Reports - 2013

Pictures from the Hubble Site

Astronomy Benalla  Meeting Presentations - Wednesday 20th February 2013 Presenter: Patrick Watson The presentation started by asking “What Year Is It?” with some possible choices shown – as below:  Gregorian           2013  Julian Calendar (Gregorian minus 13 days)  Thai solar calendar 2556  Buddhist Calendar 2557  Hebrew Calendar 5773–5774  Hindu calendar 2069-2070 It turned out that none of these were to the point, which was: Chinese Lunar New Year - Year of the Snake. Hence, the evening show was to be about Astral snakes. Those to be discussed are the constellations Hydra, Hydrus and Serpens. Hydra Represents a female water snake. It is over 100⁰ long, and is 1^st in order of constellation size, having an area of 1,303 square degrees. Hydra meanders from north of the celestial equator, into the southern celestial hemisphere. A trapezoid of stars marks one of the serpent’s ‘seven heads’. These are Delta  Hydrae. Epsilon Hydrae, Zeta Hydrae, Eta Hydrae and Sigma Hydrae. Hydra is surrounded by  13 constellations (14 if Lupus is counted - it touches at the same corner as does Centaurus and Libra). Interesting objects include open cluster M48. Over a dozen of this cluster’s 80 stars may be seen through 7x and larger binoculars. Then there is the variable carbon star V Hydrae, one of the reddest stars visible. Further objects appear below: Planetary nebula  NGC 3242 (Ghost of Jupiter). Globular star cluster  M68. Modern estimates place M68 at 33,000 light years away and approaching us at about 112 kilometres per second. Its members are spread over a volume of about 106 light years diameter. Spiral Galaxy M83. It has been host to six supernova,  more than any other Messier object. We then moved to Hydrus, a far southern constellation representing a male water snake. Hydrus winds its way from near Achernar in Eridanus toward the south celestial pole, covers  an area of 243 square degrees  and is 61^st in order of size. Hydra does not contain any particularly bright stars. • Beta Hydri, the brightest (yes - brighter than alpha) star in Hydrus, is a yellow star of magnitude 2.8, 24 light- years from Earth. • Alpha Hydri is a white main sequence star of magnitude 2.9, 71 light-years from Earth. • Gamma Hydri is a red giant of magnitude 3.2, 214 light-years from Earth. There are no Messier objects in Hydrus. Finally we move to Serpens, a constellation of the equatorial region of the sky representing a large snake and with an area of 637 square degrees (23^rd in order of size).   Serpens is unique, being split into two “halves”: • Serpens Caput, the serpents head which is the larger half, and •  Serpens Cauda, the serpents tail. Only one of the stars in Serpens is brighter than third magnitude. However, Serpens contains some very interesting objects: Globular cluster M5. The Eagle Nebula MWC 922, a nebula in the Mount Wilson Catalogue. This is a Symmetric Bipolar Nebula notable for its appearance as a perfectly symmetrical square or rectangle (“Red Square” Nebula).   Hoag’s Object is a perfectly shaped ring galaxy  located 59 million light-years from Earth. The outer ring is largely composed of young blue stars but the core is made up of older yellow stars. Seyfert’s Sextet is a group of six galaxies, four of which are interacting gravitationally and two of which simply appear to be a part of the group despite their greater distance. The gravitationally bound cluster lies at a distance of 190 million light years from Earth  and is approximately 100,000 light-years across, making Seyfert's Sextet one of the densest galaxy clusters known. Barnard’s Star - a very low- mass red dwarf star about six light years away from Earth.  Barnard’s star is the third nearest star to the Sun (after Proxima Centauri and Alpha Centauri’s A and B). Barnard’s star has the largest proper motion of any known star. Finally, there are two daytime meteor showers that radiate from Serpens, the Omega Serpentids and the Sigma Serpentids. Both showers peak between December 18th and December 25th.