Published in Nature Astronomy, a team of international astronomers has discovered the highest total mass double white dwarf binary to date, located a mere 160 light years away from the Sun. Coming in at approximately 1.56 solar masses, the source is the first double white dwarf destined to undergo unstable mass transfer and explode as a type Ia supernova.

A study published today in Nature Astronomy, in which a researcher from the IAC has participated, outlines the discovery of an extremely rare type of binary system composed of two high mass white dwarfs. The two stars are so close together that they will eventually collide resulting in a supernova explosion which, due to its proximity to the Earth, will appear ten times brighter than the Moon.

University of Warwick astronomers have discovered an extremely rare, high mass, compact binary star system only ~150 light years away. These two stars are on a collision course to explode as a type 1a supernova, appearing 10 times brighter than the moon in the night sky.

A team of international astronomers, led by researchers at the Instituto de Astrofisica de Canarias, has discovered a surprising high lithium abundance in the atmosphere of the companion star of the millisecond binary pulsar PSR J1023+0038.

A team of researchers from the Instituto de Astrofisica de Canarias (IAC), the University of Manchester and the Norwegian University of Science and Technology have detected an anomalously high lithium abundance in the atmosphere of the companion star of a binary millisecond pulsar. The lithium abundance is higher compared to stars with the same effective temperature and high-metallicity stars and so the study provides unambiguous evidence for fresh lithium production.

At least one out of four white dwarfs (WDs) will end its life as a magnetic star, and therefore magnetic fields are an essential component of WD physics. New insights into the magnetism of degenerate stars from a recent analysis of a volume-limited sample of WDs have provided the best evidence obtained so far of how the frequency of magnetism in WDs correlates with age. This could help to explain the origin and evolution of magnetic fields in WDs.

A blazar is a particular type of active galactic nucleus (AGN) with a central supermassive black hole which emits a jet, a flux of highly energetic particles and radiation moving almost at the velocity of light, and which is aligned along the observers line-of-sight. An international team of researchers has observed the birth of one of these objects for the first time by combining observations from several telescopes, among them the William Herschel Telescope (WHT).

A massive white dwarf star with a bizarre carbon-rich atmosphere could be two white dwarfs merged together, and which only narrowly avoided destruction, according to an international team led by University of Warwick (UK) astronomers, who observed the star with the William Herschel Telescope.

An international team of astronomers have made a historic discovery using the William Herschel Telescope (WHT), detecting gas molecules in a comet which has tumbled into our Solar System from another star. It is the first time that astronomers have been able to detect this type of material in an interstellar object.

Magnetic fields are present in a large variety of stars across the Hertszprung-Russell diagram, during all evolutionary stages from pre-main sequence stars, to main sequence stars and evolved stars, up to the final stages when the star explodes as a supernova. Magnetic fields play important roles in stellar evolution. Even a fairly weak magnetic field can suppress convection in stellar atmospheres and affect cooling times of extremely old white dwarfs. While the effects of the magnetic fields are well observed and sometime even understood, the origin of stellar magnetic fields is often unknown, and we do not know how fields evolve as stars evolve.

An international team of astronomers led by Marie Karjalainen (Isaac Newton Group of Telescopes, Spain), used electron-multiplying frame-transfer CCDs mounted on ISIS at the William Herschel Telescope to obtain time resolved spectroscopy of dust and gas from the extrasolar planetesimals orbiting WD 1145+017. The new results confirm previous findings showing the u-band excess and a decrease in line absorption during transits. Both can be explained by an opaque body blocking a fraction of the gas disc causing the absorption, implying that the absorbing gas is between the white dwarf and the transiting objects.

Following the principles of Lucky Imaging, a team of astronomers led by Jesus Maiz Apellaniz (Centro de Astrobiologia, Madrid) obtained Lucky Spectroscopy for five multiple massive-star systems on the nights of 2017 September 7 and 8. The spectra were obtained with the standard GOSSS-survey configuration using ISIS on the William Herschel Telescope, with some modifications (narrower slit and detector window, and tens of shorter exposures) to allow for lucky spatial separation of the individual component spectra. The spectra of delta Ori Aa+Ab and sigma Ori AaAb+B were successfully separated.

The large number of detected exoplanets around evolved stars sharply contrasts with the lack of detections of forming planets in protoplanetary disks around young stars, mainly because of the observational difficulties. Earlier this year, an international team of astronomers led by Ignacio Mendigutia (Centro de Astrobiologia, Spain), decided to use the ISIS spectrograph on the WHT to study the nature of the exoplanet LkCa15 b, by means of a technique called spectro-astrometry. This allowed them to derive not only the intensity spectrum around the H-alpha emission, but also the so called photocentre spectrum and the full width half maximum (FWHM) spectrum.

The Pristine Survey allows astronomers to look for and research the oldest stars in our universe, with the goal of learning more about the young universe right after the Big Bang. Recently, the survey team reported on the discovery of a particularly metal-poor star, Pristine 221.8781+9.7844, in the journal Monthly Notices of the Royal Astronomical Society.

A team of astronomers from SRON, Radboud University and the University of Cambridge have found out that by tweaking the existing automated system, Gaia can be used to detect hundreds of peculiar transients in the centres of galaxies. They found about 480 transients over a period of about a year. Their new method will be implemented in the system as soon as possible allowing astronomers to determine the nature of these events.

Researchers from the Universitat Politecnica de Catalunya (UPC) and the Instituto de Astrofisica de Canarias (IAC) report the discovery of one of the most massive known neutron stars using the William Herschel (WHT), the Gran Telescopio Canarias (GTC) and the IAC80 telescopes.

HS2231+2441, an HW Vir type, is a binary system composed of a low-mass white dwarf, with only 0.2-0.3 of a solar mass, with an effective temperature of 28,500 K, and a brown dwarf with 36-46 Jupiter masses. The binary system has an orbital period of approximately 3 hours. HS2231+2441 is the least massive HW Vir system known.

Highly obscured and rapidly growing supermassive black holes (SMBH), known as active galactic nuclei (AGN), might represent the key phase when SMBH accreted most of their mass and when the relationship between galaxies and their central SMBHs was established. A new study by an international team of astronomers led by Dr Silvia Mateos from the Instituto de Fisica de Cantabria (CSIC-UC) in Spain, now suggests that many of the brightest SMBH may be escaping our detection as they hide in heavily obscured environments.

Based on spectroscopic observations taken with the William Herschel Telescope (WHT) in 2015, astronomers from the Department of Physics and Astronomy at University of Sheffield have found the first evidence for a stellar tidal disruption event (TDE) in a galaxy with a massive on-going starburst.

Astronomers have discovered a new type of exotic binary star. In the system AR Scorpii a rapidly spinning white dwarf star powers electrons up to almost the speed of light. These high energy particles release blasts of radiation that lash the companion red dwarf star, and cause the entire system to pulse dramatically every 1.97 minutes with radiation ranging from the ultraviolet to radio. The research is published in the journal Nature on 28 July 2016.

A team of astronomers reports the discovery of one of the very weakest magnetic fields ever securely detected in a white dwarf. The observation was made using the ISIS spectropolarimeter on the William Herschel Telescope (WHT), in just one hour of exposure time and using the red and the blue arms of the spectrograph. This is part of a large survey of bright white dwarfs to search for such weak magnetic fields.

The European Space Agencys Rosetta mission is currently exploring comet 67P/Churyumov-Gerasimenko. The Rosetta mission is a hugely ambitious endeavour - the first spacecraft to orbit a comet and follow it on its journey towards the Sun, accompanied by its lander, Philae, which made the first ever landing on a comet in November 2014. Observatories across the planet are supporting this mission, and the ING is playing an important part in this - especially in providing unique observations this year as the comet passed its closest point to the Sun and highest level of activity.

Water delivery via asteroids or comets is likely taking place in many other planetary systems, just as it happened on Earth, according to new evidence found that numerous planetary bodies, including asteroids and comets, contain large amounts of water.

Spectroscopic observations with the William Herschel Telescope of three planetary nebulae have shed new light on the abundance discrepancy problem. Astronomers from the Instituto de Astrofísica de Canarias have shown that the largest abundance discrepancies (as high as 300 in certain positions in the nebula) are reached in planetary nebulae that have a close binary central star.

Recent William Herschel Telescope observations have revealed a new view of the accretion process in V455 And, an intermediate polar with a very rapidly spinning white dwarf. This white dwarf, which is a star that is only as large as the Earth but about half as massive as the Sun, spins around its axis in just over one minute, and is the third fastest-spinning white dwarf known.

Astronomers at the Institute of Astronomy in Cambridge (UK) have reported the discovery of a cold veil of halo stars in the very outskirts of the Milky Way. They obtained the radial velocities of a sample of distant halo stars located from 80 to 150 kiloparsecs from the center of our Galaxy using the ISIS spectrograph on the William Herschel Telescope (WHT), among others. The two most distant stars in this sample are Carbon stars observed with WHT/ISIS, and to date, they are the most distant field Galactic halo stars with radial-velocity measurements.

Astronomers have identified a new type of supernova or exploding star which is ten times brighter than any other type of stellar explosion.

Conventional CCD detectors have two major disadvantages: they are slow to read out and they suffer from read noise. These problems combine to make high-speed spectroscopy of faint targets the most demanding of astronomical observations. It is possible to overcome these weaknesses by using electron-multiplying CCDs (EMCCDs). EMCCDs are conventional frame-transfer CCDs, but with an extended serial register containing high-voltage electrodes. The recently released ING technical note no. 132 summarises the research and the implementation of EMCCDs at ING

Astronomers at the Isaac Newton Group of Telescopes (ING) have recently used, for the first ever time, an electron-multiplying detector for astronomical spectroscopic observations, allowing a high-time resolution analysis of the orbital motion of a short orbital period cataclysmic variable.

Having less than 24 hours in which to act, astronomers using the William Herschel Telescope have been able to obtain the only spectrum of an asteroid which hit the Earth, establishing the first direct link between an asteroid and a meteorite.

A team of astronomers has reported the first evidence for the presence of naphthalene cation in a region of the interestellar medium. This identification adds support to the hypothesis that this type of molecules could play an important role in the formation of prebiotic molecules present in the protoplanetary material

A team of Spanish astronomers has identified a stellar companion near the deuterium-burning mass limit located at a very wide distance, or 670 astronomical units, from the brown dwarf UScoCTIO 108 in the very young Upper Scorpius association. Although other substellar pairs with similar mass ratio are known, the system UScoCTIO 108A and B is the widest identified so far and possibly has a lower gravitational bound energy than any other known low-mass binary.

Some individual objects from the Galaxy Zoo project have gained a lot of attention from the public; the most famous of these is the ghost-like Voorwerp (the Dutch word for object), which was discovered by Dutch schoolteacher Hanny van Arkle. Observations with the William Herschel, among others, led astronomers to the conclusion that this object consists of a cloud of highly ionized gas.

Astronomers from the Rochester Institute of Technology and from University of Hertfordshire have obtained the first observational evidence that outflows from active galactic nuclei originate as winds from rotating accretion disks surrounding a super-massive black hole. Such evidence came from observations of quasar PG 1700+518 made by ISIS spectrograph in spectropolarimetric mode on the William Herschel Telescope.

For the first time, astronomers have witnessed a double stellar explosion at exactly the same position on the sky suggesting the death of a massive star

Early in the morning of February the 6th, 2006 a GRB was detected by the Swift satellite.Within 15 minutes the NOT was pointed towards this burst by the Danish GRB follow-up group. Using ALFOSC a bright optical afterglow was discovered in the R band. Directly after the detection had been made, a low-resolution spectrum was acquired using the same instrument. The latter spectrum rapidly determined the redshift of GRB 060206 at z=4.048. Meanwhile, the WHT had been alerted through our collaboration of the NOT and WHT, involving GRB follow-up teams from the Netherlands, the United Kingdom and Denmark. Starting at just 1.6 hours after the burst a medium-resolution spectrum could be obtained using WHTs ISIS spectrograph. The combination of the NOT and WHT provides a unique window on this afterglow.

Visible and near-infrared spectroscopic observations carried out on August 1st 2005 by a group led by the ING-IAC astronomer Javier Licandro using the William Herschel Telescope (WHT) and the Telescopio Nazionale Galileo (TNG) simultaneously show that the recently discovered trans-neptunian object (TNO) 2005 FY₉ is very similar to Pluto. Results have been published in the journal Astronomy & Astrophysics (Licandro et al., 2006, A&A,445, 35L).

The destiny of planetary systems through the late evolution of their host stars is very uncertain. Recently a team of astronomers from the University of Warwick using both the William Herschel Telescope and the Isaac Newton Telescope found a metal-rich gas disk around a moderately hot and young white dwarf.

Gamma-ray bursts (GRBs) have proven to be excellent probes of the distant Universe. The high luminosities of GRB afterglows allow absorption line studies of the interstellar medium at high redshift to at least z=4.5. Deep observations of afterglow positions have detected host galaxies in almost all cases. Most hosts are compact, low-metallicity, actively star-forming galaxies and are found to have low intrinsic extinction. However, in a few cases, radio/submillimeter observations of hosts give a star-formation rate which is of order a few to ~100 larger than rates derived from optical estimators.