November 2012 Sky from the Keeble Observatory
Our last column was in September – doesn’t time fly when we’re having fun? I suppose I could blame the lack of an October column on all the robo-calls leading up to the election, but the reality is that it just slipped by me!
Planets have been in the science news of late, so let’s see what’s new.
Curiosity continues to perform its job of surface exploration on Mars. It hasn’t moved terribly far, since it keeps stopping to do science. They’ve analyzed soil samples (similar to terrestrial basalts – i.e. volcanic rock from places like Hawaii), tested the atmosphere for methane (not much, if any), and measured the isotope ratios in atmospheric gases. They’ve found that slightly more of heavy isotopes of carbon are present in the carbon dioxide than in terrestrial CO2. This suggests that the currently very thin atmosphere (about 1% the density of our atmosphere) is the remnant of one once denser, and that the loss of gas was from the top of the atmosphere rather than being trapped chemically in the solid surface, because the lighter molecules would be more likely to escape at high altitudes.
The Cassini probe at Saturn detected a huge “belch” of methane in a storm which carried warm gas from the interior to the cloud layers. This gas was several hundred degrees warmer than the clouds it penetrated.
Planets in the Alpha Centauri system are a long popular trope in science fiction – I can’t tell you how many novels I’ve read which include them! Now we know of at least one! A roughly Earth sized planet is orbiting Alpha Centauri A, an essentially Sun like star only 4 light years away. Before you pack your bags for a visit, it’s extremely close to its star, and the surface is likely to be molten rock rather than solid.
Last August, observers using the Kepler probe announced the discovery of a pair of planets orbiting a pair of stars! Kepler 47 is a binary system which includes two stars. One is a bit cooler than the Sun, the other is much cooler and smaller. One of the two planets orbits in the so-called habitable zone, i.e. where the temperature would be close to what we find on Earth. However, these planets are probably more like Neptune than Earth.
Next month we’ll talk about how we detect these planets, and how we think we know how big they are.
Lunar phases for November: Last Quarter on the 6th, at 7:36 pm; New Moon on the 13th, at 5:08 pm (There will be a total solar eclipse, but it won’t be visible here. Catch a flight to Australia, New Zealand, and New Caledonia if you want to see it!); First Quarter on the 20th, at 9:31 am; Full Moon on the 28th, at 9:46 am (There will be a penumbral lunar eclipse, but you won’t see it in daylight!).Evening planet watchers will have to content themselves with following Jupiter, which rises to the east about 7:00. It will be bright to the south after midnight, about 70 degrees above the horizon. Venus and Saturn rise to the east before sunrise, Venus will be about 30 degrees above the horizon, and will be the brightest object until the Sun clears the horizon. It rises about an hour before Saturn, so Saturn will be lower and much fainter, if you can pick it out of the predawn twilight. Saturn will rise a little earlier each day, so expect it closer and closer to Venus as the month advances. Mercury joins them by month’s end.
Looking overhead at mid-month, about two hours after sunset you will find the Milky Way dividing the sky from northeast to southwest. Deneb and Vega are the two bright stars to the west of zenith, with Altair to the southwest marking out a rich triangle. Near Vega, a clear night and steady hand with binoculars may enable you to see the Ring Nebula. This is an example of what will happen to our own Sun in another five billion years … as the fuel in the core is used up, the outer layers will eventually be expelled into an expanding planetary nebula. To the east of zenith, look for the Andromeda Galaxy, a faint smudge to the naked eye. This is actually a galaxy much like our own, over 100 billion stars yet dimmed by its vast distance of some 2 million light years. Even though it is the most distant object visible without a telescope, it is close by on the cosmic scale of things.
Deneb marks the “tail” of the constellation Cygnus. The “head” is a faint binary called Alberio, which is one of the most beautiful pairs you’ll see. With a small telescope, one star glows a brilliant blue while the other is bright orange. Cygnus lies in the general direction of the Sun’s orbit around the center of the galaxy, which lies in the direction of Sagittarius, which is just setting on the southwest horizon.
Just rising to the east is bright Aldebaran, in the constellation Taurus. This is a harbinger of coming winter. By month’s end we will see Orion rising at this hour.
Copyright 2012George Spagna