When stars like the Sun come to the end of their lives they emit a shell of gas that glows due to ionisation from the remaining core of the star. Planetary nebulae are typically about a light-year in diameter and often look beautiful in images and long exposure photographs. The name was coined by William Herschel who thought their resembled the planets, although they have no connection whatsoever with them.

There are no planetary nebulae visible to the naked eye but the brightest examples can be seen in binoculars and small scopes. These include the Ring Nebula (M57), the Dumbbell Nebula (M27) and the Helix Nebula (NGC 7293).

The Helix Nebula is the brightest planetary nebula in the sky (credit:- NASA, ESA, and The Hubble Heritage Team (STScI/AURA))

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Sky Highlights - September 2017

Opposition
Neptune reaches opposition on September 5th

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for September

Northern Hemisphere
Evening
West:- Jupiter (mag. -1.7)
Southwest:- Saturn (mag. +0.5)
East:- Neptune (mag. +7.8)
Midnight
South:- Neptune
East:- Uranus (mag. +5.7)
Morning
West:- Neptune
South:- Uranus
East:- Venus (mag. -3.9), Mars (mag. +1.8) (from second week), Mercury (mag. +0.5 to -1.3) (from second week)

Southern Hemisphere
Evening
West:- Jupiter
Northwest:- Saturn
East:- Neptune
Midnight
West:- Saturn
North:- Neptune
Northeast:- Uranus
Morning
West:- Neptune
Northwest:- Uranus
Northeast:- Venus
East:- Mars (end of month)

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

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