Starship Asterisk*

[img3="Credit: ALMA (ESO/NAOJ/NRAO); C. Brogan, B. Saxton (NRAO/AUI/NSF)"]https://cdn.eso.org/images/screen/potw1712a.jpg[/img3][hr][/hr]

This image, taken by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, shows glowing dust inside the protocluster NGC 6334I. Studying this star-forming cloud in the Cat’s Paw Nebula (NGC 6334) with both ALMA and the Submillimeter Array (SMA) in Hawaii astronomers could see that something dramatic had taken place, completely changing a stellar nursery over a surprisingly short period of time.

It is known that young stars form inside protoclusters when pockets of gas become so dense that they begin to collapse under their own gravity. Over time, discs of dust and gas form around these nascent stars and funnel material onto their surfaces helping them grow.

However, this new image from ALMA shows a massive protostar, nestled deep within this dust-filled stellar nursery, that is undergoing an intense growth spurt, most likely triggered by an avalanche of gas falling onto its surface. This new material feeding it is causing the protostar to shine nearly 100 times brighter than before.The discovery of this outburst supports the theory that young stars can undergo intense growth spurts that reshape their surroundings.

[img3="Credit: ESA/Hubble & NASA"]https://cdn.spacetelescope.org/archives ... w1712a.jpg[/img3][hr][/hr]

Some galaxies are harder to classify than others. Here, Hubble’s trusty Wide Field Camera 3 (WFC3) has captured a striking view of two interacting galaxies located some 60 million light-years away in the constellation of Leo (The Lion). The more diffuse and patchy blue glow covering the right side of the frame is known as NGC 3447 — sometimes NGC 3447B for clarity, as the name NGC 3447 can apply to the overall duo. The smaller clump to the upper left is known as NGC 3447A.

The trouble with space is that it is, to state the obvious, really, really big. Astronomers have for hundreds of years been discovering and naming galaxies, stars, cosmic clouds and more. Unifying and regulating the conventions and classifications for everything ever observed is very difficult, especially when you get an ambiguous object like NGC 3447, which stubbornly defies easy categorisation.

Overall, we know NGC 3447 comprises a couple of interacting galaxies, but we’re unsure what each looked like before they began to tear one another apart. The two sit so close that they are strongly influenced and distorted by the gravitational forces between them, causing the galaxies to twist themselves into the unusual and unique shapes seen here. NGC 3447A appears to display the remnants of a central bar structure and some disrupted spiral arms, both properties characteristic of certain spiral galaxies. Some identify NGC 3447B as a former spiral galaxy, while others categorise it as being an irregular galaxy.

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ESO's Very Large Telescope (VLT) looks more like a very small telescope in this image! From this perspective, it is difficult to make out the silhouettes of the VLT’s four 8.2-metre Unit Telescopes, which sit atop Cerro Paranal in the Chilean Atacama Desert.

The VLT’s location was very carefully selected. It is vital for the site to be as dry as possible, as water vapour can absorb infrared light and degrade observations. In order to reduce the effects of Earth’s atmosphere as far as possible, the VLT is at 2600 metres above sea level, minimising the amount of atmosphere sitting between it and the stars.

Due to its remote location, Paranal manages to be mostly undisturbed and light-free. Even the winding roads that lead through the Atacama Desert to the observation site are dimly lit to avoid unnecessary light pollution.

In this image, a trail of stars cuts across the the night sky like smoke rising from a celestial chimney. This is our home galaxy, the Milky Way. Towards the top of the image you can see a brighter and wider section — this is the star-filled galactic bulge, which sits at the heart of the Milky Way.

[img3="Credit: ESA/Hubble, NASA"]https://cdn.spacetelescope.org/archives ... w1713a.jpg[/img3][hr][/hr]

Some astronomical objects have endearing or quirky nicknames, inspired by mythology or their own appearance. Take, for example, the constellation of Orion (The Hunter), the Sombrero Galaxy, the Horsehead Nebula, or even the Milky Way. However, the vast majority of cosmic objects appear in astronomical catalogues, and are given rather less poetic names based on the order of their discovery.

Two galaxies are clearly visible in this Hubble image, the larger of which is NGC 4424. This galaxy is catalogued in the New General Catalogue of Nebulae and Clusters of Stars (NGC), which was compiled in 1888. The NGC is one of the largest astronomical catalogues, which is why so many Hubble Pictures of the Week feature NGC objects. In total there are 7840 entries in the catalogue and they are also generally the larger, brighter, and more eye-catching objects in the night sky, and hence the ones more easily spotted by early stargazers.

The smaller, flatter, bright galaxy sitting just below NGC 4424 is named LEDA 213994. The Lyon-Meudon Extragalactic Database (LEDA) is far more modern than the NGC. Created in 1983 at the Lyon Observatory it contains millions of objects. However, many NGC objects still go by their initial names simply because they were christened within the NGC first. No astronomer can resist a good acronym, and “LEDA” is more appealing than “the LMED”, perhaps thanks to the old astronomical affinity with mythology when it comes to naming things: Leda was a princess in Ancient Greek mythology.