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 on the right.
This web page can also be accessed from outside the UK Hydrographic Office on http://astro.ukho.gov.uk/nao/taunton.html.
On this day, the Sun crosses the celestial equator moving southwards and the approximate length of night and day are the same. The word "equinox" is derived from the Latin words "aequus" meaning equal and "nox" meaning night. The number of daylight hours will continue to decrease until we reach the minimum amount of daylight at the northern hemisphere Winter Solstice on Thursday December 21st at 16:28 GMT. Please click on the image above to see a larger version of the diagram demonstrating the occurrence of solstices and equinoxes.
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 only one active region on the Earth-facing hemisphere of the Sun. AR2680 is stable and incapable of generating significant solar flare activity. The complex active region AR2673 has crossed over the western limb. This active region produced a major X8.2 solar flare on Sunday September 10th at 16:06 UT. Ultraviolet and X-ray radiation from the flare ionised the top of the Earth's atmosphere causing a short-wave radio blackout over most of the Americas and eastern Africa. A second, more significant, blackout over both Poles lasted two days. A moderate S2-class solar radiation storm lasted about three days after Sunday's X8.2 flare. This radiation storm was composed of solar protons which can increase the radiation risk to passengers in high-flying aircraft, cause single-event upsets in satellite operations and interfere with high-frequency propagation of radio signals. Normally, the Earth's magnetic field protects us from solar radiation storms. In rare cases, large surges in radiation reaching the Earth's surface can cause a "Ground Level Event" (GLE). A small GLE occurred on September 10th/11th, one of only seventy three to be detected since 1942. It is possible that passengers on planes flying in polar regions at 40,000 feet may have doubled their normal radiation exposure and the aircraft themselves could have experienced minor upsets to on-board electronics and avionics. A coronal hole now occupies a significant fraction of the northern hemisphere of the Sun. Solar winds emanating from this feature delivered a glancing blow to the Earth's magnetic field around midnight on September 12th/13th producing minor G1-class geomagnetic storms and active but short-lived auroral displays, particularly in Iceland. The possibility of moderate G2-class geomagnetic storms is possible when an independent solar wind stream arrives on September 14th. 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 September 2017 are as follows:
Full Moon – Wednesday September 6th at 08:03 BST
Last Quarter – Wednesday September 13th at 07:25 BST
New Moon – Wednesday September 20th at 06:30 BST
First Quarter – Thursday September 28th at 03:54 BST
The Moon is at perigee (closest to the Earth) on Wednesday September 13th at 17:06 BST when it is 369,860km from the Earth. It is at apogee (furthest from the Earth) on Wednesday September 27th at 07:50 BST when it is 404,348km from the Earth.
On Tuesday September 12th, 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 the Hawaiian Islands, northernmost parts of Mexico, most of North America except north-western Canada and Alaska, and the Azores. This occultation is not visible from the United Kingdom.
There are four occultations by the Moon on Monday September 18th. Sadly, none of them are visible from the United Kingdom. However, it will mean that the very thin waning crescent Moon will be quite close to Mercury, Venus, Mars and Regulus in the early hours of September 18th around the start of nautical twilight (05:40 BST). All the objects will be in the east north-eastern sky; Mercury (−1.0) and Mars (+1.8) will be about three degrees above the horizon whereas the waning crescent Moon, Regulus (+1.4) and Venus (−3.9) will be ten to twelve degrees above the horizon.
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 had 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 was 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 were within a day's drive of the path of totality of this eclipse. It must rival the popularity of the August 11th 1999 total eclipse of the Sun seen over Europe, south-western Asia and India.
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 occurred on Monday August 7th 2017 which was visible from the western Pacific Ocean, Oceania, Australasia, Asia, Africa, Europe and the easternmost tip of South America. This shallow partial eclipse was visible from the United Kingdom during its final penumbral stage from 20:19 BST to 21:53 BST. From Taunton, the eclipse was visible as a penumbral eclipse from moonrise at 20:40 BST to the end of the penumbral stage at 21:53 BST.
A total eclipse of the Sun occurred on Monday August 21st 2017 which was 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 started 2600km north-west of the Hawaiian Islands and made landfall over the United States mainland on the Oregon coast between Depoe Bay and Lincoln City. It then passed 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 ended 1200km south-west of Dakar in Senegal. The maximum duration of totality, 2m41s, occurred approximately 10km south-east of Makanda in Illinois. A more detailed map of the United States showing the path of totality and local circumstances for a number of locations is available.
This eclipse was also visible at sunset from the United Kingdom as a very small partial eclipse (see the diagram above). From Taunton, the eclipse started at 19:40 BST, reached maximum eclipse (4.7% obscuration) at 20:06 BST and ended at 20:31 BST, 10 minutes after sunset. The eclipsed part of the Sun set at 20:17 BST from Taunton.
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 visible low in the morning twilight sky for its best morning apparition of the year for northern observers in the first four weeks of September. It rises in the eastern sky during morning nautical twilight and brightens from magnitude +1.9 at the start of the month to magnitude −1.3 by the end of September. Mercury reaches greatest western elongation on Tuesday September 12th. It is 0.6° south of Regulus on Sunday September 10th, 0.06° north of Mars on Saturday September 16th and 0.03° north of the waning crescent Moon on Monday September 18th (an occultation centred on the Pacific Ocean).
Venus is still a prominent object low in the morning twilight sky having risen in the north-eastern sky more than an hour before the start of morning nautical twilight. It remains at magnitude −3.9 throughout the month. Venus lies 0.5° north of the waning crescent Moon on Monday September 18th (an occultation centred on Australia) and lies 0.5° north of Regulus on Tuesday September 19th.
Mars reappears low in the eastern morning twilight sky in mid-September in the constellation of Leo, initially rising at the start of morning nautical twilight but getting earlier as the month progresses. It lies 0.06° south of Mercury on Saturday September 16th and 0.1° south of the waning crescent Moon on Monday September 18th (an occultation centred on the Pacific Ocean).
Jupiter is briefly visible in the western evening twilight sky, setting at the end of nautical twilight at the start month and at the end of civil twilight by the end of September. It lies in the constellation of Virgo for the whole of September remaining at magnitude −1.7. Jupiter lies 3° north of Spica on Tuesday September 5th and 4° south of the waxing crescent Moon on Friday September 22nd.
Saturn rises in the south-eastern sky well before sunset and can be seen low in the southern sky in the mid-evening. It fades slightly from magnitude +0.4 at the start of the month to +0.5 at the end of September as it travels through the eastern part of the constellation of Ophiuchus. Saturn lies 3° south of the waxing crescent Moon on Wednesday September 27th.
Uranus rises in the eastern sky in the mid-evening as it moves towards opposition on Thursday October 19th. It lies in the constellation of Pisces close to the 4th magnitude star Omicron Piscium. Uranus is a magnitude +5.7 blue-green object visible with binoculars. This planet can also be glimpsed with the naked-eye under optimum conditions.
Neptune rises in the eastern sky in the early evening and reaches opposition on Tuesday September 5th. It lies in the constellation of Aquarius close to the 4th magnitude star Lambda Aquarii. Neptune is a magnitude +7.8 object visible with good binoculars under optimum conditions. However, it can be difficult to distinguish Neptune from other stellar objects of a similar magnitude.
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 twilight itself. In the photograph, the Zodiacal Light is on the left and the Milky Way is on the right. For Taunton, astronomical twilight starts in the morning at around 04:25 BST at the beginning of the month and at 05:20 BST 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.
There are no significant meteor showers active during September. The next shower exhibiting moderate numbers of fast meteors with long trains is the Orionids at the end of the third week of October. Further information 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. Extremely bright meteors or "bolides" can also be seen occasionally. Typically, these objects are as bright as or brighter than a full moon. A recent example of such an object was seen over the West Country, Wales and the West Midlands on Monday June 30th 2014 at 03:04 BST. They can also be seen in daylight such as the example observed in Bangkok on Monday September 7th 2015.
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 2012.
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.
The brightest comets currently visible in the night sky require a small telescope to see them. However, there is one object which has been discovered recently which may come to prominence later in the year. C/2017 O1 was discovered on Wednesday July 19th 2017 by the All-Sky Automated Survey for Supernovae program. It is expected to reach perihelion in mid-October when it will be a seventh magnitude object some 0.7au from the Earth. For most of September, it lies in the constellation of Taurus moving into Perseus for the last three days of the month. It is currently a magnitude 8.5 object visible with binoculars reasonably high in the south-eastern sky before the start of morning astronomical twilight.
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. It 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 Friday September 15th 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. If you want to generate your own star chart for Taunton for another date and/or time please follow this link
In September 2017, the amount of daylight (measured from sunrise to sunset) decreases from 13 hours 32 minutes at the start of the month to 11 hours 41 minutes at the end of the month. Total daylight (sunrise to sunset) for the month is 378 hours 17 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.
The actual times at which the Sun will just appear, or disappear, will depend on the difference of the heights of the observer and the 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 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.