“It suddenly struck me that that tiny pea, pretty and blue, was the Earth. I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn’t feel like a giant. I felt very, very small.” -Neil Armstrong
Here on our little wet rock in our Solar System, we often remind ourselves what a small world Earth actually is. The farther out in space we reach, the more this appears to be true.
The Earth is the largest of the four inner, rocky planets in our Solar System, at more than 12,000 km in diameter. But even at this size, Earth is dwarfed by all four of the gas giant planets, which range in size from Neptune (at nearly 4 times the size and 17 times the mass of Earth) all the way up to our Solar System’s giant, Jupiter, with more than 11 times the Earth’s diameter and over 300 times its mass.
We used to think that this had some type of special meaning: that the Solar System had four small, inner rocky planets and four large, outer gas giant planets. But this is not the case at all. We’ve since discovered that not only do most of the stars in the sky have planets, but there is a huge diversity as to how large and where various planets are located.
So far, most of the worlds we’ve found are very close in proximity to their star, and we’ve found more large worlds than small ones, but that’s because the large, close planets are the easiest types to find.
There are around 2,300 known exoplanets (or extra-solar planets) at present, including cases where gas giants are in the inner solar system, cases where the inner, rocky world is so close to its parent star that it is literally boiling away, cases where gas giants and rocky worlds cohabitate in the inner solar system, and, of great interest to us, systems where rocky worlds exist in their star’s habitable zone.
The diversity of what’s out there is simply astounding, and leads one to believe that if you simply look at enough stars in the galaxy, you’re bound to find any gravitationally stable configuration of planets that you can imagine.
Well, we’ve been looking at what’s out there, and around a nondescript star in a very average region of the sky, something truly remarkable has been found.
The southern skies offer this breathtaking view of the Milky Way, with the Southern Cross and Pointer Stars visible in the upper left-hand corner of the above image. But a little bit closer to the galaxy’s center in that region of the sky is a star you’d never see with your naked eye, and even if you could, you’d never think twice about it.
But about 53 light years away lives a dim, reddish-orange star that’s smaller and less massive than ours, at maybe just 70% the mass and only 8% the brightness of our Sun. It’s just barely visible with a small telescope, but a larger, higher-magnification telescope can lead an astute observer to find this star.
Originally known as HIP 85647 (as it had its parallax measured by the Hipparcos satellite), this is actually a binary star system with two M-class stars. The larger, brighter one is perhaps now better known as Gliese 676, or GJ 676 A, depending on who you ask.
A very large gas giant planet was found around this Solar System in 2009, one about five times as massive as Jupiter, known as a super-Jovian planet.
But a very recent paper by Guillem Anglada-Escudé and Mikko Tuomi ought to be generating a lot of attention, because we now know that just 53 light years away is a solar system with four planets: two inner, rocky worlds (e and d) and two outer, gas giant worlds (b and c).
This, on its own, isn’t ground-breaking. After all, there are other known systems (including one very close one) where there’s an inner, rocky world and outer gas giants.
It’s beautiful, but it’s not unique.
No, what’s truly amazing about the planets orbiting GJ 676 A are that they’re all huge! The two inner, rocky worlds? Giant, at over four and eleven times the mass of Earth, respectively. And the two outer, gas giants? Tremendous, at least five and three times the mass of Jupiter.
In other words, despite the star itself being significantly smaller, less massive and less luminous than our Sun is, all of the planets are much bigger, more massive and — for some reason — more eccentric in their elliptical orbits than the planets in our Solar System.
The second Super-Earth, the very massive one, is suspected to be only slightly too close to its parent star to be in the suspected habitable zone; there is a chance that there may be life on it.
So if there is life in this planetary system, what would it look like compared to the life we’re familiar with? Would it be similar? Or, like the worlds in its solar system, would it be… super-sized?
Whatever the case, whether there’s life or not, there’s a very good chance that practically every point of starlight you see in the sky has its own slew of worlds orbiting it, waiting to be discovered. Some are similar to the ones in our Solar System, while others are more diverse than we can even imagine at this point.
I can’t wait to see what else we learn about them.