"Worlds Without Number" - Exoplanets and LDS Beliefs

In Moses, we read that God has created "worlds without number" (Moses 1:30) and it is strongly implied that many of these worlds have inhabitants on them that are similar to us.

In my last entry I wrote about finding and characterizing Earth-like planets, and I just glossed over the fact that we actually have discovered thousands of potential planets around other stars, known as extrasolar planets or exoplanets. This is one example where science has corroborated revelations given nearly two centuries ago, in that we think the number of worlds or planets in our galaxy like numbers in the 100's of billions - certainly enough to qualify as "worlds without number."

Diagram for the radial velocity method to detect exoplanets.

First, a little bit of background on exoplanets and how they're discovered. The first exoplanet around a star like the Sun was discovered in 1995. The way it was discovered was by looking at the slight change in the star's position from the planet. You see, we think of planet's orbiting around stars and the stars staying put, but in reality the star "orbits" around the planet too - it just moves far less than the planet does. So as the planet moves around the star, the star moves in response. When the star's position changes, it's velocity or speed towards us will change, and then we can take advantage of a physical effect known as the Doppler Effect. Everyone knows what this is even if they don't know the term - you know when a fire truck or ambulance is coming towards you and you can hear the pitch of the siren change as it passes you? That's the Doppler Effect, only instead of talking about the pitch (or frequency of the sound) change, we're talking about the frequency (or color) of light changing. So as the star moves in it's "orbit," we see it's color change a very minuscule amount, and from that we can infer that there must be a planet orbiting the star.

How transit work - we see a dip in the star's
brightness and infer a planet must be there.

The other main method of detecting a planet is called the transit method. This is one is thankfully much more intuitive. For certain planet-star systems, the orientation is just right that we can actually see the planet pass in front of the star, like in an eclipse. Planets are much, much fainter than stars so when the planet is in front of the star, we see a decrease in the amount of light from the planet, and based on the amount that the light decreases by we can not only tell that there's a planet, but also how big the planet is relative to the star. You might have read news articles about planets being discovered by a mission called Kepler. The Kepler spacecraft stared at one spot in the sky for more than 3 years looking for transiting planets, and it found thousands of them. It's made the transit method the most successful method for finding planets to date.

So now that the background is out of the way, what do the results mean? Well, first off, we've found a lot of planets. You can check this site to get an up to date count, but as of right now we're at over 1,000 confirmed planets and over 3,600 planet candidates (likely to be planets, but need follow-up observation). Based on the statistics from missions like Kepler, there should be billions of planets in our galaxy alone, and in the universe, probably trillions.

But I think the most interesting part about all these discoveries is that God thew a bunch of things at us that we never expected. A lot of people more or less assumed that exoplanet solar systems would be a lot like our own solar system - rocky planets in the inner part, gas giant planets in the outer part, all with nice and neat circular orbits. But that's not what we've seen at all. We've found that about 1% of stars have what are called Hot Jupiter planets, planets that are the size of Jupiter but found 10 times closer to their star than Mercury is to our Sun. There have been planets found with highly elliptical (non-circular) orbits, and also planets in multi-planet systems where the inclinations are completely misaligned - meaning that instead of the orbits lying on a flat surface, they criss-cross each other. There are a lot of planets that have sizes between Earth-sized and Neptune-sized, things that we really don't know anything about because we don't have anything like that in the solar system. It really seems like God has created every single planet he possibly could in this wondrous universe.

It's tempting for me to think that our solar system is unique and that it's not possible to have life on a planet without having the exact right setup, but I'm sure I would be proven wrong eventually. The neat thing about these planets is that they're all, in some way or another, created to bring to pass the work of Heavenly Father - the immortality and eternal life of His children, which includes us! Even in our own solar system we have 7 other planets, countless moons and dwarf planets and a large number of asteroids and other small objects, and it's all for us. How amazing is that? And more so, how humbling is that?

So in conclusion, in exoplanets, as well as in our own lives, God helps us to remember that He knows far more than we do. He is constantly surprising us and throwing new concepts and challenges at us. There are indeed "worlds without numbers" out there, in all shapes and sizes and there will be things we never expected to see, but God knows all His creations, and He has created them for own purpose - to save His children.