Sidewalk Astronomy Night is a programme where amateur astronomers get together and setup their telescopes at public areas to provide the public an opportunity to see, with their own eyes, celestial objects through telescopes. At the same time, the public will also be provided with information of what they are seeing, with the hope that it could raise public interest in astronomy and space science.
This year, our National Space Agency (ANGKASA) will be organising a Sidewalk Astronomy Night on Oct 29. Details of the programme are as follow:
Date: 29 Oct 2010 (Saturday) Time: 8 – 10 pm Venue: Taman Tasik Titiwangsa (previously site of Eye On Malaysia) Kuala Lumpur
All are invited to join this programme. Admission is free.
Apart from ANGKASA, other astronomical bodies around Klang Valley, i.e. Starhunter Astronomy Society, Starfield Instruments Supply, Starfinder Astronomy Society and Jabatan Mufti W.P, KL will also be joining in the programme.
The Moon and planet Jupiter will be easily visible. If weather and sky conditions permit, we can also see some bright constellations such as Cygnus and Pegasus.
Two days ago, the almost full moon had a meeting with Jupiter. And I was there to take a group photo of them.
The top left is (of course) our Moon. Bottom right is Jupiter. Click photo to enlarge. Credit: thChieh.
This picture is a composite of two pictures – one exposed for the Moon and the other exposed for Jupiter. It is impossible to get this picture in one shot, because the Moon is too bright and Jupiter is too dim (relatively speaking; Jupiter by itself is consider very bright). If the picture is exposed correctly for the Moon (meaning with a fast shuttle speed), then Jupiter will not show up. If exposed correct for Jupiter (meaning with a slow shuttle speed), then the Moon will be over-exposed. So we need a composite to get the best of both worlds.
After I took the picture and looked at Jupiter in the camera screen, I felt very unsatisfied. Jupiter was not a nice round dot. It was oval. Camera shake? Maybe. I took it again. And again. Still the same oval shape. Maybe the tripod is OK but Jupiter had drifted when the picture is taken? I don’t think so – the exposure time is just 1 second or less and the zoom is not that big (125 mm focal length). I give up on trying to understand why and go back into the house.
I loaded the images into my computer and when I opened the files, voila! Mystery solved! THE MOONS! Jupiter’s moons blended together with the planet and make the “dot” oval. I can’t believe it. I never realised that Jupiter’s moons can be so easily captured. Just a camera plus a 18-135 mm lens* plus a tripod were all that you need! I fired up Stellarium to check on the positions of the moons, and yes, they were where they were supposed to be.
Look carefully at Jupiter at the bigger version picture; you may be able to see its moons – two above (Callisto & Ganymede) and two below (Io & Europa). I cropped it out as below, just in case you are having trouble seeing it. The quality may not be spectacular, but still, to be able to capture the moons is something that I’ve never think of just by using an off-the-shelf camera.
Comparison of Jupiter taken with Nikon D70, 18-135 mm lens with Stellarium.
The Moon had moved to the east a day later, so it was now below and farther away from Jupiter.
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*If you are wondering why I’m using 125 mm focal length instead of 135 mm that the lens can offer, the answer is I don’t know. I actually set it to 135 mm, but I think maybe the lens slid back a bit due to gravity when I pointed the camera to the sky. A lesson learned here is that I may need to secure the lens to prevent any movement. What I can think of now is using a (or a few) rubber band.
Recently, I kept seeing pictures of aurora in the web. It’s not a surprise since the Sun is quite active lately. What a coincidence is that I also kept on hearing the word “aurora” from the people around me. We live at the equator, most of us only heard of but never really know what an aurora is, thus aurora is not something you’ll talk about in your daily conversation with others.
Is that a sign that I’ve to finish my article on aurora which I’ve plan to write long long time ago? I’ll take that as a Yes.
So, what is an aurora?
Wikipedia answer: “An aurora (plural: auroras or aurorae) is a natural light display in the sky particularly in the high latitude (Arctic and Antarctic) regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere.” In the northern hemisphere, it is called aurora borealis (northern lights) whereas in the southern hemisphere, it is called aurora australis (southern lights).
We always see aurora as static, because most of us only see aurora through pictures, which only capture it as a moment in time. If we can look at an aurora over time, as in the videos below, we can see that they are in fact changing and “moving”. This is why some time they are also called “the dancing lights”.
You must watch all the videos below because they are just beautiful! I guarantee you will not regret.
Astronauts Capture Aurora Australis from the International Space Station. If you are an astronaut, you also can observe aurora, but from above looking down, rather than from below looking up! Click here for more pictures of auroras from space.
For an aurora to happen, you need three ingredients – charged particles, magnetic field and atmosphere. The charged particles come from the Sun, and the magnetic field and atmosphere is from Earth*. Our Sun is an active ball of gas; it constantly gives out streams of charged particles known as solar winds. When these charged particles reach Earth, our Earth’s magnetic field guides these particles to the north or south pole, where they collide with air molecules in the upper atmosphere (at altitudes above 80 km). The collisions excite/ionise the air. When the electron returns to its original energy level or recombines with the air molecule, energy is release in the form of light creating the visible aurora. See the video below for a nice animation on how aurora is forms.
Click here for a more detail (and longer) video on how aurora forms.
Since the charged particles will follow the magnetic field lines to the north and south pole, aurora is usually visible in the far northern and far southern parts of the planet, in a band known as the auroral zone. The auroral zone is typically 10 to 20 degrees from the magnetic pole. However, during a geomagnetic storm (in simple words, when the Sun is more active), the auroral zone can expand to lower latitudes making aurora visible to temperate latitudes. Large magnetic storms are most common during the peak of the eleven-year sunspot cycle or during the three years after that peak. The current solar cycle predicted to peak around 2013/2014, so we can expect more light shows for the years to come.
Click here for animation. The IMAGE satellite captured this view of the aurora australis on September 11, 2005. Shown in the image is the ring of light that the solar storm generated over Antarctica, glowing green in the ultraviolet part of the spectrum. Because the Earth’s magnetic field is three-dimensional, the aurora appears as an oval ring around each of Earth’s pole. It isn’t a perfect circle because the Earth’s magnetic field is distorted by the solar winds. From the Earth’s surface, the ring would appear as a curtain of light shimmering across the night sky.
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Colours of the Aurora
Variation of colours in the aurora with altitude. Credit: Causes of Color
If we look at pictures of aurora, we can see that aurora comes in different colours, with green as the most common. As we all know (do you?), our atmosphere consists of different compounds such as nitrogen and oxygen. The colour of the aurora depends on which gas in our atmosphere is being excited, and on how excited it becomes. Oxygen is responsible for the green and red colour; nitrogen causes blue and deep red hues.
Oxygen is unusual in terms of its return to ground state after excitation: it can take three quarters of a second to emit green light and up to two minutes to emit red. However, collisions with other atoms or molecules will absorb the excitation energy and prevent emission. At the top of the atmosphere, there has a higher percentage of oxygen and it is sparsely distributed such that collisions are rare. This allows time for oxygen to emit red. Collisions become more frequent progressing down into the atmosphere, so that red emissions do not have time to happen thus only green is visible, and eventually even green light emissions are prevented at even lower altitude.
This is why there is a colour differential with altitude; at high altitude oxygen red dominates, then oxygen green and nitrogen blue/red, then finally nitrogen blue/red when collisions prevent oxygen from emitting anything. Green is the most common of all auroras, followed by pink, a mixture of light green and red, followed by pure red, yellow (a mixture of red and green), and lastly pure blue.
Watch the video above The Aurora again and see if you can spot the layers of different colour with altitude.
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*Earth is not the only planet to have auroras. Auroras occur on other planets too – Jupiter, Saturn, Uranus and Neptune also have their own light shows since they also have magnetic fields and atmosphere. Similar to the Earth’s aurora, they are visible close to the planet’s magnetic poles.
Jupiter Aurora. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Saturn Aurora. Credit: NASA, ESA, J. Clarke (Boston University), and Z. Levay (STScI)
Crescent moon is always a lovely sight to behold, just imagine you can have two at one go plus rings as bonus.
Credit: NASA/JPL-Caltech/SSI
These are Saturn’s rings and moons taken by the Cassini Spacecraft. The smaller one (just below the rings) is Enceladus and the bigger one at the bottom is Tethys. I don’t have anything to comment, the picture is posted here purely for its beauty, and I don’t think anyone will disagree with me.
Quick facts: Enceladus is 504 km across and Tethys is 1062 km across. This view was obtained at a distance of approximately 272,000 km from Enceladus and 208,000 km from Tethys.
We never saw Vesta in such details before. The best we get before this is an image from Hubble Space Telescope, and it is a blur. Only last month, when a spacecraft called Dawn enters orbit around this second largest asteroid in the asteroid belt between Mars and Jupiter, do we get a good look at it, and wow!
This asteroid is big (in asteroid sense), roughly 500 km across and clearly it’s not a sphere. That is the reason why it is not qualified as a dwarf planet. The image shows a lot of details such as craters, grooves and dark streaks. Also can be seen is the different distribution of craters on the surface, with more cratering on the upper left (north) and smoother region on the bottom right (south). This mystery and many others to come, will definitely keeps scientist busy for years.
Here is a cool video showing full rotation of Vesta. Clearly visible and a mystery, is the parallel grooves near the equator.
Personally, I’ve quite a feeling on this mission, because I’ll been following it since its launch in 2007 (and even reported on it – on another forum since this blog has not been born yet). After 4 years of sailing in space, it finally reached its destination. Think back, in these 4 years, what have I achieved on Earth?
Last month (April 21) marks the one-year anniversary of the Solar Dynamics Observatory (SDO). Over the past year, SDO has captured every moment of the Sun in details that we had never seen before. The mission has returned unprecedented images of solar flares, prominences, filaments, coronal mass ejections (CMEs), and towering loops of magnetic plasma.
The mission has put together some of the most beautiful, interesting, and mesmerising events seen by SDO during its first year, and they would like you to vote for your favourite video from this collection. The voting ends tomorrow (May 5), so it still not too late to choose your favourite.
This video of the space shuttle launch is just amazing! The video is long – about 45 minutes – but is totally worth the time to watch. Each shuttle launch is documented by over 125 cameras providing spectacular imagery of the event. Here is a look at some of the footage from different angles in slow motion, with narration to let you know what you’re seeing.
I strongly recommend you not to miss this. If you can’t finish watching it in one go, then split it into few times, just like what I did. Make sure you watch it till the end, you definitely will enjoy it and learn a few things about the launch.
