Bakersfield Night Sky – December 20, 2014
By Nick Strobel
Tomorrow marks the southern most position of the Sun's motion among the stars; at 3:03 PM Pacific Time to be more precise. That is the December solstice which for us also marks the official start of the season of winter. After tomorrow afternoon, the Sun will begin moving slowly northward and our days will slowly get longer as we head toward the June solstice. However, heating and cooling are never instantaneous, so our coldest days of winter are very likely still ahead of us.
Near the end of this December is also when we have a decent chance to spot Venus very low in the southwest sky just after sunset. The haze in our skies might prevent us from spotting Venus until mid-January but those with a clearer view to the southwest should be able to pick it out as a super-bright star just above the southwest horizon. See the second star chart below. At the end of December, you might have a chance of catching Mercury below Venus in the southwest just after sunset. In second week of January, they will be right next to each other. After then Mercury will "fall" back toward the Sun while Venus continues to move away from the Sun. Over the next several months, we will see Venus climb up higher away from the Sun as it moves around its orbit to catch up to us in August.
The other bright planet, Jupiter, is now rising east in the evening sky just a little after 9 PM. Perhaps some pastors will use Jupiter as a visual aid for their Christmas or Epiphany sermons when talking about "the star in the east" guiding the magi to Jerusalem to inquire about the child who had been born King of the Jews of the Christmas story. In fact, if the Bethlehem star was a real astronomical event, then it was very likely that Jupiter played a role in that heavenly sign. For more about possible astronomical explanations of the Bethlehem star, see my article posted at www.astronomynotes.com/history/bethlehem-star.html . Higher up in the east during the evening are two other celestial objects mentioned in the Bible: the belt of Orion and the Pleiades star cluster at the shoulder of Taurus. The first star chart belowshows the view of the eastern sky at around 10:30 PM.
Leo, Jupiter, and Cancer will be up highest in the sky in the south at around 3:30 AM. Earlier this month Jupiter was creeping closer to the Sickle part of Leo but now it is moving retrograde, backward toward the dim stars of Cancer. It will continue moving retrograde until early April.
In between Jupiter and Venus (but closer to Venus) is the much dimmer, orange-red Mars. It is now among the stars of Capricornus in the southwest sky. Mars will be setting as Jupiter rises. A very thin Waxing Crescent Moon will be just to the right of Venus on December 22nd and by Christmas Eve, a fatter Waxing Crescent Moon will be well to the right of Mars (see the second star chart below). The Moon will be at First Quarter phase on the night of December 28th and a bright Waxing Gibbous below the Pleiades on New Year's Eve.
Looking back over the past year's Night Sky columns archived on the William M Thomas Planetarium's website, there have been a number of significant astronomy discoveries and events. In the first part of 2014 was the supernova occuring in a nearby galaxy of the type used to set the scale of the universe and determining how the universe expands. Usually those types of supernova are seen in very distant galaxies so they are harder to study in great detail.
In March was the possible detection of the signature of super-rapid expansion in the VERY early universe called Inflation by the BICEP2 experiment. The BICEP2 team was examining the very subtle fluctuations in the cosmic microwave background that is the greatly redshifted echo from the early hot universe. If the detection was confirmed, it very likely meant a Nobel prize. A few months later, in the typical cross-checking of results by other research teams that happens in the peer review process of science cast some doubt on that discovery. In October the analysis of the data from the Planck space mission that mapped the entire cosmic microwave background with a very thorough analysis of the effects of interstellar dust in our own galaxy cast even further doubt on the BICEP2 detection of Inflation.
In April our local astronomy club, the Kern Astronomical Society, put on the Astronomy Day with keynote speaker Alex Filippenko, who was a member of both of the teams that discovered that the universe's expansion was accelerating and, therefore, that dark energy made up most of the energy of the universe. In May the Kepler team released a catalog with a huge number of planetary systems with multiple planets, including the exoplanet Kepler 186f. At just 10% larger than the Earth's diameter, it is the planet closest to the Earth in size and in its star's habitable zone. Since water molecules and carbon compounds are found just about everywhere in the universe, it is very likely that Kepler 186f has the ingredients needed for life.
In the summer, the Orbiting Carbon Observatory-2 successfully launched and began measuring carbon dioxide levels all over the globe with the precision and resolution needed to characterize the sources and absorbers of carbon dioxide. Monitoring how the Earth "breathes" is one important part of understanding the complex system that makes Earth such a nice place for life. In August the Rosetta spacecraft finally rendezvoused with Comet 67P/Churyumov-Gerasinmenko and began looking for a place to land the Philae Lander in the first-ever landing on a comet later in November.
In September the MAVEN and MOM spacecraft arrived at Mars and began studying Mars's atmosphere just before Comet Siding Spring buzzed Mars in October. In October we also got to see a nice total lunar eclipse under clear skies, followed two weeks later by a partial solar eclipse.
In November the Philae Lander did successfully land on Comet 67P but part of the landing equipment did not work properly, so it bounced twice and settled against a cliff wall at such an angle that it could not recharge its batteries with the solar panels. Before it went into hibernation, it did manage to make several measurements with its suite of scientific instruments. Maybe as the comet gets closer to the Sun, it will be able get enough solar energy to reawaken. In the meantime, the Rosetta orbiter will watch how the comet changes as it heads toward its closest approach to the Sun in August. Scientists are still analyzing the treasure trove of information Philae beamed back to us in in the brief time that it was awake. The Rosetta orbiter has already determined that the water making up the comet has a different enough ratio of heavy water to regular water to tell us that comets like Comet 67P could not have supplied the Earth with its water soon after it had cooled off from its formation. Heavy water has deuterium instead of ordinary hydrogen for one or both of the hydrogen slots in H2O. Some comets such as Hartley 2 do have the same isotopic ratios of heavy water vs. regular water as the Earth does, so at least some of the water on the Earth could have come from comets. Some of the water also came from watery asteroids colliding with the Earth and some water was from Earth's original formation when it had a molten magma ocean at the surface. Linda Elkins-Tanton and her students have shown that not all of the water molecules would have boiled away during that early hot stage of the Earth's existence.
The year 2015 promises to be another exciting year in space exploration as two more spacecraft reach their destinations but that will be the topic of the next column.
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