Coal absorbs about 95% of visible light. Black acrylic paint absorbs roughly the same. TrES-2b absorbs 99.9%—making it the darkest known object in the universe.

Located about 750 light-years away in the constellation Draco, this Jupiter-sized gas giant reflects less than 1% of the starlight that hits it. If you could somehow see it up close, it would appear as a near-perfect void—a ball of nothingness hanging in space. "It's darker than the blackest lump of coal, than dark acrylic paint you might paint with," said astronomer David Kipping. "It's bizarre how this huge planet became so absorbent of all the light that hits it."

But TrES-2b isn't entirely invisible. Because it orbits so close to its star—just 3 million miles away, compared to Mercury's 28 million miles from our Sun—its surface temperature exceeds 1,800°F (980°C). At that temperature, the planet emits a faint, eerie red glow, like a dying ember in the darkness.

Scientists believe the extreme heat prevents the formation of reflective ammonia clouds that make Jupiter so bright. The planet's atmosphere likely contains light-absorbing chemicals like vaporized sodium, potassium, and gaseous titanium oxide. But even accounting for all of these, no existing model fully explains why TrES-2b is so impossibly dark. According to Princeton researchers, "something that seems to be present and absorb light hasn't been accounted for in basic models." There's a missing ingredient in the recipe—and we still don't know what it is.