DOCSLIB.ORG

1153-1160, November 1987 AGES of GLOBULAR CLUSTERS

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
1153-1160, November 1987 AGES of GLOBULAR CLUSTERS Publications of the Astronomical Society of the Pacific 99: 1153-1160, November 1987 AGES OF GLOBULAR CLUSTERS CHARLES J. PETERSON Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211 and Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics 5071 West Saanich Road, Victoria, BC V9A 2Y9, Canada Received 1986 August 11. ABSTRACT Ages have been calculated for 41 globular clusters for which color-magnitude diagram studies allow a determination of the luminosity difference between the horizontal-branch and the main-se- quence turnoff point. The data indicate only weak support for a slight difference in age between clusters in the inner halo and those in the outer halo. No correlation between cluster ages and cluster metallicities is found. Key words: globular clusters-ages I. Introduction II. The Data Globular cluster color-magnitude diagrams provide Our sample of data is taken from an essentially com- data not only about individual cluster properties, but also plete survey of all modern color-magnitude diagram stud- yield information that may be used to study the structure ies in the standard UBVRl photometric system (Peterson and evolution of the Galaxy and to set a constraint upon its 1986) supplemented by a few studies which have ap- age and the age of the universe. In particular, various peared more recently. Neglecting a number of older studies have been made in recent years to obtain ages for studies in which it is known that observational errors globular clusters (Gratton 1985; Sandage 1986, and refer- affect the fainter end of the magnitude scale, we find there ences cited therein) and to search for an age-galactocen- are approximately 70 studies of 41 clusters to or below the tric radius relationship that would give clues to the nature level of the main-sequence turnoff. For each of these of the collapse of the Galaxy halo. In particular, Gratton clusters we have determined AV(TO —HB), the differ- (1985), from an analysis based on color-magnitude dia- ence in visual magnitude between the main-sequence gram information for 26 clusters, argued that clusters in turnoff and the horizontal-branch level. Wherever possi- the inner halo (fíGC < 15 kpc) are coeval, with a mean age ble, we have taken the horizontal-branch magnitude 3-5 X 109 years older than the clusters of the outer halo V(HB) as the mean magnitude of the horizontal-branch which continued to form during a delayed outer halo stars at the position of the RR Lyrae gap. For clusters with collapse; these results are consistent with the models of very red or very blue horizontal branches, it has been Tinsley and Larson (1978) for the formation of the Galaxy, assumed that the best estimate of this magnitude is equal but contrast with the general consensus that globular to the blue edge of the red horizontal-branch star distri- clusters are of the same age (Sandage 1982a ; Carney 1983; bution or the red edge of the blue horizontal-branch star Burstein 1985). distribution, respectively. For those clusters for which At the present time, published data are now available red horizontal-branch stars have been used, we must note for 15 additional clusters. We have also surveyed the that an additional uncertainty is introduced into our cal- literature to intercompare independent studies of the culations as VandenBerg (1986) has shown their luminosi- same clusters to allow an external estimation of the accu- ties to be dependent on the abundance ratio of the CNO racy of color-magnitude diagram parameters that may be elements to Fe. used for estimation of cluster ages. Our new analysis of The turnoff magnitude V (TO) is defined as the magni- this somewhat larger sample of cluster data does not tude at the bluest position of the main sequence. To be as confirm the strong age-galactocentric radius relation consistent as possible, these values have been deter- found by Gratton. Within the accuracy of our derived mined directly from published color-magnitude diagrams ages and within the assumption that the helium abun- or from tabulated fiducial values for the main sequence. dance is constant, all clusters appear to be approximately Our determinations of AV(TO —HB), are given in coeval. Table I together with the literature references. In Table 1153 © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 1154 CHARLES J. PETERSON II are given our adopted values of the mean level of the show the distribution of AV(TO —HE). The standard de- horizontal branch V(HB) at the position of the RR Lyrae viation of the distribution is 0.16 magnitude, a value that gap, a value of the extinction E{B—V), and the average is consistent with the expected error in the determination AV(TO —HE) of the values from the individual studies of the magnitude difference. As has been emphasized, for together with the standard deviation of the mean. Ν example, by Smith et al. (1986), the distribution of stars in represents the number of studies used in the determina- a color-magnitude diagram at the position of the main-se- tion of this average. For the metallicity of the clusters, we quence turnoif has a constant {Β —V) color for a luminos- have taken [Fe/H] directly from the study of Pilachowski ity range of approximately 0.5 magnitude in V ; thus, the (1984), with the exceptions of five objects for which we intrinsic ability to determine V(TO) is subject to an error have found [Fe/H] from a new calibration against of 0.1 to 0.2 magnitude. Coupled with the observational (ß-y)0)g and/or AV1.4 = V (red giants at (B-V)o= 1.40) error in determination of V(HE) (which is particularly — V (HE) (Fig. 1). The derivations of the cluster ages t and uncertain for several clusters that have very blue horizon- the galactocentric radial distances RGC are discussed in tal branches), the distribution shown in Figure 2 could Section III. easily be explained solely by measurement error. In Fig- The data at this point already give two indications of the ure 3a we show the same data as a function of metallicity. result that we will obtain in Section III, namely that the As discussed in Section III, the computation of age de- majority of clusters appear to be the same age within the pends somewhat on [Fe/H]. In the figure we have shown uncertainties of the observational error. In Figure 2 we the expected slope of an isochrone which can be seen to TABLE I References for Color Magnitude Diagrams Cluster Δν(ΤΟ-ΗΒ) Reference Cluster AV(TO-HB) Reference NGC 104 3.45 Tifft (1963) NGC 5904 3.65 Richer and Fahlman (1987) 3.50 Hesser and Hartwick (1977), NGC 6121 3.18 Alcaino and Liller (1984) Harris, Hesser, and Atwood (1983) 3.6 Richer and Fahlman (1984) 3.75 Cannon (1981) NGC 6171 3.58 Da Costa, Mould, and Ortolani (1984) 3.73 Gratton (1985) 3.75 Sandage and Roques (1984) 3.6 Hesser et al. (1987) NGC 6205 3.4 Sandage (1970) NGC 288 3.8 Samus' and Shugarov (1978) 3.19 Richer and Fahlman (1986) 3.5 Alcaino and Liller (1980c) NGC 6218 3.9 Mironov et al. (1984) 3.8 Harris, Hesser, and Atwood (1983) NGC 6229 3.45 Cohen (1985) 3.5 Buonanno et al. (1984b, 1984c) NGC 6254 3.75 Samus' and Shugarov (1983) 3.8 Olszewski, Canterna, and Harris (1984) NGC 6341 3.45 Sandage and Katem (1983) 3.9 Penny (1984) 3.55 Christian and Heasley (1986) NGC 362 3.55 Gratton (1985) NGC 6352 3.6 Nemec, Hesser, and Ugarte (1981) 3.32 Boite (1987) NGC 6362 3.41 Alcaino and Lüler (1986a) Eridanus 3.5 Ortolani and Gratton (1986) NGC 6397 3.7 Cannon (1974) Reticulum 3.4 Gratton and Ortolani (1987) 3.8 Alcaino and Liller (1980a) NGC 1904 3.44 Gratton and Ortolani (1986) NGC 6535 3.5 Anthony-Twarog and Twarog (1985) 3.85 Heasley, Janes, and Christian (1986) NGC 6656 3.4 Alcaino and Liller (1983) NGC 2298 3.31 Gratton and Ortolani (1986) NGC 6752 3.7 Wesselink (1974) 3.4 Alcaino and Liller (1986b) 3.5 Carney (1979) NGC 2808 3.6 Buonanno et al. (1984a) 3.5 Cannon (1981) 3.55 Gratton and Ortolani (1986) 3.63 Grenon and Blecha (1984) Pal 3 3.5 Ortolani and Gratton (1986) 3.75 Buonanno et al. (1986) NGC 3201 3.33 Alcaino and Liller (1981) 3.72 Penny and Dickens (1986) 3.50 Penny (1984) NGC 6809 3.7 Penny (1984) Pal 4 3.2 Reed and Harris (1986) Pal 11 3.2 Cudworth and Schommer (1984) 3.33 Christian and Heasley (1986) NGC 6838 3.55 Arp and Hartwick (1971) NGC 4590 3.5 Penny (1984) NGC 7006 3.56 Cohen (1985) 3.35 McClure et al. (1987) 3.4 Ortolani (1986) NGC 5053 3.35 Walker, Pike, and McGee (1976) NGC 7078 3.33 Sandage and Katem (1977) NGC 5139 3.5 Da Costa and Villumsen (Í981) 3.33 Fahlman, Richer, and VandenBerg (1985) 3.8 Cannon (1981) 3.7 Harris and Hesser (1987) 3.58 Gratton (1985) NGC 7089 3.25 Samus' and Shugarov (1979) 3.8 Walker (1986) 3.65 Inman and Carney (1982) NGC 5272 3.4 Sandage (1970) NGC 7099 3.6 Piotto et al. (1987) NGC 5466 3.32 Cohen (1985) Pal 12 3.2 Harris and Canterna (1980) 3.6 Nemec and Harris (1987) 3.2 Stetson and Smith (1987) Pal 5 3.34 Ortolani (1985) Pal 13 3.29 Ortolani, Rosino, and Sandage (1985) 3.3 Smith et al.
Load more

Recommended publications
  • Broad-Band X-Ray/Γ-Ray Spectra and Binary Parameters of GX 339
    Mon. Not. R. Astron. Soc. 000, 1–17 (1998) Printed 5 March 2018 (MN LATEX style file v1.4) Broad-band X-ray/γ-ray spectra and binary parameters of GX 339–4 and their astrophysical implications Andrzej A. Zdziarski1, Juri Poutanen2, Joanna Miko lajewska1, Marek Gierli´nski3,1, Ken Ebisawa4, and W. Neil Johnson5 1N. Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland 2Stockholm Observatory, S-133 36 Saltsj¨obaden, Sweden 3Astronomical Observatory, Jagiellonian University, Orla 171, 30-244 Cracow, Poland 4Laboratory for High Energy Astrophysics, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA 5E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DC 20375, USA Accepted 1998 July 28. Received 1998 January 2 ABSTRACT We present X-ray/γ-ray spectra of the binary GX 339–4 observed in the hard state simultaneously by Ginga and CGRO OSSE during an outburst in 1991 September. The Ginga X-ray spectra are well represented by a power law with a photon spectral index of Γ ≃ 1.75 and a Compton reflection component with a fluorescent Fe Kα line corresponding to a solid angle of an optically-thick, ionized, medium of ∼ 0.4×2π. The OSSE data (> 50 keV) require a sharp high-energy cutoff in the power-law spectrum. The broad-band spectra are very well modelled by repeated Compton scattering in a thermal plasma with an optical depth of τ ∼ 1 and kT ≃ 50 keV. We also study the distance to the system and find it to be ∼> 3 kpc, ruling out earlier determinations of ∼ 1 kpc.
    [Show full text]
  • First Scientific Results with the VLT in Visitor and Service Modes
    No. 98 – December 1999 First Scientific Results with the VLT in Visitor and Service Modes Starting with this issue, The Messenger will regularly include scientific results obtained with the VLT. One of the results reported in this issue is a study of NGC 3603, the most massive visible H II region in the Galaxy, with VLT/ISAAC in the near-infrared Js, H, and Ks-bands and HST/WFPC2 at Hα and [N II] wavelengths. These VLT observations are the most sensitive near-infrared observations made to date of a dense starburst region, allowing one to in- vestigate with unprecedented quality its low-mass stellar population. The sensitivity limit to stars detected in all three bands corresponds to 0.1 M0 for a pre-main-sequence star of age 0.7 Myr. The observations clearly show that sub-solar-mass stars down to at least 0.1 M0 do form in massive starbursts (from B. Brandl, W. Brandner, E.K. Grebel and H. Zinnecker, page 46). Js versus Js–Ks colour-magnitude diagrams of NGC 3603. The left-hand panel contains all stars detected in all three wave- bands in the entire field of view (3.4′×3.4′, or 6 pc × 6 pc); the centre panel shows the field stars at r > 75″ (2.25 pc) around the cluster, and the right-hand panel shows the cluster population within r < 33″ (1pc) with the field stars statistically subtracted. The dashed horizontal line (left-hand panel) indicates the detection limit of the previous most sensitive NIR study (Eisenhauer et al.
    [Show full text]
  • The History of Star Formation in the Galactic Young Open Cluster NGC 6231
    Triggered Star Formation in a Turbulent ISM Proceedings IAU Symposium No. 237, 2006 c 2007 International Astronomical Union B. G. Elmegreen & J. Palouˇs, eds. doi:10.1017/S1743921307002736 The history of star formation in the Galactic young open cluster NGC 6231 Mario E. van den Ancker1 1European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany e-mail: [email protected] Abstract. We study the star formation history of the galactic young open cluster NGC 6231 using new, deep, wide-field BV RI imaging. Contrary to previous suggestions, we do not find a lack of low-mass cluster members; our derived mass function is compatible with a Salpeter IMF. The star formation history of NGC 6231 appears to be bi-modal, with a first wave of star formation activity 3–5 Myr ago, followed by a new generation of stars forming ∼ 1 Myr ago. Keywords. Star Formation, Pre-main sequence Stars, Open clusters and associations The star formation history of the rich open cluster NGC 6231 has been hotly debated in the literature ever since the suggestion by Eggen (1976) that a violent process must have triggered star formation in the region. In the largest photometric study of the region to date, Sung et al. (1998) suggested an abrupt decrease in the number of low-mass stars in NGC 6231 - giving further credibility to a scenario in which star formation in this region may have been triggered. Interestingly, Reed & Cudworth (2003), recently found that the trajectory of the globular cluster NGC 6397 intersected that of the natal cloud of NGC 6231 around five million years ago - close to the estimated age of NGC 6231 – thus providing a plausible candidate for the triggering mechanism.
    [Show full text]
  • Publications of the Astronomical Society of the Pacific 106: 404-412, 1994 April
    Publications of the Astronomical Society of the Pacific 106: 404-412, 1994 April CCD Photometry of the Galactic Globular Cluster NGC 6535 in the Β and Passbands Ata Sarajedini1 Kitt Peak National Observatory, National Optical Astronomy Observatories,2 P.O. Box 26732, Tucson, Arizona 85726-6732 Electronic mail: [email protected] Received 1993 October 15; accepted 1994 February 1 ABSTRACT. The first CCD color-magnitude diagram (CMD) in Β and V is presented for the Galactic globular cluster NGC 6535. From this CMD, which extends below the main-sequence turnoff, we draw the following conclusions: (1) The horizontal branch (HB) is predominantly blue in nature with no RR Lyrae variables known to be cluster members. Nonetheless, based on a comparison with clusters which have blue HBs and RR Lyraes (Ml5 and M79), we infer a mean HB magnitude of <^RR> = 15.73 ±0.11 for NGC 6535. (2) Again, via a direct comparison with the blue HBs of M15 and M79, we derive a cluster reddening oíE{B—V) =0.44±0.02. (3) When combined with the apparent color of the red-giant branch at the level of the HB, (B—V)g= 1.18 ±0.02, the derived reddening yields a metal abundance of [Fe/H] = —1.85 ±0.10, similar to that of NGC 6397. (4) Application of the AFT0_hb and Δ(5— F)SGB_To cluster dating techniques reveals no perceptible age difference between NGC 6535 and NGC 6397. (5) A significant population of nine blue-straggler candidates is detected in NGC 6535. However, this is too few to facilitate a meaningful analysis of their radial distribution.
    [Show full text]
  • A Basic Requirement for Studying the Heavens Is Determining Where In
    Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun­ damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short).
    [Show full text]
  • Arxiv:2012.05245V2 [Astro-Ph.GA] 5 May 2021
    Draft version May 6, 2021 Typeset using LATEX twocolumn style in AASTeX63 Charting the Galactic acceleration field I. A search for stellar streams with Gaia DR2 and EDR3 with follow-up from ESPaDOnS and UVES Rodrigo Ibata 1 | Khyati Malhan 2 | Nicolas Martin 1, 3 | Dominique Aubert1 | Benoit Famaey 1 | Paolo Bianchini 1 | Giacomo Monari 1 | Arnaud Siebert 1 | Guillaume F. Thomas 4, 5 | Michele Bellazzini 6 | Piercarlo Bonifacio7 | Elisabetta Caffau7 | Florent Renaud 8 | arXiv:2012.05245v2 [astro-ph.GA] 5 May 2021 1Universit´ede Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, F-67000 Strasbourg, France 2The Oskar Klein Centre, Department of Physics, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden 3Max-Planck-Institut f¨urAstronomie, K¨onigstuhl17, D-69117, Heidelberg, Germany 4Instituto de Astrof´ısica de Canarias, E-38205 La Laguna, Tenerife, Spain 5Universidad de La Laguna, Dpto. Astrof´ısica, E-38206 La Laguna, Tenerife, Spain 6INAF - Osservatorio di Astrofisica e Scienza dello Spazio, via Gobetti 93/3, I-40129 Bologna, Italy 7GEPI, Observatoire de Paris, Universit´ePSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France 8Department of Astronomy and Theoretical Physics, Lund Observatory, Box 43, 221 00 Lund, Sweden Corresponding author: Rodrigo Ibata [email protected] 2 Ibata et al. Submitted to ApJ ABSTRACT We present maps of the stellar streams detected in the Gaia Data Release 2 (DR2) and Early Data Release 3 (EDR3) catalogs using the STREAMFINDER algorithm. We also report the spectroscopic follow-up of the brighter DR2 stream members obtained with the high-resolution CFHT/ESPaDOnS and VLT/UVES spectrographs as well as with the medium-resolution NTT/EFOSC2 spectrograph.
    [Show full text]
  • Nuclear Astrophysics: the Unfinished Quest for the Origin of the Elements
    Nuclear astrophysics: the unfinished quest for the origin of the elements Jordi Jos´e Departament de F´ısica i Enginyeria Nuclear, EUETIB, Universitat Polit`ecnica de Catalunya, E-08036 Barcelona, Spain; Institut d’Estudis Espacials de Catalunya, E-08034 Barcelona, Spain E-mail: [email protected] Christian Iliadis Department of Physics & Astronomy, University of North Carolina, Chapel Hill, North Carolina, 27599, USA; Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA E-mail: [email protected] Abstract. Half a century has passed since the foundation of nuclear astrophysics. Since then, this discipline has reached its maturity. Today, nuclear astrophysics constitutes a multidisciplinary crucible of knowledge that combines the achievements in theoretical astrophysics, observational astronomy, cosmochemistry and nuclear physics. New tools and developments have revolutionized our understanding of the origin of the elements: supercomputers have provided astrophysicists with the required computational capabilities to study the evolution of stars in a multidimensional framework; the emergence of high-energy astrophysics with space-borne observatories has opened new windows to observe the Universe, from a novel panchromatic perspective; cosmochemists have isolated tiny pieces of stardust embedded in primitive meteorites, giving clues on the processes operating in stars as well as on the way matter condenses to form solids; and nuclear physicists have measured reactions near stellar energies, through the combined efforts using stable and radioactive ion beam facilities. This review provides comprehensive insight into the nuclear history of the Universe arXiv:1107.2234v1 [astro-ph.SR] 12 Jul 2011 and related topics: starting from the Big Bang, when the ashes from the primordial explosion were transformed to hydrogen, helium, and few trace elements, to the rich variety of nucleosynthesis mechanisms and sites in the Universe.
    [Show full text]
  • ¼¼Çwªâðw¦¹Á¼ºëw£Àêëw ˆ†ˆ€ «ÆÊ¿Àäàww«¸ÂÀ ‰‡‡Œ†ˆ‰†‰Œ
    ¼¼ÇwªÂÐw¦¹Á¼ºËw£ÀÊËw II - C ll r l 400 e e l G C k i 200 r he Dec. P.A. w R.A. Size Size Chart N a he ss d l Object Type Con. Mag. Class t NGC Description l AS o o sc e s r ( h m ) max min No. C a ( ' ) ( ) sc R AAS e r e M C T e B H H NGC 7192 GALXY IND 22 06.8 -64 19 11.2 1.9 m 1.8 m Elliptical pB,S,R,pmbM 134 NGC 7219 GALXY TUC 22 13.1 -64 51 12.5 1.7 m 1 m 27 SBa pB,S,R,2st nr 134 NGC 7329 GALXY TUC 22 40.4 -66 29 11.3 3.7 m 2.7 m 107 SBbc Ring pB,pS,mE90 134 NGC 7417 GALXY TUC 22 57.8 -65 02 12.3 1.9 m 1.3 m 2 SBab Ring pB,cS,R,gpmbM 134 NGC 7637 GALXY OCT 23 26.5 -81 55 12.5 2.1 m 1.9 m Sc vF,pL,R,vlbM,* nr 134 «ÆÊ¿ÀÄÀww«¸ÂÀ ¼¼ÇwªÂÐw¦¹Á¼ºËw£ÀÊËw II - C ll r l 400 e e l G C k i 200 r he Dec. P.A. w R.A. Size Size Chart N a he ss d l Object Type Con. Mag. Class t NGC Description l AS o o sc e s r ( h m ) max min No. C a ( ' ) ( ) sc R AAS e r e M C T e B H H Mel 227 OPNCL OCT 20 12.1 -79 19 5.3 50.0 m II 2 p 135 NGC 6872 GALXY PAV 20 17.0 -70 46 11.8 6.3 m 2.2 m 66 SBb/P F,pS,lE,glbM,1st of 4 135 NGC 6876 GALXY PAV 20 18.3 -70 52 11.1 3 m 2.6 m 80 E3 pB,S,R,eS* sf,2nd of 4 135 NGC 6877 GALXY PAV 20 18.6 -70 51 12.2 2 m 1 m 169 E6 vF,vS,R,3rd of 4 135 NGC 6880 GALXY PAV 20 19.5 -70 52 12.2 2.1 m 1.3 m 35 SBO-a F,S,R,r,vS* att,4 of 4 135 NGC 6920 GALXY OCT 20 44.0 -80 00 12.5 1.8 m 1.5 m SO pB,cS,R,psmbM 135 NGC 6943 GALXY PAV 20 44.6 -68 45 11.4 4 m 2.2 m 130 SBc pF,L,mE,vglbM vS* 135 IC 5052 GALXY PAV 20 52.1 -69 12 11.2 5.9 m 0.9 m 143 SBcd F,L,eE 140 deg 135 NGC 7020 GALXY PAV 21 11.3 -64 02 11.8 3.5 m 1.6 m 165 SBO-a Ring pB,cS,lE,pgbM 135 NGC 7083 GALXY IND 21 35.7 -63 54 11.2 3.6 m 2.1 m 5 Sbc pF,cL,vlE,vgpmbM,r 135 NGC 7096 GALXY IND 21 41.3 -63 55 11.9 1.8 m 1.6 m 130 Sa vF,S,R,vS** nf 135 NGC 7098 GALXY OCT 21 44.3 -75 07 11.3 4 m 2.6 m 74 SB Ring pF,R,g,psmbM,am st 135 NGC 7095 GALXY OCT 21 52.4 -81 32 11.5 4 m 3.3 m Sc F,pL,R,vglbM,*13 inv 135 «ÆÊ¿ÀÄÀww«¸ÂÀ ¼¼ÇwªÂÐw¦¹Á¼ºËw£ÀÊËw II - C ll r l 400 e e l G C k i 200 r he Dec.
    [Show full text]
  • The Hertzsprung-Russell Diagram Help Sheet
    School of Physics and Astronomy Edgbaston Birmingham B15 2TT The Hertzsprung-Russell Diagram Help Sheet Setting up the Telescope What is the wavelength range of an optical telescope? Approx. 400 - 700 nm Locating the Star Cluster Observing the sky from the Northern hemisphere, which star remains fixed in the sky whilst the other stars rotate around it? In which direction do they rotate? North Star/Pole Star/Polaris Stars rotate anticlockwise around Polaris Observing the Star Cluster - Stellar Observation What is the difference between the apparent magnitude and the absolute magnitude of a star? The apparent magnitude is how bright the star appears from Earth. The absolute magnitude is how bright the star would appear if it was 10pc away from Earth. Part 1 - Distance to the Star Cluster What is the distance to the star cluster in lightyears? 136 pc = 444 lightyears Conversion: 1 pc = 3.26 lightyears Why might the distance to the cluster you have calculated differ from the literature value? Uncertainty in fit of ZAMS (due to outlying stars, for example), hence uncertainty in distance modulus and hence distance. Part 2 - Age of the Star Cluster Why might there be an uncertainty in the age of the cluster determined by this method? Uncertainty in fit of isochrone; with 2 or 3 parameters to fit it can be difficult to reproduce the correct shape. Also problem with outlying stars, as explained in the manual. How does the age you have calculated compare to the age of the universe? Age of universe ~ 13.8 GYr Part 3 - Comparison of Star Clusters Consider the shape of the CMD for the Hyades.
    [Show full text]
  • MAD Science Demonstration Proposal a New Spin to Constrain the Absolute Age of Metal Rich Globular Clusters
    MAD Science Demonstration Proposal A new spin to constrain the absolute age of Metal Rich Globular Clusters Investigators Institute EMAIL N. Sanna Rome II Univ. [email protected] G. Bono, A. Calamida, L. Pulone INAF–OAR bono/calamida/[email protected] R. Buonanno, A. Di Cecco Rome II Univ. buonanno/[email protected] E. Marchetti ESO [email protected] M. Monelli IAC [email protected] S. Ortolani Padua Univ. [email protected] P.B. Stetson DAO [email protected] A.R. Walker CTIO [email protected] Abstract: We plan to collect accurate and deep J, K-band photometry of the Galactic Globular Clusters (GGCs) NGC 6352 and NGC 6496. The new NIR data will provide a unique opportunity to constrain their absolute age with an accuracy of the order of 1 Gyr. Together with deep optical data (HST, ground-based), these observations will provide a robust discrimination between cluster and field stars (color-color plane), and thus accurate luminosity functions from the turn-off region down to the regime of very-low-mass stars. Scientific Case: The absolute age of GGCs is the crossroad of several astrophysical problems. It provides (a) a lower limit to the age of the universe, (b) robust constraints on stellar evolutionary models, and (c) an accurate chronology for the assembly of the halo, bulge, and disk of the Milky Way (Buonanno et al. 1998, A&A, 333, 505; Stetson et al. 1999, AJ, 117, 247; Rosenberg et al. 1999, AJ, 118, 2306; Salaris et al. 1998, A&A, 335, 943; Gratton et al.
    [Show full text]
  • Proto-Planetary Nebula Observing Guide
    Proto-Planetary Nebula Observing Guide www.reinervogel.net RA Dec CRL 618 Westbrook Nebula 04h 42m 53.6s +36° 06' 53" PK 166-6 1 HD 44179 Red Rectangle 06h 19m 58.2s -10° 38' 14" V777 Mon OH 231.8+4.2 Rotten Egg N. 07h 42m 16.8s -14° 42' 52" Calabash N. IRAS 09371+1212 Frosty Leo 09h 39m 53.6s +11° 58' 54" CW Leonis Peanut Nebula 09h 47m 57.4s +13° 16' 44" Carbon Star with dust shell M 2-9 Butterfly Nebula 17h 05m 38.1s -10° 08' 33" PK 10+18 2 IRAS 17150-3224 Cotton Candy Nebula 17h 18m 20.0s -32° 27' 20" Hen 3-1475 Garden-sprinkler Nebula 17h 45m 14. 2s -17° 56' 47" IRAS 17423-1755 IRAS 17441-2411 Silkworm Nebula 17h 47m 13.5s -24° 12' 51" IRAS 18059-3211 Gomez' Hamburger 18h 09m 13.3s -32° 10' 48" MWC 922 Red Square Nebula 18h 21m 15s -13° 01' 27" IRAS 19024+0044 19h 05m 02.1s +00° 48' 50.9" M 1-92 Footprint Nebula 19h 36m 18.9s +29° 32' 50" Minkowski's Footprint IRAS 20068+4051 20h 08m 38.5s +41° 00' 37" CRL 2688 Egg Nebula 21h 02m 18.8s +36° 41' 38" PK 80-6 1 IRAS 22036+5306 22h 05m 30.3s +53° 21' 32.8" IRAS 23166+1655 23h 19m 12.6s +17° 11' 33.1" Southern Objects ESO 172-7 Boomerang Nebula 12h 44m 45.4s -54° 31' 11" Centaurus bipolar nebula PN G340.3-03.2 Water Lily Nebula 17h 03m 10.1s -47° 00' 27" PK 340-03 1 IRAS 17163-3907 Fried Egg Nebula 17h 19m 49.3s -39° 10' 37.9" Finder charts measure 20° (with 5° circle) and 5° (with 1° circle) and were made with Cartes du Ciel by Patrick Chevalley (http://www.ap-i.net/skychart) Images are DSS Images (blue plates, POSS II or SERCJ) and measure 30’ by 30’ (http://archive.stsci.edu/cgi- bin/dss_plate_finder) and STScI Images (Hubble Space Telescope) Downloaded from www.reinervogel.net version 12/2012 DSS images copyright notice: The Digitized Sky Survey was produced at the Space Telescope Science Institute under U.S.
    [Show full text]
  • Atlas Menor Was Objects to Slowly Change Over Time
    C h a r t Atlas Charts s O b by j Objects e c t Constellation s Objects by Number 64 Objects by Type 71 Objects by Name 76 Messier Objects 78 Caldwell Objects 81 Orion & Stars by Name 84 Lepus, circa , Brightest Stars 86 1720 , Closest Stars 87 Mythology 88 Bimonthly Sky Charts 92 Meteor Showers 105 Sun, Moon and Planets 106 Observing Considerations 113 Expanded Glossary 115 Th e 88 Constellations, plus 126 Chart Reference BACK PAGE Introduction he night sky was charted by western civilization a few thou - N 1,370 deep sky objects and 360 double stars (two stars—one sands years ago to bring order to the random splatter of stars, often orbits the other) plotted with observing information for T and in the hopes, as a piece of the puzzle, to help “understand” every object. the forces of nature. The stars and their constellations were imbued with N Inclusion of many “famous” celestial objects, even though the beliefs of those times, which have become mythology. they are beyond the reach of a 6 to 8-inch diameter telescope. The oldest known celestial atlas is in the book, Almagest , by N Expanded glossary to define and/or explain terms and Claudius Ptolemy, a Greco-Egyptian with Roman citizenship who lived concepts. in Alexandria from 90 to 160 AD. The Almagest is the earliest surviving astronomical treatise—a 600-page tome. The star charts are in tabular N Black stars on a white background, a preferred format for star form, by constellation, and the locations of the stars are described by charts.
    [Show full text]