Super-Earths

Introduction

We love our planet (disregarding the amount of harm we do/did to it). Without it, our existence, as it is now, would probably not be possible (disregarding parallel universes/dimensions). However, due to the impending armageddon known as a supernova (specifically, the death of our sun) we have been trying to find an alternative habitat. Mars and some of our neighbors seem to be possible options, but their atmospheres along with many other factors make our faces cringe about the idea. So what if there were...other Earths?! Can this be our solution? In this lesson, we will be discussing the idea of what a Super-Earth is along with determining whether or not they can be the solution to one of humanity's greatest problems (literally #firstworldproblems).

Now before we continue, I'm going to ask that you clear your mind and get rid of all opinions or biases about whether or not Super-Earths may be the solution. I'm only asking that you do this since this topic does require us to step back and not to be so hasty in considering what the right answer may be. Furthermore, I will preseent to you this disclaimer: This lesson will not necessarily give the "right answer", instead it will provide some food for thought on what to consider.

Don't judge a book by its cover! (What is a Super-Earth?)

Super-Earths, contrary to what you may have assumed when you first heard the name, is any planetary body that has a mass within the range of 1 - 10 times the Earth's mass. This can imply to mean that we don't have to consider whether or not the planetary body has proper temperatures, compositions, orbital properties, habitability, or environments that suit living organisms. So our first question arises:

However, we shouldn't give up yet! Let's discuss the characteristics of Super-Earths!

What are the Characteristics of Super-Earths?

We won't hit all the details in this lecture, however we will consider some of the "highelights" of features to consider.

Classification of Density and Composition

We know that Super-Earths usually have a far greater mass than our own Earth. Thus, their physical characteristics may differ from Earth's. Scientists have developed theoretical models for Super-Earths and have provided three potential main compositions with correlation to their density:

1.) Low density: These are inferred to be composed mainly of hydrogen and helium.

2.) Intermediate density: These are inferred to either have water as a major constituent, or have a denser core covered with a gaseous envelope.

3.) High density: These are inferred to be rocky and/or metallic, like Earth and the other terrestrial planets of the Solar System.

Plate Tectonics?!

Scientists suggest that Super-Earths would be more geologically active than Earth, with more active plate tectonics due to thinner plates which are placed under more stress.

Fun Fact: Scientists theorize that Earth is a borderline case, and is just barely large enough to sustain the stress of plate tectonics!

Temperature

Unfortunately we don't know enough about the atmosphere of super-Earths, thus the surface temperatures are currently unknown (However, we do make genearl approximations based off of our own Earth).

Habitability (dun! dun! dun!)

The good news is that most theorists in the field believe that Super-Earths are actually more habitable than our own Earth! The higher surface gravity (due to the planet being larger) implies a thicker atmosphere, increased surface erosion and therefore a flatter topography. The idea is that this will result into a planet filled with oceans that have island chains which are ideal for biodiversity. Even the larger extreme of Super-Earths may have ideal conditions, as the larger size implies that the planets also retain more heat within its interior much longer, along with sustaining plate tectonics (which is necessary for regulating the carbon cycle which is correlated with the climate) for longer. Furthermore, the thicker atmosphere and (probably) stronger magnetic field would also shield organisms against harmful cosmic rays.

However, this is enough talk about the theoretical parts of our discussion. Let's look at what scientists have actually found!

Empirical Evidence (Discoveries)

The Absolute First

The first super-Earths were discovered by Aleksander Wolszczan and Dale Frail around the pulsar PSR B1257+12 in 1992. The Super-Earths had masses which were approximately four times that of Earth.

The First Habitable

In April 2007, a team headed by Stéphane Udry in Switzerland announced the discovery of two new super-Earths around Gliese 581, both on the edge of the habitable zone around the star where liquid water may be possible on the surface. With Gliese 581 having a mass of at least 5 Earth masses and a distance from Gliese 581 of 0.073 astronomical units (AU; 6.8 million mi, 11 million km), it is on the "warm" edge of the habitable zone.

(Very) Recent Discoveries

While I would love to get into the full history of the discoveries that have been made in the past decade or so, I think it is best that we focus on what we have been able to do very recently (within 2015) as the problem we face is that which is in the future, not the past.

On Janurary 6th, 2015, NASA announced the 1000th confirmed exoplanet discovered by the Kepler Space Telescope. One of the sets of discoveries made to reach that 1000th mark was the Kepler-440b, which is a Super-Earth that is within the habitable region of its star.

Much more recently on July 30th 2015, Scientists discovered a planetary system with three super-Earths orbiting a dwarf star. The four-planet system which was given the name HD 219134, was found to be 21 light years from Earth within the northern hemisphere of constellation Cassiopeia. Unfortunately, we deemed it to be inhabitable. The planet with the shortest orbit is HD 219134 b, and it is Earth's closest known rocky, and transiting, exoplanet.

Concluding Remarks

We have discussed the idea of Super-Earths in relevance to one of humanity's greatest problems: How can we avoid the end of human life (by a supernova)? We have several options to consider, and perhaps Super-Earths are the best way to go...or maybe not? Now that you know at least the basics, along with what we have discovered, you decide! Are the supposedly-habitable Super-Earths the way to go? Or are they just not as viable an option compared to other planets in our solar system? Post your answer and/or explanation in the comments! Thank you, I hope you enjoyed the lesson and keep exploring!