Astronomy Quiz: Stellar Dynamics and Properties

Unit E: Space - Section 1

• The night sky has fascinated humans for a long time
• Objects in the night sky include the Sun, Moon, constellations, and planets
• Events in the sky include meteor showers, eclipses, and the northern lights

Tracking Cosmological Events

• A summer solstice occurs near June 21st in the Northern Hemisphere. It is the longest period of daylight
• A winter solstice occurs around December 21st in the Northern Hemisphere. It is the shortest period of daylight
• These events are reversed in the Southern Hemisphere
• An equinox occurs twice a year (March 21st and September 21st). The day and night are equal length

About 500 Years

• For 2000 years, humans believed Earth was the center of the universe with everything revolving around it
• This geocentric model was proposed by Aristotle
• The model included Earth at the center, the Sun, the five known planets, and fixed stars

Heliocentrism

• In 1530, Nicholas Copernicus proposed a heliocentric model—the Sun at the center of our solar system
• All other planets, including Earth, revolve around the Sun

One Little Problem

• The idea that planets moved in circular orbits was not perfect
• Johannes Kepler proposed that planets orbit in ellipses—this improved the model of the solar system

Improving Technology

• Our understanding of space has improved over time
• Tools and techniques have been developed to observe what is millions of kilometers away
• Simple tools like sundials have been used for over 7000 years

Important Tools

• Quadrants: Used since 200 A.D. to measure a star's height above the horizon
• Astrolabes: Used to create accurate charts recording star positions
• Cross Staffs: Used since the 14th Century to measure the angle between objects in the sky
• Telescopes: Used since the 16th Century to explore the night sky in depth, including modern radio telescopes that orbit space

The Hubble Space Telescope

• The Hubble Space Telescope is believed to be able to view events that occurred up to 12 billion years ago

Time and Distance

• Space is very large. Kilometers are not suitable units of measurement
• Astronomers use astronomical units (AU) and light-years (LY)
• 1 LY = 5.8 trillion miles (9.4 trillion kilometers)

Astronomical Units

• An AU is the average distance between Earth and the Sun
• About 149,599,000 km

Light Years

• A light-year is the distance that light travels in one year
• Light travels at nearly 300,000 km/s, so in one year it travels almost 9.5 trillion kilometers

What is a Star?

• Stars are giant balls of burning gases (primarily hydrogen and helium) giving off immense light
• Stars can vary greatly in appearance

How are Stars Made?

• Stars are born in nebulae, which are clouds of hydrogen gas
• Gravity pulls the molecules together, increasing pressure and temperature until a star forms

Protostars

• Once the central core of a star is capable of producing its own light, it becomes a protostar
• This stage can last up to 50 million years

The Life of Stars

• Stars reach temperatures of 27 million degrees F
• Hydrogen is converted into helium, releasing massive amounts of energy
• This conversion lasts about 10 billion years

The Death of Sun-like Stars

• When a sun-like star runs out of hydrogen, it expands into a red giant
• It cools and shrinks into a cold, dark star the size of Earth—this is a white dwarf
• The dwarf will fade until it becomes a black dwarf (this is theoretical)

The Death of Massive Stars

• When a massive star runs out of hydrogen, it becomes a red giant
• Instead of shrinking, massive stars explode into a supernova
• A super nova can form a black hole

Constellations and Asterisms

• A constellation is a group of stars that create patterns in the sky
• There are 88 recognized constellations; all other patterns are asterisms including parts of constellations

The Big Dipper & Ursa Major

• The Big Dipper, although a recognizable pattern, is actually an asterism within the constellation Ursa Major

Star Temperature

• A star's color indicates its temperature. Hotter stars appear bluer, cooler stars appear redder
• The Hertzsprung-Russell diagram is a visual representation of stars and their temperatures and sizes

Analyzing Stars

• Starlight produces a wavelength on the visible light spectrum
• We can determine the makeup of stars by the type of light they emit

The Doppler Effect

• Lightwaves are compressed when an object moves towards Earth, resulting in a blue shift
• Lightwaves stretch out when an object moves away from Earth, resulting in a red shift

Galaxies

• Galaxies are groups of millions or billions of stars, dust, and gas held together by gravity
• There are billions of galaxies in the universe

Asteroids

• Asteroids are chunks of rock and ice that are between Mars and Jupiter
• There are more than 100,000 asteroids
• It's believed the asteroid belt is the remnant of a destroyed planet

Comets

• Comets are chunks of rock and ice orbiting the Sun, often going far out to the edge of our solar system
• They can take thousands of years to complete an orbit
• Tails are produced from melting ice and gas from the heat of the Sun

What Causes a Comet's Tail?

• As comets approach the Sun, they heat up and ice melts, producing gaseous and dust tails

Meteoroids, Meteors, and Meteorites

• Meteoroids are small pieces of rock in space with no particular path
• Meteors occur when a meteoroid enters Earth's atmosphere
• Meteorites occur when a meteor is large enough to reach the ground before disintegrating

Our Solar System

• Most of the planets are named after Roman mythological gods
• The order of planets from the Sun is: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto

The Protoplanet Hypothesis

• The protoplanet hypothesis describes the formation of solar systems.
• A cloud of gas and dust swirls around
• The bulk of dust collects to form the star
• The remaining material accumulates in clumps forming planets

The Inner Planets

• Mercury: distance from the sun: 0.39 AU, average surface temp: 180°, # of moons: 0
• Venus: distance from sun: 0.72 AU, average surface temp: 480°, # of moons: 0
• Earth: distance from sun: 1.00 AU, average surface temp: 15°, # of moons: 1
• Mars: distance from sun: 1.52 AU, average surface temp: -53°, # of moons: 2

The Outer Planets

• Jupiter: distance from sun: 5.27 AU, moons: 28
• Saturn: distance from sun: 9.54 AU, moons: 19
• Uranus: distance from sun: 19.19 AU, moons: 15
• Neptune: distance from sun: 30.06 AU, moons: 8
• Pluto: distance from sun: 39.5 AU, moons: 1

The Parallax Effect

• Parallax refers to the apparent shift in the position of an object when viewed from two different locations
• This is not the actual shift of the object, but a change in the angle of view

So How Do We Locate Celestial Objects?

• To locate objects in space, we need to identify their altitude (measured from 0° to 90°) and azimuth (measured from 0° to 360°)
• Zenith is the point directly above an observer

Determining a Star's Composition

• Stars' composition can be determined by measuring the absorption spectrum of the light the emit

Space Probes

• Unmanned spacecraft used to explore distant parts of the solar system.
• Examples include: NASA's Perseverance rover

Using Technology to Interpret Space

• Technology is crucial to astronomical understanding
• Telescopes, space stations, and probes increase comprehension of space objects

Measuring Distance–Triangulation

• Triangulation, a method for determining distance, uses the geometry of a triangle to make measurements from angles and distances
• An object's distance is determined by measuring angles using a baseline and the object.

Remote Sensing

• Remote sensing is a satellite-based method to collect information on Earth's surface, environmental changes, natural resources and urban areas
• Satellites using imaging devices make observations and transmit data

GPS: Global Positioning Systems

• GPS uses an arrangement of 27 orbiting satellites to determine a location's position on Earth.
• Receivers identify the overlapping area of signals from several satellites to determine the most probable location.

Fact or Fiction

• Ball point pens were not well suited for use in space, so a special pen was developed, costing NASA 12 billion dollars!

Hazards in Space

• Some hazards in space are damaging cosmic rays, meteoroids, extreme temperatures, and the lack of atmospheric pressure.

Achievements in Rocket Science

• Overcoming forces of gravity to achieve orbit
• Developing and maintaining functioning equipment in space
• Safely getting to space and returning

Propulsion

• Early breakthroughs in propulsion included a Greek method of using steam to propel wings (400 BC), to a later Chinese use of gunpowder for rockets (2000 years ago).

Some Space “Firsts”

• Sputnik, launched by the Soviet Union in 1957, was the first artificial satellite to orbit Earth
• Laika, a dog, was sent into space by the Soviet Union one month after Sputnik

Alouette 1

• Alouette 1 was the first satellite launched by Canada
• This made Canada the third country to design, build, and launch its own satellite

The Physics of Rockets

• Rockets operate on Newton's Third Law of Motion (“for every action, there is an equal and opposite reaction”)

Parts of a Rocket

• Rockets have structural elements, fuel, and a payload (all of the necessary materials).
• Payload weight can prevent launch

The Future of Rocketry

• Future possibilities include ion drives (powered by electrically charged xenon) and solar sails (powered by electromagnetic energy).

Types of Spacecrafts

• Shuttles: transport people and equipment to orbiting spacecraft.
• Space Probes: contain equipment for exploring space.
• Space Stations: are orbiting spacecraft designed for long-term stays.

Let’s Talk About Satellites

• Satellites, are objects in orbit around a planet
• Natural and artificial satellites exist
• Satellites have multiple functions including communication, weather forecasting, TV watching, and positioning systems

Satellite Placement

• Geosynchronous Orbits: satellites orbit Earth at a speed matching Earth's rotation. They appear stationary above a particular spot on Earth
• Low Earth Orbits: satellites orbit lower to Earth, making observation faster.

LANDSAT & RADARSAT

• Specific satellites that track ships, environmental changes, and natural resources

Remote Sensing

• Imaging devices on satellites make observations of Earth. Information on conditions, natural resources, and urbanization is used in planning.

GPS: Global Positioning Systems

• The GPS system includes an arrangement of 27 satellites. Each satellite transmits its position information, and a GPS receiver calculates its location by intersecting signals from several satellites.

Take a Look!

• GPS example of using overlapping location data from 3 satellites to calculate a specific position