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:
The Earth reaches aphelion, the point furthest from the Sun in its orbit, on Monday July 3rd at 21:11 BST when it is 152,092,504km from the Sun.
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.
The Sun is blank for the third day in a row bringing the total number of spot-free days to forty seven for this year. A coronal hole is still covering a sizeable fraction of the northern hemisphere of the Sun's disk and the Earth is entering the solar wind stream emanating from this feature. This stream of high-velocity material (moving at around 650km/s) could bring so-called "dark sky" auroral displays to the high latitudes. These displays may or may not be visible to the naked eye but can be recorded photographically with exposures of several seconds with digital cameras using high ISO settings. Although active region AR2665 is now on the far side of the Sun, it is still very active. It unleashed a coronal mass ejection on July 20th at around 21:30 UT that was visible beyond the limb of the Sun. Overall solar activity remains at 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, characterized 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 July 2017 are as follows:
First Quarter – Saturday July 1st at 01:51 BST
Full Moon – Sunday July 9th at 05:07 BST
Last Quarter – Sunday July 16th at 20:26 BST
New Moon – Sunday July 23rd at 10:46 BST (Lunation 1170)
First Quarter – Sunday July 30th at 16:23 BST
The Moon is at apogee (furthest from the Earth) on Thursday July 6th at 05:28 BST when it is 405,934km from the Earth. It is at perigee (closest to the Earth) on Friday July 21st at 18:12 BST when it is 361,236km from the Earth.
On Thursday July 20th, the Moon continues its current series of occultations of Aldebaran, the orange first magnitude star in the constellation of Taurus. This occultation is visible from India, central and north-eastern Asia, Japan, the Aleutian Islands and the Hawaiian Islands. This occultation is not visible from the United Kingdom.
On Tuesday July 25th, the Moon occults the planet Mercury. This occultation is visible from northern Europe including the British Isles, most of Greenland, the Arctic Ocean, the northern half of Asia and Japan. This occultation is visible from the United Kingdom. From Taunton, this daylight occultation by the waxing crescent Moon is in progress at moonrise and ends at 11:15 BST. As the Sun is only 26° degrees away from the 5.6% illuminated Moon, observations of this occultation should not be attempted without specialist equipment.
On Tuesday July 25th, the Moon occults Regulus, the blue-white first magnitude star in the constellation of Leo. This occultation is visible from the northern half of Africa, the southernmost parts of Europe, the Middle East, southern India and Indonesia. 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 is just visible in the evening twilight sky but is best seen by observers in the southern hemisphere. It sets around the end of evening civil twilight and fades from magnitude −0.4 at the start of the month to magnitude +0.3 by the end of July. Mercury lies 5° south of Pollux on Monday July 3rd and is occulted by the Moon on Tuesday July 25th. It lies 1.1° south of Regulus on Wednesday July 26th and reaches greatest eastern elongation on Sunday July 30th.
Venus is still a prominent object low in the morning twilight sky after rising in the east-north-eastern sky around an hour before the start of morning nautical twilight. It fades somewhat from magnitude −4.2 at the start of the month to magnitude −4.0 at the end of July. Venus lies 3° north of Aldebaran on Friday July 14th and 3° north of the waning crescent Moon on Thursday July 20th.
Mars is too close to the Sun to be seen this month. It reaches superior conjunction on Thursday July 27th in the constellation of Cancer. It will reappear in the morning sky in mid-September.
Jupiter is visible in the west south-western sky at the start of evening civil twilight and sets in the western sky around midnight. It lies in the constellation of Virgo for the whole of July. Jupiter fades somewhat from magnitude −2.1 at the start of the month to magnitude −1.9 at the end of July. It lies 3° south of the waxing gibbous Moon on Saturday July 1st and 3° south of the waxing crescent Moon on Friday July 28th.
Saturn rises in the south-eastern sky at before sunset and can be seen low in the southern sky before midnight. It fades somewhat from magnitude +0.1 at the start of the month to +0.3 at the end of July as it moves in a retrograde manner through the western part of the constellation of Ophiuchus. Saturn lies 3° south of the waning gibbous Moon on Friday July 7th.
The South Delta Aquariids are active from Wednesday July 12th to Wednesday August 23rd and come to a maximum in the pre-dawn hours of Sunday July 30th. They are favourably aspected due to the relatively dark skies of the first quarter Moon at the end of July. The peak rate is around 15 meteors per hour but the meteors themselves can be quite faint, lack persistent trains and fireballs. They can best be seen by observers in the southern hemisphere. The Perseid meteor shower begins on Monday July 17th, although the shower does not peak until the last quarter moon period at the end of the second week of August. 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 recent well-reported example of this occurred at around 23:00 BST on Friday September 21st.
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/2015 V2 Johnson starts the month as a eighth magnitude object in the constellation of Virgo. It then moves into the neighbouring constellation of Hydra at the end of the third week in July and then into Centaurus for the last week of July. 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. The comet is expected to fade to around ninth magnitude by the end of the month. It is visible after the end of evening twilight before setting in the south-western part of the sky around midnight.
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 soon.
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.
In late May 2017, the first signs of the northern noctilucent cloud season were observed. However, the surge in sightings in June that normally occurs following the initial displays failed to materialize. This is the first time this has happen in two decades. Latest research shows that this has been due to a "heat wave" in the mesosphere, a layer 83km above the Earth's surface, where these clouds form on small particles of meteor smoke. This heat wave is coming to an end and we can expect more displays of noctilucent cloud. From a local standpoint, a photographic report of noctilucent cloud was made from Ilminster between 02:45 BST and 03:45 BST on Friday June 16th demonstrating that this elusive phenomenon can be seen from our latitudes.
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 Sunday July 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 July 2017, the amount of daylight (measured from sunrise to sunset) decreases from 16 hours 28 minutes at the start of the month to 15 hours 23 minutes at the end of the month. Total daylight (sunrise to sunset) for the month is 496 hours 18 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 after sunset and the half hour before sunrise.
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.