Picture of the Week

24 July 2017: Approximately 95 million light-years away, in the southern constellation of Octans (The Octant), lies NGC 7098 — an intriguing spiral galaxy with numerous sets of double features. The first of NGC 7098’s double features is a duo of distinct ring-like structures that loop around the galaxy’s hazy heart. These are NGC 7098’s spiral arms, which have wound themselves around the galaxy’s luminous core. This central region hosts a second double feature: a double bar. NGC 7098 has also developed features known as ansae, visible as small, bright streaks at each end of the central region. Ansae are visible areas of overdensity — they commonly take looping, linear, or circular shapes, and can be found at the extremities of planetary ring systems, in nebulous clouds, and, as is the case with NGC 7098, in parts of galaxies that are packed to the brim with stars. This image is formed from data ...

17 July 2017: The objects that astronomers call brown dwarfs sit somewhere between the definition of a planet and a star. They are balls of gas with more mass than a planet, but not enough mass to sustain stable hydrogen fusion like a star. Because they hardly emit any visible light, they were only first discovered in 1995 and up until today the majority of known brown dwarfs are within 1500 light-years of us. Now, astronomers using the NACO adaptive optics infrared camera on ESO’s Very Large Telescope have observed the star cluster RCW 38 in the constellation Vela (the Sail), about 5500 light-years away. This Picture of the Week shows the central part of RCW 38; the inserts on the sides show a subset of the brown dwarf candidates detected within the cluster. The scientists found half as many brown dwarfs as stars in the cluster. From these results and from studying ...

10 July 2017: In this scene, one of the most recognisable constellations in the night sky — Orion (The Hunter), with his famous belt and sword — rises over the slumbering Swedish-ESO Submillimetre Telescope (SEST) at ESO’s La Silla Observatory in Chile. This mythical collection of stars sits on the celestial equator, making it visible in both hemispheres. Within Orion itself, the distinctive blue and pink hues of the Orion Nebula are visible just above the stellar trio comprising Orion’s Belt. Hundreds of new stars are being forged in the depths of this stellar nursery. Telescopes have observed numerous stars wrapped in cocoons of gas and dust — shrouds that will transform into protoplanetary discs as the turbulent youngsters mature. This image also captures the noticeably reddish colours of Betelgeuse and Aldebaran — giant stars that belong to the constellations of Orion and Taurus (The Bull) respectively. These stars can be seen to ...

3 July 2017: This picture was taken at the northern tip of the Salar de Atacama — the largest salt flat in Chile. The flat is close to the town of San Pedro de Atacama, a town in northern Chile very popular among Chilean tourists and international visitors. The salt flat is home to two similar freshwater lagoons that lie very close together: the Ojos del Salar, which translates to “Eyes of the Salt Pan”. During the day, the site is visited by tourists, who stop by on their excursions from San Pedro de Atacama. Here, one of the two water-filled holes in the middle of the arid landscape is shown at dusk, when the site is again peaceful and quiet. The eye of water perfectly reflects the view of the sky as it changes from day to night. While the clouds on the right horizon are still been dipped in orange by ...

26 June 2017: This orange blob shows the nearby star Betelgeuse, as seen by the Atacama Large Millimeter/submillimeter Array (ALMA). This is the first time that ALMA has ever observed the surface of a star and this first attempt has resulted in the highest-resolution image of Betelgeuse available. Betelgeuse is one of the largest stars currently known — with a radius around 1400 times larger than the Sun’s in the millimeter continuum. About 600 light-years away in the constellation of Orion (The Hunter), the red supergiant burns brightly, causing it to have only a short life expectancy. The star is just about eight million years old, but is already on the verge of becoming a supernova. When that happens, the resulting explosion will be visible from Earth, even in broad daylight. The star has been observed in many other wavelengths, particularly in the visible, infrared, and ultraviolet. Using ESO’s Very Large Telescope astronomers ...

19 June 2017: The region between Mars and Jupiter is teeming with rocky worlds called asteroids. This asteroid belt is estimated to contain millions of small rocky bodies, and between 1.1 and 1.9 million larger ones spanning over one kilometre across. Small fragments of these bodies often fall to Earth as meteorites. Interestingly, 34% of all meteorites found on Earth are of one particular type: H-chondrites. These are thought to have originated from a common parent body — and one potential suspect is the asteroid 6 Hebe, shown here. Approximately 186 kilometres in diameter and named for the Greek goddess of youth, 6 Hebe was the sixth asteroid ever to be discovered. These images were taken during a study of the mini-world using the SPHERE instrument on ESO’s Very Large Telescope, which aimed to test the idea that 6 Hebe is the source of H-chondrites. Astronomers modelled the spin and 3D shape of ...

12 June 2017: This Picture of Week shows the Boomerang Nebula, a protoplanetary nebula, as seen by the Atacama Large Millimeter/submillimeter Array (ALMA). The background purple structure, as seen in visible light with the NASA/ESA Hubble Space Telescope, shows a classic double-lobe shape with a very narrow central region. ALMA’s ability to see the cold molecular gas reveals the nebula’s more elongated shape, in orange. Since 2003 the nebula, located about 5000 light-years from Earth, has held the record for the coldest known object in the Universe. The nebula is thought to have formed from the envelope of a star in its later stages of life which engulfed a smaller, binary companion. It is possible that this is the cause of the ultra-cold outflows, which are illuminated by the light of the central, dying star. ALMA looked at the nebula’s central dusty disc and the outflows further out, which span a distance of ...

5 June 2017: Astronomers using the ESO observatories might be a common sight in the Chilean Atacama Desert these days, but they were by no means the first people to call the area home. Although the desert is now dry and inhospitable, it once experienced more abundant rainfall and possessed a far more diverse flora. It has hosted various human civilisations, from the El Molle culture of 700–800 CE through to the Las Ánimas (800–1200 CE) and Diaguita (1200 CE to mid-15th century) peoples. Following the 15th-century Peruvian Inca conquests, the local culture became a mix of Inca and Diaguita. This lasted until the onset of the Spanish conquest in the 1530s, which put an end to an indigenously inhabited Atacama. Signs of this past can be found throughout the area surrounding ESO’s La Silla Observatory. Numerous rocks boasting thousand-year-old carvings — petroglyphs — can be found scattered throughout the region, thought to ...

29 May 2017: Like sentries guarding the heart of our home galaxy, the ESO 3.6-metre telescope and the Coudé Auxiliary Telescope stand tall in this stunning ultra high definition photograph from the La Silla Observatory, situated in the southern outskirts of the Chilean Atacama Desert. Since its inauguration in 1976, the ESO 3.6-metre telescope has undergone various upgrades, including the installation of a new secondary mirror that has allowed the telescope to remain as efficient and productive as ever. Since 2008, the telescope has housed the HARPS spectrograph, the most precise exoplanet hunter in the world. HARPS, the High Accuracy Radial velocity Planet Searcher, is the most successful finder of low-mass exoplanets to date. The now-decommissioned 1.4-metre Coudé Auxiliary Telescope (CAT) is housed in the smaller dome to the right of the 3.6-metre telescope. When active, the telescope fed the 3.6-metre’s Coudé Echelle Spectrometer through a light tunnel, which can be seen connecting ...

22 May 2017: Fomalhaut is one of the brightest stars in the sky. At roughly 25 light-years away the star lies especially close to us, and can be seen shining brightly in the constellation of Piscis Austrinus (The Southern Fish). This image from the Atacama Large Millimeter/submillimeter Array (ALMA) shows Fomalhaut (centre) encircled by a ring of dusty debris — this is the first time this scene has been captured at such high resolution and sensitivity at millimetre wavelengths. Fomalhaut’s disc comprises a mix of cosmic dust and gas from comets in the Fomalhaut system (exocomets), released as the exocomets graze past and smash into one another. This turbulent environment resembles an early period in our own Solar System known as the Late Heavy Bombardment, which occurred approximately four billions years ago. This era saw huge numbers of rocky objects hurtle into the inner Solar System and collide with the young terrestrial planets, ...

15 May 2017: This intriguing image may look like a collection of coloured blobs, but it is actually a high-resolution snapshot of a newborn star enshrouded in dust. Just 1300 light-years away in the Orion Nebula, the star, named HH 212, is remarkably young. The average lifespan of such a low-mass star is around 100 billion years, but this star is only 40 000 years old — truly an infant in stellar terms. In the cores of the vast molecular clouds in star formation regions, an ongoing battle rages; gravity versus the pressure of gas and dust. If gravity wins, it forces the gas and dust to collapse into a hot dense core that eventually ignites — forming a protostar. All the leftover gas and dust form a spinning disc around this baby star, and in many star systems they eventually coalesce to make planets. Such very young protostellar discs have been hard ...

8 May 2017: Sitting amongst the alien landscape of the harsh Atacama, the antennas of the Large Millimeter/submillimeter Array (ALMA) look eerily otherworldly in this ESO Picture of the Week as they are bathed in a neon green light. This light is actually an in-built function of ALMA, not evidence of alien activity! The array’s antennas have a flashing green light that blinks periodically whilst the antennas are in operation, and does not disturb the radio-wavelength observations. This light is not usually quite so visible — this picture was captured using a 10-second exposure, during which time a green flash occurred and spread throughout the image, creating a stark contrast between the neon green of the antennas and the deep blue of the night sky. Jagged ice formations known as penitentes can be seen in the foreground. These form at high altitudes where the low pressure and cold temperatures cause an unusual freezing ...

1 May 2017: Many ESO Pictures of the Week feature distant cosmic objects — mysterious jumbles of stars, gas, dust and more sitting millions of light-years away. This panorama, however, showcases a somewhat more tangible, but no less glorious, beauty — that of our home planet, Earth. Captured as the Sun slips below a false horizon of cloud, the sky glows in such a vivid shade of orange that the desert landscape takes on an almost alien appearance. In fact, the Chilean Atacama desert has been used previously by film crews seeking a Mars-like landscape! This other-worldly look is due to the exceptionally arid climate and the site’s complete isolation. The lack of humidity, rain and light pollution together produce both a dusty, rocky landscape and some of the most spectacularly clear skies found anywhere on Earth. This image was taken by ESO’s Simon Lowery in 2016 from Cerro Armazones, the future home ...

24 April 2017: In this incredible panorama, the night sky above ESO’s Very Large Telescope (VLT) displays our cosmic neighbourhood in all its glory. The VLT is located 2635 metres above sea level at ESO’s Paranal Observatory in northern Chile. This image illustrates the importance, and the benefits, of placing astronomical telescopes in such remote places! Anyone making the long journey to the site — including ESO Photo Ambassador Petr Horálek, who captured this scene — is rewarded with a truly spectacular view. On the right, behind the line of four 8.2-metre Unit Telescopes that together make up the VLT, the faint red and green hues of airglow can be seen illuminating the sky above the horizon. In addition zodiacal light is illuminating the sky as well. This diffuse light is caused by microscopic particles of light-scattering space dust in the plane of the Solar System. While these features are beautiful, the most ...

17 April 2017: So big it could engulf several Earths, Jupiter’s Great Red Spot is a gigantic storm that has been raging for centuries with winds blasting at over 600 kilometres per hour. But it has a rival: astronomers have discovered that Jupiter has a second Great Spot, this time a cold one. In the polar regions of the planet, astronomers using the CRIRES instrument on ESO's Very Large Telescope, along with other facilities, have found a dark spot in the upper atmosphere (below the aurora to the left) about 200 °C cooler than its surroundings. Aptly nicknamed the “Great Cold Spot”, this intriguing feature is comparable in size to the Great Red Spot — 24 000 km across and 12 000 km tall. But data taken over 15 years show that the Great Cold Spot is much more volatile than its slowly-changing cousin. It changes dramatically in shape and size over days ...

10 April 2017: The skies above ESO’s Paranal Observatory resemble oil on water in this ESO Picture of the Week, as greens, yellows, and blues blend to create an iridescent skyscape. The rocky, barren landscape below evokes an image of an alien world, perfectly complementing the shimmering cosmic display occurring above. The main feature is our beautiful home galaxy, the Milky Way, arching across the Chilean night sky and framing the awestruck observer on the left. The light from billions of stars combines to create the Milky Way’s glow, with huge clouds of dark dust blocking the light here and there and creating the dark and mottled pattern we observe. A natural effect known as airglow is responsible for the swathes of green and orange light that appear to be emanating from the horizon. ESO’s Very Large Telescope can be seen as a speck in the distant background to the right atop Cerro ...

3 April 2017: This image depicts the dusty disc encircling the young, isolated star HD 169142. The Atacama Large Millimeter/submillimeter Array (ALMA) imaged this disc in high resolution by picking up faint signals from its constituent millimetre-sized dust grains. The vivid rings are thick bands of dust, separated by deep gaps. Optimised to study the cold gas and dust of systems like HD 169142, ALMA’s sharp eyes have revealed the structure of many infant solar systems with similar cavities and gaps. A variety of theories have been proposed to explain them — such as turbulence caused by magnetorotational instability, or the fusing of dust grains — but the most plausible explanation is that these pronounced gaps were carved out by giant protoplanets. When solar systems form gas and dust coalesce into planets. These planets then effectively spring clean their orbits, clearing them of gas and dust and herding the remaining material into well-defined ...

27 March 2017: ESO's Very Large Telescope (VLT) looks more like a very small telescope in this image! From this perspective, it is difficult to make out the silhouettes of the VLT’s four 8.2-metre Unit Telescopes, which sit atop Cerro Paranal in the Chilean Atacama Desert. The VLT’s location was very carefully selected. It is vital for the site to be as dry as possible, as water vapour can absorb infrared light and degrade observations. In order to reduce the effects of Earth’s atmosphere as far as possible, the VLT is at 2600 metres above sea level, minimising the amount of atmosphere sitting between it and the stars. Due to its remote location, Paranal manages to be mostly undisturbed and light-free. Even the winding roads that lead through the Atacama Desert to the observation site are dimly lit to avoid unnecessary light pollution. In this image, a trail of stars cuts across the ...

20 March 2017: This image, taken by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, shows glowing dust inside the protocluster NGC 6334I. Studying this star-forming cloud in the Cat’s Paw Nebula (NGC 6334) with both ALMA and the Submillimeter Array (SMA) in Hawaii astronomers could see that something dramatic had taken place, completely changing a stellar nursery over a surprisingly short period of time. It is known that young stars form inside protoclusters when pockets of gas become so dense that they begin to collapse under their own gravity. Over time, discs of dust and gas form around these nascent stars and funnel material onto their surfaces helping them grow. However, this new image from ALMA shows a massive protostar, nestled deep within this dust-filled stellar nursery, that is undergoing an intense growth spurt, most likely triggered by an avalanche of gas falling onto its surface. This new material feeding it is ...

13 March 2017: With their spectacular glowing arms, grand spiral galaxies seem to get all the attention — but NGC 6822, a barred irregular dwarf galaxy, proves that regular spirals do not have a monopoly on galactic beauty. Also called Barnard’s galaxy, NGC 6822 is located in the constellation of Sagittarius just 1.6 million light-years away and is brimming with rich star formation regions. This new image is a composite of older observations made with the Wide Field Imager attached to the 2.2-metre MPG/ESO telescope at ESO’s La Silla Observatory and new data collected by the Atacama Large Millimeter/submillimeter Array (ALMA). The areas observed with ALMA are highlighted in the image and can be seen here in detail. The observations by ALMA reveal the structure of star-forming gas clouds in unprecedented resolution. Observations in our own galaxy have shown that stars form in the dense cores of giant clouds of molecular hydrogen gas, ...