Exoplanet WASP-104b is one of the least-reflective planets ever discovered. First identified in 2014 according to the Open Exoplanet Catalogue, WASP-104b belongs to a class of “exotic worlds” known as “hot Jupiters.”

These are gaseous exoplanets the size of Jupiter, only considerably much hotter because of their close proximity to their parent stars, which they orbit in less than 10 days, NASA explains.

Initially “considered oddballs,” hot Jupiters turned out to be quite common. Yet, although we’re used to them by know, they remain “shrouded in mystery,” NASA points out.

One thing we do know about hot Jupiters is that most of them are tidally locked — one side of the planet always faces its parent star, making it the permanent day side — and that they’re relatively dark, absorbing about 60 percent of the starlight that reaches them, notes Science Alert.

Last year, hot Jupiter WASP-12b made headlines when astronomers found out that it absorbs at least 94 percent of the light. At the time, this exoplanet was called “spooky” and “weird” and was described as “pitch black.”

But WASP-104b really takes the cake on this one. A new research by Keele University in the U.K. revealed that WASP-104b absorbs more than 97 to 99 percent of light.

Pause for gasp.

The research, a six-page paper published in the Cornell University Library, describes the exoplanet as being “darker than coal” (seriously, that’s what they put in the title) and deems it “one of the least-reflective planets found to date.”

Hot Jupiter WASP-104b is Darker Than Charcoal: WASP-104b, a so-called Hot Jupiter, has been identified in a new research as one of the least-reflective planets found to date. Astronomers classify a planet as a "Hot Jupiter" that are gas giant... https://t.co/k0ceVoVl1y — Rumor About (@rumorabout) April 23, 2018

“From all the dark planets I could find in the literature, this is top five-ish. I think top three,” lead researcher and astrophysicist Teo Mocnik said in a statement.

The authors analyzed data from NASA’s Kepler Space Telescope K2 mission, specifically the short-cadence data from Campaign 14, and found out that WASP-104b is surrounded by a thick, hazy atmosphere made up of atomic sodium and potassium. These elements absorb light in the visible spectrum, making the planet very dark on the day side (the only side that sees any starlight).

Since the planet is extremely close to its host star, WASP-104b is too hot for clouds to form in its atmosphere (on the day side, that it), which means there’s almost nothing there to reflect the light.

In fact, the exoplanet orbits its parent star — a yellow dwarf located about 466 light-years away from Earth, in the Leo constellation, Science Alert reports — from a distance of only 2.6 million miles. Remarkably, this peculiar planet completes a full orbit in just 1.75 days.

The only hot Jupiter that’s darker than WASP-104b is an exoplanet dubbed TrES-2b, which only reflects 0.1 percent of the light from its parent star, notes Science Alert.

A study has been revealed that WASP-104b, a Hot Jupiter exoplanet, has been discovered as one of the darkest exoplanets ever seen. https://t.co/APuAP36iRm — the Context (@thecontextnet) April 21, 2018

The media outlet clarifies, however, that these planets are not actually dark in color. In fact, judging by their extreme heat, they more likely glow in “a deep, bruise-like purple or a dull molten red” hue, Science Alert points out.

But WASP-104b is not the only hot Jupiter with an impressive tale to tell. In December, the world was acquainted with “death planet” WASP-18b, the first hot Jupiter with no water and an upper atmosphere almost completely made up of carbon monoxide.

Equally baffling is the hot Jupiter known as Kepler-13ab, a planet where the atmosphere “snows” titanium dioxide, the active ingredient used in most brands of sunscreen. </s> WASP-104b, a so-called Hot Jupiter, has been identified in a new research as one of the least-reflective planets found to date. Astronomers classify a planet as a "Hot Jupiter" that are gas giant exoplanets, physically similar to Jupiter but that has a very short orbital period with less than 10 days. The close proximity to their stars and high surface-atmosphere temperatures resulted in the moniker "hot Jupiters."

Researchers a the Keele University in the UK found the unique characteristic of WASP-104b by analyzing Kepler's K2 short-cadence data from Campaign 14. The exoplanet's close proximity to its star, a yellow dwarf, is likely the reason for the darkness.

Most hot Jupiters including the WASP-104b are tidally locked. One side of the planet always faces its star, making it the permanent day side. In the case of WASP-104b, the distance is only 2.6 million miles from the star and it only needs 1.75 days for a full orbit, according to ScienceAlert. Lead researcher Teo Mocnik talked to New Scientist about discovery (paywall).

The WASP-104b exoplanet was discovered back in 2014, along with the WASP-106b.

The detailed research can be found in the paper titled "WASP-104b is Darker than Charcoal" authored by T. Močnik, C. Hellier, J. Southworth and published in the Cornell University Library under arXiv:1804.05334.
A study has been revealed that WASP-104b, a hot Jupiter exoplanet, has been discovered as one of the darkest exoplanets ever seen.