Universe_Look

Universe_Look - What does the Universe look like? ASTR 2340...

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Unformatted text preview: What does the Universe look like? ASTR 2340 Spring 2010 Rupali Chandar Review Questions-- what is the basic physical principle that explains interstellar reddening, why the sky is blue, & why sunsets are red?-- what is the raw material out of which stars form? What conditions are needed for stars to form?-- describe the source of 21 cm radiation in astronomy-- What is galactic recycling?-- What is an HII region? What does it tell us if we see one? (This weeks lectures cover mostly Mystery 8 in the book ) The matter in our Galaxy emits different kinds of radiation, depending on what stage of the stargasstar cycle it is in. Looking into deep space = Looking back into time A Universe of Galaxies In 1995, the Hubble Space Telescope observed a patch of sky in the Big Dipper for 10 days. many galaxies, each one an island of stars like our own Milky Way, were detected by counting them and correcting for the entire sky, we estimate that there are over 100 billion galaxies in the observable Universe We study the life cycles of galaxies in the same way we do stars. we piece together a life story by observing many different galaxies at various stages of their lives Studying life cycles of galaxies is more difFcult than that of stars. young galaxies are only found at very great distances Hubble deep Field Movie. Click to play. Spiral Galaxies (like Milky Way) have a disk component and bulge & halo ( spheroidal component ) disk contains an ISM of gas & dust relative sizes of bulge/disk & amount of ISM vary among galaxies appear white because they contain both blue & red stars Spiral Galaxies Some spiral galaxies have a bar of stars cutting through their centers. spiral arms are attached to the ends of the bar we call them barred spiral galaxies Some astronomers have suggested that the Milky Way is a barred spiral. its bulge appears elongated Some galaxies have disks with no spiral arms. we call then lenticular galaxies they look like a lens seen edge-on They contain less cool gas than normal spirals. Elliptical Galaxies only have a spheroidal component; no disk component very little ISM, which is mostly low-density and ionized appear red (not in these pictures though) because they contain mostly red stars Irregular Galaxies none of the above category; neither spiral nor elliptical appear white & dusty with ISM have more in common with the disk component of spirals distant galaxies are more likely to be irregular they were more common when the Universe was young Groups and Clusters...
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This note was uploaded on 02/21/2011 for the course ASTR 2340 taught by Professor Rupalichandar during the Spring '10 term at Toledo.

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Universe_Look - What does the Universe look like? ASTR 2340...

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