Astronomical Measurements and Parallax

Which method did Eratosthenes employ to accurately estimate the Earth's circumference?

• Measuring the time it took for a ship to circumnavigate the globe.

• Observing the gradual disappearance of ships over the horizon.

• Comparing the angle of the sun's rays at noon in two different cities on the summer solstice.

• Using a primitive telescope to gauge the Earth's apparent size from the Moon.

After determining the Earth's size, what celestial measurements did Aristarchus of Samos successfully calculate?

• The distances to the nearest stars and their relative brightness.

• The distances to the Moon and the Sun, along with their respective sizes.

• The orbital periods of all known planets in the solar system.

• The total mass of the solar system.

What fundamental astronomical measurement is defined as the Astronomical Unit (AU)?

• The distance from Earth to the closest exoplanet.

• The average distance between the Earth and the Sun.

• The distance light travels in one year.

• The radius of the Milky Way galaxy.

How did astronomers in the 1960s achieve highly precise measurements of the Astronomical Unit?

• By analyzing the gravitational pull between Earth and the Sun.

• By launching space probes to directly measure the distance to the Sun.

• By bouncing radar pulses off Venus and accurately timing their return.

• By observing the apparent shift of distant stars due to Earth's orbit.

What phenomenon allows humans to perceive the distance of nearby objects by comparing images from each eye?

• Refraction

• Diffraction

• Parallax

• Accommodation

How do astronomers utilize Earth's movement to measure the distance to stars using parallax?

• By observing a star from different points on Earth's surface simultaneously.

• By measuring the star's apparent brightness at different times of the year.

• By observing a star from opposite sides of Earth's orbit around the Sun.

• By comparing the star's spectrum to that of the Sun.

Which star was the first to have its parallax successfully measured, and approximately how far away is it in light-years?

• Alpha Centauri, 4.3 light-years

• Sirius, 8.6 light-years

• 61 Cygni, 11.4 light-years

• Proxima Centauri, 4.2 light-years

What is a light year?

• A light year is a unit of distance equal to the distance light travels in one year.
• A light year is a measure of time.
• A light year is the speed of light in a vacuum.
• A light year is a unit of weight used in astronomy.

How many light years in 1 parsec?

• 3.26 light years
• 1.0 light years
• 2.5 light years
• 4.0 light years

If two stars have the same intrinsic brightness, but one is twice as far away as the other, how will its apparent brightness compare to the closer star?

• It will appear half as bright.

• It will appear one-quarter as bright.

• It will appear four times as bright.

• It will appear the same brightness.