Canopus is a brilliant star in the southern constellation of Carina and second brightest in the night sky. At magnitude -0.72 it's about 50% as bright as Sirius but appearances can be deceptive; Canopus is easily the more powerful of the two with Sirius only appearing brighter because it's much closer to Earth. With a declination of -52 degrees, Canopus is best seen from southern latitudes. It appears high in the sky from Australia, New Zealand, South Africa and much of South America. Indeed from such locations the star is either circumpolar or only briefly sets. It's a magnificent sight, especially during warm summer evenings.

Unfortunately, its position means Canopus can't be seen from most of Europe and significant parts of the United States. It never rises above the horizon for observers north of 38 degrees latitude although those at the bottom of Spain and Portugal, southern Florida, southern Texas and Hawaii can glimpse it during winter evenings. The star is also visible from India, Pakistan and much of China and Japan.

Interestingly from an historical perspective the fact that that Canopus could be seen from Alexandria but not from Athens provided early proof that the Earth is a globe and not a flat disk, where such behaviour would have be impossible.

Canopus (Fred Espenak)

Canopus is of the course the primary star in the constellation of Carina, the Keel. However, in previous times this area of sky was part of much larger Argo Navis, a constellation named after the ship that carried Jason and the Argonauts in their quest for the Golden Fleece. Argo Navis was the largest constellation in the sky and considerably larger than today's number one, Hydra. Canopus traditionally marked the rudder of the ship but Argo Navis was an unwieldy grouping that the International Astronomical Union (IAU) eventually lost patience with and chopped it up into Carina (a keel), Puppis (a poop), Vela (sails) and Pyxis (a compass). French astronomer Lacaille had proposed the separate parts much earlier and they were eventually accepted by the IAU along with the complete dropping of the Argo name.

Canopus was a star of great importance in ancient times for those far enough south to see it although the origin of its name is unclear. One possibility is that it was named after the legendary captain of the ship in the Trojan War that carried King Menelaus home after the fall of Troy. While landing in Egypt, Canopus failed to survive an encounter with a snake and Menelaus subsequently built a monument in his honour with a town growing up around it, although it eventually declined and fell into ruins. Today the city of Aboukir occupies the site. Another theory is that Canopus comes from the Egyptian meaning Golden Earth, a reference possibly to the star's appearance as it battled against the thick atmospheric haze low down above the Egyptian horizon.

Arab nomads respected greatly the star. When it could be seen rising in the dawn sky for the first time each year it signaled summer was over and time for weaning the camels. The New Zealand Maori's used sightings of Canopus to plant crops. These day astronauts and space probes often use Canopus for navigational purposes.

The star itself is a type F0Ib supergiant and therefore should have a yellowish tinge but most observers report it as pure white. The surface temperature is 7,350K and considerably hotter than the 5,778K of the Sun. It's also 14,500x more luminous than our star. At a distance of 310 light-years and with an apparent magnitude of -5.6, Canopus is the most intrinsically bright star within 700 light-years. Currently the southern pole doesn't have a bright star nearby but around 14,000 AD the effects of precession will take it to within 10 degrees of the South Celestial Pole.

Canopus is located south of Sirius, not that you will need a marker to find it. It dominates the surrounding area of sky but has not always done so. The erratic variable star Eta Carinae in the mid 19th century outshone Canopus and almost rivaled Sirius. It may well again return to such brilliance but for now, Canopus reigns supreme in that part of sky.

Finder Chart for Canopus (Alpha Carinae)

Finder Chart for Canopus (Alpha Carinae) - pdf format

Canopus Data Table

Bayeralpha (α) Car
RA (J2000)06h 23m 57s
DEC (J2000)-52d 41m 44s
Distance (ly)310
Apparent Mag.-0.72
Absolute Mag.-5.6
Spectral TypeF0Ib
Radius (Sol)71
Surface Temp (K).7,350
Luminosity (Sol)14,500
Age (million years)~10
Other designationsSuhail, HR 2326, HD 45348, HIP 30438
Notable featureSecond brightest star in the night sky

Sky Highlights - July 2017

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for July

Meteor Shower
Southern Delta Aquariids (Aquarids) meteor shower peaks on July 29

Northern Hemisphere
West:- Mercury (mag. -0.5 to +0.3) (second half of month)
Southwest:- Jupiter (mag. -2.0)
South:- Saturn (mag. +0.2)
West:- Jupiter
South:- Saturn
East:- Neptune (mag. +7.8)
Southwest:- Saturn
South:- Neptune
Southeast:- Uranus (mag. +5.8)
East:- Venus (mag. -4.1)

Southern Hemisphere
West:- Mercury (second half of month)
Northwest:- Jupiter
East:- Saturn
West:- Jupiter
North:- Saturn
East:- Neptune
West:- Saturn
North:- Neptune
Northeast:- Venus, Uranus

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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