Carina the circumpolar constellation in our southern sky was formed by Gould in 1879 from the southern portion of the large ancient constellation Argo Navis. The Milky Way passes through the north-eastern region of the constellation making this a constellation very rich in bright stars. Carina lies west of Crux,
“The Southern Cross” and south of Vela the Sail.
There are a multitude of open star clusters for binoculars and small telescopes, many double stars, several gas nebulae including the spectacular Eta Carina, many faint planetary nebulae and one nice globular cluster in the constellation.
The stars iota (ί ) and epsilon (ε ) Car with kappa and delta in the constellation Vela form The False Cross sometimes mistaken for our Southern Cross. The cross is a good marker to use to locate Carina.
The brightest star in the constellation white super giant Canopus (α, mag – 0.72) is the second brightest star in the sky after Sirius (mag -1.46). Canopus was named after the helmsman of the Greek King Menelaus.
Beta (β ) is a mag 1.7 blue-white star.
Theta Car (θ) mag 2.7 is within the spectacular open cluster IC 2602, (Caldwell 102) also known as the Southern Pleiades which is a group of about 60 stars and 50 arc minutes in size.Located 4° south of the Eta Carina Nebula this naked eye cluster is best observed with binoculars or a small telescope at low power, using a large field of view. I used my 128 mm (5 inch) scope at 38 x magnification with a 27 mm eyepiece and the cluster appeared as two separate groups of stars with a scattering of stars around the two groups one of which included theta.
NGC 2516 another naked eye open cluster south west of epsilon Car. appears cross shaped in binoculars, at magnitude 3.8 it has approximately 80 stars. With low power of 38 x in the 5 inch there is a spiraling of pin point stars and the brightest star a mag 5.2 red giant is visible.
Another scattered open cluster to locate is NGC 3114 of mag 4.2, 35 ‘ in size southwest of Eta Carina. Most stars are mag 6 or fainter, use binoculars or a small telescope, this cluster is not very impressive.
NGC 3532 in the north-eastern corner of Carina is an open cluster of 150 stars around magnitude 7. It is visible with the naked eye as a hazy spot NE of the Eta Carina Nebula. Best views are with binoculars or very low power. At 25 x magnification with a 40 mm eyepiece there appears to be a star free lane across the centre of a large fairly even scattering of stars. John Hershel described 3532 as “the most brilliant object of its kind he had seen”.
There is one globular cluster worth observing, NGC 2808 mag 6.3, 14’ is a compressed symmetrical cluster containing many faint stars. Easily located south east of iota of the false cross with 7 x 50 binoculars, it appears as a faint nebulous haze. The centre is more condensed with the 5 “ telescope however even at 130 x magnification the stars are not resolved. A 15 cm, 6” telescope should resolve the cluster.
Locate and observe the magnitude 4 – 10 Mira variable star R Carinae, it is a giant orange-red star with a period of 309 days. Near maximum it will be prominent amongst the background stars. Follow a line of 4, magnitude 6 stars south east from iota Car. to locate the star. Using surrounding stars with known magnitude as a guide, what magnitude would you give R Car on your observation night? I first located the star using low power of 38 x and then increased magnification to 82 x. A small reddish star is easily distinguished at the end of the line of white stars and somewhat fainter than the guiding stars. I would estimate it around magnitude 8. How bright does it appear on your observation night?
NGC 3372, the diffuse Eta Carina gaseous nebula is the most spectacular object to observe in Carina. It is located in the north-western corner of the constellation and is easily located by drawing a line from alpha Centaurus through alpha Crux and almost equal distance again north-west to Eta Carina. Alternatively, draw a line from Beta Crux through the fifth offset star opposite directly to Eat Carina. Prominent dark lanes are visible amongst the diffuse expansive nebulosity. Bright orange eta Carinae magnitude 4 is surrounded by an orange – red nebula 15 “ wide called the Homunculus nebula which should be visible in small telescopes. I could not distinguish the Homunculus in my 5” and I could not determine the orange-red colour…I will look forward to the comments of other observers. The Homunculus was formed around the star eta Carina ( ή) after the great 1843 explosion known as Nova Carinae. The explosion shot out two opposing lobes of expanding gas which have been described like “a balloon expanding in a napkin ring” . Eta Carina is a very massive variable luminous blue star which is expected to have a supernova explosion in years to come.
The Eta Carina Nebula is rich in open star clusters. Surrounding eta Carinae is 10 ‘ wide Trumpler 16 (with 10 stars visible at low power) and to the north-west 5 ‘ Trumpler14 (with 5 stars at low power). In the center of TR-14 look for a tight pair h4356 (visible with a 75 mm scope), 2’ south-east is another easy double h4360.
RT Carinae is another bright red variable star of magnitude 8.6 located just south of TR 15 in the Eta Carina Nebula.
Sources: Collins Pocket Guide to Stars & Planets, 3rd Ed; The Caldwell Objects, Stephen James O’Meara; Hartung’s Astronomical Objects for Southern Telescopes, 2nd Ed. Star Atlas Pro