Bakersfield Night Sky – January 16, 2016
By Nick Strobel
Bakersfield College starts instruction this coming week so I have been gearing up for a new term of teaching, planetarium shows, and various committees. The first evening public planetarium show for the spring semester will be "Oasis in Space" on February 18th. Tickets are available through Vallitix and the BC Ticket Office. In March, "Supervolcanoes" will be shown at the beginning of the month on March 3rd and the ever-popular "Black Holes" will have a showing on March 17th. In April, "Earthquake" will play on the dome on April 7th and "Dynamic Earth" will play on April 21st, the day before Earth Day. Shows will begin at 7:30 PM with the doors opening for general admission seating at 7 PM. Each one-hour presentation begins with a tour of the evening sky constellations. More details about the shows are posted on the William M Thomas Planetarium's website at www.bakersfieldcollege.edu/planetarium .
Tomorrow the third spacecraft in the Jason series should launch from Vandenberg Air Force Base at 10:42 AM. Jason-3 will extend our observations of the height of the oceans over the entire globe ("ocean surface topography") that began back in 1992 with the TOPEX/Poseidon mission. The height of the oceans can change with ocean waves, tides, currents, atmospheric changes including wind, and the amount of heat the ocean holds. Because the Earth's interior is not perfectly uniform, the gravity field is a bit lumpy. Gravity changes sea surface height by tens of meters while currents alter the height by just a few centimeters. Sea mountains, trenches, and other variations on the ocean floor can affect sea surface height as well. That means there are hills and valleys on the ocean surface. The sea surface height maps you see in the news about El Niño are the positive or negative changes in the normal ocean surface height at a given location which are up to about a foot in magnitude.
The oceans store a lot of solar energy and transport that heat over the globe, helping to keep Earth's climate balanced. The sea surface height data will be used to describe how ocean currents flow around the globe. The main government meteorology agencies, the United States' NOAA and Europe's EUMATSAT, will use the ocean surface topography data for: hurricane intensity forecasting, surface wave forecasting for offshore operators, forecasting tides and currents for commercial shipping and ship routing, coastal forecasting for response to environmental problems like oil spills or algal blooms, coastal modeling crucial for marine mammal and coral reef research, El Niño and La Niña forecasting, and figuring out longer term effects such as the Pacific Decadal Oscillation. NASA and the French Space Agency CNES will take supporting roles.
In addition Jason-3 will monitor the rise in the mean global sea level caused by climate change that is now increasing by about 3 millimeters a year. Using data from the GRACE mission that measures the Earth's lumpy gravity field and the ARGO global array of instruments on the surface of the ocean in conjunction with the Jason satellites, we now know that about two-thirds of the sea level rise is due to the melting of land ice from mountain glacier and ice sheets of Greenland and Antarctica adding water to the oceans and about one-third is due to the expansion of water as the oceans have heated up.
Jason-3 will use a radar altimeter system to bounce thousands of radar pulses off of the sea surface each second. Timing how long it takes the radio waves to travel between the spacecraft orbiting 1336 kilometers above the mean surface gives us the distance between the sea surface and the satellite when we multiply the time by the speed of the radio waves (the speed of light). The Jason-3 spacecraft also has a microwave radiometer to measure the amount of water vapor the radar pulses travel through because water vapor slightly affects the altimeter measurements. Three other instruments tied to the GPS network, the DORIS global array, and a laser array system will be used to locate the spacecraft in its orbit to within a centimeter. Jason-3 will be able to measure sea-level variations with an accuracy of 3.3 centimeters with a goal of increasing the accuracy to 2.5 centimeters (equals one inch). Pretty darn good from 830 miles up at 7.2 kilometers/second! Jason-3's orbit will be tilted by 66 degrees with respect to the equator so it will be able to cover over 90% of the Earth's oceans every ten days (9.9156 days to be more precise).
The NASA/JPL website http://sealevel.jpl.nasa.gov contains more information about Jason-3 and a very nice Flash-based tutorial on ocean surface topography for the lay person. NOAA's website about Jason-3 at http://www.nesdis.noaa.gov/jason-3/index.html is also worth checking out.
In tonight's sky, the stars surrounding Orion are all up by 8 PM. The first chart below shows the sky at 9 PM. The belt stars of Orion point down to the left toward the brightest star of the night sky, white-hot Sirius in Canis Major and point up to the right toward the cooler, orange-red star at the eye of Taurus, the red giant Aldebaran and further on to the gorgeous star cluster, the Pleiades at Taurus' shoulder. Lined up with Orion's shoulders to his left is the bright star Procyon at one end of the small constellation, Canis Minor. Procyon is between the Sun and Sirius in temperature and it is just beginning to transition out of the normal adult stage of hydrogen fusion in its core to becoming a red giant star.
Above and to the left of Orion is Gemini with the two bright stars, Castor and Pollux at the heads of each of the twins. Taurus shares a star at the tip of one of its horns with the constellation Auriga. At the opposite end of the pentagon-shaped Auriga is the bright yellow-white star, Capella that is actually a quadruple-star system with two binary systems that orbit each other. One of the binary systems puts out most of the light of the system with each star in the giant stage of its life. Below (south of) Orion are the stars of Lepus, the hare.
The Moon is at First Quarter tonight among the dim stars of Pisces below the brighter stars of Pegasus. On January 19th, a Waxing Gibbous Moon will pass in front of ("occult") the star Aldebaran. The Moon occultation of Aldebaran will begin at about 5:05 PM (before sunset) and end about an hour later for us in Kern County. The Moon will be at Full Phase on the night of January 23rd and ends the month at Third (or Last) Quarter.
By shortly after 10 PM tonight, Jupiter should be high enough above the horizon to be seen low in the east below the tail end of Leo. By the end of the month, Jupiter will be high enough to easily spot in the east at 9 PM still below the end of Leo. Orange-red Mars will be visible starting at about 1:30 AM at the far end of Virgo. It is moving fairly rapidly toward Libra reaching the top star of the scales at the end of the month. Saturn will become visible by about 4:30 am to the left of the red heart of Scorpius, the supergiant star Antares. About 50 minutes later, brilliant Venus will be visible in the stars of Ophiuchus. At the end of the month, Venus will be at the top of the lid of the Teapot part of Sagittarius and nearing the planet Mercury which will rise about an hour and a half before sunrise on that morning. The second chart below shows the pre-dawn sky at 6 AM.
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