Astronomy

Absolutely! Here's your **Astronomy 101 Final Study Guide** formatted in **Q\&A style** for easy import into **StudyFetch**, Anki, Quizlet, or any other flashcard platform. Each item is phrased as a question with a clear, concise answer. Key concepts are **bolded** or *italicized* for emphasis where helpful. --- ### 🌟 CHAPTER 12: Characterizing Stars **Q: What is the spectral sequence and what does it represent?** A: **O, B, A, F, G, K, M** — from hottest (O) to coolest (M) stars. **Q: What is the spectral type of the Sun?** A: **G2V** **Q: What is the formula for trigonometric parallax?** A: $D = \frac{1}{p}$, where *D* is in parsecs and *p* is in arcseconds. **Q: What are the steps in spectroscopic parallax?** A: 1) Measure *apparent magnitude (m)* 2\) Determine *spectral type* 3\) Use HR diagram to find *absolute magnitude (M)* 4\) Use distance modulus: $$ d = 10^{\frac{(m - M + 5)}{5}} $$ **Q: What does the H-R diagram tell us?** A: Temperature, luminosity, and evolutionary stage of a star. **Q: What are main sequence stars classified as on the H-R diagram?** A: **Luminosity Class V (Dwarfs)** --- ### 🔥 CHAPTER 13: Stellar Evolution **Q: What is the mass-luminosity relationship?** A: $L \propto M^{3.5}$ — higher mass = much higher luminosity. **Q: What kind of variable stars use the period-luminosity relationship?** A: **Cepheid variables** **Q: What is nucleosynthesis?** A: The creation of new atomic nuclei from pre-existing protons and neutrons in stars. --- ### 💀 CHAPTER 14: Deaths of Stars **Q: What are the characteristics of open clusters?** A: *Young stars, found in the galactic plane, long main sequence, hundreds of stars.* **Q: What are the characteristics of globular clusters?** A: *Old stars, spherical shape, in the halo, short main sequence, 10⁴–10⁶ stars.* **Q: How can you determine the age of an open cluster?** A: By the point where stars leave the main sequence on the H-R diagram. **Q: What are the evolutionary endpoints of stars based on mass?** A: * <1.4 M☉ → **White dwarf** * 1.4–3 M☉ → **Neutron star** * > 3 M☉ → **Black hole** **Q: What supports white dwarfs and neutron stars?** A: * White dwarfs: *Electron degeneracy pressure* * Neutron stars: *Neutron degeneracy pressure* **Q: What is the difference between Type Ia and Type II supernovae?** A: Type Ia = white dwarf explosion from accreted mass; Type II = core collapse of massive star. **Q: What role do neutrinos play in supernova explosions?** A: They carry away energy and confirm the core collapse. **Q: What is the model for how pulsars shine?** A: A rotating neutron star emits beams of radiation like a lighthouse. --- ### 🕳️ CHAPTER 15: Black Holes **Q: Do radio pulses from pulsars change?** A: No, they are extremely regular. **Q: What is another name for the event horizon of a black hole?** A: **Schwarzschild Radius** **Q: What was the first strong black hole candidate?** A: **Cygnus X-1** **Q: What nuclear processes power stars?** A: * **Proton-proton chain**: for sun-like stars * **CNO cycle**: for hotter, massive stars **Q: What elements will the Sun fuse after leaving the main sequence?** A: Helium into carbon and oxygen **Q: How do you detect a stellar black hole?** A: By looking for **X-ray binaries** **Q: How do you detect a supermassive black hole in a galaxy?** A: By observing stellar or gas motions near the center --- ### 🌌 CHAPTER 16: Milky Way Galaxy **Q: What do binary stars help determine?** A: **Stellar masses** **Q: What are the types of binary star systems?** A: * Visual: Seen separately * Spectroscopic: Detected via Doppler shifts * Eclipsing: Brightness dips regularly * Astrometric: Star's motion reveals unseen companion **Q: What are the parts of the Milky Way and their stellar populations?** A: * **Bulge**: Older stars * **Disk**: Young, Pop I stars * **Halo**: Old, Pop II stars **Q: What causes spiral arms?** A: **Density waves** that compress gas and trigger star formation **Q: What is Sagittarius A*?*\* A: The **radio source at the center** of the Milky Way; likely a black hole **Q: What is the 21-cm line?** A: **Spin-flip transition** of hydrogen atoms; used in radio astronomy --- ### 🌀 CHAPTER 17: Galaxies **Q: What are the types of galaxies and their properties?** A: * **Spiral**: Young + old stars, gas and dust * **Elliptical**: Old stars, little gas/dust * **Irregular**: Mixed stars, variable gas/dust **Q: Why do elliptical galaxies show little star formation?** A: They have **no gas or dust**. **Q: What does a flat rotation curve in galaxies imply?** A: The presence of **dark matter** in the halo. --- ### 💥 CHAPTER 18: Quasars **Q: What does Hubble’s Law state?** A: $v = H_0 d$; the universe is expanding **Q: What is Hubble’s Constant?** A: \~**73.5 km/s/Mpc** **Q: What is the age of the universe?** A: About **13.4 billion years** **Q: What is at the center of a quasar?** A: A **supermassive black hole** **Q: Quasars are extreme examples of what?** A: **Active Galactic Nuclei (AGN)** **Q: Do quasars have high or low redshifts?** A: **High redshifts** **Q: What type of galaxy has a bright, star-like core?** A: **Seyfert galaxy** **Q: Where do quasars appear in the timeline of the universe?** A: In the **early (young)** universe --- ### 🌌 CHAPTER 19: Cosmology **Q: What is cosmology?** A: The study of the **origin, structure, and fate of the universe** **Q: What is Olber’s Paradox?** A: If the universe were infinite and static, the night sky should be bright. **Q: What explains galaxy sheets and voids?** A: Variations in the **cosmic microwave background (CMB)** **Q: What are the 3 predictions of the Big Bang Theory?** A: 1. Expanding universe 2. Universe mostly H & He 3. **Cosmic Microwave Background** **Q: What happened 380,000 years after the Big Bang?** A: The universe became **transparent**; light could travel freely **Q: What temperature is the CMB today?** A: \~**2.7 K** **Q: What is the cause of the universe’s accelerating expansion?** A: **Dark energy** **Q: What is GUT?** A: **Grand Unified Theory** — attempt to unify fundamental forces **Q: What is the process called when matter meets antimatter?** A: **Annihilation**, releasing gamma rays --- ### 👽 CHAPTER 20: Astrobiology **Q: What is the Drake Equation?** A: A formula to estimate the number of **civilizations** in the galaxy **Q: Are binary star systems good for habitable planets?** A: No, their **gravitational instability** is bad for planetary orbits **Q: Why is a large moon good for Earth-like planets?** A: It **stabilizes axial tilt and climate** **Q: Why is a distant Jupiter-like planet helpful?** A: It deflects comets and **reduces impact risk** **Q: What defines an element?** A: Its number of **protons** **Q: What star produced SN 1987A?** A: A **blue supergiant** **Q: What is a nova?** A: **Sudden brightening** from accreting matter on a white dwarf **Q: What is the end element of fusion in massive stars?** A: **Iron (Fe)** — it can’t be fused without consuming energy **Q: Where do we search for alien life?** A: Mostly in the **radio** part of the spectrum **Q: What’s a famous project for finding alien life?** A: **SETI** (Search for Extra-Terrestrial Intelligence) **Q: What is required to travel near the speed of light?** A: Enormous amounts of **energy**