Sandoval Signpost


An independent monthly newspaper serving the community since 1988
  Night Sky

Turn off or shield your outside lights downward. 

March 2017 night sky

—Charlie Christmann

Earth 2:

It seems like everywhere we look in the night sky, we are finding planets orbiting distant stars. Many are said to be in the habitable zone, or “Goldilocks’ zone,” where the amount of energy a planet receives from its star could allow liquid water to exist on its surface. NASA scientists believe that liquid water is the key to finding life. Over the last few decades, however, the requirement to be in the habitable zone has been debunked by findings in our own backyard. Even then, planets in the habitable zone may not actually be habitable at all.

In our solar system, we have Venus, Earth, and Mars in the habitable zone. Out of all of them, Earth is the only confirmed inhabited planet. Venus would likely be habitable with liquid oceans if its atmosphere were more Earth-like. Instead, the thick Venusian atmosphere keeps much of the heat.

The Kepler mission found thousands of exoplanets on just a small patch of sky. Some seemed to be smaller worlds in the habitable zone of their star; the press, in some cases, has gone wild about finding a second earth after these announcements.

Interestingly, many of the small exoplanets in the habitable zone orbit dwarf red stars with feeble energy output—much less than our sun. This means the planet must orbit much closer to the star where its year is counted in days, not months like Earth. These red dwarf stars have many issues that could make life difficult. First, with the planet so close to its star, the planet is likely tidally locked, meaning, like our moon, one side of the planet always faces the star. One side could be very hot, the other very cold. But, with a thicker atmosphere, strong winds could even out the temperature enough to be habitable. Also, close to a star spewing a stellar wind is not good for a planet’s atmosphere. If the planetary magnetic field is weak or nonexistent, like Mars, the atmosphere would be blown away. And finally, many red dwarfs are known to emit huge flares that could bathe the planet in deadly radiation and hasten the demise of its atmosphere.

What about planets orbiting stars similar to our sun? Assuming, again, a planetary magnetic field and a reasonable atmosphere, the chances for life improve greatly. The presence of liquid water in the habitable zone will depend upon the atmosphere. Venus, with a “normal” atmosphere, would be warm but livable. Yet, its thick blanket of air keeps the planet sweltering; its average temperature exceeds eight hundred degrees Fahrenheit. Mars, on the other hand, could be terraformed by reviving an atmosphere and have a chilly but livable surface. But, today’s atmosphere there keeps the planet cold enough to form dry ice (frozen carbon dioxide).

Okay, so much for the habitable zone planets. There are still gas giants with moons. NASA believes several moons of Jupiter and Saturn have liquid oceans under an ice layer. If true, and there are organic molecules and an energy source for food, there could be life in those oceans. This would translate to gaseous worlds outside our solar system, too. Unfortunately, a large number of the gas giant worlds have been found closely orbiting their star. Even if not tidally locked, these planets are slowly being boiled away. However, those further out would make good analogs to our home gas giants. Their moons, and perhaps even the upper reaches of the atmosphere, could harbor life. Unfortunately, scientists believe that a solid, dry surface is needed to develop technology. The chemistry of technology just does not work well underwater, especially conductive salty water. And in the clouds, it would be difficult to create anything heavier than air.

Gas giant planets are not the only place outside the habitable zone to look. The recent close up study of Pluto and Ceres make dwarf planets plausible. Pluto is suspected to have a liquid ocean below its surface. Even though that is puzzling, the planet should be frozen solid by now, life could get a foothold there. In the last several months, both organic matter and water has been discovered on Ceres in the asteroid belt. Perhaps it could have pockets of liquid water.

Astronomers are just now beginning to think about the possibility of life associated with rogue planets. Several gas giant planets have been found wandering the galaxy alone, without a parent star. Like Jupiter and Saturn, any moons orbiting a rogue planet could be warm enough to have buried liquid oceans.

All of the clues we have gathered from our own solar system will apply to the search for life many light years away in our own galaxy, as well as all the other galaxies in the universe—there is in excess of two hundred billion galaxies we can see with today’s technology according to astronomers.

Yet, we have not found a second earth; there are just too many unknowns: water quantity, temperature, atmosphere composition, and solar effects. But we are still looking. The upcoming James Web Telescope should be able to see many more planets and, hopefully, look at their atmosphere for signs of gasses associated with life, like oxygen and methane.

If you think you have what it takes to help find new exoplanets, web surf to and help with the search. Who knows, maybe you will get to name a planet. If looking closer to home is appealing, astronomers are still looking for Planet 9, a Neptune-sized planet suspected to be in a 20,000 year orbit around the sun. A citizen-science project lets you help with the search. Go to:

Now, even as my Signpost article deadline approaches, NASA, on February 20, announced a “discovery beyond our solar system” would be unveiled on February 22. Could they have discovered a second earth?

An astronomical disclaimer:

No, the bright light in the western sky after sunset is not a giant meteor coming to extinguish all life on Earth; it’s not even a small asteroid headed our direction. It’s not alien UFOs either. That bright light is just Venus at its brightest.

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