Reports - 2013

Pictures from the Hubble Site

Astronomy Benalla  Meeting Presentations - Wednesday 18th  September 2013 Presenter: Patrick Watson The Constellation Carina We started with a brief reminder about star naming – specifically Bayer letters - which would be arise later in the presentation. Around the year 1600 Johannes Bayer applied lower case Greek letter names to the stars more or less in order of brightness, within each constellation, rendering the brightest star in a constellation alpha, the second beta, and so on. ( more or less - of the 88 modern constellations, there are at least 30 in which alpha is not the brightest star, and four of those lack an alpha star altogether. ) This naming method could cause problems as there are many alpha stars! Solution: To the Greek letter name is appended the Latin possessive form of the constellation name. So, where we could have had (say) “alpha of Carina”, it became  alpha Carinae. (NOTE: There are two constellations for which the name and possessive form are the same, Camelopardalis and Puppis.) Problem: With only 24 letters in the Greek alphabet, few stars could receive Greek letter names. Bayer therefore followed the lower-case Greek alphabet with: o lower-case Latin letters (e.g.  d Centauri), then o with upper case Latin letters (e.g.  G Scorpii). The last upper-case letter used by Bayer was Q. The French astronomer  Nicolas Louis de Lacaille surveyed the southern skies from the Cape of Good Hope during the period 1751 – 1753. Due to the vast extent of the then constellation Argo Navis  (the ship of the mythological Jason and the Golden Fleece, and approx. 4% of the sky)  Lacaille  separated it into three constellations, Carina (The Keel), Puppis (The Stern) and Vela (The Sail). When Argo Navis was split, its Bayer designations were also split. • Carina has the alpha, beta and epsilon, •  Vela has gamma and delta, •  Puppis has zeta. Hence, Vela and Puppis are two of the constellations with no alpha. A common although erroneous belief is that the constellation Pyxis (the Mariners Compass), created by Lacaille, was also part of Argo Navis. In fact, on his celestial map of 1752, Lacaille pictures Argo Navis as a complete ship, with Pyxis just to its north - its Bayer designations are separate from those of Carina, Puppis and Vela. The following objects adorn Carina: Canopus is the second brightest star in the night sky. Carina has some of the finest deep sky objects within its borders Open Clusters-a group of stars formed together in the spiral arms of a galaxy containing anything from a few dozen to several hundred relatively young (from a few million to several billion years old) stars. NGC2516 / NGC 3114 / IC2581 / NGC3293 / IC2602 (contains theta Carinae surrounded by  about 60 other stars ranging from 4^th to less than 9^th magnitude) / NGC3532 / Globular Clusters – a roughly spherical group of old stars in the halo of a galaxy containing from tens of thousands to millions of stars. They are very old (10 to the 10 years – 10,000,000,000) having formed early in the history of the galaxy. NGC2808 Emission Nebula – a luminous cloud of gas and dust in space which shines with its own light (e.g. HII regions – regions of interstellar hydrogen that are ionised). NGC3324 Diffuse Nebula - an earlier description of an HII region which retained its fuzzy appearance through a large telescope, as opposed to one which could be resolved into stars. NGC3372 is the finest example of a diffuse nebula found anywhere in our skies. The Eta Carinae Nebula is a monstrous glowing cloud measuring two full degrees across. Contains the open star cluster Trumpler 16 and the star eta Carinae itself. No fewer than five additional open clusters are also seen superimposed onto the nebula – Trumpler 14 and 15, Bochum 10 and 11, and Collinder 228.