Starship Asterisk*

Image Credit: Gerhard Hüdepohl/ESO

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In this image, the first rays of the morning Sun shine down upon Cerro Paranal in northern Chile, the home of ESO's Very Large Telescope (VLT) — signalling that another successful night of observations has concluded at the world’s most productive ground-based astronomical facility.

Rising 2635 metres above sea level, the VLT’s site is amongst the best in the world for gazing deep into the Universe. Giving a sense of the site’s altitude is the apparent “sea” in the background. This is, however, a trick of the eye; the Atacama Desert, where ESO’s VLT is located, is a very dry place. Rather than liquid water, the distant, blue-hued sea is instead composed of clouds that form at lower elevations.

Credit: ESA/Hubble & NASA, D. Rosario Acknowledgement: L. Shatz

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This image shows the spiral galaxy NGC 5037, which is found in the constellation of Virgo and was first documented by William Herschel in 1785. It lies about 150 million light-years away from Earth, and yet it is possible to see the delicate structures of gas and dust within the galaxy in extraordinary detail. This was made possible by Hubble’s Wide Field Camera 3 (WFC3), which was used to collect the exposures that were combined to create this image.

WFC3 is a very versatile camera, as it can collect ultraviolet, visible and infrared light, thereby providing a wealth of information about the objects that it observes. WFC3 was installed on Hubble by astronauts in 2009, during servicing mission 4, which was Hubble’s fifth and final servicing mission. Servicing mission 4 was intended to prolong Hubble’s life for another five years. 12 years later, both Hubble and WFC3 remain in active use!

Image Credit: ESO/Iodice et al.

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If you look closely at the faint and fuzzy centre of this picture, you will find a ghostly galaxy — the not-so-spooky-sounding UDG4 — captured using ESO’s VLT Survey Telescope (VST).

UDG stands for ultra-diffuse galaxy: objects as large as the Milky Way but with 100 – 1000 times fewer stars. These galaxies are extremely faint and lack star-forming gas, which makes them appear almost like a fluffy cosmic cloud, or a smudge in space. Their origins remain uncertain, but astronomers speculate that they could be “failed” galaxies that lost their gas supply early in their lifetimes.

This image of UDG4 was taken as part of a study from a much larger program, the VST Early-type Galaxy Survey (VEGAS), which aims to investigate very faint structures in galaxy clusters — large groups of many galaxies bound together by gravity. The study, led by Enrichetta Iodice from the Istituto Nazionale di Astrofisica in Italy, has found several UDGs in the Hydra Cluster, but more observations are needed to elucidate their true nature.

Given their flimsy appearance, UDGs can be difficult to spot. Nevertheless, the VST, equipped with its OmegaCAM camera, provides exquisite sensitivity to light, allowing astronomers to study such elusive objects.

• Astronomy & Astrophysics 642:A48 (Oct 2020) DOI: 10.1051/0004-6361/202038523
• arXiv.org > astro-ph > arXiv:2007.11533 > 22 Jul 2020

Credit: ESA/Hubble & NASA, A. Riess Acknowledgement: M. Zamani

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This image features the spiral galaxy NGC 691, imaged in fantastic detail by Hubble’s Wide Field Camera 3 (WFC3). This galaxy is the eponymous member of the NGC 691 galaxy group, a group of gravitationally bound galaxies that lie about 120 million light-years from Earth.

Objects such as NGC 691 are observed by Hubble using a range of filters. Each filter only allows certain wavelengths of light to reach Hubble’s WFC3. The images collected using different filters are then coloured by specialised visual artists who can make informed choices about which colour best corresponds to which filter. By combining the coloured images from individual filters, a full-colour image of the astronomical object can be recreated. In this way, we can get remarkably good insight into the nature and appearance of these objects.

bystander wrote: ↑Mon May 31, 2021 4:36 pm The Eponymous NGC 691
ESA Hubble Picture of the Week | 2021 May 31

Credit: ESA/Hubble & NASA, A. Riess Acknowledgement: M. Zamani

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This image features the spiral galaxy NGC 691, imaged in fantastic detail by Hubble’s Wide Field Camera 3 (WFC3). This galaxy is the eponymous member of the NGC 691 galaxy group, a group of gravitationally bound galaxies that lie about 120 million light-years from Earth.

Objects such as NGC 691 are observed by Hubble using a range of filters. Each filter only allows certain wavelengths of light to reach Hubble’s WFC3. The images collected using different filters are then coloured by specialised visual artists who can make informed choices about which colour best corresponds to which filter. By combining the coloured images from individual filters, a full-colour image of the astronomical object can be recreated. In this way, we can get remarkably good insight into the nature and appearance of these objects.