Free Astronomy Magazine March-April 2022

26 MARCH-APRIL 2022 ASTRO PUBLISHING geometric probability that Proxima b transits is about 1.5%. In 2017, a team led by David Kip- ping (Columbia University, Depart- ment of Astronomy) reworked Prox- ima Centauri observations collected over 40 days between 2014 and 2015 with the MOST Space Tele- scope, a very high-precision instru- ment measuring just 15 cm in di- ameter (MOST stands for Microvari- ability and Oscillation of Stars). Al- though this study did not reveal a photometric periodicity directly at- tributable to Proxima b, two iso- lated signals of candidate transits were identified with the expected depth for the transit of a body of similar size. Again in 2017, a team led by Yiting Li (Pennsylvania State University) presented the data obtained by ob- serving Proxima Centauri for 23 nights with a 30 cm robotic tele- scope at the Las Campanas Observa- tory. The research was inconclusive regarding Proxima b, but a transit candidate was identified, per- haps attributable to a second planet (not necessarily to one of the more recently discovered planets). In 2018, a team led by Hui-Gen Liu (Nanjing University, School of Astronomy and Space Sci- ence) published the results of 10 days of photometric moni- toring of Proxima Centauri with the Bright Star Survey Tel- escope at Zhongshan Station, Antarctica. Also in this case, a signal was found with the char- acteristics of a planetary transit and consistent with the orbital parameters of Proxima b de- duced from the variations in the radial velocity of its star, but the confidence level of the detected signal was not partic- ularly high. Once again, the photometric noise produced by Proxima Centauri’s magnetic activity was deleterious. Another study published in 2018 was that of David Blank’s team (James Cook University, North Queensland, Australia), who reworked over 300 observations of Proxima Centauri, collected by different telescopes around the world, in the period T ransiting exoplanets are detected as they pass in front of their star, causing a drop in starlight visible to a distant observer. The transit is repeated with a cadence that depends on the time taken by the exoplanet to orbit around its star. For example, under ideal conditions, any alien observer of our Solar System would have to wait one of our years to see a repeat of the Earth’s transit in front of the Sun. [ESA] D avid Kipping, the astronomer who, while examining MOST observa- tions with his team, highlighted two candidates transiting the Proxima Centauri disk. [Columbia University] G raphic depiction of the MOST Space Tele- scope orbiting the Earth. [Canadian Space Agency]