ASTR 1020 1st Edition Lecture 6 Current LectureQ: The Sun is made up of mostly hydrogen. Yet the p-p chain deals only with nuclei. Why are we not mentioning the electrons?A: The core is very hot so the electrons are all ionized ----------------------------------------Plasma –The 4th state of matter- Hydrogen is fully ionized in core of sun –electrons are not bound to protons- Protons and electrons co-exist (electrically neutral) but not bound to each otherP-P Chain fusion: What about the electrons?Spare electrons annihilate with positrons from step 1 Forces EQUAL: Pressure outward =Gravity inwardREVIEW: Interior of Sun- Coreo Fusion, 15 million K- Radiative zoneo <5 million K, too cold for fusiono energy diffuses out over ~10^5 years (takes a long time to get out)- Convective Zoneo Hot plasma rising to surface (hot air rises, cold air seeps) Magnetic Fields- Hard to visualize the actual fields, but lines show field strength and direction- Lines close together = strong field - Magnetic fields cause charged objects to curl, “trap” protons and electrons in field- If field moves, matter can be accelerated to very high speeds along fieldThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Redirects charged particles to much higher speeds or temperatures- They trap gas in huge bubbling loops- Cooler areas at “liftoff” cause dark sunspots ------------------------------------------------------------------------------------------------------------Chromosphere- Just above photosphere- Temperature goes back UPo T ~ 6,000-10,000 K- Heated by magnetic fields?- Very low density/thing gas (can see through it)- Emission in Hydrogen lightCorona- Temperature goes even HIGHERo T ~ 1 million K- More magnetic heating (??)- Extremely low density- Origin of most of the Sun’s X-rays - Corona in visible light revealed during an eclipse (or put your thumb over the sun)Solar Wind- A top of corona, gas is hot enough to escape Sun’s gravity o Corona is constantly “evaporating”o ~1 million tons/secondo replenished from belowo mostly protons and electrons- blows through solar system at 400-800 km/secWhen Prominences Go Bad- Occasionally the magnetic field lines in a prominence “snap”o Energy and Light is released (flares)- Charged particles are flung into space at high speedCoronal MASS Ejections Blast Out Charged Particles- PROTONS!Can:o Damage Satelliteso Harm astronautso Induce currents on Earth and destroy electric transformers on the groundo Cause swelling in the Earth’s atmosphere Earth’s magnetic field (magnetosphere) protects us from most effects of solar wind, storms.Charged particles deflected to magnetic poles.Protons interacting with Earth’s atmosphere = AURORAThe Carrington Event (1859)- Giant CME struck Earth- Telegraph lines threw sparks, worked while unplugged from power source- Bright as dawn in Colorado, auroras in Florida and Australia - X-class flare in 2012 of similar magnitude to Carrington Event not aimed at Earth!Where does the Sun end?- Heliosphere =extension of solar wind out past the Kuiper Belt (~100 AU)Chapter 15: Surveying the StarsQ: What is the common trait of all main sequence stars?A: They all generate energy through hydrogen fusionHow Far Away is It?- We’ll keep asking this question- Several techniques, each valid for different objects at different distancesTechnique #1:Parallax distance- Measure apparent movement of stars over a yearo Apparent movement is caused by Earth’s actual movement around the SunUSING PARALLAX- Distance (parsecs) = 1/p (arsec)- New distance unit invented for just this method of distance measurement!!o Parsec = (parallax + arcsecond)o 1 parsec = the distance at which an object would have a parallax of 1 arcsecondo 1 parsec = 3.26 light years Q: For a star with a parallax angle of .5 arcsec, what is its distance from us?A: 2 pcQ: The best telescopes ON Earth can measure a parallax angle of about .001arcseconds. What distance does this correspond to?A: 100 pcBest parallax measurement until now: HIPPARCOS SATELLITE (1989-1993)- Measurements made many times accurate to .001 arcsec ( 1000 pc)- 100,000 stars mapped Apparent Brightness and Luminosity - Apparent Brightness –how bright an object appears to telescopes on Earth- Luminosity –the actual power output of the object Q : Brad and Angelina are two stars that have the same apparent brightness. Brad has a larger parallax angle than Angelina. Which one is more luminous?A: