Bakersfield College

July 7, 2012

Bakersfield Night Sky – July 7, 2012
By Nick Strobel

In less than a month (August 5th), the Mars Science Laboratory, aka "Curiosity" will either land or crash on Mars. Curiosity is by far the largest rover, heck, even the largest craft of any type, to land on Mars and NASA will be using new techniques to get that rover onto Mars. NASA/JPL recently released the "7 Minutes of Terror" video about all the things that have to work absolutely correct for this thing to succeed and the list is pretty daunting. The seven minutes refer to the time when the craft is traveling through Mars' atmosphere to the touchdown (or fatal crash). Curiosity will hit the upper atmosphere at about 13,200 mph and the air friction is so intense that the spacecraft heats up to over 1600 deg C and possibly as high as 2100 deg C (3800 deg F). The craft's heat shield will prevent that heat from frying the rest of the rover but the heat will also ionize the surrounding air enough that radio communication between the Earth and the craft will not be possible. The seven minutes also refers to the additional time we'll have to wait to see if everything worked perfectly because of how long it takes the radio waves traveling at the speed of light to finally reach us here on Earth. On August 5th, the distance between Earth and Mars will be such that it will take fourteen minutes for the radio waves to travel from Mars to Earth.

Curiosity has been built smart enough (we hope) to take care of any anomalies during its descent by itself without any help from us. Remember that it takes seven minutes from hitting the top of the atmosphere to landing on the surface, so by the time we have received radio communication from Curiosity that it has reached the top of the atmosphere, it will have already been on the surface of Mars dead or alive for seven minutes. A number of things have to go right including: aerobraking through an atmosphere just 1% as thick as ours, withstanding all the heat generated from that aerobraking, small thrusters firing several times a second during the aerobraking phase to guide the package to stay within a very small window, deploying the largest supersonic parachute used on Mars when the craft is still moving at 1000 mph and surviving the 9 g's deceleration when the parachute deploys, ejecting the heat shield after parachute deployment so that the radar can locate its target landing area, separating from the parachute package when it is still falling at 200 mph and firing the skycrane's rockets with a radical horizontal thrust to avoid hitting the still-falling parachute package, lowering the rover from the skycrane on a 21-foot bridle so that the rocket's exhaust doesn't kick up too much dust into the rover's instruments when it reaches the surface, and cutting the bridle on touchdown and then diverting the skycrane very far from the rover to land (crash) elsewhere. These are only some of the challenges—go to the video section of Curiosity's website at http://mars.jpl.nasa.gov/msl/ to view the rest.

In other space exploration news, there's the first manned docking with the Chinese space station, Tiangong 1, followed by the crew's successful return to Earth at the end of June. A couple of days later, an international crew of three from the International Space Station, including American astronaut Don Petit, returned to Earth after six-and-a-half months in orbit. They left behind three people, including American astronaut Joe Acaba. Those three will be joined by another three people, including American astronaut Sunita Williams, on July 17th. The Chinese expect to return people to Tiangong 1 next year. While China appears to be catching up to us in terms of technology and economic and military power, if historians like Niall Ferguson are correct, they don't have a crucial ingredient in their society to enable them to overtake us: the rule of law based on private property rights within a representative government. Something to think about as we finish celebrating Independence Day this week. Well, I won't digress into a long discussion about that since this is an astronomy column (much to the relief of my editor I'm sure), but I do wonder if developing and trying out something like the Mars Science Laboratory with all of its seemingly crazy innovations would have been possible anywhere else besides the United States.

In our night skies in Kern County the main attraction continues to be the close pairing of the two brightest planets, Venus and Jupiter in the pre-dawn sky. Look for them low in the eastern sky in the constellation in Taurus shining brighter than any other object except the Waning Gibbous Moon. They may just fit within the same field of your binoculars tomorrow morning—Jupiter will be above Venus. Right next to Venus will be the orange-red eye of Taurus, the star Aldebaran. Lined up with Jupiter and Venus and slightly more than one binocular field of view above Jupiter will be the Pleiades star cluster at the shoulder of Taurus. The Moon will be at third or last quarter on the 11th and it will pass between Venus and Jupiter as a very thin Waning Crescent on the 15th. That should be a pretty sight with or without binoculars for you early risers. The previous early morning (on the 14th) the Waning Crescent Moon will make another nice sight with binoculars as it passes below the Pleiades. Both early mornings are shown in the inset of the attached graphic.

As Venus pulls away from Jupiter for the rest of this month, Mars and Saturn are getting closer together in our evening sky. As shown in the attached graphic, tonight they are 20 degrees apart from each other (about the distance between your pinky and thumb when your fingers are spread out and held at arm's length). Mars will be on the western (right) side of Virgo and Saturn will be on the eastern (left) side of Virgo right above bright Spica. By the end of the month Mars will be just 8 degrees away from Saturn (less than a fist width held at arm's length). Before then on the 15th, Saturn will be 90 degrees from the Sun, so a telescope will show Saturn being lit by the Sun from a bit to the side. Saturn's shadow on the rings will be particularly noticeable. The Waxing Crescent Moon will pass by them on the evenings of July 24th and 25th. Tonight and in the coming week, look for Mercury low in the west just after sunset.

The only other notable event in July already took place by the time you read this: Earth was farthest from the Sun on the evening of July 4th. As the legal fireworks were going off, the Earth was 94,506,000 miles from the Sun. However, the high altitude of the mid-day Sun and long time it was above the horizon made the summer day quite warm despite the greater distance.

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

Kern Community College District