The dark skies of West Norfolk

My apologies for the paucity of this December offering. January’s might be more expansive, like the Universe is, but will only be visible in Town and Around as the Heacham Newsletter will be in space dock for the holiday.

The 21^st Dec is the Winter Solstice when we have our shortest day and longest night. The times of sunrise and sunset depend on latitude and for Heacham / Hunstanton, sunrise will be around 8.16am and sunset 3.55pm. A day of 7hrs 39mins and, to save you the trouble of calculating, a night 16hrs 21mins long.

Winter Solstice. The northern hemisphere is in shade whilst the southern basks in more sunlight.

It’s all to do with the tilt of the Earth’s axis which makes the arc described by the Sun, as it moves across the sky, move South from around the 21^st June before it comes north again from the 21^st December. The sun is furthest south at 9.20am and dancing in the street, at that time, shouting, ‘Come back Sun’, will shorten the winter.

The planets: Venus gets ever brighter reaching magnitude -4.4 by the end of the month. It will be seen in the west until 8pm. No equipment needed so go out and take a look. On the 4^th the Crescent Moon will be just below and, on the 5^th, to the right.

Jupiter is visible all night long and bright. I even saw it in the cloudy skies of November. On the 6^th the gas giant is as close to the Earth it gets this year, a mere 612 million km away. The next day is true opposition when the Earth and Jupiter face each other across space. Consequently, Jupiter is at its brightest. Look with your eyes and with any optical instruments you have. Try and spot the close sparks of the 4 Galilean Moons and, in a telescope, Jupiter’s stripes. On the 14^th, the Full Moon is close to Jove. There are another 88 moons listed but you won’t see them.

Saturn and its rings of wonder doesn’t set until 11pm but is visible from teatime. At 5pm on the 7^th find Saturn just to the left, and up a bit, of the quarter Moon. Next night, same time, Saturn is just to the right of the Moon. Use an app to locate it other nights but it will always be well to the right of Jupiter, a yellow, dim, entity not like a star.

The red planet, Mars, is getting brighter as the month progresses, from magnitude -0.5 to magnitude -1.2. Once found it is hard to miss because it is red. It rises at 7pm and should be clear of most trees and roofs by 9pm. On the 17^th, find it just below the Moon.

The two stars above our satellite will be Pollux and Castor, the heavenly twins and part of Gemini. They are hardly identical twins though as Castor is a six-star system of blue-white and red dwarf components 51 light years away. Pollux is an orange red giant on its own and, at 34 light years distance, is the closest such star to our Sun.

Get up before dawn on Christmas Day to catch Mercury in the SE. Santa’s messenger rises at 6.15 am, 2 hours before the Sun. It will at its greatest western elongation, separation, from the Sun so able to be seen against a dark sky. A bright spark with a magnitude of - 0.3. On the 28^th it will be to the left of the Crescent Moon.

Don’t laugh but there is another meteor shower. Perhaps, this time, we will see it though, unfortunately, a Full Moon will likely blot out an otherwise clear sky. It is the Geminids which performs before midnight between the 4^th and 20^th, peaking on the night of the 14^th / 15^th. This shower is not cometary debris but bits of an asteroid, Phaethon. The particles of dust left by this are denser and move slower than those from comets and the meteor trails last a bit longer.

Phaethon hurrying along his orbit shown below. Internet

Phaethon is an oddity which has been much studied as it is rocky body which forms a tail as it approaches the Sun, just like a comet but it isn’t one. Recent studies using solar orbiters which watch the Sun have revealed that Phaethon’s tail is made mostly of Sodium gas, which is atoms of metallic sodium released by the Sun’s heat. If there is little dust in the tail then where do the associated meteors come from? The answer may be from a destructive event in Phaethon’s past and a future Japanese probe may confirm that.

When you are waiting for one, along comes another. Between the 17^th and 26^th, the Ursids shower arrives and peaks on the 23^rd. That’s why Santa wears a tin hat under his red hood.

Happy Christmas and do keep looking up.