Hubble image archive
Three Steps to the Hubble Constant
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-cali...
- Date
- Jan 1, 2009
- Mission
- Hubble Space Telescope
- Archive ID
- hubblesite-images-2009-08-2494-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.
Credits
NASA, ESA, and A. Feild (STScI)More Images From This Period
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Source
Image and source material are credited to the official mission archive linked below.
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