An exoplanet is a planet orbiting a star other than our Sun. At the time that I am writing there are 3,565 known exoplanets, but by the time you read this, there could be over 4,000. In spite of what the media says, there have been no “Earth-twin,” “habitable,” or “Earth-like” planets found. These are cliches the media throws around which have very little scientific validity. When a scientist identifies a planet as being in a habitable zone, it simply means that water could exist on the planet in a liquid form. Scientists consider water, carbon, and oxygen essential for life. But there are many other variables that must be carefully chosen before an “Earth-like” planet could actually have life on it.
The exoplanets that have been discovered so far are an incredibly varied group. Most are too big, too hot, too gassy (like our gas giant Jupiter), or they have orbits that are too eccentric (ovals, not circles) to support life. Some planets are so hot that they rain glass. Others are so cold that no biological organism could exist on them. The stars around which these planets orbit are also an incredibly varied group with enormous ranges in size, activity, temperature, and radiation levels. In most cases, those stars are orbiting other stars making life nearly impossible.
Every day new discoveries are reported. We now understand more about how planets form, and that tells us how special our planet is. We need to take care of it, because moving to another planet is not feasible now, and may never be possible. Data from Discover magazine, April 2017, pages 40 -45.
–John N. Clayton © 2017