Pumpkin Sun

Active regions on the Sun combined to look something like a jack-o-lantern’s face on October 8, 2014. The image was captured by NASA's Solar Dynamics Observatory, or SDO, which watches the Sun at all times from its orbit in space.

The active regions in this image appear brighter because those are areas that emit more light and energy. They are markers of an intense and complex set of magnetic fields hovering in the Sun’s atmosphere, the corona. This image blends together two sets of extreme ultraviolet wavelengths at 171 and 193 Ångströms, typically colorized in gold and yellow, to create a particularly Halloween-like appearance.

Image Credit: NASA/SDO
Explanation from: https://www.nasa.gov/content/goddard/sdo-jack-o-lantern-sun

IC 2118: the Witch Head Nebula

As the name implies, this reflection nebula associated with the star Rigel looks suspiciously like a fairytale crone. Formally known as IC 2118 in the constellation Orion, the Witch Head Nebula glows primarily by light reflected from the star. The color of this very blue nebula is caused not only by blue color of its star, but also because the dust grains reflect blue light more efficiently than red. A similar physical process causes Earth's daytime sky to appear blue.

Image Credit: NASA/STScI Digitized Sky Survey/Noel Carboni
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_1209.html

VdB 152: A Ghost in Cepheus

Described as a "dusty curtain" or "ghostly apparition," mysterious reflection nebula VdB 152 really is very faint. Far from your neighborhood on this Halloween Night, the cosmic phantom is nearly 1,400 light-years away. Also catalogued as Ced 201, it lies along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of interstellar dust in the region block light from background stars or scatter light from the embedded bright star giving parts of the nebula a characteristic blue color. Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust. Though stars do form in molecular clouds, this star seems to have only accidentally wandered into the area, as its measured velocity through space is very different from the cloud's velocity. This deep telescopic image of the region spans about 7 light-years.

Image Credit: Stephen Leshin
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_2385.html

Fornax Galaxy Cluster

Countless galaxies vie for attention in this monster image of the Fornax Galaxy Cluster, some appearing only as pinpricks of light while others dominate the foreground. One of these is the lenticular galaxy NGC 1316. The turbulent past of this much-studied galaxy has left it with a delicate structure of loops, arcs and rings that astronomers have now imaged in greater detail than ever before with the VLT Survey Telescope. This astonishingly deep image also reveals a myriad of dim objects along with faint intracluster light.

Captured using the exceptional sky-surveying abilities of the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile, this deep view reveals the secrets of the luminous members of the Fornax Cluster, one of the richest and closest galaxy clusters to the Milky Way. This 2.3-gigapixel image is one of the largest images ever released by ESO.

Perhaps the most fascinating member of the cluster is NGC 1316, a galaxy that has experienced a dynamic history, being formed by the merger of multiple smaller galaxies. The gravitational distortions of the galaxy’s adventurous past have left their mark on its lenticular structure. Large ripples, loops and arcs embedded in the starry outer envelope were first observed in the 1970s, and they remain an active field of study for contemporary astronomers, who use the latest telescope technology to observe the finer details of NGC 1316’s unusual structure through a combination of imaging and modelling.

The mergers that formed NGC 1316 led to an influx of gas, which fuels an exotic astrophysical object at its centre: a supermassive black hole with a mass roughly 150 million times that of the Sun. As it accretes mass from its surroundings, this cosmic monster produces immensely powerful jets of high-energy particles , that in turn give rise to the characteristic lobes of emission seen at radio wavelengths, making NGC 1316 the fourth-brightest radio source in the sky.

NGC 1316 has also been host to four recorded type Ia supernovae, which are vitally important astrophysical events for astronomers. Since type Ia supernovae have a very clearly defined brightness, they can be used to measure the distance to the host galaxy; in this case, 60 million light-years. These “standard candles” are much sought-after by astronomers, as they are an excellent tool to reliably measure the distance to remote objects. In fact, they played a key role in the groundbreaking discovery that our Universe is expanding at an accelerating rate.

This image was taken by the VST at ESO’s Paranal Observatory as part of the Fornax Deep Survey, a project to provide a deep, multi-imaging survey of the Fornax Cluster. The team, led by Enrichetta Iodice (INAF – Osservatorio di Capodimonte, Naples, Italy), have previously observed this area with the VST and revealed a faint bridge of light between NGC 1399 and the smaller galaxy NGC 1387. The VST was specifically designed to conduct large-scale surveys of the sky. With its huge corrected field of view and specially designed 256-megapixel camera, OmegaCAM, the VST can produce deep images of large areas of sky quickly, leaving the much larger telescopes — like ESO’s Very Large Telescope (VLT) — to explore the details of individual objects.

Image Credit: ESO/A. Grado and L. Limatola
Explanation from: https://www.eso.org/public/news/eso1734/

Milky Way Galaxy seen over Auxiliary Telescope

Brilliant blue stars litter the southern sky and the galactic bulge of our home galaxy, the Milky Way, hangs serenely above the horizon in this spectacular shot of ESO’s Paranal Observatory.

This image was taken atop Cerro Paranal in Chile, home to ESO’s Very Large Telescope (VLT). In the foreground, the open dome of one of the four 1.8-metre Auxiliary Telescopes can be seen. The four Auxiliary Telescopes can be utilised together, to form the Very Large Telescope Interferometer (VLTI).

The plane of the Milky Way is dotted with bright regions of hot gas. The very bright star towards the upper left corner of the frame is Antares — the brightest star in Scorpius and the fifteenth brightest star in the night sky.

Image Credit: ESO/B. Tafreshi
Explanation from: https://www.eso.org/public/images/potw1744a/

Saturn seen by Cassini spacecraft

Stunning views like this image of Saturn's night side are only possible thanks to our robotic emissaries like Cassini. Until future missions are sent to Saturn, Cassini's image-rich legacy must suffice.

Because Earth is closer to the Sun than Saturn, observers on Earth only see Saturn's day side. With spacecraft, we can capture views (and data) that are simply not possible from Earth, even with the largest telescopes.

This view looks toward the sunlit side of the rings from about 7 degrees above the ring plane. The image was taken in visible light with the wide-angle camera on NASA's Cassini spacecraft on June 7, 2017.

The view was obtained at a distance of approximately 751,000 miles (1.21 million kilometers) from Saturn. Image scale is 45 miles (72 kilometers) per pixel.

The Cassini spacecraft ended its mission on September 15, 2017.

Image Credit: NASA/JPL-Caltech/Space Science Institute
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21350

The Moon seen by Galileo spacecraft

During its flight, the Galileo spacecraft returned images of the Moon. The Galileo spacecraft surveyed the Moon on December 7, 1992, on its way to explore the Jupiter system in 1995-1997. The left part of this north pole view is visible from Earth. This color picture is a mosaic assembled from 18 images taken by Galileo's imaging system through a green filter. The left part of this picture shows the dark, lava-filled Mare Imbrium (upper left); Mare Serenitatis (middle left), Mare Tranquillitatis (lower left), and Mare Crisium, the dark circular feature toward the bottom of the mosaic. Also visible in this view are the dark lava plains of the Marginis and Smythii Basins at the lower right. The Humboldtianum Basin, a 650-kilometer (400-mile) impact structure partly filled with dark volcanic deposits, is seen at the center of the image. The Moon's north pole is located just inside the shadow zone, about a third of the way from the top left of the illuminated region.

Image Credit: NASA/JPL/USGS
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA00404

Galaxy Cluster WHL J24.3324-8.477

This NASA/ESA Hubble Space Telescope image is chock-full of galaxies — each glowing speck is a different galaxy, bar the bright flash in the middle of the image which is actually a star lying within our own galaxy that just happened to be in the way. At the centre of the image lies something especially interesting, the centre of the massive galaxy cluster called WHL J24.3324-8.477, including the brightest galaxy of the cluster.

The Universe contains structures on various scales — planets collect around stars, stars collect into galaxies, galaxies collect into groups, and galaxy groups collect into clusters. Galaxy clusters contain hundreds to thousands of galaxies bound together by gravity. Dark matter and dark energy play key roles in the formation and evolution of these clusters, so studying massive galaxy clusters can help scientists to unravel the mysteries of these elusive phenomena.

This infrared image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3 as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study. Such research will tell us more about our cosmic origins.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1743a/

Jupiter, Io and Europa seen by Juno spacecraft

This color-enhanced image of Jupiter and two of its largest moons -- Io and Europa -- was captured by NASA's Juno spacecraft as it performed its eighth flyby of the gas giant planet.

The image was taken on Sept. 1, 2017 at 3:14 p.m. PDT (6:14 p.m. EDT). At the time the image was taken, the spacecraft was about 17,098 miles (27,516 kilometers) from the tops of the clouds of the planet at a latitude of minus 49.372 degrees.

Closer to the planet, the Galilean moon of Io can be seen at an altitude of 298,880 miles (481,000 kilometers) and at a spatial scale of 201 miles (324 kilometers) per pixel. In the distance (to the left), another one of Jupiter's Galilean moons, Europa, is visible at an altitude of 453,601 miles (730,000 kilometers) and at a spatial scale of 305 miles (492 kilometers) per pixel.

Image Credit: NASA/JPL-Caltech/SwRI/MSSS/Roman Tkachenko
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21968