Starship Asterisk*

d2386n123 wrote:If you lived on a planet inside that globular cluster, how different would the night sky look from ours?
Would there be far more stars in the sky?

Q: What does the sky look like from the center of a globular cluster?

A: Here are some numbers. A typical globular cluster core region has about 100,000 stars in a volume of space about 10 parsecs in radius. This works out to a spherical volume of about 4000 cubic parsecs or about 25 stars per cubic parsec. This means that the typical distance between these stars is about (25)^-1/3 or about 1/3 parsec. These stars are mostly evolved giants with a luminosity of about 100 times the Sun, so at 10 parsecs, such a star would have an apparent visual magnitude near zero, and at 1/3 parsec it would have a magnitude near -6 making it as bright as Venus or Jupiter at their maximum brilliance. There would be about a dozen or so of these very bright stars, as bright as Venus, spread across the sky. The most distant stars would be near 10 parsecs and there would be many thousands of these, and each one would have a magnitude near zero...so the sky would be filled with 100,000 stars each brighter than the star Sirius, and a handful brighter than Venus at its maximum brilliance. There are 42,000 square degrees in the sky, so there would be one of these stars in every patch of the sky about the size of the full moon ( 1/2 degree)!!! It would be very difficult to see faint stars with the naked eye because your eye would constantly be flooded by the light from these numerous red giant stars.

This is my best estimate for what it is worth.

JuanAustin wrote:how can so many stars in such a small space exist without collisions? do they repel each other? do they revolve around the center of the cluster or do they just float together evenly spaced? if they're such old components in and of themselves, surely they should've all crashed into each other after 15 billion years!

nstahl wrote:It seems to me I've read that planets in such a region would be perturbed enough by passing stars that they'd stand little chance of staying in orbit, even assuming they could form. And from what I read above there wouldn't be much solar energy to power life for a planet wandering randomly through such a region, so likely there are no astronomers there looking back toward us. Or at least no planet-based astronomers :).

Comments?

Chris Peterson wrote:

nstahl wrote:
It seems to me I've read that planets in such a region would be perturbed enough by passing stars that they'd stand little chance of staying in orbit, even assuming they could form. And from what I read above there wouldn't be much solar energy to power life for a planet wandering randomly through such a region, so likely there are no astronomers there looking back toward us. Or at least no planet-based astronomers .

It does seem likely that such a region would not allow stable planetary systems to exist.

[c]Sorry that no one was at home when we called.
We'll call back later.[/c]

JuanAustin wrote:Even in the densest globular Omega Centauri where there's 100 million stars in roughly the same volume of space as 47 Tuc?

JuanAustin wrote:just out of curiosity, if one of these globular cluster stars "evaporated" as you put it, and was captured by our sun when it strayed nearby, what would be the effect on the earth and the other planets as it set up shop as a binary? what else could happen other than becoming a binary?

if it happened to be the same size as our sun, would the doubling of light burn us to a crisp?

JuanAustin wrote:that's pretty frightening. are there any nearby likely candidates or are all our stellar neighbors in a stable situation? do we have the capability to spot such a catastrophe in advance?

rstevenson wrote:It's possible there are nearer stellar neighbours, of the class brown dwarf, that we just haven't seen yet.

rstevenson wrote:

JuanAustin wrote:
that's pretty frightening. are there any nearby likely candidates or are all our stellar neighbors in a stable situation?
do we have the capability to spot such a catastrophe in advance?

Not to worry. Nothing moves very fast relative to the vast distances of space. For example our second nearest neighbour, Barnard's Star, is moving in our general direction at a speed of about 140 km/sec but will only get to its closest approach of about 3.8 light years away in about 9200 years from now. Building a bunker might be premature.

It's possible there are nearer stellar neighbours, of the class brown dwarf, that we just haven't seen yet. But to have any near-future impact on Sol's system any such would have to be very close already and we'd probably be detecting perturbations in planetary and other orbits.

As for getting any warning, we've recently been putting into orbit some quite extraordinary technology. Within a few years we should have a very clear idea of just what else there is in our neighbourhood besides the obvious bright objects.

JuanAustin wrote:one last question..., has anyone casually or seriously considered any potential astronomical hazards related to the mayan Dec 2012 prediction? i still find it so incredible how such an ancient civilization could be so accomplished in astronomy.

JuanAustin wrote:sorry, what i meant was a predicted rare alignment of the sun in a galactic equinox. i just find it so incredible how they could be so skilled as to arrive at this information.