Merry Christmas!
Have a very merry Christmas!
Take it easy out there. This is a heavy travel time, with some of winter’s worst weather. We want you around for International Astronomy Year - 2009.
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How much larger is Mars now then in 2010
Here is a chart that shows the relative size of Mars during its close approaches from nowtill 2027. Mars will not be as large in the sky as it is tonight until some time in 2016, so while this is not a “good opposition” this is as good as it gets for quite a while. To see Mars at its best we need to wait until 2018.
The Day the Sun Stood Still
It’s the end of Autumn as we know it; the shortest day; the winter solstice. It is the day the sun stands still.
It is the beginning of winter in the earth’s northern hemisphere, summer in the south. The instant of the winter solstice or winter “sun standstill” is 1:08 a.m. EST December 22nd this year. That’s 6:08 UT or universal time. Instead of bringing terror, the ancients celebrated at the solstice. The motion the ancients saw was the movement in the altitude of the sun at noon day to day.
From the first day of summer the altitude (angle above the horizon) of the sun falls. Here, where I live, the peak altitude of the sun at the summer solstice is about 68.5 degrees altitude. The descent of the sun at noon starts imperceptibly at first, but by the autumnal equinox, the altitude of the sun at noon is down to 45 degrees.
The ancients weren’t too sure that the sun wouldn’t stop its southern motion. It always had before, but not knowing the mechanism, being superstitious, and believing in a host of capricious gods they weren’t too sure. So in December when the sun slowed its southward rush and finally stopped they celebrated. The Romans had the most famous of these celebrations called Saturnalia. Sure it was supposedly about the god Saturn, but really it was about: The sun is coming back! Around here the sun will bottom out at 21.5 degrees altitude. Click here for one of my old articles about the why of the seasons.
The persecuted Christians slipped in the celebration of the Nativity, so their celebrations would go unnoticed. Sort of like today.
Mars is at its closest this time around
Mars will be its closest to the earth this apparition at 7 p.m. EST on the 18th (0 h the 19th UT). The distance will be 0.589 AU or about 54.7 million miles. That’s about 20.1 million miles farther than it was at its closest in 2003. Back then Mars was 25.1 seconds or arc in diameter. (1 second of arc is 1/3600th of a degree. the sun and moon are about 1,800 seconds of arc in diameter) On the 18th Mars will be only 15.9 seconds of arc in diameter. It will be a very challenging sight for the small telescope. For best viewing, allow Mars to rise high in the sky to avoid the worst of our atmospheric turbulence. It is a luxury we didn’t have in 2003 when Mars rode low in the sky. Mars will be quite a challenge for the observer, but rewarding for the diligent observer.
In its orbit Mars is currently moving away from the sun, so even though it won’t reach opposition from the sun on the 24th, where the sun, earth and Mars are most nearly in line, Mars will already be pulling away from us. If Mars and the earth had circular orbits the date of opposition would be the date of closest approach.
Happy Birthday Arthur C. Clarke
Today is the 90th birthday of Arthur C. Clarke the prolific science and science fiction writer. Google the name and you’ll find out all about him. I remember him before 2001 a Space Odyssey, with his books Childhood’s End and City and the Stars. He proposed geostationary communication satellites way back in the 40s. You can find his 90th birthday reflections on YouTube at http://www.youtube.com/watch?v=eLXQ7rNgWwg
Mars in Northern Michigan Skies
The below zero temperatures of last night as usual brought out the stars I am out looking through my telescope. I sometimes wonder what I find so intriguing about this hobby. Then I looked at Mars and I remembered right away. Seeing was 3/5 or around average so Mars was showing some details at around 270X. The polar cap was visible right away, with some dark features on the planets globe showing themselves. These dark features were a little more difficult to distinguish. After some time I determined it must have been Mare Acidalium, meaning I was looking at the area of Mars where the Pathfinder, Viking One, and the
The Geminid meteor shower December 14th.
The great meteor shower of December, the Geminids, will reach its peak Friday morning the 14th. On the evening of the 13th the 4 day old moon will set near 10 p.m. in Traverse City, which is a bit later than in most time zones. The time of the peak is 16:45 UT. That’s 11:45 a.m. EST. The shower is called the Geminids because they seem to come from the constellation of Gemini the twins. Unlike most meteor showers which have their highest numbers just before dawn, the normal highest numbers of meteors, when the radiant point is highest in the sky is at 3 a.m. The radiant point is near the star Castor and this year, the planet Mars. The Geminids rival the Perseid shower of August for numbers of meteors. The International Meteor Organization estimates if the radiant was at the zenith at the peak of the shower, 120 meteors per hour may be seen.
The Geminids are caused by bits of rock that orbit the sun in a rather small but elongated orbit. The parent body of these, thought by some to be a dead comet was discovered in 1983 by the IRAS Infrared Astronomy Satellite and was given the name Phaethon, after the son of Apollo, who tried to drive his father’s sun chariot. Phaethon comes very close to the sun at only 13 million miles, less than half Mercury’s average distance.