Just about 30 years ago, we didn’t have any scientific proof of a planet outside our solar system. Today, thanks to advances in technology and scientific research, we've discovered over 5,300 exoplanets - alien worlds out there waiting to be explored.
At first, these discoveries mainly involved large gas giants, but as our capabilities have expanded, we've started to uncover smaller, Earth-like exoplanets. Scientists have already found more than 50 exoplanets with masses similar to Earth and over 800 worlds with a radius less than one-half times that of Earth. We don’t know of many such planets orbiting in the habitable zone of their parent stars - where the conditions are just right to support life. But that's already starting to change. As our search for habitable planets continues, we're beginning to discover entire planetary systems with more than one potentially habitable world. And we already know about at least one such system in our cosmic neighborhood.
koi 5715.01
This planet is considered to be the best candidate for a super habitable world. A massive rocky world twice the size of Earth, orbiting in the habitable zone of its star. This means that the conditions are just right for liquid water to exist on the surface, a key ingredient for life as we know it.
Imagine a world so big that you could spend over 100 hours flying between continents. There would be so much more land for life to thrive on compared to here on Earth. It orbits a very special kind of star. You see, our sun is a G-type main-sequence star, sometimes referred to as a yellow dwarf, and these stars only hang around for 10 billion years. Our sun is nearly halfway through its entire life cycle, meaning in around 5 billion years, the sun will expand into a red giant star, consuming the Earth in the process.
But in the case of KOI 5715.01, a dreadful name I know, it orbits an orange dwarf star. These stars are a little smaller than our sun, but they are so much more stable. In some cases, hanging around for up to 70 billion years. Life on Earth has been evolving for just 4 billion years. Can you imagine what life might look like after 70 billion years of evolution? That's when you start getting into tier 3 civilizations and Dyson Sphere territory.
While this world does sound perfect, and I'm sure you want to move there right now, I have to be honest with you: this planet is so far away. I'm talking 3,000 light years away, meaning that if you and I wanted to leave today and head on a trip to visit this planet, and we somehow convinced NASA to lend us an Orion spacecraft, it would still take us over 100,000 years. Maybe one day we'll have a rocket quick enough to get us there in a reasonable amount of time, but for now, we can only dream about what interesting life forms might be thriving over there. Maybe we should check out something a little closer to home.
Trappist 1e
Just 39 light years away, we come across a potential safe haven for life. Seven Earth-sized worlds huddled tightly around their star, three of which orbit within the habitable zone. This is the Trappist-1 system, first discovered back in 2017, and for the last five years, astronomers have been spending every waking minute researching the system in an attempt to find life.So, they were able to detect this gold mine of planets by looking at how the star's brightness dipped ever so slightly as each planet passed between us and the star. This is known as the transit method. These planets are much older than Earth, meaning life there would have had at least 3 billion years to evolve before Earth was even finished forming.
Trappist-1e, the fourth planet from the star, is of particular interest to us. It's a little smaller than Earth, and it has the right conditions for water to exist on the planet, and we think it may have a thick oxygen atmosphere, even better for life than the atmosphere here on Earth.
But let's be clear, this system is very different from ours. The planets are orbiting a tiny red dwarf star of a similar size to Jupiter. The star is far cooler than our sun, meaning these planets have to be close, so close that the orbits of the entire system would easily fit within Mercury's orbit of the Sun. This can cause some problems.
We think that the planets are tidally locked to their star. One side is permanently cooked by the star and one side is frozen and desolate. Under perfect conditions, this could create a single strip of land around the planet where the conditions are just right for life.
But what's most exciting to me is imagining what living on these planets would actually be like. They are so close together that you would look to the sky and see these massive planets orbiting alongside you. You could take holidays to different planets as if they were countries. Visit the slopes for a skiing trip out on Trappist-1H before going for a summer holiday to the tropical world of Trappist-1d. And since it's just 39 light years away, maybe one day, this could be a reality for humanity.
Kepler-452b
Up next, we have Kepler-452b, a world that has often been called Earth 2.0. The planet shares so many similarities with Earth that it's kind of scary. It orbits a sun-like star every 384 days, that's just five percent longer than our year here on Earth. This would also make every single month exactly 32 days, which just kind of feels right...
This is a super-Earth, though, meaning it's roughly 50 percent bigger than Earth. This means more land, larger continents, and potentially more water... It's looking good so far, but it does come with a few downsides. While it is just 50% larger than Earth, it's actually five times more massive, meaning gravity will feel twice as strong on the surface, and everyone, therefore, will weigh twice as much.
But here's where things get interesting... As far as we can tell, this is the only planet in the Kepler-452 system. That means no gas giant planet, and I know what you're thinking: Jupiter protects us from asteroids here on Earth, so wouldn't this planet just be completely destroyed by asteroids? But that's where you're actually wrong. You see, we thought for decades that Jupiter was our friend, regularly protecting us from asteroid impacts. But recent simulations have come out to show that this might not actually be true. The paper showed that a solar system without Jupiter would actually have 3.5 times fewer asteroid collisions here on Earth. So, since Kepler-452b is all alone, maybe a civilization on the planet wouldn't have to worry about asteroid collisions at all.
But it is far from perfect; its star is slightly older than our own, and as sun-like stars become older, they tend to become more energetic, and as a result, the planet might be receiving too much radiation, slowly warming the planet and eventually leading to a runaway greenhouse effect. This could leave the planet looking a lot less like Earth and more like Venus, killing off all life on the planet for good.
Kepler-22b
We end our journey 600 light years away from home, in the distant constellation of Cygnus. This is Kepler-22b, one of the most interesting super-Earths ever discovered. This planet has stumped astronomers for years. It orbits well within the habitable zone, and our best observations point towards this planet is a true water world, just like Miller's planet from Interstellar. A massive ocean covers the rocky inner core, which is hundreds of kilometers deep. It is possible that life may have evolved in the depths of this ocean, strange fish that only seems real in your wildest dreams. If humans ever did make the journey across the Galaxy to visit Kepler-22b, I'm sure we would be in for a surprise.Read more about Kepler-22b-Exploring Kepler-22b: Climate, Gravity, and Characteristics.
So the real question is, which planet do you think you would want to move to? For now, I think I'll be staying here on Earth.