Scientific Method, Astronomy & Physics Final Exam Review

A comprehensive study guide covering the scientific method, planetary motion laws, stellar evolution, galactic structures, and cosmology for the Astronomy Final Exam.

What is the definition of Astronomy?

The study of objects beyond Earth and the processes that govern the universe.

List the six steps of the Scientific Method in order.

1. Observation, 2. Hypothesis, 3. Prediction, 4. Experiment/Observation testing, 5. Conclusion, 6. Revision if necessary.

Contrast the definitions of a Hypothesis and a Theory according to the notes.

A hypothesis is a testable explanation, while a theory is a broad explanation supported by evidence.

What is the approximate distance of one light-year?

$9.46 \times 10^{12}\,km$ (or 9.46 trillion km).

What is an Astronomical Unit (AU) and its value?

The average Earth-Sun distance, which is $150 \times 10^{6}\,km$ (or 150 million km).

How long does it take for light from the Sun to reach Earth?

8 minutes.

What are the 88 official patterns of stars in the sky called?

Constellations.

What causes the Earth's seasons?

Earth’s axial tilt of $23.5^\circ$, not the distance from the Sun.

List the phases of the Moon in the correct chronological order.

1. New Moon, 2. Waxing Crescent, 3. First Quarter, 4. Waxing Gibbous, 5. Full Moon, 6. Waning Gibbous, 7. Third Quarter, 8. Waning Crescent.

What is the difference between a Solar Eclipse and a Lunar Eclipse regarding moon phases?

A solar eclipse occurs at new moon (Moon blocks Sun), and a lunar eclipse occurs at full moon (Earth's shadow falls on Moon).

State Kepler's 1st Law.

The Law of Ellipses: Planets orbit in ellipses with the Sun at one focus.

What is the formula for Kepler's 3rd Law?

$P^2=a^3$, where $P$ is the orbital period in years and $a$ is the average distance in AU.

What is Newton's 2nd Law of Motion?

$F=ma$ (Force equals mass times acceleration).

Express the formula for Newton’s Universal Law of Gravitation.

$$F=G\frac{m_1m_2}{r^2}$$

List the seven categories of the electromagnetic spectrum from longest to shortest wavelength.

1. Radio, 2. Microwave, 3. Infrared, 4. Visible, 5. Ultraviolet, 6. X-ray, 7. Gamma ray.

What does Wien’s Law state about the relationship between temperature and wavelength?

Hotter objects peak at shorter wavelengths.

What is the difference between a Refracting and a Reflecting telescope?

Refracting telescopes use lenses and suffer from chromatic aberration; reflecting telescopes use mirrors and are preferred by astronomers.

List the layers of the Sun from the inside outward.

1. Core, 2. Radiative zone, 3. Convective zone, 4. Photosphere, 5. Chromosphere, 6. Corona.

What is the primary source of the Sun's energy?

Nuclear fusion in the core, where four hydrogen nuclei combine into helium, described by $E=mc^2$.

What are the Spectral Classes of stars ordered from hottest to coolest?

O, B, A, F, G, K, M (Mnemonic: "Oh Be A Fine Girl/Guy, Kiss Me").

What variables are compared on the axes of an H-R Diagram?

Luminosity (increasing upward) and Temperature (decreasing from left to right).

What is the formula for calculating distance using parallax?

$d=\frac{1}{p}$, where $d$ is in parsecs and $p$ is the parallax angle.

Who discovered the relationship between the period and luminosity of Cepheid variable stars?

Henrietta Swan Leavitt.

What are the five steps of the Star Formation process?

1. Giant molecular cloud collapses, 2. Protostar forms, 3. Temperature rises, 4. Fusion begins, 5. Main sequence star forms.

Contrast the characteristics of massive stars and low-mass stars on the main sequence.

Massive stars have shorter lives, are hotter, and are brighter; low-mass stars have longer lives, are cooler, and are dimmer.

What is the Chandrasekhar Limit?

The maximum mass of a white dwarf, which is approximately $1.4\,M_{\odot}$ (solar masses).

What is the difference between Special Relativity and General Relativity?

Special Relativity deals with time dilation and $E=mc^2$; General Relativity explains gravity as mass curving spacetime.

What are the four constituent parts of the Milky Way galaxy?

Disk, bulge, halo, and spiral arms.

State Hubble’s Law and its formula.

Farther galaxies move away faster; $v=H_0d$ (velocity equals the Hubble constant times distance).

What is a Quasar?

A ‘quasi-stellar radio source’ that is extremely distant, luminous, and powered by matter falling into a supermassive black hole.

Provide three pieces of evidence for the existence of Dark Matter.

1. Rotation curves (outer parts of galaxies rotate faster than expected), 2. Galaxy cluster motions, 3. Gravitational lensing.

What are the three main pieces of evidence for the Big Bang Theory?

1. Expansion of the universe (Hubble’s Law), 2. Cosmic Microwave Background (CMB) radiation, 3. Hydrogen and helium abundances.

What is the estimated age of the universe?

$13.8 \times 10^{9}$ years (or 13.8 billion years).

According to the notes, what is the composition of the universe?

5% ordinary matter, 27% dark matter, and 68% dark energy.

Why are Europa and Enceladus considered candidates for finding life?

Europa has a subsurface ocean beneath its icy crust; Enceladus has water plumes suggesting a subsurface ocean.

What is the Fermi Paradox?

The question: ‘If intelligent life should be common… where is everybody?’

What is the purpose of the Drake Equation?

To estimate the number of communicating civilizations in the universe.

What was Annie Jump Cannon's major contribution to astronomy?

Development of the stellar classification system (OBAFGKM).

Who determined that stars are mostly composed of hydrogen and helium?

Cecilia Payne-Gaposchkin.