Starship Asterisk*

Credit: ESA/Hubble & NASA, J. Lee, PHANGS-HST Team

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This NASA/ESA Hubble Space Telescope Picture of the Week features NGC 4826 — a spiral galaxy located 17 million light-years away in the constellation of Coma Berenices (Berenice’s Hair). This galaxy is often referred to as the “Black Eye”, or “Evil Eye”, galaxy because of the dark band of dust that sweeps across one side of its bright nucleus.

NGC4826 is known by astronomers for its strange internal motion. The gas in the outer regions of this galaxy and the gas in its inner regions are rotating in opposite directions, which might be related to a recent merger. New stars are forming in the region where the counter rotating gases collide.

This galaxy was first discovered in 1779 by the English astronomer Edward Pigott.

Image Credit: ESO/Ginski et al.

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Appearing as a bird in flight, with wings outstretched in the expanse of space, SU Aur, a star much younger and more massive than the Sun, is surrounded by a giant planet-forming disc. This image, captured by the SPHERE instrument on ESO’s Very Large Telescope (VLT), shows the disc around SU Aur in unprecedented detail, including the long dust trails connected to it. The star itself is obscured by the instrument’s coronagraph, a device that blocks the light from the central star to allow the less bright features around it to stand out.

The dust trails are composed of material from an encompassing nebula flowing into the disc. This nebula is likely the outcome of a collision between the star and a huge cloud of gas and dust, resulting in the unique shape of this planet-forming disc and the surrounding dust structure. A new study of SU Aur, which used the VLT and data from other telescopes, including the Atacama Large Millimeter/Submillimeter Array (ALMA), showed that the nebula is still feeding material to the planet-forming disc. These new observations highlight how complex planet-forming discs can be.

Image Credit: ESA/Hubble & NASA, B. Nisini

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Herbig-Haro objects are some of the rarer sights in the night sky, taking the form of thin spindly jets of matter floating amongst the surrounding gas and stars. The two Herbig-Haro objects catalogued as HH46 and HH47, seen in this image taken with the NASA/ESA Hubble Space Telescope, were spotted in the constellation of Vela (The Sails), at a distance of over 1400 light-years from Earth. Prior to its discovery in 1977 by the American astronomer R. D. Schwartz, the exact mechanism by which these multi-coloured objects formed was unknown.

Before 1997 it was theorised by Schwartz and others that the objects could be a type of reflection nebula, or a type of shock wave formed from the gas emitted from a star interacting with the surrounding matter. The mystery was finally solved when a protostar, unseen in this image, was discovered at the centre of the long jets of matter. The outflows of matter, some 10 light-years across, were ejected from the newly born star and violently propelled outwards at speeds of over 150 kilometres per second. Upon reaching the surrounding gas, the collision created the bright shock waves seen here.

Image Credit: ESO/Petr Horálek

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It may not be as famous as Halley’s Comet, but Comet 252P/LINEAR can still put on a show! In late March 2016, the comet made one of the closest approaches to Earth of all comets in history — just over 5.3 million kilometres distant, compared to Halley’s closest approach of 87 million kilometres. The light of Comet 252P/LINEAR is not elongated in a classic tail, but instead appears as a soft round glow, tinged green due to molecules of diatomic carbon fluorescing in the sunlight. This image from April 2016 captures the distinctly green comet: you can spot it just above the Milky Way, between the galaxy’s starry arch and the Very Large Telescope (VLT) Unit Telescope at the centre of the frame.

ESO’s VLT is located at the Paranal Observatory in Chile, an ideal location for comet-spotting. Paranal is one of the most spectacular observatories in the world, situated in the seemingly infinite Atacama Desert under the dark skies of the southern hemisphere. Comets are not the only treasure visible in these skies: the Milky Way puts on its nightly spectacle, its rich interstellar clouds bejewelled with stars, the diverse colours of natural airglow shine near the horizon, and high above sit two planets. In this sweeping panorama, they form a slightly distorted triangle that includes the red supergiant star Antares, with the intense shine of Mars to the left and the whitish glow of the gas giant Saturn beneath.