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# Instructions to order a star and to place it on the H-R graph accurately .

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Need to know its luminosity, but it is difficult, because distance is unknown If you can estimate a star’s diameter and/or mass, you can figure out its luminosity Then you can also find the distance to this star. How to classify a star and to place it on the H-R diagram correctly??. 0.
Transcripts
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Need to know its glow, yet it is troublesome, in light of the fact that separation is obscure If you can evaluate a star\'s breadth and additionally mass, you can make sense of its radiance Then you can likewise discover the separation to this star How to order a star and to place it on the H-R graph effectively??

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0 The Radii of Stars in the Hertzsprung-Russell Diagram Betelgeuse Rigel 10,000 times the sun\'s sweep Polaris 100 times the sun\'s range Sun As vast as the sun

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0 The Relative Sizes of Stars in the Hertzsprung-Russell Diagram

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How to recognize fundamental succession stars and goliaths? Is there any otherworldly mark of mammoths? The width of otherworldly lines!

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0 Spectral Lines of Giants Pressure and thickness in the airs of goliaths are lower than in primary succession stars. => Absorption lines in spectra of monsters and supergiants are smaller than in principle arrangement stars => From the line widths, we can gauge the size and in this manner, the radiance of a star.  Distance appraise (spectroscopic parallax)

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Luminosity Classes Ia Bright Supergiants Ia Ib Supergiants II Bright Giants III Giants IV Subgiants IV V Main-Sequence Stars

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Ia brilliant supergiant Ib Supergiant II splendid mammoth III goliath IV subgiant V principle succession star Luminosity classes

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Example Luminosity Classes Our Sun: G2 star on the Main Sequence: G2V Polaris: G2 star with Supergiant glow: G2Ib

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Measuring masses Mass is the most vital parameter. Knowing masses of stars would permit us to figure their glows, lifetime and all different properties. In any case, how to gauge masses??

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Measuring masses Binary Stars More than 50 % of all stars in our Milky Way are not single stars, but rather have a place with parallels: Pairs or various frameworks of stars which circle their normal focal point of mass. On the off chance that we can gauge and comprehend their orbital movement, we can assess the stellar masses.

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The Center of Mass focal point of mass = adjust purpose of the framework. Both masses level with => focal point of mass is in the center, r A = r B . The more unequal the masses are, the more it movements toward the more gigantic star.

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Center of Mass (SLIDESHOW MODE ONLY)

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m 1 m 2

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Estimating Stellar Masses Recall Kepler\'s third Law: P y 2 = an AU 3 Valid for the Solar framework: star with 1 sunlight based mass in the middle. We find practically similar law for paired stars with masses M An and M B not quite the same as 1 sun powered mass: an AU 3 ____ M A + M B = P y 2 (M An and M B in units of sun oriented masses)

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Examples: Estimating Mass Binary framework with time of P = 32 years and partition of a = 16 AU: 16 3 ____ M A + M B = 4 sun based masses. 32 2 Arbitrary units: How to quantify period and partition?

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Visual Binaries The perfect case: Both stars can be seen specifically, and their partition and relative movement can be taken after straightforwardly.

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Visual doubles The Castor framework The Sirius framework The two stars are independently obvious in the telescope

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Detecting the nearness of a buddy by its gravitational impact on the essential star. Wobbling movement of Sirius A

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Spectroscopic Binaries Usually, parallel detachment a can not be measured straightforwardly on the grounds that the stars are excessively near each other. Stars are viewed as a solitary point However: 1) their SPECTRA are distinctive, as various fingerprints; 2) Their phantom lines move intermittently due to Doppler impact. This permits us to quantify their orbital speeds

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The Doppler Effect The light of a moving source is blue/red moved by Dl/l 0 = v r/c l 0 = genuine wavelength discharged by the source Dl = Wavelength change because of Doppler impact v r = outspread speed( along the viewable pathway) Blue Shift (to higher frequencies) Red Shift (to lower frequencies) v r

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(Observed wavelength - Rest wavelength) Shift z = (Rest wavelength) The Doppler impact: clear change in the wavelength of radiation brought about by the movement of the source Doppler impact:

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Doppler impact The Doppler impact: evident change in the wavelength of radiation created by the movement of the source RADIAL speed!!

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The Doppler Effect The Doppler impact permits us to gauge the source\'s spiral speed. Dl/l 0 = v r/c v r

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Spectroscopic Binaries The drawing closer star produces blue moved lines; the subsiding star produces red moved lines in the range. Doppler move  Measurement of spiral speeds  Estimate of division a  Estimate of masses

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Spectroscopic pairs Stars are viewed as a solitary point Spectra of both stars are recognizable Sometimes range of one and only star is seen

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Spectroscopic Binaries (3) Typical grouping of spectra from a spectroscopic parallel framework Time

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Determining the orbital period

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Measure the orbital period Measure the outspread segment of the orbital speeds Can evaluate the circle size Can decide masses!

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1. Below is an outspread speed bend for a spectroscopic twofold. Assess the mass of every star if the mass of the double framework is 6 sunlight based masses. M A d A = M B d B V ~ 2  d/P

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Only the capacity of masses and slant edge can be measured

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THE PLANET CANNOT BE SEEN ...BUT MOTIONS OF THE STAR BETRAY ITS PRESENCE !

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450 km 9 cm/s 150 000 km 30 km/s X 750 000 km 13 m/s JUPITER X 780 000 km 13 km/s EARTH

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2020 1995 2010 1990 2015 2005 2000 0.002" MOTIONS OF THE SUN VIEWED FROM A STAR 30 LIGHT YEARS AWAY 0.002\'\' IS THE ANGULAR SIZE OF A MAN ON THE MOON OR A STANDARD NEWSPAPER FONT 300 KM AWAY Unobservable!

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STELLAR WOBBLE RECEDING: REDDER APPROACHING: BLUER

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Over 100 planets found

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EXPECTED: NEARLY CIRCULAR ORBITS BIG PLANETS FAR AWAY FROM THE STAR NO PLANETS BIGGER THAN JUPITER DISCOVERED: STRONGLY ELONGATED ORBITS BIG PLANETS VERY CLOSE TO THE STAR MANY PLANETS BIGGER THAN JUPITER

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Planetary arrangement of u And 0.85 AU 242 days 2 M J 2.5 AU 3.5 years 4 M J 0.06 AU 4.5 days 0.75 M J 0.73 AU 228 days 1 AU 1 year 0.39 AU 89 days 1.54 AU 1.9 years Solar framework Source: Harvard-Smithsonian CfA

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Habitable zones

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Signs of life in the range:

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The Puzzle of Algol

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John Goodricke 1764-1786 Explained Algol bewilder in 1783

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Eclipsing pairs

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Eclipsing Binaries Usually, slant point of twofold frameworks is obscure  vulnerability in mass appraisals. Unique case: Eclipsing Binaries Here, we realize that we are taking a gander at the framework edge-on!

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The light bend of Algol

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Measuring orbital period and widths

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Measuring distances across D = V sphere (t 2 – t 1 )

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Specific portions of the principle succession are possessed by stars of a particular mass L~ M 3.5 reliance, however Cutoff at masses > 100 M  and < 0.08 M 

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Puzzles of H-R outline Why > 90% of stars are on the fundamental grouping? Purpose behind mass-radiance reliance and mass cutoff Same stars at various phases of life or simply unique stars?

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How would we be able to find out about the life of stars?? Our life expectancy is ~ 80 years Human development exists ~ 5000 years Our Sun exists no less than 4.6 billion years!

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Star Clusters – "School Classes" for Stars They comprise of stars of similar age ! Globular groups 100,000 of stars Open bunches 100\'s of stars

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Age of the group from side road point Turnoff point: stars of that mass are going to kick the bucket and move far from the primary arrangement

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Stars spent the greater part of their lives on the Main Sequence. That is the reason it is so populated! Toward the end of its life the star moves far from the Main Sequence More huge and more iridescent stars kick the bucket quicker Hypothesis: Stars on the Main Sequence live because of atomic combination of hydrogen! Stars keep focused principle succession until all hydrogen in the center is devoured Then something ought to happen

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H-R outline 90% of stars are on the fundamental grouping and comply with the mass-iridescence reliance L ~ M 3.5 Stars on the primary arrangement create vitality because of atomic combination of hydrogen In the end of their lives stars move to the upper right corner of the H-R chart

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Mass ought to be most essential parameter It decides the weight in the star focus and the focal temperature It decides the surface temperature Check this theory How to get this reliance?

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Gravity Holds a Star Together Stars are held together by gravity. Gravity tries to pack everything to the inside. What holds a customary star up and forestalls add up to crumple is warm and radiation weight. The warm and radiation weight tries to extend the star layers outward to interminability. Newton\'s attraction law Hydrostatic balance Equation of state Energy transport Mass decides top pick\'s properties

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Amount of hydrogen fuel Lifetime = Rate of vitality misfortune Lifetime T ~ M/L ~ 1/M 3.5-1 = 1/M 2.5 ; p ~ 3.5 T ~ 3x10 8 years M = 4M  ;

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How to clarify the cutoff at masses > 100 M  and < 0.08 M 

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Maximum Masses of Main-Sequence Stars M max ~ 50 - 100 sun based masses a) More gigantic mists section into littler pieces amid star arrangement. b) Very gigantic stars lose mass in solid stellar winds h Carinae Example: h Carinae: Binary arrangement of a 60 M sun and 70 M sun star. Emotional mass misfortune; real ejection in 184

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