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On October 20th, 2021, 

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dozens of astronomers
 gathered near Las Vegas.

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They pointed their telescopes at the sky
 and waited for the moment

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that the light from a faraway star
 blinked out.

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It was an event so minuscule
 it would have been easy to miss.

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Yet the data gathered by scientists
 from those few seconds

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helped contribute to the success of NASA's
 Lucy mission.

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As the astronomers observed the star, 

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it appeared to blink out as asteroid
 Eurybates passed in front of it.

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Eurybates is one of seven Trojan asteroids

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Lucy will visit over
 the next twelve years. 

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The Trojans are clustered in two swarms
 that orbit the Sun at the same distance

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as Jupiter, though they're as far away
 from Jupiter as they are from the Sun.

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These asteroids are remnants
 of the early solar system

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and by analyzing them up
 close Scientists can hone the theory

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of how the planets formed
 and ended up in their current locations.

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As Eurybates eclipsed the star, 

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a phenomenon scientists
 call an occultation took place

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whereby a shadow the size of the asteroid
 passed over the region.

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The best known example of an occultation
 is a solar eclipse, which occurs

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when the moon passes
 between the sun and Earth, blocking

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the sun from our view. 

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Leading up to the occultation, astronomers
 predict the asteroid's shadow's

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path across Earth
 and set up dozens of telescopes

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along a line
 that's perpendicular to that path.

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Spread out under the asteroid's shadow,
 they count the seconds

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the starlight blinks out
 as the asteroid passes in front.

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Using the asteroid's known velocity,
 it is possible to calculate its width.

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By observing multiple occultations
 of the same asteroid, scientists can catch

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different sides of the asteroid
 and combine their two dimensional

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silhouette projections
 into a three dimensional shape model.

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Observing an occultation
 is one of the most reliable tools.,

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scientists have to gather information
 about Lucy's target asteroids

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and prepare for flybys of each
 of the mission's targets.

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The team will continue to 

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observe occultations until Lucy's
 last flyby of Patroclus in 2033.