Lecture 16 - Measuring the Stars

Lecture 16 - Measuring the Stars - Measuring the Stars...

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Measuring the Stars ASTRONOMY 3 Lesson 16 1 A new born cluster of stars (NGC 3603) as observed with the ESO Very Large Telescope in the near-infrared. The cluster houses several 1,000s of stars with masses down to 0.1, and up to 100 times the mass of the Sun. See http://www.eso.org/outreach/press-rel/pr-1999/ pr-16-99.html
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NATURE of the Universe Review of Lesson 15 Astronomy - Measuring the Stars • Conduction , convection , and radiation are the 3 ways to transport heat (energy). • The Sun has a core, a radiative zone and a convective zone. The Sun’s structure can be studied by helioseismology, and the principle of hydrostatic equilibrium. • The Sun produces energy with the proton-proton chain in its core. 4 hydrogen nuclei (protons) fuse to 1 helium nucleus (2 protons, 2 neutrons). 2 positrons, 2 neutrinos and 2 gamma-ray photons are emitted. Review of Lesson 15: 2
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NATURE of the Universe Questions from Lesson 15 Astronomy - Measuring the Stars Think about (questions from Lesson 15): • Are all stars like the Sun? • How old do stars get? 3
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• Distances to nearby stars (Ch. 10.1) • Luminosity and apparent brightness (Ch. 10.2) • Temperature (Ch. 10.3) • Sizes and masses (Ch. 10.4, 10.6) • The Hertzsprung-Russell diagram (10.5) • Summary & Homework & Announcements NATURE of the Universe Today’s Topics Astronomy - Measuring the Stars see also Lab 6 on “Stars & the H-R diagram” 4
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NATURE of the Universe Distances Astronomy - Measuring the Stars The parallax p enables us to measure the distance to nearby stars. 5
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NATURE of the Universe Distances Astronomy - Measuring the Stars Stars closer to the Sun show a larger parallax than stars at larger distances. distance (in lightyears) = 3.3 / parallax (in arcseconds) Proxima Centauri (a member of the alpha Centauri triple system) has a parallax of 0.772 arcsec. This corresponds to a distance of 4.22 lightyears. 6
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NATURE of the Universe Distances Astronomy - Measuring the Stars Stars within 12.5 lightyears of the Sun. 7 The solar neighbourhood - stars within 12.5 lightyears of the Sun. Note that there are many more red (M-type) and orange (K-type) stars than there are yellow (G-type) and white (A- type) stars. - see http://www.atlasoftheuniverse.com/
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NATURE of the Universe Distances Astronomy - Measuring the Stars The triple star system Alpha Centauri is the closest neighbor to the Sun. Southern Cross Alpha Centauri 8 Image of a region of the southern Milky Way by Humayun Qureshi
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NATURE of the Universe Luminosity and apparent brightness Astronomy - Measuring the Stars The apparent brightness (or the energy received from a star) is inversely proportional to the square of its distance (see also Lab 6). star If two stars are identical , but at different distances, the star closer to us appears brighter than the more distant star . This is similar to traffic lights seen along a street. The light closer to us appears brighter.
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