ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and arguably the world’s most productive astronomical observatory. Its primary mission is to provide the most advanced research facilities to astronomers and astrophysicists, allowing them to conduct front-line science in the best conditions. In these pages, we showcase some of ESO’s spectacular space images, captured by a variety of telescopes.
Force of attraction
Using ESO’s Very Large Telescope (VLT), European astronomers have for the first time demonstrated that a magnetar – an unusual type of neutron star – was formed from a star with at least 40 times as much mass as the Sun. The result presents great challenges to current theories of how stars evolve, as a star as massive as this was expected to become a black hole, not a magnetar. This now raises a fundamental question: just how massive does a star really have to be to become a black hole?
To reach their conclusions, the astronomers looked in detail at the extraordinary star cluster Westerlund 1, located 16 000 light-years away in the southern constellation of Ara (the Altar). From previous studies, the astronomers knew that Westerlund 1 was the closest super star cluster known, containing hundreds of very massive stars, some shining with a brilliance of almost one million suns and some two thousand times the diameter of the Sun (as large as the orbit of Saturn).
these results: “If the Sun were located at the heart of this remarkable cluster, our night sky would be full of hundreds of stars as bright as the full Moon.” A magnetar is a type of neutron star with an incredibly strong magnetic field – a million billion times stronger than that of the Earth, which is formed when certain stars undergo supernova explosions.
This magnificent view of the region around the star R Coronae Australis was created from images taken with the Wide Field Imager (WFI) at ESO’s La Silla Observatory in Chile. R Coronae Australis lies at the heart of a nearby star-forming region and is surrounded by a delicate bluish reflection nebula embedded in a huge dust cloud. The image reveals surprising new details in this dramatic area of sky.
This image shows a section of sky that spans roughly the width of the full Moon. This is equivalent to about four lightyears at the distance of the nebula, which is located some 420 light-years away in the small constellation of Corona Australis (the Southern Crown). The intense radiation given off by these hot young stars interacts with the gas surrounding them and is either reflected or re-emitted at a different wavelength. These complex processes, determined by the physics of the interstellar medium and the properties of the stars, are responsible for the magnificent colours of nebulae.
Way back when…
A European team of astronomers using ESO’s Very Large Telescope (VLT) has measured the distance to the most remote galaxy so far. By carefully analysing the very faint glow of the galaxy, they have found that they are seeing it when the Universe was only about 600 million years old (a redshift of 8,6). These are the first confirmed observations of a galaxy whose light is clearing the opaque hydrogen fog that filled the cosmos at this early time.
Studying these first galaxies is extremely difficult. By the time their initially brilliant light gets to Earth, they appear very faint and small. Furthermore, this dim light falls mostly in the infrared part of the spectrum because its wavelength has been stretched by the expansion of the Universe – an effect known as redshift. To make matters worse, at this early time, less than a billion years after the Big Bang, the Universe was not fully transparent and much of it was filled with a hydrogen fog that absorbed the fierce ultraviolet light from young galaxies.
How to grow a galaxy
New observations from ESO’s Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang, the mass of a typical galaxy increased dramatically, and understanding why this happened is one of the hottest problems in modern astrophysics.
The first galaxies formed well before the Universe was one billion years old and were much smaller than the giant systems – including the Milky Way – that we see today. Somehow, the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems, and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed.
Says astronomy team leader Giovanni Cresci: “The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened, and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe.” The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written.
What goes around…
A spectacular new image of NGC 300, a spiral galaxy similar to the Milky Way, located in the nearby Sculptor Group of galaxies. Taken with the Wide Field Imager (WFI) at ESO’s La Silla Observatory in Chile, this 50-hour exposure reveals the structure of the galaxy in exquisite detail. NGC 300 lies about six million light-years away and appears to be about two thirds the size of the full Moon on the sky.
ESO astronomers recently discovered the most distant and one of the most massive stellar-mass black holes yet found in this galaxy, as the partner of a hot and luminous Wolf–Rayet star in a binary system. NGC 300 and another galaxy, NGC 55, are slowly spinning around and towards each other in the early stages of a lengthy merging process.
Astronomers have obtained the first image of a dusty disc closely encircling a massive baby star, providing direct evidence that massive stars form in the same way as their smaller brethren. The team looked at an object known by the cryptic name of IRAS 13481-6124. About 20 times the mass of our Sun and five times its radius, the young central star, which is still surrounded by its pre-natal cocoon, is located in the constellation of Centaurus, about 10 000 light-years away.
Circumstellar discs are an essential ingredient in the formation process of lowmass stars such as our Sun. However, it is not known whether such discs are also present during the formation of stars more massive than about 10 solar masses, where the strong light emitted might prevent mass falling on to the star. For instance, it has been proposed that massive stars might form when smaller stars merge.
A new infrared image from ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA) reveals an extraordinary landscape of glowing tendrils of gas, dark clouds and young stars within the constellation of Monoceros (the Unicorn). This star-forming region, known as Monoceros R2, is embedded within a huge dark cloud. The region is almost completely obscured by interstellar dust when viewed in visible light, but is spectacular in the infrared.
Although it appears close in the sky to the more familiar Orion Nebula, it is actually almost twice as far from Earth, at a distance of about 2 700 light-years. In visible light, a grouping of massive hot stars creates a beautiful collection of reflection nebulae where the bluish starlight is scattered from parts of the dark, foggy outer layers of the molecular cloud. However, most of the new-born massive stars remain hidden as the thick interstellar dust strongly absorbs their ultraviolet and visible light.
This striking infrared image from ESO’s Paranal Observatory in northern Chile penetrates the dark curtain of cosmic dust and reveals in astonishing detail the folds, loops and filaments sculpted from the dusty interstellar matter by intense particle winds and the radiation emitted by hot young stars.
Wallpaper: To download wallpaper images of some of ESO's spectacular images. [click here]
Video: To watch the associated videos; which zoom in on the various stars and regions. [click here]