Starship Asterisk*

Credit: ESA/Hubble & NASA - Acknowledgement: Judy Schmidt

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Discovered in 1900 by astronomer DeLisle Stewart and here imaged by the NASA/ESA Hubble Space Telescope (HST), IC 4710 is an undeniably spectacular sight. The galaxy is a busy cloud of bright stars, with bright pockets — marking bursts of new star formation — scattered around its edges.

IC 4710 is a dwarf irregular galaxy. As the name suggests, such galaxies are irregular and chaotic in appearance, lacking central bulges and spiral arms — they are distinctly different from spirals or ellipticals. It is thought that irregular galaxies may once have been spirals or ellipticals, but became distorted over time through external gravitational forces during interactions or mergers with other galaxies. Dwarf irregulars in particular are important to our overall understanding of galactic evolution, as they are thought to be similar to the first galaxies that formed in the Universe.

IC 4710 lies roughly 25 million light-years away in the southern constellation of Pavo (The Peacock). This constellation is located in the southern skies and also contains the third-brightest globular cluster in the sky, NGC 6752, the spiral galaxy NGC 6744, and six known planetary systems (including HD 181433 which is host to a super-Earth).

The data used to create this image were gathered by Hubble’s Advanced Camera for Surveys (ACS).

Credit: ALMA (ESO/NAOJ/NRAO)/D. Fedele et al.

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Nestled in the young Ophiuchus star-forming region, 410 light-years from the Sun, a fascinating protoplanetary disc named AS 209 is slowly being carved into shape. This wonderful image was captured using the high-resolution ALMA telescope, revealing a curious pattern of rings and gaps in the dust surrounding a young star.

Protoplanetary discs are dense, rotating planes of gas and dust that surround newly formed stars; providing the matter that one day becomes orbiting planets, moons and other minor bodies. At less than one million years old, this system is very young, but already two clear gaps are being sculpted from the disc.

The outer gap is deep, wide, and largely a dust-free zone, leading astronomers to believe that a giant planet almost the mass of Saturn is orbiting here — around 800 light-minutes from the central star, and more than three times the distance between Neptune and the Sun! As the planet carves out its path, dust piles up at the outer edge of its orbit, creating ever more defined rings in the disc. The thinner, inner dust gap could have been formed by a smaller planet, but astronomers have raised the intriguing possibility that the large and distant circling planet in fact created both paths.

This inferred Saturn-like planet so far from its central star raises fascinating questions about planet formation at the edges of protoplanetary discs on particularly short timescales.

• Astronomy & Astrophysics 610:A24 (Feb 2018) DOI: 10.1051/0004-6361/201731978
  arXiv.org > astro-ph > arXiv:1711.05185 > 14 Nov 2017

Credit: Petr Horálek/ESO

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This image, taken by ESO Photo Ambassador Petr Horálek, shows the planet Venus shining brightly over ESO’s Paranal Observatory in Chile at twilight. The featured telescope is the Very Large Telescope’s Auxiliary Telescope 1, open and preparing itself to observe the night sky, which is splashed in shades of blue and orange.

ESO’s Very Large Telescope (VLT) comprises four 8.2-metre Unit Telescopes, and four 1.8-metre Auxiliary Telescopes (ATs) — like the one posing in the foreground of the image — whose captured light can be combined to form the VLT Interferometer (VLTI). By combining the light from multiple telescopes positioned in different places across the observatory site, the VLTI allows astronomers to see details up to 25 times finer than with the individual telescopes.

The light beams are then combined using a complex system of mirrors in underground tunnels where the light paths must be kept equal to distances less than 1/1000 mm over a hundred metres. This unbelievable technology means the VLTI can reconstruct images with an angular resolution of milliarcseconds — equivalent to distinguishing the two headlights of a car at the distance of the Moon.

starsurfer wrote:Cave Nebula (Sh2-155)
https://www.astrobin.com/260706/C/
Copyright: Tommy Nawratil
0a19b185468c7519389094af061f44c4.1824x0.jpg

Credit: ESA/Hubble & NASA, RELICS Acknowledgement: D. Coe et al.

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This image from the NASA/ESA Hubble Space Telescope shows the galaxy cluster PLCK G004.5-19.5. It was discovered by the ESA Planck satellite through the Sunyaev-Zel’dovich effect — the distortion of the cosmic microwave background radiation in the direction of the galaxy cluster, by high energy electrons in the intracluster gas. The large galaxy at the centre is the brightest galaxy in the cluster and the dominant object in this image, and above it a thin, curved gravitational lens arc is visible. This is caused by the gravitational forces of the cluster bending the light from stars and galaxies behind it, in a similar way to how a glass lens bends light.

Several stars are visible in front of the cluster — recognisable by their diffraction spikes — but aside from these, all other visible objects are distant galaxies. Their light has become redshifted by the expansion of space, making them appear redder than they actually are. By measuring the amount of redshift, we know that it took more than 5 billion years for the light from this galaxy cluster to reach us. The light of the galaxies in the background had to travel for even longer than that, making this image an extremely old window into the far reaches of the Universe.

This image was taken by Hubble’s Advanced Camera for Surveys (ACS) and Wide-Field Camera 3 (WFC3) as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.

Image Credit: ESO/M. Wittkowski (ESO)

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This ghostly image features a distant and pulsating red giant star known as R Sculptoris. Situated 1200 light-years away in the constellation of Sculptor, R Sculptoris is something known as a carbon-rich asymptotic giant branch (AGB) star, meaning that it is nearing the end of its life. At this stage, low- and intermediate-mass stars cool off, create extended atmospheres, and lose a lot of their mass — they are on their way to becoming spectacular planetary nebulae.

While the basics of this mass-loss process are understood, astronomers are still investigating how it begins near the surface of the star. The amount of mass lost by a star actually has huge implications for its stellar evolution, altering its future, and leading to different types of planetary nebulae. As AGB stars end their lives as planetary nebulae, they produce a vast range of elements — including 50% of elements heavier than iron — which are then released into the Universe and used to make new stars, planets, moons, and eventually the building blocks of life.

One particularly intriguing feature of R Sculptoris is its dominant bright spot, which looks to be two or three times brighter than the other regions. The astronomers that captured this wonderful image, using ESO’s Very Large Telescope Interferometer (VLTI), have concluded that R Sculptoris is surrounded by giant “clumps” of stellar dust that are peeling away from the shedding star. This bright spot is, in fact, a region around the star with little to no dust, allowing us to look deeper into the stellar surface.

This image captures an extremely small section of the sky: approximately 20x20 milliarcseconds. For comparison, Jupiter has an angular size of approximately 40 arcseconds.

• Astronomy & Astrophysics 601:A3 (May 2017) DOI: 10.1051/0004-6361/201630214
  arXiv.org > astro-ph > arXiv:1702.02574 > 08 Feb 2017