Bakersfield Night Sky – February 18, 2012
By Nick Strobel
Thanks to great public support, the February 23rd show "Oasis in Space" at the William M Thomas Planetarium at Bakersfield College is sold out. Tickets for the next show "Black Holes" will go on sale Friday, February 24th, at the BC Ticket Office. Oasis in Space focuses on one aspect of a habitable place: liquid water. My previous column gave the several reasons why liquid water is probably the liquid that complex life will use as the medium for biochemical reactions. Other things that a habitable place will need to have are a stable temperature regime provided by an energy source such as a star or some sort of geological activity, a supply of the essential building block elements, a solid surface and enough gravity to keep an atmosphere. Planets or moons without an atmosphere could have life below the surface but it would require landers to find it. For the exoplanets that would take many tens of thousands of years of travel time with our current technology. An atmosphere shields surface life from harmful radiation, moderates changes in temperature between night and day, and provides the surface pressure needed for liquid water to exist. The atmosphere will need to have a shield from the star's stream of charged particles flowing outward (e.g., our Sun's solar winds) provided by a magnetic field to prevent the atmosphere from being slowly whittled away by the charged particles like what happened on our next door neighbor Mars. A global magnetic field requires a warm enough interior to liquify a conducting material such as the iron-nickle in the Earth's outer core.
Essential building block elements will be atoms such as carbon, hydrogen, nitrogen, and oxygen with carbon most likely providing the basis for life because of carbon's great versatility to form compounds with other elements and even with itself. In something that could be a great example for a sermon, carbon's willingness to share its electrons with other types of atoms and itself is why it can create such a great variety of chemical compounds. There are far more types of organic compounds (molecules containing carbon and usually also hydrogen) known than all the other types of compounds combined. Silicon is another favorite basis for life for science fiction writers because silicon is also fairly versatile in bonding with other atoms. However, carbon is much more versatile and when carbon oxidizes (combines with oxygen), it forms a gas while silicon forms a solid. On a planet with carbon-based life and life using silicon as a base, the carbon-based chemical reactions would be far more efficient than the silicon-based ones, so the carbon-based life would quickly overrun any silicon-based life present on the planet. Finally, carbon is about seven times more abundant in the universe than silicon because it is easier to make in the cores of stars.
The planet or moon will need a solid surface to concentrate the building block elements together in the liquid on top (for detectable surface life) or at least in a thin layer near the surface as may be the case with Jupiter's moon, Europa, and Saturn's moons, Enceladus and Titan. There is a possibility that a habitable planet might require plate tectonics to be operating because of its role in long-term climate stability, magnetic field generation, and promotion of a high level of biodiversity by the creation of new environments that life would have to adapt to. If the development of complex life requires a world with plate tectonics, that would place much narrower constraints on the surface habitability of worlds than we thought before. Again, it is only surface life that we can detect from afar. Detecting sub-surface life requires landers. The universe will undoubtedly surprise us but we do have to make the effort to look and be curious in the first place.
In our evening sky, Venus continues to close in on Jupiter. Those are the two super-bright "stars" you will see in the southwestern sky after sunset. Venus is the one closer to the horizon. Venus is now in the middle of Pisces while pokier Jupiter is at the western edge of Aries above the head of Cetus. The first chart below shows the view toward the southwest at 6:30 PM. Tonight orange-red Mars will become visible in the east at about 7:30 PM. Mars is moving backward among the stars of Leo which will make it rise even earlier as the weeks progress than expected from the usual sidereal day shift of the stars each succeeding night. The second chart below shows the 9 PM sky when Mars will be comfortably above the eastern horizon. Tonight Saturn will become visible in the east at about 10:45 PM to the lower left of the bright star Spica in Virgo. The third chart below shows the pre-dawn sky at 6 AM with Saturn and Mars visible in the west. The very thin Waning Crescent Moon may be barely visible in the pre-dawn twilight low in the east on Sunday morning. It is at New Moon phase on the 21st. On the evening of the 25th, the Waxing Crescent Moon will be slightly above the bright Venus in the southwestern sky after sunset—a beautiful sight in your binoculars and your camera (see the first chart below). A similar beautiful arrangement follows on the next night with Jupiter. On those evenings, see if you can spot Mercury in the twilight glow just after sunset about three fist-widths held at arm's length below Venus.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com