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What's the Largest Known Star?
Sirius A, the brightest star in our nighttime sky, along with its faint, tiny stellar companion, Sirius B.
Credit: NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester)

The heftiest, brightest known star is in the Pistol Nebula and is located 25,000 light-years away in the direction of the constellation Sagittarius. It is believed to be 100 times as massive as our Sun, and 10 million times as bright. The Sun's mass is about 2 X 10^27 tons, which is a 2 followed by 27 zeros, or 333,000 times as massive as Earth.

The brilliant star may have begun life weighing as much as 200 solar masses. Over time, however, it has violently shed much of its mass.

In fact, the radiant star has enough raw power to blow off two expanding shells of gas equal to the several solar masses. The largest shell is so big (4 light-years) it would stretch nearly all the way from our Sun to the next nearest star.

Despite its great distance from us, the star would be a stellar sight if not for the dust between it and the Earth. Astronomers used the infrared camera on NASA's Hubble Space Telescope to peel away the obscuring dust and reveal the Pistol star.

Astronomers are currently unsure how a star this massive could have formed and how it will act in the future.

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