216 Kleopatra I Alexhelios and II Cleoselene
216 Kleopatra is a significant asteroid located in the asteroid belt between Mars and Jupiter, characterized by its unique dumbbell shape and classification as a rubble pile. Measuring approximately 217 kilometers (135 miles) in length, Kleopatra is notable for having two moons: the inner moon Cleoselene and the outer moon Alexhelios, both of which are relatively small, around 8 kilometers (5 miles) in diameter. The asteroid is named after the famous Egyptian queen Cleopatra VII, with its moons named after her children, Cleopatra Selene II and Alexander Helios.
Kleopatra's structure is not solid; instead, it is comprised of a collection of rocky debris held together by gravity, with an estimated 30 to 50 percent of its volume consisting of empty space. The formation of Kleopatra is believed to stem from the collision of two larger asteroids around 4.5 billion years ago, with the moons resulting from subsequent breakups of the asteroid during later impacts. The asteroid was first discovered in 1880, but its distinct shape and the existence of its moons were confirmed in the early 2000s using advanced telescopes. This captivating celestial body provides insights into the dynamics of asteroid formation and evolution in our solar system.
216 Kleopatra I Alexhelios and II Cleoselene
FIELDS OF STUDY: Astronomy; Astrophysics
ABSTRACT: Kleopatra is an asteroid that was discovered in 1880. It is a large asteroid that stretches 217 kilometers (135 miles) end to end. In 2008 astronomers discovered two moons orbiting Kleopatra, Cleoselene and Alexhelios. Astronomers once believed that all large asteroids were solid. However, to date, all asteroids that have been discovered to have moons are rubble piles held together by gravity.
An Asteroid with Two Moons
The asteroid Kleopatra is a rubble pile shaped like a dumbbell. An asteroid is a small rocky body that orbits the sun. Billions of asteroids, including Kleopatra, are found between the orbits of Mars and Jupiter, an area referred to as the asteroid belt. Kleopatra is orbited by two moons, Cleoselene and Alexhelios. Cleoselene is the inner moon and Alexhelios is the outer moon. The asteroid is named after the Egyptian queen Cleopatra VII (70–30 BCE), and the two moons are named after her twin children: Cleopatra Selene II and Alexander Helios.
A Rubble Pile
Kleopatra is 217 kilometers (135 miles) long, which makes it a fairly large asteroid. While most large asteroids are solid chunks of rock or metal, Kleopatra is actually a pile of rubble held together by gravity. Astronomers estimate that 30 to 50 percent of the asteroid is empty space. Of the rubble-pile asteroids, Kleopatra is one of the largest, second only to Sylvia, which stretches 280 kilometers (174 miles) across.
When astronomers discovered Kleopatra in 1880, they thought the asteroid had a tubular shape similar to a cigar. However, astronomers in 2000 determined that the asteroid’s shape was more like a thigh bone, with two wider ends and a thinner middle. In 2008, using the Keck II, a large telescope in Hawaii, scientists verified the thigh-bone shape of the asteroid and discovered its two moons, Cleoselene and Alexhelios. Each moon measures about 8 kilometers (5 miles) across.
Formation Theories
Scientists believe that Kleopatra is actually the remains of two rocky, metallic asteroids that smashed together following the formation of the solar system about 4.5 billion years ago. They theorize that the asteroid’s two moons are pieces of rubble that broke off, possibly when another collision caused Kleopatra to spin rapidly. Alexhelios may have broken off from the asteroid one hundred million years ago, and Cleoselene is thought to have formed more recently, possibly only ten million years ago.
PRINCIPAL TERMS
- asteroid: a rocky body that orbits the sun.
- Kleopatra: an asteroid that is a rubble pile with two moons, Cleoselene and Alexhelios.
Bibliography
Baldwin, Emily. "Asteroid Kleopatra Spawned Twins." Astronomy Now. Pole Star, 23 Feb. 2011. Web. 16 Feb. 2015.
Choi, Charles Q. "Asteroids: Fun Facts and Information about Asteroids." Space.com. Purch, 21 Nov. 2014. Web. 16 Feb. 2015.
"Kleopatra Gave Birth to Twins . . . Moons." Cosmic Log. NBC News, 23 Feb. 2011. Web. 16 Feb. 2015.
Redd, Nola Taylor. "Moons around Asteroid Reveal a Giant Rubble Pile." Space.com. Purch, 1 June 2011. Web. 16 Feb. 2015.
Sanders, Robert. "How Cleopatra Got Its Moons." UC Berkeley News Center. UC Regents, 22 Feb. 2011. Web. 16 Feb. 2015.
Schmadel, Lutz D. Dictionary of Minor Planet Names. 6th ed. Heidelberg: Springer, 2012. Print.
Whitt, Kelly Kizer. "Dog Bone Asteroid Kleopatra Makes a Fetching Portrait." Earth Sky, 13 Sept. 2021, earthsky.org/space/dog-bone-asteroid-kleopatra-makes-a-fetching-portrait/. Accessed 14 June 2022.