The sky in October

Messier 110 or M110 (figure 1), the brightest satellite galaxy of the Andromeda galaxy (M31) will be an interesting sight and it is due to be in a good position for viewing. It will be at its best visibility and highest point in the sky around midnight on the 1^st of October.

It will be first visible at approximately 20:14 BST above the Eastern horizon. It will fade at approximately 06:00 above the Western horizon.

M110 will be extremely faint to the eye, however, it will be visible through a good pair of binoculars or a small to medium sized telescope (4 inch or better).

Figure 1. Andromeda galaxy (M31) with M110 to the bottom right of the centre. Credit: ATLAS image/NASA/Caltech/NSF

M110 is also known as NGC (New General Catalogue) 205, it contains dust and shows signs of recent star formation which is not normal for dwarf elliptical galaxies in general. M110 is a distance of approximately 2.69 million light years away.

Also on the 1^st and 2^nd October M31 (Andromeda galaxy) (figure 2) is obviously in a good position for viewing. It will be in view from approximately 20:10 BST until about 06:00, again starting in the East and finishing in the West. Andromeda will be extremely difficult to see without the aid of a good telescope or pair of binoculars. If the observation surroundings are completely dark then it will enhance viewing.

Figure 2. Andromeda galaxy viewed by NASA’s wide field infrared survey explorer.

On the 2^nd  October, closer to home the moon will be in last quarter (figure 3), it will be dominant in the dawn sky, rising at approximately 23:00 BST, 8 hours ahead of the Sun, it will fade from view as dawn is breaking at about 06:55.

Figure 3. Moon in last quarter.

The 3^rd October, NGC 253 (figure 4), the sculptor galaxy may just be visible with the aid of a good telescope or powerful pair of binoculars. It will not rise more than 13° above the horizon, so will not be readily observable. NGC 253 will be be quite faint and not visible to the unaided eye.

Figure 4. NGC 253, sculptor galaxy.

NGC 253 is a distance of 11.4 million light years away. This NASA/ESA Hubble Space Telescope image of the core of the nearest starburst spiral galaxy, NGC 253, reveals violent star formation within a region 1, 000 light-years across. A starburst galaxy has an exceptionally high rate of star birth, first identified by its excess of infrared radiation from warm dust.                    Credit: Carnegie Institution of Washington.

On 4^th October, the moon and M44 (figure 5), the Beehive cluster also known as Praesepe (Latin for “manager”) also NGC 2632 is an open cluster in the constellation cancer, it is one of the nearest open clusters to Earth containing a larger population of stars than other nearby bright open clusters. The beehive cluster looks like a small nebulous object to the unaided eye. The astronomer Ptolemy studied it as did Galileo. It is 177 light years away.

Figure 5. M44, Beehive Cluster, just visible to the unaided eye.

The moon and M44 will be visible in the dawn sky at approximately 01:15 BST, 6 hours before the Sun. It will rise above the South Eastern horizon before fading from view as dawn breaks at about 07:00. The moon and M44 will be a little too widely separated to fit comfortably within the field of view of a telescope, but will be visible through a pair of binoculars. Figure 6 shows a night sky map for October 2018.

Figure 6. Sky map.

Friday 12^th October will see the moon and Jupiter (figure 6A), make a close approach, passing within 3°56´of each other. The moon will be two days old. The pair will be too widely separated to fit in the field of view of a telescope, however should be visible to the unaided eye or with a pair of binoculars. Figure 6A. Moon and Jupiter. Credit: RAS.

16^th October 136199 Eris (figure 7) will be observable in the constellation Cetus. Visible for most of the night, reaching highest point in the sky at approximately midnight. It will be visible between 22:00 and 04:40 from the South East to the South West. A 4 inch telescope or greater will be needed for viewing. 136199 Eris will make its closest approach to Earth (perigee) making it appear brighter and larger. This occurs because Eris lies opposite the Sun in the sky, the solar system is lined up so that Eris, Earth and the Sun form a straight line with Earth in the middle, on the same side of the Sun as Earth.

Figure 7. 136199 Eris. Credit, NASA/Hubble Space Telescope.

Thursday 18^th October will bring into view the moon and Mars (figure 8 and 9) making a close approach. They will pass within 1° 54´ of each other, the moon will be 9 days old. They will be visible in the evening sky from 18:35 BST as the dusk sky fades 14° above the South East horizon. They will then reach highest point in the sky at 20:35, 18° above the South horizon. They should be in view until approximately 23:40, when they lower to 8° over the South West horizon. They will both be in the constellation Capricornus. They will be visible to the unaided eye or through a pair of binoculars, a telescope will not have the field of view to capture both of them.

Figure 8. The moon and Mars close together.

Figure 9.

On the 21^st October the Orionid meteor shower (figure 10 and 11) will reach its maximum activity rate. Meteor activity should start around the 16^th October and last through until 30^th October. Annual meteor showers appear when the Earth moves through debris left over from comets and asteroids. Pebble sized particles collide with the Earth and burn up on entry to the atmosphere at between 70km and 100km. They seem like shooting stars.

Working out the velocity and direction at which the meteors impact the Earth, it is possible to calculate the path of the stream through the solar system and thereby identify the body responsible for causing it. The parent body responsible for creating the Orionids is Halley’s Comet.  

Figure 10. Halley’s Comet causes the Orionids. Credit, NASA/ESA/Max Planck Institute for Solar System Research.

Figure 11. Orionids, in the constellation Orion, near Betelgeuse.

Assuming dark skies, the maximum rate of meteors that can be expected is approximately 25 per hour. In practical terms the number observed is likely to be lower. From Pembrokeshire it will be more like 5 per hour. They were discovered in October 1839. Astronomer Royal (1720 – 1742), Edmond Halley discovered the comet. E. C. Herrick made observations in 1839 and 1840 about the activity present in the October sky. A. S. Herschel made the first documented record giving accurate forecasts for future meteor showers.

Uranus (figure 12 and 13) will be in a good position for viewing on the 24^th October in the constellation Aries. It will reach its highest point at about midnight. It will be visible between 20:20 and 05:35. It will rise above the Eastern horizon and disappear above the Western horizon. This optimal positioning happens when Uranus is almost directly opposite the Sun in the sky. Approximately the same time Uranus passes opposition, it also makes its closest approach to Earth (perigee) making it appear at its brightest and largest. Uranus is at a maximum distance from the Sun of 19.29 times that of the Earth. On this occasion Uranus will be at a distance of 18.87 Astronomical Units (AU). Without the aid of a telescope Uranus will look just like a point of star light. It will be positioned between constellations Aries and Pisces.

Figure 12. Uranus. Credit, NASA, Voyager 2.

Figure 13. Uranus can be found between Aries and Pisces. Credit, Galilean Satellite Information.

NGC 869 (figure 14), open star cluster will be in a position of observation on 26^th October. It can be found in the constellation Perseus (figure 13), also known as the Western half of the double star cluster. It will be at its highest point in the sky at midnight. It will be visible all night because it is circumpolar. It will be highest in the sky at 01:18, 84° above northern horizon. At dusk, it will become visible at about 19:20 (BST), 41° above north-eastern horizon. It will be lost to dawn twilight at approximately 06:41, 45° above north-western horizon. It is 7600 light years distance and is approximately 13 million years old. NGC 869 is tricky to make out with the unaided eye except from a dark site, but is visible through a pair of binoculars or small telescope. Figure 14. The Double Cluster, NGC 869 (right) and NGC 884 (left) with north to the top. Credit, NASA/Hubble.

The open star cluster NGC 884 (figure 15) in Perseus, also known as the eastern half of the double cluster will be well placed for observation on 27^th October. It will reach its highest point in the sky at around midnight local time. It is easiest to see from the northern hemisphere but cannot be seen from latitudes much south of 12°. It will be visible all night because it is circumpolar. It will be highest in the sky at 01:17, 84° above northern horizon. At dusk, it will become visible at about 19:20 (BST), 41° above north-eastern horizon. It will be lost to dawn twilight at approximately 06:42, 45° above north-western horizon.     NGC 884 is tricky to make out with the eyes except from a dark site, but is visible through a pair of binoculars or small telescope.

Figure 15. NGC 884. The Double Cluster, NGC 869 (top) and NGC 884 (bottom) with north to the left. Distance 7600 light years and approximately 12.5 million years old.

31^st October, the Moon and M44 (figure 5) will make a close approach, passing within 0°39' of each other. The Moon will be 22 days old. The pair will be visible in the morning sky, becoming accessible at around 23:25, when they rise 7° above north-eastern horizon. They will then reach highest point in the sky at 06:18, 57° above southern horizon. They will be lost to dawn twilight at about 06:46, 57° above southern horizon. They will both be in the constellation Cancer. The pair will be a little too widely separated to fit comfortably within the field of view of a telescope, but will be visible through a pair of binoculars.

Figure 16. Constellation Cancer. Moon and M44 close approach.

Warning: Never attempt to view through binoculars or a telescope an object close to the Sun. Also, never attempt to view the Sun unaided, doing so may result in immediate and permanent blindness. Always use astronomical approved viewing equipment

The Stellarium software will assist greatly in locating objects in the sky, it is a useful astronomical tool.

Mark R Smith FRAS

Physicist

Nuclear Fusion & Astrophysics