Related papers: Harold Knox-Shaw and the Helwan Observatory
Through meticulous daily observation of the Sun's large-scale magnetic field the Wilcox Solar Observatory (WSO) has catalogued two magnetic (Hale) cycles of solar activity. Those two (~22-year long) Hale cycles have yielded four…
Detecting HI using redshifted Ly-alpha absorption lines is 1e6 times more sensitive than using the 21cm emission line. We review recent discoveries of HI Ly-alpha absorbers made with the Hubble Space Telescope (HST) which have allowed us a…
The Kilometer Square Array~(KM2A) of the Large High Altitude Air Shower Observatory (LHAASO) aims at surveying the northern gamma-ray sky at energies above 10 TeV with unprecedented sensitivity. Gamma-ray observations have long been one of…
How did galaxies form and evolve? This is one of the most challenging questions in astronomy to- day. Answering it requires a careful combination of observational and theoretical work to reliably determine the observed properties of cosmic…
This paper presents optical R-band light curves and the time delay of the doubly imaged gravitationally lensed quasar SDSS J1001+5027 at a redshift of 1.838. We have observed this target for more than six years, between March 2005 and July…
Based on spectroscopy and multiband wide-field observations of the gravitationally lensed quasar HE 0435-1223, we determine the probability distribution function of the external convergence $\kappa_\mathrm{ext}$ for this system. We measure…
We present newly acquired images of the near-infrared counterpart of 3CR radio sources. All the sources were selected to have a redshift of less than 0.3 to allow us to obtain the highest spatial resolution. The observations were carried…
A black shell consists of a massive thin spherical shell contracting toward its gravitational radius, coinciding with 't Hooft's brick wall, from the point of view of an external observer far from the shell. This object was conceived by…
In 1839 Ebenezer Porter Mason (1819-1840) produced detailed drawings of the Omega Nebula (M17), the Trifid Nebula (M20) and the eastern part of the Veil Nebula (NGC 6992 and 6995). He used a 12-inch (30 cm) reflector that he and his friends…
It has been over 24 years since the iconic Crab Nebula has been visited by the high spatial resolution eye of the Hubble Space Telescope. The expanding nebula is dynamic on these timescales, with many of the outer filaments of the nebula…
We present first results from five years of spectrophotometric monitoring of the bright double QSO and gravitational lens HE 1104-1805. The quasar has varied considerably over this time, while the emission line fluxes appear to have…
We present 3 years of photometry of the ``Double Hamburger'' lensed quasar, HE1104-1805, obtained on 102 separate nights using the OGLE 1.3-m telescope. Both the A and B images show variations, but with substantial differences in the…
This paper is dedicated to the memory of Paul Felenbok (1936-2020) who was astronomer at Paris-Meudon observatory, and founded in 1974, fifty years ago, a high altitude station (2930 m), above Saint V{\'e}ran village in the southern Alps…
We present long-baseline ALMA observations of the strong gravitational lens H-ATLAS J090740.0-004200 (SDP.9), which consists of an elliptical galaxy at $z_{\mathrm{L}}=0.6129$ lensing a background submillimeter galaxy into two extended…
We have combined two epochs of Hubble Space Telescope WFPC2 imaging data with ground-based expansion velocities to determine distances to three planetary nebulae (NGC 6578, NGC 6884, and IC 2448). We used two variants of the expansion…
By the 2040s--50s, facilities such as \emph{Gaia}, WEAVE, 4MOST, Rubin, \emph{Euclid}, \emph{Roman}, and the ESO ELT will have transformed our global view of the Milky Way. Yet key questions will remain incompletely resolved: a detailed…
We present the preliminary results of a deep (167 ks) ROSAT HRI observation of the cD galaxy NGC1399 in the Fornax cluster. We find, in agreement with previous observations, an extended (41 Kpc adopting a distance of 19 Mpc) gaseous halo…
We report on narrowband CN imaging of Comet 103P/Hartley 2 obtained at Lowell Observatory on 39 nights from 2010 July until 2011 January. We observed two features, one generally to the north and the other generally to the south. The CN…
The Habitable Worlds Observatory (HWO), NASA's next flagship science mission, follows in the tradition of the Nancy Grace Roman Space Telescope and other preceding great observatories. HWO will directly image and characterize Earth-like…
We present the first results from a program searching for extended Ly$\alpha$ halos around high redshift ($ z \gtrsim 6.5$) quasars using the red channel of the Keck Cosmic Web Imager (KCWI). Our observations reveal a Ly$\alpha$ halo…