The night sky in May 2020

posted 29 Apr 2020, 05:19 by Pete Collins   [ updated 29 Apr 2020, 06:06 ]
by Anne Holt

Sunrise   1st:    05.33       31st:   04.47
Sunset:   1st:   20.39       31st:   21.26

Astro Darkness   1st:  23.28 to 02.42    31st:  none
Ends at 01.20 on the morning of 13th, then none until the end of July.

Day length  1st:  15.05.23     31st:  16.39.19

Full Moon:       7th  at 11.45
New Moon:     22nd  at 18.39

Lunar perigee:    6th at 04.03   (359654 km)
Lunar apogee:    18th at 08.44   (405583 km)

This month's full Moon occurs at a distance of 361184 km, making it a Supermoon.

May full Moon is known as the Flower Moon because so many blossom around this time.  Other names are the Corn Planting Moon and the Anglo Saxon/Old English Milk Moon.

Highlights

After April's excitement of a possible naked eye comet, we're back to having not much to write home about this month.
The sky is much clearer because of the decrease in pollution (I wish the same could be said about light pollution) but to counteract that we lose astronomical darkness from mid month.  We are also losing Venus as it is getting much lower in the evening sky, though still very bright so visible until the last few days of the month.  Mars and Saturn are getting higher in the pre-dawn sky, as is the much brighter Jupiter.  The one major meteor shower is much better seen from the southern hemisphere and, as if that wasn't enough, will be affected by the presence of the almost full Moon.  Also only visible from further south is a newly discovered comet which again promises great things.

Constellations

As the sky darkens at the start of the month Lyra and Cygnus are rising in the north east, followed a couple of hours later by Aquila.  In the later part of the night the Summer Triangle formed by Vega, Deneb and Altair, the brightest star in each of these three constellations, should be easily visible. By the end of the month Aquila will be above the horizon by around 11pm. The brightest part of the Milky Way visible to us in the UK runs through the Summer Triangle and down through Scutum and Sagittarius.

The Plough is still very high in the sky for most of the night, standing on its handle, so Cassiopeia, the W shaped 'Lady in the Chair',  on the opposite side of the Pole Star is very low down in the north.

Bootes, the herdsman, is now riding high although only Arcturus, the brightest star in the celestial northern hemisphere, is above magnitude 2, so its kite asterism may not be easily visible in our light polluted skies. Arcturus is easy to find though - just follow the arc of the Plough's handle down to the south until you come to Arcturus.  Carry on the arc a bit further and you come to the star Spica, the brightest star in Virgo.

At this time of year when you look up to the south you are looking out of the plane of our Milky Way galaxy instead of along it like you do in winter and summer, so there aren't many bright stars, open star clusters and nebulae. However, if you've got a telescope this is a good time of year to hunt down globular clusters like M13, the Great Globular Cluster in Hercules, and faint galaxies like the many galaxies lying in the bowl of Virgo and into Coma Berenices.

Planets

Mercury:  in Aries, mag -1.8
Not visible in early May, on 1st it is only 4 degrees from the Sun.  It reaches superior solar conjunction, when it is on the opposite side of the Sun to the Earth, on 4th, when it passes 6 minutes south of our star.  It then becomes an evening object but still not visible as it is so close to the Sun.  On 10th when it moves into Taurus it reaches perihelion, 0.31AU from the Sun, but still too close to the Sun to be visible.  Its position gets much better in the second half of May, on 15th it is 5 degrees above the horizon at dusk setting at 22.15 and now at mag -1.2.  It gets higher in the evening sky, moving closer to Venus which is now losing height.  They are at their closest - just under 1 degree - on 22nd at 08.44,  but stilll separated by only 1.3 degrees at 21.00, about 8 degrees above the horizon at dusk.  Mercury is to the south, now fainter at mag 0.7.  On 24th at 22.00 the Moon passes 5 degrees SE of the planet, with Venus also close by.  Mercury moves into Gemini on 30th, when it is at its highest point in the evening sky but still only 8 degrees at dusk.  On 31st it sets at 23.39.

Venus:  in Taurus, mag -4.5
Still shining brightly, high in the evening sky, at the start of the month.  On 1st it is at 27 degrees in the west around 21.00, setting at 00.51.  It gets lower during the month, by 14th it is down to 14 degrees as the sky darkens.  On 22nd it is at its closest to Mercury and on 24th the thin crescent Moon passes less than 4 degrees south of the planet, only 8 degrees in the NW at dusk.  By 29th it is only 2 degrees above the horizon as the sky darkens and on 31st appears only 6 degrees from the Sun.

Mars: in Capricorn, mag 0.4
On 1st it rises at 03.34 and reaches 7 degrees above the horizon as the sky begins to brighten.  Its position improves slightly during May, when it moves into Aquarius on 9th it is a degree higher by dawn.  On 15th, when it is at mag 0.2, the Moon passes about 2 and a half degrees to the south.  By month end  Mars is at mag zero, rising at 02.16 and getting to 10 degrees while the sky is still reasonably dark.

Jupiter:  in Sagittarius, mag -2.4
A morning object, still quite low in the sky but easy to spot because of its brightness.  On 1st it rises at 02.26 and reaches 13 degrees in the south by 05.00 as the sky begins to brighten.  On 12th the Moon passes south of the planet,  5 degrees separation at 5am and closest, 2 degrees 4', at 11.09.  On this day it rises at 01.44 and is at 14 degrees in the south by dawn.  On 14th it appears to change direction and moves from east to west across the sky - known as retrograde motion.  Of course it doesn't actually start going the other way, it's a similar effect to when a car passes a slower moving vehicle - when seen from the faster vehicle the other appears to go backwards for a short time.  It is near to Saturn throughout May, they start the month separated by 5 degrees, closest on 18th at just under 4.7 degrees, with Jupiter to the SW.  On 31st it rises at 00.20, slightly brighter at mag -2.6 and visible from around 2am.   It now reaches 18 degrees by dawn.

Saturn:  in Capricorn, mag 0.6
Slightly lower, and much fainter, than Jupiter in the morning sky but still a beautiful sight even through a small scope, with its rings at an angle of 20 degrees.  On 1st it rises at 02.39 and should be visible a couple of hours later, getting to 11 degrees in the SE by the time the sky begins to brighten.  From 11th its apparent motion is also retrograde.  The gibbous Moon passes to the south on 12th,  separated by 2 degrees 38' at 19.55 and by 5 degrees on the morning of 13th.  On 31st it is slightly brighter at mag 0.4, rising at 00.41 and reaching 15 degrees in the SE shorty before 4am as dawn breaks.

Uranus:  in Aries, mag 5.9
Not visible this month.  On 1st its apparent separation from the Sun is only 4 degrees. It moves away slighly during the month but is still below the horizon at dawn on 31st.

Neptune:  in Aquarius, mag 7.9
Again, not visible, still below the horizon as the sky begins to brighten throughout May.

Dwarf Planets

Ceres:  in Aquarius, mag 5.2
The only dwarf palnet which orbits in the (relatively) close Asteroid Belt is still too low for imaging.  On 1st it rises less than an hour before the Sun.  On 31st it rises at 03.04 but still very close to the horizon as day breaks.   On this day, Mars lies about 8 degrees to the north.

The rest, lying in the Kuiper belt, are so distant and therefore faint that even at their best they are a challenge for the most experienced astrophotographers.

Pluto:  in Sagittarius, mag 15.1
Too low for imaging and, because it moves so slowly around the sky, will be for many years yet. 

Haumea in Bootes, mag 17.3, and Makemake in Coma Berenices, mag 17.2, are both high in the sky for most of the night so could be a possible imaging target for the ambitious.  Haumea reaches 52 degrees on 1st and 51 degrees on 31st,  Makemake gets to 60 degrees, falling to 51 degrees.

Eris:  in Cetus, mag 18.8
The most distant and faintest of the 5 officially recognised dwarf planets appears very close to the Sun this month.

On 24th at 10.00, asteroid Vesta passes 2 degrees west of the Moon.  Those watching from North America and parts of Europe (but unfortunately not from Manchester) will see an occultation.

Comets

C/2019 Y4 (ATLAS) has not lived up to expactations - there's a surprise! Rather than becoming an unmissable naked eye object it has broken up into at least 4 fragments. They are in Camelopardalis, circumpolar and reasonably high throughout the night in early May.  It moves into Perseus on 13th, when it is much lower - around 14 degrees maximum, andon 25th dips below the horizon between 11pm and 2am.  It is in Taurus from 27th, when it appears only 12 degrees from the Sun.  Reaches perihelion on 30th.

The other ATLAS,  C/2019 Y1, mag 11.5, is also circumpolar and high enough for imaging throughout the night at the start of May. Moves into Camelopardalis on 3rd, Draco on 9th, and Ursa Major on 14th.  By 31st it is predicted to have faded to mag 14.5 and to be too low in the sky between midnight and 2am.

C/2017 T2 (PANSTARRS) in Camelopardalis, mag 8.9
Again circumpolar, high in the sky all night.  On 18th it briefly crosses the border into Draco then into Ursa Major the following day.  It should brighten slightly during the month, mag 8.8 from 6th to 24th then end the month back at 8.9.

C/2020 F8 (SWAN)
Discovered on 28th March with the Solar and Heliospheric Observatory's SWAN camera.  Great things are predicted for this one. The bad news is that it is currently only visible from the southern hemisphere. It starts the month in Andromeda at around mag 8, moves into Perseus on 12th and Auriga on 31st.  On this day, from our latitude, it will be 12 degrees above the horizon at dusk - still too low for imaging.

For more details and exact positions of all solar system objects see

and for latest news on comets

Meteor Showers

Not a great deal going on this month - and what there is will be seriously marred by moonlight.

Eta Aquarids:  active April 19th to May 28th, peak on the night of 5th/6th. This shower is better seen from south of the equator, from here ZHR is around 10, at best.  These bright, fast moving meteors, ofetn leaving trails, are best seen just before dawn on the morning of 6th.  However the almost full Moon sets just before the Sun rises.  Parent comet 1P/Halley.

Eta Lyrids:  active 3rd to 14th, peak 8th.  ZHR 3. Best seen just before dawn and after dusk on 8th but again there will be significant moonlight interference. Parent comet C/1983 (IRAS-Araki-Alcock).

It is thought that there could be some activity at around 23.00 on May 14th, from debris left by near Earth object 461852 (2006 GY2).  These slow meteors have a radiant in Hercules.

The antihelion source has a radiant moving across northern Scorpio into Libra. ZHR 2, but could be double that towards the end of the month.

And finally: the second half of May is a good time for daytime showers, detectable only using radio or radar equipment.  Most prominent is the daytime Arietids, beginning on May 14th, though the peak is not until early June.



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