Astronomer Stephen Kane from the San Francisco State University is scrutinizing planets that exist outside our solar system to answer a question that has been asked by physicists, biologists, philosophers and filmmakers – Is there anybody out there?
Kane is one of the world’s leading planet hunters and he focuses on finding habitable zones. These are areas where water could exist in a liquid state on a planet’s surface, providing there is enough atmospheric pressure. Kane’s team includes Miranda Waters, a former undergraduate student. They have been examining the habitable zone on a planetary system some 14 light years away from Earth. Their paper titled “Characterization of the Wolf 1061 Planetary System” will be published in the next issue of Astrophysical Journal.
Kane explained that the Wolf 1061 system is important because it is close to us, which gives them the chance to do follow up studies to see if there is indeed life somewhere in the system. Wolf 1061’s proximity to Earth is not the only reason why it is an attractive subject for Kane’s team. Wolf 1061c is completely within the habitable zone. This rocky planet is one of the three known planets in the system. With help from collaborators in Geneva, Switzerland and at Tennessee State University, they have been able to measure the star around which the planet orbits. This has given them a clearer picture of whether life could exist there or not.
Kane noted that when astronomers search for planets that might be able to sustain life, they are essentially looking for a planet that has close to identical properties to Earth. The planet would have to exist in a sweet spot often referred to as the “Goldilocks zone”. Conditions are just right for life this zone. The planet must be exactly the right distance from its parent star – not too far, but also not too close. A planet that is too close to its star would be too hot. Conversely, if it is too far away, it may be too cold and any water would freeze. Kane added that this is what happens on Mars.
On the other hand, when planets warm, a runaway greenhouse effect can arise where heat is trapped in the atmosphere. It is widely believed that this is what happened on Venus, Earth’s twin. According to NASA, Venus once had oceans, but all the water evaporated because of its heat due to its proximity to the sun. Since water vapor is very effective in trapping heat, it increased the temperature on the surface of the planet even further. The surface temperature on Venus now rises up to an amazing 880 degrees Fahrenheit.
As Wolf 1061c is close to the inner edge of the habitable zone (closer to the star), it is possible that it has an atmosphere that is similar to Venus. Kane notes that it is close enough to the star to make it look suspiciously like a runaway greenhouse.
Kane and his team also observed that Wolf 1061c’s orbit changes at a much faster rate than Earth. Our home planet experiences climatic changes, such as an ice age, due to the slow variations in its orbit around the sun. This could mean that Wolf 1061c’s climate could be quite chaotic. Kane speculates that it could cause the frequency of the planet heating up or freezing over to be quite severe.
These findings do not fully prove whether life is possible on Wolf 1061c or not. One possibility is that Wolf 1061c actually cools because of the short time scales over which its orbit changes. It will take more research before we fully understand what’s happening on the planet’s surface.
With the launch of new telescopes like the James Webb Space Telescope, the successor to the Hubble Space Telescope, in the next few years, it will be possible to detect atmospheric components of the exoplanets and display what’s happening on the surface.