THEORY EXAMINATION (SEM–IV) 2016-17 SPACE SCIENCE

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Course: B.Tech (All Branches – Common Elective)
Subject Code: EOE044
Subject Title: Space Science
Exam Type: Theory
Duration: 3 Hours
Maximum Marks: 100

SECTION – A (10 × 2 = 20 Marks)

Conceptual short-answer questions focusing on astronomy fundamentals

No.	Question	Concept Summary
(a)	Kepler’s Laws of Planetary Motion	(1) Planets move in elliptical orbits with the Sun at one focus. (2) The line joining planet and Sun sweeps equal areas in equal time. (3) T2∝R3T^2 \propto R^3T2∝R3, where T = period, R = semi-major axis.
(b)	Galaxy vs Active Galaxy	A galaxy is a gravitationally bound system of stars, gas, and dark matter; an active galaxy emits large non-thermal energy from its core due to supermassive black holes (e.g., Quasars).
(c)	Meteorites and Asteroids	Asteroids are rocky bodies orbiting the Sun, mostly between Mars and Jupiter; meteorites are fragments of these that reach Earth’s surface.
(d)	Black Hole & White Dwarf	Black Hole: collapsed star with gravity so strong that not even light escapes. White Dwarf: dense stellar remnant of a low-mass star after nuclear fuel depletion.
(e)	Radio-Quiet vs Radio-Loud Galaxies	Radio-loud: emit strong radio waves (e.g., Quasars); Radio-quiet: emit mainly visible and X-rays (e.g., Seyfert galaxies).
(f)	Perturbations of Stars	Small deviations in motion due to gravitational influence of nearby celestial bodies.
(g)	Variable & Composite Stars	Variable star: brightness changes with time (e.g., Cepheid). Composite star: binary system with distinct spectral components (e.g., Sirius A & B).
(h)	Role and Goal of Space Science	Understanding the universe, origins of celestial bodies, planetary exploration, and technological applications in satellite and communication systems.
(i)	Origin & Evolution of Planetary System	Based on Nebular Hypothesis — solar system formed from rotating gas–dust cloud contracting under gravity.
(j)	Hubble Expansion Model	Demonstrates that the universe is expanding; velocity of galaxies increases with distance (v = H₀d).

SECTION – B (5 × 10 = 50 Marks)

Descriptive and theoretical analysis questions

(a) Harvard Classification System

Based on spectral characteristics and surface temperature.

Spectral types: O, B, A, F, G, K, M (hottest to coolest).

Example:

Class	Color	Temperature (K)	Example Star
O	Blue	> 30,000	ζ Puppis
G	Yellow	5,500	Sun
M	Red	< 3,500	Betelgeuse

(b) Supernova

Definition: Catastrophic explosion marking the end of a massive star’s life.

Types:

Type I: No hydrogen lines (white dwarf collapse).

Type II: Hydrogen present (massive star collapse).

Produces neutron stars, black holes, and heavy elements.

(c) Quasars vs Microquasars

Feature	Quasars	Microquasars
Scale	Extragalactic	Within Milky Way
Power Source	Supermassive black hole	Stellar-mass black hole
Emission	Strong radio, optical, X-ray	X-ray and radio jets
Example	3C 273	SS 433

(d) Big Bang Theory – Early Universe

Planck Era (10⁻⁴³ s) – All forces unified.

Inflationary Epoch – Rapid expansion.

Nucleosynthesis – Formation of light elements.

Recombination Era – Atoms formed; cosmic microwave background (CMB) released.

Galaxy Formation – Matter condensed into stars and galaxies.

(e) Nebular Theory of Solar System Formation

Proposed by Kant and Laplace.

A rotating cloud of gas and dust collapsed under gravity → flattened disk → Sun formed at center → planets formed from accretion.

(f) Hertzsprung–Russell (H–R) Diagram

Plots luminosity (Y-axis) vs temperature (X-axis).

Main Sequence: Stable hydrogen-burning stars.

Red Giants / Supergiants: High luminosity, low temperature.

White Dwarfs: Low luminosity, high temperature.

(g) Kepler’s Law – Analytical Proofs

F=GMmr2F = \frac{GMm}{r^2}F=r2GMm (gravitational force).

Using angular momentum conservation:

r2dθdt=h=constantr^2 \frac{dθ}{dt} = h = \text{constant}r2dtdθ=h=constant

→ Derives equal-area law.

For third law:

T2=4π2GMr3T^2 = \frac{4π^2}{GM}r^3T2=GM4π2r3

(h) Life Cycle of the Sun

Nebular Stage → Protostar → Main Sequence (Current)

Red Giant Phase → Planetary Nebula → White Dwarf

Solar Winds: Streams of charged particles (mainly protons & electrons) ejected from corona.

SECTION – C (2 × 15 = 30 Marks)

In-depth and analytical long-answer questions

Q3. Galaxy and Active Galaxy

Normal Galaxy: Collection of billions of stars, dust, and gas bound by gravity (e.g., Milky Way).

Active Galaxy: Core emits enormous energy beyond normal starlight due to accretion of matter into a supermassive black hole.

Types: Seyfert galaxies, Quasars, Radio galaxies, BL Lac objects.

Features: Jets, radio lobes, X-ray/gamma-ray emissions.

Q4. Bode’s Law

Empirical Formula:

a=0.4+0.3×2na = 0.4 + 0.3 \times 2^na=0.4+0.3×2n

where aaa = planet’s distance (in AU), n=−∞,0,1,2,…n = -\infty, 0, 1, 2, …n=−∞,0,1,2,…

Predicts approximate spacing of planets in Solar System.

Valid for most planets except Neptune and Pluto.

Q5. Unification in Active Galaxies

Unification Theory explains different observed classes (Quasars, Seyferts, Radio galaxies) as same phenomenon viewed from different angles.

Key Patterns:

Orientation Model: Viewing angle affects visibility of jets or core.

Evolution Model: Active galaxies evolve from radio-loud quasars to radio-quiet Seyferts.

Energy Source: Accretion disk + relativistic jets around central black hole.

Summary

This Space Science (EOE044) paper comprehensively tests:

Topic	Focus
Celestial Mechanics	Kepler’s laws, Bode’s law, perturbations
Stellar Physics	Classification, life cycle, supernova
Galactic & Extragalactic Astronomy	Galaxies, quasars, unification models
Cosmology	Big Bang theory, universe expansion
Solar System Formation	Nebular theory, evolution of stars, Sun’s lifecycle