Goldilocks Planets

4/29/07 – 5/5/07
by C. Zaitz

The news is that astronomers have found a new planet orbiting a distant star. Astronomers have been finding planets in distant solar systems for decades, but usually the planets they discover are huge, more like Jupiter on steroids than anything earth-like. With better telescopes and more research, we are beginning to see the smaller planets. One in particular is being heralded as a “Goldilocks” planet, not too big, not too small, nor too cold, nor too hot. A “just right” planet that could possibly harbor liquid water, pretty sunsets, or even life. At least that’s the theory.

Sometimes we refer to our neighboring planets as having the “Goldilocks syndrome.” Mars and Venus are our cosmic neighbors, and together, we three planets all orbit within a distance from the sun called the “habitable zone,” where the amount of solar radiation reaching the surface is conducive for reasonable temperatures. So why did earth alone develop life, so prolifically and thoroughly that not even cataclysmic events could completely wipe it out? And what went wrong with our neighbors?

Venus is a study in what can go wrong with a nice planet. Venus and earth have plenty in common. They are very close in size, composition and their distance from the sun. However, Venus ended up with a very big problem: a runaway greenhouse effect. The effect of atmosphere trapping solar radiation and making a planet warmer than it should be is common- earth and Mars also have it. However, perhaps because it gets more solar radiation or because it had more carbon dioxide in its atmosphere, Venus is in a vicious cycle where its thick clouds trap nearly all the sunlight coming in. It simply cannot cool itself off. As we raise the level of certain gasses in our own atmosphere, we run the risk of having our greenhouse effect go astray. The current warming trend of our planet is a giant red flag that we are indeed starting a process that we would not be able to stop, much less reverse.

Mars, due to its further distance from the sun or its diminutive size, has too little atmosphere, and thus too little greenhouse effect. It is too cold on the surface of Mars for water to exist in liquid form, so it ended up a dry, cold desert-like planet. We know that Mars once was warmer and are convinced that water used to flow, but unless the conditions are just right, a planet goes awry and climate changes ensue.

The newly discovered Goldilocks planet is orbiting a red dwarf star called Gliese 581, about 20 light years away. The planet is heavier than earth, with a rocky surface and most likely liquid water. That’s a lot of information about this planet, since the data they gathered is mostly about how Gliese 581 wobbles. From this wobble, astronomers can glean information about what is going around the star to make it wobble. They infer size, distance, and even composition from the wobble. They have surmised that Gliese’s planet may be very much like earth, perhaps a “just right” place where water and life could exist. However, as we look at our neighboring planets, we see a lot of variation in a planet’s fate. It will be interesting to learn more about these extra-solar planets. Even if we don’t find life, perhaps we will find answers to how planets behave, giving us insight to our own problems and possible solutions.

Until next week, my friends, enjoy the view.