470 light years away, a planet ‘darker than charcoal’

Named WASP-104b, the planet absorbs 97-99% of the starlight that hits its surface. It is so dark that the researchers cannot actually see the planet.

Written by Sowmiya Ashok | New Delhi | Updated: April 26, 2018 8:25:01 am
Planet Nine, solar system, Kuiper Belt, solar system super Earth, California Institute of Technology, Sun, Uranus, Neptune, Planet Nine mass, Planet Nine distance from Sun, interstellar space, elliptical orbits, Sun's equator, ice planets, outer solar system Researchers have suggested that it is probably a glowing purplish ember, according to a report in phys.org. (Representational)

A planet discovered in 2014 may be the darkest celestial body ever found, say researchers in the astrophysics group at Keele University, UK.

Named WASP-104b, the planet absorbs 97-99% of the starlight that hits its surface. The researchers suggest WASP-104b is even darker than charcoal and that it can be among the top-three darkest planets. It is so dark that the researchers cannot actually see the planet. They have suggested that it is probably a glowing purplish ember, according to a report in phys.org.

Researchers used data from NASA’s Kepler space telescope — “the K2 short-cadence data from Campaign 14” — to detect “phase-curve modulation in the light curve of the hot-Jupiter host star WASP-104.”

Hot Jupiters are a class of gas giants that have a mass similar to Jupiter and stay close and orbit their stars in less than 10 days. They are also relatively dark and most reflect 40% of starlight that reaches them. WASP-104b is tidally locked — one side always faces the star, the other side is colder and darker.

The research paper, recently uploaded to an academic preprint, says that the planet is “one of the least-reflective planets found to date”. The paper suggests that the planet’s reflective clouds have burnt off due to extreme proximity to its hot star and “rules out any highly reflective clouds” in WASP-104B’s atmosphere.

The paper suggests that this is in keeping with theoretical atmospheric models that suggest that the hazy layer around the planet is thick with atomic sodium and potassium that absorb all light around it. In other words, the distance between the planet and its star is an important factor in how dark it is.

The new finding adds to dark planets that have been discovered previously. For instance, the paper notes: “TrES-2b is one of very few hot Jupiters at least as dark as WASP-104b.” Discovered in 2011, TrES-2b orbits roughly 3 million miles from its hot star, reflecting less than 1% of any light that hits it.

“This is one of the darkest planets ever discovered — reflecting very little light from its host star,” PTI quoted Teo Mocnik, who led the research. “WASP-104b is interesting because it was not even seen,” he said. “When analysing the highly precise photometric data from Kepler, we were surprised not to see reflected starlight from WASP-104b.” The planet orbits a yellow dwarf star some 470 light years away from Earth.

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