NASA's Kepler Mission Discovers Tiny Planet System

So, this right here is a planet in a system known as Kepler 138. It's a very interesting planet because we haven't really discovered any other similar to it. Now, in this particular system we actually have two planets that seem to actually meet this specification and what really makes it unique is that it is a gas planet. But it's a gas dwarf. In other words, it's a planet that's very similar in size to Earth. But in terms of the actual mass it's much lower than Earth and so it creates this very interesting envelope of gas around it.

Now, let's actually investigate it in a little bit more detail in Universe Sandbox first before we land on this planet and take a look at what the surface looks like. So, the actual system looks like similar to this. Here is Kepler 138, a relatively average red dwarf and it has three planets around it we discovered back in 2014. But since then we actually reclassified them several times because for the most part we don't really know much else about it other than what we've seen from the Kepler Mission. So, if I was to enable habitable zones here you will see that none of these planets are actually in the habitable zone. As a matter of fact, they are all very close to the star meaning that they're all going to be really hot.

So, we don't really expect them to be in any way friendly to human life. The planet that's here in the above picture right in the middle known as KOI 314 B. KOI stands for Kepler Object of Interest is more massive than Earth. As a matter of fact, it's almost double the size or the mass of Earth and it's about may be 1.2 sizes of Earth. So, it is quite comparable in size to our own planets. So, this is kind of what earth would look like if I was to position it right next to this planet. It's relatively similar in size. But more massive! Now, this particular planet is not really that interesting. Though we've seen quite a lot of these and so this is not why we're here. We're here for the other two planets and the other two planets seem to be very different.

So, first of all let's take a look at the farther one. In this case it is known as KOI 314 C. This planet is also relatively large in terms of the actual size. So, it's about the same size or similar in size to the previous planet. But its mass is much lower. Its mass is about 64% the mass of Earth and because of this its density is also much lower as well. Its density is about 2.5 times lower than density on the planet Earth and so it actually would look more like the picture shown above. Basically, mostly atmosphere. Not so much actual solid surface. The most recent analysis of this planet from 2018 actually puts the density even lower at something like 1.36 with the actual mass and the actual radius a little bit different as well.

So, it might actually be as massive as 1.17 masses of Earth with the radius being about 1.7 masses of Earth. So, it could be a lot more massive! But the reason why it's so large is really the actual unusual atmospheric layer that is probably present here. So, in other words this planet probably has a tremendously large atmosphere. So we are going to try to see if we can add a huge layer of atmosphere here just so that we can actually see it. Although, it looks like the planet really heats up pretty quickly as soon as I start doing that and that's due to the actual effects of greenhouse gas. So, the greenhouse gas is here which are probably quite abundant on this planet. Especially, if it's mostly water would mean that this planet is a lot hotter than even the hardest planet in our solar system which is Venus.

So, we don't really know if it looks like this. But it's quite possible that the temperatures here might be close to 500 - 600 degree Celsius which makes it definitely not habitable at all. But nevertheless though this is actually still not really the planet we came here for because we really wanted to show you these smallest gas dwarf we discovered so far and that's the first planet in the solar system from the star Kepler 138 B. Now, it is actually interesting because the name Kepler 138 B used to be applied to the other planet in this system. Now, here's why this is interesting! First of all let me actually take Mars and place it right next to it. It's even smaller in size than Mars and in comparison to Earth it's super tiny and so the actual mass of this planet is currently around 5.4 masses of the moon or basically about 6.6% the mass of Earth. Its radius though is a little bit larger which means that its density is about 2 to may be 3 times smaller than density of Earth.

This implies to us simply because of the size itself that this planet is definitely filled with a very large layer of atmosphere very similar to what you saw in the Space Engine right here as shown in the picture above. So, this is kind of what this planet actually looks like and what's really interesting about it is that it's relatively tiny in size. A lot smaller than Earth, possibly even smaller at least the extra-terrestrial part than Mars and basically even less massive than Mars as well. It basically has a very thick layer of atmosphere that we're going to go into land on right now that is extremely unusual and definitely not something that we've seen anywhere else in our own galaxy.

We definitely don't have anything comparable in our own solar system and so here this huge layer of atmosphere is most likely created by nothing but water vapour. It's very unlikely that this is similar to other gas giants for example so it's definitely not helium, it's definitely not hydrogen because those gases would escape very quickly from this planet simply because it has very low gravitational attraction. But having water vapour is very possible. So, all of this huge thick atmosphere in the above picture is basically water vapour. Now, one thing what we know about water vapour is that it is a very excellent greenhouse gas and that also implies that if all of this is water vapour; the actual temperature of the planet is going to be ridiculously high even higher than Venus.

So, here if we go into the planetary temperature and we give it a relatively thick atmosphere. Let's say possibly something closer to Venus or may be a little bit more than Venus you'll see that first of all almost instantly everything starts to evaporate. Now, this obviously implies that this planet is probably losing a lot of mass and a lot of it is basically being evaporated into the outer star system. But at the same time this also might mean that this planet used to be much bigger in mass and in size millions of years ago.

So, in other words in one of the main reasons why this planet is so poofy and basically is essentially a gas dwarf is because of the influence of the star on this planet. So, because of the proximity to the star and also because of the tremendous amount of water vapour in the atmosphere this planet is really hot. This in effect creates a very large atmosphere around it which then evaporates into the outer solar system. So, all we know this also means that this planet might actually one day become really tiny and possibly kind of reach a balance where it doesn't actually decrease in size anymore but it's going to be increase more and possibly look a lot more like for example Mercury.

Now, does this mean that mercury may have been similar to this in the past? Well, actually yes! It very likely was and it's possible that Mercury might even had atmosphere and could have been very similar to this planet as well. So, it could have been some sort of a gas dwarf in the past. So, are we looking at something that was the history of Mercury? Well, it's very possible! But obviously it's just a speculation and unfortunately we don't really have any proof to actually say so just yet because we haven't really landed on Mercury to investigate its surface. But if one day we'll go on to Mercury and land in there and basically discover that somewhere on the surface we actually have all deposits of what may have been atmospheric water. In that case, it means that this right here could have been what Mercury looked like in the past.

Now it's possible that we might discover more of these gas dwarfs in the future. But for now unfortunately, we mean this is actually the only one we found that seems to be not just really tiny. But also very unusual both in its composition, in its parameters and most importantly in its actual size. Anyway, that's all I wanted to discuss in this article and hopefully now we know a little bit more about the system known as Kepler 138 and most importantly about its unusual gas dwarf Kepler 138 B. Now the other object Kepler 130 D is also kind of interesting. But we've actually seen quite a lot of similar objects. So, it's not as unique! But this object that's really small and has a tremendously thick atmosphere is definitely something that we haven't really found anywhere else.

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