Stars and galaxies

1. Stars and galaxies Part I: A Trip Through the Universe “Our Transportation”

2. What do you see when you look up at the sky on a clear night? The night sky at ESO's La SillaObservatory in Chile

3. What might appear different if you were to use a telescope? Four Faces of Mars photographed by the Hubble Space TelescopeCredit: S. Lee (U. Colorado) et al., WFPC2, HST, NASA Globular cluster Messier 10 seen here in an image from the NASA/ESA Hubble Space Telescope

4. Telescopes • Unlike a microscope whose function is to magnify small objects, when looking at the stars, magnification is not very important. No matter how much you magnify them they still look like points of light. • Telescopes are built to collect light. They allow scientists to examine objects that are too dim or too far away to see unaided.

5. Types of Telescopes

6. Refracting Telescope • Uses a series of lenses to focus visible light • Limited by how large lenses can be made FYI: The largest is the 40-inch Yerkes telescope, built in 1895 in Wisconsin (40 inch lens in a sixty-foot long telescope) Pictured right – can you spot the famous scientist in the picture?

7. Reflecting Telescopes • A series of mirrors is used to collect and focus light • Images are captured by cameras (now replaced by newer technology that works with computers); long exposures allow objects too dim to see with our eyes to be “seen.” • Usually built atop mountains to reduce atmospheric interference FYI: Largest is the 200” Hale telescope on Mt. Palomar in CA 100” Hooker Telescope on Mt. Wilson in CA; used by Edwin Hubble to discover the existence of galaxies other than the Milky Way

8. Reflecting Telescopes FYI: Until the late 20th century, just like refracting telescopes, the size of reflecting telescopes was limited by how big a mirror could be made before it would distort itself under its own weight. Scientists developed two solutions to this problem. They developed a new way to make very large mirrors (6-8+ meters in diameter) and a way to combine multiple mirrors that work together as one.

9. Multiple Mirror Reflecting Telescopes • Use multiple mirrors that act together as a much large mirror • The Keck telescopes on Mauna Kea (a dormant volcano) in Hawaii are two telescopes, each with 36 mirrors that make a 400” mirror. Aerial view of Keck I and Keck II Observatories

10. Electromagnetic Spectrum – Light Waves • Energy travels through space in the form of waves. • The shorter the wavelength the higher the amount of energy. • All electromagnetic waves travel at the same speed (~300,000km/s or 186,000 mi/s) • Visible light is only a small portion of the EM spectrum.

11. The Spectroscope • An instrument used with a visible light telescope to separate the visible light from individual stars into its component colors • The spectrum of a star can tell a scientist how hot a star is. Bluer stars are hotter than redder stars. Why?

12. The Spectroscope • The spectrum of a star also tells us the composition of a star (the elements it is made of.) • The black lines in the spectrum are absorption lines, and they can be used to determine composition of the star. Spectrum of a star. Graph of spectral luminosity versus wavelength. Later we will see that the spectrum of a star can also be used to determine how far away from Earth it is.

13. Radio Telescopes – collect radio waves and use them to produce an image FYI: The Very Large Array, one of the world's premier astronomical radio observatories, consists of 27 radio antennas in a Y-shaped configuration on the Plains of San Agustin fifty miles west of Socorro, New Mexico.

14. Infrared Telescopes • Detect low energy light from objects that are normally hidden by dust clouds • May be land-based or in space. The IRTF is NASA’s 3.0 meter telescope, optimized for infrared observations, and located at the summit of Mauna Kea, Hawai`i. Spitzer Infrared Space Telescope Launched 2003

15. Ultraviolet Telescopes Generally must be placed above the atmosphere to be effective, as much UV light is blocked by the Earth’s atmosphere The Galaxy Evolution Explorer (GALEX) is an orbiting space telescope observing galaxies in ultraviolet light

16. X-Ray Telescopes • Must be above the atmosphere as X-rays from space do not pass through the atmosphere • Use special reflectors to focus X-rays and produce an image • The first X-ray telescopes were used to observe the sun. FYI: The Chandra X-ray Observatory was launched in 1999. It orbits the Earth 200 times higher than Hubble.

17. Gamma Ray Telescopes • Gamma rays are very high energy light rays and scientists have developed technology to detect and image gamma radiation from space • Must be above the atmosphere to detect • Certain cosmic events radiate large amounts of gamma rays Compton Gamma Ray Observatory Used from 1991 - 2000

18. The Hubble Telescope • Named after Edwin Hubble • Launched in 1990 and repaired/upgraded by astronauts since then • A reflecting telescope designed to detect light in the infrared, visible, and ultraviolet light ranges without distortion caused by the atmosphere • Has greatly increased our knowledge of distant galaxies and the universe

19. Pictures from Hubble Dusty Spiral Galaxy HST NGC 6751 Aquilla Nebula Butterfly Nebula Cat’s Eye Nebula Two Colliding Spiral Galaxies

20. One View Through 4 Telescopes Crab Nebula in different wavelengths. Image from NASA.