Starship Asterisk*

Credit: CTIO/NOIRLab/NSF/AURA/Babak Tafreshi

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This Image of the Week features Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF’s NOIRLab, although not in an orientation that you might easily recognize. Several of the telescopes at CTIO are wrapped around the edge of the image, while the Milky Way shines with spectacular clarity through the center of the image, looking like a reflection in a pool of water. In fact, this image’s seemingly gravity-bending distortion is due to a specialized camera lens used by the photographer, known as a fisheye lens. These lenses provide an extreme wide-angle view. With one, the photographer can capture an ultra-wide panoramic image that appears to wrap around a central point, as seen here.

Image Credit: ESO/M. Zamani

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The 3.6-metre telescope, located at the La Silla Observatory, is truly ESO’s golden oldie. Having achieved first light in 1976, it is one of the oldest ESO telescopes still in use, and it is continuously upgraded to match the latest technology. This Picture of the Week shows a fish-eye view of the dome where the telescope sits, as stars rotate above it around the Southern celestial pole.

ESO’s 3.6-metre telescope is located in the larger dome to the left of the above photograph and, today, astronomers use it to search for exoplanets. Since 2008, the telescope has been home to the High Accuracy Radial Velocity Planet Searcher instrument (HARPS) which was joined by the Near InfraRed Planet Searcher (NIRPS) in June this year. As the world’s foremost exoplanet specialists, HARPS, NIRPS and the 3.6-metre make a splendid team for making exciting new discoveries about distant worlds.

The smaller dome used to house the Coudé Auxiliary Telescope (CAT). One of the goals of CAT, which was decommissioned in 1998, was to determine ages of stars in the Milky Way, one of the trickier questions in stellar astronomy. Through the bridge, light from CAT could be fed to one of the instruments placed in the larger dome whenever the 3.6-m telescope was observing with a different instrument. That way both telescopes could work in tandem and benefit from the 3.6-metre telescope’s instruments.

Image Credit: ESA/Hubble & NASA, J. Rigby

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This intriguing observation from the NASA/ESA Hubble Space Telescope shows a gravitationally lensed galaxy with the long-winded identification SGAS J143845+145407. Gravitational lensing has resulted in a mirror image of the galaxy at the centre of this image, creating a captivating centrepiece.

Gravitational lensing occurs when a massive celestial body — such as a galaxy cluster — causes a sufficient curvature of spacetime for the path of light around it to be visibly bent, as if by a lens. Appropriately, the body causing the light to curve is called a gravitational lens, and the distorted background object is referred to as being "lensed". Gravitational lensing can result in multiple images of the original galaxy, as seen in this image, or in the background object appearing as a distorted arc or even a ring. Another important consequence of this lensing distortion is magnification, allowing astronomers to observe objects that would otherwise be too far away or too faint to be seen.

Hubble has a special flair for detecting lensed galaxies. The telescope's sensitivity and crystal-clear vision allow it to see faint and distant gravitational lenses that cannot be detected with ground-based telescopes because of the blurring effect of Earth's atmosphere. Hubble was the first telescope to resolve details within lensed images of galaxies, and is capable of imaging both their shape and internal structure.

This particular lensed galaxy is from a set of Hubble observations that take advantage of gravitational lensing to peer inside galaxies in the early Universe. The lensing reveals details of distant galaxies that would otherwise be unobtainable, and this allows astronomers to determine star formation in early galaxies. This in turn gives scientists a better insight into how the overall evolution of galaxies has unfolded.

Image Credit: Zdeněk Bardon (bardon.cz)/ESO

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Gazing up at the stars from the Chilean Atacama Desert is the newest addition to ESO’s La Silla Observatory: BlackGEM, an array of optical telescopes established to detect the sources of gravitational waves using visible light. While not present when this image was taken, a third dome has now been installed in the rightmost pillar.

In partnership with observatories such as EGO-Virgo and LIGO, BlackGEM will search for some of the most dramatic events in the universe, including the collision of black holes and neutron stars. These events cause ripples in spacetime known as gravitational waves that detectors such as Virgo and LIGO can identify. BlackGEM is then able to pinpoint their location by searching the sky for short-lived astronomical events such as optical sources that appear or disappear within a single night. After BlackGEM has finished its measurements, other telescopes such as ESO’s Very Large Telescope (VLT) can make deeper follow-up observations in more detail, providing astronomers with insight into some of the universe’s most closely guarded secrets.

Sparkling in the sky above BlackGEM is the Milky Way, bejewelled with stars and clouded with dark dust and bright gas. The haze of ruby red and emerald green which illuminates the scene is known as airglow and results mainly from chemical reactions between atoms high up in the atmosphere.

Image Credit: ESA/Hubble & NASA, W. Keel

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This luminescent image features multiple galaxies, perhaps most noticeably LEDA 58109, the lone galaxy in the upper right. LEDA 58109 is flanked by two further galactic objects to its lower left — an active galactic nucleus (AGN) called SDSS J162558.14+435746.4 that partially obscures the galaxy SDSS J162557.25+435743.5, which appears to poke out to the right behind the AGN.

Galaxy classification is sometimes presented as something of a dichotomy: spiral and elliptical. However, the diversity of galaxies in this image alone highlights the complex web of galaxy classifications that exist, including galaxies that house extremely luminous AGNs at their cores, and galaxies whose shapes defy the classification of either spiral or elliptical.

The sample of galaxies here also illustrates the wide variety of names that galaxies have: some relatively short, like LEDA 58109, and some very long and challenging to remember, such as the two galaxies to the left. This is due to the variety of cataloguing systems that chart the celestial objects in the night sky. No one catalogue is exhaustive, and they cover overlapping regions of the sky, so that many galaxies belong to several different catalogues. For example, the galaxy on the right is LEDA 58109 in the LEDA galaxy database, but is also known as MCG+07-34-030 in the MCG galaxy catalogue, and SDSS J162551.50+435747.5 in the SDSS galaxy catalogue — the same catalogue that also lists the two galaxies to the left.