Bakersfield Night Sky – December 5, 2015
By Nick Strobel
The largest, deepest survey of distant solar-system objects has found the farthest object in our solar system, an object called "V77404" for now, that is nearly 10 billion miles from the Sun. That's over twice as far as Pluto gets from the Sun. A team of astronomers led by Scott Sheppard is using the world's largest telescopes to hunt for a distant family of objects in the scattered belt. These objects might possibly indicate the presence of an undiscovered massive planet way beyond the orbit of Neptune.
V77404 might be 300 miles or more across. Astronomers estimate its size by measuring how dim the object is and assuming how much light the object reflects. If the object reflects 15% of the sunlight that falls on it, then it will be about 300 miles across. If the object is less reflective, then it would have to be larger to produce what light we do see.
Other objects that reside at similar distances include Eris (the dwarf planet that made us reclassify Pluto), Sedna, 2007 OR10, and 2012 VP113 among others. Further observations are needed to figure out the shape of V77404's orbit and thereby, determine how it got out so far from the Sun.
In very early solar system history research, two astronomers, Kaveh Pahlevan and Alessandro Morbidelli, at Universite Cote d'Azur in Nice, France may have figured out why the Moon's orbit is tilted as much as it is. The Moon's orbit is tilted by 5 degrees with respect to the Earth's orbit around the Sun which is why we do not have an eclipse every month. The giant impact 4.5 billion years ago that led to the formation of the Moon from the coalescence of the debris should have the resulting orbit be tilted by no more than 1 degree.
Pahlevan and Morbidelli started off with the reasonable assumption that the early solar system had many large planetesimals or mini-planets with masses between 0.1 to 1 times the mass of the Moon roaming around in neck of the woods. Those objects eventually found themselves falling into the Sun, crashing into the Earth or another planet, or being ejected from the solar system entirely in the 100 million year timespan after the Moon formed.
The two astronomers used thousands of computer simulations to find out that many close flybys of the planetesimals could have tugged the Moon into a greatly tilted orbit. The Earth's gravity would have then, ever so gradually, adjusted the Moon into a more closely aligned orbit over the next several billion years.
The two astronomers also find from the simulations that enough of the mini-planets would have impacted the Earth to explain the unusually high proportion of gold, platinum, and iridium in the Earth's crust. If those materials had been part of Earth's formation, they would have melted and sunk to the core when the young Earth melted and the heavy metals sank to the core and the lighter materials floated up toward the surface.
Much closer to home in space and time, you'll find the brilliant stars of Orion rising in the east by shortly after 7 PM. The stars of Taurus will be above Orion with V-shaped formation at its nose, the orange-red giant star Aldebaran at its eye and the beautiful Pleiades star cluster at its shoulder. The belt of Orion makes a line upward to Aldebaran. If you extend the belt line downward, you'll get to Sirius, the brightest star in the night sky. Sirius will be visible starting about 9 PM as shown in the first chart below.
Above and to the left of Taurus is pentagon-shaped Auriga with the bright yellow-white star Capella at one vertex of the pentagon. To the left of Orion are the stars of Gemini with the bright stars, Pollux and Castor, at the heads of the twin brothers. High up in the southwest will be the Great Square of Pegaus and almost overhead will be the stars of Andromeda among which you can spot the farthest object visible without a telescope, the Andromeda Galaxy over 2.5 million light years away. The light from that galaxy left it when the early hominids were walking around on the Earth. Low in the west the cross shape at the center of Cygnus will be nearly upright, vertical at 9 PM.
In the early morning, pre-dawn sky, the constellation Virgo holds the interesting solar system objects. The second chart below shows this view. At 5:30 AM, the bright planet Jupiter will be about half-way up in the east in between the stars of Leo and Virgo. Orange-red Mars will be near the middle of Virgo, a Waning Crescent Moon will below Mars but above the bright star Spica, and super-bright Venus will be on the lower edge of Virgo.
With binoculars scan to the left of Venus to see if you can spot Comet Catalina. Both Venus and Catalina should appear in the same field of view of your binoculars in early December. During the daytime of December 7th, you can see the thin crescent of the Moon cover up Venus. About a week later, on the night of December 13th/14th, the Geminid meteor shower peaks. Bundle up since it's now quite cold at night!
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