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Part I: A Trip Through the Universe

“Our Transportation”

STARS AND GALAXIES

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What do you see when you look up at the sky on a clear night?

The night sky at ESO's La Silla Observatory in Chile

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What might appear different if you were to use a telescope?

Globular cluster Messier 10 seen here in an image from the NASA/ESA

Hubble Space Telescope

Four Faces of Mars photographed by the Hubble Space Telescope

Credit: S. Lee (U. Colorado) et al., WFPC2, HST, NASA

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• 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.

TELESCOPES

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TYPES OF TELESCOPES

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• 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?

REFRACTING TELESCOPE

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• 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

REFLECTING TELESCOPES

100” Hooker Telescope on Mt. Wilsonin CA; used by Edwin Hubble to

discover the existence of galaxiesother than the Milky Way

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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.

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• 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.

MULTIPLE MIRROR REFLECTING TELESCOPES

Aerial view of Keck I and Keck II Observatories

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• 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.

ELECTROMAGNETIC SPECTRUM – LIGHT WAVES

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• 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?

THE SPECTROSCOPE

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• 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.

THE SPECTROSCOPE

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.

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– collect radio waves and use them to produce an image

RADIO TELESCOPES

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.

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• Detect low energy light from objects that are normally hidden by dust clouds

• May be land-based or in space.

INFRARED TELESCOPES

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

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Generally must be placed above the atmosphere to be effective, as much UV light is blocked by the Earth’s atmosphere

ULTRAVIOLET TELESCOPES

The Galaxy Evolution Explorer (GALEX) is an orbiting space

telescope observing galaxies in ultraviolet light

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• 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.

X-RAY TELESCOPES

FYI: The Chandra X-ray Observatory was launched in 1999. It orbits the Earth 200 times higher than Hubble.

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• 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

GAMMA RAY TELESCOPES

Compton Gamma Ray ObservatoryUsed from 1991 - 2000

• 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

THE HUBBLE TELESCOPE

PICTURES FROM HUBBLE

Butterfly Nebula

Cat’s Eye Nebula

Dusty Spiral Galaxy

Two Colliding Spiral Galaxies

HST NGC 6751 Aquilla Nebula

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ONE VIEW THROUGH 4 TELESCOPES

Crab Nebula in different wavelengths. Image from NASA.