#KnowledgeByte: Combining the #DarkEnergy Spectroscopic Instrument (#DESI) data with other experiments shows signs that the impact of dark energy may be weakening over time — and the standard model of how the #Universe works may need an update.

https://knowledgezone.co.in/posts/Is-Dark-Energy-Getting-Weaker-67f3f552da225d23b99cb17a

https://news.ucsc.edu/2026/04/desi-complete-3d-map/

#Astronomy #Astrophysics #Astrodon #DESI #DarkEnergy

A DESI Milestone

Yesterday the Open Journal of Astrophysics published a paper by Porredon et al which will feature in the usual Saturday round-up. That paper, which is based on the First Data Release from the Dark Energy Spectroscopic Instrument (DESI) reminded me that I should mention that DESI recently reached an amazing milestone – it has now mapped the positions and redshifts of 47 million galaxies and quasars! There is a full press-release about this achievement here.

Here’s a little video showing how the survey works:

https://www.youtube.com/watch?v=6H3diAK_KIc

There are more videos and other graphics in the press release.

Here’s a nice picture showing a thin slice through the full survey that reveals the characteristic “cosmic web” of the large-scale structure of the Universe in all its glory:

This progress is great, but it really makes me feel old. Forty years ago, in 1986, I had just started my PhD. The state-of-the-art galaxy redshift survey slice then is shown in this plot, from de Lapparent et al 1986 (ApJLett 302, L1), one of the first papers I read as a research student (I got it in 1985 as a preprint), which contains just 1,100 galaxies:

It is worth mentioning that although DESI has now covered its original target area, it will continue until 2028. You can never have too many galaxy redshifts!

Applied to graduate today. Still some pages left to go on my thesis, but it’s all booked and I can see the light.

Am I a masochist for wanting to do a PhD next?
#physics #gradschool #darkenergy