The night sky in March 2021
Post date: Feb 26, 2021 3:56:53 PM
by Anne Holt
Sunrise 1st: 06.56 31st: 06.44
Sunset 1st: 17.47 31st: 18.42
Astronomical darkness
1st: 19.42 to 04.58 31st: 21.48 to 04.36
Day Length 1st: 10 hrs 50' 40" 31st: 12 hrs 58' 18"
The Vernal (spring) Equinox is on 20th at 09.37. This is the time when the Sun is at the point where the ecliptic crosses the celestial equator. Despite the name, which means equal night, this day is 12 hrs 11' 30" long. This is because it is the centre of the Sun's disc which is above the horizon for 12 hours, whereas sunrise and sunset are the times when the upper edge appears and disappears. Also, the Sun can be seen for a few minutes before it rises and after it sets because of refraction of its rays by our atmosphere. The closest day to 12 hours is 17th at 11 hrs 58' 41"
Clocks go forward at 01.00 on 28th.
New Moon: 13th at 10.21
Full Moon: 28th at 19.48 (angular diameter 32' 58")
Lunar perigee: 2nd at 05.20 (365421 Km, angular diameter 32' 41")
30th at 06.13 (360310 Km, angular diameter 33' 08")
Lunar apogee: 18th at 05.05 (405252 Km, angular diameter 29' 28")
The full Moon is close to Lunar perigee, so it will appear slightly larger and brighter than average, but not quite enough to be classed as a Supermoon.
The March full Moon is known as the Worm Moon, because this is the time when earthworms appear, now the ground is no longer frozen. It could also refer to insect larvae, which appear from the bark of trees at this time. Other names are the Colonial American Fish Moon, the Celtic Winds or Seed Moon, the Neo Pagan Death Moon and the Chinese Sleepy Moon. There are very many different Indigenous American names, among them the Arapaho Buffalo Dropping their Calves Moon, the Omaha Moon when the Geese Come Home, the similar Haida Noisy Goose Moon and the Algonquin Sap Moon. For the Choctaw it's the Big Famine Moon and the Dakota Sioux called it The Moon when Eyes are Sore from Bright Snow.
It is also the first full Moon in Spring - on or after the Vernal Equinox (counted as March 21st even when, as this year, it's actually on 20th). This makes it the Paschal Moon - the one which is used to calculate the date of Easter Day, which falls on the first Sunday following the full Moon.
Highlights
What highlights? The only thing of note is that there will be some bright mid-evening passes of the International Space Station from the 21st until the end of the month.
The nights are getting shorter by just over 4 minutes each day. By month end we are down to just under 7 hours of astro darkness, not beginning until almost 10pm after the dreaded BST begins on 28th. We're even beginning to lose the beautiful Winter Hexagon - Rigel sets around midnight on 1st, 11pm (BST) on 31st. There are no bright comets, no meteor showers, and the naked eye planets are not well positioned. The brightest asteroid, 4 Vesta, is at opposition on 4th but, unfortunately, it isn't a particularly favourable one only reaching mag 6.2 - out of naked eye range but an easy binocular target.
Things are better for the most experienced astrophotographers, dwarf planets Haumea and Makemake are high in the sky and we have a couple of very faint circumpolar comets.
For the rest of us, we haven't even got HPAG's end of season party to look forward to this year.
Constellations
We are now losing the winter highlights of Orion, Sirius and Taurus soon after midnight, though they are still prominent in the south in the early part of the night. Auriga, with the bright yellowish-white star Capella, is now overhead soon after sunset, with Gemini and Leo also prominent. The not very obvious zodiac constellation, Cancer, is now well placed. The Plough is overhead by midnight, the handle pointing to the orange hued Arcturus, the brightest star north of the celestial equator, in the constellation of Bootes. By the end of March the Summer Triangle will be above the horizon soon after 2am - or by 1am if you've forgotten to put the clock forward.
Planets
Mercury: in Capricorn, mag 0.2
A morning object, but very low in the pre dawn sky. On 1st it rises at 05.04, nearly an hour before the Sun, but is still on the horizon as the sky begins to brighten. On the morning of 5th it is only 19' north of Jupiter but while the gas giant might be bright enough to be seen in the twilight, Mercury is too faint.
The usual important warning: DO NOT attempt to see the pair through binoculars, even catching the first few rays of the rising Sun can result in permanent blindness. You might see Mercury but it could be the last thing that you ever do see.
Even on 6th when it is at greatest western elongation, 27 degrees 18' from the Sun, Mercury is no higher at dawn because of the very shallow angle of the ecliptic in the morning sky at this time of year. It moves into Aquarius on 14th, on this day it is at aphelion, 0.47 AU from the Sun, but now 1 degree below the horizon at dawn. On 31st it rises at 06.34, only 10 minutes before sunrise.
Venus: in Aquarius, mag -3.9
Not visible this month. On 1st it rises about the same time as the Sun, appearing only 6 degrees from it. It gets even closer during the month, on 18th, when it goes into Pisces, they are separated by 2 degrees. It is at superior conjunction on 26th, passing 1 degree 21' to the south of the Sun. It then becomes a morning object but still much too close to be visible, on 31st the separation is still not much over 1 degree.
Mars: in Taurus, mag 0.9
Now only visible before midnight and fading quite rapidly. On 1st it culminates in daylight, becoming visible around 18.30 as the sky darkens, 54 degrees in the SW, a little to the south of the Pleiades. It remains close to the cluster for the next few nights, on 3rd and 4th it is about 2 degrees 40' from the centre. On 19th the 32% waxing Moon passes between Mars and the similarly hued Aldebaran - the eye of the bull, with the Moon 2 degrees 20' south of Mars at 20.15. On 31st it will be visible from 20.30, when it will be 45 degrees above the SW horizon, now down to mag 1.3 and setting at 02.07.
Jupiter: in Capricorn, mag -2.0
Now a morning object but too low to be easily visible for most of the month. On 1st it rises at 06.18 but only gets to 1 degree above the horizon in darkness. On 10th the 7% Moon passes 4 degrees 02' to the south of the planet but Jupiter is only 2 degrees above the horizon at dawn. By the time the Moon rises, around 6am, the sky will be quite bright. Jupiter might be visible towards the end of March, to observers with a low, clear SE horizon, on 31st it rises at 05.33 and gets to 5 degrees before the sky brightens.
Saturn: in Capricorn, mag 0.7
Also very low in the pre-dawn sky - too low and too faint to be seen in the morning twilight, just over 8 degrees to the west of Jupiter. On 1st it rises at 05.59 but hasn't cleared the horizon by dawn. It is also close to the Moon on the morning of 10th, still very low in the SE as the sky brightens. On 31st it rises at 05.08 and is 5 degrees above the horizon as dawn breaks, almost 12 degrees west of Jupiter.
Uranus: in Aries, mag 5.8
Now low in the early evening sky. On 1st it should be visible from around 19.00, when it is 34 degrees in the SW, remaining high enough for observing for about 90 minutes and setting at 23.12. Much more difficult to find from mid month, on 18th it is 21 degrees above the horizon at dusk, setting at 22.09. By 31st, slightly fainter at mag 5.9 it is only 10 degrees as the sky darkens, setting at 22.22.
Neptune: in Aquarius, mag 8.0
Too low to be observable this month. On 1st it sets only 45 minutes after the Sun and appears separated from it by 9 degrees. It is at solar conjunction on 11th, when it passes 1 degree 04' to the south. It is then a morning object, in conjunction with Mercury on 29th, with Neptune 1 degree 23' to the north at 20.10, but both still too close to the Sun to be observed safely. On 31st it rises only 20 minutes before the Sun, separation 19 degrees.
Dwarf Planets
Ceres: in Pisces, mag 9.3
Not visible this month as it approaches solar conjunction in early April, on 1st it is only 2 degrees above the horizon at dusk. It moves into Cetus on 4th and by the end of the month appears 8 degrees from the Sun, setting at 19.37.
Pluto: in Sagittarius, mag 15.1
After the orbit of the then planet was calculated it was realised, by re-examining earlier photographs, that it had been imaged on at least 16 previous occasions. The earliest of these were in August and November 1909, only 4 years after Lowell began his search, by E E Barnard at the Yerkes Observatory in Illinois. Lowell himself had unknowningly imaged it twice in 1915, but died the following year without realising - presumably because it was then in Orion, where he wouldn't have expected to find it.
This precovery of later found objects is quite common. It is now known that Uranus was seen in 1690 by John Flamsteed, the first Astronomer Royal, who thought it was a star and catalogued it as 34 Tauri. Even further back, Galileo saw Neptune in 1612.
However, at the moment we can't see Pluto. On 1st it rises at 05.34, on 31st at 04.38 but is much too low for telescopic observing or imaging.
Haumea: in Bootes, mag 17.4
The good news is that it's high in the sky for most of the night. The bad news is that it's so faint that it's only accessible to the very best, most experienced astrophotographers. On 1st it rises at 20.33 and reaches 21 degrees in the east by 23.00. Its highest point, 52 degrees south, is at 04.00 and it is down to 48 degrees in the SW as dawn breaks. On 31st it rises at 19.22 and gets to 21 degrees in the east by about 22.00, culminating at 03.01, still reaching 52 degrees. Remains high until dawn when it is 43 degrees in the SW.
Makemake: in Coma Berenices, mag 17.1
Also very high but very faint. On 1st it rises at 18.18 and is high enough for imaging soon after 21.00, when it reaches 21 degrees in the east. It culminates, 59 degrees above the southern horizon, at 02.47 and is down to 46 degrees in the SW by dawn. It is at opposition on 27th, when it is at its highest point, 59 degrees in the south, at 01.03. On 31st it is 30 degrees in the east as the sky darkens around 21.00, and 59 degrees south at 01.57. It remains reasonably high until dawn, when it is 40 degrees in the west.
Eris: in Cetus, mag 18.8
Eris was first seen on 23rd October 2003 and confirmed in January 2005. It was given the nickname Xena by the discovery team of Mike Brown, Chad Trujillo and David Rabonowitz - the name began with X, which was considered appropriate for what was initially thought to be the 10th planet. It was later given the name Eris, after the goddess of discord, and was reclassified as a dwarf planet in 2006, when the new category was introduced. It has a very eccentric orbit, at its closest, 37.9 AU from the Sun, it is within the orbit of Neptune and closer than Pluto's aphelion. However, at its furthest, 97.65 AU, it is beyond the main Kuiper Belt in the region known as the Scattered Disc. It takes 559 years to go round the Sun so, since its discovery, has completed only about one thirtieth of an orbit - in time. In distance probably less as it is currently close to aphelion when it moves more slowly. It is still only about 5 degrees from from where it was first seen.
It is too low for imaging this month, on 1st it is 17 degrees above the horizon at dusk and by the last week in March is on the horizon as the sky darkens. On 31st it appears only 17 degrees from the Sun.
Asteroids
4 Vesta: in Leo, mag 6.2
The second largest member of the asteroid belt contains about 9% of its mass. It was discovered in March 1802 by Heinrich Wilhelm Olbers (of Paradox fame) and named after the Roman goddess of home and the hearth. It's the only asteroid known to have a core, mantle and crust similar to the rocky terrestrial planets but is thought to have formed before them. It would probably have become a planet if it wasn't for the gravitational influence of Jupiter. It is the source of about 6% of meteorites which land on Earth.
It's the brightest of the asteroids, magnitude ranges between 5.1 and 8.48. Unfortunately it isn't at its brightest at the moment but should be an easy binocular target. On 1st it rises at 17.22 and reaches 21 degrees in the east by 20.00, culminating at 00.58, when it is 58 degrees above the southern horizon. By dawn it will be down to 24 degrees in the west. On 4th, when it is at opposition, it will be high enough for observing from 19.45 until dawn, culminating at 00.43, at 52 degrees in the south. On 31st, down slightly to mag 6.6, it culminates at 23.30, now at 54 degrees, and is visible until the end of astro darkness when it is 22 degrees above the western horizon.
Comets
Still nothing exciting to report, there are a few around but they are very low or very faint.
C/2021 A2 (NEOWISE) is circumpolar, in Monoceros. Starts the month at mag 12.8, fading to 15.1 by 31st, now in Auriga and 'visible' for most of the night.
C/2021 A1 (Leonard) The one to watch - but not yet! Again circumpolar, in Ursa Major, high in the sky for most of the night but still very faint - around mag 18.
C/2020 R4 (ATLAS): in Aquarius, mag 7.3
Very low in the morning sky. On 1st it rises at 05.13 and is only 1 degree above the horizon by dawn. It moves into Capricorn on 4th, when it is slightly higher, 3 degrees, before the sky brightens. It is at peak brightness on 13th, at an estimated mag of 6.6, and reaches 8 degrees in reasonable darkness, having risen at 03.59. It is in Aquila from 15th and on 31st rises at 02.36 and gets to 21 degrees by dawn, only slightly fainter at mag 6.8.
Meteor Showers
March is another very poor month, especially for those of us in the northern hemisphere. The only shower active at this time, the Gamma Normids, has a radiant so far south, 50 degrees, that we won't see any activity fron Manchester. Even for observers in the south it isn't a particularly good shower, active Feb 25th to March 28th, peak 14th, ZHR 6 - though meteors from this are said to be often indistinguishable from background sporadic ones.
The radiant of the ANT, moving across southern Virgo is low, ZHR no more han 2 or 3, though there could possibly be a few more around 17th.
Credits
Most of the solar system information given here is from:
More information, exact co-ordinates and finder charts of all solar system objects can be found on this site.
Also quite useful is https://theskylive.com
Other information is from various internet sources, including NASA, Britannica, Space Facts, Universe Today and, when all else fails,Wikipedia.
