Look, a shooting star! (and what happened to Comet ISON?)

Our Solar System is an amazing place. There are a bunch of objects whizzing around the Sun including planets, asteroids and comets. Comets, often called "shooting stars", are very interesting. They are strikingly beautiful, relatively rare and worth studying.

Comet ISON, called the "Comet of the Century" on various media, has been a popular topic since its discovery on 21 September 2012. Below we explain some basic features of comets, illustrated with the example of Comet ISON.

What is a comet?

Great Comet of 1882.

In simple term, a comet is a dirty ice ball moving around the Sun. When passing close to the Sun, it evaporates and displays a thin cloud and sometimes a tail. In scientific terms, the ball is called nucleus and the cloud coma.

Originated from Kuiper belt or Oort cloud, a comet mainly consists of rock, dust, ice, and solid gases such as carbon dioxide and methane. Its dimensions are from few hundreds metres to few kilometres. 

Comet ISON: It is around 2 kilometres long according to Hubble Telescope observation. 

How do we name a comet?

Many naming systems have been used to name comets, therefore many comets have more than one name. 

Comets are named after the year of discovery...

Great Comet of 1680. Isaac Newton used it to verify Kepler's Laws.

Or after the names of discoverer...

Halley's Comet. Discovered and predicted by Edmond Halley, it can be seen every 76 years.

Or according to IAU (International Astronomical Union) system. Comets are designated by the year of the discovery, followed by a letter indicating the half-month, and a number indicating the order of discovery. Prefixes are used to describe the nature of the comet as well.

Comet ISON: Comet ISON was discovered in Russia by International Scientific Optical Network (ISON). Its formal name is C/2012 S1:

• C/ means that it is non-periodic. It is not likely to revisit the Solar System. Even if it comes back to the Sun next time, it will be another 400,000 years at least!
• 2012 denotes the year of discovery.
• S denotes the second half-month of September.
• 1 indicates it is the first comet discovered in that period.

What is the fate of a comet?

A comet can end up in very drastically different outcomes. The possible fates are:

• It comes back regularly, for example Halley's comet (period of 76 years).

The orbit of Halley's comet. The next visit is in 2024.

• The nucleus evaporates by the Sun's immense heat and radiation. The comet is said to fade or extinct. 

3552 Don Quixote.

• The nucleus may break up under the Sun's gravity or radiation. The remnants are still spectacular.

Breaking up of 73P/Schwassmann-Wachmann in 1995. This animation covers three days.

• It may fall into the Sun or smash into another planet. Comet Shoemaker-Levy broke up and collided with Jupiter in July 1994.

The brown spots indicate the crash sites of Comet Shoemaker-Levy on Jupiter in 1994.

Comet ISON: According to NASA Comet ISON Observing Campaign, it is very likely that Comet ISON does not survive the trip. Most of the nucleus has been disintegrated by the Sun's gravity pull and intense radiation. All hopes are not lost yet, as a very diffused remnant emerged after the passage. The following short clip shows the time-lapsed images on the NASA STEREO spacecraft. 

(Big animated gif, please be patient... it is worth it!)

We may have been denied the opportunity to observe a bright comet in the night sky, but the scientific data collected is highly valuable. Scientists will know more about the behaviour of comets when they are very near to the Sun, and are able to predict such comets (called Sungrazing comets) better in the future. 

Reference:

1. http://hubblesite.org/hubble_discoveries/comet_ison/blogs/measuring-the-size-of-ison-s-nucleus-point-spread-function
2. http://www.isoncampaign.org/karl/a-trail-of-questions

Halloween Special: Spirits in Space

It's a spooky halloween! Pictured above is an eerie nebula (SH2-136) that is
located about 1,200 light years away from us.
Photo credit: Adam Block, NOAO, AURA, NSF

If you have watched the recent sci-fi space movie, ‘Gravity’ (starring George Clooney and Sandra Bullock), you would have realised the extremely risky nature of space expeditions. When things go seriously wrong up there, death is almost inevitable.

For the Celtic people who lived 2000 years ago, Halloween falls on the eve of their new year, which happens on 1 November. On Halloween (31 October), it is believed that the boundary between this world and the next becomes unclear. This is when the ghosts of the dead start to return to earth.  As we prepare to dress up in our spookiest costumes this Halloween night, let us take the time to remember the heroes who have sacrificed their lives up in space...

Before Neil Armstrong became the first human to conquer the moon, there had been hundreds of animals that were sacrificed in the name of space exploration. Animals such as monkeys, chimpanzees, dogs, mice and other animals were used as test subjects in space to analyse the effects of space environment such as microgravity and radiation exposure on human during spaceflight.

Laika, the space dog, was the first animal in space. Unfortunately,
she never return as a re-entry plan had not been worked out.
Photo credit: NASA

Unfortunately, the earlier designs for spacecraft construction were still in the experimental phase. As a result, many animals that were sent for spaceflights died from starvation or dehydration during flight and in explosions while on board the shuttle. In some cases, the spacecraft in which the animals flew in were never recovered. This has led to speculations of abandoned ships that might be drifting in orbit together with their animal astronauts.

It is not just animal deaths that happened during space travels. In 1971, three Soviet crew members of the Soyuz 11 spacecraft, Georgi Dobrovolski, Viktor Patsayev and Vladislav had died in space as a result of space decompression during preparations for re-entry. Technically speaking, these are the only human fatalities that occurred in space (100km above sea level) so far.

The unfortunate crew members (from left to right: Georgi Dobrovolski, Viktor Patsayev and Vladislav Volko)
of Soyuz 11 were the first men to occupy the world's first space station.
Photo credit: Joachim Becker/ SpaceFacts

Thanks to the sacrifices of these animals, astronomers are now able to better understand the requirements of bringing a living being into space and also what lies in the universe out there. So the next time you wish upon a shooting star or wonder what that mysterious looking object in the night sky may be, remember that there is more than meets the eye...

Happy Belated Mid Autumn Festival!

Scobbers were so busy that we forgot that Mid Autumn Festival has past! Other than filling ourselves with mooncakes and playing with sparklers, we found out some amazing facts about the Moon that you might not know.

1. The Moon was created in a huge impact event by a Mars-like object

Artist's Impression of Giant Impact event (Source: Wikipedia)

Termed as "Giant Impact Hypothesis", most scientists think that the Moon was formed after a great collision between the Earth and a Mars-sized object 4.5 billion years ago. It explains why the Earth and the Moon spin in similar ways. Scientists also did some calculations to show that if the post-impact Earth revolves in a 2-hour period, i.e. a day is 2 hours instead of 24 hours, we can explain some of the observations.

After the direct impact, the cores of the Mars-sized object and the young Earth fused. The collision made the post-impact Earth spin so fast that a significant portion of the Earth's mass was ejected to form the Moon. By the conservation of angular momentum (a quantity to describe an object's rotation), the Earth-Moon system has similar spin directions.

Also, if the Moon was created from the Earth's material we can explain the fact that the Earth and the Moon have similar chemical compositions. For example the isotopes of oxygen and titanium were found to have identical ratios in both lunar and terrestrial rocks.

The Mars-like object is commonly known as Theia. In Greek myth, Theia is a titan who gave birth to Selene the Moon, Helios the Sun and Eos the Dawn. That's why we use Selen- (or lunar) and Helio- to describe stuff related to the Moon and the Sun respectively.

2. We are always looking at the same side of the Moon

Near side of the Moon (Source: Wikipedia)

Far side of the Moon (Source: Wikipedia)

Readers may have known this fact a long time ago. The "dark" side of the Moon has also been depicted in movie as well. Of course, there are neither giant robots nor military bases located at the far side of the Moon, as shown in the NASA Astronomy Picture of the Day on 16 September 2013. (Direct YouTube link)

There is nothing hidden behind the Moon as shown in photos taken by lunar probes. There are only craters at the far side of the Moon (the side that is not facing us). On the other hand, the near side of the Moon (the side that is facing us) has more interesting features. Apart from the craters there are valleys, mountains and maria (meaning Sea in Latin). Maria appear dark as they mainly contain iron compounds that are less reflective. People in ancient times made up stories for the observed patterns, such as the Moon rabbit legend in Chinese culture. Do you see it in the following picture?

Did you see the Moon Rabbit? (Source: Wikipedia)

Regarding why the Moon always faces with the same side, we need to know how gravity works. Every massive object in the universe attracts each other with a force called gravity. For instance, an apple drops to the ground due to the Earth's gravity (the apple also attracts the Earth, but the effect is very negligible due to the Earth's much larger mass). The strength of the gravity depends on the distance between two objects, so in this case the near side is more attracted than the far side is, making the Moon face towards the Earth with only one side. This effect is called "Tidal Locking".

3. One day, we will lose the Moon

The Moon exerts a gravitational force on the Earth (and vice versa), pulling the water nearer to itself and causing high tide on the Earth. As the Earth rotates underneath the water (we can imagine Earth being a solid rocky ball covered by water), it tugs the tides and loses some of the rotational energy. As a result, the Moon picks up some of the energy and then speeds up, ascending from its orbit. On average, the distance between the Earth and the Moon increases by around 4 cm every year.

It has an interesting side effect: as the Earth loses rotational energy it will rotate slower and slower. The length of a day will increase as a result, amounting to 2 millisecond per century. Wish to have 48 hours per day? Perhaps if you're still around after 4 billion years!

Reference:

1. Wikipedia. Moon. Retrieved 20 September 2013, from http://en.wikipedia.org/wiki/Moon
2. Geology 5835 - The Moon - Fall 2006. University of Colorado Boulder. Retrieved 20 September 2013, from http://lasp.colorado.edu/life/GEOL5835/Moon_presentation_19Sept.pdf
3. A New Model for the Origin of the Moon. Harvard University. Retrieved 24 September 2013, from http://www.fas.harvard.edu/~planets/sstewart/Moon.html
4. M. Ćuk, S.T. Stewart (2012). Making the Moon from a Fast-Spinning Earth: A Giant Impact Followed by Resonant Despinning. Science Vol. 338 no. 6110 pp. 1047-1052.

A small upgrade at SCOB

We have recently upgraded our observatory step by step! (pun intended) We have placed anti-slip strips on every step of the stairway to the Observatory. Scobbers Chua, Li Fei and Joanna have been busy under the hot weather :)

Now the steps will not become as slippery as before when it rains. Still, please go up the stairway one step at a time carefully :)

Venus: A Hostile Planet

It has been over one year since we witnessed Venus travelling in front of the Sun. We had an event last year to observe this rare phenomenon. Did you come?

Venus spotted in front of Science Centre's entrance.

Venus spotted in Johor Bahru, Malaysia.

In these few months we can observe Venus when we look towards the western sky. Often mistaken for a star, Venus appears as a very bright speck in the sky. It is so bright that it can actually cast shadows on Earth. 

Here are some short facts about Venus:

• It is Earth's Twin Sister. It is the closest planet to Earth, and similar to Earth in terms of size and mass.
• It is the only planet in the Solar System that is named after a female figure.
• On Venus, a day is longer than a year. One Venusian day is 243 Earth days, and one Venusian year is 224.7 Earth days.
• It is the hottest planet in the Solar System. The average surface temperature on Venus is 462 °C.

The last statement comes from the fact that Venus is shrouded by a thick atmosphere which consists of carbon dioxide and sulfuric acid. These gases form highly reflective clouds, preventing us from observing the Venus surface directly. In other words, the pictures we see are actually the Venusian atmosphere instead of the surface. Active volcanic activities happen on the surface of Venus, as evident in the radar image below. These make Venus an extremely hostile place for us to go!

Venus. The surface is obscured by thick clouds. (Wikipedia)

Craters on the surface of Venus. (Wikipedia)

Fortunately for us Earthlings, we can observe Venus from a safe distance (1.7 x 10^8 kilometres, or 17 followed by 7 zeros). Around 7pm to 9pm, we can observe Venus now until end of November. Look towards the Western sky and say hello to Venus! Science Centre Observatory opens every Friday from 7:45pm to 10pm, come and join us!

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

Return of Saturn

Saturn at Opposition
Every year as Earth makes it way around the Sun, it reaches a point where it is in line with an outer planet like Saturn. This is called opposition.

This year Saturn was at opposition on Sunday 28th April 2013. This means that Saturn has now started to appear in the eastern part of the sky during the early evening and appears at its brightest and biggest over the next few weeks.
Here's a photo of Saturn, which I snapped through our main telescope at the end of last Friday's stargazing session:

Saturn on 26th April 2013 at 10:20pm. - Taken with a HTC One X+ phone camera through a 16 inch cassegrain telescope with a 13mm Nagler eyepiece.

I was quite impressed at how this photo turned out, considering it was take with a phone camera held in front of the eyepiece. The fact that I was using an expensive, high power eyepiece lens (13mm Nagler) also helped.

Each year Saturn's opposition occurs about two weeks later than the previous year's. By the time Earth's returns to its previous position after its 365 day orbital journey, Saturn has also moved about 1/29th of the way around its own orbit.

As a result we see Saturn slowly drift in font of the the more distant star and constellations. Currently Saturn is making its way through the constellation Virgo. At next year's opposition it will be closer to Libra.


Saturn's tilt
Observing Saturn each year, you may begin to notice a change in the appearance of its rings. That is, some year you see more of them than others.
Like the Earth, Saturn is tilted. Its poles are tilted by about 26.7 degree. Depending on Saturn's position along its orbit we sometimes see Saturn tilted towards us or tilted away from us.

Back in 2009, Saturn was not tilted towards us at all, resulting in an edge-on view of the rings, making them appear very thin.

Saturn in 2009 - a thin edge on view of the rings, as seen from Singapore on 20th March 2009, looking East through our main telescope (16 inch cassegrain), with a Nikon D70 DSLR camera.

A brief sidetrack
Note that the vertical orientation of the rings in this photo has nothing to do with Saturn. It's because of our position on Earth. Here in Singapore, we are standing almost 90 degree from the north pole, thus we are standing sidewise relative to Saturn.

Late last year I was informed of a video (on youtube) that was using this very photo (amongst others) to falsely claim that Saturn has been knocked completely off its axis, signalling the end of the world. The video has since been removed and the world is still here.
Due to the curved surface of the Earth, observers in different locations and time periods will see Saturn at different angles.
Of course, I could have just rotated the camera or the photo to match Saturn's actual orientation.

Back to Saturn's tilt
Over the last few years, Saturn's "natural tilt" has resulted in its north pole facing more towards the Earth, resulting in the rings appearing wider and wider each year.

Saturn in May 2011 - taken through our 16 inch cassegrain reflector using a Nikon D70 DSLR camera.

Saturn in 2012 - taken through our 16 inch cassegrain reflector with a Nikon D70 DLSR camera. Rings look slightly wider than in the photos from 2009 and 2011.

By 2017 we will have the widest possible view of the Saturn's rings. After 2017 the rings start to appear smaller again as Saturn's north pole begins to turn away from us.

Saturn Rings in 2017 - Screen capture from astronomy software Starry Night Pro Plus.

Finally, Saturn is bright enough to see without the aid of the telescope as a bright yellowish dot in the sky, just slight east of the a bright whitest star in called Spica (part of Virgo). Each night over the next few months, its will gradually shift more towards the western part of the sky before disappearing from view around September/October time.
Each month the Moon will pass by Saturn in the sky. Look out for Saturn beside the Moon on 23rd May and 19th June.

What's up for April 2013

Stars and Constellations

For the past few months we've been focused on the bright stars and constellations of Orion, Taurus, Canis Major, Gemini, etc. During the early evenings of April, these stars are getting lower and lower  towards the West each day.

The bright reflected light of Jupiter is still visible in this part of the sky close to Taurus. By next month most of these stars will begin to disappear from view.

From April onwards, we start to shift our attention to the bright stars of the South, including the second brightest star in the night sky, Canopus, part of the constellation Carina. Canopus was also known in China as “Old Man of the South” for its southern location and sometimes red appearance in hazy or cloudy conditions.

The constellations Puppis, Vela and Carina form the ancient star pattern of the Argo Navis, representing the sailing ship from an Ancient Greek legend. 

The asterism (star pattern) the False Cross is sometimes confused for the Southern Cross (Crux), located nearby to the east.

Lying close to a dense part of our Galaxy, The Milky Way, several star clusters can be found when scanning the  area with binoculars.

1) & 2) M46, M47 – Two faint open clusters, east of bright star Sirius. M47 is the closer and brighter of the two. Small telescopes maybe required.

3) M93 – Faint wedge-shaped star cluster over 3000 light years away but visible in binoculars.

4) IC2391 – large open cluster of 50 stars surrounding the star Omicron Velorum. Best viewed using binoculars.

5), 6) ; 7) IC2581, NGC3293  NGC3114   Three fainter open star clusters located in front of the rich spiral arm of the Milky Way. Binoculars and small telescopes required.

8) Eta Carinae Nebula (NGC 3372) – a gas cloud surrounding the explosive variable star Eta Carinae. Several more stars are visible through binoculars and telescopes.

9) NGC3532 -  A large bright open cluster containing more than 100 stars forming an elliptical shape, 1300 lightyears away.

10) IC2602 (The Southern Pleiades)  Large open cluster of around 60 stars surround star Theta Carinae. Easy to spot with binoculars .

Saturn

Every year planet Saturn makes it appearance in the sky when it approaches opposition, i.e. when the Earth moves into alignment with both Saturn and the Sun. This period results in the closest distance between Saturn and Earth and the brightest and biggest view of Saturn in the sky.

Opposition occurs on 28th April 2013. So can we can expect to be observing Saturn at SCOB during the later part of the month.

Moon

Here are the dates for the main moon phases this month. We will be observing the Moon at our Friday night stargazing sessions on Friday 19th April and Friday 26th April.

Full Moon on 25th/26th April 2013 will result in a Partial Lunar Eclipse over Singapore, when the Moon enters the outer edge of Earth's shadow (the penumbra). However, this is only a very small eclipse, therefore the Moon will only darken slightly during 2am-6am on Friday 26th April, (Singapore time).

We will not be holding any eclipse viewing event at SCOB.

It may be difficult to notice any change in the moon's brightness.

Lyrids Meteor Shower

Finally, 21st/22nd April is the annual Lyrids Meteor Shower, one of the brightest showers of the year. We will not be organising any meteor shower events because most meteors cannot be seen in a bright urban environment like Singapore.

You can increase you chance of seeing a few meteors by going to a wide open area such as a sports field, beach or reservoir, but the frequency of meteors may only be about one or two per hour.

Meteor showers are best observed from midnight til dawn. Lyrid meteors originate from the north-east direction but can appear in any part of the sky.

First week of March 2013

Last Friday 1st March, the sky cleared for our first stargazing session of the month.
At first it was mostly cloudy with lightning in the distance so we delayed our start time to allow the weather to improve. Whilst waiting we had time to watch the dramatic sunset.

Sunset 1st March 2013 - Science Centre Singapore Observatory.

After 8pm the sky was clear. As usual, Jupiter was the main target for most of the first hour. Just like the previous week, the Great Red Spot (a giant storm) was faintly visible amidst one of the equatorial cloud belts.

Jupiter - Taken on 22nd Feb 2013 - from Science centre Singapore, through a 16 inch Cassegrain using a Nikon D70s. The great red spot is just visble on the left, beside the southern equatorial belt (lower dark band).

Jupiter - taken on 22nd Feb 2013 - through a 6 inch refractor. Sidewise orientation due to position of Jupiter in the sky (towards the west) and the position of the camera.

Later in the evening we turned are attention to the bright stars and constellations of Taurus, Orion and Canis Major. The great Orion Nebula (M42) was particularly stunning in the main 16-inch telescope, especially as there was no moonlight around.

After closing time, a few of us stayed back to take some photos of constellations:

Orion (top) and Jupiter (brightest, below) next to bright star of Aldebaran (in Taurus) - taken facing west - 1st March 2013.

Rectangular constellation of Gemini - bright stars Pollux (on top) and Castor (below). Facing North.

Close up of Orion

Close up of Canis Major - brightest star Sirius (top right).

Canis Major & Sirius (top right) with Carina & Canopus (below) - facing South

Waning Gibbous Moon rising from the East - 1st Mar 2013 10:45pm

Back at home, on Sunday evening (3rd Mar) there was was a bright flyby of the International Space Station (ISS) over Singapore. It would have made a nice photo as the ISS passed  right next to Jupiter and through Orion. However, 10 minutes before the flyby, a big patch of cloud blocked that part of thesky. ISS was visible for a few seconds through gaps in the clouds but all I got on camera was a faint streak as it approached Jupiter:

Faint trail of ISS passing by Jupiter on a cloudy night - 3rd March 2013 - Singapore 

Finally, the Moon is currently going through its waning phases as it moves around the morning side of the Earth. I've seen it every morning this week as I walked to the MRT to get to work. Every day getting closer and closer to the Sun as it approaches New Moon, resulting in its phase changing from a Large bright Gibbous to a half and then just this morning a thin crescent Moon.

Waning Gibbous Moon - 28th Feb 2013 - 7:30am - Singapore

Last Quarter Half Moon - 4th March 2013 - 7:40am - Singapore

Waning Crescent Moon - 7th March 2013 - 7:45am - Singapore

New Moon occurs on Monday 11th of March, which means it will not be visible this weekend as it will be too close to the Sun to see. By the end of next week it will return to the evening sky as a crescent Moon around 13th-15th March.

To see the Moon at SCOB this month I would recommend either Friday 15th March or Friday 22nd March.
____
Also we've seen no sign of Comet PANSTARRS C/2011 L4, which is at its brightest this week. However, its extremely low in the sky between 7pm and 7:30pm, almost exactly west after sunset. So far, its been cloudy every day in that direction so it will be challenging to spot it.