A monthly look at astronomical events in the sky and on Earth
Oh dear! Those jobs we’ve put off doing for years and for which we can no longer use the excuse that we haven’t got time to do, will have to be done. There are no excuses left; we’re confined to barracks! So in this era of social distancing, are there any reasons for us astronomers to be cheerful? Well, maybe.
Firstly, on the assumption we don’t succumb to it, there’s one thing this wretched virus cannot steal from us, and that is the joy and wonder we feel when we gaze upwards at a beautiful night sky or tweak that focus wheel slightly to spy some subtle detail on the surface of a planet. For many, astronomy is a silent and solitary pursuit. We can still set up our telescopes and gaze in wonder at the glories of the heavens. And even if we prefer to share this experience with one or two others, we can set up far enough apart to remain safe.
Secondly, for those of us who live in an urban or semi-urban setting, the closure of facilities such as sports pitches which under normal circumstances would be illuminated at night, reduces the background sky glow, and reveals many more stars and fainter deep sky objects.
And the third reason to be cheerful is that the reduction in aircraft movements, road traffic and industrial activity has resulted in an equal reduction in condensation trails (“contrails”) and general air and sky pollution. One Stanford University professor has calculated that the dwindling harmful emissions due to the Coronavirus outbreak may have saved 73,000 lives in China alone (over twenty times the number of deaths due to the virus!) For astronomers, it’s as though the atmosphere has been washed, resulting in atmospheric clarity not seen for decades.
So my advice is to get out there, especially during the dark sky nights of the second half of April, and take advantage of what hopefully will be really dark and clear skies. If you don’t, the next set of moonless nights, in late May, will not get “Astronomically” (completely) dark because by then the Sun will be too far north.
STOP PRESS – A Potential Naked-Eye Comet
A new comet, designated ATLAS (C/2019 Y4) was discovered last December and by the 21st March had brightened to magnitude 8.5. It is expected to brighten much more and by mid-April may get to magnitude 7.0 or brighter. Later, it could be an easy naked eye object. Read all about it in the following Sky & Telescope article.
I recommend you start looking for it on April 10th when it passes very close to two stars in Camelopardalis (42 Cam and 36 Cam). Start your search at 2215 BST (astronomical twilight ends) and you’ll have at least an hour before the Moon rises and the background sky brightens.
Click on image to enlarge
Click on image to enlarge
Use the sky chart above (from SkyViewCafe.com) to locate those stars in Camelopardalis (which is about 55° high in the NW). If you magnify the chart, you’ll see the stars quite clearly. Then use the second chart – copied from the free Sky & Telescope article – to find the comet. Please note, you’re looking for an object at least 15 arch minutes in diameter (half the apparent diameter of the Moon) and faint and fuzzy, so use a lowish magnification and a fast focal ratio instrument.
The Solar System
And just in case you’re new to astronomy, do recognise that you will blind yourself if you look at the sun using binoculars of a telescope. To observe safely, use the eyepiece projection method or make yourself a full aperture solar filter using the correct filter material from a reputable source.
Best seen in a waxing gibbous phase in the first few days of the month then as a waxing crescent from Friday 24th through to the end of the month.
Mercury is a morning object and not well placed for observing this month. Wait until May.
Venus dominates the western sky this month. It reached greatest eastern elongation on the 24th of March so will now appear as a narrowing but increasingly large crescent as we go through the month. It’s diameter and magnitude on the 1st are 25.7″ and -4.6, but by the 30th it will have grown to a whopping 38.7″ and a magnitude of -4.7. Its greatest brilliance is on the 28th.
On the 3rd, Venus will skirt to within ¼° of the Pleiades and be a fine sight in binoculars or any telescope.
Mars, Jupiter and Saturn
These planets are clustered together in the morning sky and on the 15th are joined by the waning crescent Moon. None of these three planets is worth observing for its own sake at the moment, but the group – together with the Moon – is definitely worth a look if you can force yourself out of bed by about 0500. They’re only at 6-9° altitude and in the SE-SSE (azimuth 145°).
Uranus and Neptune
Both these planets are too close to the Sun to observe this month.
Lyrid Meteor Shower
This shower peaks on April 22nd. It won’t be dramatic, with estimates of about 16 meteors per hour radiating from a point between Lyra and Hercules high in the south. Best time is about 4 a.m. BST.
Deep Sky Objects
As I indicated earlier in this document, the second half of April this year presents an ideal opportunity to get out there under truly dark skies and spot some deep sky objects that can perhaps only be seen at this time of year. From the 11th onwards, the Moon is out of the way and there are some astronomically dark hours available (Sun at least 18° below horizon). These hours are as follows (all BST):
After 6th May, there is no more total darkness until August.
There follows a shortlist of objects that are roughly in the south this month at 2240 hrs.
M44 – Beehive Cluster (aka Praesepe)
An open cluster in Cancer of about 1000 stars with a combined magnitude of 3.7. Easily visible to the naked eye on a clear, dark night. Best seen with binoculars or any eyepiece-telescope combination that delivers a field diameter of 1½°. That’s three times the apparent diameter of the Moon.
The Leo and Virgo Galaxy Clusters
The detailed sky chart below shows the location of these famous clusters of galaxies. April is the best time to see these before midnight, and your last chance until February next year.
See this Sky and Telescope article for an excellent description and photos of these and other nearby galaxies.
The Leo Triplet (M65, M66 and NGC3628)
A famous trio of galaxies of about 9th or 10th magnitude all visible in the same low power field. It’s possible to see them with a 3″ refractor but larger apertures will make spotting them much easier.
M84 and M86 (imaged by Sid leach in this link)
These two galaxies are the brightest close pair within the massive Virgo cluster. It’s worth just slowly panning across this area of sky with a wide field eyepiece to see how many galaxies you can spot.
Finally, while you’re out and set up, why not have a go at three more objects, this time nearly overhead or to the north. M51, M81 and M82. The chart below is centred on the zenith. M51 isn’t far from the end of the Bear’s tail, and the other two are to the NW of that constellation. M81 is at magnitude 6.9 and fairly easy to spot. M51 and M82 are both at magnitude 8.4 so a bit more difficult, but quite achievable with even a small telescope.
Passes of the International Space Station (ISS)
The ISS is only visible on the 1st, 2nd and 4th April. There are many opportunities in May however. See the Heavens-Above web site for more details. Here is a link with all fields relevant to York selected.
For action in the satellite and spacecraft world and for up-to-date news, scroll https://www.space.com/32286-space-calendar.html
Clear skies and good viewing.
John Rowland 27/ March 2020