Detailed 3D map of Milky Way shows 'warped' shape | Hacker News Reader

Detailed 3D map of Milky Way shows 'warped' shape

theguardian.com

110 pointssgt10128 comments

When I started grad school, one of the things my thesis adviser suggested I do was to spend a few hours looking at the Palomar Sky Survey plates (this was in 1980). I spent many pleasant hours doing that, and what was striking was how few perfectly symmetric spiral galaxies there are, in relative terms. You see beautiful symmetric galaxies pictured in your Astronomy text books, but in truth most spirals are warped, or show distortion from a nearby companion, or obviously are merging with another galaxy, etc. Most spiral galaxies are deformed.

I've developed a fascination with astrophotography, one day hope to have a camera that can manage more than pinpoints/streaks/black noise, and while I always liked to go look at the stars on clear nights the technical aspects of it have reawakened the interest in space. Seeing the Milky Way across the sky at night with the naked eye is amazing and makes it hard to forget your smallness. You can get lost thinking stars are just pinpoints of light because they all generally look the same, but larger masses of them and seeing galaxies, clusters etc in binoculars etc just juices me up. Imaging that I can SEE Jupiter but the light is taking 45min to reach me is mind-blowing. Forget the larger distances to stars...it's inconceivable at times. Sometimes I have gotten vertigo seeing how our Solar system is tilted and imagining us swirling through the arm.

One thing that seems to have changed is visible satellites. Or maybe I am just missing them. I recall as a child watching the sky with my grandfather and you'd regularly see a "star" moving across the sky and he'd excitedly point it out as a satellite.

I regularly see satellites passing overhead in inland Australia

>one day hope to have a camera that can manage more than pinpoints/streaks/black noise

You can build an arduino-powered "barn-door tracker" for ~$40 that will significantly help with this. https://www.youtube.com/watch?v=5hqXqqTtWzU

If you're hoping to hook up a DSLR to a telescope this won't help though, not big enough. Plus, this style of tracker only tracks through one axis, limiting exposure time to ~10seconds before stuff gets blurry & drift destroys the image... but that's still better than the ~2seconds or so that you get without it.

That's very cool thank you. I seem to recall an astronaut on the ISS making something kind of related with parts on hand...Don Pettit I think?

*Found it: https://science.nasa.gov/science-news/science-at-nasa/2003/2...

Do you mean 10 minutes? He lines it up with Polaris, so it only needs one axis of rotation. But I guess the alignment isn't that good since it is just eyeballed, but it should work for exposure times much longer than 10 seconds. He is even rotating the screw every 15 seconds which wouldn't make much sense for a 10 second exposure. =) Clever little project in any case. Thanks for sharing the video.

I can totally relate to what you’re describing. The vertigo you mention reminds me of the Total Perspective Vortex [0] from the “Hitchiker’s Guide to the Galaxy” books by Douglas Adams. I totally agree about seeing the Milky Way, the rings of Saturn or the Andromeda galaxy with your own eyes (with the help of binoculars or a small telescope). This really gives you a different perspective on our existence, life and the grand scale of things. One last piece of advice to aspiring astrophotographers, this is an expensive hobby and an addictive “disease” :-)

[0] https://hitchhikers.fandom.com/wiki/Total_Perspective_Vortex

I love those books. I always seem drawn to these super expensive technical hobbies like astronomy and photography that are out of reach. You just cannot do them well cheaply and I've wasted money in the past on crap telescopes etc. The "lotto list" has a high quality telescope, tracking mount etc, and cameras right toward the top. One of those backyard observatories and the skills to make my own telescope properly would be a dream.

You may be watching later at night. Low Earth orbit satellites are in the shadow if you watch later at night. As a child you probably only watched the sky shortly after sunset while satellites still catch the sun.

The sky from the planets at the outer regions far from the plane must be astonishing.

For an astronomer that lives there, yes. For naked eye would be mostly black sky, just like ours on edges. That's why I love our place, it shows our galaxy beautifully stretching across.

Do we have software to easily simulate that?

Celestia[0][1] can just about do it. In principle, it can show you what you'd see from any point in space. In practice, it's limited by the data it has (for stars, it uses the Hipparcos Catalogue, which only contains ~ 100,000 stars of the ~ 250 billion that are in the Milky Way) and displays the Milky Way, outside our "immediate" neighbourhood (i.e. several hundred light years), as just a set of amorphous blobs. Hence you can visualise the Milky Way as seen from the edge of the galaxy, but it'll be rather blurry. (It also obviously doesn't include the newly discovered warped shape.)

Edit: For this purpose, I think that this "Chrome Experiment"[2], might be better.

Also see "Gaia Sky"[3] which I haven't tried, but which looks really interesting and may well do what you want.

[0] https://celestia.space/

[1] https://en.wikipedia.org/wiki/Celestia

[2] https://experiments.withgoogle.com/100000-stars

[3] http://sci.esa.int/gaia/60036-gaia-data-release-2-virtual-re...

> As with the previous work, the new study shows the Cepheids disproportionately lie on one side of the warped galaxy, forming an arc-shaped spread.

> The Polish team also found younger Cepheids lie nearer the centre of the Milky Way, while older Cepheids are further out. A computer simulation revealed there would need to have been star-forming events 64m, 113m and 175m years ago to produce the distribution of Cepheids seen today.

I don't get why the Cepheids are bunched. Even with the modeling video. It shows them forming in bursts, yes. And with differential rotation, they bunch on one side. But still, it shows the formation bursts mainly on one side.

So why?

I'm not an astronomer. But I think that stars in galaxies are supposed to orbit with approximately the same period, independent of distance from the center, due to dark matter distributions.

So then that's maybe another thing unclear about the video. I'm certainly no reliable source.

Almost - stars orbit with approximately the same velocity, not period.

You beat me to it while I was looking for references. =)

"The stars and gas in the Milky Way rotate about its center differentially, meaning that the rotation period varies with location. As is typical for spiral galaxies, the orbital speed of most stars in the Milky Way does not depend strongly on their distance from the center. Away from the central bulge or outer rim, the typical stellar orbital speed is between 210 ± 10 km/s (470,000 ± 22,000 mph). Hence the orbital period of the typical star is directly proportional only to the length of the path traveled."

https://en.m.wikipedia.org/wiki/Milky_Way#Galactic_rotation

I’m pretty sure it’s because it’s harder to detect individual stars the farther away from us they are. So you’d expect the stars they found to be clustered around us. We are in the center of that group. The simulation goes back in time to imagine how the stars got to be where they are today.

If the earth was on the other side of the galaxy the group would appear there because the stars we would find would be there. I think the article writer misunderstood the astronomer about this and mismatched responses.

Thanks. I was suspecting that, because seeing stuff through the galactic core is so iffy. But TFA was so damn coy about why they're all on our side. As if it was some deep puzzle.

How far from the galactic plane is our Solar System?

Something in the neighborhood of 20 parsecs, according to: https://astronomy.stackexchange.com/questions/822/how-far-is...

However this is unusual for us. We spend most of our time farther from the plane, and just happen to be passing through at the moment.

Watching that video makes me wonder why so many Cepheids spawned in the sun's wake ~120 million years ago.

Fascinator hat!?!?

https://en.wikipedia.org/wiki/Fascinator

I don't get why they say "fascinator". To me, it's like my favorite old floppy hat.

Edit: https://m.media-amazon.com/images/I/61IdlF0D2eL._AC_UL320_.j...

Like when you see a pizza dough being spun...

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