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Archive for the ‘Stars’ Category

17 June 2012

Woke up this morning and looked out of Bedroom Observatory. There was the crescent Moon hanging off the palm tree like a slice of silver fruit!

Crescent Moon

Crescent Moon (Click on image to enlarge)

I moved to get a better view and two bright sparks came into view! Jupiter and Venus! Gorgeous! And all before sunrise!
How quickly Venus has moved across!

Crescent Moon with Jupiter and Venus

Crescent Moon with Jupiter and Venus (Click on image to enlarge)

18 June 2012

We are really out of practice of waking at 4 AM and throwing off the feather doona, our warm nest for the night.  But jump out of bed we did, and looked out of Bedroom Observatory.  The sky overhead was clear, but it was too dark to judge whether there were low clouds in the eastern horizon.  A clear horizon was crucial for today’s pre-dawn viewing.  The only way to find the answer was to check from Clifftop Observatory.  So we had a quick cuppa, rugged up, gathered our camera gear, and drove to North Bondi.  The temperature was 9 deg C, and a cold wind from the south pole was about.  From where we parked we had to climb about 100 metres, and our fingers froze holding the cold metal of the camera tripod.

When we reached Clifftop Observatory, we stood stunned, breathless and motionless.   Jupiter was lined up with the Pleiades; the new moon was below lined up with Venus.  And Venus was pretending to be the brightest object in Taurus!

Jupiter, the Moon, Venus

As the sky brightened, some of the little stars got swallowed up in the dawn light, but the main players were still there, keeping us riveted.

Jupiter, the Moon and Venus

Jupiter, the Moon and Venus (Click on image to enlarge)

Before we left, a photo with our favourite tree and my favourite man was mandatory!

Dom the tree and the planets

Dom the tree and the planets (Click on the image to enlarge)

When we came home, we could still see the triangle of Jupiter, Moon and Venus over the roof of our house. 

Final look at Jupiter, the Moon and Venus

Final look at Jupiter, the Moon and Venus (Click on image to enlarge)

The weather man says the rain has gone to Spain for a few days.  So here’s cheers to clear weather and more good viewing.

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5 February 2012

“The sun is shining — come on, be happy”— is the song on the lips of Sydneysiders! After weeks of rain and grey skies, the sun broke through on Saturday 4 February. The weatherman announced on Friday that we were in for another 21 days of rain with three sunny days between — and we were using up two of those three days on the weekend!

So we got the cameras charged and loaded, ready to click, day and night!

After a Sydney blue day, we awaited sunset. The Moon had risen and looked splendid as the Belt of Venus and the shadow of earth painted broad pink and blue bands across the eastern sky.

After dinner at my brother’s place in North Sydney, we went to the balcony at about 10 pm. Sydney harbour lights were doing their utmost to pollute the sky, but we’ve learnt to live with such annoyances. Tonight the lights did us a favour by blotting out the dimmer stars and allowing the Southern Cross to shine through in its full glory. The Pointers, α(Alpha) Centauri and β(Beta) Centauri, were low in the sky, doing their duty of pointing to the Southern Cross!  Oh, it was a grandstand view of the most recognizable constellation in Australia!

Southern Cross

Southern Cross (click on image to enlarge)

Our clever camera picked out all five stars of Crucis, the Southern Cross, the smallest and most distinctive of the 88 constellations that populate the sky. The Pointers and Crucis form a wonderful starting point for a study of the stars because of their position and colours. The Pointers and the Southern Cross

α(Alpha) Centauri and β(Beta) Centauri

We were marvelling at their colours – αCentauri’s yellow/red and βCentauri’s white when Dom says, “Did you know that αCentauri is the star closest to our galaxy?” 

“Of course I do, but did you know that it isn’t one star, but three?”

What surprises both of us are the facts about this stellar threesome:

αCentauri-A (large and yellow like our Sun) and αCentauri-B (slightly smaller and cooler) take 80 years to orbit around each other, and they are about 20 times as far from each other as Earth is from the Sun. Wouldn’t it be cool if αCentauri supported a planet like our Earth! αCentauri A and B together form the third brightest star in the sky and the brightest in the constellation Centaurus. With a magnitude of 0.27 αCentauri shines on us from a distance of 4.3 light-years. 

The third star, αCentauri-C, is closest to us and is called Proxima Centauri. What else? It is very far from the central pair; at least 300 times as far as the most distant planet in our solar system is from the Sun! And it’s on a very slow walk round its siblings  – a single circuit takes 500,000 years or more!

Though it is the closest star – 4.2 light years away – we can’t see it with the naked eye, or even our binocs, because it is dim, red and small – about 18,000 times fainter than our Sun.

Summing up the trinity collectively known as αCentauri: 
(i) the two large siblings, each approximately as big as our Sun, waltz around each other every 80 years, at a distance 20 times our Sun/Earth distance;
(ii) the third sibling circles the other two every 500,000 years, at a distance 300 times our Sun/Neptune distance. This is the star closest to our galaxy. 

What does it mean when we say that αCentauri is roughly 4 light years away from us? It means that it takes 4 years for light to travel between αCentauri and us.

αCentaurians, if they were tuned in to Earth right now (Feb 2012), would be just seeing Kevin Rudd, the new Prime Minister of the Labor government make a historic speech of apology to the Stolen generation of Aboriginal people; Barack Obama’s election campaign in full swing; and Castro resigning as President of Cuba! Yes, they would be seeing us as we were in 2008!

This diagram below illustrates a comparison of the sizes and colours of the three stars of the αCentauri system and our Sun.

Relative sizes of Alpha Centauri and our Sun

Relative sizes of Alpha Centauri and our Sun (Click on image to enlarge)

 Position of the Southern Cross during the year

Finding the South Pole, using the Pointers and Southern Cross

Adapted from Wikipaedia http://en.wikipedia.org/wiki/File:Pole01-eng.jpg

Read also a great blog from the Observatory on finding the South Pole: http://www.sydneyobservatory.com.au/2008/finding-south-using-the-southern-cross-an-essential-skill/

Colours of the Cross

Looking closely at the Southern Cross, I notice the different colours. Going clockwise α (Alpha) and β (Beta) Crucis are blue-white, but γ (Gamma) at the top of the Cross is red. δ (Delta) Crucis is blue-white and little ε (Epsilon) Crucis – hard to see without binoculars now because of increased light pollution –  is orange.

Colours of the Southern Cross

Colours of the Southern Cross (Click on image to enlarge)

 There’s more to explore around the Southern Cross, but a Gibbous Moon is competing for my attention right now!

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