Astronomers using NASA's Kepler spacecraft have discovered the darkest known planet in the galaxy called TrES-2b located around 750 million light years away.

The findings published at Harvard-Smithsonian Center for Astrophysics mentions that the distant, Jupiter sized planet reflects less than one percent of the sunlight falling on it, making it blacker than coal or any planet or moon in our solar system.

"TrES-2b is considerably less reflective than black acrylic paint, so it's truly an alien world," states astronomer David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author on the paper reporting the research.

More than a third of the sunlight reaching the planet Jupiter is reflected due to the presence of bright clouds of ammonia. TrES-2b, on the other hand, lacks reflective clouds due to its high temperature. Ammonia clouds are not present near the planet due to its intense temperature (around 1,800° Fahrenheit or even more).

"It's not clear what is responsible for making this planet so extraordinarily dark," stated co-author David Spiegel of Princeton University. "However, it's not completely pitch black. It's so hot that it emits a faint red glow, much like a burning ember or the coils on an electric stove."

The research team studied the brightness of the TrES-2 system as the planet orbited its star and detected a subtle dimming and brightening due to the planet's changing phase.

Like the moon, the planet is believed to be tidally locked and hence, no side of the planet faces the star. Also, the planet shows changing phases as it orbits its star similar to earth's moon. This causes the total brightness of the star plus planet to vary slightly.