Bakersfield Night Sky – January 6, 2018
By Nick Strobel
Happy New Year! Before we look at what’s upcoming in astronomy for 2018, there’s one astronomy announcement in December I want to share. It is one of the many cool things we found about Saturn as a result of Cassini’s dives between the rings and the cloud tops before Cassini burned up in Saturn’s atmosphere in September. Two lines of evidence show that the rings are relatively young. A few hundred million years ago, Saturn would have looked rather ordinary instead of being the jewel of the solar system it is today.
I’ll bet that when anyone older than four years old thinks about Saturn, they’ll have the gorgeous rings in mind. Saturn without rings is just not Saturn. We now know that up until recently those rings weren’t there. Now you’re probably thinking the same thing I’m thinking: this violates the normal view in astronomy called the “Copernican principle” but in case that doesn’t come instantly to mind, here’s a little background. Named after Nicolaus Copernicus who removed the Earth from the center of the universe with his sun-centered model, the Copernican principle says that we’re not in a special place and time in the universe. We live in an ordinary and typical spot and time.
The young rings of Saturn show us that there are some special things about this time. (Of course, the fact you and I, our kids and grandchildren are living at this time makes it special too.) How do we know the rings are young? Diving between the rings and the cloud tops enabled the Cassini team to measure the mass of the rings from the slight changes in Cassini speed due to the gravity of the rings. The lower than expected mass of the rings tells us it is more likely they haven’t been around very long (compared to the 4.6 billion year history of the solar system).
After twelve years of careful measurements of the rate of dirty micrometeorites falling onto the rings by the Cosmic Dust Analyzer on Cassini, the Cassini team found that the rate of dusting by the micrometeorites is about ten times higher than we originally thought. Therefore, the pristine clean appearance of the rings tells us they can be at most a few hundred million years old. The clean, relatively dust-free beautiful rings is like those rare and brief times when my daughter’s bedroom is all neat and tidy that you want to take a picture of it.
The year 2018 brings two total lunar eclipses. The first is at the end of this month with the “blue moon” (the second full moon of a month) on January 31. When the full moon goes through the darkest part of Earth’s shadow (the umbra), the moon takes on an orange or red color from the sunlight bending through the earth’s atmosphere scattering away the blues and greens, so only the oranges and reds make it through. The January 31 totality will be from 4:51 to 6:08 a.m. our time. Look for the orange-red moon in the western sky at that time.
January 31 also marks the 60th anniversary of the United States entry into space with the Explorer 1 satellite launched on top of a Juno booster from Cape Canaveral in Florida. Unlike the Sputnik satellite that just beeped to let people know it was in space, our first satellite was a science satellite that returned data about the Van Allen radiation belts. It is noteworthy that we wanted our entry into space to be a peaceful exploration of space.
The second total lunar eclipse will be for those on the other side of the earth (Europe, Asia, Africa, and Australia) on July 27. This total lunar eclipse will last almost two hours long since the moon will pass right through the center of Earth’s umbra and the moon will be in the farthest part of its orbit when it happens.
No total solar eclipses this year but there will be THREE partial solar eclipses when the new moon covers up part of the sun. However, you’ll need to travel far south or far north to see them. The first two on February 15 and July 13 will be best seen near Antarctica and the third on August 11 will be visible off the north coast of Siberia.
Although there will be a meteor shower almost every month, we’ll have to wait until the Perseids in August before we can see one without the moon interfering with the view. The Southern Taurid meteor shower in early November will take place during a new moon and it is usually a fairly weak shower with about ten meteors per hour at best. Occasionally, though, there will be some fireballs with the Taurids. The Geminid meteor shower in mid-December is usually pretty prolific with up to one hundred meteors per hour and a first quarter moon will set before midnight when the shower rate should be picking up.
There were no launches of planetary science satellites in 2017 but 2018 will have several. In spring the Transiting Exoplanet Survey Satellite (TESS) will launch to start looking for rocky worlds around nearby stars. The Mars Insight mission will launch in May and reach Mars in November to probe Mars’s interior. The Parker Solar Probe will launch at the end of July to study the sun’s corona up close and personal. Osiris-REX and the Hayabusa-2 missions will reach their asteroid targets in the summer and the Juno spacecraft at Jupiter will finish its work in July.
Tonight in the pre-dawn sky low in the southeast you’ll see the conjunction of Mars and Jupiter among the dim stars of Libra (see the first chart below). When the waning crescent moon passes Mars and Jupiter in the early morning hours of January 11 (inset of the first chart below), all three will fit in the same field of view of your binoculars.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com