⭐ Space Physics – Black Holes, Galaxies & Universe Facts GK (1500+ Word SEO Article)
Space Physics, also known as Astrophysics, is the study of celestial objects and the physical laws that govern the universe. It covers everything from planets and stars to galaxies, black holes, dark matter, and the Big Bang.
This guide offers a complete understanding of these concepts along with 50 most important GK questions with answers. Ideal for Class 6–12 students, competitive exam aspirants, science lovers, and space enthusiasts.
🌌 What Is Space Physics?
Space Physics combines Physics and Astronomy to understand celestial phenomena such as:
Motion of planets
Gravity
Formation of galaxies
Life cycle of stars
Black holes
Big Bang
Dark matter and dark energy
It answers the most fundamental question:
“How does our universe work?”
💫 Universe: The Biggest Structure Known
The universe contains everything—matter, energy, time, and space.
Key Features of the Universe
Estimated age: 13.8 billion years
Diameter: 93 billion light-years (observable universe)
Contains:
100+ billion galaxies
Trillions of stars
Planets, moons, asteroids
Nebulae
Supermassive black holes
Dark matter & dark energy
🪐 What Is a Galaxy?
A galaxy is a huge collection of stars, planets, dust, and dark matter held together by gravity.
Types of Galaxies
Spiral Galaxy
Example: Milky WayElliptical Galaxy
Largest known structure in universe.Irregular Galaxy
No regular shape. Example: Large Magellanic Cloud.Lenticular Galaxy
Mix of spiral and elliptical.
Interesting Fact
Milky Way itself has 100–400 billion stars.
🌍 Milky Way Galaxy
Our home galaxy
Spiral-shaped
Sun is located in the Orion Arm
Rotates once every 225–250 million years
(called a Galactic Year)
☀️ Stars & Their Life Cycle
A star forms from clouds of gas & dust called nebulae.
Life Cycle of a Star
Nebula
Protostar
Main sequence star
Red giant / supergiant
White dwarf / neutron star / black hole
Stars die depending on their mass.
🕳️ What Is a Black Hole?
A black hole is a region in space where gravity is so strong that nothing—not even light—can escape.
How Black Holes Are Formed?
When a massive star collapses under its own gravity during a supernova explosion.
Key Terms
Event horizon: Boundary from where nothing can escape
Singularity: Central point of infinite density
Accretion disk: Hot rotating matter around the black hole
Types of Black Holes
Stellar black hole
Supermassive black hole (at galaxy centers)
Intermediate black hole
Mini black hole (theoretical)
🔭 What Is a Light-Year?
A light-year is the distance light travels in one year.
1 light-year = 9.46 trillion km
Not a measure of time—distance only.
🌠 What Is a Nebula?
A nebula is a large cloud of gas and dust in space.
Types:
Emission nebula
Reflection nebula
Dark nebula
Planetary nebula
Famous examples:
Orion Nebula
Crab Nebula
Nebulae are the birthplace of stars.
🌖 Dark Matter & Dark Energy
Dark Matter
Invisible substance that holds galaxies together.
Makes up 27% of the universe.
Dark Energy
Mystery energy that accelerates expansion of universe.
Makes up 68% of the universe.
Visible Matter (Everything we see)
Only 5% of the universe.
🌌 Big Bang Theory
The universe began from a single, extremely hot and dense point about 13.8 billion years ago.
Since then, it has been expanding.
🛰️ Important Space Agencies
NASA – USA
ISRO – India
ESA – Europe
JAXA – Japan
CNSA – China
Roscosmos – Russia
🌟 Space Physics – 50 GK Questions on Universe, Black Holes & Galaxies
1. What is the age of the universe?
Answer: 13.8 billion years.
2. What is the galaxy we live in?
Answer: Milky Way.
3. What type of galaxy is the Milky Way?
Answer: Spiral galaxy.
4. What is the largest structure in the universe?
Answer: The cosmic web of galaxy superclusters.
5. What is the closest star to Earth?
Answer: The Sun.
6. Second closest star to Earth?
Answer: Proxima Centauri.
7. What is a light-year?
Answer: Distance light travels in one year.
8. What is the speed of light?
Answer: 3 × 10⁸ m/s
9. What is a black hole?
Answer: Region where gravity is so strong that even light can’t escape.
10. What is the event horizon?
Answer: Boundary of a black hole.
11. What is a singularity?
Answer: A point of infinite density inside a black hole.
12. What is the Milky Way’s center called?
Answer: Sagittarius A* (supermassive black hole).
13. What is a galaxy?
Answer: Massive system of stars, dust, and dark matter.
14. What are nebulae?
Answer: Clouds of gas & dust in space.
15. What is the Orion Nebula?
Answer: A star-forming nebula.
16. What is dark matter?
Answer: Invisible matter detected through gravity.
17. What is dark energy?
Answer: Energy causing accelerated expansion of universe.
18. Universe is made of how much visible matter?
Answer: 5%
19. Largest known galaxy?
Answer: IC 1101.
20. What is a supernova?
Answer: Explosion of a massive star.
21. What is a neutron star?
Answer: Extremely dense star made mostly of neutrons.
22. What is a pulsar?
Answer: Rotating neutron star emitting radio waves.
23. What is a quasar?
Answer: Highly luminous active galactic nucleus.
24. What is cosmic microwave background (CMB)?
Answer: Remnant radiation from Big Bang.
25. What is the Big Bang Theory?
Answer: Theory that universe began from a single point.
26. What is Andromeda?
Answer: Nearest large galaxy to the Milky Way.
27. What is the Sun mainly made of?
Answer: Hydrogen (73%), Helium (25%).
28. What happens when a star dies?
Answer: Becomes white dwarf / neutron star / black hole.
29. What holds galaxies together?
Answer: Dark matter + gravity.
30. What causes day and night?
Answer: Earth’s rotation.
31. What causes seasons?
Answer: Tilt of Earth’s axis.
32. What is a comet?
Answer: Ice + dust body orbiting the Sun.
33. What is an asteroid?
Answer: Rocky body orbiting the Sun.
34. What is a meteor?
Answer: Shooting star burning in atmosphere.
35. What is a meteorite?
Answer: Meteor that reaches Earth’s surface.
36. What is space-time?
Answer: Combination of space and time dimensions.
37. What bends space-time?
Answer: Mass and gravity.
38. Who proposed General Relativity?
Answer: Albert Einstein.
39. What is gravitational lensing?
Answer: Light bending around massive objects.
40. What is a wormhole?
Answer: Theoretical shortcut in space-time.
41. What is Hubble’s Law?
Answer: Universe is expanding.
42. What telescope discovered universe expansion?
Answer: Hubble Space Telescope.
43. What is a dwarf planet?
Answer: Small planet-like body; e.g., Pluto.
44. What is the Kuiper Belt?
Answer: Region beyond Neptune containing icy objects.
45. What is the Oort Cloud?
Answer: Hypothetical cloud of comets surrounding solar system.
46. What is a solar eclipse?
Answer: Moon blocks Sun.
47. What is a lunar eclipse?
Answer: Earth blocks sunlight from Moon.
48. What is the hottest planet?
Answer: Venus.
49. What is the largest planet?
Answer: Jupiter.
50. What is the smallest planet?
Answer: Mercury.
51. What is the Sun’s energy source?
Answer: Nuclear fusion
Explanation: Hydrogen atoms fuse to form helium, releasing massive energy.
52. What is the name of our local group of galaxies?
Answer: The Local Group
Explanation: It contains 50+ galaxies including Milky Way & Andromeda.
53. What is the largest galaxy in the Local Group?
Answer: Andromeda Galaxy (M31)
54. What is the Schwarzschild radius?
Answer: The radius of a black hole’s event horizon.
55. What is a white dwarf?
Answer: Remnant of a medium-sized star after it exhausts fuel.
56. What is a red giant?
Answer: Stage when a star expands and cools after using hydrogen.
57. What is a brown dwarf?
Answer: Failed star not massive enough for fusion.
58. What is cosmic inflation?
Answer: Extremely fast expansion after the Big Bang.
59. Who discovered cosmic expansion?
Answer: Edwin Hubble.
60. What does redshift mean?
Answer: Light wavelength stretches → object is moving away.
61. What is blueshift?
Answer: Light wavelength compresses → object moves closer.
62. What protects Earth from solar radiation?
Answer: Magnetosphere.
63. What is the solar wind?
Answer: Stream of charged particles from the Sun.
64. What causes aurora?
Answer: Solar wind interacting with Earth’s magnetic field.
65. What is the hottest part of the Sun?
Answer: Core
Temperature: 15 million °C
66. What is the Sun’s outermost layer?
Answer: Corona
67. What are sunspots?
Answer: Cooler dark spots on the Sun caused by magnetic activity.
68. What is a binary star system?
Answer: Two stars orbiting each other.
69. What is the nearest galaxy to the Milky Way?
Answer: Canis Major Dwarf Galaxy (closest)
Andromeda (closest large galaxy)
70. What is a rogue planet?
Answer: Planet not orbiting any star.
71. What is a supercluster?
Answer: Largest galaxy groupings.
72. What is Virgo Supercluster?
Answer: Cluster containing the Milky Way.
73. What is Laniakea Supercluster?
Answer: The larger supercluster that includes Virgo Supercluster.
74. What is a black hole’s spin called?
Answer: Angular momentum.
75. What is Hawking Radiation?
Answer: Radiation predicted to be emitted by black holes.
76. Who proposed Hawking Radiation?
Answer: Stephen Hawking.
77. What is the shape of the Milky Way?
Answer: Barred spiral.
78. What is the Milky Way’s diameter?
Answer: ~100,000 light-years.
79. What is the Sun’s orbit speed around the Milky Way?
Answer: ~220 km/s.
80. What is the name of our Solar System’s center?
Answer: There is NO center; system revolves around the Sun.
81. What is cosmic dust?
Answer: Tiny solid particles in space.
82. What is interstellar medium?
Answer: Gas + dust between stars.
83. What is a protostar?
Answer: Early stage of star formation.
84. What is the Chandrasekhar limit?
Answer: 1.4 solar masses
Explanation: Maximum mass of a white dwarf.
85. What is gamma-ray burst (GRB)?
Answer: Most powerful explosion in the universe.
86. What is gravitational wave?
Answer: Ripples in space-time caused by massive objects moving.
87. Who first detected gravitational waves?
Answer: LIGO in 2015.
88. What is the Oort Cloud composed of?
Answer: Comets and icy bodies.
89. What is a solar flare?
Answer: Sudden explosion of energy on Sun’s surface.
90. What is a coronal mass ejection (CME)?
Answer: Large ejections of plasma from Sun.
91. What is the Kuiper Belt?
Answer: Region beyond Neptune with dwarf planets.
92. What is a planetary nebula?
Answer: Shell of gas ejected by dying star.
93. What is an exoplanet?
Answer: Planet outside our solar system.
94. What is the most Earth-like exoplanet?
Answer: Kepler-452b (popular candidate).
95. What is the nearest exoplanet to Earth?
Answer: Proxima b.
96. What is a cosmic ray?
Answer: High-energy particles from outer space.
97. What is the cosmic horizon?
Answer: Limit of observable universe.
98. What is the shape of the universe?
Answer: Flat (according to observations).
99. What is the multiverse theory?
Answer: Idea that multiple universes exist.
100. What is the fate of the universe?
Answer:
Possible theories include:
Heat death
Big Rip
Big Crunch