Astronomy Science Olympiad Preparation – Flashcards
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Optical double
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not actually binaries simply two stars lying along same line of sight (similar RA & dec) Not gravitationally bound Not usefull in determining stellar masses
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Visual binary
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both stars resolved independently if orbital pd not too long, can monitor motion provides angular separation from center of mass If dist known, linear separations can be calculated
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Astrometric binary
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If one significantly brighter, not possible to see both directly Exitence deduced by observing oscillatory motion of visible member
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Eclipsing binary
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orbital planes oriented approximately along line of sight Recognizable by regular variations in amt of light Can provide relative effective temperatures and radii based on light curve minima & lengths of eclipses
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Spectrum binary
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two superimposed independent discernible spectra Doppler effect causes shifting of spectral lines
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Spectroscopic binary
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if period not too long Orbital motion has component along line of sight Periodic shift in spectral lines observable Only 1 set of periodically varying spectral lines seen
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Systems able to provide us with mass determination
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Visual binaries combined with parallax info Visual binaries with radial velocities available over complete orbit Eclipsing double-line spectroscopic binaries
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O stars
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Hottest blue-white stars with few lines Strong He II absorption (sometimes emission) lines He I absorption lines becoming stronger
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B stars
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Hot blue-white He I absorption lines strongest at B2 H I (Balmer) absorption lines getting stronger
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A stars
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White Balmer absorption lines strongest at A), becoming weaker later Ca II absorption lines becoming stronger
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F stars
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Yellow-white Ca II lines continue to increase, Balmer lines decrease Neutral metal absorption lines (Fe I, Cr I)
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G stars
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Yellow Solar-type spectra Ca II increase Fe I, other neutral metal increase
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K stars
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Cool orange Ca II H & K strongest K0, then decrease dominated by metal absorption
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M stars
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Cool red Molecular absorption bands (TiO, VO) Neutral metal absorption lines remain strong
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L stars
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Very cool, dark red Stronger in infrared Strong molecular absorption bands of metal hydrides, water, CO, Na, K, Rb, Cs, Alkalis TiO, VO decrease
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T stars
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Coolest, Infrared Strong methane, CO decrease
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Wolf-Rayet stars
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discovered by C.J.E. Wolf and G. Rayet Paris Observatory in 1867 more than 220 WR identified, most likely more 25,000 to 100,000 K losing mass at over 10^-5 Solar masses per year Wind speeds of 800 to 3000+ kilometers per second Rapidly rotating Can have starting masses of under 20 solar masses No dramatic variability
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T Tauri
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Low-mass, pre-main-squence represent transition between stars in dust and main-sequence stars Unusual spectral features Strong Balmer lines, Ca II H&K, Fe, Li absorption Large & fairly rapid irregular variations in luminosity within days 0.5 to 2 solar masses
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P Cygni profile
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Absorption trough at short-wavelength edge superimposed on rather broad emission peak
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FU Orionis
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contain instabilities in circumstellar accretion disk Results in 0.01 solar masses being dumped T-Tauri may go through several stages
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Herbig Ae/Be
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named for George Herbig spectral type A or B strong emission lines 2 to 10 solar masses tend to be enveloped much shorter lifetimes
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Herbig-Haro objects
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contain jets of gas first discovered in vicinity of Orion nebula by george Herbig & Guillermo Haro in early 1950s
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Proplyds
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circumstellar disks around stars in Orion Nebula appear to protoplanetary disks around less than 1million year old stars Masses more than 2 * 10^25 kg
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Wien's law
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(Peak wavelength)(Temperature) = 0.002897755 mK
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Stefan Boltzmann Law
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Luminosity = 4(pi)(radius)^2(stefan-boltzmann constant)(effective temperature)^4 Stefan-Boltzmann constant - 5.670400*10^-8 W m^-2 K^4
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Stellar parallax
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d = 1/p" pc
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Distance modulus
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m-M = 5 log d - 5 = 5 log (d/10pc)
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Diffuse molecular clouds
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Also known as translucent molecular clouds 15 to 50 K n around 5 * 10^8 to 5*10^9 m^-3 M around 3 to 100 solar masses Several parsecs across
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Gliese 229b
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very faint brown dwarf orbiting small, red Main Sequence star known as Gliese 229 First object shown conclusively to be substellar, borwn dwarf 5.7 parsecs (9 ly) away prototype of T dwarfs
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Beta Pictoris
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second brightest star in constellation Pictor 63.4 ly away 1.75 as massive and 8.7 as luminous as Sun Very young (8-20 myo) In main seqeucne Excess of infrared emission First debris disk to be imaged around another star Several planetesimal belts and cometary activity Process of planetary formation Delta Scuti variable
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GJ 1214b
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Exoplanet orbiting star GJ 1214 Constellation: Ophiuchus Discovered December 2009 Super-Earth (larger than Earth but has mass and radius significantly less than gas giants) Second such planet First of new class of planets with small size and relatively low density Allows for atmosphere to be studied using spectroscopic technologies Clouds maybe detected December 2013
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Classical Cepheid
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also known as Population I, Type I, Delta Cephei 4-20 times more massive than Sun up to 100,000 more luminous yellow supergiants spectral class F6-K2 Radii change by millions of kilometers Used to determine distance sto galaxies within Local Grou and beyond way to establish Hubble constant
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Type II Cepheid
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also known as Population II periods 1-50 days metal-poor, oil, low mass (half the mass of Sun) Divided into several subgroups by period BL Her: 1-4 days W Virginis: 10-20 days RV Tauri: more than 20 days Used to establish distance to galactic center, globular clusters, and galaxies
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Semiregular variables star
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giants or supergiants of intermediate and late spectral type howing coniderable periodicity in their light changes accompnaied by various irregularities Periods 20 to more than 2000 days Shapes of light curves rather different and variable with each cycle Amplitude froms everal hundredths to several magnitude Several subtypes
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SRA variable
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Spectral type giants, persistent periodicity and usually small amplitude less than 2.5 magntiudes Periods 35-1200 days Differ from Mira only by smaller light magnitudes
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SRB variables
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Poorly defined periodicity (mean cycles in range of 20 to 2300 days) or alternating invervals of periodic and slow irregular changes
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SRC variables
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amplitudes of about 1 mag period from 30 to several thousand days
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SRD variables
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giants and supergiants of F,G, K spectral types sometimes with emission lines in spectra Amplitudes of light variation range from 0.1 to mag Range f periods 30 to 1100 days
