Starship Asterisk*

Credit: CTIO/NOIRLab/NSF/AURA/D. Munizaga

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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 read more about how a lunar eclipse happens in this recent Image of the Week.

The eclipse was the longest total lunar eclipse visible from the Americas since 1989. It also coincided with a “supermoon”, which occurs when the Moon is at its nearest point to Earth.

Image Credit: F. Aedo, F. Durán / ESO

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This ominous Picture of the Week shows our very own Moon undergoing a total lunar eclipse. The image was taken on the night of May 15 2022 from ESO’s Paranal Observatory in Chile. During a lunar eclipse, the Earth is positioned directly between the Sun and the Moon, blocking some of the Sun’s light. This casts a shadow across the Moon’s surface.

The red colour is caused by the Sun’s rays interacting with the Earth’s atmosphere. Light from the Sun contains a whole spectrum of colours. Blue light is dispersed by the atmosphere through a process called Rayleigh scattering (which makes the sky blue) while red light can pass through the atmosphere more easily, becoming slightly deflected. This red light reaches the Moon’s surface, giving rise to its dramatic crimson hue.

This photo was taken during the eclipse’s totality, when the Earth is causing the largest blockage of the Sun’s light. It was taken by two ESO colleagues at Paranal Observatory using an amateur telescope nicknamed “UT5” as a nod to its much larger siblings, the four 8-m Unit Telescopes at ESO’s Very Large Telescope.

Fun fact: astronomers often take spectra of lunar eclipses to understand the signatures that life can leave on Earth’s atmosphere, which is a very useful reference when searching for similar signatures in exoplanets.

Image Credit: ESA/Hubble & NASA, F. Ferraro

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The muted red tones of the globular cluster Liller 1 are partially obscured in this image by a dense scattering of piercingly blue stars. In fact, it is thanks to Hubble’s Wide Field Camera 3 (WFC3) that we are able to see Liller 1 so clearly in this image, because the WFC3 is sensitive to wavelengths of light that the human eye cannot detect. Liller 1 is only 30 000 light-years from Earth — relatively neighbourly in astronomical terms — but it lies within the Milky Way’s ‘bulge’, the dense and dusty region at our galaxy’s centre. Because of that, Liller 1 is heavily obscured from view by interstellar dust, which scatters visible light (particularly blue light) very effectively. Fortunately, some infrared and red visible light are able to pass through these dusty regions. WFC3 is sensitive to both visible and near-infrared (infrared that is close to the visible) wavelengths, allowing us to see through the obscuring clouds of dust, and providing this spectacular view of Liller 1.

Liller 1 is a particularly interesting globular cluster, because unlike most of its kind, it contains a mix of very young and very old stars. Globular clusters typically house only old stars, some nearly as old as the Universe itself. Liller1 instead contains at least two distinct stellar populations with remarkably different ages: the oldest one is 12 billion years old and the youngest component is just 1-2 billion years old. This led astronomers to conclude that this stellar system was able to form stars over an extraordinary long period of time.

Image Credit: KPNO/NOIRLab/NSF/AURA/M. T. Patterson (New Mexico State University) Image processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani & D. de Martin (NSF’s NOIRLab)

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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, the process has to be pieced together like a puzzle through observations of different stars in different stages of the stellar life cycle. It is very satisfying for astronomers to be able to observe supernovae, which occur incredibly quickly even by human standards, to confirm and develop theories of the life cycle of stars.

Credit: ESO/A. Ghizzi Panizza (albertoghizzipanizza.com)

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This picture of the week shows four powerful laser beams leaving Unit Telescope 4, or ‘Yepun’, at ESO’s Very Large Telescope (VLT) in Chile’s Atacama desert. These form the VLT’s 4 Laser Guide Star Facility, which enables astronomers to take extremely crisp images of the cosmos by employing a technology known as adaptive optics.

Using adaptive optics, telescopes are able to correct for the effects of atmospheric turbulence, which causes the “twinkling” and blurring of stars and other objects in the sky. To do this, a deformable mirror reshapes itself up to 1000 times per second based on the observed turbulence. Astronomers measure turbulence by monitoring a bright star in the field of view. If there isn’t a suitable star, they create artificial stars in the Earth’s upper atmosphere using lasers. The lasers in this image have a very specific orange-yellow colour (with a wavelength of 589 nm), exciting sodium atoms about 90 km above ground, causing them to shine like a star.

In the backdrop, almost appearing to follow the path of the laser beams, is the familiar band of the Milky Way stretching across the sky. Also visible is a faint green wash in the sky that results from a phenomenon known as airglow, which is light naturally emitted by atoms and molecules in the atmosphere. Airglow is only visible in areas where the sky is dark enough not to be overshadowed by light pollution.

Credit: ESA/Hubble & NASA, J. Lee and PHANGS-HST

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This image from the NASA/ESA Hubble Space Telescope shows the barred spiral galaxy NGC 7496, which lies over 24 million light-years away in the constellation Grus. This constellation, whose name is Latin for crane, is one of four constellations collectively known as the Southern Birds. The others are Pavo, Phoenix and Tucana, which depict a peacock, phoenix, and toucan respectively. The rest of the night sky is also home to a flock of ornithological constellations, including an eagle (Aquilla), swan (Cygnus), crow (Corvus), and dove (Columba).

This image comes from a collection of observations delving into the relationship between young stars and the cold, dense clouds of gas in which they form. In addition to observations with Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys, the astronomers behind this project gathered data using the Atacama Large Millimeter/submillimeter Array (ALMA), one of the largest radio telescopes in the world.

As well as shedding light on the speed and efficiency of star formation in a variety of galactic environments, this project is also creating a treasury of data incorporating both Hubble and ALMA observations. This treasure trove of data from two of the world’s most capable observatories will contribute to wider research into star formation, as well as paving the way for future science with the James Webb Space Telescope.