The asteroid Ida, with its moon, Dactyl. The image was taken by Galileo in 1993.
Click on image for full size
Courtesy of NASA/JPL
Moon Found Orbiting Asteroid
News story originally written on October 11, 1999
A moon was discovered orbiting the asteroid, Eugenia. This is only the second time in history that a satellite has been seen circling an asteroid. A special mirror allowed scientists to find the moon from a telescope on Earth.
The mirror corrects for the blurring caused by Earth's atmosphere. This effect is called adaptive optics. The Hubble Telescope was originally launched so scientists could see objects without looking through the atmosphere. Now, they can study objects from Earth as well.
Making this discovery with the newly developed adaptive optics moves ground-based astronomy to the forefront in exploring neighboring objects in our solar system," said Vernon Pankonin, manager of NSF's planetary astronomy program.
Asteroid satellites are very difficult to find. The first one, called Dactyl, was discovered by the Galileo spacecraft in 1993. It orbits the asteroid Ida. Eugenia's moon was even harder to find, because the asteroid is much brighter than its moon. It's like looking for a flashlight beam in sunlight.
Now that the moon has been found, scientists can use it to calculate Eugenia's density. It turns out that the asteroid is very light and not much denser than water. It is most likely made of packed rock or ice.
This is only the second one known, and we've searched for a couple of decades already," said David Merline of the Southwest Research Institute based in San Antonio, Texas.
Shop Windows to the Universe Science Store!
Our online store
includes fun classroom activities
for you and your students. Issues of NESTA's quarterly journal, The Earth Scientist
are also full of classroom activities on different topics in Earth and space science!
You might also be interested in:
The Galileo spacecraft was launched on October 19, 1989. Galileo had two parts: an orbiter and a descent probe that parachuted into Jupiter's atmosphere. Galileo's primary mission was to explore the Jovian...more
The Galileo spacecraft was launched in October 1989, aboard the shuttle Atlantis. Galileo has been orbiting Jupiter for more than five years and it is still going strong! "We're proud that this workhorse...more
When one object is in orbit around another object, the orbit is usually an elliptical orbit. For example, all of the planets in our Solar System move around the Sun in elliptical orbits. An ellipse is...more
It was another exciting and frustrating year for the space science program. It seemed that every step forward led to one backwards. Either way, NASA led the way to a great century of discovery. Unfortunately,...more
The Space Shuttle Discovery lifted off from Kennedy Space Center at 2:19 p.m. EST, October 29th. The sky was clear and the weather was great as Discovery took 8 1/2 minutes to reach orbit for the Unitied...more
A moon was discovered orbiting the asteroid, Eugenia. This is only the second time in history that a satellite has been seen circling an asteroid. A special mirror allowed scientists to find the moon...more
Will Russia ever put the service module for the International Space Station in space? NASA officials are demanding an answer from the Russian government. The necessary service module is currently waiting...more