Electromagnetic Spectrum & Star Classification

• The images in the pre-test are for matching with the corresponding names of celestial objects.

Observatories and the Electromagnetic Spectrum

• Observatories utilize the electromagnetic spectrum.
• The electromagnetic spectrum includes gamma rays, X-rays, ultraviolet, visible light, infrared, microwave, and radio waves.
• NASA's Hubble, Webb, and Spitzer space telescopes detect portions of the electromagnetic spectrum.
• The Hubble Space Telescope detects from approximately 90-2,500 nm.
• The James Webb Space Telescope detects from around 600-28,500 nm.
• The Spitzer Space Telescope detects from roughly 3,000-160,000 nm.

Stellar Classification and Evolution

• Stars are classified by temperature, color, spectral type, and luminosity or absolute magnitude, all linked to their age in stellar evolution.
• The Hertzsprung-Russell diagram correlates spectral classification with absolute magnitude and temperature.

Life Cycle of a Star

• A star's life cycle includes stages such as:
• Stellar Nebula
• Protostar
• Average Star or Massive Star
• Red Giant or Red Supergiant
• Planetary Nebula or Supernova
• White Dwarf, Neutron Star, or Black Hole

Nebulae

• A nebula comes from the Latin word for "cloud".
• Nebulae are interstellar clouds of gas and dust.
• Many nebulae form from dying stars' remnants.
• Nebulae are often regions where new stars are born.
• Examples: Eagle Nebula, Carina Nebula, Lagoon Nebula, Protostar in Nebula L1527

Sun-like Stars

• Sun-like stars share characteristics like near-solar surface temperature, size, chemical composition, and age.
• Our sun is a 4.5 billion-year-old yellow dwarf star, made of hydrogen and helium, held together by gravity. Alpha Centauri is the sun's closest neighbor.

Red Giants

• They form after a star exhausts hydrogen fuel for nuclear fusion and begins to die.

Planetary Nebulae

• A planetary nebula is a type of emission nebula, which consists of glowing, expanding shell of ionized gas ejected from red giant stars late in life

White Dwarfs

• They are stellar cores left after a dying star uses all nuclear fuel and expels outer layers to form a planetary nebula.

Red Supergiants

• Massive stars leaving the main sequence become red supergiants.
• Betelgeuse is a red supergiant with a diameter of approximately one billion miles and would extend to Jupiter's orbit if placed in our Solar System.

Supernovas

• A supernova indicates a powerful and luminous explosion of a star, occurring in massive stars' late evolutionary stages or when a white dwarf undergoes runaway nuclear fusion.
• The Crab Nebula is a six-light-year-wide remnant of a star's supernova explosion.

Neutron Stars

• They are incredibly dense remnants of supermassive stars that have exploded as supernovae.

Black Holes

• They are massive, compact astronomical objects with gravity so strong that nothing, including light, can escape.

Objects Visible to the Naked Eye

• Planets like Venus, Mars, Jupiter, and Saturn are easily visible, and Mercury and Uranus can sometimes be seen.
• Many stars, including bright ones like Sirius, Betelgeuse, and Rigel, can be seen.
• Some red giants like Betelgeuse (in Orion) and Aldebaran (in Taurus) are visible.
• Red Supergiants- Betelgeuse and Artates (in Scorpius) are examples that are visible.
• Rare supernovae can be bright, such as SN 1054, which created the Crab Nebula.
• Not Visible to the Naked Eye:
• Planetary and stellar nebulae
• protostars
• Neutron stars
• black holes

Hubble and Webb Observations

• The NASA's Hubble and Webb Space Telescopes offer us very different images of celestial bodies
• NGC 346, and the Pillars of Creation are example observations.