The Night Sky - December 2025
Two of the naked eye visible planets will be lost in twilight by mid month, both Mercury (low in the SE in the evening) and Venus (very low in the ENE in the morning). Mars is still in solar conjunction, which means it is on the far side of the sun from us. Jupiter will rise in the NE before 7 PM, transits (crosses the mid line) about 2 AM and will be low in the W by dawn. It takes Jupiter about one Earth year to pass through a zodiacal constellation. It takes 12 of our years for Jupiter to complete it’s orbit. This year it is in Gemini.
Saturn is further away from us than Jupiter, so it’s orbit around the sun takes almost 30 years. l During that time, both Earth and Saturn change the angles from which they are seen. So things like the rings can appear to be like a doughnut around a hole, or flat like a DVD. Right now Saturn’s rings are almost flat (-0.76* on the 25th). Saturn will be high in the S at dusk, transit before 7 PM and set in the W around midnight.
The tides will be King Tides the first week of December. This means the Sun, Earth and Moon align in a configuration called syzygy This often happens when there is a full Moon in the first week of December. And this month that happens on December 4 (Rivers Freezing Over) and the Moon is at perigee (it’s closest approach to Earth). The Moon passed just N of the Pleiades on the 3rd.
December 7 has Jupiter just S of the Moon and Mercury is its furthest from the Sun. On the 10th, Neptune will appear stationary and the Moon will occult Regulus at 2 AM. Regulus is the bright star at the end of the backward question mark in the constellation Leo. This is something you can easily see with just your eyes, Last quarter Moon is on the 11th and the Geminid Meteor shower on the 13th. Remember, to best watch a meteor shower, look away from the Radiant (where the meteors appear to be coming from). So, look away from Jupiter this year. On the 17th, the Moon will be at apogee (it’s furthest away point) and the New Moon will be on the 19th. The Ursid Meteor shower (radiant in Ursa Minor near the pointer stars) is on the 21 as is Winter Solstice.
Winter Solstice is when the sun appears to rise in the same place for about three days. In the Norther Hemisphere it means we have the fewest hours of sunlight visible to us. Earth is physically closer to the sun, but in the Northern Hemisphere we are tilted away so we don’t get warm.
The first quarter Moon will be on the 27th with Saturn and Neptune (not naked eye visible) near the Moon. On the 31st the Moon will be just N or the Pleiades.
There are lot’s of things that change in the night sky. The. Planets are always in a different position and you may be able to see Moons, rings or storms on some of those. Our Moon shows the mountains, craters and plateaus at the Terminator — the line between light and dark. With a small telescope you can see seasons on Mars. Binoculars will show the inner planets going through the same phases as the Moon. Space is a vibrant place and even stars change.
Variable stars are another area where Amateur Astronomers contribute to science. The AAVSO (American Amateur Variable Star Observers) collects information about a star’s magnitude. This data base is available for Professionals and others to access. As our Sun is a star, the more we know about how they work, the better.
There are some variable stars that are naked eye visible. Algol is one of these. It is at the hip of Perseus, which will be high in the sky most of December nights. And it is possible to see it change brightness in one night. It brightens after a 10 hour period of eclipse. The star is part of the three star grouping. The centre two stars are what causes the dip in brightness. The third star’s effect is not naked eye. The rest of the time the star maintains the same magnitude. The period is almost three days. No wonder this was designated a Demon’s eye!
Another naked eye variable is Betelgeuse. This is the red giant star that forms the right shoulder of Orion. This young star is already dying and is expected to Super Nova when its time is up.
Clear skies.
