Starship Asterisk*

Image Credit: ESO/Yuri Beletsky

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The soft glow of the Milky Way pours down like a waterfall over the VLT Survey Telescope (VST) at ESO’s Paranal Observatory. 2635 metres above sea level, the VST has an unparallelled view of the magnificently clear skies above Chile’s Atacama Desert. It is the largest telescope in the world dedicated to observational surveys in visible light, and it contributes to a vast range of studies, from discovering remote Solar System bodies to searching for exoplanet transits, to studying the structure and evolution of our galaxy.

Above the VST, a few stars are particularly prominent just outside the main band of the galaxy: the bright reddish star is Betelgeuse, a red supergiant 640 light-years away thought to be on the brink of a supernova explosion. Betelgeuse and Bellatrix, the fainter white star to its left, are the shoulders of Orion the Hunter, one of the most famous and easily recognisable constellations in the sky. The three stars forming a straight line above the shoulders are Orion’s belt, and the nearby purple-tinged cluster of light is the Orion Nebula. Though it looks like a fuzzy patch to the naked-eye, binoculars or a telescope reveal it to be a spectacular nebula, host to massive amounts of star formation.

Image Credit: ESA/Hubble & NASA, P. Erwin et al

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The barred spiral galaxy NGC 3887, seen here as viewed by the Wide Field Camera 3 aboard the NASA/ESA Hubble Space Telescope, lies over 60 million light-years away from us in the southern constellation of Crater (The Cup); it was discovered on 31 December 1785 by the German/British astronomer William Herschel.

Its orientation to us, while not exactly face-on, allows us to see NGC 3887’s spiral arms and central bulge in detail, making it an ideal target for studying a spiral galaxy’s winding arms and the stars within them.

The very existence of spiral arms was for a long time a problem for astronomers. The arms emanate from a spinning core and should therefore become wound up ever more tightly, causing them to eventually disappear after a (cosmologically) short amount of time. It was only in the 1960s that astronomers came up with the solution to this winding problem; rather than behaving like rigid structures, spiral arms are in fact areas of greater density in a galaxy’s disc, with dynamics similar to those of a traffic jam. The density of cars moving through a traffic jam increases at the centre of the jam, where they move more slowly. Spiral arms function in a similar way; as gas and dust move through the density waves they become compressed and linger, before moving out of them again.

bystander wrote: ↑Mon Mar 02, 2020 4:23 pm Orion Watches over Paranal
ESO Picture of the Week | 2020 Mar 02

Image Credit: ESO/Yuri Beletsky

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The soft glow of the Milky Way pours down like a waterfall over the VLT Survey Telescope (VST) at ESO’s Paranal Observatory. 2635 metres above sea level, the VST has an unparallelled view of the magnificently clear skies above Chile’s Atacama Desert. It is the largest telescope in the world dedicated to observational surveys in visible light, and it contributes to a vast range of studies, from discovering remote Solar System bodies to searching for exoplanet transits, to studying the structure and evolution of our galaxy.

Above the VST, a few stars are particularly prominent just outside the main band of the galaxy: the bright reddish star is Betelgeuse, a red supergiant 640 light-years away thought to be on the brink of a supernova explosion. Betelgeuse and Bellatrix, the fainter white star to its left, are the shoulders of Orion the Hunter, one of the most famous and easily recognisable constellations in the sky. The three stars forming a straight line above the shoulders are Orion’s belt, and the nearby purple-tinged cluster of light is the Orion Nebula. Though it looks like a fuzzy patch to the naked-eye, binoculars or a telescope reveal it to be a spectacular nebula, host to massive amounts of star formation.

Image Credit: Yuri Beletsky/ESO

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This beautiful image shows the dense heart of the Milky Way stretched out above one of the Auxiliary Telescopes (ATs) of ESO's Very Large Telescope (VLT). Such dark and star-studded skies are typical of the VLT’s location in the Chilean Atacama Desert, which offers spectacular views such as this night after night for all of the site’s astronomers, visitors, and staff to enjoy.

The VLT is made up of four large Unit Telescopes, and four smaller and movable Auxiliary Telescopes (one of which is shown here). These eight telescopes observe the cosmos both individually and as a team from various orientations and positions, allowing astronomers to study all manner of cosmic objects and phenomena in greater detail than ever before.

The array has stimulated a new age of discoveries, with several notable scientific firsts — including the first image of a planet orbiting another star (known as an extrasolar planet or exoplanet), and tracking individual stars moving around the supermassive black hole at the centre of the Milky Way (an object named Sagittarius A*).

Image Credit: ESA/Hubble & NASA

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The subject of this Picture of the Week, a spiral galaxy named NGC 1589, was once the scene of a violent bout of cosmic hunger pangs; as astronomers looked on, a poor, hapless star was torn apart and devoured by the ravenous supermassive black hole at the centre of the galaxy.

The astronomers are now using the NASA/ESA Hubble Space Telescope to test this interpretation. Hubble has observed such events before so the scientists are confident that Hubble will be able to provide smoking gun evidence in the form of stellar debris that was ejected during the disruption event.

Messier 35 (M35) is a large open star cluster located in the northern constellation Gemini. The cluster consists of several hundred stars, of which 120 are brighter than magnitude 13. The cluster has an apparent magnitude of 5.3 and lies at an approximate distance of 2,800 light years from Earth. The estimated age of M35 is about 110 million years. The hottest blue/white main sequence stars in the cluster have the spectral classification B3. M35 also contains more evolved stars, including several orange and yellow giants. The cluster is approaching us at 5 km/s. Another open cluster, NGC2158, lies about 15 arc minutes to the southeast of M35. NGC2158 has a visual magnitude of 8.6 and occupies an area of 5 arc minutes. It is considerably older, more compact and contains more stars. It is also more than five times more distant than M35 and the two clusters are not physically related.

The gravitational warping of distant starlight seen here is caused by a galaxy cluster located nearly 4 billion light-years away, visible at the center of this image. Clusters of galaxies are the largest gravitationally bound systems in the universe, and their abundance and distribution can reveal information about how the universe expanded and how its structure formed and evolved. A team using the South Pole Telescope recently conducted a new survey — the SPTpol Extended Cluster Survey — of 2,770 square degrees of sky, hunting for the signatures that galaxy clusters imprint on the cosmic microwave background spectrum. In a publication led by Lindsey Bleem (Argonne National Laboratory, University of Chicago), the team describes the result: the discovery of 266 cluster candidates, 244 of which have already been confirmed visually via archival and follow-up observations like the one shown above (taken with the PISCO imager on the 6.5 m Magellan/Clay telescope at Las Campanas Observatory in Chile).

• Astrophysical Journal Supplement 247(1):25 (2020 Mar) DOI: 10.3847/1538-4365/ab6993
• arXiv.org > astro-ph > arXiv:1910.04121 > 09 Oct 2019 (v1), 13 Dec 2019 (v2)