Bakersfield Night Sky – December 17, 2011
By Nick Strobel
Well, we're almost there. Interstellar space, it is. (What else do you think I'm referring to??) Voyager 1, launched in 1977 to explore the two largest planets of our solar system and then flung out by Saturn's gravity at a fast enough speed to escape the Sun's gravity, is at the boundary of the bubble produced by the Sun's solar wind pushing out on the interstellar gas and magnetic field. Voyager 1 is now 11.08 billion miles from the Sun, or 119.1 times farther out from the Sun than the Earth is. Heck, it's even further out than Pluto or Eris that can get out to 4.54 billion miles and 9.07 billion miles from the Sun, respectively, in their elliptical orbits! Eris, you may recall, is the dwarf planet discovered in 2003 that eventually led to the creation of the "dwarf planet" category and re-classification of Pluto as a dwarf planet. Now, now, before you get all grumpy over what happened to Pluto, this was actually a good thing, not a demotion. Before the re-classification, Pluto was the "odd ball" of the solar system. There was the family of four terrestrial worlds close to the Sun (Mercury, Venus, Earth, and Mars), the family of four jovian worlds far from the Sun (Jupiter, Saturn, Uranus, and Neptune), and then this poor, little, planet all by its lonesome far from all of them. A tear comes to my eye as I think of how lonely it must have been... But then we found Pluto's family! It includes other dwarf planets out in the Kuiper Belt like Makemake, Haumea, Eris, and several others waiting to be discovered. Doesn't it make the heart swell to know that Pluto is part of a family of dwarf planets—like returning home for the holidays. Sigh! (Editor's note: must remind writer next year to not write column right after watching several Christmas specials.)
Back to Voyager 1: several folks noted to me the news of Voyager's accomplishment that made the national news last week. At such a great distance it really is FAR away, so far away that it is easy to think that it's out of the Galaxy. Well..., not quite. To give you some perspective on the scale of things, let's say we scale down the Galaxy so that Pluto's orbit can fit within a quarter coin. One end of Pluto's orbit to the other end of the orbit inside a quarter coin. (That would be about 40 Earth orbits across.) On this scale, Voyager 1 would be almost 1.5 quarter coin-widths from the Sun. The next star would be about 82 meters away (a meter is one big step). The Milky Way would be the size of the western United States, stretching from Los Angeles to Pierre, South Dakota. Hmm...maybe Voyager 1 isn't really so far away after all.
The other major astronomy event this month is still to come: the December solstice, when the Sun is as far south of the Celestial Equator as it gets all year and our season of winter officially begins (and summer begins for those in the southern hemisphere). This will happen on December 21st at 9:30 PM PST. The night of December 21st to 22nd will be the longest night of the year for us in the northern hemisphere. The Moon will be a very thin Waning Crescent becoming visible just a little before 5:30 AM, so the night belongs to the planets and the stars. A few days later on Christmas Eve will be the New Moon.
On Christmas Eve, Santa and those leaving Christmas Eve services at midnight will see the brilliant stars of Orion in the middle of the southern sky with the belt stars pointing down to the left to the brightest star in the sky, Sirius in Canis Major, and pointing up to the right to the lovely Pleiades star cluster at the shoulder of Taurus, the bull charging Orion with the fiery-orange Aldebaran at its eye. The king of the planets, Jupiter, will be about a quarter of the way up in the southwestern sky reflecting so much sunlight it will outshine the rest of the objects in the sky. See the first star chart below for this view. In the east will be Leo with the sickle shape at its head and the bright star, Regulus at the base of the sickle. Orange-red Mars will be below and left of Regulus, below the triangle part of Leo marking his hindquarters and tail. See the second star chart below for this view. The bright star of Virgo, Spica, will become visible in the east at about 2:15 AM and Saturn will be nearby a few minutes later to the left of Spica. At the time your kids or grandkids will be waking you up so that you can open presents (6 AM), Mercury will be very low in the east near the red heart of Scorpius, Antares as shown on the third chart below. By then, Mars will be due South two-thirds of the way up to the zenith, Saturn will be almost halfway up in the southeastern sky, and mighty Orion will have set with one of his hunting dogs, Canis Minor with bright Procyon, following close in his master's footsteps low in the west.
Although we are constantly being bombarded by messages to spend, spend, spend during this holiday season, I hope that you will consider boosting the economy in a different fashion by donating to a worthy charity in honor of someone else. I also hope you all have a blessed and joyous holiday season and safe travels!
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