This page provides some astronomical information on a monthly basis for those of you living in the United Kingdom. Timings are in BST (British Summer Time) unless otherwise noted. York will be used as a representative location for the United Kingdom. Latest additions or updates are highlighted with a red border.
This month we have sections on:
Clocks in the United Kingdom and the European Union go back one hour on the last Sunday of October under the provisions of The Summer Time Order 2002, UK Statutory Instruments 2002 No. 262 and Directive 2000/84/EC of the European Parliament and of the Council of 19th January 2001 on summer-time arrangements respectively. Consequently, on October 31st at 02:00 BST (British Summer Time) clocks are moved back to 01:00 GMT (Greenwich Mean Time). Any event listed here taking place after 01:00 GMT on October 31st will be given in terms of Greenwich Mean Time.
Additional information on the phases of the Moon, the seasons, summer times, eclipses, chronological cycles and eras, religious calendars, the civil calendar and holiday dates in the United Kingdom can be found in HMNAO's Astronomical and Calendarial Sheet No. 108 for 2021. This is a pdf document for which a document reader can be downloaded by clicking on the Adobe Reader icon above.
↻ The last update to this page was made on Friday, 2021 October 22 at 09:53:27 BST.
An animated view of the Sun's disk over the last twenty eight days is shown in the image on the left. North is at the top of the image and east is to the left. These images come from the Helioseismic and Magnetic Imager instrument on the NASA Solar Dynamics Observatory (SDO) satellite. More multi-wavelength data from the SDO can be found here.
There is one active region on the visible disk of the Sun approaching the central meridian. AR2886 lies in the south-eastern quadrant of the Sun and has a simple magnetic field, posing little threat of strong solar flare activity. A new, potentially active sunspot is also emerging over the south-eastern limb. As yet undesignated, it has already generated several minor B-class solar flares. The total number of spotless days for 2021 remains at sixty, or 20% of the year so far. Solar winds are currently blowing with velocities of up to 440 km/s and the planetary Kp geomagnetic activity index is likely to peak at 2 (quiet) today. There is a moderately-sized coronal hole in the south-western quadrant of the Sun very close to the limb. The Earth lies within a stream of solar wind emanating from this departing feature. The overall amount of solar activity remains at very low levels.
NASA reported that a reversal of the Sun's magnetic field took place at the start of 2014 indicating that the maximum of Solar Cycle 24 had been reached. A plot of sunspot numbers, both observed and predicted versus time indicates that the solar maximum of Solar Cycle 24 was more complex than had been previously predicted. The maximum was double-peaked in a similar manner to that of the previous maximum of 2001/2002. The individual peaks occurred in 2011 and 2014 with the latter being the larger of the two. However, sunspot numbers were significantly down on the predictions made for the maximum — indeed Solar Cycle 24 may be the weakest in the last 100 years or so i.e. since Solar Cycle 14.
The declining phase of the solar cycle brings increased numbers of cosmic rays to the Earth, an increased frequency of 'pink' aurorae and a slight dimming of the Sun of approximately 0.1% in terms of the total solar irradiance. TSIS-1 was launched on December 15th 2017, which will monitor the Sun over a five-year period covering the whole of the current solar minimum. Cooling and contraction of the Earth's upper atmosphere in response to the changes on the Sun due to the solar minimum also delayed the orbital decay of satellites such as the Chinese space station, Tiangong 1, which returned to Earth on Monday April 2nd 2018 at 00:16 UTC. The Sun's magnetic field and solar winds provide some protection for the Earth from cosmic rays. A recent paper in the journal Space Weather claims that this solar minimum could see a rise in the number of cosmic rays reaching the Earth by as much as 30% due to the weakening magnetic field of the Sun and reduced levels of solar winds. This could mean an increased risk of radiation exposure for travellers on commercial airlines and possible changes to the climate.
During the post maximum phase of the solar cycle individual energetic events can spawn some of the most powerful flares and coronal mass ejections of the cycle. The so-called Carrington event on September 1st–2nd 1859 during Solar Cycle 10 is a good example of just what might ensue from this type of violent outburst. On 2020 September 15th NASA and NOAA announced that a minimum of the Sun's activity had been reached in December 2019 bringing to an end the old Solar Cycle 24. Initial predictions were that Solar Cycle 25 would be a weak one, similar to its predecessor, peaking in 2025. As a result, it would produce a deep minimum with long periods without much sunspot or flare activity. Space weather would be dominated by solar winds and cosmic rays rather than sunspots and solar flare activity. However, Solar Cycle 25 has produced larger numbers of sunspots relative to the predictions made by the NOAA/NASA Solar Cycle 25 Prediction Panel in 2019. For the past eleven months, the sunspot number has significantly exceeded the official forecast. This may suggest a stronger Solar Cycle 25 than predicted which could peak in late 2024 rather than July 2025.
The sequence of Moon phases for this month and their designations are shown in the following animation:
|Moon phases for October 2021 are as follows:|
|New Moon||—||Wednesday October 6th at 12:05 BST
|First Quarter||—||Wednesday October 13th at 04:25 BST|
|Full Moon||—||Wednesday October 20th at 15:57 BST
|Last Quarter||—||Thursday October 28th at 21:05 BST|
The Moon is at perigee (i.e. nearest to the Earth) on Friday October 8th at 18:28 BST when it is 363,386 km from the Earth. It is at apogee (i.e. furthest from the Earth) on Sunday October 24th at 16:28 BST when it is 405,615 km from the Earth.
There are no occultations of either planets or bright stars this month. The next planetary occultations for Mercury and Venus will take place in early November.
Please follow the New Moon link above to find out more about our Crescent Moon Watch program which involves making a sighting of the new crescent moon as early as possible after the instant of New Moon each month.
There are four eclipses visible from the Earth during 2021 — two Lunar eclipses (one total and one partial) and two Solar eclipses (one annular and one total). Parts of two of the eclipses are visible from the United Kingdom, namely the partial phase of the annular eclipse of the Sun and some of the partial eclipse of the Moon. The total eclipses of the Sun and Moon are not visible from the United Kingdom.
A total eclipse of the Moon occurred on Wednesday May 26th 2021. It was visible in its entirety from south-westernmost Alaska, the Aleutian Islands, the Hawaiian Islands, Polynesia, the central Pacific Ocean region, New Zealand, Melanesia, Micronesia, central and eastern Australia and parts of Antarctica. Parts of the eclipse were visible from the Americas except north-eastern Canada and eastern parts of South America, Indonesia, the Philippines, Japan, eastern Asia, north-easternmost Russia and the eastern half of the Indian Ocean. The eclipse began at 08:46 UT and ended at 13:51 UT. The Moon entered the umbral shadow at 09:45 UT. Totality began at 11:10 UT and ended at 11:28 UT. The Moon left the umbral shadow at 12:53 UT. The eclipse was not visible from the United Kingdom.
An annular eclipse of the Sun occurred on Thursday June 10th 2021. It was visible as a partial eclipse from the north-eastern part of North America, the Arctic Ocean, most of Greenland, Iceland, northern Europe (including the British Isles), Scandinavia, most of Russia, Mongolia and most of China. The path of annularity began over central Ontario and crossed over north-western Quebec, the southern part of Baffin Island, the north-western part of Greenland, the North Pole (for the only time this century) and the north-eastern part of Siberia. The eclipse began at 08:12 UT and ended at 13:11 UT. The annular phase started at 09:50 UT and ended at 11:33 UT. The maximum duration of annularity of 3m 48s took place at 10:42 UT over the sea between Ellesmere Island and north-western Greenland. From York, the partial eclipse started at 10:09 BST and ended at 12:30 BST. The maximum obscuration occurred high in the south-eastern sky at 11:17 BST when 25.6% of the Sun was obscured.
A deep partial eclipse of the Moon occurs on Friday November 19th 2021. It is visible in its entirety from most of North America except the easternmost parts, Mexico, the eastern and central Pacific Ocean regions and north-eastern parts of Russia. Parts of the eclipse are visible from Scandinavia, the British Isles, Iceland, South and Central America, Australasia, Japan, the Philippines, most of Indonesia, eastern and northern Asia. The eclipse starts at 06:00 UT and ends at 12:06 UT. The umbral phase of the eclipse starts at 07:18 UT and ends at 10:47 UT. The maximum of the eclipse occurs at 09:03 UT with a magnitude of 0.978. The eclipse is visible in part from the United Kingdom. From York, the partial eclipse starts at 06:00 UT and ends at 07:40 UT at moonset.
A total eclipse of the Sun occurs on Saturday December 4th 2021. It is visible as a partial eclipse from Antarctica, the South Atlantic Ocean, the southernmost part of South Africa, the South Indian Ocean, Tasmania and the southernmost part of Australia. The path of totality starts approximately 450 km to the east of the Falkland Islands, crosses the Weddell Sea and the Ronne Ice Shelf, Ellsworth Land and ends over the Amundsen Sea, approximately 500 km from the coast of western Antarctica. The eclipse starts at 05:29 UT and ends at 09:38 UT. The total phase of the eclipse starts at 07:00 UT and ends at 08:07 UT. The maximum duration of totality is 1m 57s at 07:33 UT over the Ronne Ice Shelf in western Antarctica. The eclipse is not visible from the United Kingdom.
Further information on all the eclipses in 2021 can be found on the Eclipses Online web pages. This web site provides information on both solar and lunar eclipses in the period from 1501 CE to 2100 CE. Global circumstances of both solar and lunar eclipses are provided as well as local circumstances of the solar eclipses based on a gazetteer of approximately 1500 locations worldwide. Eclipses for next year, 2022, are also available.
Mercury is not visible during the first half of the month, reaching inferior conjunction on Saturday October 9th. It reaches greatest western elongation on Monday October 25th and is at its most favourable morning apparition of the year for northern observers, rising about an hour or so before the Sun. Mercury is very low in the east south-eastern morning twilight sky, brightening from magnitude +2.0 in the middle of the month to magnitude −0.8 at the end of October.
Venus lies in the south south-western evening twilight sky at an elongation from the Sun which increases during the month from 45° to 47° i.e. greatest eastern elongation on Friday October 29th. Despite the increase in elongation, it remains poorly placed for northern observers due to its southerly declination. It brightens noticeably from magnitude −4.2 at the start of the month to −4.6 at the end of October. Venus lies 3° south of the waxing crescent moon on Saturday October 9th and 1.5° north of Antares (α Scorpii) on Saturday October 16th.
Mars is now too close to the Sun to be observed and reaches conjunction with the Sun on Friday October 8th. It will re-emerge into the morning twilight in the constellation of Libra at the end of November.
Jupiter rises around two hours before sunset and sets a couple of hours after midnight and lies in the north-eastern part of the constellation of Capricornus throughout October. It continues its retrograde or westward motion until mid-October when it reverses direction. Jupiter fades somewhat from magnitude −2.7 at the start of the month to magnitude −2.5 at the end of October. It lies 4° north of the waxing gibbous moon on Saturday October 16th.
Saturn rises two to three hours before sunset and sets about an hour after midnight. It lies in the central western part of the constellation of Capricornus throughout October. Saturn continues its retrograde or westward motion until the second week of October when it reverses direction and fades somewhat from magnitude +0.5 at the start of the month to magnitude +0.7 at the end of October. It lies 4° north of the waxing gibbous moon on Thursday October 14th. The north side of the ring plane is exposed with a tilt of 18° with the ring system spanning 40 arcseconds while the planet's disk is only 17 arcseconds wide.
Uranus is visible reasonably high in the southern sky before the start of morning twilight throughout October, rising around sunset. As it approaches opposition on Friday November 5th, Uranus is visible for most of the night as a blue-green object which remains at magnitude +5.7 throughout October. Uranus lies in the central southern part of the constellation of Aries where it remains for the rest of the year. It lies approximately 5.4° north of the fourth magnitude A9 giant star 87 Ceti (μ Ceti). This planet can also be glimpsed with the naked eye under optimum conditions.
Neptune is visible in the southern sky just after midnight throughout October, rising an hour or so before sunset. Neptune is a bluish object which remains at magnitude +7.8 throughout October. It lies in the north-eastern part of the constellation of Aquarius where it remains for the rest of the year. Neptune lies approximately 9.1° to the north east of the third magnitude M2.5 red-giant star Hydor (λ Aquarii). It is normally visible with good binoculars under optimum conditions although it can also be difficult to distinguish Neptune from other stellar objects of a similar magnitude.
Pluto rises about three hours before sunset and sets around midnight, making it visible in the southern sky in the early evening throughout October for observers using larger telescopes. It lies in the north-eastern part of the constellation of Sagittarius about 11.8° to the south west of the third magnitude binary pair known as Dabih Major and Dabih Minor (β Capricorni) in mid-October. Strictly speaking, this is a dwarf planet which was demoted from the ranks of the 'bona-fide' planets at the 2006 International Astronomical Union General Assembly in Prague. At magnitude +14.8, you will need a much larger telescope to find this remote member of the Solar System.
The rarely-spotted Zodiacal Light is best seen in the half hour or so before astronomical twilight starts in the morning or in the half hour or so after astronomical twilight ends in the evening. It is best seen when the ecliptic, the path the Sun takes in the night sky, is at a steep angle to the horizon. In northerly latitudes, this occurs in the western evening post-twilight sky in February and March and the eastern morning pre-twilight sky in September and October. The Zodiacal Light appears as a large, softly radiant pyramid of light with its base near the horizon and its axis centred on the Zodiacal constellations. It appears to be about as bright as the Milky Way, consequently a dark, unpolluted sky without haze is essential to see this phenomenon. Beware, it can easily be confused with the twilight itself. In the photograph, the Zodiacal Light is on the left and the Milky Way is on the right. For York, astronomical twilight starts in the morning at around 05:10 BST at the beginning of the month and at 05:05 GMT at the end of the month. The cause of this so-called 'false dawn' is sunlight reflecting of a lens-shaped cloud of dust in the plane of the inner solar system.
The Orionid meteor shower is active over very nearly the whole of October and the first week of November i.e. October 2nd–November 7th. The shower exhibits a moderate number of fast meteors and fireballs with long trains, reaching a peak of activity at the end of the third week of October. These meteors are debris connected with the orbit of 1P/Halley's Comet which is encountered by the Earth at this time of year. The full moon strongly interferes with observations on the night of October 20th-21st when the shower is at its maximum. This means that moonlight will interfere with the optimum early morning observation window for this shower when up to 20-30 meteors per hour could normally be observed. Occasionally, the peak rate can reach 70 meteors per hour on a 12-year period due to the influence of Jupiter. Unfortunately, we are close to the minimum of that cycle. The radiant, the point from which the meteors appear to emanate, lies on the border of the constellations of Orion and Gemini. Subsidiary maxima close to the main peak of activity ensure that rates will remain at the higher level for several days around October 20th–21st.
The Draconids, a weak shower with a rate of around 5-10 meteors per hour, is active during the second week of October, peaking on Thursday October 8th at 18:30 GMT. The shower consists of extremely slow-moving meteors and is best seen when comet 21P/Giacobini-Zinner returns to perihelion which last occurred on 2018 September 10th. The radiant lies close to the head of the constellation of Draco the Dragon, making the radiant circumpolar from our latitudes and best seen during the first half of the night. Fortunately, the Moon is close to the last quarter phase and consequently moonlight does not interfere with the evening observation window this year. No other regular showers exhibiting significant numbers of meteors are active this month. Further information on this and other meteor showers occurring during 2021 can be found at the International Meteor Organization and their 2021 Meteor Shower Calendar.
Meteors can exhibit a variety of colours when they burn up in the Earth's atmosphere. The colour reflects the chemical composition of the meteor. For instance, a red colouration is indicative of atmospheric nitrogen and oxygen, yellow suggests iron, purple or violet suggests calcium, orange suggests sodium, blue or white suggests magnesium and green suggests nickel. The velocity of the meteor also has an effect on its colour as higher kinetic energies will intensify certain colours. Slow meteors appear to be red or orange whereas faster ones appear to be blue. However, the most commonly-observed colours are yellow, orange and sometimes green.
It is worth noting that bright sporadic meteors and fireballs are possible at any time e.g. the fireball observed over many parts of England and Scotland on Saturday March 3rd 2012 at 21:40 GMT. Larger events, known as bolides, are rarer. Typically, this is a very bright fireball reaching an apparent magnitude of −14 or so, perhaps three times as bright as a full moon. Even rarer are the superbolides, events with apparent magnitudes of −17 or so, around 50 times brighter than the full moon. A recent example of a superbolide was the Chelyabinsk meteor of Friday 15th February 2013 at 03:20 UTC which may have been a 20-metre diameter near-Earth asteroid.
A fireball was seen over a significant fraction of the United Kingdom and northern Europe on Sunday February 28th at 21:54 UT lasting approximately 3.5 seconds. It was estimated to be a magnitude −9 fireball which generated a sonic boom as it fell. Fragments of the object may have impacted the Earth in the area north of Cheltenham in Gloucestershire. Its solar-system point of origin may lie in the asteroid belt between Mars and Jupiter. It has since been reported that at least part of the carbonaceous chondrite fell at a property in Winchcombe in Gloucestershire making it the first UK-based meteorite find in the past 30 years. The significance of this type of dark stony meteorite lies in the fact that its chemistry is similar to that of the early Solar System.
A loud sonic boom was heard at 14:58 UT on Saturday March 20th 2021. It rattled windows and shook homes for about 20 to 30 seconds and was heard over large tracts of Dorset, Devon, Somerset and Jersey. An explosion, an earthquake, thunder and a sonic boom from an RAF aircraft have all been ruled out. The culprit appears to be a daylight fireball or bolide which may have landed in the Bristol Channel. It has been photographed and may also have been detected on a Eumetsat weather satellite image. To be visible in daylight, the meteor must have been of a significant size, large enough for debris to have reached the ground. Its track through the atmosphere may be revealed by analysis of photographic material.
Another loosely-related phenomenon is the re-entry of space debris from space vehicles and satellites whose orbits are decaying to the point where they burn up in the Earth's atmosphere. A couple of well-reported examples of this occurred at around 23:00 BST on Friday September 21st 2012 as well as the return of the GOCE satellite just after midnight on Tuesday November 12th 2013.
There are a number of comets around the sky at the moment. However, most of them require telescopic assistance to see them and some may be too far south in the sky to be seen by observers based in the United Kingdom. Here is a brief summary of the comets brighter than eleventh magnitude that may be accessible to observers with binoculars or small telescopes in the northern hemisphere.
C/2019 L3 (Atlas) starts the month as a tenth magnitude object in the constellation of Auriga. It then moves into the constellation of Lynx. on the second day of the month and remains there for the remainder of October. It should brighten slowly by about 0.4 magnitudes as the month progresses and will be visible with a small telescope reasonably high in the eastern morning pre-twilight sky in the south-western part of Lynx. It will reach perihelion on Sunday January 9th 2022.
67P/Churyumov-Gerasimenko starts the month as a magnitude +10.9 object in the constellation of Taurus. It then moves into the constellation of Gemini in the middle of the month and remains there for the remainder of October. It should brighten slowly by about 0.6 magnitudes as the month progresses and will be visible with a small telescope reasonably high in the southern morning pre-twilight sky. On Tuesday November 2nd this comet will reach perihelion, passing within 0.4 au of the Earth when it is predicted to reach a maximum brightness of magnitude +10.3.
29P/Schwassmann-Wachmann starts the month as a magnitude +10.9 object in the constellation of Auriga. It will remain in Auriga for the remainder of October and should brighten slightly by about 0.1 magnitudes as the month progresses. 29P/Schwassmann-Wachmann will be visible with a small telescope reasonably high in the southern morning pre-twilight sky. Its current brightness is due to a three-magnitude outburst on Saturday September 25th which may last for a couple of weeks before fading back to around thirteenth magnitude. Latest observations show that the comet is ejecting shells of material that are expanding and becoming progressively less opaque to the point where background stars are visible though the expanding cloud. Sadly, these images were taken with a 0.5 metre iTelescope - T11 telescope, significantly larger than most amateur-sized telescopes.
One possibility for a naked-eye comet in the run up to Christmas is C/2021 A1 (Leonard) in early/mid-December. At the moment, this comet is an obscure fourteenth magnitude object in Ursa Major which will brighten more than a magnitude during September. If it reaches naked-eye visibility, it could be visible low in the west north-western sky after sunset in the constellation of Böotes at the end of the first week of December. As it is heading towards perihelion in early January 2022, it will be getting lower in the sky as it moves towards the Sun.
If you want to look for the International Space Station (ISS) as it passes over your location, please have a look at the predictions page on the Heavens Above web site. Choose your observing location in the Configuration section and then select ISS in the Satellites section. The ISS is at least as bright as a first magnitude star and can approach the brightness of Venus under favourable conditions. Similarly, if you want to look for the core module of the new, third generation Chinese space station, Tianhe-1, predictions for this 'under construction' space station can be found on the Heavens Above web site. This module, the first of three parts, was launched on Thursday April 29th 2021. Tianhe-1 is significantly fainter than the ISS, normally about as bright as a third of fourth magnitude star. Predictions for other satellites may also be obtained from the Heavens Above web site.
The above image is a 30 minute forecast of the location and probability of auroral activity based loosely on a model developed at Johns Hopkins' Applied Physics Laboratory known as the Ovation Aurora Forecast model. It provides estimates of the energy per unit area on the Earth's atmosphere from observations of the solar wind and interplanetary magnetic field made by the Advanced Composition Explorer satellite in conjunction with empirical relationships derived from the Defense Meteorological Satellite Program. It shows where the aurora is most likely to be seen and how bright it might be. The model generates a global estimate of power, called the Hemispheric Power, deposited into the atmosphere in gigawatts (GW). For powers of less than 20GW, little or no aurora may be visible. For powers of 20-50 GW, you may need to be relatively close to the aurora to see it. For values above 50 GW, the aurora should be easily observable, active and mobile. For values above 100 GW, this is considered to be a significant storm where the aurora may be visible from hundreds of miles away. The current prediction is downloaded when you load this page. If you want to download the latest model, simply reload this page or press F5. If you want to see the full-sized map, please click on the above image.
The above sky chart, generated from the Heavens-Above.com web site, shows what the night sky looks like at 22:00 BST on Saturday October 16th 2021 from York. The night sky will look the same an hour later at 23:00 BST at the beginning of the month and an hour earlier at 21:00 BST at the end of the month. Please click on the chart to see a full-sized sky chart image. If you want to generate your own star chart for another combination of location, date and time, please have a look at the Heavens Above web site. Choose your observing location in the Configuration section and then select the Interactive Sky Chart in the Astronomy section.
In October 2021, the amount of daylight (measured from sunrise to sunset) decreases from 11 hours 34 minutes at the start of the month to 9 hours 29 minutes at the end of the month. Total daylight (sunrise to sunset) for the month is 325 hours 51 minutes.
start and end times of civil, nautical and astronomical twilights.
|h m||h m||h m||h m||h m|
|** ** No phenomenon on that day|
|PLEASE NOTE: These times are in Greenwich Mean Time (GMT) except between 01:00 GMT on March 28th and 01:00 GMT on October 31st when the times are in BST (British Summer Time) which is one hour in advance of GMT. Times given in red are in GMT.|
Rising and setting times for the Sun, Moon and planets and times of twilights for other locations can be obtained from HMNAO's Websurf web pages using the Rise, Set and Twilight Times option.
The actual times at which the Sun will just appear, or disappear, will depend on the difference between the altitudes of the observer and the local horizon and the actual refraction, which depends on the meteorological conditions along the light path. Differences of a minute or so from the tabulated times are to be expected.
For the drivers amongst you, the 'Hours of Darkness', as defined in the Road Vehicle Lighting Regulations (1989), start half an hour after sunset and end half an hour before the following sunrise. Headlights should be used during the Hours of Darkness and sidelights in the half hour periods after sunset and before sunrise. These timings can also be obtained from HMNAO's Websurf web pages using the Rise, Set and Twilight Times option.
For the pilots amongst you, night, according to Statutory Instrument 2016 No. 765, The Air Navigation Order 2016, Schedule I (Interpretation), Article 2, means 'the time from half an hour after sunset until half an hour before sunrise (both times inclusive), sunset and sunrise being determined at surface level'. In other words, the night time period starts at the beginning of the Hours of Darkness and finishes at the end of the Hours of Darkness. In the United States, the Federal Aviation Administration (Federal Aviation Regulations, Section 1.1) defines night as the time between the end of evening civil twilight and the beginning of morning civil twilight as published in the American Air Almanac, converted to local time. Sunset to the following sunrise can also be defined as night in the United States as well as one hour after sunset to one hour before sunrise. By the way, flying in a total eclipse of the Sun does not count as night flying!