Four compact ROSAT X-ray sources very close to the nearby ultraluminous infrared galaxy Arp 220 (IC 4553) have been identified as medium-redshift QSOs. The closest pair lying symmetrically across the galaxy have almost identical redshifts z = 1.25,...
We present 220 GHz (1.36 mm) measurements of zenith optical depth obtained to characterise the Indian Astronomical Observatory, Hanle (Ladakh, India) during the period from late December 1999 to early May 2000 and early October 2000 to September 20...
We have used a Very Long Baseline Interferometry (VLBI) array at 18cm wavelength to image the nucleus of the luminous IR galaxy Arp 220 at ~1 pc linear resolution, and with very high sensitivity. The resulting map has an rms of 5.5 microJy/beam, an...
We report the results of pointed observations of the prototypical ultra-luminous infrared galaxy (ULIRG) Arp 220 at 850 microns using the polarimeter on the SCUBA instrument on the James Clerk Maxwell Telescope. We find a Bayesian 99 per cent confi...
Generic astronomy calculator to calculate times for sunrise, sunset, moonrise, moonset for many cities, with daylight saving time and time zones taken in account.
Cosmic reionization is known to be a major phase transition of the gas in the Universe. Since astronomical objects formed in the early Universe, such as the first stars, galaxies and black holes, are expected to have caused cosmic reionization, the f...
POEMMA-Balloon with Radio (PBR) is a scaled-down version of the Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) design, optimized to be flown as a payload on one of NASA's sub-orbital super pressure balloons circling the Earth above the southe...
The HETG can be used to obtain spatially resolved spectra of moderately extended sources. We present preliminary results for two well studied, oxygen rich supernova remnants in the Magellanic clouds, E0102-72 and N132D. The dispersed spectrum of E0...
Stars are spherical balls of hot, ionized gas (plasma) held together by their own gravity. Stars are the most fundamental building blocks of our universe.
The first time simultaneous measurements of sodium column density and the absolute flux from a sodium laser guide star, created by a monochromatic 3 W cw laser, tuned to the peak of the sodium D2 hyperfine structure, were conducted at the MMT and C...
We present our study of the 2-D structures of the tidal tails associated with 20 galactic globular clusters, structures obtained by using the wavelet transform to detect weak structures at large scale and filter the strong background noise for the...
NGC 5850 is a prototype of double-barred galaxy (Friedli et al. 1996) classified as SBb(sr) I-II (Higdon et al. 1998; Prieto et al. 1997). This kind of system is primordial to understand the physical mechanism responsible for feeding galaxy nuclei...
NGC 5850 is a prototype of double-barred galaxy (Friedli et al. 1996) classified as SBb(sr) I-II (Higdon et al. 1998; Prieto et al. 1997). This kind of system is primordial to understand the physical mechanism responsible for feeding galaxy nuclei...
We have identified a ring-shaped emission-line nebula and a possible bipolar outflow centered on the B1.5 supergiant Sher #25 in the Galactic giant HII region NGC 3603 (distance 6 kpc). The clumpy ring around Sher #25 appears to be tilted by 64 deg...
We have performed a detailed study of the morphology and kinematics of the hourglass-shaped nebula around the blue supergiant Sher 25 in the galactic giant HII region NGC 3603. Near-infrared high resolution adaptive optics images in the Br gamma li...
In gamma-ray astronomy, gamma-ray bursts (GRBs) are extremely energetic events occurring in distant galaxies which represent the brightest and most powerful
We discuss the problem of the absorption of very high-energy gamma-rays by pair production interactions with extragalactic photons which originate from stellar emission in the near IR-UV and reradiation of starlight in the mid- and far-IR. The abso...
We discuss the ability of the GLAST Large Area Telescope (LAT) to identify, resolve, and study the high energy gamma-ray sky. Compared to previous instruments the telescope will have greatly improved sensitivity and ability to localize gamma-ray po...
A Python package for gamma-ray astronomy (⭐ 276)
The flux upper limits of the diffuse gamma rays, from the inner and outer Galactic planes, are revised by factors of 4.0$\sim$3.7 for mode energies 3$\sim$10 TeV, respectively, by using the simulation results of the effective area ratios for gamma-...
We obtained new upper limits on the diffuse gamma rays from the inner Galactic (IG) and outer Galactic (OG) planes in 3.10 TeV region, using the Tibet air shower data and new Monte Carlo simulation results. A difference of the effective area of the...
We searched for steady PeV gamma-ray emission from the Monogem ring region with the Tibet air shower array from 1997 February to 2004 October. No evidence for statistically significant gamma-ray signals was found in a region 111$\degr$ $\leq$ R.A....
We propose to build a large water-Cherenkov-type muon-detector array (Tibet MD array) around the 37,000 m$^{2}$ Tibet air shower array (Tibet AS array) already constructed at 4,300 m above sea level in Tibet, China. Each muon detector is a waterpro...
We present first results of astrophysically relevant experiments where highly supersonic plasma jets are generated via conically convergent flows. The convergent flows are created by electrodynamic acceleration of plasma in a conical array of fine...
The model first introduced by Raga & Canto (1996) in which astrophysical jets are deflected on passing through an isothermal high density region is generalised by taking into account gravitational effects on the motion of the jet as it crosses the...
There are at present ${\cal O}(100)$ gravitational-wave candidates from compact binary mergers reported in the astronomical literature. As detector sensitivities are improved, the catalog will swell in size: first to ${\cal O}(1000)$ events in the A+...
Mientras que los agujeros negros han sido detectados en el universo observable, los agujeros blancos son el resultado de cálculos de astrónomos y físicos. Aparecen resolviendo operaciones …
Edwin Powel Hubble is regarded as one of the most important astronomers of 20th century. In despite of his great contributions to the field of astronomy, he never received the Nobel Prize because astronomy was not considered as the field of the Nobel...
The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to observe the boron 2500 A region of BD-13 3442. At a metallicity of [Fe/H]=-3.00, this is the most metal-poor star ever observed for B. Nearly 26 ho...
Hypatia was a prominent philosopher, mathematician, and astronomer in ancient Alexandria, born around 370 CE. She was the daughter of Theon, an esteemed mathematician, who likely supervised …
Hypatia, philosopher, astronomer, and mathematician, teaches celestial mechanics, geometry, and the art of reasoning. She is the intellectual heir of Plato and Euclid, and students from across the Eastern …
Hypatia of Alexandria, late antique Neoplatonist philosopher, mathematician, and astronomer, famed teacher and martyr of learning in Roman Egypt.
"And in those days there appeared in Alexandria a female philosopher, a pagan named Hypatia, and she was devoted at all times to magic, astrolabes and instruments of music, and she beguiled many peopl...
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Feb 25, 2026 · Hypatia, mathematician, astronomer, and philosopher who lived in a very turbulent era in Alexandria’s history. She is the earliest female mathematician of whose life and work reasonably …
Hypatia (born c. 350–370 – March 415 AD) was a Neoplatonist philosopher, astronomer, and mathematician who lived in Alexandria, at that time in the province
Hypatia[a] (born c. 350–370 – March 415 AD) [1][4] was a Neoplatonist philosopher, astronomer, and mathematician who lived in Alexandria, at that time in the province of Egypt and a major city of the …
The lowest-mass stars, brown dwarfs and giant exoplanets span a minimum in the mass-radius relationship that probes the fundamental physics of extreme states of matter, magnetism, and fusion. This White Paper outlines scientific opportunities and the...
Aims: To investigate structure of the hot object in the symbiotic prototype Z And during its major 2000-03 active phase. Methods: Analysis of the far ultraviolet, optical low- and high-resolution spectroscopy and UBVR photometry. Reconstruction of...
David Adam Wilkinson, FRAS (born 16 May 1963) is a British Methodist minister, theologian, astrophysicist and academic. He was the Principal of St John's