Next time you marvel at the night sky, it might be a good idea to keep in mind that much of it —about 42 million stars— was mapped with the help of "amateurs."

 

But these are no ordinary amateurs - they helped professional astronomers produce a star catalog that measures the detailed characteristics of more than 42 million stars.

 

The survey came from the American Association of Variable Star Observers (AAVSO), an international nonprofit organization of star observers that has been collecting data for this map since 2009, Wired.com reported.

 

The survey as run from two telescopes in Chile and New Mexico and makes eight million stellar detections per night, generating terabytes of data each year.

 

AAVSO's latest release, made publicly available on June 8, covers 95 percent of the northern and southern sky. It expects to complete the project in 2014.

 

Wired.com said the catalog is focused on variable stars, a large and diverse class of stars that change in brightness over time.

 

Thus, astronomers need good information about variable stars to learn details about the lives of stars, such as their mass, temperature, and internal structure, that would otherwise be hard or even impossible to determine.

 

"Because they change in brightness so slowly, variable stars need to be continuously watched to determine their long-term behavior. Most astronomers don’t have the time or resources for such an undertaking, which is why amateur astronomers — who can monitor and follow up with each star — are so useful," Wired.com said.

 

Also, Wired.com said knowing about variable stars is valuable to professional astronomers as some variables expand over time, pulsating and stretching due to internal forces.

 

Understanding them allows astronomers to figure out the dynamics of stellar interiors.

 

Other variables dim when a companion star passes in from of them, eclipsing their light. These binary stars allow astronomers to calculate the mass and size of different stars.

 

Dark energy

 

Another type of variable star, called Cepheid variables, has given astronomers clues to one of the biggest mysteries in contemporary science: dark energy.

 

Cepheids are used to determine the distance to faraway galaxies, and using them astronomers have discovered that such galaxies are receding from us at increasing speeds, suggesting that the universe is accelerating as it expands. — TJD, GMA News