Observational Parameters by Santosh Takale at MU-Basic(27-10-13)

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This is the Lecture taken by Santosh Takale at Nehru Planetarium for Basic Astronomy course by Extra-Mural Dept of Mumbai University.

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Observational Parameters Santosh Takale B. Tech (Mech. Engg.), Scientific Officer, Bhabha Atomic Research Centre, Mumbai, 09967584554 / santoshatbarc@gmail.com :

Observational Parameters Santosh Takale B. Tech (Mech. Engg .), Scientific Officer, Bhabha Atomic Research Centre, Mumbai, 09967584554 / santoshatbarc@gmail.com

Astronomy Studies:

Astronomy Studies Theoretical Observational Field Observation Aspects Required theoretical Aspects

Field Observation Aspects:

Field Observation Aspects What we are Looking for ? Constellations Nakshtras Sunsigns Planets Notable Stars Meteor Shower Galaxies, Dwarf Galaxies Messier Objects, Nebulae, Star Clusters etc.

Field Observation Aspects:

Field Observation Aspects What are the references ? Horizon Directions Pole Star Some known objects (constell n ) Planetary Position Aids / Accessories Star Maps Software : Stellarium, Celestia Binocular & Telescopes

Field Observation Aspects:

Field Observation Aspects Measuring Sky with Deg, Min & Seconds ? Pole Star at 19 degree from horizon (Mum) Full Moon /Sun – 0.5 degree (30 min) Link M44 ( Beehive cluster) – 90 min Smallest constell n (Crux) – 68.45 sq deg Biggest Constell n (Hydra) – 1304 sq deg Thumb Rules for Degree measurement : Fist 10 deg, Raised Thumb 5 deg Raised Thumb with little finger & Fist 19 deg Mumbai : 19 deg Latt. & 72 deg Long. India bet n : 57 to 97 & 8 to 37 (Long /Latt)

Field Observation Aspects:

Field Observation Aspects Guide lines for Sky observations : Wait & Watch (7 to 10 minutes for eyes to acclimatize) Initialize sky observation from Home terrace A, B, C, S of Sky observations? A : Aviation Head lights B : Migratory Birds C : Clouds S : Space awareness

Required Theoretical Aspects:

Required Theoretical Aspects Distances & Units ? Techniques of measurements & Limits ? Velocities of celestial Objects ? Magnitude, Scales & Calculations ? HR, Planck & Wien’s ? Colour Index ? Standard Candles ? Scales – ZOOM IN ?

Distances & Units:

Distances & Units mm, cm, inch, feet, yard, meter, furlong, km, miles . AU, LY, Parsec. Pico, nano, micro, mili, Kilo, mega, giga, tera. Avg. Human Height : 1.5 to 2 meter. Plane fly at : 10 kms. (Mt Everest 9 kms) India : 3000 EW x 2700 NS (kms x kms) Diameter of earth : 12700 kms. Dia of Geosta. satellite orbit : 1 00 000 kms. Dist to moon from earth : 3 84 000 kms. Dia of Sun : 13 92 000 kms Distance to sun from earth : 15 00 00 000 kms (ie. 1 AU) Distance to sun from Jupiter : 1 00 00 00 000 kms (ie. 7 AU)

Distances & Units:

Distances & Units Distance to sun from pluto : 40 AU. Distance to sun from kupier belt : 700 AU (100 billion kms) Oort’s cloud is up to : 20000 AU One Light year (1 Ly) : 63271 AU One parsec (Pc) : 3.26 Ly = 206265 AU The nearest star to us : 4.3 Ly = AU = kms 10 Parsec : 32.6 Ly = 3 x 10 17 mts Center of galaxy from us : 8.5 kpc = Ly (beyond reach of parallax method) Dia of Milky way : 1 Lac Ly = 30 kpc = 10 21 mts Dia of Andromeda : 1.8 Lac Ly Dist betn Andromeda & MW : 22 Lac Ly Dia of Local Cluster of galaxy : 1 Mpc Span of Universe : 15 billion Ly = 10 10 Ly = 10 23 kms

Convenient Units in Astronomy:

Convenient Units in Astronomy Astronomical Unit (A.U.) The average distance between the sun and the Earth 150 million km  1.5 x 10 8 km Useful for planetary distances Light Year The distance covered by light in 1 year Approximately 10 13 km = 10 16 m Parsec The distance at which 1A.U. subtends parallax of 1 arc second

Distance to nearest stars:

Distance to nearest stars Name Distance (LY) Spectral Type R.A. Dec. Luminosity (Solar Units) Proxima Centauri 4.2 M5V 14 30 -62 41 6 x 10 -6 Alpha Centauri A 4.3 G2V 14 33 -60 50 1.5 Alpha Centauri B 4.3 K0V 14 33 -60 50 0.5 Barnard's Star 6.0 M4V 17 57 +04 33 4 x 10 -4 Wolf 359 (Gliese 406) 7.8 M6V 10 56 +07 03 2 x 10 -5 Lalande 21185 (HD 95735) 8.2 M2V 11 04 +36 02 5 x 10 -3 Luyten 726-8 A 8.6 M5V 01 38 -17 58 6 x 10 -5 Luyten 726-8 B (UV Ceti) 8.6 M6V 01 38 -17 58 4 x 10 -5 Sirius A 8.6 A1V 06 45 -16 43 24 Sirius B 8.6 WD 06 45 -16 43 3 x 10 -3 Ross 154 (Gliese 729) 9.6 M4V 18 50 -23 49 5 x 10 -4 Ross 248 (Gliese 905) 10.3 M6V 23 42 +44 12 1 x 10 -4 Epsilon Eridani 10.7 K2V 03 33 -09 27 0.3

What is parallax?:

What is parallax? Techniques of measurements

PowerPoint Presentation:

Basics of Parallax : Arc (S ) = radii (r) x angle (p) …{ angle is physically measured, Arc is dist bet S & E, radii is dist bet Earth & star } r = S/p x 360/2 x pi (degrees) ... { 1 deg = 3600 sec} r = 206265 x S/p … { p is in arcsec} r = 206265 AU / p (arcsec) r = 1 parsec = 206265 x 15,00,00,000 kms = r / 9.46 x 10 12 Ly = 3.26 Ly Distance in parsec D pc = 1/p (arc sec) 1pc = 3.26ly = 206265 A.U. b Techniques of measurements For stars having co-latitude  : Measured change = True change / cos  Parallax method is reliable up to about 1kpc

PowerPoint Presentation:

Point on Earth Surface : Velocity (kms/ hr) = Dist / Time = 12700 x 3.142 / 24 Velocity (kms/ sec) = 12700 x 3.142 / (24 x 3600) Point on Sun Surface : Velocity (kms/ hr) = Dist / Time = 13 92 000 x 3.142 / (25 x 24) Velocity (kms/ sec) = 13 92 000 x 3.142 / (25 x 24 x 3600) Point on Altair Surface : Velocity (kms/ hr) = Dist / Time = 1.5 x 13 92 000 x 3.142 / (6.5) Velocity (kms/ sec) = 1.5 x 13 92 000 x 3.142 / (6.5 x 3600) Earth around Sun : Velocity (kms/ hr) = Dist / Time = 2 x 15 x 10 7 x 3.142 / (365 x 24) Velocity (kms/ sec) = 2 x 15 x 10 7 x 3.142 / (365 x 24 x 3600) Sun in Milky way : Orbit dia = 30000 Ly, Period is 240 million Yr. Velocity : 486000 miles / hr : 220 Kms / Sec Velocity Calculations

PowerPoint Presentation:

Magnitude scale – Originally by Hipparchus : After the sunset the first set of stars to be seen were 1 st magnitude stars, then 2 nd , 3 rd , … magnitude stars are visible. Hence the brightest stars are 1 st magnitude while the faintest stars are 6 th magnitude stars. When quantitative studies was done with the visual appearance and the amount of light received from the stars it was observed that the magnitudes are logarithmically related to the flux of light emitted by the stars. Magnitude, Scales & Calculations

PowerPoint Presentation:

The flux l is defined as the amount of energy received per unit area per unit time. e.g. we receive solar flux of 1400 W/m 2 . The flux received is inversely proportional to the square of the distance. If the two stars emit flux l 1 and l 2 , then their magnitudes m 1 and m 2 respectively are related by the formula: m 2 – m 1 = - 2.5 log( l 2 / l 1 ) The 6 th magnitude star is 100 times fainter than the 1 st magnitude star. Magnitude, Scales & Calculations

What’s Ref ::

What’s Ref : A survey of hundred 6 th magnitude (visually the faintest) stars around the pole star was done. The average flux of these 100 ‘north polar sequence’ stars was taken as the flux for the 6 th magnitude star. From that, for m = 0, the flux is 2.48 x 10 –8 W/m 2 Once the fixed point of magnitude scale was defined this way, the brightest star have magnitude even negative. E.g. the Sirius has magnitude of –1.47, Venus can have magnitude of – 4.4 Magnitude, Scales & Calculations

Magnitude scale ::

Magnitude scale : Magnitude, Scales & Calculations

Apparent/Visual and Absolute magnitudes:

Apparent/Visual and Absolute magnitudes In order to compare the real brightness of stars, one uses absolute magnitude ( M ) - It is the apparent magnitude of an object when it is placed at a distance of 10pc. The sun’s apparent magnitude is – 26.8, while its absolute magnitude is 4.5 A star might look brighter than another star Either, it is actually brighter Or, it is closer to us than the other star Magnitude, Scales & Calculations

Relation between m and M ::

Relation between m and M : M = m – 5 log D pc + 5 Canopus (the second brightest star in the night sky) has apparent magnitude of -0.6, while the absolute magnitude is -5.5 Estimate its distance. Sirius has m = - 1.47 and M = 1.42 Estimate the distance of Sirius. Magnitude, Scales & Calculations

Distance Estimation using HR diagram:

Distance Estimation using HR diagram Knowing the spectral class of stars one can determine its absolute magnitude Knowing the apparent magnitude we can determine its distance All O class stars have same brightness. Hence by finding O type star in distant cluster – one can determine cluster distance

Sun – A perfectly black body!:

Sun – A perfectly black body!

Wien’s displacement Law:

Wien’s displacement Law  max T = 0.29 cm-K Larger the surface temperature, the star peaks at smaller wavelength

Colour Index:

Colour Index Magnitude gives only information about the flux, while the colour index gives information about the colour of the star, which might be useful to know the structure of the star/ its position in HR diagram. To find the colour index, typically three different filters are used. U, B, V B: Blue filter has central wavelength of 440nm V: Visual filter has central wavelength of 568nm

PowerPoint Presentation:

The apparent magnitudes using these filters are found. Then B-V colour index is calculated. For bluish star, magnitude using B filter is smaller than that using V filter. Hence B-V number is negative. Similarly B-V number positive means the stars are reddish in colour. E.g. Betelguese has colour index B–V = 1.50 while Rigel has colour index = –0.03

Standard Candles ::

Standard Candles : If we had standard light bulbs around the universe, we could have found distance from the source by measuring the intensity of light from that source alone . Such sources are called “standard candles”. They are: Cepheid Variables Supernovae

Variable Stars:

Variable Stars Some stars are found to have variable magnitudes. Their magnitudes increase and decrease over the period. The first such star was observed in 1596 by Fabricius. It was o-Ceti or Mira. Its period is 11 months (332 days) Its magnitude varies between 3.5 to 9 In 1784,  Cephei, a yellow supergiant star was found to be variable : Its period is 5 d 8 h 37 m

Cepheid Variables:

Cepheid Variables Stars having similar light variation as  Cephei are called Cepheid variables. Cepheid variables are supergiant stars and can be seen at distances out to about 10-20 Mpc. One needs a distance measurement from some other method for at least one Cepheid – parallax for delta Cephei or distance to SMC. American astronomer Henrietta Leavitt looked at many Cepheid variables in SMC. She found the period luminosity relation (reported in 1912).

Period – Luminosity relation:

Period – Luminosity relation

Types of spectra:

Types of spectra Hot solid bodies show continuous spectra Atomic gases show line spectra

Doppler Effect:

Doppler Effect Approaching vehicle’s whistle blows with higher pitch. The receding vehicle’s whistle has lower pitch. The frequency of the whistle is the same. We hear different notes because of the motion.

Determining Stellar distance from Doppler Shift:

Determining Stellar distance from Doppler Shift Comparing wavelengths of the absorption lines of stars with those in the laboratory frame, we can find whether the star is approaching us or receding from us. Entire pattern needs to be compared for this.

Hubble’s Law:

Hubble’s Law Edwin Hubble in 30’s found that all the far off galaxies show red shift indicating that they all are receding away from us. Farther the galaxy, they recede faster.

Supernovae:

Supernovae Constant absolute magnitude of -19.6 Type I – no hydrogen line in spectrum, shows Si emission From white dwarfs or stars close to the Chandrasekhar limit Very bright initially, and slow decay in brightness due to cobalt  iron conversion Brightness estimated, hence standard candle.

Various Methods to measure distances:

Various Methods to measure distances

References & Thanks to ::

References & Thanks to : Prof. Mahesh Shetti’s notes. Shri . Mohan Apte sir’s book ‘Astronomical Calculation’. Marathi website : www. Avakashvedh.com by ‘ Sachin Pilankar Wikipedia website : http://en.wikipedia.org

Good Books to be read….:

Good Books to be read…. Astronomy for Amateurs…………….…. Pradeep Nayak . Kgaaola pircaya ……………………………… p`idp naayak . duiba-NaI AaiNa vaoQaXaaLa …………………… AanaMd GaOsaasa . taraMgaNa …………………………………… p`idp naayak . AakaXaaXaI jaDlao naato ………………… Da ^. jayaMt naarLIkr . kRYNaivavar ………………………………… maaohna AapTo . vaoQa ivaXvaacaa maanavaI XaaOyaa-caa ……………… p`a . p. ra . AaDo -. Astonomical Calculation ………….…..… Mohan Apte . A Brief History of Time ………………..…. Stephen Hawking. AMtraL AaiNa iva&ana ………………… Da ^. jayaMt naarLIkr .

PowerPoint Presentation:

Details of Additional free Lectures delivered by Santosh Takale : (Few lectures will be with Slide shows. Duration is 45 to 75 minutes) Understanding the Universe ( ivaSvaacao AMtrMga ). Career Guidance ( kiryar maaga-dSa-na ). Snakes- Myths & Facts. ( saap : samaja - gaOrsamaja ). Sky Observation with naked eye & Telescope ( AakaSa inarIxaNa ). Human Society & Beliefs/Superstition ( maanavaI samaaja AaiNa Eawa / AMQaEawa ). Communication skills & Personality Development ( saMBaaYaNa klaa va vya@tIma%va ivakasa ). Management techniques & Time Management. Being true Citizen of Country with vast diversity-India.

PowerPoint Presentation:

Certificate Course in Astronomy and Astrophysics

“ If you think you are too small an entity to play any significant role in the growth of Yourself & Society, then just think of the potential of an Atom ! ”:

“ If you think you are too small an entity to play any significant role in the growth of Yourself & Society, then just think of the potential of an Atom ! ”

Santosh Takale santoshatbarc@gmail.com s_tacs@rediffmail.com Ph-9967584554 / 7738984852 / 9224681972:

Santosh Takale santoshatbarc@gmail.com s_tacs@rediffmail.com Ph-9967584554 / 7738984852 / 9224681972

PowerPoint Presentation:

Santosh Takale is senior Scientific Officer at Bhabha Atomic Research Center, Mumbai. He has done B. Tech in Mechanical Engineering & advance studies in Nuclear Engineering at BARC, Mumbai. He has also obtained many certification in the field of Welding, Non Destructive Testing & Radiation Safety, which includes IWE (International Welding Engineer), Radiation Safety Officer & ISNT, ASNT Level III in Ultrasonic Testing & Level II in Radiographic Testing, Eddy Current Testing, Dye Penetrant testing, Visual Inspection & Magnetic Particle Testing. He is Founder of ‘TAKALE CHARITABLE TRUST’ & ‘Institute for Computer & Information Technology- Panvel . He is President of ‘ maharaYT / AMQaEaQda inamaU-lana saimatI ’ Panvel & Sky Watcher’s Association of Raigad . He is also honorary member of many reputed , regional and national oraganisations in technical & social field. He has been honoured with many prestigious award which includes ‘VISHESH GAURAVARTHI’ ‘PANVEL BHUSHAN’, ‘ANIS RAIGAD UTKRUSHTA KARYAKARTA-2012’ ‘MAHARASHTRA GAURAV’, ‘YASHWANT GAURAV’ & ‘RASHTRA GAURAV’ for his outstanding contribution in the field of science & technology as well as social field. Contact Details : santoshatbarc@gmail.com and s_tacs@rediffmail.com Ph – 09967584554. Website : www.takalecharitabletrust.org

Thank U all:

Thank U all

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