Search the Community

Some may notice I've been throwing out the phrase "Hyper Earths" several times over the last few weeks. I bet many of you want to know what exactly I'm talking about, so today I will describe a new potential planet type and the multiple confirmed examples of these hellish abominations. This first began back in May 22nd, 2017 on Exoplanet Explorers, a citizen science project on Zooniverse where users go through processed parts of K2 light curves to try and find transiting planets. After many minutes searching, I came across something that caught my eye. A light curve only known back then as Subject 7673371 showed quite odd dips in starlight every 0.49 days. They were rather small with a depth of about 400 parts per million, but were both clear and noisy - a combination very rarely seen. It looked so odd an so peculiar that I wondered if this was a plant at all, but the folded transit showed some good potential. I felt no other choice but to classify this as a planetary candidate as I went to analyze what I had found. Using ExoFOP data, I discovered that the parent star was a F-class main sequence star known as EPIC 220395236, with a radius of 1.465 times that of the Sun and a temperature of over 6,000 Kelvin. Using the helpful Planetary Calculator and the parameters I already had, I was able to characterize the planet. The results were terrifying. This was a giant planet at 3.18 RE orbiting so close to the star that temperatures reached an absolutely horrific 2,811 Kelvin, or 4,600*F. This is hotter than TRAPPIST-1 by nearly 300*K! The frightening data that was staring me in the face led me to give this world a proper name I had been waiting to use for a long time: Tartarus, named after the mythological Greek pit of Eternal Damnation, a hellish place where the most horrific beings and evildoers in the Universe were locked up to experience horrifically ghastly tortures for all of eternity. I had no idea how appropriate that name would become. Some time later (like a few minutes ) I realized something: Tartarus was breaking the laws of the Universe. A planet of its size should most definitely be a gaseous world like Neptune, but with such an extreme temperature it would have to be incredibly puffed up. However, if that were the case, its actual mass would be very similar to that of Earth's. That would be too small to hold onto all those gases in such a hostile environment and would probably evaporate, reducing its radius.This is not what appears to be happening. Only one option remained: Tartarus was an ENORMOUS rocky planet, and I truly mean enormous. In order for it to survive in an environment with thousands of times the stellar flux Earth gets, it would have to be at LEAST 120 ME, more than that of Saturn and HD 219134 h (Nerrivik). This would lead to a density of 20.576 g/cm3 and around 11.8667 gees of gravity. The conditions on Tartarus would be beyond hellish if the giant mass theory is correct. Most of the planet would be a searing, molten sea of gold, iron, rocks, and most metals in existence. The only land would be continent-sized volcanoes made purely out of Tungsten, the only metal that can survive the conditions here. Volcanic eruptions would be incredibly frequent and far more powerful than anything here on Earth, blowing out huge chunks of semi-molten metals and smothering clouds of toxic plasma. The front side would be scorching with temperatures of at LEAST 5,200*F, hot enough to vaporize iron and tin. This vapor would be pushed through a low but incredibly dense, soupy atmosphere by winds caused as a result of starlight exposure powerful enough to push the planet's atmosphere. Winds would be slow, but pack a punch as hard as getting hit by an asteroid. In "cooler" regions, the metal vapors in the atmosphere would condense into scorching pebbles and globs of molten iron and tin, which would rain SIDEWAYS in a turbulent, superheated atmosphere crackling with violent lightning storms. Overall, quite possibly the most hellish abomination of a planet ever found. This incredible discovery is what led me to make the Hyper-Earth planet class. So, what exactly is a Hyper-Earth? It would be the next step up from a Mega-Earth, which starts at 10 ME. For an object to be a Hyper-Earth, it must have at least 50 times the mass of Earth and NOT be a gas planet. It seems unlikely any Hyper-Earths would form with radii of over 4 RE, about the size of Uranus and Neptune. These giant rocky planets could be similar in mass to Saturn and Jupiter, if not more massive than the latter. Such objects would be incredibly dense and have many times the gravity of Earth. Geologic activity would be very powerful and common on such massive planets, and thick soupy atmospheres would likely form as well. But how many planets are there that would be classified as a Hyper-Earth? The truth: more than you would expect. Here are all the potential Hyper-Earth candidates known to date: THANATOS: This is @Cabbink's hellish world, which is very similar to Tartarus. It has a year of 0.52 days, orbits an F-Type star, and has a slightly cooler equilibrium temperature of 4,400*F. However, at about 2.22 RE, it might actually be a Mega-Earth instead of a Hyper-Earth. K2-77b: Another planet within the K2 data, which happens to be just 0.03 RE larger than Thanatos. It has a much safer orbit, taking about 8 days to circle a 0.76 RS high-metallicity orange dwarf. However, radial velocity measurements have shown something...odd. They heavily suggest that this planet of 2.25 RE has a mass of 604 ME, nearly TWICE that of Jupiter! And there error margins are TINY, both less than one Earth mass. This makes K2-77b the most likely and most massive Hyper-Earth candidate known. It is also the second-densest planet I will list. Put this into perspective: take every object in our solar system that isn't the Sun - all the planets, dwarf planets, asteroids, comets, dank memes, space junk, etc. - and squeeze them together into an object just over twice the radius of Earth. You will not get something as extreme as K2-77b, and that is scary. K2-92b: Similar to Tartarus, K2-92b is a world within the gaseous planet size range that is too hot to be a stable Mini-Neptune. This planet is 2.56 RE and orbits every 0.7 days around a bright F-class star, resulting in temperatures in excess of 2,675*K (around 4,355*F). While larger than Thanatos, it is likely around the lower limit for a Hyper-Earth. Recently determined to be a false positive. KEPLER-277b and c: These are a pair of large ice giant-sized planets with absolutely ridiculous masses. Both orbit what might be a G-subdwarf star every 17.32 and 33.00 days. The first, Kepler-277b, is around 88 ME and 2.9 RE, giving it a density of 19.89 g/cm3 and 10.464 gees of gravity. Its larger sister, Kepler-277c, is around 3.4 RE but is less massive at 66 ME, giving it 5.71 gees of gravity and a density of 9.26 g/cm3. With these values, it may seem like Kepler-277c might have a significant water envelope, maybe between 5 and 10% its total mass. However, both planets could be much more massive, with error margins favoring masses between that of Saturn and Jupiter. 277b and c could be as large as 239 ME and 167 ME, making them both huge terrestrial worlds. JS 183 b: An exoplanet you probably NEVER heard of. In fact, if not for the Open Exoplanet Catalog, I wouldn't either. This is near the limit of how large a Hyper-Earth can possibly get. At 3.5 RE, it's pretty close to that 4 Earth radius boundary I mentioned earlier. However, it is far more massive than Jupiter at around 531 ME, making it the second most massive planet on this list. This gives it over 43 gees of gravity and a density of 67.6 g/cm3. JS 183 b is the coldest planet on this list, orbiting near the habitable zone with an eccentric orbit (0.24) around a 0.44 solar radius, metal-rich red dwarf. K2-33b: This baby of a planet might be a Hyper-Earth, but its mass is so uncertain that I cannot tell for sure. If it is, then it's actually far past the radius limit I set at 4.9 RE. KEPLER-338b: This one is more of an honorable mention, as it is "only" 31 ME and is therefore not massive enough to be a Hyper-Earth. EPIC 22881391b: Here is the densest planet on this list. It was the recently discovered planet orbiting a red dwarf every four hours. However, things are rather odd. Based on radial velocity measurements, it appears to be somewhere around 223 ME, over TWICE that of Saturn. What makes this even more extraordinary is how this planet is only 0.87 RE, smaller than Venus. This makes EPIC 22881391b incredibly dense, at a staggering 1,884 g/cm3 with nearly THREE HUNDRED times the gravity of Earth. This would make it the densest non-stellar remnant object in the known Universe. A piece of this planet the size of a sugar cube would weight as much as a small dumbbell! Due to its hostile conditions and incredible gravity, I've nicknamed this abomination Morsaption, which comes from the Latin phrase "Mors Captionem", meaning "Death Trap". PSR J1719-1438b: One of the very few pulsar planets known is actually the FIRST Hyper-Earth candidate. This planet (which I will call J1719b for now) has around 330 times the mass of Earth and orbits a tiny, horrifying freak of nature known as a pulsar every 2 hours. It has the shortest year known, and this close proximity to such a deadly object has put significant constraints on J1719b's radius. Calculations show that it cannot be more than 4 RE, which would place it within the Hyper-Earth range. As many of you have probably heard, J1719b could very well be a Neptune-sized planet made ENTIRELY of diamonds, making it the most exciting planet on this list to visit (SPOILER ALERT: You'll still die there). However, an alternative theory has be proposed, suggesting that J1719b might be a tiny lump of quark matter around 1 km across, created in the merger of two QUARK STARS that created the pulsar PSR J1719-1438. What do you think of the possibility of Hyper-Earths? Should such a category even exist?