TRAC Action Plan: December 2024

Winter Constellations

Winter Arrives

Winter officially begins on 21 Dec 2024, the date of the winter solstice. This is the shortest day of the year, with the longest night in the northern hemisphere.

December and January are the best months for stargazing in the northern hemisphere. The days are shorter, giving us more time to enjoy the night sky. The sky also gets much darker because at midnight, the Sun is the furthest it gets below the northern horizon.

The Winter Sky

By December, many of the most iconic winter constellations are high enough by 22:00 for us to see. We'll focus on these prominent ones:

• Auriga – The Charioteer
  Contains the bright star Capella. The asteroid Eunomia is currently in the middle of Auriga's pentagon.
• Cancer – The Crab
  Home of the Beehive Cluster (M44). The main stars in Cancer are relatively faint, ranging from mag. +3.7 to mag. +5.2.
• Canis Major – The Greater Dog
  Contains Sirius, the brightest star in the sky. The constellation resembles a dog. We might only be able to see the dog's head and body; its tail will be too low until the early hours of the morning.
• Canis Minor – The Lesser Dog
  Contains the bright star Procyon. It's depicted as two stars joined by a line, so, unlike Canis Major, it doesn't look anything like a dog!
• Gemini – The Twins
  Contains the two bright stars Castor and Pollux. Gemini looks like two people with long legs with their arms outreached holding hands. December's Geminid meteor shower appears to radiate from Gemini, hence the name.
• Orion – The Hunter
  Famous for the Orion Nebula and the asterism known as Orion's belt made up of three bright neighbouring stars in a row. We'll also see Betelgeuse, a red supergiant, and Rigel, a blue supergiant.
• Taurus – The Bull
  Home of the Pleiades and Hyades open clusters, and the bright orange star Aldebaran. Jupiter and Uranus are currently located in Taurus.

That looks like a lot of work! But on a clear night, there's no reason why we shouldn't be able to see all of these constellations in one epic stargazing marathon. I know TRAC members will rise to the challenge!

We'll be taking a closer inspection of many of these areas of sky when we look for several deep sky objects (DSO) such as the famous Beehive Cluster (M44) in Gemini and the stunning Orion Nebula.

Sirius: The Brightest Star in the Sky

Some of your friends and family might think that Polaris (The North Star / Pole Star) is the brightest star in the star, but you can correct them! The brightest star visible in the night sky is actually Sirius. At magnitude -1.46, it stands out a mile!

Sirius often appears to twinkle and flash bright colours, including white, blue, and even red. I once mistook it for a plane! The flashing and twinkling are caused by atmospheric dispersion. Astronomers call this phenomenon "atmospheric scintillation", and it's the result of light passing through varying air density and temperature layers in Earth's atmosphere.

Scintillation is more noticeable in bright stars like Sirius, especially when they are closer to the horizon, as their light travels through more of the atmosphere compared to stars overhead.

The Winter Triangle

Draw three imaginary lines to connect the three bright stars Sirius, Betelgeuse, and Procyon. What do you get? That's right; a large equilateral triangle. Astronomers call this asterism "The Winter Triangle".

The Winter Triangle is easy to spot. It's high up in the sky for most of the night during the winter months. It can be used as a guide when finding other constellations.

(*) The apparent magnitude of Betelgeuse varies between +0.0 and +1.6. The value +0.50 is typical.

The Winter Hexagon

Ready to take these polygonal asterisms to the next level? I thought so!

The six bright stars, Capella, Aldebaran, Rigel, Sirius, Procyon, and Pollux, form a large hexagon in the winter sky. Two stars (Sirius and Procyon) are in both the Winter Triangle and the Winter Hexagon.

Some mavericks include both bright stars in Gemini (Castor and Pollux) as vertices of the hexagon. But really that makes it a heptagon. Pollux (mag. +1.14) is slightly brighter than his twin, Castor (mag. +1.58). We'll leave Castor out of the picture. We don't want to upset the mathematicians.

Autumn Flashback

We'll also look for the autumn constellations listed in the November Action Plan that we weren't able to observe in their full splendour, namely Aquarius, Aries, Pisces, and Capricornus.

Open Star Clusters

Stars Bound By Gravity

An open star cluster is a collection of stars that formed together from the same giant molecular cloud, making them relatively young in cosmic terms.

These clusters typically contain hundreds to a few thousand stars that are loosely bound by gravity. Because of their weak gravitational binding, the stars in open clusters gradually drift apart over time, spreading out across space. This dispersal gives the clusters their "open" appearance and distinguishes them from globular clusters, which are much more tightly packed and contain significantly more stars.

Team TRAC will aim to see four of the most famous open clusters.

The Pleiades (M45)

Located 440 light years from Earth, the Pleiades (mag. +1.6) is one of the closest star clusters. It contains more than 1,000 stars. The light we see is mainly produced by young, hot, blue luminous stars.

To the unaided eye, most observers can make out six or seven stars. Those gifted with exceptional eyesight might be able to see up to 14 stars! Back in February, Krum counted 20 stars while looking through the telescope. We'll see if we can see even more than that. I think we stand a very good chance.

The Pleiades is also known as the "Seven Sisters". Due to its distinctiveness and naked-eye visibility, M45 has become a TRAC favourite.

The Hyades

There's a second star cluster in Taurus: the Hyades (mag. +0.5). It contains 10 stars that are magnitude +4 or brighter. It's located about 153 light-years from the Sun, making it our nearest open cluster.

The bright orange star Aldebaran (mag. +1.0) lies close to the Hyades but isn't part of the cluster – it's much closer to Earth along the same line of sight.

TRAC regular attendees have seen it many times while looking at Jupiter. I've called it a "play" symbol because the brighter stars form a triangle that resembles a play button (at least to me it does!).

As of December 2024, exoplanets have been discovered to orbit four stars in the Hyades!

The Beehive Cluster (M44)

Slap bang in the middle of Cancer lies M44, the Beehive Cluster (mag. +3.1), also known as Praesepe. It contains over 1,000 stars, and it's visible to the naked eye under dark skies. It's about 600 light years away, and its bright core is 23 light years wide.

We'll see how it appears in binoculars from Rainham.

Mars will be placed just a couple of degrees above the Beehive Cluster at the beginning of the month.

The Double Cluster

As its name suggests, the Double Cluster, NGC 869 (mag. +3.7) and NGC 884 (mag. +3.8), consists of two open star clusters. They are situated next to each other in the constellation Perseus, which borders Auriga and Taurus.

There are more than 300 blue-white supergiant stars in each of the clusters, which lie at a distance of around 7,500 light years from Earth.

Planets

All seven planets are visible this month.

TRAC Top Priority: See Uranus and Neptune!

Mercury

Mercury (mag. -0.2) reaches its greatest western elongation on 23 Dec. It can be seen in the morning sky, at about 07:30, around this date.

Mercury is always a tricky target. It will rise two hours before the Sun and will be roughly the same brightness as it was when we saw it on 24 Mar 2024.

Anyone awake early enough at Christmas will have a good opportunity to observe Mercury looking east from the park. Just remember, Mercury will disappear quickly after the Sun rises, so set your alarm to ensure you don't miss it!

Venus

Venus (mag. -4.0) is getting higher and brighter with each passing day as it approaches its greatest eastern elongation on 10 Jan 2025. By the end of December, it will set four hours after the Sun and reach mag. -4.3!

We'll observe Venus immediately after sunset while the sky is still light. We want to avoid seeing it against a dark background because the glare it produces is overwhelming.

We briefly saw the phase (68%) of Venus in November, and we'll give it another go and also see if it's possible to pick out some darker markings on the clouds of Venus. This is possible in a 60mm refractor, so the telescope ought to be able to do this.

Meteors that are brighter than magnitude -4 are called fireballs. When you see Venus, try to imagine how exciting it would be to see a meteor that bright streak across the sky! Maybe you'll see one next year!

Mars

Mars (mag. -0.5) will brighten to magnitude -1.2 by the end of December 2024 as it approaches opposition in January 2025.

It will be interesting to see if we're able to see any details on the red planet. The telescope should be capable of showing us the polar ice cap in the north, prominent markings on the surface, and perhaps even some white clouds in the Martian atmosphere. We just need the atmospheric conditions to be clear.

18 Dec 2024: The Moon will occult Mars (mag. -0.9) in the daytime (09:24-10:15).

06 Dec: Mars will switch from prograde to retrograde, so it will start to drift westward against the background stars. It's not actually stopping and changing direction; it just appears that way from Earth. Its movement around the Sun isn't changing. We'll cover more on this topic next year!

Jupiter

Jupiter (mag. -2.8) makes its closest approach to Earth on 06 Dec (612 million km away) and will reach opposition on 07 Dec. It'll be visible all night long – it doesn't get better than this!

We've yet to see Jupiter's Great Red Spot (GRS), so this will be something to look for. The GRS is continuing to shrink. Scientists aren't sure why and don't know what the end result will be. Some speculate it could eventually disappear, but no one knows for sure.

Jupiter GRS Transit Times - December 2024

14 Dec: The Moon will be close to Jupiter.

31 Dec: Jupiter, Aldebaran, Hyades, Pleiades - Potential phone photo op?

We'll also aim to observe a couple more Jovian moon shadow transits.

Saturn

Saturn (mag. +1.0) is still easily seen in Aquarius, but it now sets by 23:00.

There are two Titan shadow transits we could potentially observe this month. These shadow transits are worth trying to observe because we don't get to see them very often. There's a gap of 13 years where none can be seen!

Uranus

Uranus (mag. +5.6) is visible all night long just south-west of the Pleiades on the boundary between Taurus and Aries.

A few of us saw Uranus in November with binoculars. We'll employ the same strategy to locate it again and confirm our sighting with the telescope at higher magnification power.

Neptune

Neptune (mag. +7.9) will be positioned at a high altitude under peak darkness for most of the month, offering a prime opportunity for observation.

We haven't seen Neptune yet, not even with binoculars! It's located to the south-west of the Circlet asterism in Pisces. We'll use Stellarium to pinpoint its exact location before we go out to hunt it down.

We need a very clear night and probably access to the park. Let's hope we can finally track down the Solar System's most distant planet and fulfil our 2024 mission!

Moon Shadow Transits

Please refer back to last month's plan for more information about moon shadow transits.

We successfully observed an Io shadow transit in November, and this month we'll aim to witness both the moon and its shadow crossing the planet.

We'll need an exceptionally clear night to witness a Titan shadow transit since this will push the telescope to its absolute maximum limit.

The shadow cast by each moon will transit its planet at the following times:

Timings are in UT and may vary by a few minutes.

The Ganymede transit on 08 Dec will be particularly interesting because the moon and its shadow will almost be touching.

The Orion Nebula (M42)

We haven't had the chance to observe a nebula yet this year. Let's change that!

We didn't see the Ring Nebula (M57) (mag. +8.8) in October or November due to poor weather. If time allows, we'll give it another shot.

Our primary focus will be the beautiful Orion Nebula (M42) (mag. +4.0). This vast star-forming region stretches a staggering 24 light-years across and lies just south of the three bright belt stars in Orion. At 80 times the brightness of M57, the Orion Nebula is so luminous that it's visible to the naked eye.

The Orion Nebula is one of the most photographed objects in the night sky. I'm sure you've seen some spectacular images of it online and in astronomy guides. But no picture can beat seeing it for real, with your own eyes!

Geminid Meteor Shower

The Best Meteor Shower of 2024?

The Geminid meteor shower will be active from 04 Dec to 20 Dec. Under ideal conditions, it is known to produce up to 150 meteors per hour at its peak (14-15 Dec). Unfortunately, these dates coincide with the full moon this year.

The shower's radiant point is located in the constellation Gemini, hence the name "Geminids". Sometimes it's the best meteor shower of the year. We'll soon find out if that'll be the case for 2024.

Like all meteor showers, the Geminids will be best viewed from the park where we enjoy a wide view of the sky, well away from the street lights and bright flashing Christmas lights!

Bonus Meteor Shower

There's a second meteor shower in December: the Ursids. Its radiant point is in Ursa Minor, the Little Bear, home of the North Star, Polaris.

This year, the Ursids will be active between 17-26 Dec, with a peak on 23 Dec and a modest hourly rate of 10 meteors. While not as impressive as the Geminids, the Ursids are still worth looking out for when you're out observing the night sky.

Stay Vigilant

Seeing a meteor flash across the sky is always an exciting event.

Meteors can be seen on any night. You never know when you might see one, so it's a good idea to stay alert whenever we're outside on a clear night. Quite a few TRAC members have unexpectedly seen a meteor while stargazing, observing the planets, or just out for a late-night stroll.

The longer you spend outside on clear nights, the greater your chance of seeing a bright meteor – a sight you'll remember for the rest of your life!

Minor Planet Eunomia

We haven't managed to see an asteroid in 2024 due to poor weather conditions with 3 Juno in March and unfavourable timings with Ceres in July.

Asteroid 15 Eunomia (mag. +8.0) will reach opposition on 14 Dec in the constellation Auriga.

However, the timing isn't ideal – December's full Moon falls just one night later, on 15 Dec. And what's worse, the Moon will be positioned right next to Eunomia near the border of Auriga and Taurus.

Given this situation, we'll plan to look for Eunomia earlier or later in the month, but it won't be one of our top priorities. Observing Eunomia is arguably even harder than spotting Neptune. It's best for us to focus our attention on fulfilling our main objectives.

Lunar Observations

December 2024 Lunar Calendar

• New Moon Sun 01
• First Quarter Sun 08
• Full Moon Sun 15
• Last Quarter Sun 22
• New Moon Mon 30

We must hope for decent weather near the start and end of the month.

You'll notice that we have two new moons this month. This occurs because the lunar cycle (synodic month) is about 29.5 days long. This is slightly shorter than most calendar months (which are typically 30 or 31 days).

Moon-Planet Conjunctions

Conjunctions involving the Moon and a planet, though fairly common, always provide good photo opportunities. This month is packed with celestial close encounters. Here's what to look out for:

(*) We know the Pleiades (M45) isn't a planet, but it's included because we like it!

Bonus Photo Op: On Dec 17, at 21:00, the Moon will be placed below Castor and Pollux (Gemini) and above Mars in Cancer.

• Read more about conjunctions:
  What Is a Conjunction? (Time and Date)

Lunar Occultation of Mars

The Moon (mag. -12.5) will occult Mars (mag. -0.9) on the morning of 18 Dec 2024.

At 09:24, the Moon will pass directly in front of Mars, occulting the planet for around 50 minutes. The Red Planet will emerge at 10:15.

Both objects will be in the west at an altitude of 22 degrees at the start of the occultation. As long as the weather's good, it should be possible to view this event from the park looking WNW. The Moon will be very low on the horizon, so it's unlikely that we'll be able to see Mars reappear.

TRAC has never observed the Moon occult a planet and I've never seen Mars at this time of day, so this will be an experiment.

Christmas Time

TRAC Christmas Gathering

***TBC*** Perhaps we can meet up for a big astronomy club Christmas party. Let me know your ideas.

Reindeer in Rainham

Christmas Eve is the most magical time of the year. The usual laws of physics are temporarily suspended, and anything is possible!

On the night of 24 Dec, if you spot a faint red light blinking high in the sky, could it be Aldebaran, the fiery eye of Taurus, peeking through the clouds? Perhaps it's a plane cruising at high altitude – or just maybe, it's Rudolph leading the sleigh with his bright, shiny nose lighting the way!

I'm jealous of those guys; they must get a fantastic view of the stars from up above the clouds.

Let's TRAC(k) Santa

Did you know it's possible to track Santa as he delivers presents to children around the world? Every year on Christmas Eve, NORAD tracks Santa. Their usual job is to monitor the airspace over the US and Canada, but every year on 24 Dec, they also track a special visitor!

Using the latest satellite and laser technology, NORAD tracks Santa's flight around the world – and you can, too!

Junior TRAC members, and those who are young-at-heart, can see where Father Christmas is on Christmas Eve using the links below.

• Track Santa around the world on Christmas Eve:
  https://www.noradsanta.org/en/
• More about NORAD and why they track Santa:
  https://www.norad.mil/NORAD-Tracks-Santa/

NORAD has been tracking Santa every year since 1955. In 2024, TRAC members will track Santa – with a little help from NORAD!

Admin Tasks

Website Content

The website is beginning to look a bit more respectable.

We need to continue to add more photos and imagery to make it less "text heavy". We'll review all of the photos taken in November and October and add the best ones to the website.

I'm still working on building the password-protected "members only area".

Krum is going to help me create a page for Zak, our club mascot.

TRAC members have been sent an email titled "Astronomy Club Homework". Once everyone has completed this, we'll create our avatars and add our information to the "Meet the Team" page.

Remember: a website is never finished, it's always a work-in-progress.

Looking Ahead to 2025

With only 30 days left until the end of 2024, it will soon be time to start planning for 2025. Have a think about what you'd like to do at astronomy club next year.

• Which activities/projects did you enjoy most this year?
• What could be improved or extended?
• Which astronomical events are you most looking forward to in 2025?
• Are there any other aspects of astronomy would you like to explore?

We have a few budding astrophotographers in our ranks, so I think night sky photography is definitely an area that we'll investigate further in 2025.

I look forward to hearing about other ideas you come up with!

Summary

Top Priorities for December 2024

In descending order of importance:

1. Uranus
2. Neptune
3. The Orion Nebula (M42)
4. Jupiter's GRS
5. Moon Shadow Transits
6. Open Star Clusters
7. Moon-Planet Conjunctions
8. Eunomia

We'll also track Santa, identify the major winter constellations, while keeping our eyes peeled for some meteors. Hopefully, they'll be lots of opportunities to see some planets, moons, and stars for those willing to brave the chilly December nights!

December Astrophotography

The numerous Moon-Planet conjunctions should provide some opportunities for you to practice your photography skills. And the shadow transits will push your phone's camera to its limit!

2024 Mission Update

We desperately need to see Uranus and Neptune. That's our core mission. Anything we do beyond that will be a bonus. We must stay focussed and make the most of every clear night we get – because there might not be many of them!

Only a few TRAC members have seen Venus and Mars. Everyone else will need to make sure they see them before time runs out!

Seeing Uranus and Neptune could be our big finale to end the year!

We need to redouble of efforts during these last four weeks of 2024.

You can check our progress here at any time.

TRAC Goes Paperless

That's right, our plans and reports are now only available online.

It's Christmas!

Merry Christmas to all our friends, families, and neighbours from everyone at the Taverners Road Astronomy Club! May your holiday season be filled with joy, wonder, and clear skies for stargazing!

James M
TRAC Team Leader
01 Dec 2024 – Rainham, Kent