Scientists have long tried to explain the origin of a mysterious, large and anomalously cold region of the sky. In 2015, they came close to figuring it out as a study showed it to be a "supervoid" in which the density of galaxies is much lower than it is in the rest of the universe. However, other studies haven't managed to replicate the result.
Now new research led by Durham University, submitted for publication in the Monthly Notices of the Royal Astronomical Society, suggests the supervoid theory doesn't hold up. Intriguingly, that leaves open a pretty wild possibility – the cold spot might be the evidence of a collision with a parallel universe. But before you get too excited, let's look at how likely that would actually be.
The cold spot can be seen in maps of the "cosmic microwave background" (CMB), which is the radiation left over from the birth of the universe. The CMB is like a photograph of what the universe looked like when it was 380,000 years old and had a temperature of 3,000 degrees Kelvin. What we find is that it is very smooth with temperature deviations of less than one part in 10,000. These deviations can be explained pretty well by our models of how the hot universe evolved up to an age of 380,000 years.
However the cold spot is harder to work out. It is an area of the sky about five degrees across that is colder by one part in 18,000. This is readily expected for some areas covering about one degree – but not five. The CMB should look much smoother on such large scales.
(Score: 2) by Zinho on Thursday June 01 2017, @08:01PM (2 children)
Map Projections [xkcd.com]
I have to ask why they chose an elliptical projection of the sky (although it could also be pseudoazimuthal, [wikipedia.org] hard to tell without recognizable landmarks in the data set). Kudos for using an equal-area projection at least.
Anyone else think this would make a pretty pattern for a Watterman butterfly? [wikipedia.org]
"Space Exploration is not endless circles in low earth orbit." -Buzz Aldrin
(Score: 0) by Anonymous Coward on Friday June 02 2017, @06:44AM (1 child)
I don't know why, but I can tell you that, AFAIR, every CMB map I've seen has used exactly the same projection.
Just a wild guess, but maybe an equal-area projection makes sense when you're comparing areas :)
(Score: 2) by Zinho on Friday June 02 2017, @05:16PM
Same here, and it's always bugged me a bit. Too much distortion for my taste at the sides, and with no lines marking latitude or longitude I have no idea which way the distortion is going. At a guess I'd hope that they're maybe using Polaris as the north reference, and the ecliptic for the equator; however, there's nothing really constraining them to that. I'm not familiar enough with astronomy to guess what they'd be using as their prime meridian, either. One of the Zodiac constellations?
I just took the time to google it, and it seems they do have an equirectangular projection available [caltech.edu] as well. No indication which latitude(s) are the standard parallel(s); hopefully it's the equator since they're intending it to map onto a dome for projection. They're using galactic coordinates, that puts the galactic plane as the equator and Sagittarius A* as the prime meridian. The things you learn.
Right, no problem there. It's not like they don't have other options [wikipedia.org] to choose from, though. Choosing the one they did with no reference lines drawn in makes it a bit disorienting.
Of course, in the spirit of my XKCD quote, my opinions on the map projections astronomers use are of little consequence to the astronomers; take my nerd rage with a grain of humorous salt :P
"Space Exploration is not endless circles in low earth orbit." -Buzz Aldrin