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Physics 556 Stellar Astrophysics Prof. James Buckley

Lecture 1 Mapping the Universe

Physics 456/556 Course Outline

•Stellar Structure and Evolution (and other topics in Astrophysics) •Crow 205, TR 1:00-2:30PM •Instructor: Professor James Buckley •AI: Linghan Zhu •Office: Compton 253 •Office hours: TBD •Textbook: Rose, Advanced Stellar Astrophysics, Useful books include: •Radiative Processes in Astrophysics, Rybicki and Lightman, Principles of and Nucleosynthesis, Clayton, Quarks and Leptons, Halzen and Martin •Course requires a knowledge of undergraduate E&M, Quantum Mechanics, Mechanics and Statistical Physics (but will review material as it arrises) • Grade based on one midterm (30%), homework (40%) and final project (30%). Class attendance is required. Physics 556 Syllabus

•Introduction: historical background, astronomical coordinates, distance, stellar magnitudes. •Theory of radiation. •Statistical physics and thermodynamics. •Stellar Structure: hydrostatic equilibrium, radiative transfer, convective transfer, nuclear burning, the Lane-Emden equation for Polytropes. •Relativistic quantum mechanics, Dirac equation, fermions and bosons, quantum statistics, Einstein coefficients. •Reaction equilibrium, ionization equilibrium, out-of-equilibrium processes •Equations of state, degenerate matter. •Time dependent perturbation theory, electromagnetic and weak interactions. •Stellar opacity and radiation absorption processes, oscillator strength, bound-bound, bound-free, free-free interactions •Weak interactions, neutrinos, dark matter. •, interaction rates, WKB approximation. •Stellar stability and evolution. •White dwarfs, neutron and black holes

CircularMy Research acceleration

• Supermassive black holes (discovered trillion electron-volt gamma-ray flares from• a 100 million solar black hole in the Mrk 421, about 400 million light from ) ∆⃗v ⃗a = ∆t • Search for dark matter (with VERITAS gamma-ray observatory, with LZ using 7 tons of liquid Xenon a mile below the surface of the earth, with ADMX using 100 mK RF cavities) • Developed the VERITAS experiment to detect high energy gamma-rays Physics 312, J. Buckley

Physics 312 - Lecture 1 – p. 25/27 CircularElectromagnetic acceleration Spectrum

VERITAS gamma-ray observatory

• ∆⃗v ⃗a = ∆t

HALE 200” telescope

VLA Radio telescope array Physics 312, J. Buckley

Physics 312 - Lecture 1 – p. 25/27

Circular acceleration

• ∆⃗v ⃗a = ∆t

Physics 312, J. Buckley

Physics 312 - Lecture 1 – p. 25/27 Reading

($113-$145 new Amazon) ($24-$45 on Amazon) ($40-$80 used on Amazon) ($27-$60 used on Amazon)

•I recommend purchasing a number of these books, if you plan to continue in graduate astrophysics. Clayton’s book is very complementary to Rose’s, and not expensive. Radiative Processes is an important one to have on your shelf, but pretty pricy. I put this on reserve - you might be able to copy the relevant chapters (mostly chapter 1). Halzen and Martin is an important book for many classes, but you can probably get away with class notes and checking the reserve book.

Horizon Coordinate System Circular accelerationZenith NCP

Az=135deg E

Alt=+45deg W Horizon Circle • S ∆⃗v ⃗a = ∆t

• Altitude (ALT) is the angle measured along a great circle through the zenith and the from the local horizon up to the star, Azimith (AZ) is the angle east of north along the equator to the great circle of the star and zenith. Physics 125, J. Buckley

Physics 312 - Lecture 1 – p. 25/27 CircularEquatorial acceleration Coordinates NCP Hour Circle DEC = 90

DEC = 60 Ecliptic

Celestial Equator DEC = 30

DEC

A=18h = RA

DEC = 0 RA = 4h • A=20h = RA ∆ RA = ⃗v A=22h = RA ⃗a RA = 2h ⌥∆t Spring (Vernal) Equinox

RA = 0h

RA = , measured in hours east of the Vernal Equinox where 24h = 360deg DEC = , measured in degrees north of the celestial equator (negative for southern stars) Physics 125, J. Buckley

Physics 312 - Lecture 1 – p. 25/27

CircularTransits accelerationof Stars NCP Zenith

DEC=40deg

40deg

• ∆ Celestial Equator = ⃗v ⃗a ∆ t Horizon

• A star with Declination angle (DEC) equal to the geographic latitude will transit at the Zenith Physics 125, J. Buckley

Physics 312 - Lecture 1 – p. 25/27 CircularSidereal Time accelerationApparent spin of celestial sphere

DEC = 90

DEC = 60 meridean

DEC = 30

Zenith

DEC = 0 • RA 20h= ∆ = ⃗v A=22h = RA ⃗a RA = 2h ⌥∆t

RA = 0h HA of Vernal Equinox = Sidereal Time

So when the ST=0:00, the vernal equinox is at transit (it’s highest point in the sky) Similarly, when the ST=RA of any star, it is also at transit. Physics 312, J. Buckley

Physics 312 - Lecture 1 – p. 25/27

CircularSidereal acceleration Time To distant star

1 ⇠

1 ⇠ one sidereal • later noon ∆⃗v ⃗a = ∆t it takes 4 more minutes for solar noon Sidereal and Solar Time Simulator http://astro.unl.edu/classaction/animations/coordsmotion/siderealSolarTime.html Physics 312, J. Buckley To distant star Physics 312 - Lecture 1 – p. 25/27 Galactic Coordinates http://en.wikipedia.org/wiki/File:Galactic_coordinates.JPG

Parallax Distance

1AU 1AU d = tan p p

1pc d p”

•By definition, a star at a distance of one (1 pc) will have a angle of one arcsec (1”) •1 pc = 3.08568025 x 1018 cm •1 pc = 3.26163626 ly •Nearest star, Proxima Centauri, has a parallax angle of 0.77” and a distance of 1.3 pc or 4.2 ly List of nearest stars - Wikipedia, the free encyclopedia 1/18/11 10:29 AM

List of nearest stars From Wikipedia, the free encyclopedia

This list of nearest stars contains all known stars (including brown dwarfs) at a distance at most five (16.308 light-years) from the , ordered by increasing distance. Including the Solar System, there are currently 51 stellar systems known which may lie within this distance. These systems contain a total of 62 hydrogen-burning stars and seven brown dwarfs. All of them are in the Galaxy.

Stars that have an less than 6.5 (the lower the apparent magnitude the brighter they appear), and thus can possibly be observed with the naked eye,[1] have their magnitude shown in light blue. The classes of the Artist's conception of a star, the most stars and brown dwarfs are shown in the color of their common type of star in the 's stellar spectral types. (These colors are derived from conventional neighborhood names for the spectral types and do not reflect the star's observed color.) Some parallax and distance results were measured by the Research Consortium on Nearby Stars (RECONS), and these might be only preliminary measurements.[2]

The only first-magnitude stars on this list are , Sirius, and .

See also: List of nearest bright stars

Contents

1 List 2 Map of nearby stars 3 Future and past 4 See also 5 References 6 External links Nearest Stars List

Designation Apparent Absolute J2000.0 Distance[4] [2][3] Additional # Star magnitude magnitude Light-years System Star class Right ascension[2] Declination[2] Arcseconds(±err) references # (mV) (MV) (±err) variable: the Sun travels along has 8 Solar System Sun [2] [2] [2] 180° 0.000015 G2V !26.74 4.85 the ecliptic planets Proxima Centauri 1 M5.5Ve [2] [2] h m s !62° 40! 46" [5][6] 4.2421(16) [7] (V645 Centauri) 11.09 15.53 14 29 43.0 0.768 87(0 29)" Alpha Centauri # Centauri A 1 (Rigil Kentaurus; 2 [2] [2] [2] h m s !60° 50! 02" (HD 128620) G2V 0.01 4.38 14 39 36.5 Toliman) 0.747 23(1 17)"[5][8] 4.3650(68) # Centauri B 2 [2] [2] [2] h m s !60° 50! 14" (HD 128621) K1V 1.34 5.71 14 39 35.1 2 Barnard's Star (BD+04°3561a) 4 M4.0Ve 9.53[2] 13.22[2] 17h 57m 48.5s +04° 41! 36" 0.546 98(1 00)"[5][6] 5.9630(109) 3 (CN Leonis) 5 M6.0V[2] 13.44[2] 16.55[2] 10h 56m 29.2s +07° 00! 53" 0.419 10(2 10)"[5] 7.7825(390) 4 Lalande 21185 (BD+36°2147) 6 M2.0V[2] 7.47[2] 10.44[2] 11h 03m 20.2s +35° 58! 12" 0.393 42(0 70)"[5][6] 8.2905(148) [2] [2] [2] Sirius Sirius A 7 A1V !1.46 1.42 5 06h 45m 08.9s !16° 42! 58" 0.380 02(1 28)"[5][6] 8.5828(289) (# Canis Majoris) Sirius B 7 DA2[2] 8.44[2] 11.34[2] Luyten 726-8 A 9 M5.5Ve [2] [2] (BL Ceti) 12.54 15.40 6 Luyten 726-8 01h 39m 01.3s !17° 57! 01" 0.373 70(2 70)"[5] 8.7280(631) Luyten 726-8 B 10 M6.0Ve [2] [2] (UV Ceti) 12.99 15.85 7 (V1216 Sagittarii) 11 M3.5Ve 10.43[2] 13.07[2] 18h 49m 49.4s !23° 50! 10" 0.336 90(1 78)"[5][6] 9.6813(512) 8 (HH Andromedae) 12 M5.5Ve 12.29[2] 14.79[2] 23h 41m 54.7s +44° 10! 30" 0.316 00(1 10)"[5] 10.322(36) has two 9 (BD!09°697) 13 K2V[2] 3.73[2] 6.19[2] 03h 32m 55.8s !09° 27! 30" 0.309 99(0 79)"[5][6] 10.522(27) proposed planets 10 (CD!36°15693) 14 M1.5Ve 7.34[2] 9.75[2] 23h 05m 52.0s !35° 51! 11" 0.303 64(0 87)"[5][6] 10.742(31) 11 Ross 128 (FI Virginis) 15 M4.0Vn 11.13[2] 13.51[2] 11h 47m 44.4s +00° 48! 16" 0.298 72(1 35)"[5][6] 10.919(49) EZ Aquarii A 16 M5.0Ve [2] [2] EZ Aquarii 13.33 15.64 12 (GJ 866, EZ Aquarii BList 16of nearestM? 13.27 stars[2] 15.58- Wikipedia,[2] 22h 38m the33.4s free!15° encyclopedia 18! 07" 0.289 50(4 40)"[5] 11.266(171) Luyten 789-6) EZ Aquarii C 16 M? 14.03[2] 16.34[2]

F5V- [2] [2] Procyon Procyon A 19 [2] 0.38 2.66 13 IV h m s +05° 13! 30" [5][6] 11.402(32) (# Canis Minoris) 07 39 18.1 0.286 05(0 81)" Procyon B 19 DA[2] 10.70[2] 12.98[2] 61 Cygni A first star 21 [2] [2] [2] h m s +38° 44! 58" (BD+38°4343) K5.0V 5.21 7.49 21 06 53.9 (other Magnitude Scale than 14 61 Cygni 0.286 04(0 56)"[5][6] 11.403(22) Sun) to 61 Cygni B 21 K7.0V[2] 6.03[2] 8.31[2] 21h 06m 55.3s +38° 44! 31" have its (BD+38°4344) distance measured Struve 2398 A 23 [2] [2] [2] h m s +59° 37! 49" Struve 2398 M=1(HD 173739) M=2M3.0V 8.90 11.16M=3 18 42 M=4 46.7 M=5 M=6 http://en.wikipedia.org/wiki/List_of_nearest_stars Page 1 of 4 •Hipparchus (followed by Ptolemy) created a catalog of about 1000 stars that were grouped into six magnitude Brighter Star (to be measured) groups. Ptolemy called the brightest stars first Reference Star magnitude or m=1, the second brightest m=2 and so on. •In the early 19th century, William Herschel (born in Hanover, Germany 1738 - built massive 48” reflector Aperture D 1 and 20’ refractor) devised a naked-eye method to make Aperture D2 quantitative measurements of magnitude •Herschel’s method consisted of viewing a reference star (with a stopped-down telescope) and an unknown with a star (with an identical telescope). When the aperture was adjusted so that the apparent magnitudes were the same, the apparent magnitude could be determined:

F D2/4=F D2/4 F /F =(D /D )2 1 · 1 2 · 2 1 2 2 1 Stellar Magnitudes

•In 1856, Pogson made more precise measurements verifying Hershell’s result that a first magnitude star is about 100 times brighter than a 6th magnitude star. •Pogson formalized the system, the ratio of brightness of two stars with apparent magnitude differing by 1, was defined to be exactly 1001/5=2.512, now known as the Pogson ratio. •Pogson’s scale was originally fixed by assigning Polaris a magnitude of 2. When Polaris was found to be variable, became the standard reference with m=0. •Some examples: The sun has m=-26.73, the full moon m=-12.6, maximum brightness of Jupiter m=-2.94, brightest star Sirius m=-1.47, Vega m=0.03, m=3.44 •The M of a star is defined so that it is the same as the apparent magnitude for stars at a distance of 10 pc (typical for nearby stars). From your textbook:

1001/5 = 100.4 =2.512

0.4(m2 m1) F1/F2 = 10 2 2 0.4(m M) Fabs/Frel = r /(10 pc) = 10 M = m +5 5 log r

Solar

33 1 L =3.836 10 erg s ⇥

L 6 1 2 Radient flux at Earth : F = ⇥ =1.36 10 erg s cm 4d2

2 : F =1.36 kW m CircularDistance accelerationLadder

• Parallax to kpc • Association of galactic objects with galactic structure, clusters, line of sight absorption or dispersion.

• Standard candles - Cepheids to 20 Mpc • Tully-Fisher relation to > 100 Mpc • • Redshift/distance relationship (calibrated∆⃗v by standard candles such ⃗a = as Type Ia supernovae to > 1000 Mpc)∆t

Physics 312, J. Buckley

Physics 312 - Lecture 1 – p. 25/27

Distances in our Galaxy

•Transitions in relative spins of electrons and protons in neutral hydrogen give rise to 21 cm (1420 MHz) radiation •Molecular clouds containing hydrogen, CO, etc. rotate p e p e around GC in Keplerian . •Doppler shifted 21 cm line gives line-of-sight velocity - can use Kepler’s laws to reconstruct distribution of matter in galaxy, distances, enclosed mass (Dark Matter!) •Association of galactic objects (e.g., supernova remnants, Sun pulsars) with molecular clouds can give a crude distance (sometimes the only distance) to galactic objects. Cepheid Variables

•Some stars have regular pulsations (due to changes in opacity with expansion of outer atmosphere, variations in radiation pressures). A few had distances measured by parallax. Can use period/luminosity correlation to determine distances to objects in other systems, e.g., other as pictured above.

Tully Fisher Relation

•In 1977 astronomers Brent Tully and Richard Fisher determined an empirical relationship between intrinsic luminosity and rotation velocity of spiral galaxies. •Rotation velocities are readily measured by Doppler shifts of spectral lines. •As for all standard candles, must calibrate some representative objects by another distance measure (e.g., Cephied variables) and can then use the apparent brightness and inverse square law to determine distance Hubble’s Law Circular acceleration

(0) (0) d˙2 = d a˙ d2(t)=d2 a(t) 2

˙ (0) B d1 = d1 a˙ A R(t) (0) ˙ (0) d (t)=d a(t) d2 d 1 1 = 2 ˙ (0) ) d1 d • 1 ∆⃗v ⃗a = ∆t

If the universe is uniformly expanding so that the all distances grow with some scale factor a(t), then one expects more distant objects to be receding with higher apparent velocity and larger redshift.

Physics 312, J. Buckley

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Standard Candles and Redshift

•If we know the intrinsic luminosity of stars, and measure their brightness we can measure distance •Often hard to know the intrinsic luminosity. Objects for which we have some basis of calibrating intrinsic luminosity are known as standard candles and can be used for measuring distance (or rigorously luminosity distance) •Hubble observed more distant (fainter) galaxies appeared to recede more quickly. Now standard candles can be used to calibrate the redshift-distance relationship (Hubble’s law) to map the most distant universe.

Edwin Hubble, born 1989 in Marshfield, MO! Type Ia SNae as Standard Candles Circular acceleration

• Modern Hubble diagram giving the relationship of the luminosity distance ∆⃗v ⃗a = (expressed as the difference between ∆t apparant and absolute magnitude) versus redshift

m-M=5(log d 1) 10

Physics 312, J. Buckley

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Distance

http://abyss.uoregon.edu/~js/ast123/lectures/lec13.html

•Parallax to kpc

•Spectroscopic Parallax

•Cepheids to 20 Mpc

•Tully-Fisher relation to > 100 Mpc

•Type Ia supernovae to > 1000 Mpc