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Asteroids and Asteroid Adelheid Occultation

This article appeared in the February 22, 2019 edition of the Davis Enterprise.

Asteroids and Asteroid Adelheid Occultation

NASA diagram of asteroid belts

By Vinita Domier

Special to the Enterprise


Asteroids are small, rocky objects that orbit the sun, mostly in the disc-shaped region between the orbits of Mars and Jupiter known as the asteroid belt. They are leftover space junk from our solar system’s planet-forming epoch around 4.6 billion years ago. Hence, asteroids are important to study as they are fossilized relics of the infant solar system.


Asteroids are minor planets found mostly in the inner solar system. Minor planets are astronomical objects orbiting the sun that are not classified as planets or comets.


There are relatively few large asteroids, known as planetoids, and millions of smaller ones known as planetesimals. The biggest four are Ceres, Vesta, Pallas, and Hygiea.


Asteroids are classified based on their spectra that indicate their chemical make-up. Most are C-type if they are predominately carbon, M-type if they are metallic, or S-type if they are silicate/stony in composition.


Asteroids are also classified based on their location: Main Belt asteroids are in the asteroid belt, Near-Earth Asteroids (NEAs) closely approach Earth, and Trojans asteroids orbit the sun with Jupiter.


There are around 19,000 known NEAs that are potentially hazardous if they come too close to Earth. Many NEAs and comets have collided with Earth in the past, causing destruction depending on their size.


The mass extinction of dinosaurs is attributed to an asteroid impact 66 million years ago. On February 20, 2019, a 280 feet wide NEA, dubbed 2013MD8, is expected to whiz a mere 3 million miles by Earth.


NASA’s OSIRIS-REx spacecraft rendezvoused with Asteroid Bennu on December 3, 2018 after a two-year journey and will return to Earth in September 2023 with samples of the asteroid. Japan’s Hayabusa2 approached Asteroid Ryugu on June 27, 2018 and will collect three samples of the asteroid by shooting projectiles onto the asteroid’s surface and collecting the ejecta. First sample was scheduled to be collected around February 22, 2019 and the spacecraft is scheduled to return in December 2020.


An occultation is an event that occurs when one object (like a minor planet) passes in front of another object (like a star) and temporarily obscures it from view. Occultations are useful for measuring the size and position of objects much more precisely than by other means. A cross-sectional profile of the shape of the object can be determined if observers at different nearby locations observe the occultation.


On Saturday, February 23 at 8:33pm, Asteroid Adelheid will occult a faint star in the constellation Monoceros (east of the Orion constellation) for a predicted maximum of 11.6 seconds. As both constellations are easily visible all night, amateur and professional astronomers in the nightside of Earth will be observing the occultation to add to the collective knowledge of the asteroid.


Please join the Davis Astronomy Club on Saturday, February 23 starting at 7:00pm at the Explorit Science Center (3141 5th Street, Davis for the discussion on asteroids, followed by the viewing Asteroid Adelheid occultation and the Orion nebula. Everyone is invited to the free meeting indoors, followed by a star party outdoors (weather permitting).



Explorit’s coming events:


●      Visit Explorit’s latest exhibition, Earth Explorations. Explorit’sExploration Gallery is open to the public every Wednesday, Friday, Saturday and Sunday, 1:00-5:00 p.m.  Admission is $5.00 per person; Explorit members, teachers and children 2 and under are free.



Explorit Science Center is located at 3141 5th St. For more information call (530) 756-0191 or visit, or “like” us on Facebook at

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