Globular Clusters

[dmill1220]

Globular clusters are generally composed of hundreds of thousands of old stars, similar to the buldge of a spiral galaxy,but confined to a volume of only a few cubic Parsecs. Some globular clusters, like Omega Centauri in our Milkay Way and G1 in M-31, are extraordinarily massive, weighing as many as several million solar masses. Some globular clusters like M-15 have extremely massive cores which are expected to harbor BlackHoles
While globular clusters can contain a high density of stars, they are not thought to be favorable locations for the survival of planetary systems. Planetary orbits are usually unstable within the cores of dense clusters due to the perturbations of passing stars. A planet orbiting at 1 astronomical unit around a star that is within the core of a dense cluster such as 47 Tucanae would only survive on the order of 100,000,000 years. However, there has been at least one planetary system found orbiting a Pulsar, PSR 1620 -26 that belongs to the globular cluster M-4 definetly not a canadate for life,the pulsar would see to that!

With a few exceptions, each globular cluster appears to have a definite age. That is, most of the stars in a cluster are at approximately the same stage in stellar evolution, suggesting that they formed at about the same time.
Globular clusters are typically the oldest objects in the Galaxy, and were among the first collections of stars to form.
The most massive main sequence stars in a globular cluster will also have the highest absolute magnitude, and these will be the first to evolve into the giant star stage.
As the cluster ages, stars of successively lower masses will also enter the giant stage. Thus the age of a cluster can be measured by looking for the stars that are just beginning to enter the giant star stage. This forms a "knee" in the HR diagram, bending to the upper right from the main sequence line. The absolute magnitude at this bend is directly a function of the globular cluster, and the age range can be plotted on an axis parallel to the magnitude.
By this method its shown that for example, that the cluster NGC-1818 is only about 40 million yrs old, while M-4 may be as old as 12.7 billion years. The later cluster, and other similar clusters, place a limit on the age of the entire universe. This lower limit has been a significant problem in Cosomolgy.
Why then Did astronomers decide to send a signal to M-13 in Hercules?

The Dutch astronomer Oosterhoff noticed that there appear to be two populations of globular clusters, which became known as Oosterhoff groups. The second group has a slightly longer period of RR Lyrae variable stars, Both groups have weak lines of metallic elements. But the lines in the stars of Oosterhoff type I ,OoI) cluster are not quite as weak as those in type II (OoII).
So type I are referred to as "metal-rich" while type II are "metal-poor". Wouldn't it have been a better idea to send a signal to another area of our own Milkway with stars in a open cluster of the same type as our own sun?
Globulars are one of my favorite objects to view, Im always hoping to catch an obvious Super Nova in these formations since most are very old. it would indeed be difficult to spot one. alot of them reside near our core but there are quite a few surronding the outer edge,or halo of or own galaxy,
Can you imagine what the sky would look like in or near the outside sphere of these globs!
I would imagine that there we be no night sky, it shouild be flooded with sunlight,what a drag if there was a civilization living in these areas,to me it would seem highly unlikely that there could be life that would evolve and survive long enough to recieve our message! whats the reason for sending such a signal to M-13 anyway?
Dennis

[Dragon Star]

Although I don't know exact reasons for that location, Life can be in the most unexpected places as long as it is given enough time to evolve, try strategics on such an improbability factor is like trying to aim your gun in the dark when you can't see your target, you may as well just shoot at random and hope you hit it.

[dmill1220]

Originally Posted by Dragon Star

Although I don't know exact reasons for that location, Life can be in the most unexpected places as long as it is given enough time to evolve, try strategics on such an improbability factor is like trying to aim your gun in the dark when you can't see your target, you may as well just shoot at random and hope you hit it.

Agreed! defintely no argument there!
But I think that I would have targeted a more friendly place for Planetary Systems,
I think its more like, we can faintly hear where to shoot in the dark by following the sound a liitle better from the knowledge we have gathered. after studying Globulars.
Do you have any Ideas On where I can dig up the reason for M-13 bieng targeted By Arcebio?
Ive tried a general search On the Net, but maybe Im not entering the right search criteria.
Dennis

[Dragon Star]

Yea, I know it makes sense to do that, but while you are wasting time choosing the prime locations, you could be just randomly shooting hundreds of signals all over the place and have a higher probability of something receiving it.

[dmill1220]

I agree! but, I think you may have missed my point.
in other words do you have any ideas, on what I would have to enter for a search on the web,for the answer,
There must of been somone deciding on what to target and why a gloubular.
Dennis

[Dragon Star]

http://seti.berkeley.edu/serendip/

That is all I was able to find that was linked to SETI.

[dmill1220]

Thanks!
I will try it and let you know what I find out.
I'm just Curious no big deal. looks like some serious digging from your link, just checked it out!
but I'm dieing to know why.
Here's a strange thought if there is someone out there, do we really want to let them know where we are? That could s**** !, chances are they would be farther advanced than our own society, Im not so sure if I would be making waves in a big sea anyway. plus we have already been beaming at least, TV, and radio waves ,for at least a 50 Light year radius,
Scary thought? Thanks again for the link I got to start somewhere! dragon check out my last attempt at Resolving M-27 Its in Monochrome, its in the astrophotography section.

Dennis

[Blue Fire]

Hmmmm... good question, dmill1220. Now you've got me curious! Man, it seems like I remember the big deal back then in 1974 when they sent that signal to M13. But the best I can come up with so far is that the signal was mostly ceremonial in dedicating the Arecibo Observatory and that the signal would also pass near some 30 stars along the way. But no direct, specific reference to reasons they picked M13 as the target.

I'll keep looking though, if you haven't already found your answer.

[Blue Fire]

Wow, this has been a challenge! I beginning to think, Dennis, that there was particular reason for chosing M13 other than just to do something symbolic that demonstrated our technology at the time (PR stunt?) as this says:
from: http://www.answers.com/topic/arecibo-message

Because it will take 25,000 years for the message to reach its intended destination of stars (and an additional 25,000 for any reply), the Arecibo message was more a demonstration of human technological achievement than a real attempt to enter into a conversation with extraterrestrials.

[Dragon Star]

Arecibo message

In 1974, a largely symbolic attempt was made to send a message to other worlds. To celebrate a substantial upgrading of the 305 meter Arecibo Radio Telescope in Puerto Rico, a coded message of 1,679 bits was transmitted towards the Globular Cluster M13, about 25,100 light years away.

The pattern of 0s and 1s contained in the message defines a 23 × 73 two dimensional grid which when plotted reveals some data about our location in the Solar System, a stylized figure of a human being, chemical formulae and an outline of the radio telescope itself. The 23 by 73 grid was chosen because both 23 and 73 are prime numbers, which makes it easier to decode the message. The reasons for this are:

* an attempt to factorize the length of the message would show that it can't contain a grid with more than two dimensions (since there are just two factors);
* assuming a two dimensional grid, there are only two possible resultant images, with dimensions 23x73 or 73x23.

Given the limitations of the speed of light for message transmission, no reply would be possible before the year 52,174 (approximately) and hence has been dismissed by some as a publicity stunt. A controversy arose because the transmission raised the serious question of whether a small group should be allowed to speak for Earth.

http://en.wikipedia.org/wiki/SETI#Arecibo_message

Best I could do.