le>HR Diagram
Hertzsprung-Russell Diagram:Readings: Schneider & Arny: devices 50, 58
In 1905, Danish astronomer Einar Hertzsprung, and independently Americanastronomer Henry Norris Russell, noticed that the luminosity the starsdecreased native spectral form O to M. They occurred the an approach ofplotting absolute magnitude for a star versus its spectral kind to lookfor family members of stellar type.These diagrams, dubbed the Hertzsprung-Russell or HR diagrams, plotluminosity in solar devices on the Y axis and also stellar temperature on the Xaxis, as presented below.

You are watching: How do white dwarfs compare with supergiants, in terms of temperature and luminosity?

*
Notice the the scales space not linear. Warm stars inhabit the left handside that the diagram, cool stars the appropriate hand side. Shining stars atthe top, faint stars in ~ the bottom. Our sunlight is a fairly average starand sits close to the middle.A plot the the nearest stars ~ above the HR chart is shown below:
*
Most stars in the solar ar are fainter and also cooler than theSun. Over there are additionally a handful of stars which are red and an extremely bright(called red supergiants) and also a couple of stars that space hot, but an extremely faint(called white dwarfs). We will see in a later on lecture that starsbegin your life ~ above the key sequence then evolve to different partsof the HR diagram.Most the the stars in the over diagram fall on a curve that we contact themain sequence. This is a an ar where most normal stars occur. Normal,in astronomy terms, method that they are young (a few billion year old)and burn hydrogen in your cores. Together time walk on, star readjust orevolve together the physics in your cores change. However for many of thelifetime of a star it sit somewhere top top the main sequence.
*
Several regions of the HR diagram have been offered names, return starscan occupy any portion. The brightest stars are dubbed supergiants.Star clusters room rich in stars simply off the key sequence dubbed redgiants. Key sequence stars are referred to as dwarfs. And the faint, warm stars arecalled white dwarfs.
*
The spectral classification types were much more accurate then attempts to measure the temperatureof a star by its color. So frequently the temperature range on the horizontal axis is replaced byspectral types, OBAFGKM. This had the advantage of being much more linear 보다 temperature (nicelyspaces letters) and also contained an ext information about the star than just its temperature (thestate the its atoms).The HR diagram i do not care a calculating tool when one realizes that temperature, luminosity andsize (radius) are all associated by Stefan-Boltzmann"s law. The traditional Stefan-Boltzmann regulation isfor allude sources, an idealized case. Real objects have size, which way surface area. Largeobjects cool faster (emit power faster) than small objects, so there must be part correlationwith radius. Because that stars, the luminosity, temperature and radius are attached by an development ofStefan-Boltzmann"s regulation that says:L = 4πR2σT4This equation have the right to be expressing in terms of solar units such that:L/Lo =(R/Ro)2(T/To)4where Lo, Ro and also To room the luminosity, radius and surfacetemperature that the Sun.Knowing indigenous laboratory dimensions that Stefan-Boltzmann"s constant is 5.67x10-8allows one to calculate the luminosity of a star in devices of watt (like a irradiate bulb) if weknow the radius of the star in meters and also the temperature in kelvins. For example, the sun is6.96x108 meter in radius and also has a surface ar temperature that 5780K. Therefore, itsluminosity is 3.84x1026 watts.On a log-log plot, the R squared ax in the above equations is astraight heat on one HR diagram. This means that on a HR diagram, astar"s dimension is easy to check out off as soon as its luminosity and color areknown.
*
The HR chart is a crucial tool in tracing the advancement of stars. Starsbegin your life on the key sequence, but then evolve off right into redgiant phase and also supergiant phase prior to dying as white dwarfs or somemore violent endpoint.Thermonuclear Fusion:Energy generation is the heart of stars. It provides the energy thatwe see as light, and it likewise supplies the heat and also pressure thatsupports a stars" structure. The power resource for stars isthermonuclear fusion.Normally, particles with like charges (positive-positive ornegative-negative) repel each other, this is called electrostaticrepulsion. Yet at temperatures above 15 million degrees K, themotions of protons room high enough to get over the electrostaticforces and the nuclei deserve to ``fuse"" making use of the solid force. The major output indigenous a thermonuclear reactions room photons in theform the gamma-rays, yet a huge number of other particles areproduced as well.
*
The simplest combination reaction is the proton-protonchain, common in all main sequence stars. It has actually the following fourstages:
*
*
*
*
All the gamma-ray photons space scattered many, numerous times together theyleave the stellar core. Every scattering exchanges energy so the thephotons convert into visible, UV, IR and radio photons, too ashigh energy ones, creating a thermal, Planck curve, spectrum.The Neutrino Problem:During the proton-proton chain, number of different types of matter arecreated from energy and many gamma-ray photons room released. However, dueto the high densities in the main point of a star, all these objects space trappedin the center and, thus, we can not `see" what go on within a star.However, plenty of neutrinos are additionally created, and also the neutrino is a veryspecial kind of fundamental particle v no electrical charge, a very smallmass, and also one-half unit that spin. Neutrinos belong to the family ofparticles dubbed leptons, which room not subject to the solid nuclearforce, therefore not quit by the issue in the core of a star.
*
Neutrinos space the most penetrating that subatomic particles due to the fact that theyreact with matter only with the weak interaction. Neutrinos perform notcause ionization, due to the fact that they room not electrically charged. Just 1 in 10billion, traveling through issue a distance equal to the Earth"sdiameter, reacts v a proton or neutron. However, since neutrinos areweakly interacting, lock are also just as complicated to detect. Ours bestneutrino `telescopes" are large tanks of water hidden deep undergroundsuch as the SuperKamiokande in Japan. Water has lots of protons in the type ofhydrogen atoms.
*
Neutrinos from a supernova explosion take trip at or verynear the rate of light and also carry a the majority of energy. On rare occasions, aneutrino will certainly hit a proton in the tank that water (the an ext water, thegreater the chance). This collision will create a positron i m sorry recoils v suchhigh rate that that emits a brief flash the light recognized as Cerenkov radiation. Thedetector tank that water is hidden deep in the earth to eliminate cosmicrays and other interaction that would distort the detection of theneutrinos. Only neutrinos have the right to reach to such depths.

See more: How Long Is Sliced Hard Salami Good For In The Fridge : Top Full Guide 2021

*
Even despite neutrinos are so difficult to stop, there are so plenty of of them thatit is possible to style detectors. Unfortunately, the detectors detectonly a portion of the number neutrinos they should. This was a majorsource of concern and also confusion because that years, and also was described as the"neutrino problem," or "the difficulty with solar neutrinos." What go thismean? no one knew for a lengthy time. It could have meant that our ideasabout the proton-proton chain need revising, or that there is part unknownmechanism at job-related that absorbs plenty of of the neutrinos prior to they reach theEarth. It stayed a an enig until relatively recently once astronomers andphysicists said that the neutrinos may change their characteristicsas castle travel towards Earth. So once they acquired to the detectors ~ above Earth,many the the neutrinos had actually adjusted into a different type otherthan what the detectors to be looking for. Solid evidence because that this wasannounced in June, 2001, and it appears that the "neutrino problem" hasbeen solve.
*
*