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Thursday, December 20, 2012

Solstice on Doomsday!

December 21st is a significant date for a few reasons.
Every year around this date the Earth reaches a position around the Sun that causes the south pole to lean/tilt towards the Sun at its greatest extent. This is known as Solstice, which means "Sun-stationary".
This could mean its an ideal time to buy lots of nice pens, pencils and rulers illustrated with smiley-face suns for Christmas or.... that the Sun, having gradually shifted more toward the South each day for the past few months, has now reached its Southern-most point in the sky. Therefore with each new sunrise after 21st December, the Sun appears to reverse course and shift back towards the Northern half of the sky.

The effects of the Solstice are the related to the seasons, as the intensity of sunlight varies at different places on the Earth.
Commonly known as Winter Solstice, it also results in the shortest daylight hours and longest night of year in northern hemisphere countries. At the same time, southern hemisphere countries experience their Summer Solstice or longest daylight hours/shortest nights.

Naturally there are lots of cultural events and festivals around this time. In Singapore, some of those of Chinese ancestry celebrate with family and friends by eating a dessert known as tangyuan 湯圓

The region that receives the most intense sunlight at this time of year is known as the Tropic of Capricorn. This is because the Sun's position in the sky during this time (i.e. its southernmost point), used to be directly in front of the constellation Capricornus.
However, the Earth's tend to wobble as it rotates and over thousands of years this wobble (known as precession) resulted in the Sun's southern solstice position shifting into the neighbouring constellation of Sagittarius. I guess someone should go re-label all those globes and maps and replace the Tropic of Capricorn with "Tropic of Sagittarius". At the same time they should also change the northernmost position of the Sun as well (i.e. Tropic of Cancer Gemini).

Solstice in Singapore
As mentioned in my previous post during the June Solstice, the effects on equatorial regions, such as Singapore, are much more subtle.

Slightly north of the equator, Singapore also experiences its shortest daylight hours, roughly 12hrs 3mins 2secs from sunset to sunrise, but this does not coincide with the latest sunrise, which occurs during February in the tropics.
Solstice marks the time when Singapore sunrise becomes later than 7am (i.e.7:01am). From now until February, sunrise will gradually get later and later, so you can enjoy a few extra minutes of darkness in the morning.

Sun's position 9am June - Facing east, Sun rises from North-East (left)

Sun's position 9am December - Facing east, Sun rises from South-East (right)
At June/Northern Solstice the Sun rises from the North-East direction and sets North-West.
In December, sunrise is from South East and sunset South-West. Therefore, those with south-facing windows can expect more sunlight at this time of year, while north-facing window enjoy more shade. However, in December its raining most of the time, so it probably won't make much of a difference.

End of the year world
Finally, 21st December 2012 is now more well known for its association with the ending of an ancient Mayan calendar.
Mayan Pyramid of the Moon
These ancient Central Americans kept track of the days in the following way:
1 day is called a k’in.
20 days is referred to as 1 winal.
360 days is called 1 tun.
A period of 20 tuns is called 1 k’atun
20 k’atuns are grouped into 1 b’ak’tun, which is equal to 144,000 days.

This so called Mesoamerican Long Count Calendar ends after a cycle of 13 b'ak'tuns, which when translated to our modern Gregorian Calendar finishes on 21st December 2012. 
Many scholars and scientists  think that after this date the calendar simply repeats itself or starts again, similar to how we always start back at January every year.
However, there are many other ideas out there that have developed over time, referring to doomsday and the end of the world. Many are based on scientific findings and events like asteroid collisions, planetary alignments and solar storms but have been extremely exaggerated and highly unlikely.
I think its all just a great excuse to make tonnes of movies, documentaries, write books and articles.
I guess we will find out soon!

Wednesday, December 19, 2012

December Updates - Part 2

It was a fascinating night last Friday, with one of the clearest skies we had at SCOB in several weeks. A large patch of cloud drifted by in the early evening but towards the end of the session, things cleared up again and, with no Moon around, many of the familiar December stars were free to shine as best they could in our light polluted sky.
Photo of the constellations Orion (top), Canis Major with Sirius (right), Canis Minor and Procyon (below in cloud) and parts of Gemini (lower left).
Initially, most of our attention was focused on Jupiter. During the most crowded period we were watching as Jupiter's moon Io gradually appeared out from the giant planet's shadow.
Didn't have a camera handy at that point but after closing time I took a few snaps of the Jupiter and the surrounding area of Taurus, including the Pleiades (M45) star cluster.
Long exposure photo of Taurus (v-shaped) with Jupiter (brightest object) and Pleiades Star Cluster (centre).

To finish the evening we had a last look at the great Orion Nebula (M42). I attached the camera to our main 16 inch telescope but didn't manage to reach the correct focal point, so switched to the 6 inch refractor for a "quick" 30 second exposure before the battery went flat. Next time, must remember to be more prepared and get all this photograph stuff ready early. I'm still new to astrophotography and with all the other things going on it tend to be last on my mind.
Orion Nebula M42 through 6 inch refractor telescope using a Nikon D70s camera.  The central collection of stars is known as the Trapezium, because of the four brightest stars but if you look closely there are actually 6 stars. 

The central collection of stars is known as the Trapezium, because of the four brightest stars but if you look closely there are actually 6 stars. Many visitors often confuse the three stars at the bottom with Orion's Belt. I guess its easy to form a connection between the two as the telescope is roughly pointing in the same direction as the belt, which makes it harder to grasp the concept that what we're looking at only occupies a tiny speck of sky and cannot be fully observed by the eye alone.

At one point that night we tried pointing our telescope at the Andromeda Galaxy M31, with an experienced eye I could make out the faint glow of its core but to many of our visitors it was almost invisible, I recall seeing a few blank expressions as I tried to explain about using averted vision :/

That's all for now!

Wednesday, December 12, 2012

December update

Its's 12-12-12, and I haven't done any update yet for December.
As expected the weather is still very cloudy and rainy. There were a few clear nights last week so once again I was out with my camera to take a few shots of this month's bright celestial highlights.
In particular Jupiter, Taurus and Orion. The Bull and Hunter always appear in the East during the early evening in December. This year, they are accompanied by the largest  (and second brightest) planet, Jupiter.

Over the next few weeks,  Jupiter will slower move away from Taurus's bright star Aldebaran (the follower). Later in the evening and toward the end of the month, Sirius, the brightest star in the sky will also appear, shining brightly south-east of Orion.

December is usually a good month for watching meteors/shooting star, with the Geminids meteor shower peaking around 13th-14th December (this week in fact!).
With an expected high rate of meteors and no Moon in the night sky, its bound to be the best shower of 2012.
However, in a bright city like Singapore, in the middle of the rainy season, the chances of seeing any shooting stars are significantly reduced, oh well. If we get a clear night sky of the next few days and you stare at the sky for a few hours after midnight it will increase your chances.

Other things happening this month include, Venus and Saturn still there in the early morning around 6am-7am towards the East. Mercury is there too but low altitude makes it very difficult to spot in the usual morning hazy.

21st December is southern solstice, which makes the southern most position of the Sun in the sky. Southern hemisphere countries will also experience their longest daylight hours, while the north has the shortest daylight hours. More on this in a future post.

Moon Dates for December:
We'll be observing the Moon at SCOB on Friday 21st Dec & Friday 28th Dec.

Finally, our school holiday activities are still available and going strong at SCOB every Friday evening this month.

During the past few weeks the planetarium has been the most popular activity, with light painting a close second. We also have a few items, such as astronomical 3D postcards, for sale. Surprisingly, the astronaut ice cream as been an unexpected hit.

Occasionally, we have a few visitors pop by, who appeared to have lost their way. For instance, this guy, who kept asking about some rebel base?????????