Dwarfs: The End for Stars

Dwarfs: The End for Stars

Felicia M. Echavarria, author 20053607 ASTR 1402-03 John Faust, instructor

Abstract:

An expose of the the end states of low mass stars. (used by permission of the author) Throughout the billions of years our galaxy has been around, millions of stars have been born and have grown into massive, gaseous, objects. When we look at a star with the naked eye, it seems as though it is nothing but a tiny sparkle smaller than our fingernail. When in reality, it is a huge, burning ball of gas thousands of times bigger than earth itself. But just like the human race, and everything else that lives on earth, when there is life there is death. Slowly but surely a star loses its life and luminosity and becomes what we call a dwarf star. White Dwarf There are about 5 different types of dwarf stars, each distinguished by their name, color, and mass. The White Dwarf, which is the most known dwarf, was first discovered in 1844 by Friedrich Bessel. He noticed an object being orbited by Sirius and later discovered it to be a White Dwarf. It is a star that once had low or medium mass. They are usually very small and hard to be detected. The outer layers of the White Dwarf usually only contain helium and hydrogen. It is said that our very own Sun will eventually become a White Dwarf within the next 5 billion years. Yellow Dwarf Before the White Dwarf however, comes what we call a Yellow Dwarf. A Yellow Dwarf is usually bigger than most stars with a mass of 1.9891 X 10^30 kg, a mass similar to the Sun’s. It is a G type main sequence star which means it lies towards the center of the H-R Diagram and has a surface temperature of or between 5,000 and 6,000 K. A Yellow Dwarf will get brighter by each year that passes and actually has a hotter core than most other dwarfs due to hydrogen fusing into helium. Because of this, the core of the star becomes hotter and hotter and contracts until its own energy overpowers its own gravity. Once that happens, the star expands, becomes a Red Giant then eventually a White Dwarf. Our very own Sun is actually considered a Yellow Dwarf. It has the same characteristics, similar mass, and lies on the Main Sequence of the H-R Diagram. Brown Dwarf Unlike the Yellow Dwarf, the Brown Dwarf is actually cool and dim with a temperature between 800 and 1,880 degrees. As a matter of fact Brown Dwarfs are actually too cool to emit any visible light at all. They are usually found in clouds of dust and gas just like stars. Brown In the image above a White Dwarf is compared to one of our planets. You can sort of get an idea of the size and brightness of a dwarf star. Image: http://i3a12c1.deviantart.com/art/white-dwarf-2-0-164623658 A Yellow Dwarf is located on the main sequence somewhere between the sun and Bernard’s Star. It has a surface temperature between 5,000 and 6,000 K. Image: http://death-of-the-sun.e-monsite.com/pages/the-sun/4- yellow-dwarf-and-h-r-diagram-solar-panic.html In the image above you can see just exactly how big a Brown Dwarf actually is compared to our very own Earth and planet Jupiter. Image: http://www.centauri-dreams.org/?p=33783 Dwarfs are actually too big to be planets and too small to be stars but yet have twice the mass of planet Jupiter. In the universe there are as many Brown Dwarfs as there are stars. Brown Dwarfs were first discovered in 1995 and could only be seen with an infrared telescope, even to this day. The reason Brown Dwarfs can only be seen with an infrared telescope is because infrared telescopes are the only type of telescopes that can see through all the cloudy dusty clusters of the universe where Brown Dwarfs usually are. Black Dwarf A Black Dwarf is the final stage of the stellar evolution. Even though there is no actual proof that Black Dwarfs do exist and they are said to be theoretical, there still are slim chances that they could exist. A Black Dwarf is said to be one that emits no light or heat and is simply just a “dead star”. However a Black Dwarf still retains its mass. A Black Dwarf is the stage that comes after a White Dwarf, however scientists have concluded that a White Dwarf does take billions of years to lose its total heat and in order to become a Black Dwarf its temperature would need to be a lot lower than 3000 K, which is the lowest temperature recorded of a White Dwarf today. Red Dwarf The smallest of all stars, weighing only 7.5 to about 50 percent the mass of our very own Sun and the dimmest is the one we call “Red Dwarf”. A Red Dwarf is not visible to the naked eye. They form and lie just like many of the other stars on the main sequence. As a matter of fact, one of the closest stars to the Sun, Proxima Centauri, is a Red Dwarf itself. Their temperature is not very high either, burning at only 5000 K. Out of our whole galaxy, Red Dwarfs have become In the image above is an example of what a Black Dwarf is said to look like. Image: http://www.glogster.com/mefivecent/white-dwarf-blackdwarf/g-6liq7ipeuoeo2g3oa9froa0 In the figure above you can see with the temperature chart, an estimation of a Red Dwarf’s temperature and color. Image: http://pics-about-space.com/red-dwarf-startemperature?p=2 Above is an image of Proxima Centauri, a Red Dwarf. Red Dwarfs are the smallest stars in our universe. In the image above you can see a Red Dwarf being compared to our Sun as well as Alpha Centauri A and Alpha Centauri B. Image: http://www.gravitywarpdrive.com/Zeta_2_Reticuli.htm the most common and actually make up the majority of the stars in our galaxy. Many of them are not stationed alone, they have been found in between different planets, surrounded. They are also very different from other stars when it comes to life span. Since they don’t burn hydrogen like most other stars their lifespan is actually a lot longer. They can actually survive trillions of years. But like many other dwarf stars, a Red Dwarf will eventually become a White Dwarf. Thanks to technology now we are able to learn more and become more familiar with dwarf stars. We are able to learn the many different colors, masses, and temperatures they carry. As well as their names and reasons behind them. It is amazing how many of these dwarf stars have been around for hundreds of years and will continue for hundreds more. Dwarf stars are so unique because even though they are considered the ending stage for a star, they still contain so much mass, heat, light, and energy. With our universe constantly expanding, year after year, we can only imagine how many more dwarf stars will reside within our solar system and universe overall. The image above shows you the stages of a star’s life and how the paths for a red giant and red supergiant are very different and have different outcomes. Image: https://socratic.org/questions/what-is-the-life-cycle-of-a-star-from-birth-to-death In this figure you are able to see the comparison of dwarf stars and the stages of human life. Image: http://www.slideshare.net/dolandese/life-cycle-of-stars-7194842 Resources Used – “What is a Yellow Dwarf?” http://www.wisegeek.com/what-is-a-yellow-dwarf.htm – White Dwarf http://imagine.gsfc.nasa.gov/science/objects/dwarfs1.html – Brown Dwarf http://coolcosmos.ipac.caltech.edu/cosmic_classroom/cosmic_reference/brown_dwarfs.html – Yellow Dwarf http://planetfacts.org/yellow-dwarf/ – Red Dwarf http://www.space.com/23772-red-dwarf-stars.html – Black Dwarf http://www.space.com/23799-black-dwarfs.html – http://www.universetoday.com/41096/black-dwarf/ – Title page photo http://www.skyandtelescope.com/astronomy-news/white-dwarf-stars-withhiccups-2109201523/

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