Bakersfield Night Sky – April 6, 2013
By Nick Strobel
Mars will be going behind the Sun in another week but it is already too close the Sun on our sky for us to see it against the glare of the Sun. It is also too close to the Sun line for us to safely send commands to the spacecraft orbiting around or roving on Mars. All of the hot plasma above the Sun's surface can mess up radio waves trying to pass through it on its way to a planet on the far side of the Sun. April 4th to May 1st is the moratorium on transmitting commands to Mars but our robot explorers will continue doing routine observations on the ground and in orbit.
Before the communication blackout, the computers on Curiosity were back to doing science again after recovering from a couple of computer software glitches that put it into "safe mode", waiting for the engineers at the Jet Propulsion Laboratory, south of us in Pasadena, to figure out what went wrong. It looks like the computer bug is figured out but now Curiosity will wait until it can talk to Earth again before resuming its exploration of the rocks of Mars in our careful search for possible ancient life on Mars long ago.
An important step in that search is to determine how habitable Mars might have been long ago. Besides liquid water, life would need to have some source of energy to drive its metabolism. A few weeks ago, the Curiosity rover drilled into a sedimentary rock in Gale Crater. Drilling into the rocks may give us information about the conditions on Mars further back in time than what the Mars Exploration Rovers can give us with their wire brush tool. The rock powder from Curiosity's first drillings were gray with a hint of green, not red, from olivine and magnetite that have less oxygen than the hematite found in rocks studied by the Mars Exploration Rovers. The different amounts of oxygen bonded with the materials in the rock could be used as a sort of chemical battery by micro-organisms. In addition, the rocks Curiosity is studying would be better at preserving organics than the rocks studied by the Mars Exploration Rovers. The rock drilled into by Curiosity has the key ingredients for life, things like sulfur, nitrogen, oxygen, phosphorus, and carbon. The rocks at Curiosity's location were formed from neutral or mildly alkaline water that wasn't too salty instead of the extremely high acidity and saltiness of the water that would have formed the rocks explored by the Mars Exploration Rovers. Examinations of other rocks in the area explored by Curiosity show that the Gale Crater floor was soaking wet more than once. So far, no organic compounds have been found yet by the SAM instrument on Curiosity, but one thing for sure is that ancient Mars was definitely habitable, able to support microbes long ago. Another drilling of the rock to confirm the results will be done after the communication blackout.
In this evening's sky facing west you will see bright Jupiter shining above the head of Taurus at around 8 PM (see the first chart below). Down to the left of Jupiter is orange-red Aldebaran at Taurus' eye and down to the right is the Pleiades cluster at the shoulder of Taurus. If you have sharp eyes you may be able to count six stars making a tiny dipper-like shape, though light-polluted skies will make that a challenge. I had one sharp-eyed student say that he could count nine stars in the Pleiades from his house near Tehachapi. I was a bit skeptical at first, but when he said he could also spot Uranus and could correctly point out its position, skepticism was replaced by amazement! A line drawn from Aldebaran to Pleiades and extended further down will eventually run into M31, the Andromeda Galaxy---the closest large galaxy to us and the farthest thing you can see without binoculars (though I wonder if my sharp-eyed former student could spot a galaxy even farther away). The Andromeda Galaxy will be slightly less than a fist width above the horizon at 8 PM. With your binoculars you should be able to see the faint fuzz ball with a tail we know as Comet PanSTARRS (C/2011 L4) to the right of the Andromeda Galaxy. The two were closest on the sky on Thursday. PanSTARRS is now about 124 million miles away and continues to move away from us. I always had to use binoculars to find the comet in the Bakersfield sky even when it was at its best appearance a few weeks ago (but that sharp-eyed former student was probably picking it out very easily without binoculars---can you tell I'm a bit jealous of his eyesight?).
To the left of Taurus in the evening, you will see Orion with his distinctive belt of three bright stars lined up (see the Orion Belt inset in the first chart below). People have noticed those belt stars for well over a couple of thousand years at least---they are mentioned in a couple of places in the Old Testament part of the Bible (along with the Pleiades) and in parts of the Middle East, they are known as the "string of pearls". Although the belt stars look like they belong to each other, we now know that they are definitely separate from each other in space. The leftmost star of the belt is Alnitak, a hot blue supergiant 800 light years away that is over five times hotter than the Sun and a 100,000 times as luminous. It has a smaller blue normal adult star companion and it takes thousands of years for the two to orbit each other. The middle star is Alnilam, a hot blue-white supergiant 1340 light years away that is over four times hotter than the Sun and a whopping 375,000 times as luminous. The rightmost star is Mintaka. Of the sky's brighter stars, Mintaka is closest to the celestial equator, the projection of the Earth's equator onto the sky, so it will rise almost directly east and set almost directly west. Mintaka is 915 light years away and is actually a complex system of stars of two binary systems. Two faint binary stars, visible only with a telescope, are in an orbit about a quarter of a light year away from what looks like the single bright star Mintaka in a telescope. However the single bright star Mintaka we see is actually a "spectroscopic binary"---a system of two stars that are too close together to distinguish as separate stars in even the largest telescopes but whose binary nature is revealed in its spectrum. (So that's a faint binary orbiting a bright binary---four stars in a gravitational dance.) Both of the stars in the spectroscopic binary are five times or more hotter than the Sun and radiate nearly 90,000 times as much as energy as the Sun. If you extend the line of the belt stars to the left, you will get to the brightest star in the night sky, Sirius, at the nose of Canis Major. In this evening's sky, only the planet Jupiter will be brighter. The Moon will be even brighter but as a very thin Waning Crescent, it won't rise until around 5:30 AM tomorrow morning.
Turning around to face east at 8 PM, you will see the spring constellation of Leo halfway up in the east with the backward question-mark ("the Sickle") at the top and the triangle representing the lion's hip, back leg, and tail at the bottom (see the second chart below). Just beginning to come up in the east are the stars of Virgo. You might have to wait until 8:30 PM to easily see Virgo's bright star Spica. Already up by 8 PM just north of Virgo is Bootes with the very bright star, Arcturus, at the end of the kite-shaped constellation. Of the stars we can see at night from the Bakersfield metro area, Arcturus is the second-brightest star (only Sirius is brighter). In the northeast, the Big Dipper part of Ursa Major will be almost standing up on end. If you extend the arc of the Big Dipper's handle, you will arc your way to Arcturus ("arc to Arcturus"). At 9:30 PM, you will be able to see Saturn rising in the east below the stars of Virgo.
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
last updated: April 1, 2013
Webpage contact: Nick Strobel