Theshyan Thirun

9 March 2022

Today’s session was quite interesting. The information given on Blackholes and Wormholes were quite sufficient and definitely interesting. I very much enjoyed today’s session due to the length of videos on Blackholes and Wormholes. The presenters were quite fast in the presentation and soft in their words but it was still a great presentation due to the videos presented. The Kahoot was also quite interesting, but definitely could have been done after showing all the videos and allowing us access to the slides for reference. 

Today’s session was the most interesting of the astronomy presentations this term, and could be elaborated much more. But still was sufficiently interesting and I definitely would want to watch the Kurzgesagt videos that were presented once more. 

Notes:

​​Blackholes and Wormholes

Blackholes

What are Black Holes

• A Region of spacetime with a gravitational effect so strong that nothing can escape it

• Looks completely black because it absorbs any light that touches it

Even though black holes are effectively invisible, you can infer their presence from the distorted space around the object

• No force can keep a dead star from collapsing under the influence of gravity

• However, instead of collapsing forever on a single point, as the star collapses, it gets closer to it’s event horizon

• Time on the “surface” of the star slows down relative to observers

• When the surface reachers the event horizon, time stop

How do Black Holes form?

Most blackholes form from the remnants of a large start that dies in a supernova explosion

• Small stars (less than 8 solar masses turn into White Dwarves

• Larger stars (8-20 solar masses) turn into Neutron Stars

• The largest stars (30 solar masses and up) turn into Black Holes

Black Hole Structure

• Relativistic Jet

• Photon Sphere

• Singularity

• Accretion Disc

Types of Black Holes

• Stellar Black Holes

  • Formed from the deaths of individual stars

  • Small compared to other black holes, but very dense

  • Consume surrounding dust, gas, and when they get big enough, other celestial bodies, in order to grow larger

• Immediate Mass Black Holes

  • Mass is too high to have formed due to the collapse of a single star

  • There are three theories as to how these could have formed

    • Theory 1: Merging of multiple high density celestial bodies

      • Mass was reached via the merging of multiple high-density celestial objects, such as black holes and neutron stars

      • Explains why they have so much more mass than stellar black holes

    • Theory 2: Runaway collision of stars in dense stellar clusters

      • Mass was reached via the collision of several stars

      • This could have happened in a dense star cluster, where two stars collided and set off a chain reaction, causing multiple stars to come together

    • Theory 3: They are primordial black hoes formed just after the Big Bang

      • Formed right after the Big Bang, when most of the universe was compacted into a few cubic centimetres, making it easy for black holes to form

      • Due to the high density of matter, it would be easy for black holes with a mass much higher than stellar black holes to form

• Supermassive Black Holes

  • Black holes with a mass higher than 100,000 solar masses

  • Exist at the center of every large galaxy

  • No exact cause for the formation of these objects has been determined

  • When these black holes feed, they are referred to as quasars, and essentially become galaxy sized stars

Wormholes

What is a wormhole

• A wormhole is a tunnel that connects two black holes or two points in space time

• It can act as a shortcut to reduce travelling times

Wormhole Theory

• Wormholes existence is in line with Einstein’s theory of relativity

• However, none have been found yet

Developments

• Black holes are a type of wormhole

• Only in this case, you’ll never get out of the wormhole

Schwarzschild wormhole

• First type of wormhole discovered

• Initially thought to collapses too quickly for anything to pass through

• Requires exotic energy

Reissner-Nordstrom wormhole

• A Reissner-Nordstrom wormhole is a wormhole that only travels one way

• These wormhole consists of a black hole at the entrance and a white hole at the exit

  • White holes are the opposite of black hole s, where yo can’t enter so basically a one way tour

• These wormholes aren’t

Einstein Rosen Bridges

2 March 2022

I felt that today’s lesson was slightly rushed despite the long time for the presentation. The order of the slides were very weird as they skipped many of the slides allowing for my notes to be quite confusing as some points. They also rushed many of the slides not allowing us time to sufficiently copy the information in the slides which caused some information such as that of Edmund Halley to be completely ignored and skipped. 

The time given for the group presentation task was sufficient and we had decided to do a task on Sputnik 2. We had managed to complete the task to our best ability. But luckily, we were not tasked to present as our script was not as complete as we wanted it to be. I found that the session was quite interesting at its beginning but due to the complexity at the order of the slides, it eventually became hard-to-follow and had caused some confusion but I did still manage to understand the information give.

I appreciate the presenters for spending their time organising their slides and it had given us appropriate information about the History of Astronomy and its significant peoples and discoveries as well as other 21st century advancements in astronomy. I did learn some information during this lesson.

Notes:

History of Astronomy

Significant People and Their Discoveries:

What is Astronomy?

1. The study of celestial objects and phenomena and the universe

2. It uses Mathematics, Physics, Chemistry to explain their origin and evolution.

3. Objects observed include planets, stars, galaxies and comets,

4. Phenomenon observed supernovae, pulsars and gamma ray bursts

Astronomy is…

1. Considered to be the oldest sciences studied

2. Origins dating back to ancient Babylonians, Chinese, and other civilizations

Significant People:

1. Galileo Galilei

Italian natural Philosopher, astronomer, mathematician

Born: February 15, 1564 in Pisa Italy

Contributions to Astronomy:

1. Sparked the birth of modern Astronomy by:

   1. Observing the Moon and Phases of Venus

   2. Moons around Jupiter and Sunspots

   3. Countless stars make up the Milky Way

2. Made the first telescope by:

   1. Modifying the spyglass that was invented back then and improving it

3. In 1609, Galileo made the first astronomical discovery

Discoveries

1. Galileo made the discovery of 4 moons orbiting Jupiter

2. Galileo also discovered that by looking at Venus, he could deduce that planets orbit the sun, not the earth

3. Galileo discovered the sunspots in the sun which appear as dark in colour

In conclusion, he laid the foundation for today’s modern space probes and telescopes

1. Johannes Kepler

German astronomer, Mathematician, Astrologer, Natural Philosopher and a Music Writer

Born: December 27, 1571 in Weil der Stadt Germany

Contributions to Astronomy:

1. Discovered 3 major laws of planetary motion

2. Made his own telescope

3. Explain the Principles of Telescopes

3 Laws of Planetary Motion:

1st Law: Each planet’s orbit about the Sun is an ellipse

The Sun’s center is always located at one focus of the orbital ellipse. The planet follows the ellipse in its orbit, meaning that the planet to Sun distance is constantly changing as the planet goes around its orbit

2nd Law: The line joining a planet and the Sun sweeps equal areas of space during equal time intervals as the planet orbit.

Basically, that planets do not move with constant speed along their orbit but their speed varies so that the line joining the centers of the Sun and the planet sweeps out equal parts of an area in equal times

3rd Law: The squares of the orbital periods of the planets are directly proportional to the cubes of the semi-major axes of their orbi.

Kepler’s Third Law implies that the period for a planet to orbit the Sun increases rapidly with the radius of its orbit. The earth takes 365 days, while Saturn requires 10,759 days to do the same.

Keplerian Telescope:

1. Improvement of Galileo’s Design

Uses convex lens instead of Galileo’s Concave lens for the eyepiece

Advantage: Rays of light emerging from the eyepiece are converging. This allows for a much wider field of view and greater eye relief, but the image for the viewer is inverted

1. Reach higher magnifications that Galileo’s could

X30 before the image becomes distorted for Galileo

1. Isaac Newton

English physicist and Mathematician

Born December 25, 1642 in Lincolnshire, England

Contributions to Astronomy:

1. He created the modern telescope by improving the current ones through grinding his own lenses and finding a solution.

2. Law of Universal Gravitation

3. Three Laws of Motion

Newton’s Modern Telescope:

Why did Newton build his telescope?

• He thought that it would be able to prove his theory that white light consists of a spectrum of colours via a prism

• Newton wanted a telescope that could get rid of the problem of chromatic aberration

So…

• Changing from using lens to mirror

• Using different types of metals and polishing them

In 1968, he finally made his first telescope

3 Laws of Motion:

1. Balanced Forces

   1. Object would remain at rest or move with constant velocity, unless acted by a net or resultant force

   2. There is still forces that are acting on it, its just that they are balanced

Law of universal gravitation

Statement that any particle of matter in the universe attracts any other particle with a force varying directly as the product of the masses and inversely as the square between them

The magnitude of the attractive force F is equal to G (the gravitational constant, a number the size of which depends on the system of units used and which is a universal constant multiplied by the proud (m|1 and m)

21st Century Advancements

Finding another “Earth” (Kepler-452B)

• Kepler-452b is currently the smallest planet in the habitable zone (the area around the star that could pool water on the orbiting planet)

• Kepler-452b is 60% larger in diameter than earth (Super-Earth-Size)

• While Kepler-452b is larger than earth, it only takes 385 days to orbit 

• Kepler-452b is 6 billion years old

Distant Galaxies and the true nature of Dark Matter

1. Dark matter makes up almost 84% of the mass in the cosmos

2. Dominance throughout the galaxies arises from the fact that the stars and hydrogen gas are moving as if governed by an invisible element

3. Spiral galaxies like our own offers fundamental clues into the nature of the particle at the heart of the mystery of dark matter

What is dark matter and dark energy then?

1. Dark matter is invisible, non-baryonic matter hypothesised to explain phenomena including gravitational lensing and galactic rotation curves

2. Dark energy is thought to permeate the Universe and, despite its low energy-density, is thought to be responsible for the accelerating expansion of the Universe

Astronomers find a potential new breed of a neutron star

About 4,000 light-years from Earth, an entity released a large flash of radiation three times an hour, each for a minute at a time, taking researches by surprise

Magnetars

The most magnetic objects in the universe.

1. Their magnetic fields are a thousand trillion times stronger than earth

2. Like other stars, they emit bursts of radiation.

3. Unlike Pulsars, their bursts are not reliable/consistent. They are pretty erratic

Some of these strange phenomenon can be seen via fast radio bursts. Sudden and intense ones in fact.

But… how are young ones able to produce such a large burst of radiation?

One is an ultra long period magnetars.

Space Missions

NASA Founded by Dwight D Eisenhower

• A journey, by a manned or unmanned vehicle, into space for a specific reason

1. Mercury

Project Mercury was the first human spaceflight program of the United States, running from 1958 through 1963. An early highlight of the Space Race, its goal was to put a man into Earth Orbit and return him safely, ideally before the Soviet Union.

It started when the Soviet Union sent a satellite, Sputnik 1 to space, shocking America, spurring them to start the Project. They successfully sent a satellite to Space, however… The soviets then sent Yuri Gagarin to space, leading America to start…

1. Gemini

Project Gemini was the development of space travel techniques to support the Apollo mission to land astronauts on the Moon. In doing so, it allowed the United States to catch up and overcome the lead in human spaceflight capability the Soviet Union had obtained

They managed to develop on space technology, and also sent two-man spacecraft to Earth-Orbit, setting the groundwork for the next Project. However…

1. Apollo

Project Apollo was the third United States human spaceflight program, which succeeded in preparing and landing the first humans on the Moon from 1968 to 1972

They managed to land two people, Neil Armstrong and Buzz Aldrin, on the moon. Leading to the famous quote: “That’s one small step for man, one giant leap for mankind”

16th February 2022

I felt that today’s lesson was quite boring. As I was the one was in the team that was presenting. I felt that I could have already learnt as much with or without the presentation just through the slides. The presenters were quite hard-to-understand. I understand that the presenters had only less than an hour. But despite it, they still went on with their normal pace. Honestly, the only part that was insightful and interesting was the lens demonstration.

I do think that the lesson could be made much more interesting did the time peruse. I do understand that there were last minute decisions made to make it more compact to get all the necessary points for the presentation. It was an insightful experience with the help of our seniors.

Notes:

Telescopes:

Telescopes-

A telescope is an optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects. They can also be various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.

In other terms, telescopes are bigger magnifying glasses that can also sometimes see heat and other colours on the spectrum you can’t observe normally.

Reflection: Reflection is a lighting feature that makes photons (light particles) bounce off of smooth objects.

Refraction: Refraction is another lighting feature that causes photons to bend going from one medium to another. If you find this slightly more complicated, just dip a pencil in water and look at it.

Light Theory-

• Light can exhibit both a wave theory, and a particle theory at the same time. 

• Much of the time, light behaves like a wave. 

• Light waves are also called electromagnetic waves because they are made up of both electric (E) and magnetic (H) fields. 

• Electromagnetic fields oscillate perpendicular to the direction of wave travel, and perpendicular to each other.

• Light waves are known as transverse waves as they oscillate in the direction traverse to the direction of wave travel.

The Huygens-Fresnel principle:

…states that every point on a wavefront is a source of wavelets. These wavelets spread out in the forward direction, at the same speed as the source wave. The new wavefront is a line tangent to all of the wavelets.

Light:

When light is reflected from a flat and smooth mirror, it bounces off at the same angle in the opposite direction from which it hit. For example, if the light hits a flat or "plane mirror" at a 30-degree angle from the left, it will bounce off at a 30-degree angle to the right.

Light Particles:

Supposedly light particles must always travel in straight lines. If the particles encounter the edge of a barrier, then they will cast a shadow because the particles not blocked by the barrier continue on in a straight line and cannot spread out behind the edge. The results obtained from light diffraction experiments on a much smaller scale do not agree with this. When light is passed through a narrow slit, the beam spreads and becomes wider than expected. So what is the credibility of the wave theory of light?

Converging Lenses

Convex Lens:

A convex lens is a type of lens that funnels and redirects light into one singular area, known as the principal focal point. This mechanic is the reason why you can set innocent insects on fire with a magnifying glass.

Concave Lens:

A concave lens spreads out light directed into it, instead of pointing the light at one single area.

Different Types of Lenses:

-Biconcave Lenses

-Biconvex Lenses

-Plano-Concave Lenses

-Plano-Convex Lenses

-Meniscus Lenses (Lunar Shaped)

-Meniscus Lenses (Squared Lunar Shaped)

How can we apply what we learnt to the function of telescopes?

Types of Telescopes:

Reflector Telescopes:

The reflector telescope uses a mirror to gather and focus light. All celestial objects (including those in our solar system) are so far away that all of the light rays coming from them reach the Earth as parallel rays. Because the light rays are parallel to each other, the reflector telescope's mirror has a parabolic shape. The parabolic-shaped mirror focusses the parallel lights rays to a single point. 

Advantages:

• Reflector telescopes do not suffer from chromatic aberration because all wavelengths will reflect off the mirror in the same way.

• Support for the objective mirror is all along the backside so they can be made very BIG!

• Reflector telescopes are cheaper to make than refractors of the same size.

• Because light is reflecting off the objective, rather than passing through it, only one side of the reflector telescope's objective needs to be perfect.

Disadvantages:

• Because of their size and the design of an open tube assembly, the mirror must be cleaned periodically. Whenever it is cleaned, it must also be realigned, which can be expensive. An improperly aligned telescope results in a blurry or marred image.

• The single reflective surface in a telescope's mirror allows it to be large, but it is also exposed to the air. the metal coating of the reflective surface will oxidise and needs to be replaced after years of service.

Refractor Telescopes

Traits:

• Optical system is more resilient to misalignment than the reflector telescope, 

• rarely needs cleaning, 

• images are sharper and steadier than reflector telescope of same size. 

• All suffer from chromatic aberration

Advantages:

• Superior revolving power per inch of aperture

• Superior performance in inferior conditions - image steadier

• Not reflections or interruption of light path

• Near permanent optical alignment - minimum maintenance

• Long focal ratios can mean use of longer focus, simpler, eyepieces

Disadvantages:

• Very high initial cost relative to reflector

• A certain amount of secondary spectrum (chromatic aberration) unavoidable (reflector completely free of this)

• Long focal ratios can mean that the instrument is cumbersome

Compound Telescopes

Traits:

Compound telescopes are hybrid telescopes that have a mix of refractor and reflector elements in their design. The first compound telescope was made by German astronomer Bernhard Schmidt in 1930.

With its compact construction, compound telescopes can be made more compact compared to the other two types of telescopes. This also provides the advantages of both refractor and reflector telescopes which makes it an excellent all-purpose telescope. 

Advantages:

• Compound telescopes have the advantage of having a long focal length even with their short tubes. This makes these telescopes perfect for observing planets and the moon because of the higher magnification that it can achieve.

• Having a short tube also means that even with big apertures, it still weighs much less than the equivalent of the same aperture of reflector or refractor. It also makes them very portable and very easy to assemble and disassemble for viewing.

Disadvantages:

• Compound telescopes have the problem of not being as good for deep sky objects like galaxies and planetary nebulas because of its high focal ratio and narrower field of view. 

Superachromat:

Like the apochromatic and achromatic lenses, a superachromat corrects aberrations by bringing different colors into focus at the same time. The superachromat is quartic, meaning it disperses four colors simultaneously. These highly fine-tuned lenses are built with expensive fluorite glass to achieve the best type of image correction.

19th January 2022

(Notes were done on Paper, will be scanned and placed here soon)

Today’s lesson went much smoother compared to the last. We first started on with Zhi Xuan( I presume) teaching part two on the satellite lessons namely the Electromagnetic Waves produced. All my notes were written on paper due to my LD running out of battery. We focused a lot on the many different types of EM Waves, from Radio Waves to Gamma Rays. with its frequency and wavelengths taught. Zhi Xuan also taught the Uses ,sources and dangers of these types. Also mentioned were a few questions such as why Electromagnetic Waves Special? Also taught were the special sources, dangers and reasons of Electromagnetic Waves. Sources of Light Pollutions were also taught.

I praise the classroom ICs for their help and swiftness especially for the group tasks. I do would like to hope to see the presentation be slower as we are unable to copy notes which is a requirement for the Exit Ticket of Astronomy. I was lucky to be picked as the group to do the presentation on whether the source of light pollution was true. We managed to finish and do a great job at the presentation, excluding the technological setbacks. This was definitely an insightful lesson, and was interesting to see Secondary 1s looking at our lessons and admiring what they could do as well just as I did last year. Thank you!