Astronomy

What are the planets of our solar system in order from the sun outwards?

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

What are the planets relative sizes

Mercury = 4,880km (3,032mi), Venus = 12,104km (7,521mi), Earth = 12,742m (7,918mi), Mars = 6,779km (4,212mi), Jupiter = 142,984km *88,846mi), Saturn = 120,536km (74,898mi), Uranus = 51,118km (31,763mi), Neptune = 49,528km (30,775)

What is the relative size of our Sun compared to the planets?

Suns’s Size = 1,391,000 km (864,000mi)

Mercury - Sun = 285x Wider, Venus - Sun = 115x Wider, Earth - Sun = 109x, Mars - Sun = 205x Wider, Jupiter - Sun = 10x Wider, Saturn Sun = 12x Wider, Uranus - Sun = 27x Wider, Neptune - Sun = 28x Wider

What makes each planet unique? What is at least one unique feature of each planet?

Each planet has unique characteristics including size, composition, atmospheric conditions, surface features, and orbital characteristics.

Mercury - Smallest and closest to the Sun, Mercury has a heavily cratered surface and extreme temperature variations.

Venus - Known for its extremely dense, toxic atmosphere and scorching surface temperatures. It has similar size and gravity to earth.

Earth - The only planet able to support life

Mars - Known for it reddish appearance due to iron oxide (rust) on its surface. It has polar ice caps, evidence of past liquid water, and seasons like earth.

Jupiter - The largest planet, Jupiter is a gas giant with prominent red spot, a massive storm. It has a faint ring system and numerous moons.

Saturn - Famous for its prominent ring system. Saturn is another gas giant known for its low density.

Uranus - This ice giant is unique for its extreme axial tilt, causing it to rotate on its side. It also has a faint ring system and a unique blue-green color due to methane in its atmosphere.

Neptune - The farthest planet from the Sun, Neptune is also an ice giant with strong winds and a dark spot similar to Jupiter’s.

Approximately how fast does light travel?  (relatively speaking i.e. how long does light take to get to our eyes from the Sun?)

• Light travels at approximately 300,000 kilometres per second

• Light takes approximately 8 minutes and 20 seconds to travel from the sun to our eyes

Approximately how large is the Milky Way galaxy? Approximately how many stars does it contain?

• The milky way galaxy is approximately 100,000 light-years in diameter.

• The galaxy contains approximately 100 billion stars

Approximately how far away are other galaxies?

Galaxies are far apart with the nearest ones being millions of light-years away

What is cosmic background radiation and how does it relate to the big bang

The cosmic microwave background (CMB) is the afterglow of the Big Band, the faint heat that remains from the universe’s formation, it’s the oldest light we can see.

How do we know the Universe is expanding? What is “red-shift”

The Universe is known to be expanding through observation of redshift, which is a phenomenon where the light from distant galaxies appears shifted towards the red end of the spectrum. The stretching of light wavelengths indicates that galaxies are moving away from us.

What are spectral lines? What do they represent?

A Spectral line is a distinct band of colour, either brighter or darker, within a continuous spectrum of light. They represent the unique fingerprint of an element, arising from the interaction f light with atoms or molecules.

How can we determine where stars are made of?

Stars compositions are determined through a technique called spectroscopy, which analyzes the light emitted or absorbed by celestial objects. By examining the unique patterns of light and dark lines in a stars spectrum, astronomers can identify the elements present and their relative abundances.

Approximately how old is the universe?

The universe is roughly 13.8 billion years old based on measurements of ages of the oldest stars and the rate at which the universe expands

Why is the beginning of the Universe called “The Big Bang”?

The beginning of the universe is called the Big Band because it is believed to have started from a very hot, dense state and then rapidly expanded, much like an explosion

Why is the Big Bang a misnomer

The Big Band is considered a misnomer because it suggests a literal explosion, which is not what the theory describes. Instead, the Big Band refers to the rapid expansion of space itself from an extremely hot, dense state.

Where is the centre of the universe

There is no centre of the universe. The universe is expanding, and this expansion is happening uniformly everywhere, meaning there’s no central point from which everything is expanding

Approximately, how many stars are in the observable universe?

There are estimated 200 billion trillion stars in the observable universe.

Describe the life cycle of a Sun-like star

A Sun-like star’s life cycle begins with a nebula, forms, a pro-star, then enters the main sequence phase, followed becoming a red giant, and ultimately shedding its outer layers to become a white dwarf, which eventually cools into a black dwarf.

Describe the life cycle of a massive star

A massive star’s life cycle, starting from a nebula, involves stages of protostar, main sequence, a red giant, and culminates, in a supernova. The core of a massive star collapses into either a neutron star or a black hole, depending on the core’s remaining mass

Why is a black hole black?

A black hole appears black because its immense gravity prevents any light or other electromagnetic radiation from escaping, making it essentially invisible to observers

What is a neutron star?

A neutron star is the dense remnant of a massive star that has exploded in a supernova. After the explosion, if the star’s core is between 1.4 and ~3 times the mass of the Sun, gravity crushes it into a ball of neutrons. These stars are incredibly dense—one sugar-cube-sized amount would weigh a billion tons on Earth. They often spin rapidly and emit beams of radiation, becoming pulsars if the beam crosses our line of sight.

What is the name of the boundary of a black hole from which light cannot escape

It is called the event horizon. This is the “point of no return”; once any matter or light crosses this boundary, it cannot escape the black hole’s gravity. Beyond this, not even light can travel fast enough to break free.

What is wavelength

Wavelength is the distance between two identical points on consecutive waves (like crest to crest). It is usually measured in meters or nanometers, and it determines properties like color (in light) or pitch (in sound).

What is the relationship between wavelength and energy of light?

Shorter wavelengths have higher energy, and longer wavelengths have lower energy. This is an inverse relationship. For example, gamma rays have very short wavelengths and are extremely energetic, while radio waves are long and low in energy.

What types of radiation do stars give off?

Stars emit electromagnetic radiation across the spectrum, mainly:

• Visible light

• Ultraviolet (UV)

• Infrared (IR)

• Some emit X-rays and radio waves
  The Sun, for example, emits mostly visible light but also UV and IR.

What are all the different types of light in the EM spectrum and how are they ordered?

From lowest to highest energy:

1. Radio waves – longest wavelength

2. Microwaves

3. Infrared (IR)

4. Visible light – red to violet

5. Ultraviolet (UV)

6. X-rays

7. Gamma rays – shortest wavelength, highest energy

What is a continuous spectrum?

A continuous spectrum shows all the colors (wavelengths) of visible light without gaps, like a rainbow. It is produced by hot, dense objects such as stars, glowing metal, or incandescent bulbs.

How is the color of a star related to its temperature?

Color tells us temperature:

• Blue stars are the hottest (over 10,000 K)

• White stars are also very hot

• Yellow stars like our Sun are medium temperature (~5,800 K)

• Red stars are cooler (below 3,500 K)

This is due to blackbody radiation—hotter objects emit more energy at shorter (bluer) wavelengths.

What is a lunar eclipse? What is a solar eclipse?

• Lunar eclipse: Earth blocks sunlight from reaching the Moon. Happens when the Earth is between the Sun and the Moon. The Moon often turns reddish (a “blood moon”).

• Solar eclipse: The Moon blocks sunlight from reaching Earth. Happens when the Moon is between the Earth and the Sun, casting a shadow on Earth.

Describe the shape of Earth’s orbit around the Sun

Earth’s orbit is an ellipse (oval shape), but it’s nearly circular. The Sun is located at one of the two foci of the ellipse.

What is the reason for the seasons?

The tilt of Earth’s axis (23.5°) causes the seasons. As Earth orbits the Sun, different parts of the Earth receive more direct sunlight. When the Northern Hemisphere is tilted toward the Sun, it’s summer there.

How long does it take for Earth to orbit the Sun?

Approximately 365.25 days, or 1 year. The extra 0.25 days is why we have leap years every 4 years.

How did people in the past know Earth orbits the Sun?

• Retrograde motion of planets: best explained by a Sun-centered (heliocentric) model.

• Phases of Venus (observed by Galileo): only possible if Venus orbits the Sun.

• Stellar parallax (later observed): nearby stars shift position relative to background stars due to Earth’s orbit.

How did people know Earth is a sphere?

• Ships disappearing hull-first over the horizon

• Lunar eclipses: Earth’s shadow is round

• Different stars visible from different latitudes

• Eratosthenes' experiment: measured Earth’s circumference using shadows

How did people know Earth rotates?

• Foucault pendulum: proves Earth rotates beneath the swinging pendulum

• Coriolis effect: affects weather and ocean currents

• Day-night cycle: best explained by rotation

What is parallax and how is it related to a parsec?

Parallax is the apparent shift of an object when viewed from two positions. Astronomers measure how much nearby stars move against background stars over 6 months.
A parsec is the distance at which a star has a parallax angle of 1 arcsecond. 1 parsec ≈ 3.26 light-years.

What is an arcsecond?

An arcsecond is a tiny angle: 1/3600 of a degree. Used to measure very small angles in astronomy, like star positions and parallax.

What is the Fermi Paradox? What are some solutions?

The Fermi Paradox asks: “If the universe is so big and old, where is everyone?” (Why haven’t we found alien life?)

• We’re alone (life is extremely rare)

• Aliens are avoiding us

• We’re not listening properly

• Civilizations self-destruct
  One detailed solution: The Great Filter—something extremely hard (like the jump to intelligent life or avoiding extinction) prevents civilizations from becoming spacefaring.

If the Sun were the size of a red blood cell, how big would the Milky Way be?

• A red blood cell is about 6 micrometers.

• If the Sun were this small, the Milky Way would be the size of North America, roughly 5,000 km (3,100 miles) across.

If the Sun were the size of a marble (~1 cm), how big would the Milky Way be?

• A marble is about 1 cm wide.

• At this scale, the Milky Way would be about 100,000 km wide—about 2.5 times the circumference of the Earth, or roughly the size of planet Earth itself.