ASP History of Astronomy 2

Question 1

Edwin Hubble's observations in the 1920s proved that 'spiral nebulae' such as Andromeda were actually distant galaxies. Which type of variable star did he use to measure their distances?

Accepted Answer

Cepheid variables

Answer

Hubble used Cepheid variable stars, whose period-luminosity relationship (discovered by Henrietta Swan Leavitt) allowed him to calculate that the Andromeda nebula was far outside the Milky Way.

Question 2

Which ancient Greek thinker first proposed a heliocentric model of the solar system, more than 1,700 years before Copernicus?

Accepted Answer

Aristarchus of Samos

Answer

Aristarchus of Samos proposed a heliocentric model around 270 BCE, also estimating the relative sizes of the Sun and Moon, but his model was largely rejected in favor of the geocentric view.

Question 3

William Herschel discovered which planet in 1781, the first planet found in recorded history rather than known since antiquity?

Accepted Answer

Uranus

Answer

William Herschel discovered Uranus on March 13, 1781, using a homemade telescope, making it the first planet discovered in modern times and doubling the known size of the solar system.

Question 4

Annie Jump Cannon developed the Harvard stellar classification system (OBAFGKM). What physical property of stars does this sequence primarily reflect?

Accepted Answer

Surface temperature

Answer

The OBAFGKM sequence orders stars by decreasing surface temperature, with O-type stars being the hottest (>30,000 K) and M-type stars being the coolest (~3,000 K).

Question 5

Henrietta Swan Leavitt's 1908 discovery of the period-luminosity relationship in Cepheid variable stars allowed astronomers to determine what?

Accepted Answer

Distances to objects beyond the Milky Way

Answer

By relating the pulsation period of a Cepheid to its intrinsic brightness, Leavitt created a 'standard candle' that enabled accurate distance measurements to nearby galaxies.

ASP - Astronomical Society of the Pacific Exam Practice Test

ASP - Astronomical Society of the Pacific Exam Practice Test

ASP History of Astronomy 2