On the night of 11-12 December, the star Betelgeuse will disappear... for a few seconds

At around 2:15 in the early hours of 12 December, the asteroid Leona will pass in front of the red supergiant star Betelgeuse, a very unusual event that will be visible to the naked eye. The Institute of Astrophysics of Andalusia (IAA-CSIC) has organised a campaign to observe the phenomenon, which will make it possible to study both the asteroid and the star's atmosphere


During the night of December 11-12, 2023, the asteroid Leona will pass in front of the star Betelgeuse, a very rare event known as stellar occultation. The phenomenon, during which we will see Betelgeuse disappear for a few seconds, will be visible along a strip in southern Spain, from Murcia to Huelva. It will offer a unique opportunity to study both objects, and the Institute of Astrophysics of Andalusia (IAA-CSIC) has organized an observation campaign with mobile telescopes to obtain as much data as possible. Likewise, the IAA-CSIC participates in the Starblink citizen science project, which will develop outreach and observation activities for amateur astronomers and the general public, since this phenomenon can be recorded even with modest means such as digital cameras.

"Betelgeuse is not a big star, it's this: it's a giant. We can see it with the naked eye on the right shoulder, the red star, in the constellation of the Hunter, Orion. It is one of the brightest stars that can be seen with the naked eye. Betelgeuse is about the same size as Jupiter's orbit, and asteroid (319) Leona just so happens to be about the same angular size projected in the sky. Thus, the occultation will be something similar to when we see a solar eclipse, in which the Moon completely hides the Sun”, says René Duffard, a researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who participates in the observation campaign.

The asteroid (319) Leona, with an estimated diameter of about 65 kilometers, will pass in front of Betelgeuse and block its light for approximately ten seconds, depending on the observation location. This phenomenon offers a unique opportunity to study Betelgeuse's atmosphere and collect data on the shape and other characteristics of the Leona asteroid.

The phenomenon will be visible during the night of Monday 11 to Tuesday 12 December. In Spain it will begin to be visible at 02:15 in the morning, depending on the location from which it is observed. "It should be noted that this is a very nice event to observe even with the naked eye, with binoculars or a mobile phone. You just have to find a place where Betelgeuse is visible at 2 am", says René Duffard (IAA-CSIC). "You don't even have to leave the cities, because even with the enormous light pollution in our cities, Betelgeuse is usually visible", says Jose Luis Ortiz (IAA-CSIC).



All people interested in astronomy will be able to join this observation in the early hours of next Monday. The Starblink project will allow astronomical observation enthusiasts to share their data in a collective project. It has an observation guide, as well as resources on concealment and a form to participate. The project has been developed by the Granada Astronomical Society, the Institute of Astrophysics of Andalusia and the Descubre Foundation, and has the support of the Europlanet Society.

As it is a citizen science project, it will use a research methodology that allows obtaining scientific knowledge with the active participation of the general population. The more people who participate from the greatest number of places, the better the results obtained will be to achieve the scientific objectives of the project. These aim to specify the size and shape of the asteroid, specify its position in the sky and the distribution of brightness on the disk, as well as determine the physical characteristics of the Leona asteroid.

StarBlink is included as an initiative supported by the Andalusian Citizen Science Office within the Andalusia + Citizen Science project of the Descubre Foundation and the Pablo de Olavide University, co-financed by the Department of University, Research and Innovation and the Spanish Foundation for Science and the technology.



Instituto de Astrofísica de Andalucía (IAA-CSIC)
Unidad de Divulgación y Comunicación
Silbia López de Lacalle - sll[arroba]iaa.es - 958230676