Starship Asterisk*

Credit: ESO/VPHAS+ team. Acknowledgement: Cambridge Astronomical Survey Unit

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In this Picture of the Week, we take a deep plunge into the ocean of stars in the IC4701 nebula. This nebula is located in the Sagittarius constellation, and it is twice as wide as the full Moon in the sky. The energetic light from newly-born stars ionizes the hydrogen gas in the nebula, causing it to emit the intense reddish hue seen in this picture. The dark clouds in this image contain large amounts of interstellar dust, too dense for the light of the background stars to pierce through it.

The IC4701 nebula is part of a rich and vast complex of dust and gas within which new stars spring to life. When stars are born, most of them are cooler, redder, and less massive than our own Sun. Hotter, more massive stars are much rarer, and they quickly burn through all their fuel and die. This makes these brilliant blue and massive stars, and their surrounding glowing gas, beacons of recent star formation.

A spiral galaxy. It is irregularly-shaped and its spiral arms are difficult to distinguish. The edges are faint and the core has a pale glow. It is dotted with small, wispy, pink regions where stars are forming. A few stars and small galaxies in warm colours are visible around it.

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Image Credit: ESA/Hubble & NASA, C. Kilpatrick

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The irregular spiral galaxy NGC 5486 hangs against a background of dim, distant galaxies in this image from the NASA/ESA Hubble Space Telescope. The tenuous disc of the galaxy is threaded through with pink wisps of star formation, which stand out from the diffuse glow of the galaxy’s bright core. While this particular galaxy has indistinct, meandering spiral arms it lies close to the much larger Pinwheel Galaxy, one of the best known examples of ‘grand design’ spiral galaxies with prominent and well-defined spiral arms. In 2006 Hubble captured an image of the Pinwheel Galaxy which was — at the time — the largest and most detailed photo of a spiral galaxy ever taken with Hubble.

NGC 5486 lies 110 million light-years from Earth in the constellation Ursa Major. Constellations are not only patterns of bright stars, but also a system that astronomers use to divide the sky into regions. There are 88 of these regions, and each has an associated constellation depicting a mythological figure, an animal, or even an item of scientific equipment. This strange celestial menagerie contains everything from Ursa Major’s great bear to a toucan, a sea monster, a telescope, and even a painter's easel!

This observation comes from a selection of Hubble images exploring the detritus left behind by Type II supernovae. As massive stars reach the end of their lives they cast off huge amounts of gas and dust before ending their lives in titanic supernova explosions. NGC 5486 hosted a supernova in 2004, and astronomers used the keen vision of Hubble’s Advanced Camera for Surveys to explore the aftermath in the hopes of learning more about these explosive events.

Image Credit: International Gemini Observatory/NOIRLab/NSF/AURA/J. Chu

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Maunakea, the huge volcano in the background of this image, is one of the five volcanoes on the island of Hawai‘i. Maunakea is home to a number of astronomical observatories, including Gemini North, one half of the International Gemini Observatory, operated by NSF’s NOIRLab.

It may not look like it, but this image was taken at night, not on a sunny afternoon as it might appear at first glance. The Moon reflects sunlight rather evenly across the visible spectrum, albeit at a brightness of only 0.3 lux — about 300,000 times fainter than the Sun. With a long exposure, moonlight can appear to illuminate scenery just as though it were a sunny day. If you look closely you might notice a few stars visible in the sky.

bystander wrote: ↑Mon Mar 06, 2023 3:10 pm Plunge into a Stellar Ocean
ESO Picture of the Week | 2023 Mar 06

potw2310a[1].jpgCredit: ESO/VPHAS+ team. Acknowledgement: Cambridge Astronomical Survey Unit

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In this Picture of the Week, we take a deep plunge into the ocean of stars in the IC4701 nebula. This nebula is located in the Sagittarius constellation, and it is twice as wide as the full Moon in the sky. The energetic light from newly-born stars ionizes the hydrogen gas in the nebula, causing it to emit the intense reddish hue seen in this picture. The dark clouds in this image contain large amounts of interstellar dust, too dense for the light of the background stars to pierce through it.

The IC4701 nebula is part of a rich and vast complex of dust and gas within which new stars spring to life. When stars are born, most of them are cooler, redder, and less massive than our own Sun. Hotter, more massive stars are much rarer, and they quickly burn through all their fuel and die. This makes these brilliant blue and massive stars, and their surrounding glowing gas, beacons of recent star formation.

Credit:D. López Calvin (solarigrafia.com), J. C. Muñoz Mateos / ESO. CC-BY-NC 4.0

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This picture of the week shows the Sun’s path on the sky as seen from ESO’s Paranal Observatory in Chile. The picture was taken with a pinhole camera with an exposure of 8 months, from 17 April to 11 December 2018. The tall structure in the foreground is the “seeing monitor”, which measures the blur/twinkling of the stars due to the atmospheric turbulence. In the background we can see several domes; the ones to the centre-left are part of the Very Large Telescope, and the rightmost one is the VLT Survey Telescope.

But what are those bright coloured lines behind them? They are created by the Sun as it moves in the sky throughout the day, leaving an imprint on the sheet of photographic paper placed inside the pinhole camera.

The camera was facing west, so here we see hundreds of sunsets. But as the Earth moves around the Sun, each day the Sun sets at a different point along the horizon. The shortest arc all the way to the right of the image corresponds to the winter solstice (June 21 in the Southern Hemisphere), when the Sun reaches its lowest elevation. From that point onwards, the Sun moves southward day after day, to the left in this image. The arcs become longer and higher, and the days longer and hotter. Then, on the summer solstice (December 21), the Sun reaches its highest point, which is not visible in this picture, and draws the longest arc to the left of this image.

The dark lines are due to clouds blocking the Sun. Luckily for astronomers, Paranal Observatory boasts over 300 clear days per year, hence the very few dark bands in this image.

A wide band of bluish light extends from the centre of the image to the right side. It is speckled with many tiny stars, and a few small, bright red bubbles of gas, identifying it as a galaxy. The background is black, and has small galaxies and stars spread around. Most are too small to distinguish, except for two oval-shaped galaxies, each having a hazy glow around a bright centre. Image Credit: ESA/Hubble & NASA, R. Tully

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UGCA 307 hangs against an irregular backdrop of distant galaxies in this image from the NASA/ESA Hubble Space Telescope. The small galaxy consists of a diffuse band of stars containing red bubbles of gas that mark regions of recent star formation, and lies roughly 26 million light-years from Earth in the constellation Corvus. Appearing as just a small patch of stars, UGCA 307 is a diminutive dwarf galaxy without a defined structure — resembling nothing more than a hazy patch of passing cloud.

This image is part of a Hubble project to explore every known nearby galaxy, giving astronomers insights into our galactic neighbourhood. Before this set of observations, almost three quarters of nearby galaxies had been investigated by Hubble in enough detail to spot the brightest stars and build up an understanding of the stars populating each galaxy. This Hubble project set out to explore the remaining quarter of nearby galaxies by taking advantage of short gaps in Hubble’s observing schedule.

This crystal-clear image was captured by Hubble’s Advanced Camera for Surveys (ACS), which was installed on the telescope in 2002 during Servicing Mission 3B. Hubble’s vantage point in low Earth orbit means that it is above atmospheric turbulence, giving it a sharper view of the Universe. However, it is also close enough to Earth that astronauts could visit the telescope to repair and refurbish the telescope. In total, five Space Shuttle missions flew to Hubble and kept it at the forefront of astronomy by installing new instruments. The ACS replaced one of Hubble’s original instruments, the Faint Object Camera, which was built by ESA.