Russell Eberst's Sky View

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October 2017

The month of October sees the Sun moving rapidly south, leaving the northern hemisphere at the time of the autumnal equinox. With the longer nights there are more hours of darkness, when observing the night sky can be undertaken. However, temperatures are dropping, and the real test of dedication comes with the onset of night frosts. Although the stars of summer are still visible, with the "Summer triangle" (consisting of Vega, Deneb and Altair) being located in the western sky after dusk, the really obvious constellations such as Pegasus, Andromeda and Cassiopeia are the ones that dominate the sky at this time of year. Also becoming better placed for studying are Autumn constellations such as Perseus, Aries and Triangulum. The latter constellation does not contain any really bright stars, The brightest (beta Triangulum) being only magnitude +3. However, it does contain an interesting galaxy, known as M33. A large spiral, this galaxy is the 33rd entry in Messier's catalogue of non-stellar objects, and is therefore known by the rather prosaic name of M33. Another entry in Messier's catalogue is M31. It is also better known as the "Andomeda galaxy", since it lies within the boundary of the constellation of Andromeda. This is the nearest large galaxy to our own Milky Way. Some 2.5 million light-years distant, it is the most distant object that is visible to the unaided eye. The brightest planet is Venus which is to be found in the eastern sky before dawn. On the mornings of October and 6, Venus acts as a guide to finding Mars. The two planets are less than 0°.5 apart and both are close to the star sigma Leonis, in the eastern part of Leo, the mighty Lion. The Moon passes Mars on October 17 and Venus on October 18.

The planet Saturn is coming to the end of its evening apparition, but can be found below and to the right of the crescent Moon on the evening of October 24. Its low elevation is somewhat compensated by the fact that its rings are at their maximum opening. The lack of bright planets in the evening sky may persuade observers to attempt observing the outer planets Uranus and Neptune, both being interesting this month. Uranus is at opposition on October 19, so visible all night and at its closest to the Earth. At magnitude +5.7, it is theoretically visible to the unaided eye, but only under ideal conditions. Binoculars or a telescope will show it as a small bluish point that shows its identity by moving slowly westwards each night. Neptune will attract attention on October 5-6 when its largest moon, Triton will occult (or hide) a star in the constellation of Aquarius. A comparatively rare phenomenon, the occultation will enable studies to be carried out, with investigation of the moon's atmosphere as to its extent and composition. The event takes place at around 23.48 U.T. on October 5 and is well placed for U.K. observers. The star is known as UCAC4 410-143659, whose light will pass through the moon's atmosphere and reveal which gases are present. Although the majority of stars remain constant in brightness, there are a sizeable number of variable stars. One well-known variable is chi Cygni, to be found within the 'Summer triangle' mentioned above. Its magnitude varies from as faint as +14 to a maximum of about +4. This is equivalent to a factor of 10,000 in brightness. During October it is expected to reach its next maximum, probably at magnitude +5 or so. Another variable worth monitoring is R Coronae Borealis. In the Northern Crown (Corona Borealis), this enigmatic object has remained very faint for several years, but is now recovering in brightness and may attain magnitude +6 or brighter. It is visible in the West in the evenings and in the East before dawn.

At the beginning of September, the Earth experienced a close pass by the asteroid 3122 Florence. Observed by many astronomers both amateur and professional, the minor planet was found to possess at least two small moons. Since Florence itself is named after the famous nurse Florence Nightingale, I like to refer to the moons as Edith and Elsie. On October 12, the Earth can expect another close encounter, this time with a tiny asteroid known as 2012 TC4. Its estimated diameter is only 16 metres, but it will close to within 49,000 km (31,000 miles) of the Earth. That's only one-eighth of the Moon's distance. There is no danger of a collision with the Earth. The Earth has other problems, including the enormous amount of junk or debris that now orbits high above us. In the sixty years that have passed since the beginning of the space age when the first Sputnik was launched into orbit on October 4, 1957, the number of objects in Earth orbit has grown to many millions. About 25,000 of these are trackable from Earth's surface, but the vast majority are too small to be detected. All this detritus results from more than 5000 launches into orbit. Satellites are involved in so many different facets of life that it is difficult to recall what it was like before this resource was available. These artificial satellites have improved areas such as Communications, Navigation, Mapping, Search and rescue, Agriculture and horticulture, Meteorology and Astronomy. The military authorities have not been slow to utilise the capabilities of orbital satellites, keeping surveillance on friend and foe. Very little of this was predicted prior to 1957, and we have difficulty foreseeing what the next sixty years will bring. It is easier to predict that clocks will be put back on hour on Sunday, October 29 at 2 a.m. British Summer Time.

Moon phases:

  • Full Moon: October 5
  • Last Quarter: October 12
  • New Moon: October 19
  • First Quarter: October 27

Sky View Image

The maps show the sky at 23:00 BST on the 1st, 22:00 BST (21:00 GMT) on the 16th and at 20:00 GMT on the 31st. Summer time ends at 02:00 BST on the 29th when clocks are set back one hour to 01:00 GMT.