Astronomy Quiz 1

1. History of Astronomy

Key Figures and Their Contributions:

• Ptolemy: Proposed the Geocentric Model (Earth-centered universe).

• Copernicus: Suggested the Heliocentric Model (Sun-centered solar system).

• Galileo Galilei: Used telescopes to observe celestial objects; supported Heliocentrism.

• Tycho Brahe: Made detailed planetary observations.

• Johannes Kepler: Formulated the Laws of Planetary Motion.

• Isaac Newton: Developed the Law of Universal Gravitation.

Key Concepts:

• Geocentric Model: Earth is at the center of the universe.

• Heliocentric Model: The Sun is at the center of the solar system.

2. Telescopes

Types of Telescopes:

• Refracting Telescopes: Use lenses to gather and focus light.

• Reflecting Telescopes: Use mirrors to gather and focus light.

• Radio Telescopes: Detect radio waves from space.

• Space Telescopes: Operate outside Earth’s atmosphere (e.g., Hubble Space Telescope).

Important Terms:

• Aperture: Diameter of the primary lens or mirror; aMects light-gathering power.

• Magnification: Enlargement of an image.Celestial Sphere

Key Terms:

• Celestial Sphere: Imaginary sphere surrounding Earth where celestial objects appear.

• Zenith: Point directly overhead for an observer.

• Horizon: Where the sky meets the Earth.

• Celestial Equator: Projection of Earth's equator onto the celestial sphere.

• Ecliptic: Path of the Sun across the celestial sphere throughout the year.

Important Lines and Points:

• Meridian: Line running from North to South through the zenith.

• North Celestial Pole: Near Polaris (North Star).

• South Celestial Pole: Point directly opposite the North Celestial Pole.

4. Celestial Coordinates

Right Ascension (RA):

• Similar to longitude on Earth.

• Measured in hours, minutes, and seconds along the celestial equator.

• 24h of RA = 360° around the celestial sphere.

Declination (Dec):

• Similar to latitude on Earth.

• Measured in degrees north (+) or south (−) of the celestial equator.

• Ranges from +90° (North Celestial Pole) to -90° (South Celestial Pole).

How to Use Celestial Coordinates:

• Right Ascension determines when an object will cross the meridian.

• Declination determines how far north or south an object is from the celestial equator.Star Movements

Daily Motion:

• Caused by Earth's rotation.

• Stars appear to rise in the East and set in the West.

• Circumpolar Stars: Never set and move around the celestial pole.

Annual Motion:

• Caused by Earth's orbit around the Sun.

• Seasonal constellations change due to Earth’s changing position.

Special Movements:

• Parallax: Apparent shift in a star's position due to Earth's movement, used to measure

distances to nearby stars.

6. Constellations

Types of Constellations:

• Circumpolar Constellations: Always visible in the night sky (e.g., Ursa Major).

• Seasonal Constellations: Visible only during certain seasons.

• Zodiac Constellations: Lie along the ecliptic path.

Be able to identify constellations

• Orion: Visible in winter; contains bright stars Betelgeuse and Rigel.

• Ursa Major: Contains the Big Dipper, used to find Polaris.

• Cassiopeia: W-shaped, near the North Celestial Pole.

• Seasonal Changes: Constellations visible depend on the time of year. Right Ascension and Declination:

o If a star is at RA 6h and Dec +30°, when would it be highest in the sky? yes it would be

o Which stars would be circumpolar from a latitude of 45° N?stars with decliantion greater thean 45 N

• Constellation Identification:

o Where would you look to find Orion in January at 9:00 PM? Orion would be visible in the southern sky.

o Which constellation points to Polaris? Ursa Major .

o How do RA and Dec help in locating celestial objects? helps pinpoint the location of clestial objects in sky, RA is similar to longititude on Earth and measures East- West postion, while Dec is similar to lantitude and measures north-south postion,

o Why do constellations appear to shift throughout the year? due to earths revloution around the sun.

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