Ted Talks (Aftermath)

I have meant to post this update weeks before but I couldn't find the excerpt to the talks. Now that I am able to find it, I finally get to update this. The talks were brilliantly well-presented with ideas that were mind-blowing and revolutionary. I will just paste the link of the recap of the stunning talks from a Ted blog so that I can share with you what exciting discoveries humankind have uncovered and what awaits us in the future.

A huge thank you to Gary who accompanied me to the event.

http://blog.ted.com/out-of-this-world-a-recap-of-the-stellar-talks-in-session-4-of-ted2015/

Upgrades

It's 4am in the morning now and I have just came back from shopping at Mustafa Centre. I was planning to get a name card holder for some time now because my phone case is fully chucked with name cards. I have the old Singapore Sidewalk Astronomy paper name cards, the newer and better quality Singapore Sidewalk Astronomy name cards, and some of Gary's Astro.sg name cards. My phone casing was bursting at the seams and I thought it was an appropriate time for me to get a proper holder.

I also thought to buy a voice amplifier for future astronomy sidewalks. This is purely experimental. Instead of repeating myself over and over again about what they are going to see whenever someone next in line comes up to view my scope, I could just use this device and speak to everybody who is queuing. I could also give mini-lectures if the sky doesn't hold up. It's also a good idea to get this because we can reach out to the public who are further away from us and are curious to know what we are doing but are shy to approach us. I don't want to shout across for them to come over to have a peek as I may seem aggressive and may easily scare them off. Hopefully it works out as planned. If someone in our group is keen to do the talking and is an articulated orator, then I shall pass the PA system over for an overall improvement during sidewalks.

Sidewalk @ Queensway Tea Garden Mac's

We held a sidewalk session at Tea Garden Mac's at Queensway last night for a small crowd. It was just a 10 mins walk from where I was staying. I noticed Singaporeans are quite a shy lot. Many people just walked by, stole a few glances at the telescope and carried on with their journey. Gary did his magic of pulling in a small crowd and interacting with them. I think I should be more proactive in reaching out to these people but sometimes I really don't know how because I am a rather introvert person myself.

Thanks to Haz, Dave, Ava, and Gary for coming over to hold this wonderful session with me nonetheless. Photo credits to Haz.

Scrapbook

I have started work on the scrapbook idea that Gary came up with. It serves two main purposes:

1) Use it for our public outreach sessions so that the public could appreciate and have a better understanding of what they are seeing through our telescopes with enlarged, detailed pictures and some basic infomation.

2) Serves as a backup to teach basic astronomy when the sky doesn't hold up.

Using Microsoft PowerPoint, I have come up with some slides. I have sorted it into chapters in the table of contents and have completed the first chapter, which is solar astronomy. I am currently working on observable planets and the remaining chapters may take me some time to complete. 

Everything is in draft now. I have done some brushing up while doing the slides, reading about the subjects that I feel are important and then condensing them into bite-size information for the layman.

I am still unsure if the science or the contents are right. I will need to gather opinions and reviews here and there once it's completed.

Once it's done, I will save all the slides into a thumb drive and get them printed onto magazine quality paper and bind them into a scrapbook at Queensway Shopping Centre. If it's not too costly, I may chose to have a better quality paper to make the scrapbook.

SG50 @ Bishan Park

It began pouring with thunder at 7pm when I was in a taxi and on my way to Bishan Park to help Dave and Gary with our public outreach session last Saturday. We thought it'd be great to setup there as the expected crowd numbers will soar because of the SG50 concert that was being held directly opposite of where we were.

A message came via Whatsapp while I was still in the taxi. Dave and Ava had sought refuge from the rain at a nearby housing estate. So, I informed the cab driver of the new destination.

Met the both of them there and they told me Gary was at the park's Macdonald's. I was surprised to see Jason and his girlfriend, Amanda, seeking shelter at the housing estate together with Dave and Ava.

That was also the first time I met a new friend. His name is Valdric and he has this intriguing telescope that has Wifi function and its motion can be controlled by a mobile phone.

Luckily for us, the rain stopped after awhile. Jason and his girlfriend left for dinner. Dave, Ava, and I went over to Macdonald's to look for Gary and he was there slicing up new name cards that came with a QR code which he had designed himself. Gary also showed us his "new" 80mm refractor telescope. It's a long, bright yellow tube that looked cute in some way.

The clouds began to slowly dissipate and all of us went to setup our equipment. I had the honour of opening Valdric's telescope case and had a look at the equipment before he set it up.

Uncle Wayne came later with his binoculars and helped us entertained the crowd.

Some of us were looking at Jupiter, some at Orion's Nebula. When the SG50 concert ended, huge crowds started pouring in. Gary signaled for them to come over to have a peek through the telescopes. We had a busy field day showing and explaining to people what they were seeing. We were also being constantly mistaken as part of the SG50 concert tie up, which we were not. Ha ha.

The rain clouds came in and blanketed the entire sky again at about 11pm and there was nothing to be seen, not even Jupiter. We thought it was best to pack up and then have supper before heading back home.

To sum it up, it was a tiring but rewarding sidewalk session.

Here are some pictures that Gary took at the sidewalk session.

Valdric's Wifi telescope.

    

IN.Genius

This morning, Gary sent us a news article through Whatsapp, letting us know that a Singaporean team from a private company called In.Genius has successfully sent 3 rats up into the stratosphere via air balloons and they all came back alive.

http://www.channelnewsasia.com/news/singapore/singaporean-team/1716002.html

This preliminary test was conducted to ensure that it is safe to send the very first Singaporean up during the Singapore National Day celebration on the 9th of August 2015. A series of tests are still necessary before that actually happens.

I have heard a great deal of good things that the founder of IN.Genius was trying to do. The founder is by the name of Mr. Lim Seng. He was trying to show that Singaporeans can dream big even though ours is a small island nation. He is a local prodigy by any standards.

However, his ostentatious ideas have met with stiff resistance, garnering him many naysayers - from the public skeptics to government approvals. Mr. Lim Seng has persisted to this very day for the past couple of years or so. One such incident was the "No Go" by the Civil Aviation Authority of Singapore, or CAAS for short. IN.Genius was not allowed to conduct the balloon testing locally as air traffic would be severely affected in a jam packed air space in Singapore. So the IN.Genius team test-launched it in India instead.

http://www.channelnewsasia.com/news/singapore/no-to-space-balloon/1578984.html

For once, I am proud to call myself a Singaporean because of what Mr. Lim Seng is doing. He has paved the way and laid the first brick as a foundation for us, Singaporeans, to venture into space exploration. It is something that we can collectively look upon as a nation. We don't need anymore bankers, or lawyers, or aspiring politicians. We need explorers, pioneers, and inventors - people who not only dream, but dare to fulfill that dream and inspire others to step forward.

I want to congratulate Mr. Lim Seng for the successful trial. I hope that his endeavour is seen and appreciated by all on Singapore's coming birthday.        

Below are some pictures that were taken during an IN.Genius roadshow at Orchard Road. Photos credits to Ava.

The proposed capsule that carries the first Singaporean up.

Astronomy Notes

I have collected astronomy notes from about a year ago when I was still fresh in the hobby. Some of them were collected from the web, some through conversations with fellow astronomers, and some of them through personal experiences. I thought I'd share it with my viewers. I will save myself the trouble of taking dozens of screen shots and just copy and paste the whole thing at the bottom.

Astronomy Notes

Light travels at approximately 300,000km/s or 3 x 10^8 m/s

Seasonal brightest star: Aldebaran (Spring, Constellation Taurus) , Regulus (Summer, Constellation Leo) , Antares (Autumn, Constellation Scorpius) , Formalhaut (Winter, Constellation Piscis Austrinus).

Summer Triangle Stars: Vega (Constellation Lyra), Denub (Constellation Cygnus), Altair (Constellation Aquila).

Winter Triangle Stars: Betelguese (Constellation Orion), Siruis (Carnis Major), Procyon (Constellation Carnis Minor). 

Spring Triangle Stars: Regulus (Constellation Leo), Spica (Constellation Virgo), Arcturus (Constellation Bootes).

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Constellations of the ecliptic (astronomy):

Pisces 12 Mar - 18 Apr (38 days)

Aries 19 Apr - 13 May (25 days)

Taurus 14 May - 19 Jun (37 days)

Gemini 20 Jun - 20 Jul (31 days)

Cancer 21 Jul - 9 Aug (20 days)

Leo 10 Aug - 15 Sep (37 days)

Virgo 16 Sep - 30 Oct (45 days)

Libra 31 Oct - 22 Nov (23 days)

Scorpius 23 Nov - 29 Nov (7 days)

*Ophiuchus 30 Nov - 17 Dec (18 days)

Sagittarius 18 Dec - 18 Jan (32 days)

Capricornus 19 Jan - 15 Feb (28 days)

Aquarius 16 Feb - 11 Mar (24/25 days)

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Optics Terms:

Achromatic - An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus in the same plane. The most common type of achromat is the achromatic doublet, which is composed of two individual lenses made from glasses with different amounts of dispersion. Typically, one element is a negative (concave) element made out of flint glass, which has relatively high dispersion, and the other is a positive (convex) element made of crown glass, which has lower dispersion. The lens elements are mounted next to each other, often cemented together, and shaped so that the chromatic aberration of one is counterbalanced by that of the other.

Apochromatic - An apochromat, or apochromatic lens (apo), is a lens that has better correction of chromatic and spherical aberration than the much more common achromat lenses. Chromatic aberration is the phenomenon of different colors focusing at different distances from a lens. In photography, chromatic aberration produces soft overall images, and color fringing at high-contrast edges, like an edge between black and white. Astronomers face similar problems, particularly with telescopes that use lenses rather than mirrors. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus in the same plane. Apochromatic lenses are designed to bring three wavelengths (typically red, green, and blue) into focus in the same plane. Apochromats are also corrected for spherical aberration at two wavelengths, rather than one as in an achromat.

Doublet ED (extra low dispersion) lens might not be apochromatic. Apochromatic is only certified when the colour correction is good. Extra low dispersion describes the light dispersion ability of the lens. Apo is the false colour-free nature of a refractor telescope. Apo is the design, while ED is the lens. Almost all refractors have at least 2 types of lens sticked together as one collective objective lens. Apo objective lens could have one or more ED glass. Having ED glass involved alone does not mean that the final objective lens will turn out to be a true Apo refractor. How the glass elements are configured together also influences the false colour suppression. Some designs are so good that they can reduce a lot of false colour without the use of ED glasses at all. Not all lens designers or manufacturers agree on the exact design and definition of Apo and ED.

Apparent field of view--this is the width in degrees of the field as seen through just the eyepiece alone. If I have two eyepieces with the same focal length, the one with the larger apparent field of view will show more of the sky if inserted into the same telescope. This parameter is determined by the design of the lenses inside an eyepiece.

Curvature of field--good eyepieces provide a field of view which is flat. The focused image should be sharp from edge to edge. Star fields are a tough test of this characteristic.

Distortion--good eyepieces also have little distortion, this means if you viewed a piece of lined graph paper that all the lines would be straight and would cross at right angles. Distortion can be a problem for only a small section of the field of view, but curvature generally happens to the entire field of an eyepiece.

Exit Pupil--the lenses in an eyepiece form an image that floats in midair just outside the lens closest to your eye. When you observe you place your eye so that it can see this exit pupil image. If all is going as planned, the image size will fit with room to spare within your eye. The size of this image is the exit pupil.

Eye relief--the distance from the eye lens to your eyeball. This value is important to eyeglass wearers. If you need to have your glasses on to view the sky, there must be plenty of eye relief so that your eyeglasses will fit between the eyepiece and your face. Those of us who don't wear glasses to observe generally like some eye relief to avoid the feeling that I am jamming my eye lens against the glass lens of the eyepiece.

Focal length--the apparent distance from the lens to the object being viewed, in this case the image formed by your telescope. Long focal length eyepieces show a large portion of the image being viewed and short focal length eyepieces will allow a small section of the image to be inspected. This is how you choose the magnification of your optical system. Pick out a long focal length eyepiece, say 40mm to 24mm, and the system will give a wide field and low power. Select a short focal length eyepiece, around 8mm to 4mm, and you will get a high power, small field of view look at whatever is in the scope.

Ghost images--in poorly made eyepieces some of the light from a bright star can reflect about within an eyepiece and form faint images within the field of view. These ghost images can be subdued by multicoating the lenses in the eyepieces. Only the cheapest eyepieces nowadays are not coated to suppress this problem.

True field of view--this is the field of view of the entire telescope system, including the eyepiece.

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Technical Calculations For Telescope:

Magnification = Telescope focal length / Eyepiece focal length

Exit pupil = Telescope aperture / Magnification

True field of view = Apparent field of view / Magnification

Focal ratio = Focal length / Aperture  (Influences field of view and chromatic aberration. Fast focal ratio scopes typically offer a wider field of view than slow focal ratio, but the former has more CA than the latter.)

1 inch = 2.5cm = 25mm

General rule of thumb is to apply a maximum of 50x magnification per inch of aperture. Anything more is useless.

Advisable NOT to get refractors below 3 inches of aperture, Newtonian reflectors below 6 inches of aperture, binoculars below 30mm of aperture and more than 12x magnification.

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List Of Bright Stars:

1) Sun -- Magnitude -27

2) Sirius (Constellation Carnis Major) -- Magnitude -1.46

3) Canopus (Constellation Carina) -- Magnitude -0.72

4) Alpha Centauri (Constellation Centaurus) -- Magnitude -0.27

5) Arcturus (Constellation Bootes) -- Magnitude -0.04

6) Vega (Constellation Lyra) -- Magnitude 0.03

7) Capella (Constellation Auriga) -- Magnitude 0.08

8) Rigel (Constellation Orion) -- Magnitude 0.12

9) Procyon (Constellation Carnis Minor) -- Magnitude 0.34

10) Betelguese (Constellation Orion) -- Magnitude 0.42 *variable*

11) Achernar (Constellation Eridanus) -- Magnitude 0.50

12) Beta Centauri/Hadar (Constellation Centaurus) -- Magnitude 0.60

13) Altair (Constellation Aquila) -- Magnitude 0.77

14) Acrux (Constellation Crux) -- Magnitude 0.77

15) Aldebaran (Constellation Taurus) -- Magnitude 0.85 *variable*

16) Spica (Constellation Virgo) -- Magnitude 1.04

17) Antares (Constellation Scorpius) -- Magnitude 1.09 *variable*

18) Pollux (Constellation Gemini) -- Magnitude 1.15

19) Formalhaut (Constellation Piscis Austrinus) -- Magnitude 1.16

20) Denub (Constellation Cygnus) -- Magnitude 1.25

21) Becrux/Mimosa (Constellation Crux) -- Magnitude 1.30

22) Regulus (Constellation Leo) -- Magnitude 1.35

23) Adara (Constellation Carnis Major) -- Magnitude 1.51

24) Castor (Constellation Gemini) -- Magnitude 1.58

25) Shaula (Constellation Scorpius) -- Magnitude 1.62

26) Gacrux (Constellation Crux) -- Magnitude 1.63

27) Bellatrix (Constellation Orion) -- Magnitude 1.64

28) Alnath (Constellation Taurus) -- Magnitude 1.68

29) Miaplacidus (Constellation Carina) -- Magnitude 1.68

30) Alnilam (Constellation Orion) -- Magnitude 1.70

31) Alnitak (Constellation Orion) -- Magnitude 1.70

32) Alnair (Constellation Grus) -- Magnitude 1.74

33) Alioth (Constellation Ursa Major) -- Magnitude 1.76

34) Alsuhail (Constellation Vela) -- Magnitude 1.78

35) Dubhe (Constellation Ursa Major) -- Magnitude 1.79

36) Mirfak (Constellation Perseus) -- Magnitude 1.82

37) Wezen (Constellation Carnis Major) -- Magnitude 1.84

38) Alkaid (Constellation Ursa Major) -- Magnitude 1.85

39) Rasalhague (Constellation Ophiuchus) -- Magnitude 2.10

40) Mintaka (Constellation Orion) -- Magnitude 2.23

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Question: Are the colours of stars based on the intensity of nuclear fusion in the star's core or the cause of Redshift or Blueshift (assuming both stars are of the same mass and at the same fusion intensity)?

1) Blue colour has a shorter wavelength, higher frequency than orange in the visible light spectrum because some stars are so massive, they create fusion energy at a more intense rate. So imagine when you burn something with a blowtorch, it becomes red, orange, and if long and hot enough, it can turn blue.

2) Edwin Hubble had discovered that the Universe is expanding, everything is moving away from each other. The farther something is, the faster it appears to move away. There are also objects that are moving closer to us as during this expansion. This creates the Redshift and Blueshift. These phenomena can be explained using the Doppler Effect, since both light and sound have frequencies and wavelengths. The Doppler Effect is like when a car is travelling pass you while the driver is honking. As it gets closer to you, the wavelength of sound shortens and the frequency is high as it has a lot of energy, thus the sound is high-pitched. As the car travels away from you, the wavelength is stretched and has low frequency with less energy, thus the honking sound becomes low-pitched. So according to Doppler's Effect, light acts the same way - as an object moves away from you, the light it emits has lower frequency, an object moving towards you has higher frequency. These frequency corresponds to the colours they emit in the electromagnetic spectrum.

3) So back to my original question, if there are 2 massive stars of the same size and are undergoing the same intensity of nuclear fusion, but they differ hugely in distances relative to where we see them, does that mean that point 1 is not true but point 2 is, for this case? One of the stars is orange in colour because it is farther away, while the closer one shines blue. But in actual fact, one is not "burning" more intensely than the other, rather, it's the distance that determines the colour?

Answer: Redshift and blueshift are actually quite insignificant. Although astronomers can use it to measure relative velocity, the velocities involved are only a fraction of the speed of light. The measurement of redshift and blueshift in galaxies require sensitive instrumentation. If we were to assume that the doppler effect is causing a difference in colour of two stars (to the extent of causing one to be orange and the other to be blue), they would have to me moving at a very extreme relative velocity for it to happen. Secondly, if we are comparing two stars in our galaxy, or even another galaxy in the local cluster, the effect of the expansion of the universe is negligible. As big as galaxies and clusters are, gravity predominates over the expansionary force at these scales. The cosmological constant is a very small value in the field equations.

When we use spectroscopy on starlight, what we are looking at is an absorption line spectrum. The way that astronomers measure redshift and blueshift is via these absorption spectra. Absorption line spectra is produced when light of all wavelengths is emitted from fusion processes. When these photons pass through different atoms, those photons that correspond to the energy gap between atoms in a star will be absorbed. Because the schrodinger equations predict the exact energy levels of electron orbitals, these absorption lines always appear in the same place and have the same pattern without interference by the doppler effect. When we factor in the doppler effect, we would see the same pattern in the stellar spectrograph, but shifted towards the red or the blue. Since the absorption spectra consists of very sharp dark lines, any small shift towards the red or blue can be detected from spectroscopy. Because of spectroscopy, we can differentiate between redshift and blueshift from the actual surface colour of the star.

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Question: What keeps the stars from crashing into each other?

Answer: There is a very short answer to your question, and that is that space is very large, and there is lots of room for stars, moons, and planets to move around without colliding with each other. Often, when two objects look close together on the sky, one of them is much further away than the other. Therefore, they are not really close together at all. This is true for many of the stars in the constellations that we are familiar with, and it is true for stars and planets which look close to our Moon. The nearest stars are light years away, while the Moon is about a billion times nearer. Collisions between stars are believed to happen, but they must be very infrequent. Collisions inside our solar system happen fairly often between planets and comets or meteors. Each "shooting star" is an example of such a collision, and 2 years ago a fairly large comet collided with Jupiter.

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Stars - Formation, Classification and Constellations:

Stars are giant, luminous spheres of plasma. There are billions of them — including our own sun — in the Milky Way Galaxy. And there are billions of galaxies in the universe. So far, we have learned that hundreds also have planets orbiting them.

History of Observations:

Since the dawn of recorded civilization, stars played a key role in religion and proved vital to navigation. Astronomy, the study of the heavens, may be the most ancient of the sciences. The invention of the telescope and the discovery of the laws of motion and gravity in the 17th century prompted the realization that stars were just like the sun, all obeying the same laws of physics. In the 19th century, photography and spectroscopy — the study of the wavelengths of light that objects emit — made it possible to investigate the compositions and motions of stars from afar, leading to the development of astrophysics. In 1937, the first radio telescope was built, enabling astronomers to detect otherwise invisible radiation from stars. In 1990, the first space-based optical telescope, the Hubble Space Telescope, was launched, providing the deepest, most detailed visible-light view of the universe.

Star Naming Designations:

Ancient cultures saw patterns in the heavens that resembled people, animals or common objects — constellations that came to represent figures from myth, such as Orion the Hunter, a hero in Greek mythology. Astronomers now often use constellations in the naming of stars, with the International Astronomical Union, the world authority for assigning names to celestial objects, officially recognizing 88 constellations that cover the entire sky. Usually, the brightest star in a constellation is has "alpha," the first letter of the Greek alphabet, as part of its scientific name. The second brightest star in a constellation is typically designated "beta," the third brightest "gamma," and so on until all the Greek letters are used, after which numerical designations follow. See our overview of Constellations. 

Since there are so many stars in the universe, the IAU uses a different system for newfound stars. Most consist of an abbreviation that stands for either the type of star or a catalog that lists information about the star, followed by a group of symbols. For instance, PSR J1302-6350 is a pulsar, thus the PSR. The J reveals that a coordinate system known as J2000 is being used, while the 1302 and 6350 are coordinates similar to the latitude and longitude codes used on Earth.

A number of stars have possessed names since antiquity — Aldebaran, for instance, means "the follower" in Arabic, as it seems to follow the Pleiades, or Seven Sisters star cluster, across the sky. These possess scientific names as well — Aldebaran is also known as Alpha Tauri.

Formation:

A star develops from a giant, slowly rotating cloud that is made up entirely or almost entirely of hydrogen and helium. Due to its own gravitational pull, the cloud behind to collapse inward, and as it shrinks, it spins more and more quickly, with the outer parts becoming a disk while the innermost parts become a roughly spherical clump. This collapsing material grows hotter and denser, forming a ball-shaped protostar. When the heat and pressure in the protostar reaches about 1.8 degrees F (1 million degrees C), atomic nuclei that normally repel each other start fusing together, and the star ignites. Nuclear fusion converts a small amount of the mass of these atoms into extraordinary amounts of energy — for instance, 1 gram of mass converted entirely to energy would be equal to an explosion of roughly 22,000 tons of TNT.

Evolution:

The life cycles of stars follow patterns based mostly on their initial mass. These include intermediate-mass stars such as the sun, with half to eight times the mass of the sun, high-mass stars that are more than eight solar masses, and low-mass stars a tenth to half a solar mass in size. The greater a star's mass, the shorter its lifespan generally is. Objects smaller than a tenth of a solar mass do not have enough gravitational pull to ignite nuclear fusion — some might become failed stars known as brown dwarfs.

An intermediate-mass star begins with a cloud that takes about 100,000 years to collapse into a protostar with a surface temperature of about 6,750 degrees F (3,725 degrees C). After hydrogen fusion starts, the result is a T-Tauri star, a variable star that fluctuates in brightness. This star continues to collapse for roughly 10 million years until its expansion due to energy generated by nuclear fusion is balanced by its contraction from gravity, after which point it becomes a main-sequence star that gets all its energy from hydrogen fusion in its core.

The greater the mass of such a star, the more quickly it will use its hydrogen fuel and the shorter it stays on the main sequence. After all the hydrogen in the core is fused into helium, the star changes rapidly — without nuclear radiation to resist it, gravity immediately crushes matter down into the star's core, quickly heating the star. This causes the star's outer layers to expand enormously and to cool and glow red as they do so, rendering the star a red giant. Helium starts fusing together in the core, and once the helium is gone, the core contracts and becomes hotter, once more expanding the star but making it bluer and brighter than before, blowing away its outermost layers. After the expanding shells of gas fade, the remaining core is left, a white dwarf that consists mostly of carbon and oxygen with an initial temperature of roughly 180,000 degrees F (100,000 degrees C). Since white dwarves have no fuel left for fusion, they grow cooler and cooler over billions of years to become black dwarves too faint to detect. (Our sun should leave the main sequence in about 5 billion years.)

A high-mass star forms and dies quickly. These stars form from protostars in just 10,000 to 100,000 years. While on the main sequence, they are hot and blue, some 1,000 to 1 million times as luminous as the sun and are roughly 10 times wider. When they leave the main sequence, they become a bright red supergiant, and eventually become hot enough to fuse carbon into heavier elements. After some 10,000 years of such fusion, the result is an iron core roughly 3,800 miles wide (6,000 km), and since any more fusion would consume energy instead of liberating it, the star is doomed, as its nuclear radiation can no longer resist the force of gravity.

When the iron core of such a star reaches a mass of 1.4 solar masses, the result is a supernova. Gravity causes the core to collapse, making the core temperature rise to nearly 18 billion degrees F (10 billion degrees C), breaking the iron down into neutrons and neutrinos. In about one second, the core shrinks to about six miles (10 km) wide and rebounds just like a rubber ball that has been squeezed, sending a shock wave through the star that causes fusion to occur in the outlying layers. The star then explodes in a so-called Type II supernova. If the remaining stellar core was less than roughly three solar masses large, it becomes a neutron star made up nearly entirely of neutrons, and rotating neutron stars that beam out detectable radio pulses are known as pulsars. If the stellar core was larger than about three solar masses, no known force can support it against its own gravitational pull, and it collapses to form a black hole.

A low-mass star uses hydrogen fuel so sluggishly that they can shine as main-sequence stars for 100 billion to 1 trillion years — since the universe is only about 13.7 billion years old, this means no low-mass star has ever died. Still, astronomers calculate these stars, known as red dwarfs, will never fuse anything but hydrogen, which means they will never become red giants. Instead, they should eventually just cool to become white dwarfs and then black dwarves.

Binary stars and other multiples:

Although our solar system only has one star, most stars like our sun are not solitary, but are binaries where two stars orbit each other a pair, or multiples involving even more stars. In fact, just one-third of stars like our sun are single, while two-thirds are multiples — for instance, the closest neighbor to our solar system, Proxima Centauri, is part of a multiple system that also includes Alpha Centauri A and Alpha Centauri B. Still, class G stars like our sun only make up some 7 percent of all stars we see — when it comes to systems in general, about 30 percent in our galaxy are multiple, while the rest are single.

Binary stars develop when two protostars form near each other. One member of this pair can influence its companion if they are close enough together, stripping away matter in a process called mass transfer. If one of the members is a giant star that leaves behind a neutron star or a black hole, an X-ray binary can form, where matter pulled from the stellar remnant's companion can get extremely hot and emit X-rays. If a binary includes a white dwarf, gas pulled from a companion onto the white dwarf's surface can fuse violently in a flash called a nova. At times, enough gas builds up for the dwarf to collapse, leading its carbon to fuse nearly instantly and the dwarf to explode in a Type I supernova, which can outshine a galaxy for a few months.

Characteristics:

Brightness

Astronomers describe star brightness in terms of magnitude and luminosity. The magnitude of a star is based on a scale more than 2,000 years old, devised by Greek astronomer Hipparchus in about 125 BC. He numbered groups of stars based on their brightness as seen from Earth — the brightest ones were called first magnitude stars, the next brightest were second magnitude, and so on up to sixth magnitude, the faintest visible ones. Nowadays astronomers refer to a star's brightness as viewed from Earth as its apparent magnitude, but since the distance between Earth and the star can affect the light one sees from it, they now also describe the actual brightness of a star using the term absolute magnitude, which is defined by what its apparent magnitude would be if it were 10 parsecs or 32.6 light years from Earth. The magnitude scale now runs to more than six and less than one, even descending into negative numbers — the brightest star in the night sky is Sirius, with an apparent magnitude of -1.46.

Luminosity is the power of a star — the rate at which it emits energy. Although power is generally measured in watts — for instance, the sun's luminosity is 400 trillion trillion watts— the luminosity of a star is usually measured in terms of the luminosity of the sun. For example, Alpha Centauri A is about 1.3 times as luminous as the sun. To figure out luminosity from absolute magnitude, one must calculate that a difference of five on the absolute magnitude scale is equivalent to a factor of 100 on the luminosity scale — for instance, a star with an absolute magnitude of 1 is 100 times as luminous as a star with an absolute magnitude of 6. The brightness of a star depends on its surface temperature and size.

Color

Stars come in a range of colors, from reddish to yellowish to blue. The color of a star depends on surface temperature. A star might appear to have a single color, but actually emits a broad spectrum of colors, potentially including everything from radio waves and infrared rays to ultraviolet beams and gamma rays. Different elements or compounds absorb and emit different colors or wavelengths of light, and by studying a star's spectrum, one can divine what its composition might be.

Surface temperature

Astronomers measure star temperatures in a unit known as the kelvin, with a temperature of zero K equaling minus 273.15 degrees C, or minus 459.67 degrees F. A dark red star has a surface temperature of about 2,500 K (2,225 degrees C and 4,040 degrees F); a bright red star, about 3,500 K (3,225 degrees C and 5,840 degrees F); the sun and other yellow stars, about 5,500 K (5,225 degrees C and 9,440 degrees F); a blue star, about 10,000 K (9,725 degrees C and 17,540 degrees F) to 50,000 K (49,725 degrees C and 89,540 degrees F).

The surface temperature of a star depends in part on its mass and affects its brightness and color. Specifically, the luminosity of a star is proportional to temperature to the fourth power. For instance, if two stars are the same size but one is twice as hot as the other in kelvin, the former would be 16 times as luminous as the latter.

Size

Astronomers generally measure the size of stars in terms of the radius of our sun. For instance, Alpha Centauri A has a radius of 1.05 solar radii (the plural of radius). Stars range in size from neutron stars, which can be only 12 miles (20 kilometers) wide, to supergiants roughly 1,000 times the diameter of the sun.

The size of a star affects its brightness. Specifically, luminosity is proportional to radius squared. For instance, if two stars had the same temperature, if one star was twice as wide as the other one, the former would be four times as bright as the latter.

Mass

Astronomers represent the mass of a star in terms of the solar mass, the mass of our sun. For instance, Alpha Centauri A is 1.08 solar masses. Stars with similar masses might not be similar in size because they have different densities. For instance, Sirius B is roughly the same mass as the sun, but is 90,000 times as dense, and so is only a fiftieth its diameter. The mass of a star affects surface temperature.

Magnetic field

Stars are spinning balls of roiling, electrically charged gas, and thus typically generate magnetic fields. When it comes to the sun, researchers have discovered its magnetic field can become highly concentrated in small areas, creating features ranging from sunspots to spectacular eruptions known as flares and coronal mass ejections. Directly detecting the magnetic fields of other stars, however, can be difficult.

Metallicity

The metallicity of a star measures the amount of "metals" it has — that is, any element heavier than helium. Three generations of stars may exist based on metallicity. Astronomers have not yet discovered any of what should be the oldest generation, Population III stars born in a universe without "metals." When these stars died, they released heavy elements into the cosmos, which Population II stars incorporated relatively small amounts of. When a number of these died, they released more heavy elements, and the youngest Population I stars like our sun contain the largest amounts of heavy elements.

Classification:

Stars are typically classified by their spectrum in what is known as the Morgan-Keenan or MK system. There are eight spectral classes, each analogous to a range of surface temperatures — from the hottest to the coldest, these are O, B, A, F, G, K, M, and L. Each spectral class also consists of 10 spectral types, ranging from the numeral 0 for the hottest to the numeral 9 for the coldest.

Stars are also classified by their luminosity under the Morgan-Keenan system. The largest and brightest classes of stars have the lowest numbers, given in Roman numerals — Ia is a bright supergiant; Ib, a supergiant; II, a bright giant; III, a giant; IV, a subgiant; and V, a main sequence or dwarf.

A complete MK designation includes both spectral type and luminosity class — for instance, the sun is a G2V.

Stellar Structure:

The structure of a star can often be thought of as a series of thin nested shells, somewhat like an onion.

A star during most of its life is a main-sequence star, which consists of a core, radiative and convective zones, a photosphere, a chromosphere and a corona. The core is where all the nuclear fusion takes places to power a star. In the radiative zone, energy from these reactions is transported outward by radiation, like heat from a light bulb, while in the convective zone, energy is transported by the roiling hot gases, like hot air from a hairdryer. Massive stars that are more than several times the mass of the sun are convective in their cores and radiative in their outer layers, while stars comparable to the sun or less in mass are radiative in their cores and convective in their outer layers. Intermediate-mass stars of spectral type A may be radiative throughout.

After those zones comes the part of the star that radiates visible light, the photosphere, which is often referred to as the surface of the star. After that is the chromosphere, a layer that looks reddish because of all the hydrogen found there. Finally, the outermost part of a star's atmosphere is the corona, which if super-hot might be linked with convection in the outer layers.

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SO, YOU HAVE BOUGHT A SMALL TELESCOPE?

If you ask most amateur astronomers what telescope is best, they will probably advise you to check out the field and learn a bit about astronomy before you purchase. This advice is good, but what if you have already bought a small telescope? There is still hope for you! Read on and find out! 

As defined here, a small telescope is a refractor (a telescope with a big lens in the front of the tube, and an eyepiece holder at the back) with a lens diameter (D) or aperture between 50mm (~2 inches) and 90mm (~3.5 inches). Any refractor smaller than 50mm will be practically useless for astronomy, and any larger than 90mm is too large (and expensive) to qualify as a "small" telescope. Newtonian reflector telescopes (with a mirror at the back of the tube and the eyepiece holder near the front) between 3 inches and 4.5 inches will probably fall into the small telescope category as well.

In the eyes of overly serious amateurs, most inexpensive telescopes in these size ranges are useless. It is true that they have their shortcomings, but it is possible to do astronomy with these telescopes. If a small telescope was all you could afford, and/or you can't return your purchase, read on.

ESSENTIALS

There are some features a telescope needs in order to be useful for viewing astronomical objects.

First, the main or objective lens or mirror must be intact and relatively well-aligned. With a refractor, any large defect is usually apparent.

The telescope must have at least one eyepiece, and preferably two. A detailed explanation of eyepieces is given below, since the quality and sizes of the eyepieces you use will greatly affect your telescopic view.

The telescope must have a mount. Most inexpensive small telescopes will be mounted on a tripod and can be moved vertically and horizontally. Check the mounting for any excessive wobbles or shakiness. Unstable mountings, rather than poor optics, are the major disadvantage of these small scopes. If the mounting is shaky, try to steady it as much as possible.

The telescope should have a finder. Usually this is a small telescope that rides piggyback on your main telescope. In principle, it has a wide field of view and makes it easier to locate objects. Many small telescopes have unacceptable finders, so you may eventually want to replace yours.

MY TELESCOPE IS SUPPOSED TO MAGNIFY 236x!

 Any telescope can be made to magnify any amount, simply by changing the eyepiece. In practice, the high powers advertised with many small telescopes will be unusable. The eyepiece determines the magnification, so here is the scoop on eyepieces.

 Eyepieces are marked by their focal lengths. The longer the focal length of the eyepiece, the lower the magnification when used with a given telescope. The objective lens or mirror also has a characteristic focal length. The longer the focal length of the objective, the higher the magnification when used with a given eyepiece. You can find out the magnification (or power) a telescope will give by dividing the focal length of the objective (often marked on the box as F=700mm or something similar) by the focal length of the eyepiece.

For example, I use 4 eyepieces with my 60 millimeter refractor. The focal length of the objective is F=710mm. The focal lengths of the eyepieces are 20mm, 12.5mm, 9mm, and 6mm. The 20mm gives a magnification of 710 / 20 = 35.5x. This is a good low power for finding and viewing most objects.

Make sure you have a low power eyepiece in the range of 20x-40x. If you don't, you will have a tough time finding anything! The lower the power, the wider the field of view and the easier it is to locate objects. When you have a small, bright object like a planet in the field of view, you may wish to zoom in on it. This is where a higher power eyepiece will come into play. My 9mm eyepiece gives a magnification of 710 / 9 = ~79x.

Ridiculous eyepieces with focal lengths of less than 6mm are sometimes shipped with small telescopes. These are, without exception, poorly made and useless. They serve only to allow the manufacturer to advertise a high magnification. In practice, the view through a 4mm eyepiece will be uncomfortable, dim, and blurry. Just as useless is the Barlow lens, which effectively increases the magnification between 2x and 3x. A well-made Barlow might work, but the ones shipped with small telescopes have poorly-made lenses and sometimes will not even focus!

THIS IS TOO COMPLICATED! I JUST WANT TO LOOK AT THE SKY WITH MY TELESCOPE!!!!!!!!!!!!!!!!

 OK. This is actually a good time for it, if it's clear out and the Moon is up. Bundle up and take your scope outside. Put in your low power eyepiece and point the scope at the Moon. Center the Moon in the finder. Look in the eyepiece of the main scope. If you don't see the Moon, your finder isn't aligned. Luckily, the Moon is so bright that you don't need a finder. Just keep looking in the eyepiece and sweep the scope around the area until the Moon comes into view.

When you come across the Moon, it will probably be out of focus. So, find the focus knob and twist it until the Moon comes into focus. Did the scope move much when you did this? If so, your mounting is not the steadiest. You can either try to fix this or just live with it. What about the Moon's image? Can you see craters? The best part of the Moon to look at is the terminator, the line separating the sunlit side from the night side of the Moon. Shadows are long here, so detail will be enhanced. You should be able to get a very sharp image, with lots of craters and bright spots and dark spots visible. The Moon will be the most detailed astronomical object you will ever see in your telescope, so if it doesn't look good, then nothing else will. If something doesn't seem right, you might want to find someone to evaluate your telescope's optics.

Take some time to look at the Moon. You'll notice that the Moon appears to move out of the field of view. This is due to the Earth's motion, so you'll have to push the telescope every couple of minutes to keep up. Put in a higher power eyepiece and refocus. You may not be able to fit the whole Moon in the eyepiece field, now that the image is larger. Details are larger as well, but on the whole the image doesn't look as sharp. That's the trade-off of high power. You'll want to try different powers to find the eyepiece that gives the best view. Before you leave the Moon, adjust the finder scope so the Moon is in its center when it is centered in your main scope. This may take a bit of work, but it will help when you are looking for fainter objects.

Do you want to look at a planet? Do you know which planets are out now, and where to find them? If so, turn your scope on them. If not, you'll have to put off this step until you find out. Monthly astronomy magazines give the locations of the planets, usually on easy-to-read sky maps. In the meantime, let's look at a star. Any star will do, but you might want to choose a bright one. Center it in your finder, and it should be in the field of view of your low power eyepiece. If you were using a different power on the Moon, you may need to re-focus. The star will be in focus when it is smallest and sharpest. In fact, it should look just like a very bright point of light. Stars are so far away that they will always appear as tiny points when in focus. This doesn't mean that they are uninteresting. With your naked eye, you will notice that some stars are colored. You can study these colors more carefully under the telescope. In addition, some stars are double. Here are a few double stars that are good in small telescopes. You'll see that knowing the constellations and being able to read a star chart will help you out.

THE PLANETS

 Small refractors are often said to be good for the moon and planets, if nothing else. The planets will usually not be as detailed as they are through a larger telescope, but they are still worth looking at. In fact, most of the descriptions of planets in SKYTOUR are valid for small telescopes. You will be able to see the rings of Saturn and the moons of Jupiter and the phases of Venus when these planets are favorably placed in the sky. Because images in small telescopes are dim at high power, you will have to use lower powers than you would in a larger telescope. This can make the planets' disks appear disappointingly small. However, if you stick to powers in the range of 80x-120x, you should be able to make out increasing amounts of detail as your eyes become trained.

THE NEXT STEP: DEEP SPACE

If small telescopes are regarded as good planetary performers, they are usually written off for deep-sky objects. Galaxies, nebulae, and star clusters are very faint compared to the Moon and planets. The larger a telescope's aperture, the fainter the objects it can see. Telescopes with apertures of over 6 inches have become standard for deep-sky work. It is true that larger scopes will allow you to see fainter objects--there is no getting around that. In addition, more detail will be observed in bright objects with larger scopes. However, the brighter deep-sky objects are also visible in small telescopes, and there is no reason you should not observe them if you want to. First, you will need to have a good knowledge of the sky. There are many books on observing the sky with binoculars and small telescopes; many of them have star charts with the brightest deep-sky objects labeled. You should also get a planisphere, so you know what can be viewed when. Objects like the Orion Nebula (M42), Hercules Cluster (M13), and Andromeda Galaxy (M31) may even be labeled on the planisphere. Perhaps the best objects to view with small telescopes are open star clusters.

It is true that small telescopes are not the easiest (or even the most cost-effective, when purchased new) way to view the cosmos. Still, if you have one you can get a lot of use out of it and learn a lot about the sky before you graduate to a larger scope.

Rooftop Observatory

Last night, I had the honour of touring a rooftop observatory at Alfred's private apartment. It was truly quite an experience. Dave, Ava, and James were there. We had to climb a ladder to an attic and then exit to the rooftop where the open-air observatory was. Being afraid of heights, I had to bite the bullet and climb my way up in the name of astronomy. The ladder felt a little flimsy as I was ascending to "heaven" but Alfred assured me that it was sturdy enough to take even the weight of a massive dude like me.

We had to walk through the attic where Alfred keeps all his telescopes and other astronomical equipment. I made a quick count of the number of telescopes he had while we were walking to the observatory. It was something like, I don't know, 30? That's a crazy number of telescopes he own!

Exiting the attic and reaching the observatory, a super-massive C14 greeted our arrival. This 14-inch beast was sitting on a solid pier and it was pointing at Jupiter and a live image was projected onto James' 22-inch TV.

We also took turns to look through the telescope and gosh, what an awesome sight of Jupiter and its moons!

I really want to thank Dave and Ava for the invitation to such a wonderful night and Alfred for being such a gracious host for having us over to his impeccable rooftop observatory. I have also learnt that it was a customary practice to enjoy a little birds' nest drink while doing observations up there. How cute is that, huh? It was certainly an experience that no words could convey.

*Damn it, I should have took a picture of the ladder leading up to the attic as well. Next time, perhaps.

Jupiter!

 

 

YouTube Channels

*Disclaimer: I am in no way sponsored by these channels or making any profit from sharing these channels. I share them with you because I thought they were interesting enough.

This channel is awesome and I love his teaching style. He not only teaches astronomy but also some advance physics topics.

https://m.youtube.com/playlist?list=PL2yn_e5rlIW0bsNIOc3dEadJ6YwTOoj-Z

This channel features bite-size clips that dwell in different astronomy/space exploration topics. It's done in style and won't take up too much of your time.

https://m.youtube.com/channel/UCrMePiHCWG4Vwqv3t7W9EFg

Finally, there's StarTalk Radio hosted by a funny astrophysicist, Dr. Neil deGrasse Tyson. 

https://m.youtube.com/user/startalkradio

Are They The same?

Remember that astronomy textbook which I have posted about in my earlier blog entry? I started skipping a few chapters ahead because I was curious about our Sun and wanted to learn more about this ball of nuclear reactor to better appreciate solar observations in the future.

I wanted to know more about solar prominences and solar filaments but there was no mention of the latter in the textbook. So, I decided to Wiki about it and found that they were actually the same thing. I thought they were mutually exclusive!

Let's start from how the Sun spins and generates its magnetic field. Earth has a nice North Pole and a South Pole, it too, generates a magnetic field that shields us from deadly solar radiation and whatnot. 

However, the Sun does not behave like that. This huge ball of gas spins at a different rate depending on its latitude. At the equator, it spins and completes a rotation at about 25 days, at mid-latitudes between the equator and the poles, it's about 30 days, and about 35 days at the poles. This is something called Differential Rotation and is common among gaseous bodies in Space, such as Jupiter, Saturn ect.

This differential rotation causes a lot of magnetic fields to form on the Sun. Unlike Earth's single North Pole and South Pole, the Sun has many of such poles. These magnetic fields disrupt the Sun's convection currents and thus the regions where they reside become relatively cooler than the surrounding plasma. That is how sunspots are formed.

Prominences are formed along the magnetic field lines where cooler gas with lesser pressure is "trapped" by surrounding hot gases with a higher pressure, bottling the cooler gas along the magnetic field line in the Sun's atmosphere called the Chromosphere, creating a solar prominence.

When this happens at the edge of the Sun, against the black background of Space, we see it as a beautiful prominence - a fiery arch that glows.

Beautiful solar prominence. 

When we are seeing it head-on, with the Sun's overly bright photosphere as a background, it becomes an elongated dark line on the chromosphere known as a filament.

Mysterious-looking solar filament.

They are the same thing. It only depends on where they appear on the Sun.

Please correct me if I am wrong. Thank you!

Good News!

I was wondering why there was a sudden surge of Facebook 'Likes' on our little astronomy sidewalk page. There's been 16 'likes' for the past two hours now. Then I saw someone posted a Singapore Straits Times online article entitled "30 ways to live 'cheaply' in Singapore" on Facebook.

Guess what? Our little sidewalk group was mentioned in the article! We are at number 19.

Here's the link to the article: http://www.straitstimes.com/news/singapore/more-singapore-stories/story/30-ways-live-cheaply-singapore-the-worlds-most-expensive#xtor=CS1-10

Additionally, here's our little astro group Facebook page: https://www.facebook.com/SingaporeSidewalkAstronomy

I am so happy for the people working so hard in the Singapore Sidewalk Astronomy group to promote free public outreach sessions to the masses. Their hard work has gained some publicity, at least. Keep up the awesome work, people, gambateh!

Chinese Astronomical Terms

I am a Chinese by race but I do not pride myself as one because I find myself lacking in the language. Growing up in Singapore, Mandarin is not used as a main language to communicate. We have adopted English to be our main business language. I wouldn't dare say that I am highly proficient with English either, but I am calling a spade, a spade. So, I am at least an English literate.

As a stargazer who often does public outreach sessions, I feel a little disappointed and dejected when I can't communicate the science or even introduce some of the objects that we see in the night sky in basic Mandarin to our older Singaporean folks and to the Chinese migrant workers from The Peoples' Republic of China who were only literate in Chinese. I sometimes get the dirty look from them, too. They must be thinking, "Why does this Chinese dude not know how to speak Mandarin?"

Therefore, I have decided to draw some time to learn some basic astronomical terms in Chinese to communicate to this group of people in future public outreach sessions.

It's fascinating how the 5 planets that can be seen by the naked eye were named after the 5 important Chinese elements - Mercury (water), Venus (gold), Mars (fire), Jupiter (wood), Saturn (soil). 

Some additional words to learn:      

Comet - 彗星Huìxīng

Constellation - 星座 Xīngzuò
Siruis - 天狼星 Tiān láng xīng

Canis Major - 大犬座 Dà quǎn zuò

Taurus - 金牛座 Jīnniúzuò 

Orion - 猎户座 Lièhùzuò

Nebula - 星云 Xīngyún

Star cluster - 星团 Xīngtuán

Planets - 行星 Xíngxīng

The Seven Sisters (Pleiades) - 七姊妹 Qī zǐmèi  

Orbit - 轨道 Guǐdào

Asteroid impact - 小行星撞击 Xiǎo xíngxīng zhuàngjí

Moon's surface - 月球表面 Yuèqiú biǎomiàn

Craters - 陨石坑 Yǔnshí kēng

Meteor - 流星 Liúxīng

Meteorite - 陨石 Yǔnshí
Gravity - 重力 Zhònglì
Solar System - 太阳系 Tàiyáng xì
Galaxy - 星系 Xīngxì
Milky Way - 银河系 Yínhéxì 

I shall add more words and expand this list when anything comes to mind.