File:Spiral Galaxy NGC 4639 (1996-21-425).jpg
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This Hubble Space Telescope image shows NGC 4639, a spiral galaxy located 78 million light-years away in the Virgo cluster of galaxies. The blue dots in the galaxy's outlying regions indicate the presence of young stars.
Summary
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English: This Hubble Space Telescope image shows NGC 4639, a spiral galaxy located 78 million light-years away in the Virgo cluster of galaxies. The blue dots in the galaxy's outlying regions indicate the presence of young stars. Among them are older, bright stars called Cepheids, which are used as reliable milepost markers to obtain accurate distances to nearby galaxies. Astronomers measure the brightness of Cepheids to calculate the distance to a galaxy. Allan Sandage's team used Cepheids to measure the distance to NGC 4639, the farthest galaxy to which Cepheid distance has been calculated. After using Cepheids to calculate the distance to NGC 4639, the team compared the results to the peak brightness measurements of SN 1990N, a type Ia supernova located in the galaxy. Then they compared those numbers with the peak brightness of supernovae similarly calibrated in nearby galaxies. The team then determined that type Ia supernovae are reliable secondary distance markers, and can be used to determine distances to galaxies several hundred times farther away than Cepheids. An accurate value for the Hubble Constant depends on Cepheids and secondary distance methods. The color image was made from separate exposures taken in the visible and near-infrared regions of the spectrum with the Wide Field Planetary Camera 2. |
| Date | 9 May 1996 (upload date) |
| Source | Spiral Galaxy NGC 4639 |
| Author | A. Sandage (Carnegie Observatories), A. Saha (Space Telescope Science Institute), G.A. Tammann, and L. Labhardt (Astronomical Institute, University of Basel), F.D. Macchetto and N. Panagia (Space Telescope Science Institute and European Space Agency) and NASA |
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| Keywords | Variable Stars; Galaxies; Stars; Cosmology; Distant Galaxies; Spiral Galaxies |
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Licensing
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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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| current | 17:40, 15 June 2024 | | 2,065 × 2,561 (270 KB) | OptimusPrimeBot (talk | contribs) | #Spacemedia - Upload of https://stsci-opo.org/STScI-01EVTAP2B5MMC0BR80HV31605Q.jpg via Commons:Spacemedia |
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