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Saturday, April 25, 2009

A cross, a centaur and a boat

Lately, the weather has been very hot day and night, it can be very uncomfortable at times but its not all bad. For one thing my laundry drys alot quicker (however that can mean the ironing pile increases faster also), secondly, it seems the hot weather is creating some very clear skies which is great for stargazing particularly as we're coming to one my favourite times of the year.
During the months of May and June, you may want look outside one night and find somewhere that has a clear view of the southern sky.

As long as your not looking directly at a street light or at somebody's house you should be greeted by two (possibly three) bright constellations. I'm talking about the fairly well known Southern Cross and the constellation Centaurus.
Below is a representation of these constellations as they would appear when looking South:

The Southern Cross (officially known as Crux) has a distinctive diamond/kite shape formed by its four brightest stars. The bottommost star is called alpha crucis (or Acrux) it is the brightest of the four. Clockwise from Acrux are the other three stars are beta, gamma (the top star) and delta crucis, in that order.

Surrounding Crux like an arch are the stars of the centaur (Centaurus), named after the mythic creature possessing half the body of a horse and half the body of a man (obviously, the horse's body forms the lower part of the creature and the man's body the top part, not the other way around). The brightest stars in Centaurus are Alpha and Beta Centauri located just to the left(East) of Crux. Alpha centauri (Rigil Kentaurus) represents the front foot of the centaur and is the closest star system to the Sun. Through a telescope this star actually consists of two yellow stars. There is even a third star, a faint red star which is barely visible.

What make these constellations interesting to me is the wealth of other objects that lie around them. This includes some bright star cluster. My favourite would have to be the Jewel Box cluster (kappa crucis). Located close to beta crucis (Mimosa) it is a tight cluster of 50 or so shining stars one of which is distinctively red in colour.
Almost all the stars of Jewel Box can be seen through a telescope (depending on the sky conditions). The cluster can even be seen with binoculars. In fact this area of sky is great for exploring with binoculars, there are many other star clusters nearby.
In the diagram above, I've indicated the positions of the 7 other clusters. On a clear night, I find it most enjoyable to grab a pair of binos and scan this area. Most of these clusters will look like small fuzzy or misty patches as the binoculars will not be able to resolve the individual stars within each cluster, except maybe in Jewel Box. Here is a list of the other star clusters.
1. Omega Centauri globular cluster - a densely packed ball of thousands of stars
2. Open Cluster NGC3766
3. Open Cluster NGC 3532
4. Eta Carinae Nebula (NGC 3372) - a gas cloud and star cluster surrounding the explosive star eta carinae.
5. Open Cluster NGC 3293
6. Open Cluster IC 2581
7. Open Cluster IC 2602 - known as the Southern Pleiades
You may notice that many or these clusters lie next to the constellation Carina (representing one part of a sailing ship). The stars of Crux, Centaurus and Carina lie in front of a distant edge of our galaxy, The Milky Way. Although this dense band of stars is to faint to be seen in Singapore, we can still get a glimpse of some of its wonders like the Jewel Box star clusters.
A few weeks ago, I was at an astronomy event at East Coat Park (area D1). Below is a photo I took of the Southern Cross in the sky together with the star alpha and beta centauri, to the bottom left of the picture. (FYI, I took this picture with a regular Canon Ixus 8MP set to a 6 sec exposure/shutter speed)
I also couldn't resist a spot of light painting with a light stick. There was a new star in the sky that night - andrew centauri :) ....... sorry if that was a bit lame.

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