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File:NGC 5584 (captured by the Hubble Space Telescope).jpg

原始文件 （3,539 × 4,016像素，文件大小：19 MB，MIME类型：image/jpeg）

描述

The brilliant, blue glow of young stars trace the graceful spiral arms of galaxy NGC 5584 in this Hubble Space Telescope image. Thin, dark dust lanes appear to be flowing from the yellowish core, where older stars reside. The reddish dots sprinkled throughout the image are largely background galaxies.

Among the galaxy's myriad stars are pulsating stars called Cepheid variables and one recent Type Ia supernova, a special class of exploding stars. Astronomers use Cepheid variables and Type Ia supernovae as reliable distance markers to measure the universe's expansion rate. NGC 5584 was one of eight galaxies astronomers studied to measure the universe's expansion rate. In those galaxies, astronomers analyzed more than 600 Cepheid variables, including 250 in NGC 5584.

Cepheid variables pulsate at a rate matched closely by their intrinsic brightness, making them ideal for measuring distances to relatively nearby galaxies. Type Ia supernovae flare with the same brightness and are brilliant enough to be seen from relatively longer distances.

Astronomers search for Type Ia supernovae in nearby galaxies containing Cepheid variables so they can compare true brightness of both types of stars. They then use that information to calibrate the measurement of Type Ia supernovae in far-flung galaxies and calculate their distance from Earth. Once astronomers know accurate distances to galaxies near and far, they can determine the universe's expansion rate.

The image is a composite of several exposures taken in visible light between January and April 2010 with Hubble's Wide Field Camera 3.

NGC 5584 resides 72 million light-years away in the constellation Virgo.
日期 在2010年1月到2010年4月之间
date QS:P,+2010-00-00T00:00:00Z/9,P1319,+2010-01-00T00:00:00Z/10,P1326,+2010-04-00T00:00:00Z/10
来源 http://hubblesite.org/newscenter/archive/releases/2011/08/image/a/ (direct link)
作者 NASA, ESA, A. Riess (STScI/JHU), L. Macri (Texas A&M University), and Hubble Heritage Team (STScI/AURA)
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Public domain
This file is in the public domain because it was created by NASA and ESA. NASA Hubble material (and ESA Hubble material prior to 2009) is copyright-free and may be freely used as in the public domain without fee, on the condition that only NASA, STScI, and/or ESA is credited as the source of the material. This license does not apply if ESA material created after 2008 or source material from other organizations is in use.

The material was created for NASA by Space Telescope Science Institute under Contract NAS5-26555, or for ESA by the Hubble European Space Agency Information Centre. Copyright statement at hubblesite.org or 2008 copyright statement at spacetelescope.org.

For material created by the European Space Agency on the spacetelescope.org site since 2009, use the {{ESA-Hubble}} tag.

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