This year ends with an extraordinary celestial event and the chance to talk about Jupiter and Saturn’s connection to asteroids. On 21 December, the planets Jupiter and Saturn will be so close to each other that they will appear to touch. Although the two planets draw close to each other every 20 years, this year will be their closest approach since 1623!
At dusk today, check out how close the planets appear already. You can locate them between the constellations of Sagittarius, the archer, and Capricornus, the sea-goat. Then, keep watching every clear night until 21 December.
What does this have to do with asteroids? Both planets have a large family of moons. In 2018, ten new one were discovered at Jupiter. The following year, 20 new moons were discovered around Saturn. Recently, a published study claims that Jupiter could have more than 600 moons with a diameter of less than 1 km!
Analysis indicates that many of the small moons orbiting Jupiter and Saturn are actually captured asteroids.
Jupiter’s strong gravitational field certainly makes this possible but passing asteroids or comets are not automatically transformed into moons.
In the case of Saturn, it’s also possible that some of the small moons may be fragments of ancient collisions between larger moons and external bodies, such as asteroids and comets.
Could Earth also catch an asteroid, and transform it into a second moon? Although our planet’s gravitational field is much smaller than a planet like Jupiter, it is possible. Asteroids 2006 RH120 and 2020 CD3, this one discovered a few months ago, are both thought to have been temporarily captured by the Earth.
Of course, the small moons captured by Jupiter and Saturn are not visible to a small telescope and while this rare celestial conjunction in December will be worth watching just for its own beauty, you can also use it to explain the similarities between asteroids and the small moons of these giant planets.
Illustrating your talk with images of asteroids and the small moons of Jupiter and Saturn taken by space missions will allow your audience to identify the similarities. So, inspire your audience to travel beyond the asteroid belt and marvel at the moons of the Solar System’s largest planets.
As 2020 draws to an end, make we all come together again next year – like Jupiter and Saturn. Have a good event!
Asteroid Day Global Coordinator
ABOUT THE AUTHOR:
Saulo Machado is the Asteroid Day Global Event Coordinator. Since 2016, Saulo has been the Brazil Regional Coordinator, where he helped organizers host their Asteroid Day events all over Brazil.
With a passion for astronomy and scientific dissemination, Saulo works as a business administrator in Fortaleza, Brazil. He is the Founder of the Astronomical Events Support Group (GaeA) and hosts Asteroid Day events in observatories, planetariums and astronomy groups throughout Brazil.