HUbble looks at NGC 3021 to help narrow possible explanations for dark energy. Click for larger image (~61k). Image credit: NASA, ESA, and A. Riess (STScI/JHU)
The latest Hubble release explains how the refined Hubble constant narrows the possible explanations for dark energy.
For the long version at Hubblesite click the link below and to see the image above without the annotations click here, it’s very nice.
Just a couple days to go before Atlantis launches with the the “repair crew” for Hubble.
From Hubblesite:
This is a Hubble Space Telescope photo of the spiral galaxy NGC 3021. This was one of several hosts of recent Type Ia supernovae observed by astronomers to refine the measure of the universe’s expansion rate, called the Hubble constant. Hubble made precise measurements of Cepheid variable stars in the galaxy, highlighted by green circles in the four inset boxes. These stars pulsate at a rate that is matched closely to their intrinsic brightness. This makes them ideal for measuring intergalactic distances. The Cepheids are used to calibrate an even brighter milepost marker that can be used over greater distances, a Type Ia supernova. The supernova was observed in the galaxy in 1995. The images in the boxes were taken with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).
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