For all of human history, we have thought we were alone in the universe; that the Earth was the center of everything, and that our solar system was the edge of all existence. But recent discoveries suggest that this view may be changing as we expand our knowledge beyond the edge of our solar system and into what’s known as exoplanets, or planets that orbit stars other than our own sun. In this article, you will discover what scientists have learned about these exoplanets – and what they still don’t know about them.
Where did it all begin?
We know that around 13.7 billion years ago all matter in existence was condensed into a single point, and then for some reason – perhaps to relieve a huge cosmic itch – began exploding outwards in what is known as The Big Bang. Since then we’ve been on an almost 14-billion-year long cosmic journey with nothing but dark space as our companion. But could there be something else out there? Could intelligent alien life exist somewhere past our universe’s vast expanse? And if so, how would they even begin trying to communicate with us? These are just a few of the questions being asked by scientists at Breakthrough Listen, an initiative launched by Russian entrepreneur Yuri Milner which aims to search for signs of intelligent extraterrestrial life using powerful telescopes trained on our galaxy and neighboring stars. So far it has spent $100 million on its quest, but it hasn’t found any evidence that aliens exist…yet. However, researchers have discovered thousands of planets orbiting distant stars outside our solar system, many of which may contain conditions suitable for supporting life. In fact, scientists have calculated that one in five sunlike stars should have an Earth-sized planet within their habitable zone (the distance from a star where liquid water can exist on a planet’s surface), suggesting that billions of Earth-like worlds may exist in our galaxy alone!
How can we look back in time so far?
It’s all about speed. The fastest objects in our solar system are interstellar particles, which reach speeds up to 1000 km/s when they interact with magnetic fields. Travelling at such speeds means that, given enough time, they could travel a distance equal to three times our solar system -or more. Unfortunately, it would take longer than 13.8 billion years for them to reach Alpha Centauri -the nearest star beyond our own sun- travelling at these incredible speeds. So how can we look back into space so far? We need to use light itself as an instrument. This is possible because of something called redshift; an effect where electromagnetic radiation (such as visible light) appears redder if it is moving away from us and bluer if it is moving towards us. If a galaxy is receding from us, its emitted light will appear shifted towards longer wavelengths and be invisible to us on Earth due to its long wavelength; but using instruments like telescopes or satellites we can detect its presence by looking for shifts in infrared or ultraviolet frequencies instead. By detecting these ‘shifted’ light waves, astronomers can determine how fast galaxies are moving away from us and measure their distances. In fact, in order to measure distances across space accurately, astronomers have developed another method known as ‘standard candles’. Standard candles are used to calibrate distances between objects within a certain class of astronomical object. One example of a standard candle is Cepheid variables: stars whose luminosity fluctuates periodically over time periods ranging from days to months.
Where can we look for evidence?
To investigate whether any other stars (or even other civilisations) are out there, scientists look for telltale signs of alien life in deep space. Just like police detectives examine clues on Earth to track down criminals, astronomers search distant solar systems for evidence that extraterrestrials may have been – or still may be – hanging out. But just how would we know if they were there? And how do we find it? In short: by looking at what is known as exoplanets. A planet beyond our solar system is called an exoplanet because it orbits a star outside our own sun, but these planets can also be called extrasolar or exoplanetary planets as well. The first exoplanets discovered were huge Jupiter-like gas giants orbiting their parent stars far too closely to support life. The hunt was then on for smaller, rocky worlds similar to Earth and its neighbour Mars. Since 1995, when Swiss astronomers Michel Mayor and Didier Queloz found the first bona fide exoplanet orbiting a sun-like star, more than 2,000 others have been discovered. Today, astronomers estimate that at least 100 billion planets exist in our galaxy alone, with many billions more in other galaxies. That’s a lot of real estate to cover! Scientists have identified two main methods for finding exoplanets: direct imaging and indirect detection.
Are we alone in the universe?
Since our planet is spinning around a star, much like other stars are doing in a galaxy, and since many galaxies exist in space, it’s possible that somewhere out there, intelligent life exists on an unknown planet. However, we have no way to contact these faraway civilizations; furthermore, we don’t know if they have been destroyed by some natural disaster or a supervirus. In short: We simply don’t know whether life exists beyond our Solar System. But here’s why you should be hopeful about alien life! One reason why you might be hopeful about alien life comes from exoplanet research. Exoplanets are planets outside our Solar System (that means they revolve around a different sun than ours). NASA has discovered more than 3,500 exoplanets so far—many with similar characteristics as Earth. That could mean extraterrestrial beings could live there too! The second reason you might be hopeful about alien life is because of how long stars last. Stars can burn for billions of years, which gives plenty of time for intelligent species to develop. It also gives them plenty of time to evolve into something else entirely (if they aren’t wiped out by a supernova explosion first!). The third reason you should be hopeful about alien life comes from astrobiology research. Astrobiologists study what conditions must exist for living things to grow and thrive in outer space.
