June 2013 - Venus, Mercury, Solstice, Supermoon and HAZE!!!

June got off to a pretty good start with clear nights and some great views of Saturn.

Planets Venus and Mercury also made an appearance shortly after sunset. Mercury was at its highest on 12th June, about 24 degrees high at sunset. Its gradually getting lower each day before disappearing by end June.

I took this picture on 10th June, when a thin waxing crescent Moon was near Venus. Mercury is the dimmer object above Venus near the top edge of the photo.

Venus will get higher each day from now until November as it makes its way closer to Earth.

Mercury-Venus Conjunction
On 20th and 21st June, Venus and Mercury will appear close together (about 2deg apart). Due to their low position in the western part of the sky, they will only be visible from 7:30pm-8pm.

Screenshot from Stellarium planetarium programme - posted on Singapore-Sky Facebook page by Dr KK Cheong.

Sadly, the haze that has currently enveloped the island will make these planets almost impossible to see.

Northern Solstice
June 21st is the time when the Sun reaches its northernmost point in the sky due to the tilt of the Earth. This also causes warmer temperatures and longer daylight hours in the Northern parts of the world.

In Singapore, expect the Sun to rise from the north east and set in the north west. Daytime will also be slightly longer than usual, 12 hours 11 mins 43 secs to be more exact. Sunrise: 7:00am, Sunset: 7:12pm.
For more info on Solstice see last year's post: Solstice in Singapore

Supermoon Returns
23rd June 2013 is Full Moon in Singapore. Its also the Moon's closest perigee (the Moon's closest point to Earth), resulting in a  larger than normal Full Moon, known as a Supermoon.
Even at its closest point the Moon is still 356989km away, therefore the difference in size is hard to notice.

Size difference of Full Moons at closest position to Earth (perigee) and furtherest distance (apogee)

Usually the Moon looks bigger when its lower in the sky due to an illusion where are brain perceives objects near the ground closer than those high in the sky.
The June Supermoon is actually closer than other supermoons that occur in the year but once again it will be difficult to notice unless you compare photos of other full moons.
More on supermoon: Earth and Sky - Most "Super" Supermoon

Haze
These three astronomical events are quite subtle and can be missed if you don't know what you're looking for. Visibility is made worse by the haze blowing over Singapore from Sumatra.
The air quality/Pollutant Standards Index is currently in the unhealthy-hazardous range, so its not the best time to be going outside looking at the sky.
Took a picture of the hazy Sun setting behind Science Centre on the way home last night.

Someone commented that it looked a bit like Lord of the Rings, i.e. the eye of Sauron above the Dark Tower Barad-dur. A few minutes later I saw a post from SGAG with the exact same idea:

Original picture submitted by Jonathan Chong. Posted on SGAG facebook and www.sgag.sg

February 2013

ISS
February starts with a bright International Space Station (ISS) pass over Singapore on Sun 3rd Feb 7:38pm-7:45pm.

During this time the ISS will pass almost directly overhead, from south-west to north-east between the bright stars of Orion and the planet Jupiter.
The only things that will interfere with its visibility will be clouds or the bright evening sky at this time of year.

Star map showing the path and timings of ISS pass on 3rd Feb in Singapore.

Sunrise-Sunset
You may have noticed that mornings remain darker for longer and early evening (ard 7pm) is brighter than usual.
Every year in February, Earth is halfway between its Solstice(21st Dec) and Equinox(21st Mar) position, resulting in the latest sunrise and sunset of the year in equatorial regions like Singapore.
Around 10th Feb the Sun rises at 7:17am and sets at 7:21pm.
Therefore the late sunset may impede ISS visibility.

Chinese New Year!
Its no coincidence that CNY also occurs on 10th Feb this year.
The date of Chinese Lunar New Year is also related to the position of the Sun at this time of year.
In China, the Sun's position around 3rd-4th Feb traditionally signifies the start of spring or Lichun 立春.
The New Moon closest to Lichun, is the start of the lunar new year.

Moon dates for Feb 2013

Obviously, during new moon, the moon is facing towards the Sun and is obscured from view. You can expect to see the Moon in the evening from 14th Feb to 26th Feb.

Position of the Moon in the early evening sky during Feb 2013

Jupiter's Moon
Jupiter remains the brightest planet in the night sky. During Friday's at SCOB we'll be able to see the following arrangement of its four biggest moons:

Mercury
The closest planet to the Sun, reaches its maximum elongation (18deg) east  of the Sun, meaning Mercury is at is highest position, towards the West direction shortly after sunset on 14th Feb (around 7:30pm). Ideal weather conditions (clear sky) are required to see it, but it is just visible to the naked eye.

Constellations
Finally, at least 8 of the brightest stars in the sky are visible in February. This includes Sirius, Canopus, Procyon.
One of our most common targets is of course Orion, reaching his highest point in the sky in the early evening this month, which should give us some pretty good views of the Orion Nebula.

Diagram of the brightest stars in the constellation Orion

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!

Halloween in the tropics - an astronomical event

Next week is Halloween. This festival is normally associated with death and spook things but it also has an astronomical significance, just like alot of other seasonal holidays.

Halloween occurs on 31st October every year, which is in the middle of the season of Autumn or Fall in the Northern temperate regions of the Earth. During this time the leaves on many trees (so called "deciduous trees") start to turn brown and fall to the ground, in preparation for the approaching winter months.
I'd imagine that the disappearance of alot of the summer flora and fauna was one of the key influences for the "death" theme of Halloween, as at this time life simply seems to fade away, to be replaced by a cold, barren, frozen landscape.

A typical British street during winter - with leafless trees and frost or snow covering the ground.

These changes are mainly triggered by a reduction in the amount of sunlight, resulting in a lose of chlorophyll (the green stuff responsible for photosynthesis) in leaves.

Basically Halloween signifies the middle point between the Autumnal Equinox (22nd Sept - where night and day are equal in length) and the Northern Winter Solstice (21st Dec - the shortest daylight hours of the year).

Although we don't experience the same seasons here in tropical Singapore, there are a few  astronomical clues that can be observed around Halloween:

1) Early Sunrise/Sunset
If like me you wake up for work around 6:30am-6:45am, you may have noticed recently that the sky is already bright compared to a few months ago when at the same time it was still dark.
This is because on the day after Halloween (1st Nov) Singapore (and other tropical areas) experiences its earliest sunrise for the whole year. Sunrise on this day occurs at 6:46am compared to the latest sunrise of 7:17am on 10th Feb (incidentally close to Valentine's Day and Chinese New Year).
In the tropics, early sunrise also means early sunset. So if you get home around 7pm, over this next week, it should be almost dark as sunset on 1st Nov (and Halloween) is at 6:50pm.
All this is a result of the orientation of Earth's tilt relative to the Sun at this time of year.

9am Morning Sun during June  - Sun located towards North-east (on the left).

9am Morning Sun in October - Sun is slightly higher and more towards the South (right) than earlier in the year.

2) Southern Sun
During Equinox (22nd Sept) the Sun is directly level with the equator, which from Singapore, results in the Sun rising due East and setting due West, with the midday Sun directly overhead.
On December 21st (solstice) the Sun rises from its most southern point in the sky. Around Halloween the Sun will be halfway between these two positions. So the daytime sunlight will come from a slightly southern direction. Bad news for those with south-facing windows, as for the next few months you can expect more and more sunlight on that side of your house.

This effect can also be seen in the orientation of shadows on ground.
Back in June (close to northern solstice) the Sun was at its northern most point so shadows appear to point south.

12:30pm - Midday shadows in June (solstice) - shadow are long and point south (left).

During Equinox, shadows pointed more or less east and west as well as directly below our feet.

12:30pm - Midday shadows in September (Equinox)  -  shadows are short, gradually pointing west and east in the morning and afternoon.

Lunchtime shadows in September (Equinox) are directly  below our feet

Around Halloween shadows now point slightly north (i.e. opposite the Sun).

12pm - Midday Shadows in October (close to Halloween) - shadows point slight North (towards the right)

Of course Halloween has alot of other cultural and religious influences, but its timing is primarily astronomical in basis and represents one of the four so called "cross-quarter dates" that occur between solstice and equinox.

Being an astronomer in Singapore has its uses, sometimes to share these little tidbits of information with others whilst walking out for lunch, to pause for a few seconds in order to look around and observe the small occurrences of the Earth's daily wanderings through space before we ourselves resume going about our own daily life.

September Sky 2012

September is here and change is abound.

Stars and Constellations of September
For months we've been concentrating on the bright southern constellations like Crux, Centaurus, Scorpius and Sagittarius.

Stars of Sagittarius as seen from Singapore

Scorpius and Sagittarius are still around but now its time for these constellations to gradually move aside for some of the brightest stars in the northern part of the sky like those of Aqulia Cygnus and Lyra, which include the Summer Triangle.

1) Delphinus – a small constellation representing a Dolphin. Visible to the naked eye and binoculars.

2) Coathanger Asterism (Brocchi’s Cluster) – A small group of 10 stars in the shape of a coathanger. Requires binoculars or small telescopes. Located in the faint constellation of Vulpecula.

3) Dumbbell Nebula (M27) – a Planetary Nebula, gas cloud formed from the other layers of a dying star.

Appears as a faint misty ellipse using low magnification.

4) Albireo (Beta Cygni) – a colourful double star, yellow and blue in colour. Requires telescope.

5) Ring Nebula (M57) – A faint planetary nebula in the shape of a ring or halo. Appears misty in small telescopes.

6) Double-Double (Epsilon Lyrae) – Four stars arranged in pairs, very close together. Larger telescopes and high magnifications are need to separate each pair to see all four stars. 600 light-years away.

Some my favourite targets within these constellations are double stars like the colourful Albireo (beta cygni) and the Double Double (epsilon lyrae), as well as a faint collection of stars known as the coathanger asterism (among other names). Visible in binoculars or a finderscope its located near the centre of the Summer Triangle (constellation Vulpecula) and looks like a coathanger.

Double Star "Albireo" - Beta Cygni as seen through the observatory's 16 inch cassegrain reflector telescope

In the unlikely event of extremely clear skies and no moon we may feel ambitious and aim for the faint glows of the Ring Nebula(M57) and Dumbbell Nebula (M27).


Planets
This year, September also sees the disappearance of Saturn, but it can still be seen for a few weeks in the early evening around 8pm.
Mars hangs around for a another month or two, although it now appears very tiny in telescopes. Gradually making its way across the constellation Libra, Mars will eventually end up in front of Scorpius, next to the bright red star Antares.
Antares gets its name from Mars, as "Ares" is Greek for Mars, therefore Antares literally means "Anti-Mars" as they both appear similar in colour (red/orange).

Neptune and Uranus are at their closest position to Earth right now. Neptune was at opposition (in direct alignment with Earth) on 24th Aug and Uranus will reach opposition on 29th Sept.

This means that they'll be visible during the later part of the evening but even at their closest they are still billions of kilometres away so in a telescope they kinda look like this:

The Moon

The best time to view the Moon during our Friday Night Stargazing session will be 21st Sept (Crescent Moon) and 28th Sept (Gibbous Moon).
A good time for moon watching, at home will be on the evenings 19th & 20th Sept, when the crescent Moon moves past the red planet Mars and then between Mars and the red star Antares:

Finally 30th September is Mid Autumn Festival  中 秋 節 - Full Moon/15th day of 8th lunar month (Chinese Lunar Calendar), a time for family celebrations, lanterns and mooncakes.

What's special about this Full Moon is that it's the closest Full Moon to the Autumnal Equinox (22nd Sept, where night and day are equal length).
A common assumption about mid-autumn is that the Full Moon is at its biggest or brightest, which is not the case. Lunar festivals usually have some seasonal significance. For mid-autumn, its harvest time in the northern hemisphere.
The orientation of the Earth during Equinox causes the Moon to rise at a smaller angle and stay in the sky slightly longer (roughly12-13hours) than in previous months. Therefore, warm autumnal temperatures and long moonlight hours make this full moon the ideal time for night harvesting, before the cold winter weather arrives. In Europe, the autumnal Full Moons are called Harvest Moon and Hunter Moon for similar reasons.

Of course, here in Singapore, near the equator, its warm all year round and there is little or no change in the Full Moon's timing in the sky but we still in get to enjoy the festivities.

Not so Blue Moon!

I recently encountered a number of questions about this month's double full moon. The first full moon occurred on 2nd August (2012) and the second is tonight (Friday 31st August).
Its a common misconception that the second full moon in a month is called a "blue moon". I also made this assumption previously, however this is not the case. Having two full moons in one month does not result in a Blue Moon.
Throughout several conversations this week, I have attempted to explain why and this is the best explanation I can come up with:

The rather long background information
Our 12 month Gregorian Calendar is partially based on the 12 Lunar Cycle that often (but not always) occur in one year but individual calendars months (like August) are no longer in sync with the (approximately) 29-day lunar month (i.e. the time between two New Moons).
This results in some months (e.g those with 31 days) having two Full Moons or two New Moons.

The term "once in a Blue Moon" is not related to the number of Full Moons in one month but instead, the number of Full Moons or lunar cycles between two seasons.

Most calendars around the world have significant dates that represent the start of seasons. These dates are based on the Sun's position in the sky.

For example, in European calendars, the "Start of Spring" was usually celebrated on the 20th Mar (or 21st Mar), when the Sun is exactly level with the Earth's equator. This is referred to as Vernal Equinox where day and night are equal in length (Equi -"equal"; Nox -"night").
Likewise, the "start of summer" is usually 21st Jun or Solstice, when the Sun reaches its highest position in the sky, resulting in the longest daylight hours.

In Asian calendars, the "start of spring" (Lichun, 立春) is actually marked by the halfway point between the December Solstice and Vernal Equinox, i.e. when the Sun is 45 degrees behind (or 315 degrees in front of) its Vernal Equinox position.

The actual answer
How does the Blue Moon fit in to all of this?
Most of the time, there are three Full Moons between Equinox and Solstice (i.e. between seasons). But occasionally when a Full Moon occurs on or near the Equinox or Solstice, there will four Full Moons between the seasons. The third moon of a four moon season is called the "Blue Moon" (It will take another essay to explain why).

Consequences and Complications
Having an extra Full (Blue) Moon between seasons makes things a little bit messy, because cultural and religious festivals like Easter and Chinese New Year are based on lunar and seasonal dates.
For example, Chinese New Year is always celebrated on the New Moon closest to Lichun (the start of spring based on the Sun's position).
When there is a Blue Moon between seasons (like in 2013) it can result in the date of next Chinese New Year moving back (e.g from February to January) by almost half a month. Over several years, this gradual shift can result in Chinese New Year moving into winter months like December or November.

To accommodate this, extra/double months have to be added into the Chinese Lunar Calendar during certain years in order to push forward significant festivals, e.g. so that Chinese New Year stays close to spring/LiChun.

Phew ... that explanation was a little bit more complicated and longer than I thought!

June Solstice in Singapore

This week is June Solstice week, where the Sun reaches its most northerly point in the sky. Of course, this event is not due to the Sun's actual movement but instead the movement and tilt of Earth. Every year around 21st June, Earth's north pole points more towards the Sun than at any other time of year. This causes a number of significant effects here on Earth.

June Solstice signifies the start of summer in the northern parts of the Earth as well as the longest daylight hours for the whole year. At the same time, it also marks the start of winter and the shortest daylight hours in the southern hemisphere.
There's often a great deal of excitement and sometimes celebelation associated with solstice particularly in places like stonehenge in the UK, where crowds gather from sunrise (around 5am) to sunset (around 9:30pm). The stones themselves also mark the Sun's position at solstice.

Stonehenge - Credit: Pete Strasser - NASA.gov

In Singapore, the effects of solstice are a little harder to spot as near the equator the Sun's position varies only slightly throughout the year.
However, here are some of the signs to look out for in order to notice the solstice from 1 degree north of the equator:

1. Longest daylight hours and shortest night. As Singapore is technically in the northern hemisphere by 1 degree, we also experience the longest number of daylight hours for the year. How long? Exactly 12hours 11minutes 48seconds, from sunrise to sunset. Compare this to the shortest daylight hours of 12hours 3minutes 2seconds in December, the difference is only 8 minutes. Not much to celebrate about, but it is noticeable particularly if, like me, you find yourself reaching home around 7pm. Whilst walking home from the MRT station, bus stop or waiting for a ride, look up at the sky and see if it looks any brighter than usual. A slightly later sunset at 7:16pm should make the sky look brighter than at other times of the year.

Sunset/dusk in June - Longer daytime, later sunset, slightly brighter sky.

Sunset/dusk in April - slightly darker than in June.

2. Sunrise, Sunset and Northern Sun
If you're heading out to work or school around 7:30am or 8am, you may notice that the morning Sun is positioned slightly more to the left (i.e. North) than usual.

June morning Sun to the left (north) of the Science Centre entrance - After June 21st the morning Sun will gradually make its way south (towards the right)

After 21st June, take a look at the Sun every now and then over the next few months around 8am. You should find the Sun gradually moving more towards the right (i.e. south) every week, until it reaches the December solstice position on 21st December.
Similarly at sunset, the afternoon/evening Sun should be located more towards the right than usual. This can be a bit annoying if you happen to own a house, flat or condo with north-facing windows, thinking that you'll escape the brightness and heat of the afternoon/western Sun. Around June Solstice, you'll start to find what was once a nice shady spot is now lit by bright sunlight, as that north facing window is now tilted slightly towards the Sun for most of the day. Those with south-facing windows will experience the same thing in December.

3. Noontime Shadows
Between 12:30pm and 1:30pm, the Sun is at its highest point in the sky but as the June Sun is at its most northern point, midday shadows on the ground will be at their longest as compared to other times of year.

June Solstice Shadows - Longest noontime shadows. Shadows point South

Morning Shadows in June - Sun rises from north-east, shadows point south-west 

If you compare your shadow at midday over the next few months you should find it becoming gradually shorter and shorter until finally its directly below your feet around late September, when the Sun is directly overhead (Autumnal Equinox). Also, as the Sun is located towards the North, all the June shadows should point in the opposite direction towards the South.


All parts of the world, will experience the effects of solstice in one way or another, the most obvious being  in those parts furthest from the equator.In Singapore, the changes may be small, but the clues to spot them are all around us, we need only stop for a while and look around at the environment we live in.

There are a number of other times in year in which the Earth's tilt causes other seasonal effects, such as the the position of the Sun, daylight hours, sunrise, sunset, planet growth, animal migration and seasonal weather patterns. Some of these changes have even influenced the dates of well know holidays and celebrations such as May Day, Halloween, Mid-Autumn Festival, Christmas and Chinese New Year as the movement of objects like the Sun and Moon, have formed the basis of many calenders for thousands of years.
The world may be full of different cultures, but we all share the same sky.
Happy Solstice everyone!