Do Aliens Exist?

Talk of extraterrestrial life—or life originating off of our planet—made science headlines twice in the past week. I’m not talking about claims of UFO sightings or the latest alien abduction story. The news items I’m talking about offer examples of millions of dollars being spent on the human urge to search the vastness of space to find more of ourselves out there.

First, the Russian millionaire Yuri Milner recently pledged $100 million dollars toward the search for ET over the next decade. The funds will go toward developing new technologies, recruiting new students, and more guaranteed telescope time, all of which will make the search for life larger, faster, and more efficient.

Then, just a few days after this game-changing announcement, NASA’s Kepler mission released the news of the most Earth-like planet to be discovered so far. At 1,400 light years away, the planet, called Kepler 452b, is 1.6 times the size of the Earth and orbits its sun at a similar rate, making its year 385 days.

Together these announcements mark a potential turning point in the search for other forms of life in space. We now have the resources to look for it, and we’re figuring out where to look.

Are We Alone?

Whether or not the search for life will be successful depends on what you would call “life.” Studies of extrasolar planets (planets outside of our solar system, also called exoplanets for short) have started by looking for planets with the key ingredients for life rather than for life itself.

One key ingredient for life as we know it is water. Planet hunters can predict the temperature on the surface of an exoplanet based on how far the planet is from its star (and what kind of star it orbits). Every star has a “habitable zone,” also called the “goldilocks zone” where the temperature is just right for water to be a liquid—not too hot (i.e., too close to the star) and not too cold (i.e., too far from the star). When an exoplanet falls in its stars habitable zone, it could potentially host liquid water.

According to the NASA Exoplanet Archive, a total of 1,879 exoplanets have been discovered as of July 2015. Considering the first exoplanet was only discovered in 1992, that’s over 80 entire new worlds discovered each year.

However, early on the search techniques favored the discovery of planets that were much more massive than the Earth and in orbits that were much closer to their stars. These exoplanets are called “Hot Jupiters” because they are closer to the mass of Jupiter than to that of the Earth. The dominance of the more massive planets in the current exoplanet count is what makes NASA’s recent discovery of Kepler 452b so compelling. By comparison, Kepler 452b is so similar to Earth that scientists are calling it Earth’s bigger, older cousin. (It’s star is roughly 1.5 billion years older than our Sun.)

Of course, in order to get a better estimate of an exoplanet’s temperature, we also have to know something about its atmosphere. Remember that Mercury, the closest planet to our Sun, is a blistering 426 degrees Celsius (about 800 degrees Fahrenheit), but it is still not the hottest planet in our solar system. That honor goes to Venus at a sweltering 462 degrees Celsius (864 degrees Fahrenheit). Even though Venus is further from the Sun, its atmosphere acts as a blanket that traps heat and warms the surface.

Planetary atmospheres thus offer clues as to whether or not a planet can host life via their effect on the planet’s temperature but also through their chemical composition. Scientists are just now starting to infer the properties of atmospheres around exoplanets. One of those atmospheres may contain oxygen, a strong indication that the planet could harbor life.

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The Search for Intelligent Life

Besides the huge progress made over the last two decades in the search for habitable planets, the search for intelligent life is a much more difficult task. First off, the distances to other worlds are prohibitive. Humans have never traveled farther than the Moon! Even our space probes are lost once they leave the outer reaches of our solar system, and the nearest star is a whopping four light years further away. Second, even if we did have the resources to reach out to a particular star, in hopes that it hosts a life-bearing planet, which star would we pick? Our Milky Way galaxy is home to at least 100 billion stars!

Luckily there is a way to communicate across the vastness of space without the need for a human space traveler or even a probe: radio waves. A dead giveaway that there is intelligent life here on Earth (at least from an outsider’s perspective) are the nonstop radio emissions we send out into space for everything from air traffic control to satellite communications.

Now these radio emissions aren’t sent so they will be detected by aliens in the far reaches of our galaxy so someone would have to be listening really hard to find them. We did, however, once use the large Arecibo radio dish nestled in the Puerto Rican jungle to send out an encoded message explaining what life is like on Earth for anyone who might be listening. You can have a look at the message and see if you can decode what each line is meant to represent! So far, no one has returned our call.

The goal of programs like the Search for Extraterrestrial Life (SETI) and Yuri Milner’s Breakthrough Listen Initiative is to search for other solar systems for planets emitting such signals. As outlined by the astronomer Frank Drake in his famous Drake Equation, the chances of detecting such a foreign signal depend on a lot of poorly constrained factors. How many stars do we have the resources to spend time observing? How many of those could have habitable planets? How many of those planets have been around long enough and have the unique conditions necessary to develop intelligent life? How many of those civilizations use radio waves to communicate and have sent out a signal for us to detect?

The task seems daunting, but the reward is so huge and potentially life-changing for all of us Earthlings, that many see it as worth the effort.

How Can You Help?

Searching a range of radio frequencies for signals amongst the Milky Way’s 100-200 billion stars is sometimes referred to as looking for a signal in the “cosmic haystack.” With the new funds provided by Milner, both SETI and Breakthrough Listen will be able to drastically increase the size and scope of their searches. This effort will result in, as you may have guessed, an enormous amount of data. Thus, both are looking to citizen scientists (that’s you!) to get things done.

Three million users already participate in the SETI@home project which works as a screensaver that processes SETI data when your computer would otherwise be idle. The Breakthrough Listen Initiative plans to use open source software called BOINC to do a similar task. BOINC is already tackling many different scientific problems from climate change to pulsar searches by using your smartphone or tablet to process data. The app only runs while your device is plugged in and fully charged so it doesn’t run down your battery, and it does not contribute to your data rate.

There are a lot of factors working against the search for extraterrestrial life, most significantly large interstellar distances. But getting involved in the search takes minimal effort, and what if your phone finds the first ever message from ET?

 “This is the biggest question. We should be listening.” – Yuri Milner

Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.

Planet image courtesy of nasa.gov and Shutterstock.