Astronomy - PSCI 101 - ASR
Professor: Edward J. Stander
The age of the universe
Throughout modern universe astronomers can estimate the age of the universe with all different bodies that creates the universe. The universe is 13.7 billion years old and the big bang happen around 10 to 20 billion years ago by scientist estimation. The way astronomers figured out the solution was figuring out the age of the cluster stars, the age of the old white dwarf stars, the chemical elements, nebula, and finding the rate of the universe using mathematics with the big bang. There are ways astronomers can figure out the ages of the stars by studying the “globular clusters.” Another way to estimate the age of the universe is the “Hubble constant”.
The globular clusters are the oldest surviving stellar subsystems in galaxies which were formed 13 to 15 billion years ago. In 1993: there where 125 clusters known in the galaxy. The cluster has the highest concentration of stars close to its own center. The average star density in a globular cluster is 0.4 stars per cubic parsec. So the star density can increase from 100 to 1000 per cubic parsec. But in the center of the clusters there is a lot of space between certain stars. The globular clusters are the first ones to use up the hydrogen in their core and evolve of the main sequence becoming the red giants. Looking at clusters of stars (groups of stars all born at the same time that are at the same distance from the earth). When stars are in the longest stage of their lives “burning hydrogen” scientist can put them on a plot of temperature versus luminosity (how bright they are) and scientists found they all fall in a straight line (they call it the "main sequence"). Based on the history of stars, they know how long each type of star stays on the main sequence. When scientists observe a cluster of stars, they can see all kinds of stars filling out the line call the main sequence. They also can see what types of stars have already left the main sequence in old clusters to find an upper limit for the age of the cluster and also the universe.
The Hubble constant is the estimation of the size and age of the universe. The number is in constant debate, it indicates the rate at which the universe is expanding, from the point of the big bang. The Hubble Constant is represented by the mathematical equation, HO = v/d, where v is the galaxy's radial outward velocity, d is the galaxy's distance from Earth, and HO is the current value of the Hubble Constant.
A nebula is an interstellar cloud in outer space that is made up of dust, hydrogen and helium gas, and plasma. It is formed when portions of the interstellar medium collapse and clump together due to the gravitational attraction of the particles that comprise them. There are all kinds of different nebula body for example; planetary nebula results from the death of a star, when a star has burned through so much material that it can no longer sustain its own fusion reactions, the star's gravity causes it to collapse. As the star collapses, its interior heats up. The heating of the interior produces a stellar wind that lasts for a few thousand years and blows away the outer layers of the star. When the outer layers have blown away, the remaining core remnant heats the gases, which are now far from the star, and causes them to glow.
White dwarfs are the burned out cores of collapsed stars. Like dying embers, slowly cool and fade away. They are the remnants of low mass stars, among the dimmest objects observable in the Universe. They are low to medium “less than the ten solar mass” Main Sequence stars which have burned through their reservoirs of both hydrogen and helium, passed through the giant phase, were not hot enough to ignite their carbon, puffed off their outer layers to form colorful planetary nebula, and then collapsed and cooled into small glowing coals. It has no nuclear hydrogen