Venus is often referred to as Earth’s “sister planet.”
After all, they orbit the same sun. Venus is just a bit smaller than Earth. And the two are only about 26 million miles away from each other – veritable next-door neighbors in the cosmos.
But other than size and proximity, the two planets have little in common. The surface temperature on Venus is nearly 900 degrees Fahrenheit. (And you thought Florida was hot in the summer.) The atmosphere is almost entirely made of carbon dioxide. In short, astronomers are fairly certain life doesn’t exist on Venus.
So, other than perhaps the courtesy title of “sister,” you can cross Venus off the sibling list. In fact, the closest thing Earth may have to a solar system sibling would have to be Mars. While there is still no proof, some scientists believe it’s possible there is some form of life on the Red Planet, although it would almost certainly be microbial – bacteria and viruses than we would refer to on Earth as germs.
But astronomers have not given up hope that life – perhaps closer to what we have come to know on Earth — might exist on another planet outside of our solar system. In fact, NASA is taking steps to try to answer that age-old question with its Kepler mission. The Kepler spacecraft is in orbit around the sun, currently about 40 million miles away from Earth. From the spacecraft, the brightness of about 145,000 stars in a swath of the Milky Way Galaxy is being monitored. A very slight reduction in the brightness of an individual star is an indication that a planet might be orbiting around it.
Kepler-22b, the first confirmed planet outside our solar system to be orbiting its sun at a distance hospitable to life, is shown here in an artist’s rendering of what it might look like. It is located 600 light years away and its radius is about 2.4 times that of Earth.
Image credit: NASA/Ames/JPL-Caltech
Through the Kepler findings, astronomers are able to take a closer look at those “potential planets” to determine if they actually exist, and if so, how far they are away from their sun, according to Elliott Horch, associate professor of physics at Southern. Ground-based telescopes and equipment are used for this purpose. (One of the Earth-based devices used to prove or disprove the existence of a planet was actually developed by Horch with funding from the National Science Foundation.)
A “sweet spot” distance between a planet and its sun would increase the chances of the surface temperature on that planet being hospitable to life. That distance – known scientifically as a “habitable zone”– varies based on multiple factors, but a requirement is that water can exist as a liquid on that planet. The Earth is an average of about 93 million miles away from the sun.
Horch says the Kepler mission is already producing fascinating results. “It really is a remarkable project – one that may help us one day answer the age-old question, ‘Are we alone?’”
He points to several Kepler accomplishments:
- A total of 105 planets have been found so far that are within the potential “life zone” distance from their sun. That number is expected to rise significantly in the months and years ahead. The first of these 105 “confirmed planets” orbiting in this habitable zone is known as Kepler-22b, located about 600 light years from the Earth.
- About 2,700 stars are being closely studied as possibly having planets that could sustain life.
- Based on results from the project so far, experts estimate that about 16 percent of stars similar to our sun have a planet similar in size to the Earth orbiting it.
So what? Just because a planet orbits a star within a certain range doesn’t prove that life exists on it, let alone any form of intelligent life, right?
That’s correct. But as Horch points out, it’s a significant step toward finding out. He notes that astronomers could then hone in more closely on those potential “Earth-like planets” to determine if life is likely, such as by conducting more research on the average density of those planets.
“After that, things gets much more difficult,” Horch acknowledges. “But perhaps a next-generation satellite or satellite array could determine a planet’s bulk atmospheric properties or even take an image of the planet.”
And those actions would move us closer, by far, in determining whether or not we are alone in the universe.
Do you think life exists on other planets? And if so, is there intelligent life out there?