Three Steps to the Hubble Constant
NASA, ESA, and A. Feild (STScI) · Download full size image
Hubble measurements have simplified the cosmic "distance ladder," which is needed to calculate a more precise value for the universe's expansion rate, called the Hubble constant. At select host galaxies, Cepheid variable stars — known as reliable milepost markers — are cross-calibrated to Type Ia supernovae in the same host galaxy. The new technique reduced the distance ladder to three "rungs": (1) The distance to galaxy NGC 4258 is measured using straightforward geometry and Kepler's laws; (2) Cepheids in six more distant galaxies are used to calibrate the luminosity of Type Ia supernovae; (3) The Hubble constant is measured by observing a brighter milepost marker, Type Ia supernovae, in more distant galaxies hundreds of millions of light-years away, embedded in the expanding universe.
Posted on: 12 May, 2009
- Hubble Space Telescope
- Chandra X-ray Observatory
- Compton Gamma-Ray Observatory
- ROSAT X-ray Observatory
- SOHO Solar Observatory
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- NRAO Gallery
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- Galaxy Evolution Explorer (GALEX)
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- Wide-Field Imager (WFI)
- SOFI Infrared Multi-mode Instrument
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- New Technology Telescope (NTT)
- Atacama Pathfinder Experiment (APEX)
- SOHO Daily Images - 1996
- Spitzer Space Telescope (SIRTF)
- Infrared Legacy Gallery
- Herschel
- Advanced Technology Solar Telescope
- Planck
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