This page provides some astronomical information on a monthly basis for those of you living in the Taunton area. Timings are in BST (British Summer Time) unless otherwise noted. Latest additions or updates are highlighted with a red border.
This month we have sections on:
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. 104 for 2017. This is a pdf document for which a document reader can be downloaded by clicking on the Adobe Reader icon above.
This web page can also be accessed from outside the UK Hydrographic Office on http://astro.ukho.gov.uk/nao/taunton.html.
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 satellite.
There is one small active region on the Earth-facing hemisphere of the Sun's disk. This sunspot does not have the energy to generate significant solar flare activity. There are no coronal holes on the visible hemisphere of the Sun. However, a coronal mass ejection was observed on Tuesday May 23rd which may make a glancing impact with the Earth on Friday May 26th generating some geomagnetic activity and polar aurorae. A very large "hedgerow" prominence can also be seen on the western limb of the Sun. It is about 30,000km in height and approximately 400,000km in length and resembles several bushes in a hedgerow; put more scientifically, hot plasma is being held aloft by unstable solar magnetic fields. Overall solar activity is still 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 this solar maximum is more complex than had been previously predicted. The maximum is 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 are significantly down on the predictions made for this maximum — indeed solar cycle 24 may be the weakest in the last 100 years or so i.e. since solar cycle 14. Assuming the start of 2014 was the beginning of the post maximum phase of solar cycle 24, we are now well into the decreasing phase of activity where individual energetic events can spawn some of the most powerful flares and coronal mass ejections of the cycle. The so-called Carrington event of 1859 is a good example of just what might be expected from this type of violent outburst. The next solar minimum, characterised by periods of many days without sunspots and flare activity, may occur in 2019 or 2020. It is likely to be a deep minimum with long periods without much sunspot or flare activity.
The sequence of Moon phases for this month and their designations are shown in the following animation:
Moon phases specific to May 2017 are as follows:
First Quarter – Wednesday May 3rd at 03:47 BST
Full Moon – Wednesday May 10th at 22:42 BST
Last Quarter – Friday May 19th at 01:33 BST
New Moon – Thursday May 25th at 20:44 BST (Lunation 1168)
The Moon is at apogee (furthest from the Earth) on Friday May 12th at 20:51 BST when it is 406,210km from the Earth. It is at perigee (closest to the Earth) on Friday May 26th at 02:22 BST when it is 357,207km from the Earth.
The combination of the Moon being at perigee and the phase of the Moon being either new or full as it is towards the end of May leads to "perigean spring tides" i.e. spring tides with a tidal range somewhat higher than those of normal spring tides.
On Thursday May 4th, the Moon continues its current series of occultations of Regulus, the blue-white first magnitude star in the constellation of Leo. This occultation is visible from Malaysia, most of Indonesia, the southern half of New Guinea, Australia, New Caledonia, New Zealand and the Chatham Islands. This occultation is not visible from the United Kingdom.
On Wednesday May 31st, the Moon occults Regulus for the second time this month. This occultation is visible from north-eastern Brazil, Cape Verde Islands, central and southern Africa except the south-western part of South Africa, Madagascar, Reunion and Mauritius. This occultation is not visible from the United Kingdom.
Please follow the New Moon link above to take part in our Crescent Moon Watch program which involves sighting the new crescent moon as early as possible after the instant of New Moon.
If you want to know what the Moon looks like now, try this USNO page generated by our colleagues in the Astronomical Applications Department at the US Naval Observatory in Washington.
There are four eclipses in 2017, the first of which occurred in February as a deep penumbral eclipse of the Moon which was visible in its entirety from the United Kingdom. The second eclipse of February, an annular eclipse of the Sun, was not visible from our shores. We have a very brief glimpse of the final penumbral stages of a partial eclipse of the Moon at moonrise early in August. The last eclipse of the year is a total eclipse of the Sun visible principally from the United States. It is interesting to note that as many as 250 to 300 million people will be within a day's drive of the path of totality of this eclipse.
A penumbral eclipse of the Moon occurred on Friday February 10th-Saturday February 11th 2017 which was visible from western Asia, Africa, Europe, Greenland, the Americas and parts of the Pacific Ocean. This deep penumbral eclipse was visible from the United Kingdom starting at 22:32 GMT on February 10th and ending at 02:55 GMT on February 11th. Penumbral eclipses of the Moon involve very subtle changes in brightness and can be difficult to observe. From Taunton, the whole eclipse was visible.
An annular eclipse of the Sun occurred on Sunday February 26th 2017 which was visible as a partial eclipse from the south-eastern Pacific Ocean, the southern half of South America, the south Atlantic Ocean, most of Antarctica and Africa except the northern part. The path of annularity started 1800km south of Easter Island and crossed southern parts of Chile and Argentina, the Atlantic Ocean, central Angola, the north-western tip of Zambia and ended over the southern part of the Democratic Republic of Congo, 100km north west of Lubumbashi. The minimum duration of annularity was 0m44s over the mid-south Atlantic Ocean. The eclipse was not visible from the United Kingdom.
A partial eclipse of the Moon occurs on Monday August 7th 2017 which is visible from the western Pacific Ocean, Oceania, Australasia, Asia, Africa, Europe and the easternmost tip of South America. This shallow partial eclipse is visible from the United Kingdom during its final penumbral stage from 20:19 BST to 21:53 BST. From Taunton, the eclipse is briefly visible from moonrise at 20:40 BST to the end of the penumbral stage at 21:53 BST.
A total eclipse of the Sun occurs on Monday August 21st 2017 which is visible as a partial eclipse from the Hawaiian Islands, the north-eastern Pacific Ocean, Oceania, North and Central America, northern parts of South America, the westernmost tip of Europe and West Africa. The path of totality starts 2600km north-west of the Hawaiian Islands and makes landfall over the United States mainland on the Oregon coast between Depoe Bay and Lincoln City. It then passes over northern Oregon, southern Idaho, the extreme south-western tip of Montana, central Wyoming, Nebraska, north-eastern Kansas, the south-western tip of Iowa, Missouri, southern Illinois, western Kentucky, eastern Tennessee, north-eastern Georgia, western North Carolina and South Carolina leaving the United States mainland near McClellanville. The path of totality ends 1200km south-west of Dakar in Senegal. The maximum duration of totality, 2m40s, occurs approximately 10km south-east of Makanda in Illinois. This eclipse is visible at sunset from the United Kingdom as a very small partial eclipse. From Taunton, the eclipse starts at 19:40 BST, reaches maximum eclipse (4.7% obscuration) at 20:06 BST and ends at 20:31 BST, 10 minutes after sunset. A more detailed map of the United States is available.
Further information on all the eclipses in 2017 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, 2018, are also available.
Mercury rises close to the start of morning civil twilight in the eastern sky for the whole of May, being significantly better-placed for southern hemisphere observers this month. It is at greatest western elongation on Wednesday May 17th. Mercury brightens from magnitude +2.5 at the start of the month to magnitude −0.3 by the end of the month. It lies 1.6° north of the waning crescent Moon on Wednesday May 24th.
Venus is a prominent object low in the morning twilight sky, rising almost due east around the start of morning nautical twilight. It fades somewhat from magnitude −4.7 at the start of the month to magnitude −4.5 at the end of the month. Venus gets slightly higher in the twilight sky as the month progresses as it moves towards greatest western elongation on Saturday June 3rd. It lies 2° north of the waning crescent Moon on Monday May 22nd.
Mars can be seen low in the west north-western sky towards the end of evening nautical twilight, setting in the late evening in the north-western sky. It lies in the constellation of Taurus for the whole of the month, fading slightly from magnitude +1.6 at the start of the month to magnitude +1.7 at the end of May. Mars lies 6° north of Aldebaran on Sunday May 7th and 5° north of the waxing crescent Moon on Saturday May 27th.
Jupiter rises in the eastern sky well before sunset and is visible for most of the night, setting in the western sky close to the start of morning nautical twilight. It lies in the constellation of Virgo remaining there for the whole of May. Jupiter fades slightly from magnitude −2.4 at the start of the month to magnitude −2.3 at the end of May. Jupiter lies 2° south of the waxing gibbous Moon on Sunday May 7th.
Saturn rises in the south-eastern sky before midnight and lies low in the southern sky at the start of morning nautical twilight. It brightens noticeably from magnitude +0.3 at the start of the month to +0.0 at the end of the month. It moves in a retrograde manner from the constellation of Sagittarius to Ophiuchus on Thursday May 18th. Saturn lies 3° south of the waning gibbous Moon on Saturday May 13th.
The Eta Aquariids are active between April 19th and May 28th, peaking around May 5th and 6th. They are best seen in a short window as the radiant rises above the eastern horizon in the pre-dawn sky at the end of the first week of May. It has to be said that the peak of this shower is more of an extended plateau of activity lasting several days centred on the maximum. This shower exhibits a variable rate of around 30-40 meteors per hour, occasionally peaking as high as 60 meteors per hour. The shower is relatively unaffected by moonlight as the waxing gibbous Moon sets in the latter part of the night. It is more likely to be affected by the increasing morning twilight glow. The meteors are often swift and bright with long, persistent trains. This shower is loosely connected with Comet 1P/Halley, having separated from the comet hundreds of years ago.
No other significant meteor showers are active this month, Further information on these and other meteor showers occurring during 2017 can be found at the International Meteor Organization web site.
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.
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 summary of the comets that may be accessible to northern observers with binoculars.
Comet C/2017 E4 Lovejoy has now faded beyond 10th magnitude and is likely to continue fading due to the fact that it is probably disintegrating. It is likely to disappear from our skies around the beginning of the second week of May whilst moving from the constellation of Triangulum to Aries.
Comet 41P/Tuttle-Giacobini-Kresak starts the month at nearly eighth magnitude in the northern constellation of Hercules. It crosses into Lyra on May 3rd remaining there for around two weeks. It then moves back into Hercules for the rest of May fading as it does so to around 11th magnitude, beyond the reach of average binoculars.
Comet C/2015 ER61 PANSTARRS starts the month in Pisces at magnitude 7.5. It disappears into the morning twilight glow for observers at our latitudes, becoming a southern hemisphere object for the whole of May.
Comet C/2015 V2 Johnson starts the month as a ninth magnitude object in the constellation of Hercules. On May 3rd, it moves into the constellation of Boötes where it remains for the rest of May. C/2015 V2 has both an ion tail of material blown away by the solar wind and a dust tail following along in its orbital path. It appears somewhat greenish in colour due to diatomic carbon in its nucleus. It should brighten to around eighth magnitude by the end of the month and will be closest to the Earth on Monday June 5th at a distance of 0.811au. The comet will reach perihelion on Monday June 12th when it is expected to reach seventh magnitude. It is visible throughout the night high in the eastern and southern parts of the sky for the whole of May.
Strictly speaking, this phenomenon is an atmospheric one rather than a truly astronomical one. Nonetheless, living in the United Kingdom, we are well placed to see this unusual spectacle during the shorter nights of the summer months, particularly in June and July.
These tenuous cloud-like structures are composed of ice-coated particles at an altitude of around 80km in the mesosphere, approximately four times higher than the limiting altitude of cirrus cloud. Created by water vapour freezing around meteor smoke in the upper atmosphere, their altitude means that they appear silvery-blue in colour against the darker twilight sky when the Sun lies between 6° and 16° below the horizon.
Noctilucent or "night shining" Cloud is normally seen between 10° and 20° above the northern horizon exhibiting a range of forms — perhaps the most common is the "herring-bone" pattern. Normal visibility limits are mid-May to mid-August, peaking around the time of the Summer Solstice. More information, including the facility to report your sightings, can be found at the Noctilucent Cloud Observers' Homepage.
A word of warning; displays are unpredictable and more frequently seen from the northern half of the United Kingdom. Nevertheless, observations have been submitted by observers living in this locality e.g. from Exeter and Castle Cary.
Maps constructed from AIM satellite imagery showing the current positions of Noctilucent Clouds stopped in late February 2017 due to a satellite repositioning exercise. It is hoped that they will resume at the end of May.
A particularly nice animation of this phenomenon taken before dawn on June 3rd 2013 by The Sky at Night's Pete Lawrence is well worth a look. A photograph demonstrating that these clouds can be seen from southern parts of the United Kingdom was taken by D. Tate in Castle Cary in the early hours of June 10th 2013.
If you want to look for the International Space Station (ISS) as it passes over Taunton, please have a look at this page on the Heavens Above web site. The ISS is at least as bright as a first magnitude star and can approach the brightness of Venus. Similarly, if you want to look for the Chinese space station, Tiangong-1, have a look at this page. It has been known for some time now that Tiangong-1 will re-enter the Earth's atmosphere in an "uncontrolled manner" late in 2017. Tiangong-1 is significantly fainter than the ISS, normally as bright as a third or fourth magnitude star. Information for Tiangong-2, the latest Chinese addition to the space stations orbiting the Earth, can be found on this page. It is of a similar brightness to the larger Tiangong-1. Predictions for other satellites may also be obtained from the Heavens Above web site.
Another satellite-related phenomena to look out for are the so-called "Iridium flares". These bright flashes of sunlight reflecting off the Iridium series of communication satellites can be seen at night and also occasionally during the daytime if they are bright enough. Predictions for the next seven nights are available.
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 and shows where the aurora is most likely to be seen and how bright it is likely to 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 20-50GW, you may need to be relatively close to the aurora to see it. For values above 50GW, the aurora should be easily observable, active and mobile. For values above 100GW, 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 hit 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 Tuesday May 16th 2017 from Taunton. 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 Taunton for another date and/or time please follow this link
In May 2017, the amount of daylight (measured from sunrise to sunset) increases from 14 hours 48 minutes at the start of the month to 16 hours 13 minutes at the end of the month. Total daylight (sunrise to sunset) for the month is 482 hours 47 minutes.
start and end times of civil, nautical and astronomical twilights.
|h m||h m||h m||h m||h m|
|** ** No phenomenon that day|
|PLEASE NOTE: These times are in Greenwich Mean Time (GMT) except between 01:00 GMT on March 26th and 01:00 GMT on October 29th when the times are in BST (British Summer Time) which is one hour in advance of GMT.|
The timings in the table above should be accurate to within 1-2 minutes inside the red circle superimposed on the map shown on the left.
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.
For the drivers amongst you, the "Hours of Darkness", as defined by 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 VFR (Visual Flight Rules) pilots amongst you, night, according to Statutory Instrument 2009 No. 3015, Civil Aviation, The Air Navigation Order 2009, Part 33 (Interpretation), Article 255(1), 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 period starts at the beginning of the Hours of Darkness and finishes at the end of the Hours of Darkness.