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. 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.
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.
Shop Windows to the Universe Science Store!
Our online store
on science education, classroom activities in The Earth Scientist
specimens, and educational games
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 main mission was to explore Jupiter and...more
The Galileo spacecraft was launched in October 1989. So, Galileo has been in space more than 10 years and it has been orbiting Jupiter for more than five years. Galileo is still going strong! "We're proud...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 on October 29th at 2:19 p.m. EST. The weather was great as Discovery took 8 1/2 minutes to reach orbit. This was the United States' 123rd...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 want an answer from the Russian government. The necessary service module is currently waiting to be...more
A coronal mass ejection (CME) happened on the Sun early last month. The material that was thrown out from this explosion passed the ACE spacecraft. The SWICS instrument on ACE has produced a new and very...more