The darkest planet in the known universe would look as bright as a full moon if it were located in Earth’s solar system. Unfortunately, this planet is located 718 light years away from our solar system.
The planet, known as TrES-2b, probably absorbs 99.9 percent of the light that hits it, according to a report by David Spiegel, a postdoctoral researcher at Princeton U. and David Kipping, a post-doctoral researcher at Harvard U. Meanwhile, coal, one of the darkest materials on Earth, absorbs 95 percent of the light that hits it.
TrES-2b, called an “exoplanet” in scientific circles because it lies outside of our solar system, was discovered in 2006 and is one of approximately 150 “hot Jupiter planets.”
Hot Jupiter planets are exoplanets with masses that are near to or greater than Jupiter’s. They have temperatures of over 1,340 degrees Fahrenheit due to the proximity of their orbit to their respective stars.
TrES-2b is no exception, lying just 3 million miles from its star. For comparison, the distance between the sun and the Earth is 93 million miles, making the distance between TrES-2b and its star relatively short. This close proximity between planet and star helps heat TrES-2b to more than 2,200 degrees Fahrenheit, a temperature so hot that the planet glows thermally and would appear 3,000 times brighter than Venus, our solar system’s brightest planet, if it were closer to Earth.
The planet’s high temperature further prevents the formation of the ammonia clouds that surround Jupiter and consequently reflect over a third of the sunlight reaching it.
Instead, TrES-2b’s atmosphere contains light-absorbing chemicals such as vaporized sodium and potassium and gaseous titanium oxide.
Though other hot Jupiters are closer to their stars than most planets — most of these Jupiters are over 10 times closer to their stars than Jupiter is to the sun — Spiegel and Kipping suspect that there is a mysterious additional component in the atmosphere of TrES-2b that contributes to its extraordinary ability to absorb light.
This discovery is among the first of its kind to find visible light — in addition to the more commonly observed infrared light — coming from an exoplanet, Spiegel said. Burrows and Speigel said they believe that the optical light received from TrES-2b may be attributed not to reflection but to its thermal emission.
Their observations and analyses are the most definitive confirmation yet of the presence of some optical absorber in the upper atmospheres of hot Jupiters.
“This is not the first reporting of the mystery element,” Spiegel said in a Princeton press release. “But it is the first identification of how non-reflective it can make a planet.”
Spiegel’s findings have been published in Monthly Notices of the Royal Astronomical Society.