A classification introduced by the International Astronomical Union (IAU) in 2006 to describe celestial objects that don't quite reach planetary status. This new class currently includes Pluto, Ceres, Eris, Haumea and Makemake. Of these, Pluto was formerly a planet, Ceres is the largest object in the main asteroid belt and Eris, Haumea and Makemake are trans-Neptunian objects.

The classification was introduced after the discovery of Eris, which is larger in size than Pluto. With the discovery of numerous objects further than Neptune it was decided a new classification of object was required otherwise the number of planets in the Solar System would dramatically increase.

Pluto from New Horizons space probe (credit:- NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute)

Glossary A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Sky Highlights - August 2017

Total Solar Eclipse
Total Solar Eclipse of August 21st

Meteor Shower
Perseids meteor shower peaks on August 12th

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for August

Northern Hemisphere
Evening
West:- Mercury (mag. +0.4) (start of month)
Southwest:- Jupiter (mag. -1.9)
South:- Saturn (mag. +0.3)
East:- Neptune (mag. +7.8)
Midnight
Southwest:- Saturn
Southeast:- Neptune
East:- Uranus (mag. +5.8)
Morning
Southwest:- Neptune
South:- Uranus
East:- Venus (mag. -4.0)

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

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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