A monthly look at astronomical events in the sky and on Earth
Compiled by John Rowland
A Happy New Year to all our Readers!
Prospects for 2021
Well, I hardly dare say, “What a year!” but it’s unavoidable. Thankfully, however, we enter 2021 with hope in our hearts that after such a long time, we can again get together with friends to gaze upwards, wonder, and share in the splendour of the night sky. After all, the cycles of the heavens know nothing of nor care about the trillions of microscopic organisms against which we, on this precious and exquisitely beautiful planet, are battling. Hopefully, this battle will soon be won, and we can turn our attention from microscopes to telescopes and say, “What’s Up?”.
So, what is up? What can we look forward to in the sky in 2021? Before I answer that, I want to tell you what we’ve been doing down here on Earth to improve what we’re going to look up with. 2020 was not a wasted year for the YAS. Society members have worked hard to improve the observatory and its facilities. We now have an operational multi-function room, remote cameras on telescopes on the roof and observing deck, and image feeds down into the warmth and comfort of that room. Telescopes can be remotely controlled from below, and there is also a facility for visitors to mount their own cameras “piggy-back” on one of the large telescopes and take automatically tracked time exposure pictures of deep-sky objects. The short video on the home page of this web site gives a brief overview of the observatory and its facilities. We have never had such cutting edge technology, so 2021 should be an amazing year for members and visitors alike.
The Year at View
Our star’s 11-year cycle (sunspot activity) passed through its minimum in late 2020 so now, we are beginning cycle number 25. Hopefully, therefore, we will be starting to see a few sunspots this year. The maximum won’t be until 2025 – see the NOAA graph below – but it should be worth keeping an eye open and checking sites such as Space Weather website which has a lot of interesting stuff on it related directly or indirectly to our star’s activity or our own Met Office website.
As always, the Moon is our most reliable observing target and never fails to impress. There’s nothing special happening related to the Moon this year. The best and most convenient times to observe it are when it’s between 3 and about 18 days old, when it’s in the sky in the evening and illuminated from the side rather than face-on (when there are few if any shadows to bring its features into sharp relief). The best months of all are February to April.
The Inner Planets – Mercury, Venus and Mars
(Also Known As Terrestrial Planet)
There are two periods when elusive Mercury may be seen in the evening sky: mid-January and mid-May. Neither apparition is particularly favourable when compared to ones that occur in March. See later in this article for details of the January apparition.
This year, Venus spends the first quarter of the year as a morning object and can only be seen before sunrise. From April to the end of the year it slowly emerges from behind the Sun and into the evening sky, but unfortunately, due to the orientation of the ecliptic during that time, Venus will be very low in the sky, climbing to only 7° in October. To be brutally honest, this is probably the worst year to see Venus. Sorry!
After last years’ most favourable opposition, Mars remains an easy object to spot in the evening right through to June. It is however not easy to observe through a telescope as it is so small. The Earth is moving away from Mars now and its angular diameter in January is 10 arc seconds, reducing to only 4 arc seconds by June. Best catch it soon and try to get access to a large telescope to have any chance of seeing any surface markings.
The Outer Planets – Jupiter, Saturn, Uranus and Neptune
Of all the planets, Jupiter will be 2021’s star performer. Up until August, It will be impossible or inconvenient to observe it but it reaches opposition on August 20th, when it will be at over 20° high in the south at midnight. It can then be seen in the evening right through to the end of the year. We will publish more information on observing Jupiter and its satellites nearer the time.
The beautiful planet with the rings will be in the same area of sky as Jupiter this year. Saturn reaches opposition on the 2nd August so like Jupiter, will be inconvenient to observe until then. It won’t climb so high in the sky as its larger neighbour and will look smaller in a telescope and suffer more from poor atmospheric “seeing”. But the rings will be well seen as they are tilted at quite a large angle from our line of sight. The best month for Saturn will be October but it’s visible through to November and beyond.
This naked eye (just!) planet is perfectly placed for observation throughout January and into mid-February. After that, forget it until November. See later in this article for a finder chart and a pointer to its conjunction with Mars and the Moon on 21st January.
Even a small telescope will allow you to see Neptune but you’ll need a guide chart to find it. You might just catch it in January but if not, wait until its opposition in September, and it can then be well seen through to December.
There are no solar or lunar eclipses of any significance visible from the British Isles this year. The only eclipse visible at all is an annular eclipse of the Sun on June 10th visible from the arctic. On that day, the UK will see a partial eclipse where less than 25% of the sun’s disc will be covered. See 10 June 2021 – Annular Solar Eclipse for details and timings. We’ll mention it again in June What’s Up.
Each year, there are six major meteor showers. Whether they can be favourably seen depends to a critical extent on the position and phase of the Moon at the time of the shower. If the Moon is full or in any phase up to 5-6 days either side of full, and in the sky at the same time the meteors are due, its light will flood the background sky and render all but the brightest meteors invisible. 2021 is not exactly the best year for meteors, with one major exception. Here is a list of the main showers in 2021 and their prospects.
Night of January 2nd/3rd. Very unfavourable due to nearly full moon. Quadrantid meteors, though numerous, tend to be fainter than most showers.
A few days either side of the peak on April 22nd/23rd. Unfavourable as waxing gibbous moon in the sky until first light.
A few days either side of the peak on August 12/13th. Extremely favourable, as no moon. By far the best chance to spot meteors this year. Expect to see up to 100 per hour between midnight and 3 a.m. The 13th is a Friday, so it’s worth organising a meteor watch party/barbecue for that evening.
Around October 21st. Very unfavourable due to full moon corresponding with meteor peak date.
Around November 17th. Very unfavourable due to nearly full moon.
Around December 13/14th. Unfavourable until moonset at about 3 a.m. then good. Expect to see up to 60 bright meteors per hour.
There are no comets visible to the naked eye predicted for 2021. There are however three comets that will be visible in telescopes (or even binoculars under favourable conditions), and finder charts will be published nearer the time. (May, September and November)
Man’s Space Activities
Spotting the International Space Station (ISS)
The ISS will be visible on numerous occasions during the year. The Heavens Above website gives details for the very date it can be seen. The link above is preset to return the data for sightings from York.
General Space News
There’s always something of interest going on in space. See the space.com website for the latest news. And for a detailed timetable of projected launches and other space-related activities, the Wikipedia website is an excellent place to start as it has links to each project/mission mentioned.
Note particularly that the James Webb Space Telescope (JWST) is due to be launched in October. This enormous telescope is a marvel of engineering as well as being the largest telescope by far to be positioned at the Sun-Earth Lagrange 2 point, nearly a million miles from Earth.
Space Day is an occasion where space-related activities and resources for children are presented. This year it’s on Friday, May 7th. See the Space Day website for more information.
That ends the Year at View. Now for recommended viewing for the month each What’s Up? is published. For each month, we aim to highlight the objects that are conveniently placed for viewing in the four-hour evening slot of 19:00 – 23:00 hrs unless there’s a good reason to view earlier or later.
Mercury’s greatest eastern elongation (GEE)
As the inner planets (Mercury and Venus) travel around the Sun, when seen from Earth they appear to wander to and fro, left and right of the Sun. The point at which they are the furthest left – or east – is called the greatest eastern elongation. It is at this point that they are furthest from the glow of the Sun and highest above the horizon once the Sun sets. Venus can reach up to 47° away from the Sun at its GEE, but Mercury’s angular separation can never be more than 28° and can be as little as 19°. So observing Mercury at or near its GEE is the only time it can be seen. The best possible circumstance is when GEE occurs in March, but any GEE between late January and May is worth our attention. Mercury reaches GEE on the 24th so you should give it a go any time within a few days either side of the 24th.
The diagrams below show firstly the position of Mercury at sunset (1628), then at 1700 on the 24th. Find somewhere that gives you a clear view right down to near the SW horizon, then at 1628 note where along the horizon the Sun sets, then wait until 1700 and look about 10° above the horizon and about 5° to the left of where the Sun set, and you should spot that elusive planet.
Beware: Do not look for Mercury using binoculars until the Sun has completely disappeared. Even a low red sun in binoculars can permanently damage your eyesight.
Mercury at sunset and then at 17:00 hrs on January 24th (from SkyViewCafe.com)
As explained above, Earth is leaving Mars behind now, so this month is your best opportunity to see the red planet. It’s due south (transits) and high in the sky at 1900 on January 1st. You can’t miss it. By the end of the month, it transits at 1800 and will have reduced in magnitude and diameter from -0.2 and 10.3” (arc seconds) to 0.4 and 7.9” respectively.
On January 20th, Mars passes only 1.5° to the north of magnitude 5.8 Uranus. This is an ideal opportunity to easily find and observe that planet. The Moon happens to be at first quarter on that date and is quite nearby in the sky. See the chart below. The Moon is even nearer (but to the SE of the planetary pair on the 21st).
Looking South at 18:00 on January 20th (From SkyViewCafe.com)
The best evenings to observe the Moon are from the 15th (slender crescent) through to the 24th (mid-gibbous). For those wishing to spot the earliest crescent moon, the best time will be at about 16:50 on the 14th. (See the Crescent Moon Watch page for more details.)
Deep Sky Objects
January and February are without question the two months that present us with the richest, most diverse and spectacular objects to observe. These objects (and in particular the nebulae) are best seen against a dark and moonless sky so try to observe them during the 4th – 21st window. The diagram below shows the full sky at 21:00 on the 15th.
Whole sky January 15th at 21:00 (from SkyViewCafe.com)
There are too many objects to describe each one in detail in this article, so I have compiled a list with hyperlinks that you may care to follow if you want more information and/or finder charts.
M31 – The Great Nebula in Andromeda
Not a nebula actually, but a galaxy; our nearest and sister galaxy. Visible very clearly in binoculars and awesome in any telescope with a “fast” focal ratio such as f/5. Use a low power eyepiece to see it, as it’s at least twice the angular diameter of the Moon.
NGC869/884 – The Double Cluster in Perseus
Often referred to as the Sword Handle, this famous pair of star clusters is a beautiful sight. Like the Andromeda galaxy, you’ll need binoculars or a low power eyepiece in a telescope to get both clusters in the same field of view.
M45 – The Pleiades
Otherwise known as the Seven Sisters, this is one of the nearest open clusters in the sky and the one most people who are not familiar with the night sky have seen because it is so noticeable. It contains many hundreds of hot blue stars, seven of which are clearly visible to the naked eye of a person with excellent vision. Binoculars give the best view, as the cluster is nearly two degrees in diameter (four times the apparent diameter of the Moon). You will not need a finder chart to locate it.
M42 – The Orion Nebula
This true gaseous nebula is without doubt the most famous deep-sky object in the heavens. It is twice the angular diameter of the Moon and with even the simplest optical aid, reveals an intricate and colourful structure. Start with a low magnification and work slowly up, and at every stage more of its beauty will be revealed. For this object, it really is vitally important that you observe it against a dark, moon-free and non light-polluted sky.
I recommend you read this Sky & Telescope article, which includes a finder chart.
M1 – The Crab Nebula
This final viewing recommendation is another famous object. It is the remnants of a supernova explosion recorded by the Chinese in 1054. At magnitude 8.4 it is not visible to the naked eye and very small compared with the other objects listed above but I’ve included it as a bit of a challenge. You may just spot it in rock-steady 10 or 12 x 50 binoculars, but if you have a telescope, use it and home in on it with a medium-to-high magnification eyepiece. It’s at the south-eastern corner of Taurus. Use the finder chart below and use your mouse to zoom in and out. But before you observe it, just consider these amazing facts about the Crab and the 16th magnitude star at its centre.
- The star is a spinning neutron star about 12 miles in diameter rotating at 1800 RPM. Yes, that’s 30 times per second. Just imagine something that big rotating so quickly!
- Such rotating neutron stars are called pulsars. You can hear the pulsing radiation converted into sound in this youtube recording.
- The Crab pulsar is so dense that a coffee cup full of its material would weigh 25 thousand million tonnes, the same as a rock cube with side lengths of over 2 km.
Hopefully, if and when you spot the nebula surrounding this apparently diminutive star, you can think about what a truly exotic and mind-boggling object it is.
I wish you clear skies and good viewing. Stay safe!