Survey of the Universe Tom Burbine

Quiz #3 Wednesday Covers up to last Wednesday

Atmosphere Atmosphere can absorb light Atmosphere can scatter light Atmosphere can distort light (twinkling) (atmospheric scintillation)

Twinkling Twinkling of stars is caused by moving air currents in the atmosphere. The beam of light from a star passes through many regions of moving air while on its way to an observer’s eye or telescope. Each atmospheric region distorts the light slightly for a fraction of a second.

Advantages of space-based telescopes It can be open 24 hours, 7 days of week Do not have to worry about distorting effects of atmosphere There is no extra background of light due to scattering of light in the Earth’s atmosphere Observe in more wavelength regions

Figure 7.20

It does not help That you are closer to the stars

Great Observatories The Hubble Space Telescope (HST) observes visible, infrared, and near-ultraviolet light. Launched in 1990 The Compton Gamma Ray Observatory (CGRO) observes gamma and x-rays. Launched in Deorbited in 2000 into the Pacific Ocean The Chandra X-ray Observatory (CXO) observes x-rays. Launched in 1999 The Spitzer Space Telescope (SST) observes in the infrared. Launched in 2003.

Hubble (launched in 1990) Telescope is the size of a school bus 2.4 m mirror

Initially Hubble’s primary mirror was polished to the wrong shape Was too flat at the edges Was barely 2.3 micrometers out from the required shape (1/50 the width of a human hair) Images were not focused as well as they could be Later shuttle mission fixed this problem by installing a number of small mirrors

Jupiter taken by Hubble

Compton Gamma Ray Observatory Launched in 1991 Mapped the gamma rays distribution in the sky Dominated by emission from interactions between cosmic rays and the interstellar gas along the plane of our Galaxy

Chandra X-ray Observatory Launched in 1999 Observed X-rays X-rays can be associated with gas that is spiraling into black holes M81

Spitzer Space Telescope Infrared observatory Launched in 2003 Andromeda Galaxy in the infrared. Seeing dust

Sun Our nearest star Mean diameter ×10 6 km 109 × radius of Earth Mass ×10 30 kg 333,000 × Mass of Earth Made out of plasma – temperatures are so high that atoms are ionized

Figure 15.4

Temperature Density

Parts of Sun Core Core – ~15 million Kelvin – where fusion of Hydrogen to Helium occurs

Figure 15.4

Radiation zone Radiation zone – region where energy is transported primarily by radiative diffusion Radiative diffusion is the slow, outward migration of photons

Figure 15.13

Photons emitted from Fusion reactions Photons are originally gamma rays Tend to lose energy as they bounce around Photons emitted by surface tend to be visible photons Takes about a million years for the energy produced by fusion to reach the surface

Figure 15.4

Convection Zone Temperature is about 2 million Kelvin Photons tend to be absorbed by the solar plasma Plasma is a gas of ions and electrons Hotter plasma tends to rise Cooler plasma tends to sink

Figure 15.14

Granulation – bubbling pattern due to convection bright – hot gas, dark – cool gas Figure 15.14

Figure 15.10

Figure 15.4

Photosphere Photosphere is the solar surface Where photons escape into space Temperature of ~5,800 K

Chromosphere Thin layer of the Sun's atmosphere just above the photosphere Temperatures of 4500 K to as high as 20,000 K Most of the Sun’s ultraviolet light is emitted from this region

Corona Plasma "atmosphere" of the Sun,extending millions of kilometers into space Most easily seen during a solar eclipse Temperature of 1 to 3 million Kelvin

Solar Wind Solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun

Converting Mass to Energy What is the most famous formula in the world?

E = mc 2 m is mass in kilograms c is speed of light in meters/s So E is in joules very small amounts of mass may be converted into a very large amount of energy and

Who came up with it?

How much energy can be produced if you can convert 10 kg of material completely into energy? E = mc 2 A) 3.0 x 10 8 J B) 3.0 x J C) 9.0 x J D) 9.0 x J

Answer E = 10 kg * (3 x 10 8 m/s) * (3 x 10 8 m/s) E = 10* (9 x ) J E = 90 x J E = 9.0 x J

Mass-Energy E=mc 2 So Mass is a form of potential energy Where is one place where you see mass converted into energy?

Energy Source for Sun Fusing hydrogen into helium –Hydrogen nucleus – 1 proton –Helium nucleus – 2 protons, 2 neutrons Need high temperatures for this to occur ~10 to 14 million degrees Kelvin

Law Law of Conservation of mass and energy –Sum of all mass and energy (converted into the same units) must always remain constant during any physical process

observe.arc.nasa.gov/nasa/exhibits/stars/star_6.html

Any Questions?