The Life Cycle of Stars Complete Presentation

Complete PPT on The Life Cycle of Stars

1. The Life Cycles of Stars Harshita Agarwal -A002 Svara Dadhe -A012 Pari Desai-A013 Shreyas Gupta -A022

2. Introduction Stars, the celestial giants that illuminate our universe, undergo fascinating life cycles, evolving from birth to death in a cosmic dance of energy and matter. In this presentation, we will embark on a journey through these stages, exploring the birth, evolution, and ultimate fate of stars.

3. Birth Giant Gas Cloud Formation:Stars are born frommassive clouds of gas and dust, which fragment and give birth to multiple stars. Protostar Formation: Protostars are the pre-stage of a star, forming within molecular clouds and surrounded by dust, striving to achieve equilibrium before initiating nuclear fusion. T-Tauri Phase: T-Tauri stars are young, pre-main-sequence stars less than about ten million years old, offering insights into the early stages of stellar and planetary formation.

4. Stars form from giant clouds of gas and dust. Massive stars are born from massive clouds that fragment, leading to the birth of multiple stars. Different physical mechanisms, such as turbulent gas motion or magnetic fields, may influence this fragmentation process. Star formation occurs on a hierarchy of different levels, starting from giant molecular clouds to denser clumps where individual stars form. Giant Gas cloud

5. Protostars Protostars are the pre-stage of a star, resembling a baby star. They form within stellar nurseries, which are molecular clouds where stars form. Protostars are difficult to observe in visible light as they are surrounded by dust. They have a protostellar disk spinning around them, which may coalesce into planetary systems. Protostars strive to gain equilibrium between internal forces and gravity. The protostar phase lasts for about 100,000 years and ends when core temperature exceeds 10 million K, initiating hydrogen fusion.

6. T-Tauri Phase After the protostar phase, stellar winds and radiation clear the surrounding envelope of gas and dust. The T-Tauri phase is when the surrounding envelope has cleared. T-Tauri stars are pre-main-sequence stars less than about ten million years old. They are promising candidates for studying the early lives of stars and planets. The phase ends when a star of 0.5 solar masses or larger develops a radiative zone or when a smaller star begins nuclear fusion on the main sequence.

7. . Low & Medium Mass Star 1. Low mass stars undergo hydrogen-to-helium fusion via the proton-proton chain for billions of years. 2. They often have convection zones, with some showing activity cycles akin to the Sun's sunspot cycle. 3. Stars with deep convection zones and fast rotation can produce X-ray flares due to twisted magnetic fields. 4. A star's lifetime is related to its mass divided by its luminosity, and luminosity is roughly proportional to the 3.5 power of its mass.

8. Red Giant 1. Red giants are luminous giant stars in late stellar evolution, with masses ranging from 0.3 to 8 solar masses. 2. They have large radii and low surface temperatures, appearing yellow-white to reddish-orange. 3. When hydrogen fusion stops in the core, gravity collapses it, leading to outer layers expanding and increasing luminosity, transforming the star into a red giant. 4. Helium fusion in the core causes a helium flash, followed by the formation of a helium fusion shell around a carbon core, sustaining the star as a red giant for millions of years.

9. Planetary Nebulae 1. Planetary nebulae form when dying stars eject their outer layers, leaving behind a hot core that emits ultraviolet radiation. 2. The ionized gas in the expanding shell of a planetary nebula glows brightly, creating a luminous cloud. 3. Planetary nebulae are relatively common in the galaxy, with an estimated 20,000 to 50,000 present. 4. They have various shapes, including round compact appearances, and are relatively short-lived phenomena in stellar evolution.

10. 1. A white dwarf is a compact star. Gravitation has pulled the atoms close together, and taken off their electrons. 2. White Dwarfs are incredibly dense, with masses comparable to that of the Sun but compressed into a volume roughly the size of Earth. 3. The material in a white dwarf no longer undergoes fusion reactions, so the star has no source of energy. It is not supported by the heat of fusion against gravitational collapse. 4. White Dwarfs are often surrounded by a shell of gas that was expelled during the star's final stages of evolution, which can form a beautiful planetary nebula. White Dwarf

11. 1. A black dwarf star is a hypothetical object that could exist in the distant future of the universe. It is the final stage in the evolution of a white dwarf star. 2. As a white dwarf cools down over trillions of years, it would eventually reach a temperature where it no longer emits light or heat become a black dwarf. 3. As this process takes much longer than the current age of the universe, no black dwarfs are thought to exist yet, and none have been observed. 4. Black dwarfs are theoretical objects that represent the ultimate fate of stars like the Sun. Black Dwarf

12. . High & Massive Mass Star 1.High-mass stars form from the gravitational collapse of large molecular clouds of gas and dust. 2. They undergo several stages of nuclear fusion, forming progressively heavier elements in their cores 3. When a high-mass star exhausts its nuclear fuel, it can undergo a supernova explosion, where the outer layers are ejected into space, leaving behind a dense core. 4. They produce and distribute heavy elements (such as carbon, oxygen, and iron) into space through their stellar winds and supernova explosions, enriching the interstellar medium

13. Red Supergiant 1. A red supergiant is a type of star that is in a late stage of its evolution. These stars are massive, with masses between about 8 and 40 times that of the Sun. 2. Red supergiant are characterized by their cool surface temperatures, which cause them to emit most of their light in the red part of the spectrum. 3. They are also very luminous, with some red supergiants shining hundreds of thousands of times more brightly than the Sun. 4. One of the most famous red supergiants is Betelgeuse, which is located in the constellation Orion

14. Supernova 1. Supernovae are powerful explosions occurring in the last stages of massive stars or triggered white dwarf fusion. 2. They form neutron stars, black holes, or diffuse nebulae, with peak luminosity comparable to entire galaxies. 3. Supernovae create heavy elements through fusion, releasing tremendous energy, radio waves, X-rays, cosmic rays, and gamma-ray bursts. 4. Supernova remnants expand, releasing heavier elements into the interstellar medium before dissolving.

15. Black Hole 1. Black holes are regions of spacetime with intense gravity that nothing, including light, can escape from. 2. They form when massive stars collapse, and supermassive black holes can grow by absorbing mass or merging with other black holes. 3. Black holes have an event horizon, beyond which nothing can escape, and they emit Hawking radiation. 4. Their presence can be inferred through interactions with surrounding matter, such as forming accretion disks or affecting the orbits of nearby stars.

16. Neutron Star 1. Neutron stars are the collapsed cores of massive supergiant stars, typically with a mass of 10-25 solar masses. 2. They are extremely dense, with a radius of about 10 kilometers and a mass of about 1.4 solar masses. 3. Neutron stars form from supernova explosions and gravitational collapse, compressing the core to atomic nuclei density. 4. They can evolve further through collision or accretion, and some types include pulsars with bright X-ray hot spots and magnetars with exceptionally strong magnetic fields.

17. Thank you very much!