Notes 13 – Tools and Classification of Stars Mrs. Gordon Earth Science Friday, October 23, 2015Friday, October 23, 2015Friday, October 23, 2015Friday, October 23, 2015

HaHa Funny! Sort of… Star light, star bright Star light, star bright First star I see tonight First star I see tonight I wish I may, I wish I might. I wish I may, I wish I might. Oh, It's just a satellite…. Oh, It's just a satellite….

1. Tools of Today A. Electromagnetic Spectrum – energy that travels in waves A. Electromagnetic Spectrum – energy that travels in waves Different wavelengths help determine the composition of objects in space. (what they are made of, how hot they are) Different wavelengths help determine the composition of objects in space. (what they are made of, how hot they are)

B. Telescopes (or light buckets) OPTICAL telescopes are the most common, however there are also radio, infrared, UV and other high- energy telescopes. OPTICAL telescopes are the most common, however there are also radio, infrared, UV and other high- energy telescopes. Refracting – uses lenses Refracting – uses lenses Reflecting - uses mirrors Reflecting - uses mirrors

Why Reflectors are preferred over Refractors: Chromatic aberration – light must pass through a lens, it is difficult to make the glass completely uniform Chromatic aberration – light must pass through a lens, it is difficult to make the glass completely uniform Glass absorbs some radiation (infrared, UV) Glass absorbs some radiation (infrared, UV) Large lenses can be quite heavy, and can only be supported around the edges so the glass can deform under its own weight, mirrors can be supported on one whole side. Large lenses can be quite heavy, and can only be supported around the edges so the glass can deform under its own weight, mirrors can be supported on one whole side. A lens has TWO sides that need to be cared for, a mirror only has one A lens has TWO sides that need to be cared for, a mirror only has one

C. Hubble Space Telescope World's first space-based optical telescope World's first space-based optical telescope Launched in 1990, orbits Earth about once every 95 minutes at an altitude of about 350 miles. Launched in 1990, orbits Earth about once every 95 minutes at an altitude of about 350 miles. The most expensive scientific instrument ever constructed… Cost ~ $2 Billion The most expensive scientific instrument ever constructed… Cost ~ $2 Billion Hubble transmits about 120 gigabytes of science data every week. That's equal to about 3,600 feet of books on a shelf. The rapidly growing collection of pictures and data is stored on magneto-optical disks. Hubble transmits about 120 gigabytes of science data every week. That's equal to about 3,600 feet of books on a shelf. The rapidly growing collection of pictures and data is stored on magneto-optical disks. Hubblesite.org Hubblesite.org Hubblesite.org

D. Observatories Contain telescopes on the ground Contain telescopes on the ground Usually located on high mountain tops, away from cities. Usually located on high mountain tops, away from cities. Mauna Kea Mauna Kea

Other cool Telescopes Arecibo Radio Telescope, Arecibo Radio Telescope, Puerto Rico Puerto Rico Very Large Very LargeArray, New Mexico

2. Classifying Stars A. Astronomers classify stars by: A. Astronomers classify stars by: color color temperature temperature size size brightness (and this depends on temp. and size) brightness (and this depends on temp. and size) B. Apparent magnitude - how bright a star looks from Earth. This depends on how far away it is AND how bright the star actually is (luminosity) B. Apparent magnitude - how bright a star looks from Earth. This depends on how far away it is AND how bright the star actually is (luminosity) C. Absolute magnitude – how bright a star really is at a standard distance from Earth C. Absolute magnitude – how bright a star really is at a standard distance from Earth

D. H-R Diagram Charts stars by temperature and absolute magnitude. Charts stars by temperature and absolute magnitude. Used to: Used to: classify stars classify stars understand how understand how stars change over time Main Sequence - 90% of all stars Main Sequence - 90% of all stars Super Giants – large, cool, bright Super Giants – large, cool, bright Red Giants – large, cooler, medium brightness Red Giants – large, cooler, medium brightness White dwarfs – small, hot, dim White dwarfs – small, hot, dim Hertzsprung-Russell Diagram interactive Hertzsprung-Russell Diagram interactive

Our star – the Sun – is an average star on the main sequence. Our star – the Sun – is an average star on the main sequence. Betelgeuse is listed as the brightest star in the constellation of Orion. Betelgeuse's reddish hue is due to it being a well- developed red giant star. Betelgeuse is listed as the brightest star in the constellation of Orion. Betelgeuse's reddish hue is due to it being a well- developed red giant star. The star's outer layers have expanded to such a degree that if it were where the Sun is, Earth would actually be inside it. When Betelgeuse finally uses up all its hydrogen fuel, the outer layers will be cast out from the main star which will then explode as a supernova. This event could happen any time in the next million years or so. The star's outer layers have expanded to such a degree that if it were where the Sun is, Earth would actually be inside it. When Betelgeuse finally uses up all its hydrogen fuel, the outer layers will be cast out from the main star which will then explode as a supernova. This event could happen any time in the next million years or so. In this ultraviolet image of the Sun, a prominence arcs thousands of miles above the solar surface and white patches reveal magneticallly acive regions. The Solar and Heliospheric Observatory, SOHO, returned this image in It's one of many spacecraft dedicated to monitoring our star. NASA / SOHO In this ultraviolet image of the Sun, a prominence arcs thousands of miles above the solar surface and white patches reveal magneticallly acive regions. The Solar and Heliospheric Observatory, SOHO, returned this image in It's one of many spacecraft dedicated to monitoring our star. NASA / SOHO