Research and Development Agency (NASRDA).

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