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Home / what likely happened to the other stars in the cluster the sun was born in?

what likely happened to the other stars in the cluster the sun was born in?

Measuring the Age of a Star Cluster

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Boosted reading from www.astronomynotes.com

  • Confirmation of Stellar Development Models

Star clusters provide usa with a lot of information that is relevant to the report of stars in general. The primary reason is that we assume that all stars in a cluster formed almost simultaneously from the aforementioned cloud of interstellar gas, which means that the stars in the cluster should be very homogeneous in their properties. This means that the simply pregnant divergence between stars in a cluster is their mass, but if we measure the backdrop of ane star (age, distance, limerick, etc.), we can presume that the backdrop of the residue of the stars in the cluster will exist very similar.

In reality, some stars in the cluster form before than others, just compared to their lifetimes, the spread in their formation times is small and tin be ignored. We also assume that the stars in a cluster are nonetheless distance away from united states. Again, there is in fact a spread in distance, but, in most cases, this spread is much smaller than the altitude to the cluster, then it can be ignored. For example, the outermost stars in the globular cluster M13 are well-nigh 50 parsecs from the center of the cluster, just the cluster is about 7,700 parsecs abroad from us. Finally, we assume that the chemic limerick of all of the stars in a item cluster should exist very similar because the cloud of gas from which they formed is expected to accept been well mixed, so the individual cloud fragments that formed private stars should all have contained the aforementioned mix of elements and molecules.

When stars form out of a molecular deject, very high mass stars (perhaps up to about 100 times the mass of the Sunday) all the style down to low mass, chocolate-brown dwarf objects (about 0.08 solar masses) are formed. Observations of newly formed populations of stars have shown united states of america that very few high mass stars form, while many low mass stars grade. The drop-off is very steep as you get to college masses, likewise. If y'all were to survey the stars nearly the Dominicus, you would find that most 90% of all stars in our Solar Neighborhood are less than or equal to the Sun'due south mass. Most of the rest are less than twice the mass of the Sun, and only nigh 0.5% of all nearby stars are more massive than viii times the mass of the Sun. Remarkably, observations of star formation in many different locations in the universe seem to indicate that the relative ratios of stars of different masses that course is a universal law. That is, the same relative proportion of loftier mass compared to low mass stars ever forms regardless of the size of the star forming region, the environment in which the star forming region resides, and how long ago the stars formed. Therefore, if we tin decide how i cluster of stars formed, we tin generalize our findings to apply to all clusters. This idea of a relationship between the number of stars formed in a star forming region and their mass is referred to as the stellar initial mass function.

Let u.s.a. follow the development of an entire cluster of stars through several stages of its lifetime.

This presentation (with credit to Penn Country Astronomy & Astrophysics) allows you to click through slides that step you lot through the evolution. You volition see a serial of schematic 60 minutes diagrams for the stars in a cluster. In each frame, every bit the stars age, their luminosities and temperatures evolve, irresolute the overall appearance of the diagram with historic period.

The presentation progresses in the following manner:

  1. At an early fourth dimension stamp in the star cluster's formation, what we will call t=0, most of the high mass stars take reached the Main Sequence, while some of the lower mass stars are still in the T Tauri phase.
  2. 10 million years (107 years) later, the highest mass O stars take used up all of their hydrogen and brainstorm to evolve off the Master Sequence.
  3. Later 100 million years (108 years), all of the O stars have gone supernova. The B stars brainstorm to evolve off of the Main Sequence.
  4. Later 1 billion years (109 years), All of the B stars that are massive enough have gone supernova and the residuum have evolved into red giants. The A stars brainstorm to evolve off of the Main Sequence.
  5. After 5 billion years (5x109 years), The Thou stars begin to evolve off of the Main Sequence. The cherry giant co-operative is populated with some of the originally more massive stars. Some of the start red behemothic stars that formed have already become white dwarfs.
  6. After 10 billion years (1010 years), The OBAFG stars are all missing from the Main Sequence, the ruddy giant branch is very well populated, and there are also many white dwarfs. Only K & Grand stars remain on the Main Sequence.

What we see in the sequence is that as a cluster of stars ages, the acme of the Main Sequence disappears first. The illustration yous oft hear is that it is similar the wick of a candle—equally the cluster stars burn out, the Main Sequence gets shorter. Therefore, if y'all tin identify exactly what type of star is just now undergoing the transition from Main Sequence to ruddy giant (chosen the Principal Sequence Turn-Off), and if you know how long (theoretically) that it takes stars of that blazon to use up all of their hydrogen, you lot can estimate the age of that star. Now, because we assume that all of the stars in the cluster formed simultaneously, nosotros can presume that all stars in the cluster accept the aforementioned historic period equally the most massive star left on the Primary Sequence. Astronomers often utilize this technique of Main Sequence Turn-Off fitting to estimate the historic period of star clusters. The way this is washed in practice is the following:

  1. Astronomers utilize computer models to create a theoretical HR Diagram for a population of stars with a specific age, say 500 million years. Instead of plotting the individual points, they plot a line that goes through the points of all of the stars in the Hr diagram. Since this line indicates the positions of stars with a specific age, it is called an isochrone.
  2. Astronomers plot the observed colors and luminosities for the stars in a star cluster.
  3. You find the best match between a theoretical isochrone and the stars in your cluster, and that tells y'all the historic period of the cluster.

HR diagram with Main Sequence fits for open clusters of different ages based on the Main Sequence Turn-off point in each.

Figure 7.10: Hour diagram with Main Sequence fits for open up clusters of unlike ages

If yous compare the Hr diagrams for stages 1-three, these are very similar to the Hour diagrams for open clusters. The HR diagram for stage half-dozen appears to be very like to that of a globular cluster. Thus, we can conclude that open up clusters are young (usually a few tens of millions or hundreds of millions of years erstwhile), while globular clusters are very old (typically well-nigh 12-xiii billion years old). In the image higher up, you can come across a schematic 60 minutes diagram with plots of lines that represent the Primary Sequence for a number of open clusters. From the location of the Master Sequence Turn-Off, you tin see that NGC 2362 is the youngest, so h & χ Persei, and M67 is the oldest of the clusters.

This realization explains several of the other observations that we made of the differences between these two types of clusters. Since open clusters are immature, they have non had a hazard to movement very far from the location where they were built-in. Thus, there is likely to be leftover textile from the molecular clouds in which they formed nearby (which creates the reflection nebulae seen in the Pleiades). The intense radiation from the bright O & B stars in the open clusters tin ionize the nearby gas, creating emission nebulae nearby, as well. The light from an open cluster is dominated by the brightest stars in the cluster, which are O & B Master Sequence stars, since no red giants accept formed yet. Thus, open clusters should be quite blueish.

Since globular clusters are old, they are not constitute near the regions in which they formed. There is no gas in their vicinity. Even if at that place was, the stars in globular clusters exercise not emit much ultraviolet light capable of creating emission nebulae. Thus, we do not look to find emission nebulae surrounding globular clusters. There are no bluish Main Sequence stars left, and so the light from a globular cluster should be dominated by the brightest red giants, leading to their very red appearance.

Lastly, nosotros tin besides explain the departure in chemical composition between open cluster stars and globular cluster stars. Originally, all of the gas in the universe contained few elements heavier than helium. However, as nosotros learned in our study of stellar evolution, heavier elements are created in massive stars and dispersed when they get supernova. Therefore, as time goes on, later generations of stars should contain college and college concentrations of heavy elements. Since globular clusters are 12 billion years old, their atmospheres reflect the makeup of the primordial gas from which they formed. Since open clusters have formed relatively recently, they have 10-100 times more than heavy elements in their atmospheres.

One question that we accept not withal answered is why the Sun is so manifestly isolated. If all stars class out of molecular clouds that form many stars at once, why are there non several hundred stars nearby? The reason has something to do with the density differences between star clusters. Remember, open clusters look "fluffy. " That is, they are not very concentrated. Globular clusters, on the other hand, are very densely packed with stars. In open clusters, the gravitational pull of all the stars taken together is not stiff enough to keep the stars bound to the cluster. Over time, the individual stars in open clusters drift away, and the cluster dissolves. The gravitational pull past the cluster on the stars in a globular cluster is much stronger, and so these clusters are able to retain nearly of their stars for billions of years. It is likely that the Sunday did form as part of an open cluster, but since the Sun is now virtually 5 billion years quondam, it has long ago drifted away from the stars that formed out of the same deject.

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Source: https://www.e-education.psu.edu/astro801/content/l7_p6.html