Astronomy Explain How the Hertzsprung-Russell

Astronomy

Explain how the Hertzsprung-Russell diagram is constructed of the four main groupings of stars. Identify characteristics of the four main groupings of stars on the diagram. The H-R Diagram shows the similarities among stars in the sky. The diagram is used for understanding the life cycle of the stars. The diagram effectively classifies or categorizes the stars by certain characteristics. The characteristics include luminosity, spectral type, color, temperature, and evolutionary stage.

"A Star is Born!" In a step-by-step fashion, reconstruct the birth of a star. In your answer, include interstellar medium, protostar, and how stellar equilibrium is finally reached. A star is born after it is formed from the condensation of a hot cloud of gas and dust in space. The cloud gets very hot and dense and this inspires fusion to occur (fusion is the combination of hydrogen atoms into helium atoms). This produces starlight. It depends on the size of the cloud as to whether one star, a binary star, or a cluster of stars is formed.

3. "A Star Dies!" Using the same technique you applied in question 2 above, trace the elements in the demise of stars of low stellar mass, those of medium stellar mass, and those that are very massive. Once a star's hydrogen starts to deplete, it begins to die. In other words, a star can only last as long as it has hydrogen to fuel it. The star is in the last stages of life once its hydrogen starts to run low. The next stage is different for every star depending on its size. For example, an average-sized star such as the sun, will spend its last time in life as a red giant. The star will look reddish in color and it will grow larger than its original size. The sun, which is average in size, will effectively "bloat" in size. Once it is a red giant, it blows off its gases and then it will eventually simply collapse. The star, our sun, will then fade and turn into a white dwarf, the inner core of the star. The white dwarf will eventually cool down and turn into a black dwarf, giving off no light or heat. However, because the cooling off process takes so long, it is believed that no star has ever reached this phase in its life cycle.

A red dwarf or a smaller mass star dies in the same way as an average-sized star like our sun, except that it does not turn into a red giant and it takes billions of years more to turn into a white dwarf and then a black dwarf.

A very large star -- a blue giant -- dies like other stars, or else it can go supernova.

4. Explain how Type I and Type II supernovae occur. When a blue giant is dying, it gets very hot and bright and turns into a super giant. It then collapses -- but its collapse is inward -- as it explodes. This is called a supernova. Supernovae can be categorized as Type I or Type II depending on the shape of their light curves and the nature of their spectra (Nave). Supernovae are categorized as Type I if their light curves exhibit sharp maxima and then die away gradually and rather smoothly. The maxima may be about 10 million solar luminosities (Nave). The model for the initiation of Type I supernovae is the detonation of a carbon white dwarf when it collapses under the pressure of electron degeneracy (Nave). Type II supernovae have less sharp peaks at maxima and peak at about 1 billion solar luminosities. They die away more sharply than Type I supernovae. They are modeled as implosion-explosion events of a massive star. They exhibit characteristic plateau in their light curves a few months after initiation (Nave).

1. Describe how Harlow-Shapley determined that the sun was not at the center of our galaxy. In 1915, Harlow-Shapley used Cepheid variables found in globular clusters to estimate the distance to each cluster. He believed that humans are limited in the stars that we can see, which has duped us into thinking that we are the center of everything. However, the distribution of globular clusters shows that our star system is much more expansive than we could ever imagine. He concluded that we our located near the edge of the system, not the center. He used the relation between the period of Cepheid and their observed brightness to map the relative distances of clusters from us and from each other. He noticed that they were randomly distributed both above and below the plane of the Milky Way and looked to be concentrated in one area near the constellation Sagittarius. He argued that this kind of distribution would make sense if the galaxy had the shape of a flattened disk with the clusters grouped around the galactic center. This meant that the solar system be displaced from its accepted central position by a significant distance.

2. Compare the differences between galactic and globular clusters. One major difference between galactic and globular clusters can be viewed easily with the aid of a telescope. Galactic clusters is a cluster of young stores that aren't necessarily close -- rather, the cluster is dissipated; globular clusters are the opposite; they are clusters of old stars densely and closely packed together into a region of space, which is a spherical shape.

3. How does the use of H. II regions to find a galaxy's distance differ from the use of Cepheid variables? Cepheid variable are bright stars that are variable. Their period is linked to their absolute luminosity. Once the absolute luminosity is known, the distance can be found by comparison with the apparent luminosity. H II regions are regions of ionized hydrogen. They are luminous because they are regions where there is an active forming of stars in the galaxy. There is an empirical association between a galaxy's absolute magnitude and the geometrical size of the brightest H. II region.

4. How does the cluster method tell us the mass of galaxies? The cluster method isn't about measuring mass. The cluster method is more about finding distances, not mass (Soper).

5. What evidence do we have that the center of our galaxy is a powerful source of energy? The evidence that we have to show that the center of our galaxy is a powerful source of energy is a whirlpool known as an accretion disk. There is energy both radio and infrared that comes from that direction. The energy is coming from the swirling whirlpool of hot gas and dust falling into it.

6. Our galaxy is not a radio galaxy, but it does emit radio energy. Explain where this radio energy comes from. Radio galaxies are simply one aspect of phenomenon known as active galaxies. They are like regular galaxies but the black hole at their centers feeds on material. This is what happens in our galaxy. When too much material piles up, it forms an accretion disk around the black hole and it becomes so hot that it gives off a lot of radiation (Cain).

7. Why should we expect quasars to be small? How small? We should expect them to be small because they are so far away -- but they are so bright. In actuality, quasars are probably bigger than regular stars.

8. What observational evidence do we have that quasars are at the centers of very distant galaxies? The evidence we have is that the energy that comes out of them changes within a few days -- sometimes less. This shows that this objects is small enough span less than a few light days. The energy that they produce is double that of the whole galaxy.

Write a three 3-page paper about some type of current research that is going on in astronomy today. The search for planets outside of our solar system is a search that is gaining importance every day. While Kepler's spacecraft has located more than 1,200 planet candidates, confirming them is something that still remains a problem for Kepler (Space Daily). In some cases, an eclipsing binary star can mimic the shallow dimming due to a planet crossing in front of its star (Space Daily). Because of this ground-based measurements are needed in order to confirm an orbiting world by spotting the gravitation wobbles it induces in its host star -- a method known as radial velocity (Space Daily).

Science Daily reports that NASA's Kepler mission has found its first Earth-size planet candidates and its first candidates in the habitable zone, a region where liquid water could exist on a planet's surface (Science Daily). The research into finding habitable planets is interesting because we have gone from a generation that was interested in extraterrestrial planets (more of a mainstay of science fiction) to the present where we are searching for habitable planets where humans could potentially live.

The Kepler mission has found several new hundred new planet candidates. To date then, the number of potential candidates has increased to 1,235. Of those 1,235, 68 are estimated to be Earth-size; 288 are super Earth-size; 662 are Neptune-size; 165 are the size of Jupiter, and 19 are larger than Jupiter (Science Daily).

Of the 54 planet candidates that have been found in the habitable zone, five are near Earth-size. The other 49 left in the habitable zone range from super-Earth-size (up to twice the size of the Earth) -- to larger than Jupiter (Science Daily). All of these findings came from observations between May 12 to September 17, 2009 of more than 156,000 stars in Kepler's view (approximately 1/400 of the sky) (Science Daily).

This research has shown that the fact that so many candidates for planets have been found in such a tiny fraction of the sky (1/400) suggests that there are more planets orbiting sun-like stars in our galaxy -- many more than we can imagine (Science Daily). William Borucki of NASA's Ames Research Center in Moffett Field, California believes that some of these planet candidates in the habitable zone could potentially have moons with liquid water (Science Daily).

A new instrument called HARPS-North will help complement Kepler by helping to confirm and characterize Kepler's planetary Candidates (SIFY). HARPS stands for "High-Accuracy Radial velocity Planet Searcher" and it was created to detect the tiny radial-velocity signal induced by planets as small as Earth (SIFY). The Kepler mission gives the size of the planet based on light it blocks when it moves in front of stars, but planets need to have their planetary masses measured so that density can be measured. This will make it so rocky planets and water worlds can be identified -- as opposed to those that have atmospheres of hydrogen and helium (SIFY).

HARPS-North will look at the most interesting targets that Kepler finds. They will work as partners to find worlds that are similar to Earth and might be able to support life like human life (SIFY). A spectrograph operates by splitting the light from a star into its component wavelengths or colors (kind of like a prism) (Space Daily). Chemical elements absorb light of specific colors, leaving dark lines in the star's spectrum. Those lines change position slightly because of the Doppler shift created by the gravitation tug of an orbiting planet on its star (Science Daily).

1. Briefly relate several possible courses for the future of the universe and the kinds of observation that would be necessary to resolve the issue. Will the universe last forever or will it end? There is the possibility that the universe will come to an end in the opposite way of which it started. The opposite of the Big Bang is called the Big Crunch. The Big Crunch would happen when there is enough matter in the Universe that the gravitational forces will stop its expansion. Gravity will then cause the universe to change directions and begin to collapse under its own weight. It could even collapse into a giant black hole. There are some that believe if the universe did collapse into a giant black hole, it could then turn into another Big Bang. In this way, the universe could, potentially, live forever, but it would simply be going through these phases of contraction and expansion forever.

2. Outline the stellar nebula theory, and explain how the characteristic properties of the solar system provide evidence that supports that theory. The stellar nebula theory is the most widely used theory when it comes to explaining how our solar system was formed and how it evolved. It was first just applied to our own solar system, but it is now applied to the entire universe. According to the theory, stars form in massive and dense clouds of molecular hydrogen. The clouds are unstable gravitationally speaking and matter merges into smaller and more dense clumps inside. The clouds then collapse and they form stars. This can be the beginning of planets when the situation is right. Planets are believed to form thus as a direct and natural result of star formation.