thought experiment?

[yusufcam]

just looking at a photo of Omega Centauri.

Ever wondered what the sky would look like if you lived on a planet within a globular cluster?

[julianh72]

There's a good discussion here:
http://physics.stackexchange.com/questions/26555/what-if-our-sun-were-located-in-the-middle-of-a-globular-cluster

The writer concludes that you would have something like 1000 times more naked-eye stars (> Mag 6) than we see on earth, but the night sky would glow about 3 orders of magnitude brighter than a badly light-poluted urban sky, so I'm not sure how many you would actually be able to see.

[julianh72]

Here's a rather more scholarly discussion (with "photos"!) :

http://io9.com/what-the-night-sky-would-look-like-from-inside-a-globul-1589324556

[yusufcam]

in my minds eye, i imagined it as a view of a sky with multiple suns, rather than stars. But given Omega Centauri is 150 light years across and Alpha Centauri is 4 light years away and appears as a distant spec in the night sky, i suppose the images they have posited would be correct.

not to say that the former might not exist.

[julianh72]

The article http://io9.com/what-the-night-sky-would-look-like-from-inside-a-globul-1589324556 talks about 47 Tucanae as being 120 light-years across and containing 570,000 stars. (Although Wikipedia says "millions of stars" http://en.wikipedia.org/wiki/47_Tucanae .) By my reckoning, using 570,000 stars, that makes the mean star-to-star spacing about 1.1 light-years. Of course, the actual spacing will tend to be much closer near the core, and further apart at the periphery, but it's a number to start with, to get some context. The article says:

"At the center, our planet would be surrounded by a few hundred stars per cubic light-year (several thousand stars per cubic pc), which is thousands of times the stellar density of the Sun's neighborhood in the Milky Way's suburbs. The typical distance from our hypothetical planet to the closest star, however, still would be substantial — about 0.05 light-year (0.015 pc). In our solar system, this would place it beyond the inner edge of the Oort Cloud of comets."

For Omega Centauri, with a diameter of 150 light-years and containing about 10,000,000 stars, I calculate a mean separation of about 0.6 light-years, but again, they will be much closer at the core.

The angular diameter of the Sun, viewed from a distance of one light-year, would be about 0.03″, and at 0.05 light-year it would be about 0.6", so even near the core, most "typical" stars (apart from super-giants) would still appear as pin-points to the naked eye, but the nearest stars would be resolved as discs in a telescope. Only a couple of stars at most would be naked-eye discs - e.g. if your sun happened to be part of a tightly bound binary system.

Ain't the Universe an amazing place?!

[yusufcam]

hi julian,

wouldn't it be crazy fun to be able to pull out a deck chair on a beach somewhere in the universe and to watch some of the more exotic stuff out there at a distance similar to our own sun.

like the suns that orbit each other at astronomical speeds, an optical pulsar, a supernova remanent, and on.

[AlexN]

Imagine living on a planet orbiting a relatively new star in the heart of the orion nebula or the eagle nebula at the tip of the pillars. The view must be amazing.

I always was amazed when reading that if the tarantula nebula was as close to earth as m42 is it would fill the night sky and be so bright it would cast a shadow ... That must be an impressive view.

[speach]

And we whinge about a full moon, I'm rather glad the night sky is like it is.:)

[clive milne]

A voorwerp would be top my list

[silv]

with the night sky so polluted as in "if the tarantula nebula was as close to earth as m42 is it would fill the night sky and be so bright it would cast a shadow",
planet inhabitants would take much much longer to even look up with conscious curiosity.

so I think I'd say: the darker (and less interesting) the night sky is the faster intellectual evolution regarding astronomy and space travel will develop.

now, that's a new criteria for searching for extraterrestrial life forms to go visit. we wouldn't want to scare them if they are assumably completely ignorant :thumbsup:

[AussieTrooper]

Perhaps the most interesting prospect would be the fact that it would be well within the realms of possibility to send a probe to the nearest star. It may take 20 years to get there, but certainly doable.

[rustigsmed]

you should download the incredible universe simulator Space Engine.
http://en.spaceengine.org/

https://www.youtube.com/watch?v=UxEnZ1qVjPc


you can fly to pretty much anywhere and experience what the brightest/dense or darkest places in the universe would appear like.