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that gif is blowing my mind

we're traveling in like a "solar up" direction?? where are we even going? this is madness.

the sun isn't moving exactly in the plane of the galaxy, but approximately so. and yeah apparently the plane of the solar system happens to be about 60° to the plane of the galaxy. who knew.

oh great so we're cockeyed too

iphone people: i recommend the app "exoplanets"

you can explore the MW, throw it around, pinch in out, etc.

and you can make neat graphs like size of planet against discovery year (notice we're getting good at finding smaller and smaller planets, i.e. closer and closer to earth mass)

we're traveling in like a "solar up" direction?? where are we even going? this is madness.

― goole, Friday, March 1, 2013 2:51 PM (6 minutes ago) Bookmark

http://i.imgur.com/CXIjIEr.jpg

Thought the Sun was moving at about the same velocity as nearby parts of the galaxy. There's nowhere to put the camera to capture this. The only way to get this effect given movement of nearby bodies would be to have the camera moving away from solar system at Ludicrous Speed, in which case the experience will be of the observer moving, not the solar system. No?

figuring out what's going on in the solar neighbourhood is very, very tricky and it's very difficult to visualize how they do it. but they do it by observing nearby stars.

on average they're all going round the sun at about the same speed in the same direction, 200-odd km/s. there's some scatter though. some are on perfectly circular orbits in the plane of the galaxy, some wobble up and down, some are on "radial" orbits, i.e. plunging toward the middle and out the other side, and only happy to be passing through the solar neighbourhood right now.

the upshot of that scatter in velocity/direction is that the stars that are close to us right now, will not be our nearest neighbours forever

http://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Near-stars-past-future-en.svg/749px-Near-stars-past-future-en.svg.png

Right, but those changes are glacial for any observer in a human time scale. There is literally nowhere to put a camera to visualize that gif. Even if the "camera" moved that fast away from the S.S. it wouldn't see the Sun translating so dramatically against the backdrop of near space, which is also moving at similar speeds in similar directions.

well that gif is just showing what voyager II is beaming back .... dunno what to tell ya man

afaict the camera is orbiting the centre of the MW faster than the sun, which is why the stars in the b/g are seen in parallax

apart from the scale issues, it looks basically plausible

http://m.youtube.com/watch?v=C4V-ooITrws

Quite a bit clearer. In the youtube description he lists the duration of precession cycle as 25,000 years, with over 8000 cycles in one 226 million year revolution of the galactic center.

Of course if the planets complete hundreds or thousands of revolutions around the Sun while the Sun makes one cycle around the vortex, the planetary orbits themselves aren't especially helical, as was shown in the first video.

The visualization also highlights the movement of the solar system against a static haze, without showing the (I guess similarly helical?) movements of other stars nearby, which would show the galactic arm rotating more or less in unison, as is suggested by the wider views at the beginning of the new video.

yes the original anim exaggerates the pitch of the helices formed by the orbits of the planets too, good point

spiral arms is a complicated one

good grief what a bore http://www.slate.com/blogs/bad_astronomy/2013/03/04/vortex_motion_viral_video_showing_sun_s_motion_through_galaxy_is_wrong.html

dude it's important to stop the hoi polloi taking any interest in SCIENCE

i mean you know you're in for a fun old time, and some excellent, concise writing, when you come across passages like

However, there’s a problem with it: It’s wrong. And not just superficially; it’s deeply wrong, based on a very wrong premise.

his specific valid criticisms of the animation, beyond that it is apparently accompanied by some crank's nonsense idea of the universe, and that crank doesn't know the difference between a vortex and a helix, basically boil down to the fact that the ecliptic (solar plane) is at 60° not 90° to the galactic plane.

this criticism in particular is totally unfair/wrong:

That is apparently what Sadhu is representing in his video. But that wobble does not affect the Sun at all. It’s just something the Earth does. But Sadhu adds that to the Sun’s motion around the Milky Way, which makes no sense. His video shows the Sun corkscrewing around the galaxy, sometimes closer to the galactic center and sometimes farther away over and over again. To go back to the carousel analogy, its like the horse is circling the center, moving up and down, and also left-to right. But that's not what the Sun really does. There is no left to right motion (toward and away from the galactic center multiple times per orbit). That corkscrew pattern Sadhu shows is wrong.

well, it is an it isn't. seen from above the galaxy, the sun isn't on a circular orbit. it is sometimes closer and sometimes further away. it goes on these excursions in and out at its epicyclic frequency. this is undergrad stuff. tbf it's obvious that's what not the animator has in mind with his crazy theory (he calls it a "precession", which is, at best, a pretty fundamental misunderstanding), but the to say simply and clearly that "the corkscrew pattern is wrong" is wrong.

Have to love when a fan of a nutty theory likes to make animations

South Park for example

that's a nice city, i have some cousins there. one is a foxy tv presenter, i'll send you her facebook.

― the late great, Wednesday, July 4, 2012 10:00 AM (8 months ago) Bookmark Flag Post Permalink

you never her

Caek

whats it all about, really

caek have you ever met this guy: http://www.cv.nrao.edu/~jmangum/

I work w/ him on the journal he edits & I like how he has a link on his page for "not THAT J3ff M@ngum"

i have not met him, probably due to the weird schism between radio and optical astronomy (i am optical)

xp, i know right?

http://images.gizmag.com/hero/esa-planck-cmb.jpg

this is a decayed map of the world someone found in the back of an old shed, who are they trying to fool

gah

http://images.gizmag.com/hero/esa-planck-cmb.jpg

i think a lot of people are kind of disappointed there wasn't definitive evidence of significant non-standard "anomalies" in those results, although it seems like there is probably something slightly weird going on. otherwise they've measured a bunch of numbers we already know to greater precision.

some good summary coverage from one of the uk-based cosmologists working on it

http://www.andrewjaffe.net/blog/science/000553.html
http://www.andrewjaffe.net/blog/news/000554.html

caek I just want you to know that I am going to read all of this thread (missed it somehow until now) in preparation for MCDONALD OBSERVATORY SECRETS OF THE UNIVERSE time!

cool! this is still a can do go situation!

Caek

how can a person be said to exist at all, were one to use a galactic scale? How does yr answer to this question inform yr pickup technique?

Cos i see it having ultimate neg potential tbrfr

I think that might fail as a neg. True, space is mostly empty, but the earth is not. I am in torquay marks and Spencer's right now so I can say this with some certainty.

-_- *perspective*

Dear caek,

1) Which telescope will you be using at McDonald?
2) Whatcha gonna do with the telescope?
3) I seem to recall reading somewhere that the color of the universe is kinda muddy olive. T/F?
4) What kind of beer do you like to drink in West Texas?
5) What is you favorite kind of taco?

Blue taupe iirc

i will be on the 107" aka the harlan j smith. i will be measuring the mass of the most massive black holes (i.e. this stuff http://www.bbc.co.uk/news/science-environment-20528137)

the universe is as black as midnight on a moonless night in my experience.

the west texas beer situation is improving thanks to the big bend brewing co in alpine, and i am really looking forward to drinking a vulgar amount of this on my forthcoming trup. but apparently they have struggled with licensing, and i have not had a chance to try it. so i usually drink alamo golden ale or shiner or whatever is on happy hour, i.e. bud/miller light.

i don't eat meat so my favourite taco is the fish taco. i love fish tacos!

In the optical telescope world, does bigger always equal "better" or do different size telescopes do different things better/worse?

Also: what is your all-time favorite telescope?

And: how does one go about booking time on a major telescope? Do you have to pay for it, or drink beers with the right people, or????

yes, basically.

bigger telescopes have technical difficulties. e.g. you can't machine a single piece of glass for the mirror much bigger than about 8m, so to get above that you have to build segmented mirrors like keck in hawaii. and segmentation requires active optics http://en.wikipedia.org/wiki/Active_optics, which is complicated and therefore expensive and unreliable. and if you put exactly the same instrument configuration/optical set up on a bigger telescope as on a smaller telescope then you'll have problems with a tiny field of view (think like the zoom lens on a camera). and small field of view is generally not a good thing, especially if you are observing "extended objects", i.e. galaxies, blobby things, etc. but you would never do that. so in practice, bigger is better, cost and robustness notwithstanding.

my all time favourite telescope is the 200" hale telescope at mt palomar: http://en.wikipedia.org/wiki/Hale_telescope. it was the biggest telescope in the world for most of the 20th century. the dome is beautiful (and because of old school mount, still the biggest dome in the world, i think). if anyone is in socal ever then i highly recommend a visit. it's a great site, maybe even prettier than the mcdonald.

you get telescope time by applying in a competitive process. they put out a call for proposals every 3-6 months, you say what you want to do, how many nights you need to do it etc. and then an anonymous committee ranks the proposals and a scheduler tries to fit all the highly ranked proposals in. once you get awarded time, it's free, except you might need to pay for bed and board on site (e.g. i have to pay like 100$/night to stay in the lodge at the mcdonald). you can't really stay off site, even at a place like the mcdonald, which has towns relatively nearby.

http://www.astro.caltech.edu/palomar/images/blog/EscondidoBrochureCover.jpg

Somehow read that as "One of California's Greatest Booty and Recreation Spots"

hey caek gimme a holler when you're in san diego

i thought you were in new york? but yeah, definitely!

http://neo.jpl.nasa.gov/risk/

I don't know if this is your thing Caek, but could you recommend any good docs about the Cambrian Extinction? I watched an old beeb one recently and thought maybe they have new data since that one.

I don't know anything about that stuff. It is very cool though. I do remember thinking evolution by Carl zimmer was great by that's not what you're looking for. Too general.

Thanks anyway. The doc was an episode of Horizon called The Day The Earth Nearly Died (2002) and it was very interesting. Previously they thought the Permian Extinction was some extremely rapid event that took out 96% of life on the planet and in this they found new data. It was multiple events and it took hundreds of thousands of years to nearly take us all out of the game.

imminent detection of dark matter in the news a lot at the end of last week. here's why most of those articles were nonsense. http://profmattstrassler.com/2013/04/03/ams-presents-some-first-results/

some more planck stuff. pity the people who staked their careers on non-gaussianity: http://telescoper.wordpress.com/2013/04/07/has-planck-closed-the-window-on-the-early-universe/

also max i enjoyed your article about black hole death.