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Chemistry and Kinematics of Stars in Local Group Galaxies
Chemistry and kinematics of stars in Local Group galaxies Giuseppina Battaglia ESO Garching In collaboration with DART (E.Tolstoy, M.Irwin, A.Helmi, V.Hill, B.Letarte, P.Jablonka, K.Venn, M.Shetrone, N.Arimoto, F.Primas, A.Kaufer, T. Szeifert, P. François,T.Abel) Dwarf spheroidal galaxies Small (half-light radius= 0.1-1kpc), devoid of gas, pressure supported SSccuulplpttoorr FFoorrnnaaxx Typical dSph Unusual dSph • Distance: 79 kpc • Distance: 138 kpc • Faint (Lv~ 10^6 Lsun) • Most luminous (Lv~10^7 Lsun) and and metal poor metal rich of MW satellites SFHs from Grebel, Gallagher & Harbeck 2007 (see also Monkiewicz et al. 1999, Stetson et al. 1998, Buonanno et al.1999, Saviane et al. 2000) Time [Gyr] Time [Gyr] Motivation • Galaxy formation on the smallest scales – Evolution and distribution of stellar populations – Chemical enrichment histories – All dSphs contain > 10 Gyr old stars => early universe • Most dark-matter dominated galaxies – Measure dark-matter distribution – Constrain the nature of dark-matter (warm, cold...) • Galaxy formation: building blocks of large galaxies? TThhee LLooccaall GGrroouupp Grebel et al. 2000 Large Dwarf ellipticals (dE); Dwarf irregulars dSphs/dIrrs spirals dwarf spheroidals (dSphs) (dIrr) dI rr Large majority DDAARRTT LLaarrggee PPrrooggrraamm aatt EESSOO • 4 dSphs in the MW halo: Sextans, Sculptor, Fornax, Carina (HR only) • Extended ESO/WFI imaging (CMD) probable members • VLT/FLAMES Low Resolution (LR) X probable non members spectra of 100s Red Giant Branch (RGB) stars in CaII triplet (CaT) region -
Tip of the Red Giant Branch Distance for the Sculptor Group Dwarf ESO 540-032?
A&A 371, 487–496 (2001) Astronomy DOI: 10.1051/0004-6361:20010389 & c ESO 2001 Astrophysics Tip of the red giant branch distance for the Sculptor group dwarf ESO 540-032? H. Jerjen1 and M. Rejkuba2,3 1 Research School of Astronomy and Astrophysics, The Australian National University, Mt Stromlo Observatory, Cotter Road, Weston ACT 2611, Australia 2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei M¨unchen, Germany e-mail: [email protected] 3 Department of Astronomy, P. Universidad Cat´olica, Casilla 306, Santiago 22, Chile Received 19 January 2001 / Accepted 9 March 2001 Abstract. We present the first VI CCD photometry for the Sculptor group galaxy ESO 540-032 obtained at the Very Large Telescope UT1+FORS1. The (I, V − I) colour-magnitude diagram indicates that this intermediate- type dwarf galaxy is dominated by old, metal-poor ([Fe/H] ≈−1.7 dex) stars, with a small population of slightly more metal-rich ([Fe/H] ≈−1.3 dex), young (age 150 − 500 Myr) stars. A discontinuity in the I-band luminosity function is detected at I0 =23.44 0.09 mag. Interpreting this feature as the tip of the red giant branch and adopting MI = −4.20 0.10 mag for its absolute magnitude, we have determined a Population II distance modulus of (m − M)0 =27.64 0.14 mag (3.4 0.2 Mpc). This distance confirms ESO 540-032 as a member of the nearby Sculptor group but is significantly larger than a previously reported value based on the Surface Brightness Fluctuation (SBF) method. -
Naming the Extrasolar Planets
Naming the extrasolar planets W. Lyra Max Planck Institute for Astronomy, K¨onigstuhl 17, 69177, Heidelberg, Germany [email protected] Abstract and OGLE-TR-182 b, which does not help educators convey the message that these planets are quite similar to Jupiter. Extrasolar planets are not named and are referred to only In stark contrast, the sentence“planet Apollo is a gas giant by their assigned scientific designation. The reason given like Jupiter” is heavily - yet invisibly - coated with Coper- by the IAU to not name the planets is that it is consid- nicanism. ered impractical as planets are expected to be common. I One reason given by the IAU for not considering naming advance some reasons as to why this logic is flawed, and sug- the extrasolar planets is that it is a task deemed impractical. gest names for the 403 extrasolar planet candidates known One source is quoted as having said “if planets are found to as of Oct 2009. The names follow a scheme of association occur very frequently in the Universe, a system of individual with the constellation that the host star pertains to, and names for planets might well rapidly be found equally im- therefore are mostly drawn from Roman-Greek mythology. practicable as it is for stars, as planet discoveries progress.” Other mythologies may also be used given that a suitable 1. This leads to a second argument. It is indeed impractical association is established. to name all stars. But some stars are named nonetheless. In fact, all other classes of astronomical bodies are named. -
The Constellation Microscopium, the Microscope Microscopium Is A
The Constellation Microscopium, the Microscope Microscopium is a small constellation in the southern sky, defined in the 18th century by Nicolas Louis de Lacaille in 1751–52 . Its name is Latin for microscope; it was invented by Lacaille to commemorate the compound microscope, i.e. one that uses more than one lens. The first microscope was invented by the two brothers, Hans and Zacharius Jensen, Dutch spectacle makers of Holland in 1590, who were also involved in the invention of the telescope (see below). Lacaille first showed it on his map of 1756 under the name le Microscope but Latinized this to Microscopium on the second edition published in 1763. He described it as consisting of "a tube above a square box". It contains sixty-nine stars, varying in magnitude from 4.8 to 7, the lucida being Gamma Microscopii of apparent magnitude 4.68. Two star systems have been found to have planets, while another has a debris disk. The stars that now comprise Microscopium may formerly have belonged to the hind feet of Sagittarius. However, this is uncertain as, while its stars seem to be referred to by Al-Sufi as having been seen by Ptolemy, Al-Sufi does not specify their exact positions. Microscopium is bordered Capricornus to the north, Piscis Austrinus and Grus to the west, Sagittarius to the east, Indus to the south, and touching on Telescopium to the southeast. The recommended three-letter abbreviation for the constellation, as adopted Seen in the 1824 star chart set Urania's Mirror (lower left) by the International Astronomical Union in 1922, is 'Mic'. -