Determining the expansion of the Universe through the Hubble constant

Feature article in Science, Vol. 355, Issue 6329, pp. 1010-1014, “Hubble Trouble”

Summary of article: Observations of distant stars and galaxies highlighted to astronomers that the universe is expanding through possibly the repulsive effect of dark energy; however, the rate of expansion of the universe as measured by the Hubble constant is still under heavy scrutiny and debate in the field. Specifically, multiple approaches from ground-based telescopes to the Hubble space telescope, and measurements of standard candles and the cosmic microwave background have combined to provide a differing view of the state of the universe, its size, and most importantly, the value of the Hubble constant. While early observations using ground-based telescopes provided an over-estimate of the Hubble constant, which placed the age of the universe at 2 billion years, rather than the currently known 13.8 billion years, progressive refinement of observations using better telescopes has brought the measured Hubble constant to closer agreement with those yielded by space observatories such as Hubble Space Telescope, Gaia and Planck satellites. Indeed the distance ladder approach for measuring Hubble constant has been typically taken to be the gold standard, as multiple assumptions in the astrophysics approach of listening to the cosmic microwave background is thought to be less reliable. Nevertheless, gravitational lensing observation of how star light from distant galaxies and stars are bent by a nearby galaxy cluster may provide a bridge between the two seemingly incongrous methods for cosmology.

Link to original article: http://science.sciencemag.org/content/355/6329/1010

Category: Interesting scientific articles, astronomy, space exploration,

Tags: standard candle, Hubble constant, cosmic microwave background, dark energy, repulsion, expanding universe, gravitational lensing, Planck, Gaia, Hubble Space Telescope,

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