Image of the Week

3 August 2022: The Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory, a Program of NSF’s NOIRLab, in Chile is shown here juxtaposed against the bright Milky Way in the background. The green light above the clouds in this image is airglow, an atmospheric phenomenon caused when trace particles and gasses in the atmosphere become electrically charged or ionized. Their atoms release their own light when they recombine at night and create a faint glow. The glow is so faint that it’s rare to see airglow with the naked eye — it’s easier to capture it in long-exposure photos like this Image of the Week. Airglow is one reason why the night sky is never truly dark even in places far from light pollution. However, its presence alone generally doesn’t cause major problems when astronomers observe the sky at night.

27 July 2022: RCW 120, also known as Sharpless 2-3, is an emission nebula and star-forming region located in the constellation Scorpius, about 4300 light-years away from Earth. The glowing nebula was captured here by the SMARTS 0.9-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF’s NOIRLab. This HII region shines in the red color of ionized hydrogen gas. Immense heat generated from young, massive stars within energizes the gas, that then releases light in deep red and infrared wavelengths. The dark lanes in the nebula are less energized areas and thus do not appear to glow despite being made of the same material. Within the gas, bright stars are a common sight in emission nebulae, and are responsible for fusing together light elements to form many of the heavier elements in the cosmos, such as silicon and iron. RCW 120, however, houses an unusual embryonic star – one that …

20 July 2022: At first glance, it might appear as though this image was taken during the day, with the deep blue sky arching over Vera C. Rubin Observatory, a Program of NSF’s NOIRLab. On closer inspection, however, a sprinkling of stars is visible throughout the sky, revealing that it was actually taken at night, by the light of the Moon. The brightening of the sky is due to the artificial light from areas densely populated by humans, which can be seen as clusters of bright lights on the horizon. The light from the cities is so obvious in this image because the photographer used a long exposure time. If you were to visit this spot in person then the night sky would actually be very dark, and the stars would be far more visible. In fact, one of the reasons why Rubin Observatory’s location on the Cerro Pachón ridge in north-central Chile …

13 July 2022: 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.

6 July 2022: There’s more going on in this picture than you might think. This image shows Gemini North, located on Maunakea in Hawai‘i. Gemini North is one half of the International Gemini Observatory, a Program of NSF’s NOIRLab. To the lower left of Gemini is a red glowing light source. This is from the eruption of the Halemaʻumaʻu crater of the Kīlauea volcano, ongoing since late September 2021. Further lower left of Gemini is the faint green light of Hilo, Hawai‘i, mostly hidden by the layer of clouds that often covers the ground as seen from Maunakea. This is a form of light pollution, caused by excessive light shining up into the night sky above. However, protected by the high altitude, Gemini North is frequently shielded by a thick blanket of cloud. This barrier obscures urban light pollution and ambient natural light coming from the island and ocean below. This photo was …

29 June 2022: A remarkable array of colors is visible in the night sky over Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF’s NOIRLab, in this image. We tend to assume that the night sky should be inky black and punctuated by stars, although it is rarely visible in cities and other highly-populated areas because of light pollution from artificial, man-made light. Interestingly, however, the night sky is not actually pitch black in the absence of light pollution. It instead reveals a beautiful array of subtle colors that arise from various phenomena. Most of the color in this image is due to red and green airglow, which is the term used to describe the slight brightening of the night sky caused by chemical reactions taking place in Earth’s atmosphere.

22 June 2022: This Image of the Week is a composite panorama of the entire night sky taken from the platforms of Gemini South in Chile (left) and Gemini North in Hawai‘i (right). These two telescopes comprise the International Gemini Observatory, a Program of NSF’s NOIRLab. The bright white band streaking from left to right is zodiacal light, created by sunlight scattering off interplanetary dust dispersed throughout the Solar System. This light appears along the pathway of the Sun and planets across the sky, known as the ecliptic, and it's so bright that it can easily be mistaken for light pollution on a dark night. The bright patch of light at the center of the image is directly opposite the Sun in the sky. This spot is the Gegenschein. On the left side of the image you can zoom in to see a rising Jupiter along with Venus (brightest spot on the left), …

15 June 2022: NGC 7020, a barred lenticular galaxy in the southern constellation Pavo, holds a geometric mystery. Clear but subtle in this image from Gemini South, one half of the International Gemini Observatory, a Program of NSF’s NOIRLab, the core of NGC 7020 is visibly hexagonal in shape. A hexagon is not a common shape for any celestial body, let alone an entire galaxy. To form a hexagonal structure such as this, a considerable number of stars must orbit in a very narrow band. This orbital path includes two denser regions of stars seen on the left and right sides of the hexagon, which are known as “ansae”. NGC 7020’s unusual shape seems to be the product of a very rare orbital resonance, or an as-yet-unknown phenomenon. The 8-meter Gemini South telescope is located on Cerro Pachón in the Chilean Andes. Along with the other half of the international Gemini observatory, Gemini …

8 June 2022: Gemini South, one half of the International Gemini Observatory, a Program of NSF’s NOIRLab, is seen here with its laser guide star in action. Both of the Gemini telescopes use laser guide stars to provide data for the calibration of their adaptive optics, systems of deformable mirrors that compensate for fluctuations in the upper atmosphere which can blur the images of distant stars and galaxies. The laser excites trace gas particles high in Earth’s upper atmosphere. Software then analyzes feedback from the laser to provide a model for the adaptive optics to map against. The laser guide stars can also be augmented by additional adaptive optics systems that use images of real stars from the telescope itself, such as the Natural Guide Star Next Generation Sensor (NGS-2). This photo was taken as part of the recent NOIRLab 2022 Photo Expedition to all the NOIRLab sites.

1 June 2022: Typically, our Images of the Week feature observatories, starry night skies, or images captured by telescopes — not blazing blue skies! This image features the glorious Maunakea in Hawai‘i, where the Gemini North telescope, one half of Gemini Observatory, a Program of NSF’s NOIRLab, is fortunate enough to have its home. You can see Gemini North if you zoom in on the summit. Maunakea is a dormant volcano that peaks over 4000 meters (13,000 feet) above sea level. Its great height means that different locations on its slopes enjoy very different climates. The summit, for example, is arid and very cold. The gentle slopes also minimize the amount of turbulent air passing over the summit. These conditions, in conjunction with the spectacularly cloud-free skies at the volcano’s summit caused by an inversion layer in the air, create an ideal environment for observing, whether with eyes or electronics.

25 May 2022: Captured by the Mosaic camera on the Nicholas U. Mayall 4-meter Telescope at the Kitt Peak National Observatory (KPNO), a Program of NSF’s NOIRLab, the spiral galaxy NGC 2403, also known as Caldwell 7, highlights the dynamic birth and death of stars. The glowing red spots dotting the galaxy are clouds of ionized hydrogen gas known as HII regions. These areas indicate the birth of young, hot stars, which often ionize nearby hydrogen gas during their dynamic formation. Conversely NGC 2403 has also been the home of the brightest and nearest observed death of a star this millennium: the supernova SN 2004dj. The region in NGC 2403 that contained the star which became a supernova in 2004 had been observed both before, during and after the explosion, providing a fascinating timeline of the impact of the event. Since star formation occurs on a timescale much longer than a human lifetime, …

18 May 2022: A total lunar eclipse transformed the sky on the evening of 15 May 2022 and photographers at NOIRLab facilities in Arizona and Chile took advantage of clear skies to capture the event. This week’s Image of the Week shows the eclipse as seen from Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF’s NOIRLab, near La Serena, Chile. The crimson Moon shines above the Milky Way in the center left of the image. At the bottom of the image are the Víctor M. Blanco 4-meter Telescope (center) and Curtis Schmidt Telescope (left). In the southern hemisphere, the eclipse appeared extraordinarily dark as a result of the ash from the 2021 Hunga Tonga–Hunga Ha'apai volcanic eruption. In the northern hemisphere, the lunar eclipse was captured in this close-up image taken from the Visitor Center at Kitt Peak National Observatory (KPNO), also a Program of NSF’s NOIRLab, near Tucson, Arizona. You can …

11 May 2022: Shown here is the partial lunar eclipse of 19 November 2021 as seen from Kitt Peak National Observatory, a Program of NSF’s NOIRLab. This Image of the Week captures the eclipse above the Nicholas U. Mayall 4-meter Telescope in the Arizona-Sonoran Desert of Arizona. While technically a deep partial eclipse with 97% of the Moon in Earth’s shadow, or umbra, this eclipse was deep enough to give the Moon a pronounced red tint and decrease its brightness. The only light the Moon ever “shines” with is reflected sunlight. But while the Moon is within the umbra, the sunlight illuminating the Moon is scattered by Earth’s atmosphere. Essentially passing through a prism, the sunlight refracts in Earth’s atmosphere and takes on a crimson hue, which then illuminates the Moon. This hue can be seen in this image, taken on the same night through a 600-mm focal length camera lens (equivalent to …

4 May 2022: Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF NOIRLab, is depicted here with the Milky Way and several nebulae within it, including the Lagoon Nebula and Rho Ophiuchi cloud complex. A number of CTIO telescopes are captured in this 360-degree panorama, including, from left to right: the UBC Southern Observatory, the SMARTS 1.0-meter Telescope, the Curtis Schmidt Telescope, the Víctor M. Blanco 4-meter Telescope, the SMARTS 1.5-meter Telescope and the SMARTS 0.9-meter Telescope. Various other, more unusual night sky phenomena are also visible. The white glow on the left of the image is zodiacal light, arising from interplanetary dust illuminated by the Sun. The green, orange, and reddish “clouds” near the horizon are airglow, caused by trace gasses in the upper atmosphere.

27 April 2022: Gemini North, one half of the international Gemini Observatory, a Program of NSF’s NOIRLab, uses a laser beam traveling through Earth’s atmosphere to adjust its adaptive optics. Like many large research telescopes today, Gemini North uses adaptive optics — bending its mirrors to compensate for atmospheric turbulence or “seeing”, which can blur the images of distant objects like stars and galaxies. The laser beam, seen here as a pink-orange stripe on the sky, travels into the upper atmosphere where it creates a bright spot of light that provides a reference point for the telescope to follow, and correct for, the atmospheric turbulence. This long-exposure photograph shows the laser tracking its target near the zenith, appearing to paint the sky with light. The stars appear as trails as they revolve around the north celestial pole during the long exposure.

20 April 2022: The aboveground portion of the McMath-Pierce Solar Telescope at Kitt Peak National Observatory (KPNO), a Program of NSF’s NOIRLab, is seen here at sunset. The McMath-Pierce Solar Telescope, located about 88 kilometers (55 miles) from Tucson, Arizona, saw its first light in 1962. It continued operating for an impressive 55 years until being decommissioned in 2017. For much of its life, it was the largest solar telescope on Earth. The McMath-Pierce telescope was unusual in that it used a large flat mirror called a heliostat to track the Sun across the sky and continually send sunlight down into an underground tunnel where the telescope itself was located. This helped to minimize hot air currents in the light path of the telescope, which would degrade the quality of the image. Though decommissioned, the McMath-Pierce Solar Telescope facility is being repurposed as the NOIRLab Windows on the Universe Center for Astronomy Outreach.

13 April 2022: This image, which looks a little like an enormous bubble in space, features a planetary nebula known as EGB 6. It was imaged by the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory (KPNO), a Program of NSF’s NOIRLab. Planetary nebulae, notoriously, have nothing to do with planets. They form during the dying millennia of intermediate-mass stars, stars with masses between one and eight times the mass of the Sun. “Dying millennia” might sound like a very long time, but compared to the overall lifespan of a star, planetary nebulae are extremely short-lived. Towards the end of their life cycle, intermediate-mass stars enter the red giant phase, during which fusion reactions temporarily reignite in a dying star’s core. Layers of gas, shed or ejected during the red giant phase, absorb vast amounts of energy and create the gorgeous phenomena known as planetary nebulae. The dying millenia only last …

6 April 2022: The dust-filled center of our Milky Way galaxy stretches up from the Víctor M. Blanco 4-meter Telescope and one of the SMARTS Consortium telescopes at Cerro Tololo Inter-American Observatory (CTIO) in this Image of the Week. CTIO, a Program of NSF’s NOIRLab, is located at 2200 meters (7200 feet) in the mountains of Chile. Far from major cities, the dark landscape provides American, Chilean, and international researchers clear views of the southern sky. The spectacular green colors in the sky are not due to the aurora borealis, but instead are due to a phenomenon known as airglow. Airglow is not an optical illusion, but a genuine light source that results from chemical reactions in Earth’s upper atmosphere. It is far too faint to be visible during the daytime, and in most human-inhabited places it is drowned out by light pollution. However, out in the Chilean desert, it is possible to …

30 March 2022: Gemini North, of the international Gemini Observatory (a Program of NSF’s NOIRLab), stands peacefully in the foreground, under a crystal clear sky. The dramatic upward sweep of milky and sooty patches of the Milky Way galaxy is seen in the background. The dark tendrils that permeate the Milky Way are due to enormous clouds of cosmic dust. These clouds of tiny particles absorb and scatter light, making huge patches of the Milky Way appear dark to human eyes from our vantage point here on Earth. Telescopes such as Gemini North, however, see the night sky differently. They are designed to collect far more light that the human eye can, thanks to their large primary mirrors. They can also detect ranges of light that humans cannot, meaning that they can probe areas of cosmic dust, giving us information on things that would otherwise remain obscured.

23 March 2022: This Image of the Week captures the use of the laser guide star (LGS) on Gemini South, the southern twin of the international Gemini Observatory, a Program of NSF’s NOIRLab, during a night of observations on Cerro Pachón in the Chilean Andes. The LGS creates a constellation of five artificial stars, by causing sodium atoms 90 kilometers up in the atmosphere to glow. By tracking the atmosphere’s effect on these “stars”, the adaptive optics system within Gemini South can correct for distortions caused by turbulence in the atmosphere. These adjustments improve observations so much that a squiggle of light can become a distinct star, galaxy or other astronomical object. While it may seem that this laser must be shockingly powerful, it actually uses only 10–15 watts of energy, about the same as a bedside lamp. A similar LGS system is in use at Gemini North, which you can see in …