XMM-Newtons massive discovery
25 August 2008
ESAs orbiting X-ray observatory XMM-Newton has discovered the most massive cluster of galaxies seen in the distant Universe until now. The galaxy cluster is so big that there can only be a handful of them at that distance, making this a rare catch indeed. The discovery confirms the existence of dark energy.
The newly-discovered monster, known only by the catalogue number 2XMM J083026+524133, is estimated to contain as much mass as a thousand large galaxies. Much of it is in the form of 100-million-degree hot gas. It was first observed by chance as XMM-Newton was studying another celestial object and 2XMM J083026+524133 was placed in a catalogue for a future follow-up.
This is written for the general public, so I assume the author means accelerate positively (speeding up) as opposed to accelerate negatively (slowing down). In popular speech people use decelerate instead of accelerate negatively; they use accelerate instead of accelerate positively.
It wasn't so long ago that scientists thought that the expansion of the universe was slowing down. Now they think it is speeding up; hence they postulated the existence of dark energy and dark matter. Do they have any way of describing what dark energy and dark matter are?