observational parameters by santosh takale at mu np basic astro course

Observational Parameters

Santosh TakaleB. Tech (Mech. Engg.), Scientific Officer,

Bhabha Atomic Research Centre, Mumbai, 09967584554 / [email protected]

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Astronomy Studies

• Theoretical

• Observational

– Field Observation Aspects

– Required theoretical 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.





• What are the references ?

– Horizon

– Directions

– Pole Star

– Some known objects (constelln)

– Planetary Position

• Aids / Accessories

– Star Maps

– Software : Stellarium, Celestia

– Binocular & Telescopes





• 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 constelln (Crux) – 68.45 sq deg

– Biggest Constelln (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 betn : 57 to 97 & 8 to 37 (Long /Latt)





• 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

• 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

• 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

• 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 1017 mts

• Center of galaxy from us : 8.5 kpc = Ly

(beyond reach of parallax method)

• Dia of Milky way : 1 Lac Ly = 30 kpc = 1021mts

• 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 = 1010 Ly = 1023 kms




Convenient Units in Astronomy

• Astronomical Unit (A.U.)– The average distance between the sun and the Earth

– 150 million km ≈ 1.5 x 108 km– Useful for planetary distances

• Light Year– The distance covered by light in 1 year

– Approximately 1013km = 1016m

• Parsec– The distance at which 1A.U. subtends parallax of 1 arc second




Distance to nearest stars

NameDistance

(LY)Spectral

TypeR.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?arcsecp

Dpc1

=

Techniques of measurements




• 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 1012 Ly = 3.26 Ly

• Distance in parsec Dpc = 1/p (arc sec)

• 1pc = 3.26ly = 206265 A.U.

β

Techniques of measurements

• For stars having co-latitude β :

Measured change = True change / cos β

• Parallax method is reliable up to about 1kpc




• 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 107 x 3.142 / (365 x 24)

• Velocity (kms/ sec) = 2 x 15 x 107 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




• Magnitude scale – Originally by Hipparchus :

– After the sunset the first set of stars to be seen were 1st magnitudestars, then 2nd, 3rd, … magnitude stars are visible.

– Hence the brightest stars are 1st magnitude while the faintest stars are6th magnitude stars.

• When quantitative studies was done with the visualappearance and the amount of light received from thestars it was observed that the magnitudes arelogarithmically related to the flux of light emitted by thestars.

Magnitude, Scales & Calculations




• 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/m2.

• The flux received is inversely proportional to the square of the distance.

• If the two stars emit flux l1 and l2, then their magnitudes m1 and m2 respectively are related by the formula:

m2 – m1 = - 2.5 log(l2/l1)

• The 6th magnitude star is 100 times fainter than the 1st

magnitude star.





What’s Ref :

• A survey of hundred 6th magnitude (visually the faintest) starsaround the pole star was done. The average flux of these 100‘north polar sequence’ stars was taken as the flux for the 6th

magnitude star.

• From that, for m = 0, the flux is 2.48 x 10–8 W/m2

• Once the fixed point of magnitude scale was defined this way,the brightest star have magnitude even negative. E.g. theSirius has magnitude of –1.47, Venus can have magnitudeof – 4.4





Magnitude scale :





Apparent/Visual and Absolute magnitudes

• In order to compare the real brightness of stars, one usesabsolute magnitude (M) - It is the apparent magnitude of anobject when it is placed at a distance of 10pc.

• The sun’s apparent magnitude is – 26.8, while itsabsolute 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





Relation between m and M :

• M = m – 5 log Dpc + 5

• Canopus (the second brightest star in thenight 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.





Distance Estimation using HR diagram

• Knowing the spectral class ofstars one can determine itsabsolute magnitude

• Knowing the apparentmagnitude we can determineits distance

• All O class stars have samebrightness. Hence by findingO type star in distant cluster –one can determine clusterdistance




Sun – A perfectly black body!




Wien’s displacement Law

• λmaxT = 0.29 cm-K

• Larger the surface temperature, the star peaks at smaller wavelength




Colour Index

• Magnitude gives only information about the flux, whilethe colour index gives information about the colour ofthe star, which might be useful to know the structure ofthe star/ its position in HR diagram.

• To find the colour index, typically three different filtersare used. U, B, V

• B: Blue filter has central wavelength of 440nm

• V: Visual filter has central wavelength of 568nm




• 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 :

• If we had standard light bulbs around theuniverse, we could have found distance fromthe source by measuring the intensity of lightfrom that source alone.

• Such sources are called “standard candles”.

• They are:– Cepheid Variables

– Supernovae




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, δ Cephei, a yellow supergiant star was found to be variable : Its period is 5d 8h 37m




Cepheid Variables• Stars having similar light

variation as δ Cephei arecalled Cepheid variables.

• Cepheid variables aresupergiant stars and can beseen at distances out to about10-20 Mpc.

• One needs a distancemeasurement from someother method for at least oneCepheid – parallax for deltaCephei or distance to SMC.

o American astronomer Henrietta Leavitt looked at many Cepheid variables in SMC.

o She found the period luminosity relation (reported in 1912).




Period – Luminosity relation




Types of spectra

• Hot solid bodies show continuous spectra

• Atomic gases show line spectra




Doppler Effect

• Approaching vehicle’swhistle blows with higherpitch.

• The receding vehicle’swhistle has lower pitch.

• The frequency of thewhistle is the same.

• We hear different notesbecause of the motion.




Determining Stellar distance from Doppler Shift

• Comparing wavelengthsof the absorption lines ofstars with those in thelaboratory frame, we canfind whether the star isapproaching us orreceding from us.

• Entire pattern needs tobe compared for this.




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.

Distance D km/s/Mpc) (73Constant Hubble H

velocitylrecessiona vD v

===

= H




Supernovae

• Constant absolute magnitude of-19.6

• Type I – no hydrogen line inspectrum, shows Si emission

• From white dwarfs or starsclose to the Chandrasekhar limit

• Very bright initially, and slowdecay in brightness due tocobaltà iron conversion

• Brightness estimated, hencestandard candle.




Various Methods to measure distances




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


http://en.wikipedia.org



Good Books to be read….

• Astronomy for Amateurs…………….…. Pradeep Nayak.

• Kgaaola pircaya ……………………………… pìdp naayak.

• duiba-NaI AaiNa vaoQaXaaLa …………………… AanaMd GaOsaasa.

• taraMgaNa …………………………………… pìdp naayak.

• AakaXaaXaI jaDlao naato ………………… Da^. jayaMt naarLIkr.

• kRYNaivavar ………………………………… maaohna AapTo.

• vaoQa ivaXvaacaa maanavaI XaaOyaa-caa ……………… pà. p. ra. AaDo-.• Astonomical Calculation ………….…..… Mohan Apte.

• A Brief History of Time ………………..…. Stephen Hawking.

• AMtraL AaiNa iva&ana ………………… Da^. jayaMt naarLIkr.




Details of Additional free Lectures delivered bySantosh 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.




Santosh Takale is senior Scientific Officer at Bhabha AtomicResearch Center, Mumbai. He has done B. Tech in MechanicalEngineering & advance studies in Nuclear Engineering at BARC,Mumbai. He has also obtained many certification in the field ofWelding, Non Destructive Testing & Radiation Safety, which includesIWE (International Welding Engineer), Radiation Safety Officer &ISNT, ASNT Level III in Ultrasonic Testing & Level II in RadiographicTesting, Eddy Current Testing, Dye Penetrant testing, VisualInspection & 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 manyreputed , regional and national oraganisations in technical & social field.

He has been honoured with many prestigious award which includes ‘VISHESHGAURAVARTHI’ ‘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 socialfield.

Contact Details : [email protected] and [email protected] Ph – 09967584554. Website : www.takalecharitabletrust.org




http://www.takalecharitabletrust.org



Thank U all




observational parameters by santosh takale at mu np basic astro course

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