VISTA views a vast ball of stars

May 09, 2012
This striking view of the globular star cluster Messier 55 in the constellation of Sagittarius (The Archer) was obtained in infrared light with the VISTA survey telescope at ESO's Paranal Observatory in Chile. This vast ball of ancient stars is located at a distance of about 17,000 light-years from Earth. Credit: ESO/J. Emerson/VISTA. Acknowledgment: Cambridge Astronomical Survey Unit

(Phys.org) -- A new image of Messier 55 from ESO's VISTA infrared survey telescope shows tens of thousands of stars crowded together like a swarm of bees. Besides being packed into a relatively small space, these stars are also among the oldest in the Universe. Astronomers study Messier 55 and other ancient objects like it, called globular clusters, to learn how galaxies evolve and stars age.

Globular clusters are held together in a tight spherical shape by . In Messier 55, the stars certainly do keep close company: approximately one hundred thousand stars are packed within a sphere with a diameter of only about 25 times the distance between the Sun and the nearest , Alpha Centauri.

About 160 globular clusters have been spotted encircling our galaxy, the , mostly toward its bulging centre. The two latest discoveries, made using VISTA, were recently announced. The largest can have thousands of these rich collections of stars in around them.

Observations of globular clusters' stars reveal that they originated around the same time — more than 10 billion years ago — and from the same cloud of gas. As this formative period was just a few billion years after the Big Bang, nearly all of the gas on hand was the simplest, lightest and most common in the cosmos: hydrogen, along with some helium and much smaller amounts of heavier chemical elements such as oxygen and nitrogen.

Being made mostly from hydrogen distinguishes globular cluster residents from stars born in later eras, like our Sun, that are infused with heavier elements created in earlier generations of stars. The Sun lit up some 4.6 billion years ago, making it only about half as old as the elderly stars in most . The chemical makeup of the cloud from which the Sun formed is reflected in the abundances of elements found throughout the Solar System — in asteroids, in the planets and in our own bodies.

Sky watchers can find Messier 55 in the constellation of Sagittarius (The Archer). The notably large cluster appears nearly two-thirds the width of the full Moon, and is not at all difficult to see in a small telescope, even though it is located at a distance of about 17 000 light-years from Earth.

The French astronomer Nicolas Louis de Lacaille first documented the stellar grouping around 1752, and some 26 years later another French astronomer, Charles Messier, included the cluster as the 55th entry in his famous astronomical catalogue. The object is also cross-listed as NGC 6809 in the New General Catalogue, an often-cited and more extensive astronomical catalogue created in the late nineteenth century.

The new image was obtained in infrared light by the 4.1-metre Visible and Infrared Survey Telescope for Astronomy (VISTA, eso0949) at ESO's Paranal Observatory in northern Chile.

As well as the of Messier 55, this VISTA image also records many galaxies lying far beyond the cluster. A particularly prominent edge-on spiral galaxy appears to the upper right of the centre of the picture.

Explore further: Does the galactic spiral lead the rotation of a galaxy?

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Lurker2358
1.7 / 5 (3) May 09, 2012
This article has a subtle, yet disastrous flaw.

I challenge some others to proof-read this very, very closely and then post back what you think I'm talking about.
Mike_Massen
3 / 5 (4) May 09, 2012
Should we do this with or without religious bias, I'm not sure of your position or expectation - are you looking for a debate or dialectic ?

Though it is interesting that this cluster exists in our own galaxy.

Is there any indication of angular momentum/axis of the cluster ?

If we could accurately model the whole galaxy in all the combinatorial complexity of gravitational interactions we might find a reasonable explanation but I don't expect we have that much time or enough computing resources and that would have to be based on a known initial condition at the same time across the whole galaxy, ie Rather unlikely.
elektron
5 / 5 (4) May 09, 2012
This article has a subtle, yet disastrous flaw.

I challenge some others to proof-read this very, very closely and then post back what you think I'm talking about.


Why not just state what you think it is. Because you imply that you have pronounced yourself automatically right and if you are not right you therefore condemn anyone who decides to take up your challenge to wasting their time. What is the point. If you have something to say then say it.
Lurker2358
3.7 / 5 (3) May 09, 2012
The way they date the stars age, as cited in this article, is wrong.

If the globular cluster stars are very high in hydrogen, then within the standard model of stellar life, they would need to be very young, not old. After all, Hydrogen is what stars supposedly start out with.

If a star has more hydrogen than the Sun, by percentage, then it is either very, very young, or it is very low in mass, else it would have burned it's hydrogen up by now if it was significantly older or more massive.

Being made mostly from hydrogen distinguishes globular cluster residents from stars born in later eras, like our Sun, that are infused with heavier elements created in earlier generations of stars. The Sun lit up some 4.6 billion years ago, making it only about half as old as the elderly stars in most globular clusters.


This makes no sense. The "older," so-called first generation stars should have higher metallicity than a second generation star that formed as a mixture... contine...
Lurker2358
3 / 5 (3) May 09, 2012
So you see, their dating methods are totally flawed.

IN fact, the Globular Cluster's stars, if they are rich in hydrogen, should be orders of magnitude YOUNGER than the Sun, (when comparing similar mass stars to similar mass stars,) not the other way around.

Luminosity of main sequence stars is roughly related to the 4th power of mass in solar masses related to solar luminosity.

therefore, a star twice as massive as the Sun should burn 16 times faster.

A star with the same mass as the Sun, but half the hydrogen concentration, should be at least twice as old as the Sun.

A star with the same mass as the Sun and more hydrogen concentration should be much younger than the Sun.

therefore, if the globular cluster stars are rich in hydrogen, that would actually make them significantly younger than the Sun.

So either this article is flawed, or the source material is flawed.
Lurker2358
1 / 5 (1) May 09, 2012
If the Globular Cluster stars were twice as old as the Sun, they should have finished most of their P-P chain reactions, and even most of the Helium based reactions, and should be running purely on the CNO sequence or even heavier sequences. Thus, they should have much lower hydrogen and much heavier metallicity than the Sun if they were really that old.

After all, the scientists claim teh Sun is a second generation star, and that the SS got it's heavy elements from a nearby supernova. HOWEVER, the original alleged first generations stars would need to have massive, iron and lead cores during the Supernova explosion.

Second Generation stars only pick up a scattering of dust from a SN explosion, therefore they should have lower metallicity than "old, almost dead first generation stars," which are composed almost entirely of heavy elements.

Therefore, the globular clusters are dated entirely incorrectly.

They are actually very, very young stars.
elektron
3 / 5 (2) May 09, 2012
You have answered your own question when you point out that the stars could be very low mass. Which would account for their old age as well as their predominance of H.
Lurker2358
1 / 5 (1) May 09, 2012
You have answered your own question when you point out that the stars could be very low mass. Which would account for their old age as well as their predominance of H.


No.

That's a good point, but not necessarily true.

It would depend on the individual star in the individual cluster.

There's no evidence presented to suggest these stars are particularly low mass.

Some of them could be, but even in the photo, some of them are clearly as much as an order of magnitude brighter than the others.

Additionally, first generation stars should generally be more massive than second generations stars, since there was more matter around to be collected at their formation. Therefore first generation stars should have a bias towards being more massive on average, not less massive.
Lurker2358
1 / 5 (1) May 09, 2012
One thing a globular cluster does theoretically explain is how to make an "intermediate mass black hole".

the way I see it, for a globular cluster that REALLY is very old and has a lot of stars nearing supernova stage, it would work like this.

Perhaps the central stars explode, becoming neutron stars or black holes if they are massive enough. The metals are collected by the outer stars. When the outer stars get old enough and explode, roughly half of their shells are directed back deeper into the cluster, where they will be collected by the neutron stars and black holes there. Over time, this could potentially add scores of stellar masses to the central neutron stars and black holes, which may consume one another through tidal frame dragging, forming one or more black holes in the 100 to 1000 solar mass range, while about half of the mass of the cluster would be ejected into galactic or inter-galactic space.

That's how you go from stellar black hole to intermediate mass reliably.
Lurker2358
1 / 5 (1) May 09, 2012
So then what you would end up with for an old Globular Cluster system is a core of several intermediate mass black holes orbiting one another, surrounded by thousands or tens of thousands of neutron stars and stellar mass black holes orbiting the core.

Which means that if they were old, you would expect them to make little visible light, and instead be a huge X-ray and Gamma source, bigger than anything in the galaxy except the Sagitarius SMBH.

So if Globular Clusters are very old, then they should appear as a giant fireball with some polar jets in varying directions when viewed in X-ray or Gamma, especially when they have as clear a shot as this M55 is taken.

If Globular Clusters are very old, they should have noticeable intermediate mass black holes in them, with perhaps polar jets.

Also, if they are very old, Supernovas from Globular Clusters should be much more common than they are in typical solo, binary, or trinary star systems.
barakn
3 / 5 (2) May 09, 2012
Lurker, are you really so lazy you can't look up the solutions to the false conundrums you've postulated?
Lurker2358
1 / 5 (1) May 10, 2012
Lurker, are you really so lazy you can't look up the solutions to the false conundrums you've postulated?


They are not false conundrums.

The article is flawed.

A false conundrum would be if a person presented a problem that doesn't actually exist.

I did not.

The problem is blatantly obvious to anyone familiar with mainstream theory on stellar formation and life cycles.

Hydrogen = new star.

Heavy metallicity = very old star.

The article is diametrically opposed to mainstream stellar models.
Shinichi D_
3.7 / 5 (3) May 10, 2012

Hydrogen = new star.
Heavy metallicity = very old star.
The article is diametrically opposed to mainstream stellar models.


It's not necessarily the case. A massive star can be very young, only few million years in it's main sequence, yet already have a very high metallicity.
A dwarf star on the other hand, can be very old, and very poor in metals. Dont forget, that according to standard modell, the absolute oldest possible red dwarfs are about at 10% of their main sequence life! There are no "old" dwarf stars in the universe, because the universe itself is not old enough. At the very best we can talk about "ancient" dwarf stars, that are some 10-11 billion years old, but these are still young.
With massive stars, it's the other way around. There are no old massive stars, because they simply don't live long enough. You can try to study "ancient" massive stars, that were born close to the big bang in time, but they are far away. There are no close and old massive stars.
Mike_Massen
3 / 5 (2) May 10, 2012
Theory of gravity was incomplete at the time of Newton but, a very good start which works at just below & just above the observable scales.

Models of star formation are just as much in their infancy.

There are many possible reasons for clusters to have low or high metallicity in conjunction or in contrast with low or high hydrogen.

Those scales are subject to all sorts of permutations and chaotic conditions which shift in & out of patterns of order.

We don't know what was in various clouds for billions of years before clusters formed *and* how they move, who has any knowledge of the preceding billions of years, so its not appropriate to argue the current model is wrong as if it is to be thrown out completely.

We didn't throw out gravity when Einstein came along it was amended & very likely that process will continue towards some asymptote of a semblance of truth.

To Lurker2358, please don't waste our times, get to the point efficiently, no ego games please, some of us are busy !
barakn
5 / 5 (1) May 23, 2012
The problem is blatantly obvious to anyone familiar with mainstream theory on stellar formation and life cycles.

Hydrogen = new star.

Heavy metallicity = very old star. - lurker2358
Actually I'm familiar with mainstream theory on stellar formation and life cycles. What you've forgotten or never knew is that metals are created in cores, and you've also forgotten the two main modes of energy transport in a star - radiative and convective. Metals are only going to be dredged up by convective zones, and even in those stars that do have a convective zone, there's usually also a radiative zone either shielding the convective zone from the core or covering both the core and the convective zone. Therefore metals remain hidden even in very old stars. When the star blows up, it provides the metals as a source material for nascent stars, which will then proudly display the metals on their surfaces. So yes, you were lazy and were presenting false conundrums. Stop wasting our time.