Stars and Nebulae: Formation and Types

• The Sun is the main source of energy on Earth.
• Stars are members of the Solar System
• Stars are huge glowing balls of hot gas, mainly hydrogen and helium.
• When stars grouped together, they form constellations.
• Stars are a ball of plasma held together by its own gravity.
• The Eagle Nebula is where Stars are born.

Nebulae

• Nebulae are giant clouds of dust and gas in space.
• They serve as nurseries for stars
• Nebulae originate from the gas and dust of dying star explosions.

Common Nebulae

• Carina Nebula
• Ant Nebula
• Omega Nebula
• SNR B0509-67.5
• Rosette Nebula
• Crab Nebula
• NGC 604
• Helix Nebula
• Red Rectangle Nebula

Birth of Stars

• Stars are formed from giant clouds of dust and gas
• Gravity causes the cloud to collapse into a rotating gaseous ball.
• Once the new star gets hot, it creates energy through nuclear fusion.

Evolution of Stars

• Stellar Cloud with Protostars
• Small Star evolves into a Red Giant and Planetary Nebula before becoming a White Dwarf
• Large Star becomes a Red Supergiant and Supernova before either becoming a Neutron Star or Black Hole.

Star Temperature and color

• Cooler stars tend to be red or orange.
• Hotter stars tend to be white or blue.
• Stars in mid ranges tend to be yellow.

Distance

• Stellar distances are measured in light-years.
• A light-year is the distance light travels in one year, equivalent to 9.46 x 10^12 km or nearly 6 trillion kilometers.
• The Earth is approximately 8.3 light-minutes from the Sun
• The North Star, Polaris, is 320 light-years away
• Proxima Centauri, the closest neighboring star, is 4.3 light-years away
• Andromeda, the closest neighboring galaxy, is 2.5 million light-years away
• The center of the Milky Way galaxy is 26,000 light-years away
• The oldest galaxy ever found, GN-z11, is 13.4 billion light-years away

Brightness

• Luminosity is the amount of light that a star radiates
• Magnitude refers to a star perceived brightness

Magnitude

• Magnitude or absolute magnitude measures a star's true brightness
• Absolute magnitude is the magnitude of a star at a certain standard distance.
• Apparent magnitude is the brightness of stars as seen on Earth.

Dwarf Stars

• Small stars that are 20 times larger than the Sun and 20,000 times brighter.
• Most main sequence stars are these

Red Dwarf Stars

• By far the most common stars in the milky way
• Generally low luminosity

Blue Giants

• Huge, hot stars that usually burns helium.

Super Giants

• The largest know type of stars
• Betelgeuse and Rigel are the example of super giants.

Stellar Mass

• Stellar mass is key, but tough to measure.
• Kepler's laws of planetary motion is applicable.
• The sum of two stars' masses equals their mean distance cubed divided by their revolution squared.

Hertzsprung-Russell Diagram

• It classifies stars based on absolute magnitude (brightness) and spectral type (temperature/color).
• Supergiants are at the top, then giants, with White dwarfs at the bottom
• Sun is in the middle with Main sequence stars

The Sun

• It is a yellow dwarf medium sized star
• It has an estimated lifespan of approximately 5 billion years.
• Once it exhausts its hydrogen supply, it will expand into a red giant, then condense into a white dwarf.

Twinkling Stars

• Stars twinkle because of stellar scintillation/astronomical scintillation because of refraction of the light passing through the Earth’s atmosphere.

The Death of Stars

• Stars will die if they run out of gases to burn.
• The star will expand into a super giant.
• A star can have multiple ends including, Planetary Nebula, Black Hole, and Gamma Ray Burst.
• After a star explodes it can form the Crab Nebula