How to see the planets in the night sky, October 2020

Pete Lawrence reveals which planets of the Solar System are best placed for observing throughout October 2020.

How to the see planets in October 2020. Mars lies in Pisces throughout the opposition period. Credit: Pete Lawrence

Mars is at opposition this month, a time when the planet presents its best appearance through a telescope, and due to its brilliance, to the naked eye as well. Opposition occurs on 13 October, this being the time when the ecliptic longitude of the planet is 180˚ different to that of the Sun – in other words, Mars is in the opposite part of the sky to the Sun.

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However, technically the best views are to be had when Mars is closest to Earth, a position which is reached on 6 October.

In reality of course, the presentation of Mars should be excellent for the weeks running up to and from opposition.

Find out more about how to make the most of opposition in our guide How to observe Mars.

Mars is closest to Earth on 6 October, presenting a disc 22.6 arcseconds across. Credit: Pete Lawrence
Mars is closest to Earth on 6 October, presenting a disc 22.6 arcseconds across. Credit: Pete Lawrence

On 6 October, Mars will present a fully illuminated disc, 22.6 arcseconds across. Reaching its highest point in the sky around 00:40 BST (23:40 UT), a telescopic view of Mars from this time into the early hours will have the large, dark V-shaped feature known as Syrtis Major rotating into view.

Syrtis Major is placed centrally around 04:20 BST (03:20 UT) on 6 October. Mars currently has its southern pole tilted towards us and this may be seen close to the planet’s southern limb.

Between the southern edge of Syrtis Major and the southern polar cap is the giant Hellas Basin.

At the start of October, Mars shines at mag. –2.5 and appears 22.5 arcseconds across.

At closest approach on 6 October, Mars will shine at mag –2.6 as it reaches its maximum apparent diameter of 22.6 arcseconds.

By opposition on 13 October, it remains at mag. –2.6, but will have shrunk to 22.4 arcseconds.

By the end of the month, the magnitude will have decreased to –2.2 and the apparent size to 20.2 arcseconds.

The phase and relative sizes of the planets in October 2020. Each planet is shown with south at the top, to show its orientation through a telescope. Credit: Pete Lawrence
The phase and relative sizes of the planets in October 2020. Each planet is shown with south at the top, to show its orientation through a telescope. Credit: Pete Lawrence

How to see the planets in October 2020

Mars

  • Best time to see 6 October, around 00:30 BST (5 October, around 23:30 UT)
  • Altitude 43˚
  • Location Pisces
  • Direction South
  • Features Dark ‘albedo’ features, polar caps, weather
  • Recommended equipment 150mm or larger

Mercury

Mercury reaches greatest eastern elongation (25.8˚) on 1 October when it should theoretically be visible in the evening twilight, but its position is poor and it’s unlikely to be seen. Inferior conjunction occurs on 25 October.

Venus

  • Best time to see 3 October, 05:30 BST (04:30 UT)
  • Altitude 19˚
  • Location Leo
  • Direction East

Venus is a spectacular morning planet, passing east through Leo before ending up in the Bowl of Virgo. On 3 October, mag. –4.0 Venus appears close to mag. +1.3 Regulus (Alpha (α) Leonis), separated from the star by 12 arcminutes as they both rise above the east-northeast horizon at 03:20 BST (02:20 UT). At the start of October it rises 4 hours before the Sun; a scope will reveal its phase, which is 71%-lit, increasing to 81% at the month’s close.

The Moon makes its monthly visit to Venus on the morning of the 14th, when a 9%-lit waning crescent can be seen 4˚ to its northwest. On the morning of 28 October, when Venus has crossed over into Virgo, it passes 48 arcminutes to the north of Zavijava (Beta (β) Virginis).

Jupiter

  • Best time to see 1 October, 20:00 BST (19:00 UT)
  • Altitude 14˚
  • Location Sagittarius
  • Direction South

Jupiter hangs in there this month, aided by the longer nights. At the month’s start, the mag. –2.2 planet appears towards the south as the evening twilight darkens.

Although the sky appears brighter towards the end of the month when Jupiter is close to its highest point due south, the difference isn’t that great thanks to the expansion of the night-time period. A crescent Moon lies 3˚ south of Jupiter on the evening of 22 October.

Saturn

  • Best time to see 1 October 20:00 BST (19:00 UT)
  • Altitude 16˚
  • Location Sagittarius
  • Direction South

Saturn currently appears close to Jupiter in the sky, 7.4˚ east and slightly north of it on 1 October, and 5.2˚ east and slightly north on 31 October. Saturn shines with an off-white colouration at mag. +0.8 on 1 October, dimming to +0.9 by 31 October. Its rings are tilted by around 22.6˚ with the north pole tilted towards Earth.

Uranus

  • Best time to see 31 October
  • Altitude 51˚
  • Location Aries
  • Direction South

Uranus reaches opposition on 31 October. Currently located within Aries, the green hued planet shines at mag. +5.7 and is, theoretically, visible to the naked eye. Located in southern Aries, it can take some finding with binoculars. It’s located roughly halfway between Hamal (Alpha (α) Arietis) and Kaffaljidhma (Gamma (γ) Ceti).

Neptune

  • Best time to see 1 October, 23:50 BST (22:50 UT)
  • Altitude 32˚
  • Location Aquarius
  • Direction South

Neptune was at opposition last month and remains well placed for observation. The blue-hued planet shines at mag. +7.8, so you’ll need binoculars to see it. It’s located 1.5˚ east of mag. +4.2 star Phi (ϕ) Aquarii on 1 October.

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Pete Lawrence is an experienced astronomer and a co-host of The Sky at Night. This article originally appeared in the October 2020 issue of BBC Sky at Night Magazine.