Star Properties and Evolution

Main Sequence Star Alignment

• Massive, hot, and blue stars are located in the top left.
• Stars in the top middle are hot and white or blue, but less massive than those in the top left.
• Supergiants are in the top right, cooler but with high luminosity, and red in color.
• Cool and small red dwarf stars are in the bottom right.
• Stars in the bottom middle are smaller and moderately hot, typically yellow like the sun.
• Very cool white dwarfs, which are dying stars, are in the bottom left.

Distance Measurements

• An astronomical unit (AU) is the average distance between the Earth and the Sun.
• Jupiter is 5.20 AU from the Sun.
• Saturn is 9.54 AU from the Sun.
• The Sun's diameter is 109 times Earth's diameter.
• The Sun's mass is 332,800 times Earth's mass.

Evolution to Giant Stage

• A star begins to die and expand into a giant when hydrogen fusion into helium ceases.

Continued Evolution of High Mass Stars

• When hydrogen fusion stops in a high-mass star, it can turn into a supernova, or if the core is dense enough, it can form a neutron star.

Birth of Stars

• Gravity causes a gas cloud to shrink and fragment.
• The core of this shrinking cloud heats up.
• Fusion begins when the core becomes hot enough, halting the shrinking process.
• The new star achieves a state of balance.
• A shock wave from a space event can trigger star formation by disrupting the gravitational balance within a birthing cluster.

Sun-like Stars Track and Death

• The life cycle of a sun-like star: Nebula -> Main Sequence -> Red Giant -> Planetary Nebula -> White Dwarf (NMRPW).
• As sun-like stars die, fusion slows, leading to a red giant phase, followed by helium fusing into carbon and oxygen.

Type I and II Supernova

• Type I supernovae do not have hydrogen.
• Type II supernovae have hydrogen.

Dark Matter

• Dark matter may consist of protons, electrons, and unknown particles.
• The existence of dark matter is proposed to explain observations that would otherwise require a revision of our understanding of gravity.

Other Galaxy Types

• Active Galaxy
• Radio Galaxy
• Galactic Nuclei (AGN)
• Seyfert Galaxy
• Double Lobed Radio Source
• Quasar
• Blazar

Expanding Universe

• The universe is constantly expanding, causing galaxies farther away to appear to recede from us at very high speeds.

Structure of the Universe

• The universe consists of clusters and superclusters of galaxies.
• A cluster is a smaller version of a supercluster.

Cosmology

• Cosmology involves theories supported by evidence about space stretching out, causing the universe to expand at an accelerating rate.

Open and Closed Universes

• The closed universe theory suggests the universe is a closed sphere.
• The open universe theory suggests the universe will expand indefinitely.

Doppler and Cosmological Redshift

• The Doppler effect explains how the motion of an object affects sound and light by using its direction of travel.
• Cosmological redshift uses the same principle to describe the expansion rate of the universe.

Big Bang Theory

• Cosmic microwave background radiation, detected in the 1960s, helped determine when the Big Bang occurred.

Problems with Big Bang Theory

• Unanswered questions include what existed before the Big Bang and the lack of conclusive proof of dark matter.

General Features of Planets

• Planets can be icy, rocky, or gaseous.
• Planets are spherical, orbit a star, and have an atmosphere and rotation.

Origin of Solar System

• The solar system is approximately 4.6 billion years old.
• It formed from a solar nebula (composed of hydrogen and helium) that collapsed under gravity and flattened into a disk.

Rocky Planets

• Mercury
  • Closest planet to the Sun.
  • Its surface is similar to the Moon.
  • It has a dense iron core and a very thin atmosphere.
• Venus
  • Has 0.89 of Earth's mass.
  • It has a slow rotation.
  • Its surface temperature is hot enough to melt lead.
  • One Venus day is equivalent to 243 Earth days.
• Earth
  • Is 1.00 AU from the Sun.
  • It is the densest major body in the solar system.
  • 71% of its surface is covered in water.
• Moon
  • Is 384,400 km from Earth.
  • Has 0.28 of Earth's diameter and 0.01 of Earth's mass.
  • It has no atmosphere.
• Mars
  • Has lost its atmosphere, reducing the likelihood of surface carbon-based life, though it is still possible below the surface.

Jovian Planets

• Jupiter
  • Is twice as massive as all other planets combined.
  • It has no solid surface.
  • It has a core of rocky material, high winds and a strong magnetic field.
  • It's distance from the sun is 5.20 AU
  • Its primarily composed of 90% hydrogen.
  • Its diameter is 11.19 times Earth's diameter and its mass is 318 Earth masses.
• Saturn
  • Is 9.54 AU from the Sun.
  • Has a diameter 9.4 times Earth's and a mass of 95 Earths.
  • Its primarily composed of 75% hydrogen.
  • It radiates more energy into space than it receives from the Sun.
• Uranus
  • Has a mass of 15 Earths and a diameter 4.04 times Earth's.
  • It has 11 rings and 27 satellites (moons).
• Neptune
  • Has a mass of 17 Earths and a diameter 3.88 times Earth's.
  • Its blue color is due to the absorption of red light by methane in the atmosphere.
  • Experiences high winds and has 14 satellites.
  • Radiates more than twice as much energy as it receives from the Sun.

Asteroid Belt

• The asteroid belt is located between Mars and Jupiter.