THE SCALE OF THE UNIVERSE DEBATE IN 1996Bonnell, Jerry T.; Nemiroff, Robert J.; Goldstein, Jeffrey J.
doi: 10.1086/133835pmid: N/A
On April 21, 1996 Sidney van den Bergh and Gustav Tammann engaged in a public debate entitled "The Scale of the Universe". The arguments they prsented focused on recently determined and still controversial values of the Hubble Constant. The program was moderated by John Bahcall with lectures on the background and history behind humanity's quest for the scale of the universe given by Owen Gingerich and Virginia Trimble. These introductory lectures along with the arguments presented by the 1996 debates are re-created in the following papers. This debate was of the same title and held in the same auditorium as the "Great Debate" between Heber Curtis and Harlow Shapley in 1920. Here we discuss some of the issues surrounding the organization and inspiration for the 1996 debate. Like the 1920 debate, the 1996 debate was not intended instantly to resolve a disagreement. Instead it is hoped that this debate and the written contributions will stand as educational tools, summarizing the arguments behind today's Hubble Constant controversy, and will help provide a framework for evaluating progress in this field as the century, which saw its creation, draws to a close. Together with last year's debate, the Distance Scale to Gamma Ray Bursts (Nemiroff 1995), these papers may also provide a clue as to how scientists think.
THE SCALE OF THE UNIVERSE: A CURTAIN-RAISER IN FOUR ACTS AND FOUR MORALSGingerich, Owen
doi: 10.1086/133836pmid: N/A
This concise and highly selective introduction to the distance-scale debate, from antiquity to Hubble's paper of 1924 on the distance to M31, provides some key quotations and references. The first section describes the early Greek determinations of the distances of the sun and moon. The second part discusses the distances to the stars, from Copernicus to Huygens. Section 3 skips to the early twentieth-century ideas on the scale of the Milky Way, especially the work of Shapley. The final section describes how Hubble's discovery of distances to galaxies was first announced.
H0: THE INCREDIBLE SHRINKING CONSTANT, 1925-1975Trimble, Virginia
doi: 10.1086/133837pmid: N/A
The story of the Hubble constant logically begins just wehere the Curtis-Shapley debate on the distance scale of the universe ended, with Hubble's discovery of Cepheid variables in several nebulae that we now recognize as galaxies within the Local Group, which settled the issue of the existence of external galaxies. Hubble's own values of H was in the range of 500-550 km/sec/Mpc. The "best buy" value shrank in several large steps beginning in 1952, each being predicated on the recognition of some fundamental mistake in the previous distance scale calibrations. But it shrank more for some workers than for others, and by 1973 there was a clear polarization between a "long" recognition that general relativity permits, indeed nearly requires, an expanding universe; the gradual elimination of alternative explanations of redshift-distance relations; and the repelling of a late assault in the form of steady state cosmology, within whose framework H0 is a well-defined, never-varying number of only moderate importance.
THE EXTRAGALACTIC DISTANCE SCALEvan den Bergh, Sidney
doi: 10.1086/133839pmid: N/A
Cepheid variables are used to derive a Virgo cluster distance of 16.0 ± 1.5 Mpc. In conjunction with the mean Coma radial velocity and the well-established Coma/Virgo distance ratio, this yields a Hubble parameter H0 = 81 ± 8 km s-1 Mpc-1. By combining this value with an age of the Universe >~ 16.8 ± 2.1 Gyr, that is derived from the metal-poor globular cluster M92, one obtains f (Omega, Lambda) >~ 1.39 ± 0.22. This value is only marginally consistent with an Einstein-de Sitter universe with Omega = 0 and Lambda = 0, which has f =1. An Einstein-de Sitter universe with Omega = 1 and Lambda = 0, for which f = 2/3, appears to be excluded at the 3-sigma level. It is shown that some recent small values of H0 may have resulted from the large intrinsic dispersion in the linear diameters of galaxies, and from the fact that well-observed supernovae of Type Ia exhibit a luminosity range of ~20 at maximum light. A representative sample of recent estimates of H0 is given in Table 1. The median value of the Hubble parameter from the data in this table is H0 = 72 km s-1 Mpc -1 from which f(Omega,Lambda) >~ 1.24.
STARS CLASSIFIED AS CONSTANT IN THE GENERAL CATALOGUE OF VARIABLE STARS, IISchmidt, Edward G.
doi: 10.1086/133842pmid: N/A
Photometric observations have been made of 36 stars classified as CST or CST: in the General Catalogue of Variable Stars. Six of these stars are found to vary and three others were deemed possible variables. Of the certain variables, two (MR Her and TY Sge) are red pulsators, one (V1585 Cyg) is a rapid irregular variable, one is apparently a short period Cepheid-strip star (V432 Oph), one is an eclipsing binary (AQ Boo) and one is uncertain type (V351 Cyg). The stars we have observed as MR Her and TY Sge are the same ones which were identified on finding charts in the discovery papers suggesting that these stars have intervals of variability and intervals of quiescence. V432 Oph is of special interest because our photometry indicates that it may be either a double mode Cepheid or a peculiar long period RR Lyrae star depending on which of a couple of possible periods turns out to be correct.
A NEAR-INFRARED SURVEY OF OLD NOVAE--II. CK VULPECULAE AND V605 AQUILAEHarrison, Thomas E.
doi: 10.1086/133843pmid: N/A
We present near-infrared photometry of two objects that have been classified as clasical novae: CK Vulpeculae and V605 Aquilae. We were surprised to find that CK Vul was a moderately bright near-infrared source (mK = 14.13). Infrared images conclusively show that the near-infrared source is positionally coincident with the optical candidate for CK Vul. We are able to model the near-infrared + IRAS spectral energy distributions of both objects with a two-component model composed of a heavily extinguished central source, and a cooler blackbody source consistent with a cool dust shell. The combination of the model results and the outburst parameters suggest that these two objects might be of a similar nature. If we are to make this association, however, the central source luminosity of CK Vul object must have declined dramatically since the eruption in 1670. Because of its brightness, near-infrared spectroscopy of the CK Vul counterpart should be easily achievable with current instrumentation. Such observations are needed to determine the true nature of this source.
SPECTRA OF FOUR IRAS-SELECTED AGN CANDIDATESAguero, E. L.; Paolantonio, S.; Suarez, F.
doi: 10.1086/133844pmid: N/A
Observations of four southern warm IRAS objects are presented. From their optical spectral characteristics they are classified according to their principal excitation mechanisms: one as a Seyfert 2 type, two others as H II region-like galaxies (one of them is a starburst galaxy); the proposed optical identification for the remaining IRAS object is a star of early K type. Their heliocentric radial velocities are given. Additional observations of other eight IRAS galaxies are also reported, basically confirming previous results with slight variations in redshifts and classifications.