Starship Asterisk*

Credit: Gerhard Hüdepohl (atacamaphoto.com)/ESO

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Surrounded by the gleaming metal of one of ESO's Very Large Telescope’s (VLT) Unit Telescopes, two engineers are carrying out maintenance work on the telescope’s complex and delicate optical systems. Similar to human eyes, the eyes of ESO’s Paranal Observatory must be constantly checked, maintained and tested in order to continuously provide the very best astronomical images.

The huge 8.2-metre Unit Telescope mirrors are housed in protective structures, ensuring that the delicate opto-electronic systems are sheltered from the harsh and dusty desert surroundings. But even with this level of protection, it still pays to spring clean the mirror from time to time! This is vital, as even the slightest contamination can distort the astronomical images received.

The fine dust particles of the Atacama desert not only lower image quality, but can also have an abrasive effect on the mirror’s surface. This means that not only does the mirror have to be cleaned, but it must be periodically recoated too. This episode of the ESOcast shows the process in action!

This image was taken by ESO Photo Ambassador Gerhard Hüdepohl, who formerly worked as an electronics engineer on Cerro Paranal.

Image Credit: ESA/Hubble & NASA, J. Greene

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At first glance, the subject of this NASA/ESA Hubble Space Telescope image looks to be a simple spiral galaxy, with two pinwheeling arms emerging from a central bar of stars and material that cuts through the galactic centre. In fact, there are rings within these spiral arms, too: spirals within a spiral.

This kind of morphology is known as a multiring structure. As this description suggests, this galaxy, named NGC 2273, hosts an inner ring and two outer “pseudorings” — having so many distinct rings is rare, and makes NGC 2273 unusual. Rings are created when a galaxy’s spiral arms appear to loop around to nearly close upon one another, combined with a trick of cosmic perspective. NGC 2273’s two pseudorings are formed by two swirling sets of spiral arms coming together, and the inner ring by two arcing structures nearer to the galactic centre, which seem to connect in a similar way.

These rings are not the only unique feature of this galaxy. NGC 2273 is also a Seyfert galaxy, a galaxy with an extremely luminous core. In fact, the centre of a galaxy such as this is powered by a supermassive black hole, and can glow brightly enough to outshine an entire galaxy like the Milky Way.

Susanna Kohler wrote:

You’re looking at SPT-CL J2106-5844, the most massive distant (farther than roughly 8 billion light-years) galaxy cluster known. This composite image shows the field of the cluster, which spans a distance of roughly 3 million light-years across, in three Hubble color filters. The overlaid contours show the distribution of mass within the cluster, as recently determined by a team of scientists led by Jinhyub Kim (Yonsei University, Republic of Korea; University of California, Davis). Kim and collaborators used weak gravitational lensing — slight distortions in the shapes of background galaxies caused when their light is bent by the massive gravitational pull of this cluster — to map out the tremendous mass of SPT-CL J2106-5844. They find this cluster weighs in at a whopping ~1 quadrillion (10¹⁵) solar masses! Studying this distant, monster cluster can help us place constraints on how the universe’s large-scale structure formed and evolved.

• Astrophysical Journal 887(1):76 (2019 Dec 10) DOI: 10.3847/1538-4357/ab521e
• arXiv.org > astro-ph > arXiv:1910.04775 > 10 Oct 2019

starsurfer wrote: ↑Wed Apr 01, 2020 8:12 pm Kronberger 61
https://www.britastro.org/node/19755
Copyright: Peter Goodhew
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starsurfer wrote: ↑Wed Apr 01, 2020 8:10 pm HDW 3
https://www.astrobin.com/llcf4t/0/
Copyright: Chris Sullivan
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Image Credit: ESO/Petr Horálek

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From 18 to 20 July 2017 western Germany endured intense storms. Thunder and lightning storms lit numerous fires and drove water levels to some 1.5 metres high, flooding streets and basements across the region.

Although destructive, these storms brought their own impressive beauty. In Garching bei München, home to ESO’s Headquarters, ESO photo ambassador Petr Horálek captured this beautiful photograph of the storm over the road connecting Munich to Berlin.

Interestingly, the sky surrounding the storm is tinged with purple. Exotic colours in the sky, such as red, green, orange or purple, usually indicate the presence of charged particles in the atmosphere, often caused by weather systems and cloud formations. The colour of the sky is also related to temperature of any lightning bolts, their distance from us, the way their light is distorted before hitting our eyes, and the time of day, since the angle of sunlight as it enters and refracts through the clouds creates different colours in the atmosphere. Since most thunderstorms occur in the late afternoon, as this one did, we often see vivid colours appearing within the turbulent clouds. Purple is the colour most usually observed, and indicates that the brewing storm is likely to be a rainy one!

Image Credit: ESA/Hubble & NASA, A Filippenko

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This image depicts a swirling spiral galaxy named NGC 2906.

The blue speckles seen scattered across this galaxy are massive young stars, which emit hot, blue-tinged radiation as they burn through their fuel at an immense rate. The swathes of orange are a mix of older stars that have swollen and cooled, and low-mass stars that were never especially hot to begin with. Owing to their lower temperatures, these stars emit a cooler, reddish, radiation.

This image of NGC 2906 was captured by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3, an instrument installed on Hubble in 2009 during the telescope’s fourth servicing mission. Hubble observed this galaxy on the hunt for fading light from recent, nearby occurrences of objects known as supernovae.