It is hard to escape Jupiter this month. The giant planet is at opposition on November 3, opposite the Sun in the sky and thus visible all night long. Shining strongly among the faint stars of Aries, it is brilliant in the east after sunset.
Later in the night it is much higher in the sky, making it a treat for astrophotographers and those with telescopes of any size. Even binoculars will reveal the four bright moons discovered by Galileo in the early 17th century (he called them “Medicean stars” after his patrons and funders; we call them the Galilean moons). Their position changes relative to each other from night to night, and their mutual encounters, plus eclipses and transits, add interest to the scene.
The great Danish astronomer Ole Romer studied these events carefully. He noticed that eclipses of Io, the innermost moon, did not always have the same duration. Believing that it could not be the orbit of the moon which was changing, he realised that longer eclipses occurred when the Earth and Jupiter were moving away from each other. This was the first indication that the speed of light was not infinite, but took a noticeable period to cross any extra distance between the planets; his estimate of light speed was within 25 per cent of the modern value; pretty good going.
More recently, it is the belts, storms and clouds of the planet itself that attract attention. The ever-changing weather in the giant planet’s cloud decks is fascinating to watch, and new discoveries are still being made. Just in the last month, observations with the infrared James Webb Space Telescope showed winds in a high jet stream moving at more than 500km/h, twice the speed of those on Earth.
Stronger winds still are found in Saturn’s atmosphere, where speeds of more than 1,500km/h are not unheard of. Saturn itself is bright in the south after sunset, in Aquarius, with a conjunction with a first quarter Moon on the evening of November 20 a particularly attractive sight. With the naked eye, compare its colour to that of brighter Jupiter; the larger planet always appears a purer shade of white to me.
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In the morning sky, Venus is a beautiful and brilliant sight, rising more than four hours before the Sun as the month begins. On the morning of the 9th, the Moon passes in front of Venus in what is known as an occultation, beginning at about 9.45am (exact timings depend on exactly where you are).
That is, of course, well after the Sun has risen, so to protect your eyes extreme care will need to be taken if you are using binoculars to look for the pair. I would recommend positioning yourself so a building blocks the Sun, which is to the east of the pair, thus ensuring that you cannot accidentally look at it. Venus reappears about an hour later.
The Leonid meteor shower is active throughout the month, with a peak expected on the morning of November 18. The Leonids, associated with Comet Tempel-Tuttle, in normal years produce ten or so meteors an hour, but once every 33 years create a spectacular storm with many thousands a minute. The next such storm is due in the first few years of the 2030s, but the Leonids are still worth watching this year with the Moon out of the way.
As ever, make sure you give your eyes enough time to get dark-adapted when meteor spotting.
The stellar sky has a wintery aspect, with Orion now visible on our map. The celestial hunter’s belt points up to Aldebaran, the brightest star in the zodiacal constellation of Taurus. Aldebaran sits among the stars of a cluster called the Hyades, though is not a member of this, our nearest open cluster. It comprises hundreds of stars, most of which formed together about six hundred million years ago, just enough time for the most massive members of the cluster to be evolving into giant stars.
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As the cluster ages, the interaction between its members will cause it to evaporate, and perhaps a third of the stars seem to be in the process of escaping from it. Observers wishing to catch it at its best should point their binoculars in this direction sometime in the next few hundred million years.
Just above Taurus the winter Milky Way passes through Auriga, also home to a selection of bright clusters, before crossing Cassiopeia and then down to the northwestern horizon. Over in the north, the asterism of the Plough skirts the horizon at its lowest point in the annual cycle.
