![]() Probably the most iconic image ever produced by the Hubble Space Telescope is the image dubbed Pillars of Creation, showing a star forming region in the Eagle Nebula. Stars can also become too big to ever form a stable star and they blow themselves apart as soon as nuclear fusion starts, resulting in one or more large stars and/or new clouds from which stars can form. Very often proto-stars are blown apart before they can actually start nuclear fusion, so star formation is a hit-and-miss process. This process of star formation occurs in very dynamic and often violent conditions of turbulence and high energy radiation and is very hard to model. Most stars form in groups in the same region and thus will have similar age.ĪLMA images of proto stars. At this stage bi-polar jets can appear on both sides of the rotation axis of the proto-star. Once this compression occurs, gravity can cause further contraction which results in rotating clouds of compressed gas called proto-stars, in which the internal pressure slows but cannot prevent further collapse under gravity. On a grand scale this can happen when neighbouring galaxies interact and massive “ star burst regions” are formed, often as a result of a galaxy merger. This can be the result of a collision of different clouds, or be due to the shock wave of a supernova explosion (see below) or strong radiation of a nearby young massive star. The process of star formation begins when a region of gas and dust becomes gravitationally unstable because a part of the cloud compacts and increases in pressure. Under influence of high-energy radiation from young hot stars, the gas can become ionised and it then emits light in various ways, forming emission nebulae. Generally these inter-stellar regions are cold enough for molecules to exist. The dust particles are microscopic and are largely composed of Carbon and Silicates. The gas is predominantly Hydrogen, the most abundant element in the Universe, but it also contains other gasses. Regions called Giant Molecular Clouds (GMC’s) can extend over hundreds of light years and contain as much material as millions of Suns. Credit and further info hereGalaxies, including our own Milky Way galaxy, contain vast amounts of gas and dust in inter-stellar space in the disk region. Herschel telescope image of a star forming region in Cassiopea. This module will also illustrate how stars are formed from the remains of previous stars and how the Universe can be considered as a giant "recycle factory".īefore continuing this EBook, it is advisable to first read our EBook “Stellar Radiation” to learn about the Electro-Magnetic spectrum, spectroscopy and the Hertzsprung-Russell diagram. The material from which stars are made never disappears. In this module we will discuss how stars are born, live their life - some live much shorter than others - and how there are different ways in which they end their existence. Modern observations, in particular in wavelengths outside the visible spectrum and also from observatories in space, have contributed very much to our understanding of stellar evolution, although research in stellar evolution remains very much at the forefront of modern astrophysics. While we cannot wait to see the evolution of one star, we can study many stars in various stages of their evolution, and thus learn about the whole sequence. ![]() A human life span, and in some cases even the existence of the human race as a whole, is too short to actually observe dynamic processes in the Universe. ![]() We need to think at another time scale to understand that everything moves in orbits and that stars come and go a time scale of evolution. Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0)Ĭompared to the human life span, everything in the Universe seems stationary and constant. Our EBook Stellar Radiation (spectra, HR-diagram) In this EBook we discuss how stars form and evolve throughout their lifetime.Īstronomy, Stellar evolution, EM-spectrum, spectral lines, star formation, molecular cloud, star burst, proto-star, nucleosynthesis, fusion, Orion nebula, Crab nebula, multi-wavelength, plasma, ionisation, nucleus, electron, strong nuclear force, proton, neutron, proton-proton cycle, CNO cycle, Hertzsprung-Russell diagram, main sequence, red dwarf, giant, red giant, super giant, blue giant, white dwarf, core collapse, supernova, neutron star, black hole, luminosity, spectral class, brown dwarf, black dwarf, shell fusion, triple-alpha process, planetary nebula, electron degeneracy, neutron degeneracy, Chandrasekhar limit, Pauli exclusion principle, hydrogen, helium, carbon, oxygen, neon, magnesium, silicon, sulphur, iron, pulsar, event horizon, schwarzschild radius, type Ia, type Ib, type Ic, type II, light curve, metallicity, thermal runaway, horizontal branch, asymptotic giant branch, Gaia spacecraft, cosmic alchemy, cosmic ray fission.
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