PSCI 131 Light Telescopes The Sun Light Telescopes

PSCI 131: Light, Telescopes, & The Sun Light, Telescopes, & the Sun Part Two • Optical Telescopes • Radio and Orbiting Telescopes • The Structure of the Sun

PSCI 131: Light, Telescopes, & The Sun Optical Telescopes

PSCI 131: Light, Telescopes, & The Sun Optical Telescopes • Gather visible light wavelengths • Concentrate it at a focal point, creating magnified image • Two types – Refracting – Reflecting

PSCI 131: Light, Telescopes, & The Sun Optical Telescopes: Refracting • Uses a lens (called the objective) to bend (refract) the light to produce an image • Light converges at an area called the focus • The eyepiece is a second lens used to examine the image directly – The size of the image produced by a lens is proportional to the focal length of the lens.

PSCI 131: Light, Telescopes, & The Sun Optical Telescopes: Refracting • Advantages – Inexpensive – Lens doesn’t have to be perfect to make a decent image • Drawbacks – Chromatic aberration: “halo” of color around image caused by refracted light – Chromatic aberration reduces image quality – If lens are too large, their weight will deform them and cause image distortion – limit to maximum telescope size

PSCI 131: Light, Telescopes, & The Sun Optical Telescopes: Reflecting • Uses a concave mirror to gather the light – Can be supported from the back because mirrors can be made thinner than lenses of similar size • No color distortion • Nearly all large telescopes are of this type

PSCI 131: Light, Telescopes, & The Sun Optical Telescopes: Reflecting • The primary mirror collects the light • The larger the primary mirror, the greater the light-collecting capacity. • Light gathered by the primary mirror is reflected to a secondary mirror. • The secondary mirror reflects the light to the focus, where the eye or instrument can observe it.

PSCI 131: Light, Telescopes, & The Sun Optical Telescopes: Reflecting • Advantages – No chromatic aberration – Can be very large, so higher magnification • Drawbacks – More expensive – Tiny flaws in mirror can greatly reduce image quality

PSCI 131: Light, Telescopes, & The Sun Large Telescopes • Larger light-gathering area – Total area of lens or mirror that gathers the light – Collect more photons of light, so can see fainter objects • Better resolution: sharper and more detailed images • Turbulence: the blurring and twinkling of astronomic objects such as stars caused by the movement of air in Earth’s atmosphere. – Observatories built on mountain summits to limit turbulence

PSCI 131: Light, Telescopes, & The Sun Resolution – 2 telescopes

PSCI 131: Light, Telescopes, & The Sun Technologies • Photographic films are used to detect ultraviolet and infrared wavelengths – Not distorted by human bias – Can expose for hours, recording more photons • CCDs (charge-coupled devices) – Large cameras that can collect almost all photons that strikes the chip • Greatly increases exposure time

PSCI 131: Light, Telescopes, & The Sun Technologies • Active optics: Motors drive telescope to compensate for distortions – Twin Keck Observatory telescopes in Hawaii use these • Arrays of telescopes (Interferometer) – Connecting telescopes into an array increases their resolution even more than their lightgathering area.

PSCI 131: Light, Telescopes, & The Sun Technologies • Even when located on mountain tops, advanced telescopes still face distorting effects of atmospheric turbulence. • Adaptive optics: Computer controlled mirrors cancel out atmospheric turbulence

PSCI 131: Light, Telescopes, & The Sun Radio- & Space-Based Telescopes

PSCI 131: Light, Telescopes, & The Sun Radio Telescopes • Gather radio waves from space – Pulsars, Quasars, Black holes • Collecting dish must be very large – Radio waves are about 100, 000 times longer than visible radiation – These signals are extremely faint • Can be networked into an array – Improves poor resolution

PSCI 131: Light, Telescopes, & The Sun Radio Telescopes • Advantages of radio telescopes – Less affected by weather – Less expensive – Can be used 24 hours a day – Detects material that does not emit visible radiation – Can “see” through interstellar dust clouds

PSCI 131: Light, Telescopes, & The Sun Orbiting Telescopes • Detect all forms of light – Atmosphere blocks much of EM spectrum • Radiation shorter than longest UV waves blocked • Water vapor in lower atmosphere absorbs most IR • No light pollution – Ex. The Hubble Space Telescope *

Space Observatories • Infrared – Cool stars, exoplanets, cool dust and gas of universe • Ultraviolet – Interstellar dust and gas clouds and hot young stars • X-ray – Black holes, quasars, high-temp gases – Chandra X-ray Observatory measured age of universe – 13. 8 billion years

PSCI 131: Light, Telescopes, & The Sun The Hubble Space Telescope • One of most important instruments in history of astronomy • Important discoveries: – Disks of dust are common around young stars • Supports nebular theory – Massive black holes exist at center of many large galaxies – Has allowed us to look further out (further back in time)

PSCI 131: Light, Telescopes, & The Sun Our Star: The Sun

PSCI 131: Light, Telescopes, & The Sun’s Composition • One of 200 billion stars that make up the Milky Way Galaxy • Only star close enough to allow the surface features to be studied • An average star in universe, but huge in our solar system – 100 x Earth’s diameter – 1. 25 million x Earth’s volume • Composition – Gaseous (90% Hydrogen, 10% Helium, others <1%) – Density: slightly greater than water (1/4 of Earth’s)

PSCI 131: Light, Telescopes, & The Sun’s Structure

How often do sunspots occur? Is there a correlation with magnetic storms on earth?

PSCI 131: Light, Telescopes, & The Sun Photosphere - Surface • “Sphere of light” • Sun’s “surface”—actually a layer of incandescent gas less than 500 kilometers thick • Grainy texture made up of many small, bright markings, called granules, produced by convection • Most of the elements found on Earth also occur on the Sun • Temperature averages approximately 6000 K (10, 000°F)

PSCI 131: Light, Telescopes, & The Sun Photosphere: closeup view *

PSCI 131: Light, Telescopes, & The Sun Chromosphere - Atmosphere • Just above photosphere • Lowermost atmosphere • Relatively thin, hot layer of incandescent gases a few thousand kilometers thick • Top contains numerous spicules—narrow jets of rising material

PSCI 131: Light, Telescopes, & The Sun Chromosphere From: astroguyz. com

PSCI 131: Light, Telescopes, & The Sun Corona - Atmosphere • Outermost portion of the solar atmosphere • Very tenuous • Ionized gases escape from the outer fringe and produce the solar wind • Temperature at the top exceeds 1 million K • Solar wind and Sun’s magnetic field make bubble called the heliosphere that extends past Pluto

PSCI 131: Light, Telescopes, & The Sun Corona (total solar eclipse)

PSCI 131: Light, Telescopes, & The Sun’s Interior • Cannot be observed directly • Sound waves are emitted, showing three distinct layers – Core: Region where Sun’s energy is radiated – Radiation zone: Above the core, dense zone where radiation is absorbed and re-emitted – Convection zone: Between radiation zone and photosphere, convection transports energy outward

PSCI 131: Light, Telescopes, & The Sun Source of Solar Energy • Nuclear fusion within core • Proton–proton reaction – Nuclear reaction that produces the Sun’s energy – Four hydrogen nuclei are converted into a helium nuclei – Matter is converted to energy – 600 million tons of hydrogen is consumed each second – Sun has enough fuel to last another five billion years

PSCI 131: Light, Telescopes, & The Sun The Active Sun

PSCI 131: Light, Telescopes, & The Sun Solar Energy • Most energy that reaches Earth results from steady, continuous emission of radiation from photosphere • Solar storms – irregular solar activity – Sunspots – Prominences – Solar flares – Coronal mass ejections

PSCI 131: Light, Telescopes, & The Sunspots • On the solar surface • Dark center, the umbra, surrounded by a lighter region, the penumbra • Dark color is due to a cooler temperature (1500 K less than the solar surface) • Follow an 11 -year cycle • Governed by Sun’s magnetic field • Pairs have opposite magnetic poles

PSCI 131: Light, Telescopes, & The Sunspots

PSCI 131: Light, Telescopes, & The Sun Prominences • Huge arching cloudlike structures that extend into the corona • Condensations of material in the corona

PSCI 131: Light, Telescopes, & The Sun Solar flares and CMEs • Solar flares – Explosive events that normally last an hour or so – Sudden brightening above a sunspot cluster – Release enormous quantities of energy • Coronal mass ejections – Eject particles that reach Earth in about one day and creates a magnetic storm that can affect radio transmissions – Causes auroras (the Northern and Southern Lights)

CMEs and Northern Lights

End of Light & The Sun Chapter