The night sky in October 2015

posted 30 Sep 2015, 07:44 by Pete Collins
by Anne Holt

Sunset  1 Oct - 18.46    31 Oct - 16.38 (after the clocks go back)

The clocks go back in the early hours of Sunday 25th, after which it will not only go dark at a reasonable hour, we will also have the sun at its highest point in the sky at noon - which is how it should be.

Highlights of the month - 4 planets and the Moon visible close together in the pre-dawn sky, and the Orionid meteor shower. See below.

Constellations

The Summer Triangle, made up of Vega in Lyra, Deneb in Cygnus and Altair in Aquila, is losing its dominance in the night sky.  It is still visible during the first part of October high in the south west but by the end of the month all three constellations will have set by 4am. It's place in the southern sky is being taken by the Great Square of Pegasus, autumn's signature constellation.

The beautiful star cluster the Pleiades (also known as the Seven Sisters) followed by the rest of Taurus, will be visible by 11pm in early October and by 8pm (now back to GMT) at month end.

On 29th, Aldebaran- the eye of the bull in Taurus - will be occulted by the moon between 21.45 and 22.44.

By the end of October Orion will be easily visible by midnight, with Sirius just above the eastern horizon at this time.

Perseus and Andromeda are still high in the sky for most of the night, making it a good time to look for M31, the Andromeda galaxy.   If you are at a very dark sky site, it should be visible to the naked eye, especially when using averted vision.

Cassiopeia is now high in the sky for most of the night, so the Plough, on the opposite side of the North Celestial Pole, is low in the north.

Planets

Planetary observing this month favours those who like to get up early, as most of the planets are now morning objects.

Exceptions are:

Saturn:  in Libra,  mag 0.6. Now setting soon after the sun.  Might be visible in the twilit sky in early October

Uranus:  in Pisces,  mag 5.7. Visible throughout the night - if you have perfect eyesight and are at a dark sky site, otherwise binoculars will be needed.  An amateur telescope should show its blue/green disc. It is at opposition on 12th, sets around 5am by month end.

Neptune:  in Aquarius,  mag 7.8. Throughout October, it reaches its highest point due South while the sky is still dark.  In the early evening of 23rd, it is just 2 degrees below the waxing gibbous moon and should be visible in amateur scopes.

There's quite a party going on in the pre-dawn sky in Leo this month, with several planetary close encounters - Venus, Jupiter and Mars, also Mercury from the 2nd week in the month, and the Moon joins in too 8 to 11 Oct.

Venus:  mag -4.4. Unmissable in the morning sky, brighter than everything except the Sun and Moon, rising 4 hours before the sun at the start of the month.  By month end this will have increased to 4 1/2 hours and it will have brightened even more to -4.5. On 26th it will be separated by just 1 degree from Jupiter.

Mars:  mag 1.8. Not much detail will be seen through a scope this month as the planet is currently quite distant from Earth. Separated from Jupiter by less than half a degree on 18th, and from Venus by one degree on 31st.

Jupiter:  mag -1.8. Second only to Venus in brightness in the morning sky - albeit not a very close second.  At the start of October it rises around 4.30, by month end it will reachan altitude of 30 degrees before the sky begins to brighten.

Mercury, in Virgo, mag 1.4. Making its best showing of the year this month, should be visible in the dawn sky from the second week of the month, on 8th it rises 90 minutes before the sun.  Greatest Western elongation is on 15th, by which time it will have brightened to -0.5.  By month end it will be at -0.9. Despite its brightness it is not too easy to spot in the brightening pre-dawn sky

Minor planet Vesta reaches opposition on 3rd, in the constellation of Cetus.  At mag 6.1 it is unlikely to be visible to the naked eye - unless you have eyes like a hawk and are in the middle of nowhere.

For the exact position of Vesta, and the other planets, comets and larger asteroids, see  theskylive.com

Meteor Showers

One (fairly) major and several minor showers, this month.

Orionids: Dust particles from Halley's Comet, there may be a few around from early October to early November, but the peak night is 21st/22nd,  ZHR 25, occasionally much higher.  Fast moving meteors, some leaving trails, could also be a few fireballs. Best viewed between midnight and dawn.  The waxing gibbous moon sets just before midnight on 21st, so won't interfere.

Minor showers -

Camelopardids: peak 5/6th.   ZHR 1 but occasionally much higher.

Draconids:  max 8/9th,  ZHR 2 - often higher but many are so faint they can only be detected using radar.   This shower is unusual in that it is best seen before midnight, when the radiant is high in the sky.

Epsilon Geminids: Peak Oct 18/19th;  ZHR 3,   fast moving meteors.

Leonis Minorids:  Peak 22nd/23rd ZHR 2,  fairly fast.

Southern Taurids: Peak 10th,  ZHR 5. Slow moving but very bright, again could include fireballs.  Best time to look for these is around midnight.
There is an an associated shower, the Northern Taurids.  This does not peak until November but there could be some activity in late October. This also can include fireballs, sometimes called the Hallowe'en fireballs. It is thought that these were originally the same shower but have become separated, over thousands of years, by the gravitational influence of Jupiter. Probably related to comet Encke but not directly,  both thought to be  remnants of a larger, much earlier comet which broke up.
Comments