Starship Asterisk*

starsurfer wrote: ↑Sat Mar 30, 2019 6:39 pm NGC 299
https://www.spacetelescope.org/images/potw1642a/
Copyright: ESA/Hubble & NASA

Click to view full size image

Californian wrote: ↑Thu Mar 28, 2019 2:15 am https://www.jpl.nasa.gov/news/news.php?feature=7359
NASA/JPL-Caltech

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

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This star-studded image shows us a portion of Messier 11, an open star cluster in the southern constellation of Scutum (The Shield). Messier 11 is also known as the Wild Duck Cluster, as its brightest stars form a “V” shape that somewhat resembles a flock of ducks in flight.

Messier 11 is one of the richest and most compact open clusters currently known. By investigating the brightest, hottest main sequence stars in the cluster astronomers estimate that it formed roughly 220 million years ago. Open clusters tend to contain fewer and younger stars than their more compact globular cousins, and Messier 11 is no exception: at its centre lie many blue stars, the hottest and youngest of the cluster’s few thousand stellar residents.

The lifespans of open clusters are also relatively short compared to those of globular ones; stars in open clusters are spread further apart and are thus not as strongly bound to each other by gravity, causing them to be more easily and quickly drawn away by stronger gravitational forces. As a result Messier 11 is likely to disperse in a few million years as its members are ejected one by one, pulled away by other celestial objects in the vicinity.

Credit: Petr Horálek/ESO

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This astonishing image clearly illustrates why astronomical observatories are usually built in remote, and often inhospitable, places. At ESO’s La Silla Observatory in Chile, the sky is so clear and untroubled by man-made sources of light that it appears as if a brightly-coloured celestial firework display is in progress!

This photograph, taken by ESO Photo Ambassador Petr Horálek, has been digitally projected to show as much of the sky as possible. This is why the roads leading to ESO’s 3.58-metre New Technology Telescope (left) and 3.6-metre telescope (right) appear distorted, and the bright river of light that is the Milky Way seems to curve across the sky, stretching from horizon to horizon.

Cosmic fireworks aside, this scene is filled with awe-inspiring phenomena. The pink “fireworks” themselves are actually large accumulations of glowing gas known as nebulae. To the right of the Milky Way lie the Magellanic Clouds, two nearby dwarf galaxies. Rising up from the horizon on the left of the image is a pale, white-ish column of light. This is the glow of Zodiacal light, caused by sunlight scattering off dust particles in the Solar System. At the centre of the image is another glowing region — green this time. This is airglow, a phenomenon that occurs high up in the Earth’s atmosphere, where a variety of processes create ghostly coloured light.

Credit: NASA/ESA/Hubble, J Blakenslee, P Cote et al

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This fuzzy orb of light is a giant elliptical galaxy filled with an incredible 200 billion stars. Unlike spiral galaxies, which have a well-defined structure and boast picturesque spiral arms, elliptical galaxies appear fairly smooth and featureless. This is likely why this galaxy, named Messier 49, was discovered by French astronomer Charles Messier in 1771. At a distance of 56 million light-years, and measuring 157 000 light-years across, M49 was the first member of the Virgo Cluster of galaxies to be discovered, and it is more luminous than any other galaxy at its distance or nearer.

Elliptical galaxies tend to contain a larger portion of older stars than spiral galaxies and also lack young blue stars. Messier 49 itself is very yellow, which indicates that the stars within it are mostly older and redder than the Sun. In fact, the last major episode of star formation was about six billion years ago — before the Sun was even born!

Messier 49 is also rich in globular clusters; it hosts about 6000, a number that dwarfs the 150 found in and around the Milky Way. On average, these clusters are 10 billion years old. Messier 49 is also known to host a supermassive black hole at its centre with the mass of more than 500 million Suns, identifiable by the X-rays pouring out from the heart of the galaxy (as this Hubble image comprises infrared observations, these X-rays are not visible here).

Credit: ESO Cosmic Gems

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It’s impossible to miss the star in this ESO Picture of the Week — beaming proudly from the centre of the frame is the massive multiple star system Tau Canis Majoris, the brightest member of the Tau Canis Majoris Cluster (NGC 2362) in the eponymous constellation of Canis Major (The Great Dog). Tau Canis Majoris aside, the cluster is populated by many young and less attention-seeking stars that are only four or five million years old, all just beginning their cosmic lifetimes.

The Tau Canis Majoris Cluster is an open cluster — a group of stars born from the same molecular cloud. This means that all of the cluster’s inhabitants share a common chemical composition and are loosely bound together by gravity. Having been born together, they make an ideal stellar laboratory to test theories of stellar evolution, the chain of events that leads from a star’s birth in a cool, dense cloud of gas through to its eventual death.

Though the stars in this image were all created at the same time, their various different masses mean they will lead very different lives. As Tau Canis Majoris is one of the most massive and short-lived types of star, it will burn through its nuclear fuel long before its smaller companions, which will keep on shining for billions of years.

This image was created as part of the ESO Cosmic Gems programme, an outreach initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. All data collected may also be suitable for scientific purposes, and are made available to astronomers through ESO’s science archive.