Page 56 - BBC Sky at Night - September 2017 UK

56 SEPTEMBER THE SKY GUIDE

THE PLANETS

PICK OF THE LEO Venus 3 Sep
MONTH MINOR Sickle

URSA
MAJOR
LEO Mars
MARS 4-6 Sep 1 Sep
BEST TIME TO SEE: 16 September, (Mars-Regulus Regulus
Conjunction)
05:30 BST (04:30 UT)
16-17 Sep 1 Sep
ALTITUDE: 2.5º (low) (Mercury-Mars HYDRA
Conjunction) Mercury
LOCATION: Leo
DIRECTION: East-northeast
FEATURES: Colour, dark surface 30 Sep
Denebola Alphard
markings, bright polar caps, weather
EQUIPMENT: 6-inch or larger telescope 30 Sep

Mars is a morning object gradually
pulling away from the Sun’s glare VIRGO
A waning crescent Moon passes through this region
in September. Telescopically, it’s of sky between 17-19 September (omitted for clarity)
rather challenging. It does not 30 Sep
attain a decent altitude and appears
rather small through the eyepiece. E
The planet is on the far part of its
orbit relative to Earth and this Þ Mars and Mercury cross paths; constellation positions shown for 05:30 BST on 30 September
renders its disc small. At present
it has a similar apparent size it will be low in the sky for mag. –0.7) on 16 and 17 September.
to the planet Uranus. those of us in the UK. The two planets will have an apparent
However, it’s good This month the separation of 27 arcminutes on the
to see Mars on the emphasis is more 16th and 21 arcminutes on the 17th.
western side of the on the naked eye On the morning of 17 September,
Sun, a course and binocular Mars and Mercury fall into a straight
that will take it appearances of the line with Regulus, Venus and a slender
towards its next Red Planet. Mars is waning crescent Moon that’s just 10% lit
opposition close to mag. +1.8 and forms – you can read more about that encounter
the end of July 2018. an interesting pattern in this month’s Big Three (page 52).
This will be a perihelic with mag. +1.4 Regulus It’s fascinating to watch how these
opposition, one which (Alpha (_) Leonis) and patterns of planets, bright stars and the
occurs when Mars is in mag. +1.5 Mercury from Moon appear to change over subsequent
a part of its orbit that Þ Mars will appear small, 5-8 September. Look to mornings. By 30 September, Mars and
its disc about the same
PETE LAWRENCE X 3 As a consequence this will size as Uranus’s about 05:20 BST (04:20 UT). to be 2.7º apart. This comes ahead of a
takes it closer to the Sun.
the east-northeast from
a dazzling mag. –3.8 Venus will appear
There’s a really close encounter between
further close encounter set to occur in
be a favourable situation for
earthbound observers too, although
the first week of October.
Mars and a much brighter Mercury (now
THE PLANETS IN SEPTEMBER The phase and relative sizes of the planets this month. Each planet is
shown with south at the top, to show its orientation through a telescope
VENUS MARS JUPITER SATURN URANUS NEPTUNE
15 Sep 15 Sep 15 Sep 15 Sep 15 Sep 15 Sep
MERCURY
1 Sep

MERCURY
15 Sep

MERCURY
30 Sep 0” 10” 20” 30” 40” 50” 60”
ARCSECONDS

skyatnightmagazine.com 2017