This image is one of my first views into my collection of astronomic data. It will take some time for it to load; the file is quite large. It should be more or less smoothly animated when it is finished loading.
Each point in this image represents one of 70,000 quasars. Quasars are supermassive black holes at the center of galaxies. Cosmologists love them because they are extremely bright, even at vast distances. Quasars can consume multiple Suns-worth of material every year, and they convert it into energy more efficiently than a star does. The result is a bright beacon in the sky that cosmologists can use to map the universe.
The colors in the image indicate distance from earth. Bluish quasars are closer to the earth, and reddish ones are farther away. Because the distances are so vast, and because of the time it takes for their light to reach us, we are also looking farther back in time the farther away we look. At the far red end of the image, we are seeing 13.03 billion years into the past, so far back that it was shortly after the creation of the universe.
The quasar map is shaped like a cone of light because we are mapping them from earth, and the star survey only studied specific regions of the sky. It kind of looks like we pointed a flashlight into space. If you look closely, there is a band in the middle that is kind of sparse. This is because the survey didn’t focus there as much.
The reddest quasars are actually farther away than 13.03 billion lightyears. It took 13.03 billion years for the light from them to reach us, but this whole time the universe has been expanding. So they are probably something more like 28.7 billion lightyears away by now, assuming that the universe expansion rate has been constant this whole time.
These values were determined by analyzing the redshift of the light that reaches earth. We know what distant stars are supposed to be made of, and we know what the spectral signatures of that material is. When we look at the spectrums of starlight, they have the material spectral signature that we would expect, but slightly redder than it should be. Scientists believe that this is because the galaxies are moving away from us, and the farther away they are, the faster they are moving away, so the light is redshifted farther. But there could be other explanations, also.
The coordinates that you are most familiar with are probably something like the x-, y-, and z-axes. Sky survey coordinate catalogs store location information in Right Ascension, Declination, and Redshift. Right Ascension is similar to East-West in the celestial sphere, Declination is similar to North-South, and Redshift can be converted to distance through some math.
I can run a Python script on the data, and it pulls out 70K quasar coordinates, renders them into a bunch of frames, and stitches them together into a GIF. Along the way, I can pull out information from the data, like the distance of the farthest quasar. It really feels a lot like I am using a telescope to search through space, even though I mostly interact with it through a Python script.
=== 🔬 Closest Quasar ===
RA: 6.0796, DEC: -1.6382, z: 0.0380
Distance: 166.68 Mpc Mpc (5.44e+08 lyr ly)
Lookback Time: 0.53 Gyr Gyr
=== 🌌 Farthest Quasar ===
RA: 12.0307, DEC: 16.1531, z: 6.8891
Distance: 8783.21 Mpc Mpc (2.86e+10 lyr ly)
Lookback Time: 13.02 Gyr Gyr
=== 📊 Summary Statistics ===
Mean z: 1.710, Median z: 1.664, Std z: 0.708
Mean dist: 4644.74 Mpc Mpc, Median: 4775.33 Mpc, Std: 1226.70 Mpc
Mean lookback: 9.52 Gyr Gyr, Median: 9.89 Gyr, Std: 1.69 Gyr
Note that these statistics do not describe the entire catalog. They only represent the 70,000 quasars pulled at random to render this video. I will do a deeper analysis on the entire data set later.
