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Telescopes Big and Small Aid Asteroid Research

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Research conducted by major observatories aided by amateur astronomers is helping to determine the composition of an asteroid named Sylvia.

Astronomers were able to determine the complex interior of Sylvia, which is located in the main asteroid belt between Mars and Jupiter, by studying the interaction of it with Romulus and Remus, two smaller asteroid moons orbiting Sylvia.

(Romulus and Remus are the twin brothers who were central characters in the myth about the foundation of Rome and the sons of Rhea Silvia, after whom the main asteroid appears to be named.)

“Combined observations from small and large telescopes provide a unique opportunity to understand the nature of this complex and enigmatic triple asteroid system,” said Franck Marchis, senior research scientist at the Carl Sagan Center of the SETI Institute and leader of the team conducting the study.

“Thanks to the presence of these moons, we can constrain the density and interior of an asteroid, without the need for a spacecraft’s visit.”

The researchers believe Sylvia, which measures about 167 miles across, has a spherical core of dense material surrounded by a fractured outer layer, Keck Observatory said in a press release.

Knowledge of the internal structure of asteroids is key to understanding how the planets of our solar system formed, Marchis said.

The findings were being revealed today at the 45th annual division of Planetary Sciences meeting in Denver.

Scientists said the project shows the value of combining observations from the world’s largest observatories with those from amateur astronomers using smaller telescopes.


Another example was contributions from small telescopes that provided data being used in a project involving a launch last month of a lunar probe.

In addition to the twin Keck and Gemini North observatories atop Mauna Kea, the Sylvia research also involved images obtained from the European Southern Observatory in Chile.

Then on Jan. 6, an “occultation” occurred as the triple asteroid system passed in front of a star. The passing was visible in a narrow band across the south of France, Italy and Germany.

Because observers at different locations could see different parts of the asteroid or its moons passing in front of the star, comparisons of the images allow precise measurements of their relative positions and sizes.

During the occultation, about 50 amateur astronomers agreed to try to record the event. A dozen of them were able to successfully observe the event lasting between four and 10 seconds, depending on the location of the observer in the band across southern Europe.

“Additionally, four observers detected a two-second eclipse of the star caused by Romulus, the outermost moon, at a relative position close to our prediction,” said Jérôme Berthier, astronomer at Observatoire de Paris. “This result confirmed the accuracy of our model and provided a rare opportunity to directly measure the size and shape of the moon.”

The observation revealed that Romulus is about 15 miles in diameter and shaped like a dumbbell. Scientists believe it may have been formed from fragments ejected from Sylvia by an impact several billion years ago.


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