Bakersfield College

Bakersfield Night Sky -- October 17, 2015

Bakersfield Night Sky – October 17, 2015
By Nick Strobel

Next Saturday, October 24th, is the last of the free public star parties for the year at Panorama Bluff Park hosted by the Kern Astronomical Society. Observing through their telescopes will begin shortly after sunset and go to about 10 PM, depending on foot traffic. They set up near the intersection of Linden Ave and Panorama Drive (a little west of Greenlawn Cemetery). However, if it's cloudy, the star party won't happen, so let's hope the weather is better than the previous one during the total lunar eclipse.

In the early morning sky before sunrise today and tomorrow, you will see dim orange-red Mars less than half a degree away from very bright Jupiter as shown in the attached star chart. That angular distance is about the width of your pinky held at arm's length. Look toward the east before sunrise to see Mars and Jupiter below the stars of Leo. A bit higher up in the east will be even brighter Venus. Above Venus will be the brightest star of Leo, Regulus. You might also be able to spot Mercury very low in the eastern sky below Jupiter.

Venus and Jupiter have also been drawing closer together. On the 25th and 26th of October they will be just a degree apart, or your thumb held at arm's length (see the right inset of the attached star chart). Venus will be the brighter of the two. October 26th is also the morning that Venus reaches its greatest angular separation from the Sun on our sky ("greatest elongation") and it will rise almost four hours before the Sun does. After that date, Venus drop back toward the Sun and a telescope will show its phase becoming a gibbous as it moves farther away from us in its inside faster orbit. 

"Gibbous" means that Venus will appear more than half lit up. When it is at the farther half of its orbit, meaning it will be farther from us than the Sun, Venus will appear smaller in size but even fuller in phase. When it goes just behind the Sun, it will be at almost full phase. This is something that Galileo first saw over 400 years ago and it proved that Venus orbits the Sun. It also showed that Ptolemy's Earth-centered model was impossible.

Galileo thought that disproving Ptolemy's model would prove Copernicus' Sun-centered model correct but that was an error in logic that some church officials pointed out to Galileo. Copernicus' Sun-centered model could very well be correct but Galileo's observations did not prove it correct. Disproving one explanation doesn't make an alternative explantion automatically correct. In fact, Tycho Brahe's model of the solar system had the planets orbiting the Sun but the Sun and Moon went around the Earth. The Earth was still at the center of the solar system (and the universe). This aspect of the debate between the Church and Galileo is not shown in popular depictions of religion vs. science such as Brecht's "Life of Galileo", etc. 

However, this discussion of history is a digression of what I want to write about. That's Mars! Mars was already in the news at the beginning of the month with the discovery of liquid water present TODAY on Mars. Last week was the announcement from the Mars Science Laboratory Curiosity rover team confirming that Gale Crater did have lakes over an extended period of time. What looked like sediment layers at the base of Mount Sharp in the center of Gale Crater from the Mars Reconnaissance Orbiter between 150 and 200 miles above Mars are indeed sediments deposited over an extended time period by water.

A series of long-lived streams and lakes existed in Gale Crater (and, presumably, other parts of Mars) between about 3.8 to 3.3 billion years ago. The mudstone now left at the base of Mount Sharp shows that there were bodies of standing water in the form of lakes that existed for long periods of time. The top part of Mount Sharp, above 800 meters above the crater floor, are sediments deposited by dry winds instead of water. 

Mars once had a thicker and warmer atmosphere than it does now. The big mystery is what happened to Mars's atmosphere. The "runaway refrigerator" idea turns out to not work. The loss of a global magnetic field as Mars's core cooled and hardened is at least part of the answer. A global magnetic field shields a planet's atmosphere from the constant barrage of charged particles from the Sun called "solar wind". I'm not sure how those who want to terraform Mars will be able to shield the atmosphere after they create a thicker atmosphere. 

One last thing about Mars is a question raised at the beginning of the movie "The Martian". Are there dust storms like that depicted in the book and movie? Well, there are big dust storms that can cover the planet once every three Mars years and smaller ones that can cover continent-sized areas every Mars year. 

However, the strongest winds are only about 60 miles per hour and the atmosphere on Mars is just 1 percent as dense as Earth's. Since kinetic energy depends on velocity squared, the wind on Mars would have to travel about 10 times as fast as the wind on Earth to make up for the difference in density. So Mars's great winds would be enough to blow a plastic bag around but not enough to knock you over or break equipment. The author of the book, Andy Weir, did know about that error in his book but he needed a way to strand the astronaut on Mars. The rest he kept as accurate as possible. 

The "Fact and Fiction of Martian Dust Storms" page at mars.nasa.gov talks about what actually makes Mars's dust storms so problematic for current and future missions (manned or not) to Mars. The two major problems are the super-fine grains of dust clinging to surfaces and what it does to solar power. The first problem is the super-fine grains of dust getting into machinery and ruining mechanical gears and other moving parts. The dust would also lodge itself deeply into spacesuit fabric and it would not be healthy to breathe in. Martians are going to need to take off their suits and not track in any dust into their living quarters.

The second problem is that Mars's dust will cling electrostatically to solar panels to decrease the amount of sunlight hitting the panels. Also, dust storms can block sunlight from reaching the surface. The deposition of dust on solar panels is one reason why the Mars Exploration Rovers that landed in 2004 were not expected to last much longer than the original 90 martian days. However, every so often a dust devil would blow over the rovers and clean off their solar panels, rejuvenating their power systems. Sometimes wind can be a good thing!

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. 

--
Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com

October 17, 2015 at 6:30 AM looking East

Kern Community College District