The heart of a vast cluster of galaxies called MACSJ1720+35 is shown in this image, taken in visible and near-infrared light by the NASA/ESA Hubble Space Telescope. The galaxy cluster is so massive that its gravity distorts, brightens, and magnifies light from more distant objects behind it, an effect called gravitational lensing. In the top right an exploding star nicknamed Caracalla and located behind the cluster can just be made out. The supernova is a member of a special class of exploding star called Type Ia, prized by astronomers because it provides a consistent level of peak brightness that makes it reliable for making distance estimates. Finding a gravitationally lensed Type Ia supernova gives astronomers a unique opportunity to check the optical "prescription" of the foreground lensing cluster. The supernova is one of three exploding stars discovered in the Cluster Lensing And Supernova survey with Hubble (CLASH), and was followed up as part of a Supernova Cosmology Project HST program. CLASH is a Hubble census that probed the distribution of dark matter in 25 galaxy clusters. Dark matter cannot be seen directly but is believed to make up most of the universe's matter. The image of the galaxy cluster was taken between March and July 2012 by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. Credit:
NASA, ESA, and J. Lotz (STScI)
Het begrip Universum lijkt allesomvattend – letterlijk alles omvattend. Maar bij nader inzien kan je er toch anders tegen aan kijken. Alles wat zich vroeger heeft afgespeeld en alles wat nog voor ons in de toekomst ligt, behoort dat ook allemaal tot het universum? Alles wat we niet weten en nooit te weten zullen komen, hoort dat er ook bij? Alles buiten het waarneembare heelal, hoort dat er ook bij? Afijn, neem even de tijd om naar deze korte, maar o zo boeiende video van MinutePhysics te kijken, handelend over de vraag ‘wat is het universum?‘
