|
|
Hubble Space Telescope Measu
…
| Title |
Hubble Space Telescope Measures Precise Distance to the Most Remote Galaxy Yet |
|
Hubble Space Telescope Measu
…
| Title |
Hubble Space Telescope Measures Precise Distance to the Most Remote Galaxy Yet |
|
M100: A Grand Design
| Title |
M100: A Grand Design |
| Explanation |
Majestic [ http://www.lhl.lib.mo.us/pubserv/hos/stars/welcome.htm ] on a truly cosmic scale, M100 [ http://bozo.lpl.arizona.edu/messier/m/m100.html ] is appropriately known as a Grand Design spiral [ http://antwrp.gsfc.nasa.gov/apod/ap961030.html ] galaxy. A large galaxy of over 100 billion or so stars with well defined spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap960409.html ], it is similar to our own Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap970315.html ]. One of the brightest members of the Virgo Cluster of galaxies [ http://bozo.lpl.arizona.edu/messier/more/virgo.html ] , M100 (alias NGC 4321) is 56 million light-years distant in the spring constellation of Coma Berenices [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Coma_Berenices.html ]. This Hubble Space Telescope image [ http://oposite.stsci.edu/pubinfo/PR/94/01.html ] of the central region of M100 was made in 1993 with the Wide Field and Planetary Camera 2. It reveals the bright blue star clusters [ http://antwrp.gsfc.nasa.gov/apod/ap980329.html ] and intricate winding dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ] which are hallmarks of this class of galaxies [ http://hermes.astro.washington.edu:80/scied/astro/hubble/hubble.html ]. Studies of stars in M100 [ http://antwrp.gsfc.nasa.gov/apod/ap960110.html ] have recently played an important role in determining the size and age [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/ debate_1996.html ] of the Universe. |
|
M100 and the Expanding Unive
…
| Title |
M100 and the Expanding Universe |
| Explanation |
The distance to the swirling grand design spiral [ http://antwrp.gsfc.nasa.gov/apod/ap951218.html ] M100 [ http://antwrp.gsfc.nasa.gov/apod/ap950626.html ] is causing quite a stir among astronomers. Many believe that the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ]'s recent distance measurement to this galaxy accurately calibrates the expansion rate [ http://www.ast.cam.ac.uk/RGO/leaflets/cosmology/cosmology.html ] of the universe [ http://antwrp.gsfc.nasa.gov/apod/ap951108.html ]. Others believe this distance measurement is misleading. The universe's expansion rate is usually given as a quantity called "Hubble's constant [ http://www.stsci.edu/pubinfo/background-text/hnought.txt ]", a factor dividing well-measured recession velocity of a galaxy to give actual distance. Scientific debate [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate.html ] over the value of Hubble's constant [ http://www.mathsoft.com/astronomy/hubble.html ] has been ongoing since it was first measured by Edwin Hubble [ http://spacelink.msfc.nasa.gov/Spacelink.Hot.Topics/Hubble.Space.Telescope/Edwin.Hubble/ ] in 1929. A real live debate involving the value of Hubble's constant titled "The Scale of the Universe [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate_1996.html ]" will occur in April 1996 in Washington, DC. |
|
The Cepheids of M100
| Title |
The Cepheids of M100 |
| Explanation |
Can this blinking star tell us how fast the universe is expanding? Many astronomers also believe it may also tell us the age of the universe! The photographed "Cepheid variable [ http://www.stsci.edu/pubinfo/gif/M100CphB.txt ]" star in M100 [ http://antwrp.gsfc.nasa.gov/apod/ap960109.html ] brightens and dims over the course of days as its atmosphere expands and contracts. A longer blinking cycle means an intrinsically brighter star. Cepheids variable stars are therefore used as distance indicators [ http://www.stsci.edu/pubinfo/background-text/cosmyard.txt ]. By noting exactly how long the blinking period is and exactly how bright the star appears to be, one can tell the distance to the star and hence the star's parent galaxy. This distance can then be used to match-up easily measured recessional velocity ("redshift") with distance. Once this "Hubble relation [ http://www.mathsoft.com/astronomy/hubble.html ]" is determined for M100 [ http://antwrp.gsfc.nasa.gov/apod/ap950626.html ], it should be the same for all galaxies - and hence tell us how fast the universe is expanding [ http://www.ast.cam.ac.uk/RGO/leaflets/cosmology/cosmology.html ]. The exact magnitude of this calibration is under dispute and so a real live debate involving the value of Hubble's constant [ http://www.stsci.edu/pubinfo/background-text/hnought.txt ] titled "The Scale of the Universe [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate_1996.html ]" will occur in April 1996 in Washington, DC. |
|
M100: A Grand Design
| Title |
M100: A Grand Design |
| Explanation |
Majestic [ http://www.lhl.lib.mo.us/pubserv/hos/stars/welcome.htm ] on a truly cosmic scale, M100 [ http://bozo.lpl.arizona.edu/messier/m/m100.html ] is appropriately known as a Grand Design spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap961030.html ]. A large galaxy of over 100 billion or so stars with well defined spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap960409.html ], it is similar to our own Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap970315.html ]. One of the brightest members of the Virgo Cluster of galaxies [ http://bozo.lpl.arizona.edu/messier/more/virgo.html ] , M100 (alias NGC 4321) is 56 million light-years distant in the spring constellation of Coma Berenices [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Coma_Berenices.html ]. This Hubble Space Telescope image [ http://oposite.stsci.edu/pubinfo/PR/94/01.html ] of the central region of M100 was made in 1993 with the Wide Field and Planetary Camera 2. It reveals the bright blue star clusters [ http://antwrp.gsfc.nasa.gov/apod/ap980329.html ] and intricate winding dust lanes [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ] which are hallmarks of this class of galaxies [ http://hermes.astro.washington.edu:80/scied/astro/hubble/hubble.html ]. Studies of stars in M100 [ http://antwrp.gsfc.nasa.gov/apod/ap960110.html ] have recently played an important role in determining the size and age of the Universe. |
|
|
