An all-sky map of half a million supermassive black holes | Hacker News Reader

An all-sky map of half a million supermassive black holes

sdss.org

190 pointsMarcoDewey40 comments

We also released the 2nd half sky catalogue of the eROSITA X-ray survey at the same time, for 1.5 years of operations, in collaboration with SDSS. Here is a sky map and 3D plot with redshift: https://www.mpe.mpg.de/8215311/news20260731

This almost doubled the number of known X-ray sources to 2 million.

> "almost doubled the number of known X-ray sources"

That's a fantastic achievement!

The number of massive maps of the universe in recent years are absoultely fascinating, and have reignited my childhood interest in astronomy and cosmology.

These maps consist of a large number of statistical observations derived from images, and that lines up with all the data analysis I've used in the past decades in genomics. (Most DNA sequencing data comes from image analysis, coincidentally!). And the plots I see in these papers are looking increasingly like the plots I've produced over the past 20 years, so I'm thinking maybe it would be fun to download a few TB of atlas and see if I can reproduce their plots...

Thanks for everyone who works in this field, it's fantastic work that's reshaping our very understanding of reality.

Scary as well though. All those cosmic powers, and here we are, not even ants standing on a hilltop.

On the flip side of scary, it can put your problems in perspective and offer some kind of solace. I guess it's a bit of both :)

Doing this in my early 20s helped me out of a depression.

The perspective shift is massive.

I find this sentiment so bizarre ... scared of what, exactly? There are real threats that people ignore, like rip tides, global warming, RFK Jr., and fascism, but those "cosmic powers" aren't coming to get us.

Love how you throw in RFK Jr. His muscular tone is certainly impressive!

I referred to real threats, and he is one. His muscles aren't relevant.

They are if you ever try to take his raw milk away

Or measles

Neither is 'fascism' or 'rip tides'! Some of us find the beauty and power of nature awe-inspiring, regardless of our day-to-day problems.

Knowing how precious the current state of Earth is at human scale makes me fear the asshats acting like everything revolves around “progress” a lot more than knowing how insignificant we are at cosmic scales.

Exactly. "We did ruing the only planet we ever knew, but at least for a brief moment in time we made a lot of value for Musk and his friends"

There's a diagram of the size of everything in the universe from quarks to the whole observable universe. https://www.universetoday.com/163927/everything-in-the-unive...

I honestly find it extremely comforting. Having something so much bigger than oneself in the world is calming. All my worries, all my loves, everything that goes well, everything that goes poorly, just a tiny blip in the hugeness of it all. To me, it makes the good things better, and the worse things less meaningful. I watch DESI animations every few months for a reminder.

Yeah ... for all our accomplishments there's still a decent amount of people globally (though it's falling) living without basics (food, clean water, safe living conditions), and we still fight over fossil fuels despite having clean energy like wind, solar, nuclear and others.

I'd give the human race a C-. Let's see if in our lifetimes we can improve on this.

What are the "gridded" regions in the middle? Is that some kind of measurement artifact?

If you're talking about the purple blotches, that's a map of the regions of the sky that have been targeted for observation. It's not the actual SMBH density.

Why are some areas more observed than others then?

Anyone ever worked with data from SDSS? What have you done with it? I imagine it's a gold mine for university students. I took an astronomy class and was able to plot the largest structures in the universe from their data, which was cool but pretty basic. I've loved astronomy all my life and I've always wondered if there was anything more one person or a small team could do with SDSS data. I took the class in 2010 so I imagine there are more possibilities now with AI?

Interesting how anisotropic it is. Naively I would have assumed it would be roughly symmetrical

I think that's more a result of our incomplete/inconsistent scanning.

On the other hand, the ancients assumed there had to be big continents in the southern and western hemispheres to "balance" the land in their own quadrant.

They turned out to be right, but not quite for the reasons they put forth.

As a non-cosmologist, I'm unwilling to speculate on what "should" be out there, because my mental model is probably very wrong (keeping in mind that our best models of what's happening out there are also probably quite wrong).

Luck of the draw that they weren't lizard people on pangea, making that prediction.

Well, in more formal terms, cosmology has the 'cosmological principle'[0], which is a conjecture that at large enough scales, the universe is universally isotropic and homogenous wrt the distribution of matter. Basically that it should average out to the same density everywhere, and should look basically the same in terms of how much matter there is from wherever you pick.

There'd be a lot of cosmology glory in proving that wrong. They'd put your name before Hubble's.

[0] - https://en.wikipedia.org/wiki/Cosmological_principle

Interesting indeed but might be an artifact of regions being surveilled and Milky Way disk both containing more easily detectable holes and obscuring some areas with the dust clouds (I am not an astrophysicist or astronomer)

Supermassive black holes are generally at the center of galaxies, like a tiny yolk in an egg. That's not a hard rule. For instance, they can theoretically be ejected and make a mess if a few galaxies collide. But yes, it's harder to detect far away objects when the bulk of our milky way is in the way, making things milky. I suspect there are a lot of black holes back there that we just can't see.

As others say, this is probably mostly artifacts from the survey design (e.g. eROSITA data rights), but the Galactic plane definitely limits things too.

This video of the DESI galactic map shows the directions that are possible to survey with optical light, in a very cool way:

https://www.youtube.com/watch?v=VSTGiRLWzS4

Nature is a painting, not a pattern.

I tend to assume that the obvious gridded point pattern is a sky sampling artifact - but it would be far more interesting if it's a real thing.

How different is "mapping supermassive black holes" from "mapping galaxies"?

Is the distribution because of taking time to look/equipment? or is that actually related to the distribution (clumps in various directions).. I would guess the lines and things are "that's where we've looked" vs. "that's all there is".. I wonder if it's gonna line up with the CBR.

Perhaps including one that is scooting across the universe (Dr Becky): https://www.youtube.com/watch?v=EHLF6sgLdrs&t=4s

Woah, cool. Why is the map so uneven? Does this reflect differences in how frequently such objects occur, or does it have to do with how the scanning works?

Various types of 'lumpiness' in the observable universe are huge topics of research.

if they used X-Rays for that, why does Event Horizon Telescope use millimeter waves?

Thanks, now I know where not to go

On the bright side, you could live much longer if you went near a black hole. Though, that's according to everyone else's reference frame, not yours. Also, the gravity probably wouldn't feel nice. So, I concur.

They can watch me flipping them all off for an eternity as I descend into the abyss.

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