Bakersfield Night Sky — February 4, 2017
by Nick Strobel
Tickets are still available for the William M Thomas Planetarium’s showing of “Incoming!” from the California Academy of Sciences on February 16 at 7:30 PM. Narrated by George Takei, “Incoming!” explores the past, present, and future of our Solar System and the landmark discoveries scientists have made sending spacecraft to visit tiny worlds. Tickets can be purchased at the BC Ticket Office and online from Vallitix. The doors open up at 7 p.m. The first half of the show will be a tour of the evening sky by me. The lineup for the rest of the season is posted on the William M Thomas Planetarium’s website at www.bakersfieldcollege.edu/planetarium .
A couple of cool space exploration stories came into my inbox recently. The first was the stunning view of the waves in Saturn’s rings made by the tiny moon Daphnis. Daphnis is just 5 miles along its longest dimension and it clears out a gap 26 miles wide in Saturn’s outer A ring. When the Cassini spacecraft came to within 17,000 miles of Daphnis during a recent ring-grazing pass on its highly tilted orbit, Cassini took a beautiful image that shows the ripples or waves made in the A-ring by the weak gravity of Daphnis. The image is so sharp that you can see a faint thin tendril of ring material pulled up from the ring by Daphnis. Absolutely gorgeous and to know that it’s all just gravity at work!
The ring-grazing orbits are taking Cassini high above Saturn and then speeding through the ring-plane just outside of the F-ring. The image of the Daphnis-induced waves is from the seventh ring crossing on January 16. Last Monday, January 30 was ring crossing #9 and there will be a total of 20 ring crossings before a flyby of Titan in April changes Cassini’s orbits to ones that thread the gap between the innermost ring and the cloud tops of Saturn. The last orbit will have Cassini plunge into Saturn in mid-September. Before then, we’re going to get more stunning views of the rings that have marveled people for centuries.
The second story was about the shadow cast on the dusty disk around a star called TW Hydrae indicating an exoplanet orbiting TW Hydrae. Thousands of exoplanets have been found using a variety of techniques such as looking for dimming of a star as an exoplanet passes in front of it or wobbling of a star as it is pulled upon by the gravity of an orbiting exoplanet and other methods.
The shadow of the TW Hydrae system is a unique way. The shadow on the dusty disk is not from the planet itself but from the inner part of the disk that has been lifted up and twisted possibly by the gravity of an exoplanet in an orbit that it tipped with respect to the main dusty disk. The images from the Hubble Space Telescope show the shadow rotating counter-clockwise. Archival images show that the shadow completes a rotation around the dusty disk every 16 years. Perhaps you can see from these two stories that I’m strangely attracted to beautiful shapes caused by gravity (and bad puns). Probably something in the DSM for that.
Another thing coming into my inbox was a lengthy email against the idea of climate change. I’m sure I’ll get plenty more in the coming months because I talk about the greenhouse effect and the evidence for human-caused climate change on my open-access Astronomy Notes textbook website. In the planetary science section I talk about the things that can affect any planet’s surface temperature and the carbon dioxide cycle on Earth, Venus and Mars. As preparation for the future emails, I created a short summary of what convinces me that climate change is happening and what is the evidence that shows humans are affecting the climate. It is posted at www.astronomynotes.com/solarsys/HowIKnow.pdf . There are links embedded in the document to further details on the Astronomy Notes site. Nothing in there arguing from the authority of science organizations, just the physical evidence itself.
Something that is definitely true is the brilliant Venus in our southwestern sky (see the second chart below). It is so bright that you might be able to see it in broad daylight. It is highest due south in the mid-afternoon. I say “might” because those with good eyes should see it but those with poorer eyes like mine won’t. Venus is now dropping away from dimmer Mars. Last month Venus got closer and closer to Mars and reached its closest point of almost 5 degrees (half a fist width at arm’s length) on February 1. The gap between them will be over twice that distance by the end of the month.
This column’s first star chart highlights the brilliant constellations of Orion and its neighbors. Orion is high up in the south at 9 p.m. Look for super-bright Sirius to the lower left of Orion. A waxing gibbous moon, one day past first quarter, is in Taurus. By February 10, it will be full and right next to the brightest star in Leo, Regulus.
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