Life Cycle of Stars and Structure of the Universe

Ejection of planetary nebula

Outer layers of a star are expelled.

Hot interior exposure

Star's core becomes visible after outer layers ejection.

Fusion shells

Regions where nuclear fusion occurs in a star.

High temperature and luminosity

Characteristics of a star's exposed core.

Density decrease in outer layers

Outer layers lose density as fusion ceases.

Sudden luminosity decrease

Rapid drop in brightness as fusion stops.

White Dwarf

Final stage of medium mass star after fusion.

Degenerate matter

Formed when a white dwarf contracts further.

Electron stripping

Electrons removed from atoms in white dwarf.

Resistance to contraction

Force preventing further collapse of degenerate matter.

Density of white dwarf

Very dense, comparable to Earth's size.

Sirius B teaspoon weight

Teaspoon weighs 15 tons on Earth.

Black dwarf

Final stage of a cooled white dwarf.

Protostar formation

Initial stage of star formation from molecular clouds.

Brown Dwarf

Star with mass < 0.08 solar masses, no fusion.

Main Sequence star

Stable phase where fusion occurs in the core.

Red dwarf star

Star with mass < 0.4 solar masses, slow death.

Shell burning

Occurs in stars with mass 0.4 to 8 solar masses.

Planetary nebula

Ejected outer layers of a star during death.

Chandrasekhar Limit

Maximum mass for a stable white dwarf.

Neutron star formation

Occurs when core collapses post-supernova.

Neutron star properties

Extremely dense, composed mostly of neutrons.

Neutron Star Formation

Occurs from core collapse of massive stars.

Chandrasekhar Limit

Maximum mass for white dwarf stability: 1.4 solar masses.

Supernova Explosion

Result of core collapse and outer layer ejection.

Event Horizon

Boundary beyond which nothing escapes a black hole.

Schwarzschild Radius

Radius defining the event horizon of a black hole.

Degenerate Electron Pressure

Pressure preventing collapse in white dwarfs.

Neutron Degeneracy Pressure

Pressure preventing collapse in neutron stars.

Neutron Star Density

Approximately 10^14 g/cm^3, extremely dense.

Neutron Star Size

Typically around 10 km in diameter.

Neutron Star Temperature

Exceeds 1 million K, primarily X-ray emission.

Pulsar

Rapidly rotating neutron star emitting beams of radiation.

Pulsar Discovery

First identified in 1967, pulsing every 1.337 seconds.

Black Hole Formation

Occurs if core mass exceeds 3 solar masses.

Core Collapse

Rapid contraction of stellar core under gravity.

Iron Core

Final stage of fusion in massive stars.

Shell Burning Stages

Different fusion processes occur in star layers.

Massive Star Characteristics

Stars > 8 solar masses undergo complex fusion.

Neutrino Production

Occurs during neutron formation in core collapse.

Magnetic Field of Neutron Stars

Up to a trillion times stronger than the Sun.

Angular Momentum Conservation

Causes rapid rotation of neutron stars.

Electromagnetic Radiation Beams

Produced by charged particles in neutron star's field.

Black Dwarf

Final fate of a cooled neutron star.

Material Near Black Holes

Stretches and accelerates due to extreme gravity.

Singularity

Point of infinite density in a black hole.

Escape Velocity

Speed needed to escape a gravitational field.

Event Horizon

Boundary beyond which nothing can escape a black hole.

Schwarzschild Radius

Radius defining the event horizon for non-rotating black holes.

Tidal Forces

Differential gravitational forces causing stretching effects.

Electromagnetic Radiation

Energy emitted by matter falling into a black hole.

X-rays

High-energy radiation emitted by matter near black holes.

Neutron Star

Dense stellar remnant, not exceeding 3 solar masses.

Binary System

Two stars orbiting a common center of mass.

Gravitational Effects

Influences of gravity felt near a black hole.

Black Hole Detection

Identifying black holes through their interactions with surrounding matter.

Compact Object

Dense astronomical body, possibly a black hole or neutron star.

Mass Measurement

Determining mass using gravitational effects in binary systems.

General Relativity

Einstein's theory explaining gravity's effect on space-time.

Glowing Plasma

Hot, ionized gas surrounding a black hole.

Supernova Explosion

Catastrophic stellar explosion marking the end of a star's life.

Degenerate Neutron Pressure

Force resisting collapse in neutron stars.

Infinite Density

Condition where matter's density becomes unbounded.

Observable Consequences

Effects that can be detected from outside a black hole.

Gravity Pull

Attraction exerted by mass on other masses.

Interstellar Medium

Matter existing in the space between stars.

Star Mass Comparison

Gravity of black holes matches stars at safe distances.

Dimming

Amount of light reduction based on distance.

Sea of Stars

Concept of a vast distribution of stars.

Globular Clusters

Tightly packed groups of millions of stars.

Milky Way Galaxy

Lens-shaped galaxy containing our solar system.

Shapley Estimate

Center of Milky Way near Sagittarius/Scorpius.

Dark Rift

Region in Milky Way obscuring star visibility.

Diameter of Universe

Estimated at ~100,000 light-years.

Distance to Center

Earth is ~28,000 light-years from center.

Radio Telescopes

Instruments that detect radio waves from space.

IR Telescopes

Instruments that detect infrared radiation.

Nuclear Bulge

Dense central region of the Milky Way.

Flat Disk

Region containing spiral arms of the galaxy.

O-class Stars

Young, hot stars used to identify structures.

Molecular Clouds

Cold hydrogen regions revealing spiral arms.

Barred Spiral Galaxy

Recent classification of the Milky Way's shape.

Galactic Nucleus

Center of the Milky Way with high star density.

Sagittarius A*

Supermassive black hole at the galaxy's center.

Stellar Density

Number of stars per cubic parsec.

Supermassive Black Hole

Massive black hole at galaxy's core.

Spherical Component

Includes high-density nucleus and low-density halo.

Disk Component

Region with spiral arms and star formation.

Shapley-Curtis Debate

1920 discussion on the scale of the universe.

Spiral Nebulae

Early term for distant galaxies with spiral shapes.

Island Universe

Concept of galaxies as separate entities.

Heber Curtis

Proposed the Sun is in a small galaxy.

Spiral Nebulae

Other galaxies resembling the Milky Way.

Standard Candle

Star with known absolute magnitude for distance measurement.

Apparent Magnitude

Brightness of a star as seen from Earth.

Absolute Magnitude (M_v)

Intrinsic brightness of a celestial object.

Edwin Hubble

Used a 100-inch telescope to study galaxies.

Andromeda Nebula

Estimated distance of ~2.9 million light years.

Hubble Classification

System for categorizing galaxy shapes.

Elliptical Galaxy

Smooth, featureless galaxy shape.