Gliese 436 b is probably my favorite exoplanet. (not that it being my favorite is a big accomplishment on its behalf, especially as I am easily amused); however, I believe the same could be said for many individuals (laypeople and scientists alike). This exoplanet is a favorite of many, which is unsurprising as the planet is currently of the strangest, most inexplicable exoplanets we know of…and we know of some strange planets. For example, one exoplanet is known to contain some type of unknown substance that has made the planet darker than coal. Plus, with the number of potential candidates approaching quadruple digits, calling Gliese 436b the strangest is really saying something.
Before we delve into the strangeness that is Gliese 436 b, lets talk about it’s basic features…
The Neptune-sized planet orbits a cooler, less luminous red-dwarf star (dubbed Gliese 436), completing one full orbit in just 2 days and 15.5 hours. This short orbital period indicates that the planet in question is located very close to Gliese 436, perhaps orbiting it from an area that is roughly 13 times closer to the star than Mercury (the innermost planet of our solar system) is from the Sun.
Because of this close proximity, the planet’s surface temperature is expected to be around 400 degrees Celsius (752 F), which is sufficiently hot enough to permanently ward off water in liquid form. Our current models say that a planet like this, composed mostly of hydrogen gas (with such high surface temperatures), should have significant quantities of methane present in the atmosphere. Here is where Gliese 436 b presents us our first conundrum. The planet has more than 7,000 times less methane than it should. Yet, it does have a surprising abundance of carbon monoxide molecules.
And that is the other mystery… carbon monoxide should not be present to this degree, as it only becomes dominant with temperatures that exceed 900 degrees Celsius. According to a scientist from the Kepler team, “Carbon, when it is cold, likes to hold onto hydrogen, but if it is hotter it likes to throw off the the hydrogen and steal oxygen from, say, water molecules, to make carbon monoxide.” The cause of this perplexing discovery is still unknown, but whatever the case may be, the mystery of the missing methane still has astronomers scratching their heads.
Moving onward, as I mentioned before, the planet is similar in size to Neptune, but it is too compact to be composed largely of hydrogen (like typical gas-giants), yet is not compact enough to be considered a “super-Earth.” Therefore, astronomers believe the planet may host a large concentration of an exotic form of hot water-ice (now dubbed “Ice-x”). The water substance can remain solid despite the blisteringly hot temperatures experienced there. You read that right, water as a solid at temperature exceeding 400C/700F. How is that even possible?! Well, it may be that the immense gravity of the planet is strong enough to compress the trace amount of water vapor found in the atmosphere, ultimately allowing the substance to remain solid despite the temperatures.
However, this “ice” is not traditional in any regard, as it’s very hot and could totally melt your face off if you caught a drop of it in your mouth. And if I may, ice that can burn your face off is a little bit strange.