Beyond Pretty Pictures: Science Investigations with a GoTo Telescope & CCD Camera

1. Beyond Pretty Pictures:Science Investigations with a GoTo Telescope & CCD Camera David Richards 2006-10-10 Groombridge 34 All pictures in this presentation are by the author (unless specifically indicated) and were taken with 8” LX200 / ST7e

2. Some Pretty Pictures … M2 (Aqr) M51 (CVn) M103 (Cas) M57 (Lyr)

3. Another reasonably pretty picture : Groombridge 34 (GRB 34) … Groombridge 34 an 8th magnitude double star in the constellation of Andromeda … Approximate Colour CCD ImageRed 1 min (R filter), Green 1 min (V filter), Blue 1 min (B filter)2005-09-18 20:49h UT (#94008-12)

4. … but what questions might we ask about GRB 34 ? What kind of star ? Is it a true binary star ? What are its properties ? Or is simply an optical double ? Groombridge 34 Colour ? Is it moving, which way ? Temperature ? What is it’s orbitial period ? Luminosity ? Size ? Mass ? How far away is it ? Where does it sit ona H-R diagram ? Does it show any brightness or colour variations ?(and if so, what kind & why ? ) What was it’s past ? Does it have any planets ? Could they hold life ? What is it’s future ?

5. Science Investigations with a GoTo Telescope & CCD Camera • Introduction • Goto Telescope / CCD Camera / CCD Basics • My Own Equipment & Setup • Example Observing Session • Astrometry – measurement of star positions • Photometry – measurement of star brightness and colour • Current Projects • Nearby Stars • Exosolar Planets • Selected Variables • Distance Ladder • Collaborative Projects • Discoveries / Follow Up Studies

6. A Popular Goto Telescope e.g. Meade LX200 Schmidt-Cassegrain Telescope (SCT) Worm-gear drive system for smooth sidereal-rate tracking and slewing Hand Controller (Built-in Objects Database) Serial or USB port to allow connection to computer Equatorially Mounted. Polar Aligned Photo from Meade Catalogue

7. Telescope Control / Planetarium Software Current Telescope Position Button enabling slewto new target or location M27 TheSky (Software Bisque)

8. Planetarium Software – Flexibility to import any catalog or ascii object list is important Screen shot from TheSky (Software Bisque) Here we see the import of a list of Globular Clusters in M31(mag 14 to 19), some of which will be a future imaging challenge

9. CCD Camera e.g. SBIG ST-7e camera Electronic controlled exposure (0.11 sec to 60 min) Cooled (typical 30 deg C below ambient)Low Dark Noise / Low Read-Out NoiseNon Anti-Blooming (best for science)Anti-Blooming (best for pretty pictures)Square pixels best Photos from SBIG Catalogue Electronically controlled Filter Wheel(RGB / UBVRI filters)

10. CCD Camera (CCD Chip, Circuit Board, Electronics, Shutter, Cooling Equipment, Housing) Object Telescope CCD Chip Focuser Photon Attachment Shutter Computer Screen Computer Light Sensitive Areaphotons recorded as electrons in ‘square light buckets’ RamHard DriveSoftware 0 0 0 0 0 0 1 5 1 0 0 7 67 3 0 0 2 8 1 0 0 0 0 0 0 0 0 0 0 0 0 1 5 1 0 0 7 67 3 0 0 2 8 1 0 0 0 0 0 0 Electronics USB or Parallel Cable CCD Imaging – The Basics

11. Longer Exposure  Greater Magnitude Reach Consecutive CCD images (star field in Milky Way in Cygnus)2003-08-05  5.2 x 7.6 arc mins (suburban site, Dorset, UK) The 10 sec exposure reaches to mag +12.0 whilst the 40 sec exposure reaches to +13.5

12. Camera Control Software CCDSoft(Software Bisque)

13. x,y Centroid calculation Astrometry( Image Linking / Obtaining a Plate Solution)

14. Photometry Differential Photometry easiest(All-Sky Photometry more difficult and a whole topic in itself) Choose Comparison stars Using software to calculate instrumental magnitudes for stars i) determines star’s Flux ( this is total ADU count minus background ADU count within a circular aperture centred on the star)ii) convert to inst. MagnitudeInst. Mag = -2.5 * Log10 (Flux) Calculate estimated magnitudes using Reference Star’s magnitude For greater accuracy, correct for colour extinction and colour transforms Target Star (V) Reference Star (C) Check Star (K) StarFlux (ADU)Inst. MagS/NMagCalc. Mag C 4483 -9.13 51 9.88 - V 21484 -10.83 137 - 8.18 [ -10.83 + (9.88 minus -9.13) ] K 904 -7.39 14 - 11.62 [ -7.39 + (9.88 minus -9.13) ]

15. Star Catalogs Catalog Stars Median Median Astrometric Photometric Accuracy Accuracy • SAO 0.25 million stars to mag 9.5 (10 MB) • HIPPARCOS 0.1 million stars to mag 9 0.001” / Proper Motion 0.0015 mag • TYCHO 1 million stars to mag 11.5 (18 MB) 0.025” 0.06 m(Vt) • TYCHO 2 2.5 million stars to mag 12 0.06”, 0.007” (Vt<9) 0.1 m, 0.013 m (Vt<9), • GSC 1.x 19 million ‘stars’ to mag 14 0.3-0.4” 0.2 m • GSC ACT 19 million ‘stars’ to mag 14 • UCAC 2.0 48 million stars to 40 degs, • USNO B1 (subset) 15 million stars above 40 degs 0.2” 0.3 m in 5 colours • USNO SA-2.0 54 million stars to mag 19 (600 MB)USNO A-2.0 526 million stars to mag 20 (6 GB) 0.25” • GSC II (2.2) 435 million stars to mag 19 • GSC II (2.3) 1 billion stars to mag 21 • USNO-B1 1 billion stars to mag x (80 GB) 0.2” 0.3 m • LANDOLT 258 stars, Standard Photometric Fields (UBVRI) 0.01 m ( 5 colours) • HENDEN Quasi-Standard Fields (BVR) • LONEOS 29500 stars, Brian Skiff’s Quasi-Standard (UBVRI) 0.05 m

16. My Own Equipment & Setup Meade 8” LX200 Goto Telescope ST-7e CCD Camera Equatorial Wedge PermanentPier

17. Equipment 2006 Meade 8” LX200 (Goto Telescope) Meade RCX400 ? 1995 Somewhere with less cloud !! Roll-Off Roof Observatory Scotland Scotland 1998 S.England ?? SBIG ST-7e CCD Camera SBIG ST-2000XM ? 2001 CFW-8A Filter Wheel / filters 2004

18. High Level Workflow • Target Selection / Imaging Specification (week/day before + adhoc on the night targets) • Image Acquisition (observing session) • Image Reduction (next day) • Image Analysis (next few days)

19. Magazines Web, Books AcquisitionControl Software Project Lists Target List AIS (Own Software) Other ObjectCatalogs CameraControl Software Camera Simulator Planetarium Software TheSky (Software Bisque) CCDSoft (Software Bisque) Star Catalogs Telescope Simulator Target Selection Flowchart >> DEMO

20. Example Target List

21. Telescope Modelling Software CameraControl Software Telescope Control Software Image Files(.fit) TPoint (Software Bisque) TheSky (Software Bisque) CCDSoft (Software Bisque) Darks Flats Star Catalogs AcquisitionControl Software Log files AIS (Own Software) Observatory Laptop Target List Remote Computer Image Acquisition Flowchart Filter Wheel Goto Telescope / Mount CCD Camera

22. Example Session in Action Buttons allowing targets to be re-ordered or specifications to be changed Control Window

23. Example Target Specification Lalande 21185 / HIP 54035 (Ursa Major)4th closest star system to the Sun8.3 light years distant

24. Example Session in Action Completed

25. Example Raw Image

26. Example Reduced Image File Lalande_21185.20060808.im133011-17.av7x30s.C.FIT Image Linked in TheSky Old Star Positions From GSC Catalog Lalande 21185Position from Hipparcos Catalog Annotated Image for Session’s Web Page Lalande 21185 / HIP 54035 (Ursa Major)4th closest star system to the Sun8.3 light years distant

27. Image Reduction Flowchart Raw Images (.fit) Astro Workbench (Own Software) Sigma Beta (Ray Gralak) Darks Image List Master Darks Master Flats VB Script Flats Excel (Microsoft) Raw Imagesby Bin, Exp, Filter VB Script CCDSoft (Software Bisque) Reduced Images Session Workbook (Inventory) Reduced Imagesby Object / Exp Copy of Reduced Images

29. Example Session Workbook

30. Image Analysis Flowchart ImageHandling Software Planetarium Software Reduced Imagesby Object / Exp TheSky (Software Bisque) CCDSoft (Software Bisque) Star Catalogs AIS (Own Software) Reference files Analysis Control Software VMA (Own Software) Reference files Excel (Microsoft) Log files Data Files Session Workbook(Inventory) Variable Star Results Astrometry Results >> DEMO

31. Example Astrometric Analysis Lalande 21185 / HIP 54035 (Ursa Major)4th closest star system to the Sun Baseline Position

32. Returning to some of our questions about GRB 34 ? What kind of star ? Is it a true binary star ? What are its properties ? Or is simply an optical double ? Groombridge 34 Colour ? Is it moving, which way ? Temperature ? What is it’s orbitial period ? Luminosity ? Size ? Mass ? How far away is it ? Where does it sit ona H-R diagram ? Does it show any brightness or colour variations ?(and if so, what kind & why ? ) What was it’s past ? Does it have any planets ? Could they hold life ? What is it’s future ?

33. Jan Proper Motion Earth Orbit Sun Nearby Star Background / Distant Stars Nearest stars can be expected to show the largest proper motions

34. Barnard’s Star Barnard’s Star

35. Barnard’s Star – Proper Motion Proper Motion 10 arc secs in 1 year For Scale :Tennis Ball at 2.7 km(1.7 miles) For Scale :Tennis Ball at 13.4 km(8 miles)

36. Examination of Proper Motion of GRB 34 From images taken roughly one year apart it can be determined that the two stars (A & B) are moving through space in an identical speed and direction (relative to the Sun) having a proper motion of ~ 2.8 arc secs/year, with PA of 83 deg. We can tell that the stars very probably form a true binary system and must be relatively close to the Sun. 2.8”/year 2.8”/year [ GRB 34 is known to be a binary system with estimated orbital period of 2600 years ]

37. Distance to GRB 34 ? Nearest stars generally show the largest proper motions GRB 34 with Proper Motion of ~ 2.8 arc sec/year could perhaps be estimated to lie at 6 – 20 light years distance Barnard’s Star Kapteyn's Star GRB 34 is actually known to be a binary star system located at 11.7 light years distance Lalande 21185 61 Cygni Wolf 359 But how are the distances determined ? Proxima Centauri GRB 34 Alpha Centauri Sirius

38. Jan Jul Stellar Parallax More Distant Star Earth Orbit Sun Nearby Star Background / Distant Stars Parallax allows us to measure the distance to nearby stars: The larger the parallax, then the closer the star is …this can be quantified and distance determined

39. Earth (Jan) d p Sun Nearby Star Earth (Jul) d = 1 / p d = distance to star, in parsecs (multiply by 3.26 for d in light years) p = parallax angle of the star, in arc seconds Calculating distance using Stellar Parallax Astronomer’s often measure interstellar distances in units of parsecs (pc) where 1 parsec = distance at which 1 AU subtends an angle of 1 arcsec 1 parsec = 206,265 AU 1 AU = 1.496 x 108 km 1 ly = 9.46 x 1012 km 1 parsec = 3.26 ly 1 parsec 1 AU 1 arc sec Sun Earth Orbit

40. Stellar Parallax Background / Distant Stars Gamma Draconis Nearby Star(near Celestial Pole) Nearby Star(near Ecliptic) Jan Earth Orbit Sun Mar Oct Jul Background / Distant Stars

41. 61 Cygni – the ‘flying star’ Robert HookeMade first modern attempt to measure stellar parallax by observing Gamma Draconis in 1669. His equipment was not up to the task and in any case Gamma Draconis’ parallax for him to measure (brightest stars are not necessarily close to the sun) GalileoFirst person to have the idea that parallax could be used to indicate the relative distance to stars. Friedrich Bessel 61 Cygni Gamma Draconis 61 Cygni: the very first star to successfully have its distance determined using parallax. This was by Friedrich Bessel in 1838

42. Jan Jul Parallax & Proper Motion Combined Earth Orbit Sun Nearby Star Background / Distant Stars

43. 61 Cygni - Proper Motion Separation 30.96 arc secs (+/- 0.04)from 104 images (over 13 nights) For Scale :Tennis Ball at 2.7 km(1.7 miles)

44. 61 Cygni – Parallax Indications For Scale :Tennis Ball at 13.4 km(8 miles)

45. 61 Cygni – Parallax, Distance For Scale :Tennis Ball at 67 km(42 miles)

46. Barnard’s Star - Parallax For Scale :Tennis Ball at 26.8 km(18 miles)

47. Apparent Magnitude • Often referred to as simply magnitude in regular speech. • A quantity measuring the brightness of a star - or other object - as seen from the position of the observer (normally at Earth). • Logarithmic scale (based on human eye’s perception of brightness differences) magnitude = -2.5 x Log10 (flux) • Magnitude difference of 5 mag, equivalent to a x100 difference in brightness • Magnitude difference of 1 mag, equivalent to a x 2.512 difference in brightness, (2.512)^5 = 100 • Extends from –ve numbers to +ve numbers (mag 0 is approximately brightness of Vega) • More -ve number numbers are brighter (eg Sun, -26.8 ) • More +ve numbers are dimmer (faintest observed object ~ +25) • Often measured at a particular Pass Band (ie a particular range of wavelengths) e.g. UBV or more commonly today UBVRI V magnitudes corresponding to the magnitude at 480-680 nm (visual) is most commonly used • Magnitudes are obtained by comparing its brightness (flux), with that of standard stars, whose magnitudes have been defined by careful measurement. Note: Standard magnitudes are a measure of the brightness of an object as viewed from above the atmosphere • Colour Indices (eg B-V or V-R) are often used to express the difference in magnitude measured using two different filter bands. Colour Indices (B-V and V-R) are ~ 0.0 for stars of spectral type A0 (eg Vega) • Apparent magnitudes tells us nothing about true brightness of stars, since distances differ considerably.

48. Absolute Magnitude & Distances • Absolute Magnitude • Quantity measuring the intrinsic brightness a star (or other object) • Defined as the apparent magnitude the star would have if viewed from a distance of 10 parsecs (32.6 light year) • MU, MB, MV, MR, MI are absolute magnitude values through U,B,V,R,I bands • Physicists use Luminosity to measure brightness. Luminosity (L) = amount of light energy emitted by the star each second either in watts (joules per second) or as a multiple of the Sun’s luminosity • Distance Modulus • The difference between the apparent magnitude (m) of a star and its absolute magnitude (M) is termed the distance modulus (m-M) • We can relate apparent magnitude (m), absolute magnitude (M) and the distance (d) using the simple, but highly important equation :m – M = 5 x Log10 (d) - 5where d is in parsecs • If we know the apparent and absolute magnitudes of a star, or other object, we can find its distance (d) d = 10^((m - M + 5)/5)

49. c) This star looks red (B-V = 1.5) a) This star looks blue (B-V = -0.1) b) This star looks yellow-white (B-V = 0.6) Intensity Intensity Intensity 3,000 k 12,000 k 6,000 k 500 1500 500 500 1000 1500 1500 1000 1000 Wavelength (nm) Wavelength (nm) Wavelength (nm) Star Colours • A star’s colour is directly related to its surface temperature • The Surface temperature of a star is described by the quantity effective temperature, Te, which is the temperature of blackbody which radiates with the same total flux density as the star • The peak wavelength emission of a blackbody (and thus a star) is given by Wien’s lawλmax (in m) = 0.0029 / T (in K) where λmax in metres & T in kelvins • The Following diagrams show relationship between colour of a star and temperature for 3 hypothetical stars

50. Hertzsprung-Russell (H-R) diagram • Hertzsprung and Russell, working independently around 1910-13, found that stars fell is a regular pattern when their absolute magnitudes (a measure of luminosity) was plotted against either their colour or spectral type(both measures of their surface temperatures). • Graphs of this kind are today known as Hertzsprung-Rusell diagrams or H-R diagrams V. Hot Cool LuminousStars Dim Stars Red Blue