Engineering topics
Publications and source records attributed to Hoessel, J. G..
This is one of the galaxies being observed as part of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale which aims to determine the Hubble Constant to 10% accuracy.
WFPC2/HST images of Saturn's far-ultraviolet aurora reveal emissions confined to a narrow band of latitudes near Saturn's north and south poles. The aurorae are most prominent in the morning sector with patterns that appear fixed in local time.
Short exposure Planetary Camera images of T Tauri have been obtained using broadband filters spanning the wavelength range 0.55-0.80 mu. The optically visible star lies very close to an arc of reflection nebulosity.
The distance to NGC 4725 has been derived from Cepheid variables, as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale.
We report on the identification of 255 candidate variable stars in a field located some 1.7 from the center of the late-type spiral galaxy M101 = NGC 5457, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope.
Using the Hubble Space Telescope (HST) thirty-seven long-period Cepheid variables have been discoverd in the Fornax Cluster spiral galaxy NGC 1365.
We report the Discovery of Cepheid variable stars in the galaxy NGC 4414, as part of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale. Observations were obtained with the HST Wide Field and Planetary Camera 2 (WFPC2) for 13 epochs at V (F555W) and 4 at I (F814W).
The determination of an accurate value of the Hubble constant requires the measurement of accurate galaxy distances and velocities. Both the Virgo and Fornax clusters of galaxies are close enough to be studied in considerable detail.
We report the detection of Cepheids and a new distance to the spiral galaxy NGC 2541, based on data obtained with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST).
We report the discovery of Cepheid variable stars in the galaxy NGC 4414, as part of the Hubble Space Telescope (HST) key project on the Extragalactic Distance Scale.
We report on the discovery of Cepheids in the field spiral galaxy NGC3621, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST). NGC 3621 is one of 18 galaxies observed as part of the HST Key Project on the Extragalctic Distance Scale, which aims to measure the Hubble Constant to 10 percent accuracy.
We report on the discovery and properties of Cepheid variable stars in the barred spiral galaxy NGC 3351 which is a member of the LeoI group of galaxies.
HL Tauri is considered a prototype solar-mass T Tauri star. Planetary camera images of HL Tauri have been obtained through V, R, and I band filters using the Wide Field Planetary Camera 2 aboard the refurbished Hubble Space Telescope. These images show that HL Tauri is entirely reflection nebulosity at optical wavelengths, with no optical star visible to a limiting magnitude of V=25.5.
Accurate distances to galaxies are critical to determining the present expansion rate of the Universe or Hubble Constant (H(sub 0)). An important step in resolving the current uncertainty in H(sub 0) is the measurement of the distance to the Virgo cluster of galaxies. New observations using the Hubble Space Telescope yield a distance of 17.1 +/- 1.8 Mpc to the Virgo cluster galaxy M100. This distance leads to a value of H(sub 0) = 17 km/sec/Mpc. A comparable value of H(sub 0) is also derived from the Coma cluster using independent estimates of its distance ratio relative to the Virgo cluster.
As part of both the Early Release Observations fromthe Hubble Space Telescope and the Key PRoject on the Extragalctic Distance Scale, we have obtained multi-wavelength BVR WFPC2 images for the face-on Virgo cluster spiral galaxy M11 = NGC 4321.
Observations obtained over a period of five years of the resolved stars in the Pegasus dwarf irregular galaxy (DDO 216) have been searched for variable stars. Thirty-one variables were found, and periods established for 12. Two of these variable stars are clearly eclipsing variables, seven are very likely Cepheid variables, and the remaining three are probable Cepheids. The period-luminosity relation for the Cepheids indicates a distance modulus for Pegasus of m - M = 26.22 + or - 0.20. This places Pegasus very near the zero-velocity surface of the Local Group.
During their search for faint planetary nebulae on the Palomar Sky Survey, Ellis, Grayson, and Bond (1984) found three low-surface-brightness objects which they speculated were dwarf galaxies. Deep CCD observations of these objects indicate that one, EGB 04 27+63 is a previously uncataloged dwarf irregular galaxy which is partially resolved into stars. The other two objects appear to be faint diffuse nebulae: perhaps gaseous or reflection nebulae.
An analysis of repeated deep CCD observations of a field in the Local Group dwarf elliptical galaxy NBC 147 has resulted in the detection of 34 variable stars. The periods and shapes of light curves obtained for 13 of these variables show nine of them to be RR Lyrae stars. An intensity-averaged phase-weighted-mean g magnitude of 25.15 (+ 0.17 or - 0.15) is found which indicates a distance modulus to NGC 147 of 23.85 (+ 0.22 or - 0.20), or 589 kpc.