Since July 31, 2018, Mars has approached Earth so closely that it now appears two times brighter than Jupiter in our skies (assuming you’re reading this from Earth). To most people, Mars at night looks like a bright orange star. If you haven’t seen it yet, you should definitely check it out! Mars’s spectacular entrance this summer sparked my interest in the other planets of our universe. Of the 3775 confirmed exoplanets — planets that orbit a host star outside of our solar system — the five planets below remain so alien to us that scientist still consider them some of the most remarkable worlds ever discovered.
TrES-2b: The Dark Planet
Year of discovery: 2006
Distance from Earth: 750 light years
Distance from host sun: 3.1 million miles (5 million kilometers) — about 29.9 times closer than Earth is to the sun
Tres-2b reflects less than 1% of light from it sun, making it darker than the blackest acrylic paint imaginable. Detecting this darker-than-coal planet was no small feat; scientists describe the dip in brightness the planet caused as it passed by its sun to be the smallest change in signal ever detected (1). Imagine looking for a fruit fly to pass by an illuminated billboard. Tres-2b is about the same size as Jupiter and has a surface temperature of about 1800°F (980°C).
This planet’s extreme darkness remains a mystery for astronomers. Some theorize that the planet is so dark because it may lack reflective ammonia clouds, such as those on Jupiter, due to its extreme heat. After all, it is so close to its “sun” that a complete revolution lasts about 2.5 Earth days (that would mean a lot more birthdays and anniversaries) (2).
55 Cancri e: The Diamond Planet
Year of discovery: 2004
Distance from Earth: 40 light years
Distance from host sun: 3.5 million miles (5.6 million km) — about 26.7 times closer than Earth is to the sun
Though this planet was originally dubbed a super-earth, a planet featuring a mass much greater than yet a chemical composition similar to that of Earth, astronomers have now suspected that 55 Cancri e is likely made up primarily of carbon, iron, and silicon carbide (3). When one considers how close this planet is to its sun, the implications seem unbelievable. 55 Cancri e orbits its “sun” every 18 hours and has a surface temperature of 3,900°F (2,100°C) (4). Due to this heat, about one third of the planet’s mass could be subjected to an intense amount of pressure. That’s a ball the size of three Earth masses made completely of heated and pressurized carbon. Also known as, diamond.
The value of this planets is estimated to be around 23.9 nonillion dollars. That’s 23.9 multiplied by one followed by thirty zeros. However, sending spaceships to extract the diamond from this planet could have disastrous effects. First, our fastest spaceship may need at least 2 million years to reach the planet and return to Earth. Second, removing even a meter of the diamond from this planet would cause the value of diamond on Earth to plummet so that the jewel would become nearly worthless.
HD 189773b: The Blue Planet (with Rains of Terror)
Year of discovery: 2005
Distance from Earth: 63 light years
Distance from host sun: 2.9 million miles (4.7 million km) — about 31.8 times closer than Earth is to the sun
On Earth, we experience weather ranging from temperate climates to detrimental tornadoes and hurricanes. HD 189773b, however, features storms even meteorologists would be cautious to chase. HD 189773b receives its blue color from sunlight reflecting off of the silicon particles found in its atmosphere (5). The planet’s surface temperature is 1800°F (980°C), making it hardly a habitable place.
At a distance 31.8 times closer to its “sun” than Earth is to ours, the planet experiences winds traveling 4,000 m.p.h. (6,400 k/h) (6). That’s five times faster than the speed of sound. To make matters worse, the extreme pressure characteristic of the planet and the abundance of silicon fills the atmosphere with glass. That’s right; a storm on this planet would send raining glass flying through the air at about 1800 m/s. That’s fast enough to travel around Earth in only 6 hours.
GJ 1214b: The Waterworld
Year of discovery: 2009
Distance from Earth: 40 light years
Distance from host sun: 1.2 million miles (2 million km) — about 74.8 times closer than Earth is to the sun
This planet is classified as a super earth because it is more massive that Earth but not as large as most gas giants such as Jupiter. While it is only about two times the size of Earth, it is seven times as massive. Why? Because the planet is covered with water. While Earth’s oceans make up about 70% of its surface, water takes up only 1% of its mass. Research shows that water on GJ 1214b takes up 10% of its entire mass, suggesting that its oceans are 10 times deeper than ours. One can only imagine the extraordinary beings that may be living in those oceans if ours can host incredible deep sea creatures such as mantis shrimp, goblin sharks, and basket stars.
GJ 1214b orbits its star every 38 hours (that is, every “year” on this planet last about only 1.5 Earth days!) Due to its close sun proximity, this planet experiences temperatures from 360 to 560°F (180 to 280°C) (7). Scientists predict that under these conditions, the water may be found in states very different from the solid, liquid and gas water we see on Earth, such as steam, superliquid, and plasma. The water towards the planet’s core would be under so much pressure that it would form into ice. Unlike the ice we know on Earth that forms at 0°C, this ice is called Ice 7.
HD 188753 Ab: The Trisolar Planet
Year of discovery: 2005
Distance from Earth: 151 light years
Distance from host sun: 5 million miles (8 million km) — about 18.7 times closer than Earth is to the sun
If you were to stand on the surface of this planet, you would find that you have not one shadow but three. This planet revolves around its “sun” every 3.3 days along with two other “suns” revolving around each other (8). Scientists refer to HD 188753 Ab as a “hot Jupiter” because it is a gas giant much closer to its host sun than Jupiter is (perhaps trying to stand on this planet would not be the best idea).
As spectacular as the triple sunsets on this planet would be, the planet’s existence itself is especially remarkable. The triple star complex makes the host solar system very crowded and hot, and since planets rarely form under these harsh conditions, HD 188753 Ab’s formation is a mystery. Since its discovery, only four other planets have been found in a triple star system (9). HD 188753 Ab’s existence suggests that planets may be more robust than we thought.