A monthly look at astronomical events in the sky and on Earth
A Happy New Year to all our Readers!
Prospects for 2020
Well, here we go. Another year; another chance to see something you’ve never seen before, or just to re-acquaint yourself with old celestial friends.
So what can we look forward to in the sky this year?
Firstly, what about the sky immediately around and above our heads – the atmosphere? A Met Office analysis from three global temperature data sets (HadCRUT, NOAAGlobalTemp, GISTEMP) predicts that atmospheric warming will continue the upward trend set over the last 22 years, so 2020 may be the warmest yet. As we have come to learn by now, heat means instability, and instability results in more storms, floods, droughts, heatwaves, big freezes and a general increase in extreme conditions. The wildfires of 2019 can hardly have helped, with their double-whammy of sending billions of tons of CO2 into the atmosphere coupled with the loss of CO2-fixing flora. In fact CAMS has estimated that between 1st Jan 2019 and 30th Nov, nearly 7,000 megatons of CO2 have been released into the atmosphere by wildfires. If we don’t get to grips with climate change soon, it’ll be too late and Earth may reach a tipping point. Everyone needs to do their bit to act or persuade.
Moving now to the higher atmosphere (50 – 75 miles up), there are five favourable meteor showers, meaning that a bright Moon doesn’t coincide with any of the showers. There are the Quadrantids in early January, the Lyrids in April, the Perseids in August, the Orionids in October, and the Geminids in December. If meteors are your bag, 2020 is the year for you.
Not too far above those flaming meteors, in addition to ambitious plans by a number of countries and commercial organisations, we can probably expect Elon Musk’s SpaceX company to further develop its low earth orbit launch and rendezvous capability. At the very least, it’s hoping to use its Dragon capsule to carry two NASA astronauts to the ISS by spring. And its rival, Boeing is developing its reusable capsule, which will return America’s ability to launch people to low Earth orbit for the first time since the last space shuttle flight (STS-135) in 2011. Watch this space!
Back to SpaceX, we are reminded today that they intend to launch hundreds more Starlink satellites during 2020, with the potential to ruin viewing and/or time exposure photography of the night sky. It’s amazing that President and COO Gwynne Shotwell’s, “No one thought of this”, statement can be true but apparently it is. They are now going to coat some test satellites with a less reflective coating, but let me predict that they will come back to us and explain that the coating made the satellites heat up too much in the direct sunlight so the idea had to be dropped. We will see.
As for the Moon, nothing dramatic is going to happen. There are a couple of penumbral eclipses but all you’ll see is the Moon going slightly darker. They’ll be nothing to write home about.
Out into the solar system proper now. Firstly, the sun. According to NASA, the solar minimum (sunspot activity) occurred in 2019 and we may begin to see the odd sunspot in 2020, but it also predicts that this next cycle will be fairly inactive compared to previous ones. We shall see. Keep checking – safely of course! Oh yes, I almost forgot. For those who have deep pockets (£2,150 plus international flights), there’s a total solar eclipse in December lasting just over 2 minutes visible from Argentina and Chile.
There are no comets brighter than magnitude 8 predicted to appear this year.
I’m leaving the good news until last so let’s hear the not-so-good first. That is that the two most dramatic and easy-to-observe planets, Jupiter and Saturn, will not be favourable placed this year. They are both languishing in the deep southern hemisphere and from the UK will not gain a greater altitude than 14° or 15° at any time. They both reach opposition in July, Jupiter on the 14th and Saturn on the 20th. To ameliorate this, these two planets will participate in a number of conjunctions with the Moon, and on 21st December there will be a “great conjunction” when the two planets close to within 6 arc minutes of each other. Great conjunctions only happen about once every 20 years. This one in 2020 is the closest for over 200 years. There’s quite an interesting Wikipedia entry dealing with great conjunctions.
OK, now for the good news: the inner planets will put on a good show this year.
Firstly, Mercury has two favourable greatest eastern elongations (GEE), one in February and one in late May. This is when Mercury can be seen low in the west not long after sunset.
Next, Venus will reign supreme in the evening sky from the beginning of January right through to the end of May. It sets over 4 hours after the sun during the spring and reaches greatest brilliancy in late April when, at magnitude -4.7, if you know where to look and the sky is very clear, you should be able to spot it in the daytime.
And now for the best news: Mars will return. Mars comes to opposition roughly once every 780 days (its synodic period), but because Mars’ orbit is a fairly eccentric ellipse, the distance between us and Mars at opposition can be anything between 34 and 63 million miles. That’s quite a difference; Mars looks nearly twice a big at 34M than it does at 63M. The closest approaches happen when Mars is at or near its perihelion. So the best oppositions occur when Mars is there; it’s a no-brainer, right? Wrong! Unfortunately, the perihelion of Mars’ orbit is at a point on the ecliptic (in Aquarius), where the ecliptic is 12 degrees south of the celestial equator. Further, Mars’ orbit is about 4° below the ecliptic at that point. The result is that at perihelic oppositions, Mars only climbs to 20° above the horizon. That puts it into the murk and noticeably degrades our view of it. So, what to do? The answer is to take advantage of oppositions when Mars is much higher in the sky, but not so high that its orbit has taken it too much further away. The “happy medium” between these two conflicting requirements is when an opposition occurs when Mars is in Pisces. For such events, it rises to over 40° above the horizon from the UK – well out of the murk – and its apparent size is only about 13% less than the size for perihelic oppositions. Such an opposition will occur in October this year. This is going to be the best opposition for the next 15-17 years, so do please make the most of it. Try to begin your observations by mid September (Mars’ diameter 20 arc seconds) and continue through opposition on the 13th October (diameter over 22 arc seconds) to the first week in November, by which time the Earth will overtake Mars and its diameter will reduce quickly to below 20 arc seconds again. By the beginning of December, the red planet will be only 14 arc seconds across and difficult to observe.
The nakedeyeplanets.com web site has an excellent and well-illustrated overview of Martian oppositions and is well worth a read.
I think that’s it. An interesting astronomical year in prospect. Let’s hope the weather is kind.
What to see in January
Best seen as a waxing crescent in the west from the beginning of the month, through first quarter on the 3rd to gibbous high in the south on the 7th.
May be glimpsed low in the SW after sunset at the end of the month, but best to wait until early February.
On 1st January, Venus will be at 16° altitude in the SSW at sunset and at magnitude -4.0 will be easy to spot shortly after that. By the 31st, its altitude will have risen to 27° at sunset, the planet itself not setting until nearly four hours later. Through a telescope, Venus will look like a very bright gibbous moon about 15 arc seconds in diameter. As we’ll be looking only at cloud tops, its surface will be featureless. It’s worth noting its phase, which will change towards “half moon” then crescent as the year progresses. It will also get larger, ending up at a massive 56 arc seconds by the end of May.
Mars, Jupiter and Saturn
Mars is only visible low in the SSE in the morning sky and it’s only 5 arc seconds in diameter. Wait until nearer its opposition in October.
Both Jupiter and Saturn are too close to the sun to be observable in January.
Uranus is conveniently placed for observation in January. It’s due south and at its highest point in the early evening. At magnitude 5.8 and with an angular diameter of 3.6 arc seconds, it can be seen as a disc in most good quality telescopes. Please see November 2019’s What’s Up for more information and a finder chart.
Neptune is now too close to the Sun to observe. It reaches opposition in September.
Quadrantids Meteor Shower
This shower peaks on the morning of 4 January lasting less than a day. The International Meteor Association predicts the peak to be at 0800 UT on the 4th when from northern latitudes, 15-25 meteors per hour are expected. The radiant is near the end star of the Big Dipper’s handle, and the best time will be in the hours before sunrise, 0530 – 0630 being the very best. Look anywhere high to the south and with no Moon to lighten the background you should be rewarded.
These are best seen when the Moon is out of the way, and that’s in the entire second half of the month.
If you haven’t paid them a visit this winter, then the four objects listed in December’s What’s Up (M31, M33, The Double Cluster in Perseus, and the Pleiades) are worthy of your attention.
(Looking south at 10 pm on the 1st, 9 pm on the 15th, and 8 pm on the 31st)
It’s also worth having a look at the Hyades open cluster. This is the nearest open cluster to us and contains hundreds of stars that form the head of the bull in Taurus. Alpha Tauri (Aldebaran) is the red giant “eye of the bull” but is not in fact part of the cluster. The only way to do the cluster justice is to view it using binoculars as it is 5.5° in diameter.
But the star attraction for January and February must be the constellation of Orion. Why the constellation and not M42, the Great Nebula in Orion? Because the constellation is peppered with deep sky splendours which tend to be upstaged by the Great Nebula.
What I’ll say about M42 is if you haven’t seen it yet, you’ve missed the most spectacular deep sky object in the entire sky. It’s twice the apparent diameter of the full Moon so start with a wide field low power eyepiece and spend a goodly length of time with that before upping the magnification. Do this in easy steps and use averted vision to detect the subtle but complex filamentous structure. I also recommend you read the entire Wikipedia entry on M42; there are lots of links in there and an excellent image gallery.
Regarding Orion’s family of deep sky objects, just read this Sky & Telescope article to be convinced that “Orion” is not just its Great Nebula. The article will guide you through the constellation and includes a photo-map of the rich area round the “sword of the hunter”. Do give it a go.
Passes of the International Space Station (ISS)
The ISS is visible every night up to and including the 9th, then again from the 22nd to the end of the month. See the Heavens-Above web site for more details. Here is a link with all fields relevant to York selected.
For up-to-date news on space missions, rocket launches etc. scroll https://www.space.com/32286-space-calendar.html
Clear skies and good viewing.
John Rowland 27 December 2019