Starship Asterisk*

Image Credit: CTIO/NOIRLab/NSF/AURA/C. Corco

---

A rainbow cloud creates a stunning curtain of colors just after sunrise in this image taken from Cerro Pachón in Chile, home of one half of the International Gemini Observatory, the SOAR Telescope, and Vera C. Rubin Observatory, all operated by NSF’s NOIRLab. The appearance of pastel pigmentation sweeping across the sky is possibly due to the phenomenon known as cloud iridescence. Similar to the swirling colors on the surface of a bubble or oil spill, this optical effect occurs when sunlight passes through a particularly thin cloud that is composed of water droplets or ice crystals of uniform size. As the Sun’s rays encounter individual crystals, the light is both diffracted and scattered, revealing a gradient of the component wavelengths, or colors, that make up the Sun’s light.

Because of the smooth, wavy shape of the clouds in this image, they closely resemble a different class of iridescent clouds called nacreous clouds, which are also produced by uniformly sized ice crystals diffracting sunlight. But unlike regular iridescent clouds that form in the troposphere and can be seen all over the world, nacreous clouds form at a higher elevation, in the stratosphere, and most often in frigid regions such as Antarctica, Alaska, and Scandinavia where the lower stratosphere cools below – 85° Celsius (–120° Fahrenheit).

Zdeněk Bardon/ESO

---

This Picture of the Week shows a long exposure image of the BlackGEM telescopes, located at ESO’s La Silla Observatory in Chile. The whitish star trails in the sky are an effect due to the Earth’s rotation on its axis around the southern celestial pole, which gives the impression of the stars’ movement over the course of several hours. To the right hand side of the central telescope the Milky Way is visible, seen here as a particularly bright region, densely packed with streaks of starlight. As these streaks move in circles across the night sky, the viewer gets a sense of tumbling around inside a giant washing machine, as they peer out at the scene through the fisheye lens.

BlackGEM, which recently started operating, is an array of three 0.65-metre optical telescopes, which can point at different regions of the sky, searching for some of the most dramatic events in the Universe like merging neutron stars and black holes. As these events unfold they send out ripples in spacetime, known as gravitational waves, which can be picked up by observatories like LIGO and Virgo. BlackGEM can then pinpoint the light sources from the afterglow of these events, allowing for more detailed follow-up observations of these cataclysmic collisions.

A spiral galaxy that is tilted partially toward us. Its inner disc is bright and colourful, with bluish and reddish spots of star formation throughout the arms. An outer disc of pale, dim dust surrounds it. It has many arms, which are being pulled away from the disc, down and to the right. They stretch into long, faint trails that cross the image. The background is dark and mostly empty, with three bright stars. ~ Image Credit: ESA/Hubble & NASA, M. Gullieuszik and the GASP team

---

The jellyfish galaxy JO206 trails across this image from the NASA/ESA Hubble Space Telescope, showcasing a colourful star-forming disc surrounded by a pale, luminous cloud of dust. A handful of bright stars with criss-cross diffraction spikes stand out against an inky black backdrop at the bottom of the image. JO206 lies over 700 million light-years from Earth in the constellation Aquarius, and this image of the galaxy is the sixth and final installment in a series of observations of jellyfish galaxies. Some of Hubble's other observations of these peculiar galaxies — which range from grandiose to ghostly — are available here.

Jellyfish galaxies are so-called because of their resemblance to their aquatic namesakes. In this image, the disc of JO206 is trailed by long tendrils of bright star formation that stretch towards the bottom right of this image, just as jellyfish trail tentacles behind them. The tendrils of jellyfish galaxies are formed by the interaction between galaxies and the intra-cluster medium, a tenuous superheated plasma that pervades galaxy clusters. As galaxies move through galaxy clusters they ram into the intracluster medium, which strips gas from the galaxies and draws it into the long tendrils of star formation.

The tentacles of jellyfish galaxies give astronomers a unique opportunity to study star formation under extreme conditions, far from the influence of the main disc of the galaxy. Surprisingly, Hubble revealed that there are no striking differences between star formation in the discs of jellyfish galaxies and star formation in their tentacles, which suggests the environment of newly-formed stars has only a minor influence on their formation.

• Astrophysical Journal 945(1):54 (2023 Mar 01) DOI: 10.3847/1538-4357/acb59b
• arXiv > astro-ph > arXiv:2301.08279 > 19 Jan 2023

• arXiv > astro-ph > arXiv:2302.10615 > 21 Feb 2023

A close-in image of a spiral galaxy, showing its core and part of a spiral arm. Thousands upon thousands of tiny stars that make it up can be seen, most dense in a whitish bar that forms its core. Clumps and filaments of dust form an almost skeletal structure that follows the twist of the galaxy and its spiral arm. Large, glowing bubbles of red gas are hidden in the dust. ~ Credit: ESA/Webb, NASA & CSA, J. Lee and the PHANGS-JWST Team

---

A delicate tracery of dust and bright star clusters threads across this image from the NASA/ESA/CSA James Webb Space Telescope. The bright tendrils of gas and stars belong to the barred spiral galaxy NGC 5068, whose bright central bar is visible in the upper left of this image. NGC 5068 lies around 17 million light-years from Earth in the constellation Virgo.

This portrait of NGC 5068 is part of a campaign to create an astronomical treasure trove, a repository of observations of star formation in nearby galaxies. Previous gems from this collection can be seen here and here. These observations are particularly valuable to astronomers for two reasons. The first is because star formation underpins so many fields in astronomy, from the physics of the tenuous plasma that lies between stars to the evolution of entire galaxies. By observing the formation of stars in nearby galaxies, astronomers hope to kick-start major scientific advances with some of the first available data from Webb. ...

This image is a composite of image data from two of Webb's instruments, MIRI and NIRCam.

Image Credit: KPNO/NOIRLab/NSF/AURA/T. Slovinský

---

The eighteen-story Nicholas U. Mayall 4-meter Telescope is located at Kitt Peak National Observatory (KPNO), a Program of NSF’s NOIRLab, and is seen here against the backdrop of two celestial landmarks of the northern hemisphere: The constellation Ursa Major (the Great Bear), with its seven bright stars that make the Big Dipper, on the right side of Mayall and the North Star Polaris on the left.

The stars of the Big Dipper asterism are notable even on their own. The second star in the Big Dipper’s handle is Mizar and together with its fainter companion star Alcor they are known as the Horse and Rider. Their pairing is a naked-eye double since they appear to observers to be right next to each other. Because of their close proximity, trying to resolve the pair with only the naked eye has been a traditional sight test in many countries. The stars Merak (blue) and Dubhe (white), that form the front of the Big Dipper’s cup, are often used for celestial navigation. By connecting the two with an imaginary line and extending it across the sky, the North Star Polaris can easily be located, seen here the brightest star to the far left of the Mayall telescope. Polaris’s stable position has made it useful for northern hemisphere navigation since the 5th century. ...

Credit: ESO

---

It might look like there’s not a lot going on in this Picture of the Week, but looks can be deceiving. Far off in the distance, huddled together like penguins in an Antarctic storm, sit the 66 high-precision antennas of the Atacama Large Millimeter/submillimeter Array (ALMA). Operated by ESO together with international partners, ALMA is designed to study the light emitted by the coldest objects in the Universe, such as vast cold clouds in interstellar space.

Stretching out either side of the antennas is the empty landscape of the Chajnantor plateau. Sitting at 5,000 m above sea level in the Chilean Andes, this remote location is one of the driest places on Earth. It’s this dryness that makes it the perfect place for observing the signals from the cold Universe which would otherwise be heavily absorbed by water vapour in our atmosphere.

ALMA is what’s known as an interferometer, meaning that its individual antennas work together, acting to form a more powerful telescope that can discern details smaller than what can be seen with the individual antennas. Depending on what observations are being carried out, the antennas are arranged in different configurations. The further away they are, the finer the details they can see; more compact configurations, on the other side, offer better sensitivity and are ideal when observing diffuse extended objects. Here the antennas are in one of the most compact configurations, but the distance between them can be as great as 16 kilometres!

A galaxy fills up most of the frame from the right. It is fuzzy and diffuse, but made up of numerous tiny stars. In the core, the stars merge into a glowing bar shape. The gas and stars in the galaxy vary between warm and cool colours. They are spread over a large area, the colours mixing like clouds. The glow of the galaxy fades into a black background, with a few stars and small, distant galaxies. (Credit: ESA/Hubble & NASA, C. Kilpatrick)

---

The galaxy NGC 7292 billows across this image from the NASA/ESA Hubble Space Telescope, accompanied by a handful of bright stars and the indistinct smudges of extremely distant galaxies in the background. It lies around 44 million light-years from Earth in the constellation Pegasus.

This slightly dishevelled galaxy is irregular, meaning that it lacks the distinct spiral arms of galaxies like the Whirlpool Galaxy or the smooth elliptical shape of galaxies like Messier 59. Unusually, its core is stretched out into a distinct bar, a feature seen in many spiral galaxies. Alongside its hazy shape, NGC 7292 is remarkably faint. As a result, astronomers classify NGC 7292 as a low surface brightness galaxy, barely distinguishable against the backdrop of the night sky. Such galaxies are typically dominated by gas and dark matter rather than stars.

Astronomers directed Hubble to inspect NGC 7292 during an observational campaign studying the aftermath of Type II supernovae. These colossal explosions happen when a massive star collapses and then violently rebounds in a catastrophic explosion that tears the star apart. Astronomers hope to learn more about the diversity of Type II supernovae they have observed by scrutinising the aftermath and remaining nearby stars of a large sample of historical Type II supernovae.

NGC 7292’s supernova was observed in 1964 and accordingly given the identifier SN 1964H. Studying the stellar neighbourhood of SN 1964H helps astronomers estimate the initial mass of the star that went supernova, and could uncover surviving stellar companions that once shared a system with the star that would become SN 1964H.

Credit: CTIO/NOIRLab/NSF/AURA/T. Slovinský

---

Below the southern skies, the telescopes of Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF’s NOIRLab, bask in the starlight of the brilliant Milky Way. Speckled with multi-colored stars, our home galaxy in this image stretches down into the city-lit horizon, just grazing past the Víctor M. Blanco 4-meter Telescope (left) and SMARTS 1.5-meter Telescope (right). The Small and Large Magellanic Clouds that accompany our home galaxy are seen to the left of the Blanco telescope. In between the telescopes blooms a deep shade of red that permeates through the tendrils of the Milky Way. This is the Gum Nebula, an emission nebula that blazes with the light of gas ionized by its host stars. From our perspective it holds a bountiful number of cosmic objects, from globular clusters, to the Vela Pulsar, and even to an 11,000-year-old supernova remnant.