Presentation on theme: "Ch. 30 - Stars The Sun accounts for more than 99% of the mass in the solar system. The Sun is 330,000 times as massive as Earth. It would take 109 Earths."— Presentation transcript:
1Ch StarsThe Sun accounts for more than 99% of the mass in the solar system.The Sun is 330,000 times as massive as Earth.It would take 109 Earths end to end to fit across the Sun.The Sun’s mass controls the motion of the planets and other objects in the solar system.The Sun’s density in the center is 150,000 kg/m3.This is 13 times the density of lead.A pair of dice would weigh about 2 lbs.The temp. is about 10,000,000 K in the center.These gases become plasma at this temp.Video
2Galileo was the first to study the Sun in detail. Use solar telescopes to study the Sun today.Sun is 110 times larger than the Earth.How long does it take the radiation to reach the Earth?8 minutes 33 sec.The Sun’s surface is about 5,500 C.Video
32. Chromosphere – the outer atmosphere above the photosphere. Regions of the Sun1. Photosphere – inner most layer, yellow surface with granules or blotches. Average temp. = 5,800 KFig (pg. 806)2. Chromosphere – the outer atmosphere above the photosphere.Fig. 30-13. Corona – above the chromosphere with a vacuum like atmosphere.Fig (pg. 807) – Temp. range of 1 to 2 million KVideo
4Solar winds come off the corona and fly towards the Earth. The charged particles from the solar winds are deflected by Earth’s magnetic field and collide with gases in Earth’s atmosphere producing auroras.Auroras are “Northern Lights” produced by solar winds.Sunspots are darks spots with a lower temperature than the surface, thus the dark color. They last about 2 months.Sunspots reach a maximum number every 11.2 years.
5Solar flares are extensions in the corona Solar flares are extensions in the corona. They are violent eruptions from the Sun’s surface.Prominence is an arc of gas that is ejected from the chromosphere. Like solar flares prominences are associated with sunspots.All of this energy comes from the center of the Sun where fusion occurs.Video
6Spectrum Visible Light Spectrum. What are the colors? 3 Types ROYGBIV3 Types1. Continuous spectrum – produced by a flowing solid or liquid, or by a highly compressed, glowing gas. It can also be produced by a prism (refracting the light).2. Emissions spectrum – comes from a noncompressed gas in which bright lines occur at certain wavelenghts.The lines are dependent on the element being observed.3. Absorption spectrum – causes a series of dark bands. These bands are produced from different chemical elements that absorb light at specific wavelengths.They can be used to identify gas in a star’s outer layers.
7Big Dipper Ursa Major or big bear ConstellationsConstellation is a group of stars that forms a pattern in the sky. 88 total.Big Dipper Ursa Major or big bearLittle Dipper Ursa Minor or little bearNorth Star PolarsDraw all threeCassiopeia is a lopsided M above the little dipper.Video – Looking NorthVideo – Looking South
8Circumpolar constellations circle around polaris Ursa Major, Ursa Minor, CassiopeiaWinter ConstellationsOrion’s Belt & the hunterSirius is the left star on Orion’s belt the brightest star in the sky.Summer ConstellationsNorthern CrossAppendix K – pg. 922
102 units of measurement are used by astronomers. When we look at stars in the sky at night they seem to be close to each other. However, we see them in a 2-dimensional view (we can’t see the depth of the stars = 3-D).This means that stars from a constellation may not be close to one another at all.IllustrateBinary star are 2 stars gravitationally bound together and orbit a common center of mass.More than ½ the stars in the sky are binary or multiple-star systems.2 units of measurement are used by astronomers.1. light years = 9.46 x 1012 km2. parsec = 3.26 light years (3.09 x 1013 km).
11Parallax – the apparent shift in position caused by the motion of the observer. The position of the Earth changes as it orbits the Sun. This causes a nearby star to appear to change its position as well.The closer the star, the larger the shift.The distance to the star can be estimated by its parallax shift.A parsec is defined as the distance at which an object has a parallax of 1 arcsecond.Astronomers use this method to record distance up to 500 pc or 1500 ly.
12Magnitude – how bright it appears. A star has the following properties: mass, diameter, brightness, composition, surface temp., and energy output (power).Magnitude – how bright it appears.Used by ancient Greeks – now we use apparent magnitude.Apparent Magnitude – how bright an object appears to be.A +1 star is 100 times brighter than a +6 star.Negative numbers are assigned to the brightest objects.Absolute Magnitude – the brightness of an object is placed at a distance of 10 pc.This system takes into account distance.This can only be calculated when actual distance is known for that object.
13Cooler stars have more absorption bands than hotter stars. Luminosity – measures the energy output from the surface of a star per second.Need apparent magnitude & distance.A star’s spectra (absorption spectra) is used to determine the type of star and categorize it.In order of hottest to coldest: O, B, A, F, G, K, M.Cooler stars have more absorption bands than hotter stars.Fig (pg. 818)Most stars have 73% H & 25% He.Activity
14The red end of the spectrum means there are longer wavelengths coming from the star. This means the distance between the star & the Earth are increasingThis is the Doppler effect.This usually means the star is moving away from the Earth.The blue end of the spectrum means shorter wavelengths are coming from the star.This means the distance between the star and the Earth is decreasing.This usually means the star is moving towards the Earth.
15H-R DiagramsThis uses the relationship between a star’s absolute magnitude, surface temp., and spectral type to distribute stars.The main sequence shows that stars follow a pattern in decreasing surface temp.The outliers are the Supergiants, Giants, and White dwarfs.Video
16What is the next closest star? Alpha CentauriWhat is the closest star?Sun150 million kilometers93 million miles40 trillion kilometers4.3 light years awayLight-years are used to measure space distance 5.8 trillion milesWhat is the speed of light?300,000 km/sec. or 186,000 miles/secLight travels at 9.5 trillion kilometers per year.
17Star Size Star Temperatures Some stars are smaller than the Earth. Some are 2,000 times larger than the SunSome are very dense, others are not.1 teaspoon of Sirius’ mass would weigh more than a ton on Earth.Most stars have similar masses as the Sun.Star TemperaturesWhite & Blue stars are the hottest30,000 degrees CRed stars are the coldest.3,000 degrees CThe Sun’s temperature is about 5,500 C.
18Sirius is a hot blue-white star. Aldebaran is a cooler red star. Supergiants are the largest starsGiants are nextDwarf stars are the smallest.These are very dense.
19Stellar EvolutionStars are thought to have formed from hydrogen & a cloud of dust.A nebulae is a forming star.VideoWhen the forming star becomes dense enough & hot enough to glow it is called a protostar.Fusion occurs once it gets hot enough.It takes a few thousand years to form a white star.It takes about 10 billion years to reach its death.
20A star will then go through the main sequence from: blue, yellow, orange, red. Red is towards the end of their lifespan.Most stars maintain a steady brightness, but there are a few that blink. Why do you suppose they blink?Variable stars are the ones that vary in brightness (blinking).Pulsating stars expand & contract as they change in brightness. Very slow change in brightness, sometimes days.Pulsars are stars that release light and radio waves as it flickers. These are believe to come from dying stars (supernovas).
21As a star dies out it forms a Red Giant. Helium builds up in the core from this.A White Dwarf is the final stage in a star’s lifespan, in which the energy from fusion reactions are used up.They then start to pulsate this is called a Nova.Finally, the white dwarf explodes with half of its mass blown away in a huge cloud of dust.This is called a SupernovaVideo
22Black Hole Neutrons stars are the remaining part of a supernova. Electrons & protons collapse to form a extremely dense neutron. The resistance of the dense neutrons cause the collapse of the core to stop.Black HoleIf the Neutron star is too dense for the neutrons to stop the collapse in which the core collapses forever, then a black hole will form. The collapse doesn’t allow light to escape.Video