Dark energy changes over time

Dark energy is thought to be the reason why the universe continues to expand faster and faster, instead of contracting. Yet researchers still don’t have a well-founded theory on what exactly this mysterious form of energy is. If current theories of the universe are correct, dark energy must account for up to 72 percent of the total matter of the universe today.

But what about in the past? Current theory assumes that dark energy had little influence early on. So, the expansion of the universe must have changed significantly over time. Now, with the help of NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton, researchers have verified this hypothesis with a new method using quasars. Quasars, active galactic nuclei, are so far away from us that they are basically illuminating the past for us.

In their work, researchers measured 1,598 quasars. They quantified the UV and X-ray radiation of the objects and set this in relation to their distance. The result is a statement on the rate of expansion of the universe and it gives a result that had already been found using other methods: the effect of dark energy was significantly weaker many billions of years ago than today.

Schematic illustration of the research work (picture: NASA/CXC/Univ. of Florence/G.Risaliti & E.Lusso)

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  • BrandonQMorris
  • Brandon Q. Morris es físico y especialista en el espacio. Lleva mucho tiempo preocupado por las cuestiones espaciales, tanto a nivel profesional como privado, y aunque quería ser astronauta, tuvo que quedarse en la Tierra por diversas razones. Le fascina especialmente el "qué pasaría si" y a través de sus libros pretende compartir historias convincentes de ciencia ficción dura que podrían suceder realmente, y que algún día podrían suceder. Morris es autor de varias novelas de ciencia ficción de gran éxito de ventas, como la serie Enceladus.

    Brandon es un orgulloso miembro de la Science Fiction and Fantasy Writers of America y de la Mars Society.