Northern Hemisphere
Ian Morison tells us what we can see in the night sky above the world's middle line during Month 4 2020.
The Planets
- As April begins, Jupiter rises some three and a half hours before the Sun shining at magnitude -2.1. It then follows Mars and precedes Saturn, just above Mars, into the pre-dawn sky. During the month it brightens to magnitude -2.3 whilst its angular size increases from 37.0 to 40.6 arc seconds. A low south-eastern horizon will be needed and our views of the giant planet and its Galilean moons will be somewhat hindered by the depth of atmosphere through which it will be observed.
- As April begins, Saturn rises at 05:33 UT, 20 minutes after Jupiter, and by its end at 02:50 UT whilst its magnitude increases slightly from +0.7 to +0.6 whilst its angular size increases from 16.1 to 16.9 arc seconds. Saturn reaches ‘quadrature', 90 degrees in angle from the Sun, on April 21st enhancing the three-dimensionality of its globe and rings. At 21 degrees, the rings are slightly less tilted to the line of sight than they have been for some time. Sadly, its low elevation before sunrise will somewhat limit our views of this most beautiful planet.
- Mercury is lost in the Sun's glare this month, so cannot be observed.
- Mars can be seen towards the southeast in the pre-dawn sky at the start of the month. It then rises at ~04:48am and will be best seen at around 6am having an elevation of ~8 degrees. It will then have a magnitude of +0.78 and a 6.4 arc second, salmon-pink, disk and lies just inside Capricornus. By month's end it will have moved over to the east of Capricornus and its magnitude will have increased to +0.43 and it angular size to 7.6 arc seconds. Having started the month just below Saturn, it rapidly leaves Saturn and Jupiter as it crosses Capricornus.
- Venus is still dominating the south-western twilight sky. It reached greatest elongation east from the Sun on the 24th March but is still near its highest possible altitude and April is still one of the very best months to observe it in its 8 year cycle of apparitions. As April begins, it will then have an elevation of ~39 degrees at sunset - about the highest elevation it can ever achieve! During the month its angular size increases from 25.5 to 38.2 arc seconds but, at the same time, it phase (the percentage of the disk illuminated) decreases from 47% to 26% and so the brightness only increases slightly from -4.5 to -4.7 magnitudes. This is about the brightest that Venus ever gets!
Highlights of the Month
- April 1st - before dawn: Jupiter, Saturn and Mars. Before dawn on the first of the month, Mars will be seen to lie just below Saturn with Jupiter over to their right.
- April 3rd - evening: Venus within the Pleiades Cluster. After sunset on the 3rd of April, if clear, Venus will be seen to lie just to the left of Merope within the Pleiades Cluster. A great photographic opportunity!
- April 15th - before dawn: the Moon joins three planets. Before dawn on the 15th of April, the Moon, just after third quarter, lies below a lineup of Mars, Saturn and Jupiter.
- April 25th - after sunset: A very thin crescent Moon lies between the Hyades and Pleiades Clusters. If clear after sunset on the 25th of the month, a very thin crescent moon will be seen to lie between the Hyades and Pleiades Clusters in Taurus. It may be possible to spot the 'Old Moon in the New Moon's arms' due to earthshine. Binoculars may well be needed, but please do not use them until after the Sun has set.
Haritina Mogosanu and Samuel Leske from the Carter Science Centre in New Zealand speaks about the night sky below the world's middle lineduring Month 4 2020.
In these very strange times, as we find ourselves locked inside our homes, we might have some ideas as to what to do with the April night sky. Hopefully you’ll be able to actually get out of your house and take your telescope somewhere else to have a look at the night sky.April is a month of action in astronomy and stargazing! Global Astronomy Month (GAM) is organised each April by Astronomers Without Borders and the International Dark Sky Week is also in April, this year from Sunday, April 19 until Sunday, April 26!
Planets- Look for Venus in the evening sky, where it is shining very bright. You can try to see it during daytime if your eyesight is good and you know exactly where to look.
- Look for Jupiter after midnight at the beginning of the month, and after 10:30 PM towards the end of it - thanks to daylight saving as well as Earth’s revolution around the Sun that among other things makes stars rise 4 minutes earlier every day. Try to spot Saturn and Mars about half an hour after Jupiter.
- Morning Owls can still enjoy Mercury as well as a beautiful arch of planets stretching across the sky and are welcome to tell us if it is worth waking up that early to see them. Sadly Mercury will disappear in the twilight of the rising Sun at the end of the month.
Stars
- Try to see the brightest stars in the sky - now is the time (as it was last month but we can still enjoy these in April). They are Sirius, the dog star, Canopus the cat star and Alpha Centauri, our closest neighbour 41.3 trillion kilometres away (so in the safe zone). Although, technically Sirius and Alpha Centauri are double stars, so then are they the three brightest stars or the five brightest stars?
Galaxies
- Milky Way - the obvious choice is brightest towards Crux. The centre of the galaxy rises around 10PM. In it, Scorpius is now here called Manaia ki Te Rangi, the guardian of the sky, and if you're into jewelry, you’ll see that it looks like a manaia made of green stone - pounamu. It’s a beautiful name for Scorpius and is great that the asterism can look like so many things, including a scorpion - which here in New Zealand don’t exist.
- Other visible galaxies are the Magellanic Clouds. Look for these in the Southern part of the sky, obviously, the part that we call circumpolar from here as the stars there never set and never rise but move around the celestial south pole in circles. Usually any star above declination -60 classifies as circumpolar from here.
- There are a whole bunch of amazing galaxies around Leo at this time of year. For our northern hemisphere listeners, Leo in the southern hemisphere is upside down from what you’re used to. The most amazing of the group of galaxies is the Leo triplet, which is M66, M65 and NGC 3628, and it’s really amazing to see three of them in the eyepiece. If you’ve got a big enough telescope, you can always go a little better, up the sky to NGC 3593 and then a little bit further away to NGC 3596 which are two nice galaxies too. Also a little bit above Leo, there’s another bunch of galaxies, Messier objects M95, M96, and M105, and in fact round M105 there’s another couple of galaxies, NGC 3389 and NGC 3384 - they’re all quite easy to see. If you’ve got a big telescope, you can also have a look for four other galaxies that are closer to Leo than the three I just mentioned: NGC 3338, NGC 3367, NGC 3377 and NGC 3412. They are all pretty easy to find as well. NGC 3367, if you can catch that one, is a hundred and fifty million light years away, which is staggering.
- Closer to the horizon, there’s all the galaxies that are around Virgo. They’re probably still a bit low for us, but by April if we stay up late enough there will be a beautiful bunch of galaxies to have a look through. That’s one of the great groups of galaxies that we share with the northern sky.
- Also, one of the classics for us is the Sombrero Galaxy, absolutely magic to look through on the telescope. Then, there’s M83, which is the big spiral that we see down here in the southern hemisphere. There’s Centaurus A, also known as the Hamburger Galaxy, and there’s another great galaxy that we quite like looking at as well - it’s NGC 4945, which is just above Omega Centauri, between Omega Centauri and the Southern Cross.
Binocular objects
- Omega Centauri is a nice big globular cluster, really easy to see and you can totally spot that.
- Now, if you’ve got a nice dark sky you’ll also be able to see M83 pretty easily in binoculars, so that’s definitely worth checking out. There’s not many galaxies you can see in binoculars, but M83 is one of them, and in summer you can see Sculptor, so now we’re sort of getting into the colder months M83 dominates.
- Then there are the larger clusters, the Southern Pleiades you can look at, which is pretty amazing in the binoculars. Omicron Valorum is high in the sky, as is NGC 2516, the Southern Beehive, and of course if you’re looking at the Southern Beehive you probably also want to look at the other Beehive, M44 in Cancer, which is also an absolutely wonderful binocular object as well. M42, the Eta Carina nebula is always great, and the Wishing Well cluster stands out really well in binoculars as well. 47 Tucanae is the other really nice globular cluster to have a look at.
- Of course what you can do as well is just lie on the ground with your binoculars and just browse around the Large Magellanic cloud. You’ll see the Tarantula nebula, and you might see a whole bunch of fuzzy-looking stars, which will be the big collection of globular clusters and other open clusters they have in that galaxy. So well worth having a look there, especially if you have a decent high-powered pair of binoculars, but still quite cool on small binoculars as well.
So, from here from New Zealand, we wish you clear skies so that you can always see the stars, and stay safe - stay inside, keep your two metre distance from people, and don’t get sick. Clear skies, everyone, and let’s hear each other healthy next month.
