Exoplanet TrES- 2b4 min read

Every planet has some feature distinctive to it that makes it a source of enigma. In this case, the exoplanet TrES-2b’s claim to fame is its reputation of being the darkest ever planet known, whose hue is even blacker than coal! Revolving extremely close to its star, having a size akin to that of Jupiter and present in the Draco constellation, TrES-2b falls into the category of “Hot Jupiter” planets, whose temperatures can soar to an overwhelming 980 degrees Celsius, as opposed to the gelid temperature of minus 145 degrees Celsius of the Jupiter in our Solar System.


TrES-2b, which exists approximately 750 light years from the earth, was found by a Kepler spacecraft. This planet is so dark that it is less reflective than the blackest of acrylic paint. In fact, it is said to reflect less than 1 percent of the light that falls upon it! In other words, it has an infinitesimal reflectivity, also known as albedo. Jupiter, on the other hand, reflects about half of the sun’s light due to the presence of ammonia, thereby making it appear to be streaked by bright red and white clouds. The earth itself reflects around one third of the light it receives, thus imparting to it the bright, striking blue as can be seen from space. However, TrES-2b still emanates a very faint, red glow, like a smoldering ember, which rather than illuminating it and making it more approachable, only adds to its spine-chilling aura of mystery and fear. This glow is due to the scorching heat on its surface, which orbits its host star at a distance of only 3 million miles (the earth is 93 million miles away from the sun).


Scientists and astronomers have been baffled by the chemical reactions and formations that must be taking place within TrES-2b that lend such a deathly shade to it. They believe its atmosphere is composed of gases that absorb the star’s incoming radiation, such as vaporized sodium, potassium, and titanium oxide. These gases very efficiently do away with an overwhelming majority of the light that hits this perplexing planet. All the same, the presence of these gaseous elements alone is not enough to completely explain the fact that TrES-2b absorbs almost all of the light that falls on it, consequently leading experts to believe that there are some inexplicable, ongoing processes and reactions swirling amid the depths of this planet that are unknown to humankind as of now. It has been speculated that the existence of these light-absorbing compounds can also be attributed to the intense heat arising from its neighboring star. In the words of David Spiegel of Princeton University, “it really is a mystery”. And as described by the astronomer David Kipping, “If we could see it up close it would look like a near-black ball of gas, with a slight glowing red tinge to it—a true exotic amongst exoplanets”. Kipping also said- “It’s bizarre how this huge planet became so absorbent of all the light that hits it”.

TrES-2b was discovered on 21 August, 2006 by the Trans-Atlantic Exoplanet Survey (TrES), which employed a detection system that marked the transit of the planet across its star. This black orb, which is believed to be a tidally locked planet (like the orbit of the moon around the earth), was proved to be the darkest planet yet due to the precise observations of the spacecraft Kepler. On closely inspecting the images taken by Kepler and the planet’s orbits, astronomers discovered that there was a surprisingly small amount of lighting and dimming that took place when TrES-2b revolved around its star, although there was enough to corroborate that there was a cause behind it. As a matter of fact, when this giant crosses in front of its star, the star’s darkening is “so small that it’s like the dip in brightness we would see with a fruit fly going in front of a car headlight”. In contrast, there would have been much larger fluctuations had the planet been more reflective or had a higher albedo. And this led to the discovery of one of the most alien worlds known to humanity- a planet darker than the darkest shade we know. It redefines our definition of “an alien world”- from one of rocky, Martian landscapes to a spiraling sphere of infinite darkness, which makes itself known to mankind by a faint, crimson glow.

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