All The Epochs

Planck

• Gravity behaves according to quantum mechanics

• temperature is so hot that there is only energy

Grand Unification

• 3 forces left; Weak Nuclear Force; Weak Radioactive Force; ___

Inflationary, Quark, Hadron

• Space became larger by an order of 10^26, over a time of 10^-36 to 10^-32 seconds, cooling the universe by a lot

• Remaining 3 forces took up their present forms

• Too hot for quarks to form hadrons

• When the temperature dropped enough, quarks -> hadrons, Hadron Epoch Started

Photon

• Universe cool enough -> electrons, protons, neutrons formed

• Protons + Neutrons = Nuclei

Recombination Epoch

• Electrons and Nuclei -> Atoms

• Universe transparent to photons

Formation Of Stars

• Universe = transparent, light travel long distances but few light sources

• Universe = only Hydrogen Gas, Background Radiation -> From Big Bang

• Gravity pilled densest regions of Hydrogen gas together yo gotm stars

• Stars were classified as Population III stars -> virtually no metals

• very massive + luminous

Birth Of Galaxes

Matter

• birth of stars accelerated when universe left dark ages

• denser lumps of matter around the universe gave rise to the rapid formation of stars

Galaxy Mergers

• Gravity eventually caused galaxies to merge together, forming larger galaxies

• early large galaxies were spirals but merging caused them to become more eliptical

• galaxies become galaxy clisters

• this process can trigger intensive formation of stars + black holes

Birth Of Planets

• The sun and planets formed from a cloud of gas and dust called a solar nebula

• sun -> center, planets -> thin disk around it

• before sun ignited, planetesimals formed from smallb its of dust and gas clumping together amidst the accretion disk and then collided with each other to form larger plants because of gravity

Cooling Down

• Collision occured, debris rained down on larger objects, lots of heat

• smount of stray debris reduced -> decreasing heat generated

• planets began cooling down from molten rock to what it is today

• thea collided with earth = moon exist

• debris = moon

• originally molten but it crystallised

types of black holes

• stellar

• neutron star absorb enoiugh material from nearby binary star = collapse

• supermassive

• primordial

• black holes can be fofrmed as long as remains of collapsed stars are greater thhan 5 solar masses

• stars must be greater than 20 solar masses for the above to happen

nuclear fusion

• 2 different molecules collide with each other with intense forces to the point where they fuse together

• ^^^ released massive amounts of energy

low mass stars

• <25% solar masses -> collapse white dwarf

• >25% solar masses -> red giant

• trillions of years to run out of fuel

intermediate mass stars

• heavier but not heavy enough for huge explosions

• capable of fusing Helium into heavier elements

• shortens lifespan of these star

white dwarfs

• remains of low & intermediate stars

• very dense and has the mass. of the sun while having the volume of the earth

• when star collapses on itself = remaining mass = compressed into core

high mass stars

• 10 - 70 heavier than sun

• enough to implode and cause massive explosions and formation of other celestial bodies

• can turn into different types of bodies

supernova

• cores are usually obliterated or turns into other things = white dwarfs uncommon

• high mass stars -> alot of nuclear energy to counter its own gravity

• runs out of fuel -> collapse

type 1a supernova

• white dwarf orbiting another star

• the white dwarf accumulates matter from the other star until 'Runaway Nuclear Reaction' ignites

neutron stars

• star collapses on itself -> atoms compressed -> electrons and protons crushed into neutrons

• boom a neutron stars

pulsars

• most common form of neutron star

• emit pulses of strong energy at intervals

• strong magnetic fields which shoots out particles from each poles -> beaem of light

magnetars

• larger + stronger magnetic field

• huge magnetic field = neutron star release a vast amount of energy in the form of electromagnetic radiation (very strong energy)

black hole 2

• star collapses = imaginary surface called "event horizon" forms = light cannot escape from gravity of the Black Hole

• beyond event horizon = ??? (singularity hypothesised to be where it is so dense that space-time starts to curve and the laws of physics starts to break

the end

• hypothetical form of particle decay in which the proton decays into lighter subatomic particles such as positron and pion

• proton decay is hypothetical as it has never been observed to decay

• black holes survive by pulling objects into its event horizon

• when space becomes so vast that therees nothing to pull, nothing happens but if long enough the black hole will become smaller at an increasing rate because of Hawking Radiation

• black hole lights up the universe for the last time (explodes)

end of universe theories

big crunch

• reverses and reforms

big freeze

• universe would hover above absolute zero

• likely to happen

big rip

• universe is torn apart by the expansion of the universe until distance is infinite

reflection

1. what was the most interesting topic youve learnt today

• black hole 2 & supernovas

2. what did you like about the presentation

• the end (part 3/3 not part 4/3 but partially part 4/3 too) & the in a blink of an eye video (the animation was amazing)

Table Of Contents

• Habitability

• Fermi Paradox

• Dark Forest Theory

• Communication

• Seager Equation

• Activity

Habitability

The Basis Of All Life

• In all known forms of life, water & sufficient amounts of certain air qualities are the basis for their existence

• Some important elements include Carbon, Hydrogen, Oxygen & Nitrogen

Habitable Zone (aka 'The Goldilocks Zone')

• It is a region where planets can be at a sufficient temperature that is not too warm or cold

• This allows us to gauge possible planets that contain life

• Earth and Mars

Fermi Paradox

Definition

• Apparent contradiction for the lack of evidence and high probability estimates for the existence of extraterrestrial civilisations

• It was made after a casual conversation between such physicists like Enrico Fermi, etc.

The Great Filter

• An "evolutionary path" in which intelligent life would have to take before discovering us or other colonies of extra-terrestrial origin

1. The right star system

2. Reproductive molecules

3. Simple (prokaryotic) single-cell life

4. Complex (eukaryotic) single-cell life

5. Ability to reproduce

6. Multi-cell life

7. Tool-using animals with intelligence

8. A civilisation advancing toward the potential for a colonisation explosion (Where we are now)

9. Colonisation exploration

Table Of Contents

• 01 - Introduction To Black Holes

• 02 - ???

• 03 - Theories

01 - Introduction To Black Holes

What is a black hole?

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong...

Can we see black holes?

• We cant since its strong gravity pulls all the surrounding light to the center of the black hole. 

• However, astronomers observe the presence of a black hole by its effect on its surroundings.

• Scientists can observe how the strong gravity affects the stars and gas around the black hole.

How big and heavy are black holes?

• It can vary greatly. The smallest black holes can be as small as one atom, yet they have a mass of a large mountain.

• The large black holes can be as big as a few million Earths combined, and they have a mass equal to around 4 million Suns.

What types of black holes are there?

• There are 4 types: stellar-mass, intermediate, supermassive and miniature.

  • Stellar-mass: they are the most common black holes, ranging from five to tens of times the mass of the Sun.

  • Intermediate: Significantly more massive than a stellar black hole. However, it has less mass than a supermassive one. Intermediate black holes range from 100 to a million times more massive than the Sun.

  • Supermassive: Largest type of black holes, ranging from millions to billions of times the mass of our Sun. Every galaxy has a supermassive black hole at its center.

  • Miniature: Hypothetical tiny black holes. The size of these black holes may be equal to or above 22.1 micrograms, which is about one millionth of a gram.

How are black holes created?

• Stellar-mass: When the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.

• Intermediate: It is too massive to be formed by the collapse of a single star. One theory as to how intermediate black holes are formed is that stellar black holes gravitationally attract other stellar black holes or compact objects. The merging of these black holes and compact objects from an intermediate black hole. 

• Supermassive: The formation of supermassive black holes are still unconfirmed. Some have suggested that supermassive black holes form out of the collapse of massive clouds of gas during the early stages of the formation of the galaxy.

• Miniature: A black hole formed soon after the creation of the universe is called a primordial black hole and is the most widely accepted hypothesis for the possible creation of micro black hole.

How to photograph Black Holes

1) Event Horizon Telescope: Capture an image of a black hole. The degree of precision makes the EHT capable of resolving objects about 4000 times better than the Hubble Space Telescope.

2) Very Long Baseline Interferometry: Creating an array of smaller telescopes that can be synchronised to focus on the same object at the same times and act as a giant virtual telescope.

The Singularity and Event Horizon

• Event Horizon: Infamously known as the "point of no return". Once matter is inside it, that matter will fall to the center. With such strong gravity, the matter squishes to just a point - a tiny, tiny volume with a crazy-big density.

• Singularity: That is the point. It is vanishingly small, so it has essentially an infinite density; which makes it likely that the laws of physics break down at the singularity. 

Spaghettification

The singularity is found at the centre of a black hole, and it exerts a strong gravitational force for any object that falls in. This process is known as spaghettification.

03 - Theories

White holes

• The polar opposites to black holes

• Also contain a singularity, but they operative in reverse to a black hole: Nothing can enter the event horizon of a white hole, and any material inside the white hole gets ejected immediately.

Wormholes

01 - How are white and black holes connected?

• Because the two holes would exist in separate places in space, a tunnel – a wormhole – would bridge the two ends.

02 - What is a wormhole exactly?

• Describes Einstein's theory of general relativity that connects two distant point in space or time via a tunnel.

However, wormholes would not be very useful

1) Super unstable. If a particle dropped towards the event horizon of a white hole, it would never reach since nothing can enter a white hole -> energy of system increases to infinity and white hole explodes.

2) The only way to enter this kind of wormhole would be to cross the event horizon of the black hole on the other side. But once an object crossed the event horizon, it could never leave. So objects could enter the wormhole but never escape.

How would hypothetical wormholes look like?

• The entrance would be a sphere, like the surface of a planet. If you looked into it, you would see light coming from the other side. The wormhole tunnel could be any length, and while you are travelling down the tunnel, you would see distorted views of the region if the universe you came from and the region you were travelling to.

Wormholes and time travel

• A wormhole could also act as a time machine. Special relativity dictates that moving clocks run slowly. In other words, someone racing around at nearly the speed of light would not advance into their own future as quickly as someone standing still.

• If scientists could somehow construct a wormhole, initially the two ends would be synchronised in time. But if one end were then accelerated to nearly the speed of light, that end would start to lag behind the other end. The two entrances could then be brought together, but then one of the entrances would be in the past of the other.

Hawking Radiation

Glossary:

• Quantum Fluctuations - The temporary random change in the amount of energy in a point in space.

• Annihilation - The conversion of matter into energy, especially the mutual conversion of a particle and an antiparticle into electromagnetic radiation.

• Eons - A unit of time equal to a thousand million years.

Evaporating black holes

• It is the thermal radiation predicted to be spontaneously emitted by black holes. It arises from the steady conversion of quantum vacuum fluctuations into pairs of particles, one of which escaping at infinity while the other is trapped inside the black hole horizon.

Exoplanets

Table Of Contents

• What Are Exoplanets?

• Examples Of Exoplanets

• History Of Exoplanets

• aa

• aa

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What are Exoplanets?

Exoplanets refer to planets outside our solar system. They orbit around their own stars, forming their own solar system. Most orbit other stars, but there are free-floating exoplanets, called rogue planets, orbit the galactic center and are untethered to any star.

Examples of Exoplanets

Goldilock's Zone

 The habitable zone is the area around a star where it is not too hot and not too cold for liquid water to exist on the surface of surrounding planets. The temperature of the habitable zone is "just right" for liquid water to exist.

Exoplanets

• Kepler 186f: Kepler-186f was the first rocky planet to be found within the Goldilock's zone. This planet is also very close in size to Earth.

• HD 209458b ("Osiris"): The first planet to be seen in transit and the first planet to have its light directly detected.....

• 51 Pegasi b: This giant exoplanet is about half the mass of Jupiter and orbits its star every 4 days. it was the first confirmed exoplanet around a sun-like star, a discovery that launched a whole new field of exploration

• Kepler-444 System: The oldest known planetary system has five terrestrial-sized planets, all in orbital resonance. This weird group showed that solar systems have formed and lived in our galaxy for nearly its entire existence.

Other Notable Exoplanets

• Kepler-22b: Possible water-world planet unlike any seen in our solar system.

• Kepler-69c

• Kepler-452b: The first Earth-sized planet found in the habitable zone of a sun-like star.

History Of Exoplanets

Carl Sagan

Carl Edward Sagan was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. His best known scientific contribution is research on extraterrestrial life.

The First Exoplanet

After much of Carl Sagan's theory, in 1992, astronomers discovered the first exoplanet, or planet outside our solar system. But it didn't come in any form they'd really anticipated. It was found by detecting pulsars.

How To Detect Exoplanets

• Doppler Spectroscopy

• Centre of gravity: In space, two or more objects orbiting each other also have a center of mass. It is the point around which the objects orbit. This point is the barycenter of the objects. The barycenter is usually closest to the object with the most mass.

How To Apply

As the exoplanets orbit around a star, the barycentre of a sun is important. If a star has planets, the star orbits around a barycenter that is not at its very center. This causes the star to look like it's wobbling. This is how we detect exoplanets. Since the mass of a star is mostly significantly larger than that of the planet, the centre of mass of the system usually lies within the star, causing the orbit to manifest as a "wobble" in the star.

Transits

• Transit-timing variation: Transit-timing variation is a method for detecting exoplanets by observing variations in the timing of a transit. The provides an extremely sensitive method capable of detecting...

• Pulsar timing: Pulsar are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds. Pulsars have very strong magnetic fields which funnel jets of particles out along the two magnetic poles. These accelerated particles produce very powerful beams of light. By tracking the motion of pulsars, the orbit parameters can be determined and exoplanets can be detected. However, pulsars are relatively rare, and planets orbiting these pulsars are even rarer, limiting the usefulness of this technique.

• Direct imaging: Imagine taking a picture with your camera. You see what is before you, and nothing else. Now, imagine taking a picture with a camera that can include frequencies of light beyond the visible spectrum. Limitations: The parent star is usually much brighter than the planet, so light will most likely be blocked by them. Planets found through direct imaging are usually around brown dwarfs, which are relatively dim and not much light detected.

• Gravitational microlensing: This technique is premised in general relativity, where the light from a star can be bent by the gravity of an object between the earth and the source star. The object acts as a lens, where the gravity from the planet will cause further bending or distortion of the light, and such variations in the can be detected. Limitations: However, this technique relies on a chance alignment between the source star, the lens star, and the observer, and that is not that common.

• Astrometry: Astrometry involves measuring a star's position in the sky accurately, and detecting how that position changes over time. Since a star with a planet will orbit around the common barycentre of the system, the star's position in the sky can be used to detect signs of this orbit.

Table Of Contents

• basic knowledge

• construction

• control

• some physics lessons along the way

• getting into orbit

• landing back onto earthControls

Spacebar -> stage

F5 -> quicksave

F9 -> load quicksave

arrow keys -> change viewing angle

Lshift -> increase throttle

Lctrl -> decrease throttle

caplock -> fine control

C -> change view

Lecture Continuation

Single Stage to Orbit (SSTO): 1 Stage Plane Rocket, from ground to orbit.

Rovers: Help Kerbals to move around, robots can go to more places to collect data. They are small, complex and very useful.

Satellites

• Satellites: refer to an object orbiting a planet.

• Intentional Artificial Satellites: These can be either for commercial or militaristic purposes. 

  • Commercial Uses: Planetary observation, Communication, Navigation, etc.

  • Planetary Observation (Earth): Environmental monitoring, meteorology, cartography

Communication

• Relays information across curvature of earth through radio signals. Multiple satellites work together as transponders. 

  • Passive: Only reflect the signal. Does not amplify so signal received is very weak

  • Active: Amplifies signal. More common nowadays.

Antennas

• Used to send and receive signals continuously

• Applies to satellites orbiting other planets

• Eg: Elon Musk using Starlink to provide internet to people in Ukraine

Navigation

• Provide autonomous geo-spatial data and super accurate time synchronisation. positioning, navigation, timing (pnt)

• Common global navigation satellite systems (GNSS): GPS (USA), GLONASS (RU), BeiDou (CN), Galilei (EU)

Telescopes

• Observe distant astronomical objects. Better because it avoids light pollution and other distortions thabt ground telescopes face. 

  • Astronomical survey: Maps whole sky

  • Focused survey: Focuses on certain objects and parts of sky

Space Station and Crafts

• Support human crew for extended period of time. For scientific purposes such as to study the effects of spaceflight on the human body, as well as to provide a location to conduct a greater number and longer length of scientific studies than is possible on other space vehicles. Power Source is solar.

Famous Satellites

• ISS: Modular space station in low earth orbit, multinational collaborative project involving five participating space agencies: NASA (USA), Roscosmos (RU), JAXA (JP), ESA (EU), CSA (CAD). Meant to be a laboratory, observatory and factory while providing transportation, maintenance. However, not all of the uses have been realised.

• New Horizons: NASA mission to study Pluto, its moons and other objects in the Kuiper Belt (1st spacecraft to encounter Pluto, carries a cylindrical radioisotope thermoelectric generator (From Cassini Mission) that gave 250W at launch.

• Sputnik 1: Elliptical low earth orbit, Soviet Union, 4/10/1957, Soviet Space Program, orbited for 3 weeks before batteries ran out, 4 external radio antennas to broadcast radio pulses.

• Soil Moisture Active Passive (SMAP): NASA Env Monitoring Satellite on 31/1/2015. Detects soil moisture which provides invaluable info around the globe.

• Cassini-Huygens: NASA & ESA & ASI, Space Probe. To study Saturn & its System, Determining the 3D and behaviour of rings of Saturn, Composition of satellite surfaces & Geological history or each object, Characterise Titan's surface on a regional scale.

Launch, Trajectory, Disposal

• Trajectory

• The Satellites cannot ravel in a straight line to target planet. They use gravity from another planet like Venus or the Sun like a "slingshot" to move towards the target planet.

• Disposal

• Earth Satellites

  • • Low Earth Orbit (LEO): Burning the satellite in the earth's atmosphere

    • High Earth Orbit (HEO): Graveyard orbit. (Raising the orbit of satellite to be far away from any other ongoing missions and won't be a danger.

  • External Earth Satellites

    • Deorbiting: Similar to graveyard orbit

    • Controlled entry: Launch the satellite to the atmosphere of the planet for them to burn up, like in HEO for earth satellites.

Constellations

Table Of Contents

• 01 - What Are Constellations?

• 02 - What Are Asterisms?

• 03 - Examples of constellations + storytime

• 04 - Quick demo on stellarium

01 - What are constellations?

• Constellations are groups of stars. They depend on your location and time of year. They are named after objects, animals, and people long ago. Astronomers today still use constellations to name stars and meteor showers.

• NGC - New General Catalogue. The catalogue refers to an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. 

• M - Messier. A set of 110 astronomical objects catalogued by the French astronomer Charles Messier. They are a collection of deep sky objects, such as galaxies, nebulae, and star clusters.

• They helped stargazers and astronomers:

  • Specific stars in the night sky

  • Create and track the calendar (ancient)

  • Navigation

  • Difference in colours

  • Group stars

02 - Constellations vs Asterisms

Asterisms: Patterns of varying stars

• Winter Triangle: Contains Sirius, Betelgeuse, Procyon, Canis Major, Orion, Canis Minor. Prominent asterism in the N Hemisphere from December to March.

03 - Examples of constellations + storytime

Ursa Major: All stars are of equal magnitude, larger area

Ursa Minor: Only 3 bright stars, small area

1. How can I apply this in my daily life?

2. How can this lesson be improved?

3. What would you like to see in the future?

Stellar Evolution (1/2)

• Protostars

  • Molecular Clouds: Size & density contribute to regular molecular formation, mostly Hydrogen. It helps differentiate from other interstellar clouds. An example is the Taurus Molecular Cloud (Nearest large star formation).

  • Protostars: The birth of a star which lasts for ~500k years. Starts out as small clumps of gas (Dense cores). After it collapses, it forms a low mass protostar with a protoplanetary disk orbiting it. Gas accumulates at the disk and forms an equilibrium. An example is HOPS 383 (Outburst).

• Main Sequence

  • Main Sequence Stars: A fully mature star which has homogeneous initial composition (~70% Hydrogen, ~28% Helium, ~2% Others). Does nuclear fusion (Hydrogen + Helium). Classified by nuclear fusion rate to determine their colour & brightness.

    • G-Type Stars: Called yellow dwarves and has surface temperature of 5.3k- 6k Kelvin. Outshines over 90% of the galaxy, often has a lifespan of 10B years. Example is our Sun (Halfway stage).

    • Brown Dwarf: Called a dead star, happens because of insufficient hydrogen mass.

• Old & Death

  • Red Giants: When a main sequence star runs out of Hydrogen and contracts due to gravity. Nuclear fusion continues due to addition of Hydrogen. Thermal pressure and gravity fights till the star stops expanding. Temperature ranges from 3K to 4K Kelvin and has 3x the brightness.

  • Planetary Nebula: Emission shell of ionised gas, signified as the end of a typical star's life cycle. It is a short-lived phenomenon. An example is the Dumbbell nebula.

  • White Dwarf: Degenerate star. No longer has a core. Made out of a plasma with unbound nuclei and electrons. Compression of the electrons increases the kinetic energy of the electrons and is only dependant on density.

  • Black Dwarf: Theoretical stellar remnant. If it does exist, it would be very hard to detect as it emits very little radiation.

Lecture Stellar Evolution (2/2)

Supernovas

• Details: A phenomenon when a star reaches the end of its lifespan and explode.

• Caused By: The burning process will continuously burn till hydrogen can no longer be fused. Gravity tips over its thermal pressure and causes a core collapse.

• Discovery & Observation: First documented supernova was by Walter Baade. It was observed that stars can be observed that glow up in a burst of energy, then disappear altogether or leave a smaller star than it was before.

• Type 1a Supernova: Sun (Star) -> Red Giant -> White Dwarf -> If >1.4 ☉ = Type 1a Supernova

• Type II Supernova -> Star (>8☉) -> Red Giant OR Blue Compact Star -> If >8 ☉ = Type II Supernova (SN1993J)

Neutron Stars

• Details: A neutron is a collapsed core of a massive star. It is so compact that its density is equivalent to Mount Everest in a cup of coffee. Currently there are known to be ~2000 Neutron Stars in the Milky Way and Magellanic Clouds.

• Discovery: Some of the first ideas of the neutron star were discovered by Walter Baade and Fritz Zwiicky. The first official Neutron Star was discovered by Jocelyn Bell.

Black Holes

• Details: A collapsed core of a massive star that has enough gravity that makes anything inescapable. Black holes are known to be invisible. However, we have observational evidence of Black Holes.

• Discovery: On 10 April 2019, the first image of a black hole was published.

Relativity

Chapter 1 - General and Special Relativity

[Check Previous Lectures]

Chapter 2 - Special Relativity

Chapter 3 - General Relativity

If light’s speed is constant, then even though length AB > CD, light travelling on line CD will have the same speed as the light travelling on AB. Recall the distance speed and time 🜂. That means that light travelling on CD has more distance, but uses less time, thus time dilation.

Chapter 3.5 - Exceptions to GR

GR is unable to work in the centre of black holes. The standard model of quantum physics are so far incompatible with GR & SR, as spacetime needs to be measured with absolute precision.

Chapter 4 - Twin Paradox & Thought Experiments

Imagine that there are two sisters, who are identical twins, when they are 20 years old, one is sent on a mission in space where the rocket will be travelling at v = 0.995c to visit a nearby star while the other twin stays behind on Earth. When the twin returns from space, she will be 22 years old while the twin who stayed behind will be 40 years old due to time dilation.

Imagine that you are in an empty, windowless room that is drifting in space. Suddenly you fall to the floor and is stuck. 1) you are approaching an object that exerts gravitational force, and it is pulling it towards you, or 2) you are being pulled by an accelerating force like a spaceship. Thus, this experiment demonstrates how Einstein combined the two problems of making GR, gravity and acceleration, by making a connection between these forces: An observer cannot tell if they are accelerating due to gravity or another force.

Deep Sky Objects

Deep Sky Objects Catalogue

• NGC - New General Catalogue. The catalogue refers to an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. 

• M - Messier. A set of 110 astronomical objects catalogued by the French astronomer Charles Messier. They are a collection of deep sky objects, such as galaxies, nebulae, and star clusters.

Nebulae

• Emission Nebula: Clouds of ionised gas and emit their own light at optical wavelengths. Mass ranges from 100 - 10000 M☉, spread over a volume of <1 - 300 light years.

• Planetary Nebula: The energy causes the expelled gas from red giants to ionise, meaning that the atoms and molecules in the gas become charged and begin to emit light. The cast-off glowing gas is known as a planetary nebula.

• Supernova Remnants: Structure resulted from the explosion of a star in a supernova. It is bounded by an expanding shockwave and consists of ejected material expanding from the explosion and interstellar material.

Galaxies

• Spiral galaxies: Have central bulge surrounded by a flat, rotating disk of stars which contains older, dimmer stars and is thought to contain a supermassive black hole. The disk of stars orbiting the bulge separates into arms that circle the galaxy and contain gas and dust and younger stars that shine brightly before their quick demise.

• Elliptical galaxies: They are very old and stars inside are among the oldest in the universe and do not create new stars. They hold tightly to ancient stars that have lived for billions of years. Each of them contain a supermassive black hole.

• Irregular galaxies

  • Type I: Usually single galaxies of peculiar appearance. They contain a large fraction of young stars and show the luminous nebulae.

  • Type II: It appears the way it does because of it interacting of merging with another galaxy.

Star Maps

• Stars: Black dots on a white background. Size of dot is brightness of star.

• Night Sky Coordinates: The reference frames used on star charts; right ascension and declination, are equivalent to the ones used on Earth.

• Observing: On a sky map, the sky is observed as a dome around the Earth. As night progresses, the dome turns so that stars seem to rise in the east and set in the west. The point directly overhead is called the Zenith and the edge is called the Horizon.

refer to physical

i learnt about the types of telescopes used for stargazing and was introduced to activites/competitions in astronomy club

1. How can I apply this in my daily life?

•  Maybe debunk myths about extraterrestrial life

2. How can this lesson be improved?

•  More in-depth explanations 

3. What would you like to see in the future?

• Quizzes at the end of CCA and more hands-on activities

1. How can I apply this in my daily life?

• I can tell my friends about black holes accurately if they want to know about black holes

2. How can this lesson be improved?

• More images instead of words because images can be understood quicker and better

3. What would you like to see in the future?

• not boring lectures (eg. interesting activities like using telescopes)

1. How can I apply this in my daily life?

• If i ever become a physicist, i can use direct imaging to map out exoplanets for some reason

2. How can this lesson be improved?

• easier kahoots

3. What would you like to see in the future?

• exoplanets in the sky

• i learnt how to orbit and de-orbit 

• ksp controls n stuff

I learnt about what asterisms are. I can now recognise what constellation i took picture of (orion).

I learnt about what astronomical discoveries (pun not intended) were made in the 21st century and what to expect in the future. I felt that the lesson was normal and a little boring. Activities with quizzes that don't have a lot of errors.

I learnt what astronauts eat and what food cannot go up in space. Potatoes are good except that they lack fiber and vitamin D. 

I learnt the aerodynamic forces like drag forces and lift forces and there are pressure drag and friction drag. Pressure drag is caused by lower pressure behind the object and higher pressure in front of the object. Friction drag is caused by air flow along the surface area of the object. A blunt object has low friction drag but high pressure drag. 

I learnt that black dwarfs are invisible and emits very little radiation. Protostars events last for 500k years and form a protoplanetary disk. Yellow dwarves actually outshine 90% of their galaxy. Red giants still can perform nuclear fusion somehow. This lesson can be improved by having hand-on activities.

I learned that 1.4 solar masses is needed for a star to become a type 1a supernova and 8 solar masses or higher is needed for a star to become a type II supernova. After the supernova, the leftover is a remnant. A neutron is as dense as mount everest in a cup of coffee. It was discovered by Jocelyn Bell. The first image of a black hole was published on 10/4/2019 and light can be bent by them allowing us to see some parts behind the black hole and are known to be invisible. The lesson can be improved by having hands-on activities.

I learnt about how to read a star map and the components in it, types of nebulae and galaxies. I also identified the stars in an image with a stellarium. I learnt about GN-z11 in my group's slide research. Improve: Having hands-on activities out of classroom.

I am ok with teaching others but prefer not to and my voice is soft i think. I can improve by increasing my volume when presenting. i would like this lesson to be repeated.

Mr Tan introduced 2 programmes, bottle rocket program and dome program for Sec 1 - 3, overseas trip for Sec 2 - 3, astronomy competitions and fox hunting radio. Idk how lesson can be improved.

21/2/2024

astronomy. utilise a lot of formulas just like physics eg. orbit formula something

W3: We did circular trigonometry but it was kinda confusing and couldn’t really understand

i learnt about the binary star systems and the doppler and the unique ones and it was also quite fun since there was blooket and i won ig

ksp and rocket kept crashing, the astro exploration thing is kind of boring since we did it before and my calculator stolen

the total dipole length is 3.22758621 feet while length of each dipole is 1.6137931 feet for the antenna (frequency is 145 MHz)

there isnt much to reflect since we have done it in the past but its cool to learn about possible extraterrestrial life out of Earth

this guy participated in astrochallenge and they did a poster and like were not prepared to face the questions posed by the judges and also did a group exam. and then after that we learned some orbital mechanics about how the hofmann transfer thing works change orbits trajectory

i learned about the oort cloud and disk accretion and angular momentum conservation where momentum of the roating object doesnt change until external torque is applied

there are like weird laws and stuff too complicated for me

solar system and nilky way are accretions too

roche limits has a weird formula and gravitational stuff

kahoot too

apply the stuff maybe in competitions

i learnt about planets and their characteristics in the solar system like jupiter storms and stuff

also there is a china / HK trip announced by mr tan

i enjoyed ksp

what can be improved is the abolition of lectures

i want learn about / i would look forward to the good ol' water rockets

I learnt that main sequence stars luminosity increases at like a constant rate when the temperature increases. Giants usually cluster around the low temperature but high luminosity, supergiants are across the spectrum and high luminosity. Red giants still can perform nuclear fusion somehow. This lesson can be improved by having hand-on activities.

26/2/2025

a scientist from NASA came over to the auditorium and gave us a very nice presentation how solar flares and the effects of them

CMEs and flares are different, they look similar but are different

CMEs can damage the Earth's infrastructure by interferring with essential communications such as satellites and avionics

I learnt about telescopes and their features and got to create and design a telescope on tinkercad

what has 2 heads and a long body, that everyone in this school needs?