Contenu connexe
Stars
- 4. Solar System Milky Way Galaxy Local Group of galaxies Virgo Supercluster
- 6. Open Cluster Globular Cluster
- 7. binary stars: two stars bound by gravity and orbiting each other around their center of gravity (double star)
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- 44. Small Medium Large Red Dwarf Sun-like star Blue Giant
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Notes de l'éditeur
- So lets go back to that exam question, and our overall structure for the Universe. I am warning you now, I am going to ask you this question on EVERY exam. This is the structure of the entire Universe, this is everything we will be learning about in this class. If you leave learning one thing, I want you to be able to fill out this chart, AND to understand what it means.What have we talked about so far. Last week we talked about the large scale structure of the Universe, the Virgo Supercluster, the Local Group of Galaxies, and the Milky Way. Where are the stars in this picture? They make up the galaxies. Here is one of them right here! The Sun. The Sun is a star.
- So let’s zoom in on a galaxy and take a look at some stars. We are going to spend the whole day learning about stars.
- These are the two kinds of star clusters. Globular and Open.
- Most of the stars in the sky have at least one companion. We call systems of two stars, binary systems. binary stars: multiple systems bound by gravity and orbiting each other around their center of mass (double star)
- Nebul-nube
- after it has fragmented from a interstellar gas cloud but before it has collapsed sufficiently for nuclear fusion reactions to begin. It may last from 100,000 to 10 million years, depending on the mass of the star. A protostar is surrounded by a dense cocoon of gas and dust that blocks visible light, but allows through large amounts of far infrared and microwave radiation. Protostars glow because of gravitational energy, as the matter collapses, it releases energy, making the star hot and glow.
- Eventually the star gets hot enough to “turn on”…Now wouldn’t it be nice if we had a star super close by, so we could study it in more detail?
- We do. We have star, a mere 93,000,000 miles away. That’s nothing in cosmic distances. If we were living on a peppercorn, that would only be 33 meters away. We have our own personal star to study, and that is really cool.What are some questions we have about stars like the Sun? What do we know about stars like the Sun already? Go ahead and write down two things you know about the Sun already. Now let’s make a list together as a class.
- Keep in mind that the Sun is huge. Remember the balloon. And it’s not even a very big star. There are stars out there way bigger than the Sun!
- Here’s a question I’ve gotten in the past. Why is the Sun so hot? Is the Sun on fire?in the core, the temperature is an amazing 27 million degrees Fahrenheit (15 million degrees Celsius)! The surface of the Sun is almost 11,000 degrees Fahrenheit (6000 degrees Celsius). The Sun's outer atmosphere (corona) is about 2 million degrees Fahrenheit (1million degrees Celsius).
- http://www.youtube.com/watch?v=qvSxVBalhFM
- What is convection?
- Magnetic fields are at the root of virtually all of the features we see on and above the Sun. Without magnetic fields the Sun would be a rather boring star.
- Sunspots are places where very intense magnetic lines of force break through the Sun's surface. The sunspot cycle results from the recycling of magnetic fields by the flow of material in the interior. Theprominences seen floating above the surface of the Sun are supported, and threaded through, with magnetic fields. The streamers and loops seen in the corona are shaped by magnetic fields.
- Sunspots are places where very intense magnetic lines of force break through the Sun's surface. The sunspot cycle results from the recycling of magnetic fields by the flow of material in the interior. Theprominences seen floating above the surface of the Sun are supported, and threaded through, with magnetic fields. The streamers and loops seen in the corona are shaped by magnetic fields.
- We are going to go outside and see the Sun, and see if we can see any of these.
- http://www.youtube.com/watch?v=sBWPCvdv8Bkhttp://www.youtube.com/watch?v=xTRVV-k0i9M&feature=related
- So we have the solar atmosphere, the Corona, and then we have the photosphere, where we see Sunspots. We have magnetic fields dictating what is going on in the photosphere. Then the convection stuff, the granules that we saw earlier, that is only happening in the outer layers of the star, beneath that, heat is simply radiating out from the core, where something else is happening, the Sun is powered by what is going on in here. This is the furnace of the Sun, the engine.
- Stars like the Sun are fueled by nuclear fusion, not by burning wood, remember!
- Do the worksheet(4*(1.67262158E-4grams)-(6.642E-25 grams))*((3E8meters/second)^2)
- With cars, what uses the most fuel, a smart car, an SUV, or a big bus? The bus, right? Stars are the same way. The big ones burn more fuel, and so they burn hotter, and faster. Their lives are much shorter.
- With cars, what uses the most fuel, a smart car, an SUV, or a big bus? The bus, right? Stars are the same way. The big ones burn more fuel, and so they burn hotter, and faster. Their lives are much shorter. Colors.
- Our Sun is a G star. There are a lot of stars much smaller than the Sun, and some stars that are way bigger than the Sun. There are all colors and sized of stars, but we are going to talk in particular about three kinds: blue giants, Sun-like stars, and red dwarfs.
- We can tell a stars spectral type by looking at its….spectrum (yet another thing we can learn from spectra! Composition, spectral type, redshift which tells us how far away it is, all kinds of things) Spectral type can tell us temperature. So by looking at a stars spectrum, we can see oh look it’s a B star, so that must mean it is about 14,000 Kelvin, which means its about 25,000 degrees Fahrenheit.
- We are going to reproduce H-R’s experiment. Only we do not have to go measure the brightness of the stars, or the temperature, I have already gathered the data. But I do want us to think about how we WOULD have gathered the data. If we wanted a list of the temperatures and the brightnesses of the stars here, what would we need?Break?
- So remember from before we were breaking stars on the main sequence into three main types…this does not include protostars, and it does not include dying stars, we are only talking right now about stars in the prime of their lives, on the main sequence. These stars’ masses determine everything about them. This star is red why? And this star is blue why? And this star is big why? And This star is mediaum why? And this star is brighter than this star, and hotter than it why? ALL because of MASS. Which star has the strongest gravity? The blue giant, right, because it bends spacetime more.Esentially, however, these stars are fueled by the same thing, what? Nuclear fusion. And which one has the longest lifetime? The red one. And which one lives the shortest? The blue one. It has a very short, very hot, very bright life. Live fast die young, that’s their motto, the blue giants.
- So lets go back to that chart we made earlier. We call this a HertzsprungRussel diagram, remember? And we had the main sequence, which we identified, but we also had these other groups of stars. There was a group up here, and a group up here, and another group down here. These groups represent other places in a stars lifetime, after it has left the main sequence.
- Why can’t we see features on the star’s surface? Why is this picture so blurry?This is how big a red giant is compared to our system: http://www.youtube.com/watch?v=zppa-Zkp74E&feature=player_embedded
- This is a supernova remnant on the right, it is what is leftover after a star explodes.
- Remember gravitational lensing?
- Remember that the Sun will NEVER explode, it is simply not big enough. It will never explode. Not going to happen. But it will continue its lifecycle, and become a red giant.Watch red giant video:http://www.youtube.com/watch?v=iauIP8swfBY&feature=player_embeddedhttp://www.youtube.com/watch?v=iauIP8swfBY&feature=related – Sun becomes a Red Giant
- This is the full lifecycle of a star like the Sun.
- This is the full lifecycle of a really big star. Remember that after a supernova it can go one of two ways, to a neutron star, or to a black hole.
- Remember that the smallest stars burn their fuel very, very slowly, because they are so fuel efficient, like the smart car. Why is this star red again? Because it is not burning hot, it is burning cool. The truth is, no red dwarf that has ever been born has died yet, because they live so long! So we don’t know. Every red dwarf star that has ever been born is still alive.