Astronomy: Celestial Characteristics and Objects

• Astronomy studies celestial objects outside Earth's atmosphere.
• The universe encompasses everything that exists.

Galaxies

• A galaxy is a vast, rotating mass of gas, dust, stars, planets, and celestial objects.

Celestial Characteristics

• Rotation: A celestial body's spin on its axis, taking Earth 24 hours.
• Revolution: The orbit of one object around another, such as Earth's 365.24-day revolution around the sun.

Stars

• Stars are masses of plasma and gases, held together by their gravity and emitting energy.
• The Sun is an average star among the Milky Way's billions.

Planets

• Planets are spherical objects orbiting stars.
• To be a planet, it must orbit a star, be spherical due to its gravity, and have cleared its orbit of similar objects.
• Objects failing these criteria are dwarf planets like Pluto, Eris, Ceres, Haumea, and Makemake.

Moons

• Moons are celestial objects orbiting planets or dwarf planets.
• Earth has one natural satellite, the Moon.

Asteroids

• Asteroids are variable-sized chunks of rock.

Comets

• Comets consist of dust and ice.
• When passing the sun, solar heat causes comets to form a tail of ice particles.

Meteroids

• Meteroids are small rocks and metal with no path.
• Meteors enter Earth's atmosphere.
• Meteorites survive atmospheric entry and land on Earth.

The Sun

• The Sun is a star composed of hydrogen and helium gas.
• Nuclear fusion converts hydrogen to helium, releasing energy.

The Sun's Six Layers

• Core: 15,000,000°C with high pressure, where nuclear fusion occurs.
• Radiative Zone: Dense plasma, 2 to 7 million °C, light takes ~100,000 years to pass through due to absorption and re-emission.
• Convective Zone: 6,000 to 2 million °C, hot plasma rises, cools, and sinks, creating convection.
• Photosphere: 5,500°C, contains 4,000°C sunspots caused by magnetic field disturbances.
• Chromosphere: 6,000 to 50,000°C, generates solar flares of charged particles.
• Corona: 1 million °C, a very hot, thin layer visible during solar eclipses, extending millions of kilometers into space.

The Sun's Surface

• Sunspots are cooler, darker areas.
• Solar prominences are slow gas eruptions.
• Solar flares are explosive events of gas and plasma on sunspots.

Solar Winds

• Solar winds are constant streams of particles from the sun.
• Solar winds create the aurora borealis (Northern Lights) and aurora australis (Southern Lights).
• Solar wind particles create a glow near Earth's poles due to interaction with its magnetic field.

Seasons

• Earth's axis is tilted 23.5 degrees relative to its orbit around the sun.
• This tilt causes different areas to receive varying amounts of sunlight and heat at different times of the year.
• The Northern Hemisphere tilts toward the sun in summer, resulting in more light and heat, and away from the sun in winter.

Solstice

• The summer solstice, near June 21st, has the longest daylight and starts summer.
• The winter solstice, near December 21st, has the shortest daylight and starts winter.

Equinox

• Equinoxes occur when day and night are equal in length.
• The vernal equinox occurs around March 21st.
• The autumnal equinox occurs around September 22nd.

Lunar Phases

• The moon's rotation and revolution around Earth take approximately the same time (27.3 days), causing tidal lock.
• This means the same side of the moon always faces Earth.
• The moon reflects sunlight, making it visible from Earth.

Eclipses

• An eclipse occurs when one celestial body is obscured by another.
• The penumbra is a partial shadow; the umbra, a total shadow.
• Solar eclipses happen when the moon blocks the sun's light to Earth.
• Lunar eclipses occur when Earth blocks the sun's light to the moon.

Tides

• Tides are the rise and fall of ocean levels due to the moon's gravity.
• The moon's gravity pulls on Earth and its oceans, creating bulges of water.
• These bulges result in two high and two low tides per day.

The Solar System

• A solar system consists of one or more stars and the celestial bodies that orbit them.

Geocentric Model

• The geocentric model posited Earth at the center with other celestial bodies orbiting it.
• According to this model, stars were attached to an outer sphere.

Heliocentric Model

• The heliocentric model places the sun at the center with planets orbiting it.
• A planet's orbital radius and speed are related.
• Orbits are elliptical, not circular.

Distance Measurement

• An astronomical unit (AU) is the average distance from the sun to Earth (149.6 million km).

Planets of the Solar System

• Inner, Terrestrial Planets: Mercury, Venus, Earth, Mars

• Asteroid Belt: A region between the inner and outer planets containing billions of asteroids

• Outer, Gaseous Planets: Jupiter, Saturn, Uranus, Neptune

• Kuiper Belt: Located beyond Neptune, contains Trans-Neptunian icy objects, 30-50 AU from the Sun

Scattered Disk and Oort Cloud

• Located at the edge of the solar system, these areas are sources of comets
• Long-term comets, such as Halley's Comet, originate in the Oort Cloud at a distance of 50-10,000 AU.

Terrestrial Planets

• Mercury: Small, rocky, lacks an atmosphere, experiences extreme temperature variations, 0.3 AU from the Sun, fastest orbit and rotation.
• Venus: Thick carbon dioxide atmosphere, uninhabitable, hottest planet, opaque to telescopes, rotates east to west, 0.7 AU.
• Earth: Abundant liquid water in all three states, habitable zone, ozone layer protects from UV radiation, one moon, 1 AU.
• Mars: Thin CO2 atmosphere, iron oxide-rich surface gives it a red color, largest canyon and volcano, seasons, polar ice caps, 1.524 AU. Has two moons, Phobos and Deimos.

Asteroid Belt

• Between Mars and Jupiter, at 2.8 AU.
• Home to hundreds of asteroids; Jupiter's gravity prevented planet formation.
• Ceres is the largest object, originally considered a planet then a dwarf planet, now classified as an asteroid.

Gaseous Planets

• Jupiter: Largest planet, numerous satellites including the Galilean moons; Great Red Spot is a massive, long-lasting storm, 5 AU, fastest rotation.
• Galilean Satellites:
  • Ganymede: Largest moon, has a magnetosphere, saltwater ocean.
  • Callisto: Tidally locked with Jupiter, heavily cratered.
  • Io: Volcanically active due to tidal heating from Jupiter.
  • Europa: Icy surface, probable subsurface ocean.
• Saturn: Lower density than water, extensive ring system composed of icy particles.
  • Titan: Saturn's largest moon, has a dense atmosphere with lakes of hydrocarbons.
• Uranus: Ice giant composed of water, ammonium, and methane ice, has a blue color, axial tilt of almost 90 degrees, 10 rings, 28 moons. Unusual 84-year revolution.
• Neptune: Ice giant with high winds and disappearing storms, methane in the atmosphere, blue appearance, 17 moons. Triton is its largest moon, has a retrograde orbit. 30 AU, 165-year revolution.

Dwarf Planets

• Defined by the IAU as large objects that are not satellites but lack sufficient gravity to clear their orbits.
• Examples: Pluto, Eris, Ceres, Haumea, Makemake.

Distance Measurement in Space

• 1 AU = distance from Sun to Earth (150 million km).
• Light year = distance light travels in one year.
• Light travels 300 million meters in 1 second.

Significant Digits

• Any non-zero digit in a number, excluding leading and trailing zeros.

Scientific Notation

• A number written as a decimal number multiplied by 10 raised to an exponent.
• Negative exponents move the decimal to the left.
• Positive exponents move the decimal to the right.

The Big Bang Theory

• The universe began as a singular point and has been expanding ever since.
• Evidence includes the detection of cosmic microwave background (CMB) radiation in 1965, the afterglow from when the universe was hot and compact.
• Redshift of distant galaxies indicates the universe expands since objects moving away are stretched light waves.
• The abundance of hydrogen and helium in the universe matches predictions of the Big Bang.

Nebula

• A nebula is a massive cloud of gas and dust, spanning billions of kilometers.
• Gravity causes hydrogen and helium to clump together.
• Nebulae are the birthplaces of stars and star systems.

Solar Nebula Theory

• Our solar system formed from a spinning cloud of gas and dust called the solar nebula.
• Nuclear fusion started in the dense center of the nebula, forming the sun.
• Planets formed from the collection of material in the cloud.
• Rocky planetesimals formed closer to the sun.
• Gaseous planets formed from debris and gases in the outer regions.
• Planets orbit in the same plane around the sun in the same direction (counter-clockwise).

Exoplanets

• Planets orbiting stars other than our sun.
• Approximately 4,000 exoplanets have been discovered.

Retrograde Motion

• Planets typically move west to east.
• Retrograde motion is an apparent change in the direction of a planet's path, where it briefly moves east to west against the background stars.
• It occurs when a faster-moving planet overtakes a slower-moving one in their respective orbits.

Stars

• Stars are large masses of hot gases, primarily hydrogen and helium, that emit energy.
• Hydrogen nuclei fuse to form helium atoms, releasing vast amounts of energy.

Properties of Stars

• Brightness depends on distance and luminosity (energy released per second.)
• Closer stars appear brighter.
• Color indicates surface temperature, with blue being hotter and red cooler.
• Stars are composed of approximately 71% hydrogen and 27% helium.

Life Cycle of Stars

• Main sequence stars are in a stable phase of their life cycle.
• A star's life cycle depends on its initial mass.
  • Begins as nebula.
  • Protostar (dust cloud), the earliest stage of star formation.
  • A star is born when fusion ignites, entering the main sequence.
  • Eventually, the star exhausts its fuel.

Low Mass Stars

• Burn hydrogen fuel slowly, having long lifespans (100 billion years).
• Evolve into red dwarfs/giants.
• Outer layers drift away, forming a gaseous planetary nebula.
• Shrink to white dwarfs, then cool to black dwarfs.

Medium Mass Stars

• Burn hydrogen hotter and faster (10 billion years).
• When fuel is exhausted, they shrink, and carbon fusion begins, generating heat.
• The star expands into a red giant.
• Outer layers are blown away, shrinking to a white dwarf, then a black dwarf.

High Mass Stars

• Rapidly consume hydrogen, burning hot and blue.
• Evolve into supergiants.
• Heat produces heavy elements (iron).
• Have short lifespans (7 billion years).
• End in a supernova explosion.
• The supernova explosion creates other elements.
• Debris forms new nebulae and stars.

Star Core Outcomes (Supernovas)

• Can result in a neutron star, compressed to neutrons.
• Or a black hole, with gravity so strong that space, time, matter, and light are compressed.

Dark Matter

• Dark matter is invisible, emits no light radiation, and makes up 90% of the universe.
• Its presence is inferred from gravitational effects on visible matter.

The Hertaprung-Russell Diagram

• Relates a star's absolute magnitude (brightness) to its color/surface temperature and luminosity.
• Reveals relationships between:
  • Colour/surface temperature (blue to red)
  • Luminosity, the energy released (top bright, and dim bottom, with Sun equated to 1)
• Shows the main sequence band.
• Stars not on the main sequence are dying.
• Is used to determine the age of star clusters.
• Colour indicates temperature, and size/distance indicates luminosity.

Constellations

• Constellations are groups of stars forming a shape or pattern.
• Patterns within constellations are called asterisms (e.g., Orion's Belt).
• They are traditionally used for navigation and orientation with Polaris and circumpolar constellations that are close to the poles.

Star Positions

• Earth rotates west to east (counter-clockwise), so stars appear to rise in the east and set in the west.
• Earth's revolution makes some constellations visible only at certain times of the year (hemisphere dependent).

Star Distances

• Stars in a constellation are at vastly different distances from Earth.
• To find the distance between stars, subtract their individual distances.

Light Spectrum

• The Electromagnetic Spectrum is light energy (electromagnetic radiation), as a wave travelling.

• The different categories of light waves have different energy and wavelengths.

  • Radiowaves, microwaves, infrared, and visible light/colour are spaced out, and non-dangerous. -Ultraviolet, xrays, and gamma get smaller each time, and are dangerous.

• Refracting = bending light

• Reflecting = mirror light

• Radio = wave tech

• Different wavelengths of light from a star which can be analyzed by a spectroscope separates light into spectral colours (spectral lines are the dark lines).

• Lines show waves of light energy being absorbed by elements in the star, these have disappeared making a unique ‘barcode’ (so the sun has helium, etc.) must have all the lines.

Galaxies

• Four main shapes -all billions of stars.

• Spiral, with arms and central bulge (nucleus), and galactic halo of old stars

• Barred, spiral but with a bar in the mid section.

• Elliptical, a flattened sphere, which are merged spirals.

• Irregular arise from the collision of spirals, smaller/fainter

• Milky Way - spiral, 100k ly, part of the 20 in the ‘Local Group’ cluster (made in big bang).

• EARTH - Milky Way (galaxy,) Solar System (system), Orion Arm (interstellar neighbourhood), Milky Way Local Group (local collection), Laniakea Supercluster (local supercluster) Observable Universe (universe)

Canadian Contributions to Space

• Canadian astronauts (brief details about each), MOST, Canadarm, and ISS.

• Marc Garneau:- First Canadian in Space: Garneau was the first Canadian to go to space. He later became the first Canadian to head the Canadian Space Agency (CSA).

• Chris Hadfield First Canadian to Command the ISS.

• Roberta Bondar First Canadian Female Astronaut.

• The Canadarm is a robotic arm that was used on the Space Shuttle which was designed and built by the Canadian Space Agency

• MOST was Canada’s first space telescope (launched in 2003) which was designed to study the oscillations (vibrations) of stars.

• The ISS is a large spacecraft that orbits Earth and serves as a laboratory for scientific research in microgravity.