Telescopes and Constellations

Telescope

• Galileo Galilei was a famous astronomer who constructed a modern telescope in the 1600s.
• Telescopes collect more light than the human eye can detect.

Early Astronomers

• Ptolemy, a Greek astronomer from the 2nd century, identified dozens of star patterns.

Constellations

• Constellations are groups of stars forming particular shapes in the sky, often named after their apparent form or mythological figures.
• There are 88 constellations.
• 12 are from the western tradition.
• The constellations you see depend on your location, date, and time.
• Most constellations have legends, myths, or stories behind them.
• Examples of constellations include:
  • Orion, a hunter in Greek mythology, is visible during winter in the northern celestial hemisphere.
  • Scorpion constellation is typically visible during the summer months in the Northern Hemisphere.
  • Big Dipper (Ursa Major) including the "pointers" Dubhe and Merak.
  • Little Dipper (Ursa Minor)

Spectroscope

• Spectroscopes (Stellar Spectroscopes) spread light into different wavelengths to analyze the:
  • Temperature
  • Composition
  • Energies of Stars

Electromagnetic Spectrum

• Visible light is one part of the electromagnetic spectrum.
• Newly formed stars emit mostly radio and infrared waves, which have low energy.
• Exploding stars emit mostly high-energy ultraviolet waves and X-rays.

Measuring Distances

• Astronomers use angles created by parallax to measure how far objects are from Earth.
• Parallax is the apparent change in an object's position caused by looking at it from two different points.
• Astronomical Unit: The average distance between Earth and Sun, about 150 million km (Within the Solar System).
• Light-Year: The distance light travels at a rate of about 300,000 km/s (Beyond the Solar System).
  • 1 light-year is equivalent to 10 trillion km.
  • Proxima is 4.2 light years away.
  • Almost 4 days equals 1 second light year

Apparent and Absolute Magnitude

• Apparent Magnitude: Measures how bright an object appears from Earth.
• Absolute Magnitude measures luminosity as the true brightness of an object.
  • Luminosity depends on a star’s temperature and size, not its distance from Earth.
  • M87 Galaxy is measured at -22.
  • Brightest known stars measure at -10.
  • Sirius measures 1.4 and The Sun measures 4.83
  • Ross 258 is measured at 14.8