Starship Asterisk*

bystander wrote:The Calabash Clash
ESA Hubble Picture of the Week | 2017 Jan 30

[img3="Credit: ESA/Hubble, NASA
Acknowledgement: Judy Schmidt"]https://cdn.spacetelescope.org/archives ... w1705a.jpg[/img3][hr][/hr]

The Calabash Nebula, pictured here — which has the technical name OH 231.8+04.2 — is a spectacular example of the death of a low-mass star like the Sun.

Eckhart Spalding of astrobites.org wrote about star formation in the Orion Nebula:
Surprisingly, the mass function corresponding to an age of 2-5 million years has two distinct peaks (Fig. 2)! If the Orion Nebula is indeed that old (some think it might actually be younger) and if the isochrones are accurate (isochrones are debatable at the lowest masses), then the Orion Nebular Cloud seems to be preferentially producing objects at around 0.25 and 0.025 solar masses. These correspond to low-mass stars and brown dwarfs.

[img3="Credit: ESA/Hubble, NASA
Acknowledgement: Judy Schmidt"]https://cdn.spacetelescope.org/archives ... w1705a.jpg[/img3][hr][/hr]

The Calabash Nebula, pictured here — which has the technical name OH 231.8+04.2 — is a spectacular example of the death of a low-mass star like the Sun. This image taken by the NASA/ESA Hubble Space Telescope shows the star going through a rapid transformation from a red giant to a planetary nebula, during which it blows its outer layers of gas and dust out into the surrounding space. The recently ejected material is spat out in opposite directions with immense speed — the gas shown in yellow is moving close to a million kilometres an hour.

Astronomers rarely capture a star in this phase of its evolution because it occurs within the blink of an eye — in astronomical terms. Over the next thousand years the nebula is expected to evolve into a fully fledged planetary nebula.

The nebula is also known as the Rotten Egg Nebula because it contains a lot of sulphur, an element that, when combined with other elements, smells like a rotten egg — but luckily, it resides over 5000 light-years away in the constellation of Puppis (The Poop deck).

[img3="Credit: ESO/Babak Tafreshi (TWAN)"]https://cdn.eso.org/images/thumb700x/potw1705a.jpg[/img3][hr][/hr]

This picture shows the ESO 3.6-metre telescope, located at the La Silla Observatory in Chile. The night sky overhead is dominated by the Moon, which shines so brightly that illuminates the scene fully.

The most dominant feature of this image is the red rock in the foreground. It is marked with prehistoric engravings — signatures from the region’s past. Several such engravings can be found around La Silla, but this particular rock is part of the richest site in the area.

A complete photographic and topographic survey of these engravings was carried out in 1990. The carved rocks predominantly depict scenes involving men and animals, as well as mysterious geometrical figures. It is believed that these engravings originate from the El Molle complex — the first culture in the north of Chile. Geologists believe that the first millennium of our era experienced a lot more rainfall than it does today, allowing parts of the Atacama Desert to support various civilised cultures.

starsurfer wrote:vdB38 and Sh2-265
http://www.atacama-photographic-observa ... .php?id=61
Copyright: Thierry Demange, Richard Galli and Thomas Petit
vdb38.jpg

bystander wrote:Starbirth with a Chance of Winds?
ESA Hubble Picture of the Week | 2017 Jan 23

[img3="Credit: ESA/Hubble & NASA"]https://cdn.spacetelescope.org/archives ... w1704a.jpg[/img3][hr][/hr]

The lesser-known constellation of Canes Venatici (The Hunting Dogs), is home to a variety of deep-sky objects — including this beautiful galaxy, known as NGC 4861. Astronomers are still debating on how to classify it: While its physical properties — such as mass, size and rotational velocity — indicate it to be a spiral galaxy, its appearance looks more like a comet with its dense, luminous “head” and dimmer “tail” trailing behind. Features more fitting with a dwarf irregular galaxy.

Although small and messy, galaxies like NGC 4861 provide astronomers with interesting opportunities for study. Small galaxies have lower gravitational potentials, which simply means that it takes less energy to move stuff about inside them than it does in other galaxies. As a result, moving in, around, and through such a tiny galaxy is quite easy to do, making them far more likely to be suffused with streams and outflows of speedy charged particles known as galactic winds, which can flood such galaxies with little effort.

These galactic winds can be powered by the ongoing process of star formation, which involves huge amounts of energy. New stars are springing into life within the bright, colourful ‘head’ of NGC 4861 and ejecting streams of high-speed particles as they do so, which flood outwards to join the wider galactic wind. While NGC 4861 would be a perfect candidate to study such winds, recent studies did not find any galactic winds in it.

Ann wrote:

starsurfer wrote:Fornax Dwarf
http://www.glitteringlights.com/Images/ ... CrGHQTn/X3
Copyright: Marco Lorenzi

Click to view full size image

This is quite interesting, too. The Fornax Dwarf is a really puny galaxy without any trace of star formation. The galaxy's absolute luminosity, according to Guide and Principal Galaxy Catalog, is −11.139. According to Wikipedia, there are a lot of stars that are brighter than that in their own right - admittedly we are talking about bolometric (total) luminosity for the stars, whereas the −11.139 mag luminosity for the Fornax Dwarf galaxy would be V (or more likely, B) luminosity. But there are some stars whose luminosity peaks in or near the optical part of the spectrum, such as V4998 Sagittarii, and they are still more luminous in their own right than all the stars in the Fornax Dwarf. The mind boggles.

The Fornax Dwarf, being utterly devoid of star formation, is quite red, with an effective B-V index of 0.840. There is a sixth magnitude G5-type star apparently located next to it, Lambda-2 Sagittarii, and it looks blue compared with the galaxy, even though it is almost exactly the same color as the Sun.

And by the way, there is a whitish object in the upper part of the galaxy that is a globular cluster!

Ann

[img3="Credit: ESA/Hubble & NASA"]https://cdn.spacetelescope.org/archives ... w1704a.jpg[/img3][hr][/hr]

The lesser-known constellation of Canes Venatici (The Hunting Dogs), is home to a variety of deep-sky objects — including this beautiful galaxy, known as NGC 4861. Astronomers are still debating on how to classify it: While its physical properties — such as mass, size and rotational velocity — indicate it to be a spiral galaxy, its appearance looks more like a comet with its dense, luminous “head” and dimmer “tail” trailing behind. Features more fitting with a dwarf irregular galaxy.

Although small and messy, galaxies like NGC 4861 provide astronomers with interesting opportunities for study. Small galaxies have lower gravitational potentials, which simply means that it takes less energy to move stuff about inside them than it does in other galaxies. As a result, moving in, around, and through such a tiny galaxy is quite easy to do, making them far more likely to be suffused with streams and outflows of speedy charged particles known as galactic winds, which can flood such galaxies with little effort.

These galactic winds can be powered by the ongoing process of star formation, which involves huge amounts of energy. New stars are springing into life within the bright, colourful ‘head’ of NGC 4861 and ejecting streams of high-speed particles as they do so, which flood outwards to join the wider galactic wind. While NGC 4861 would be a perfect candidate to study such winds, recent studies did not find any galactic winds in it.

starsurfer wrote:Fornax Dwarf
http://www.glitteringlights.com/Images/ ... CrGHQTn/X3
Copyright: Marco Lorenzi

Click to view full size image

starsurfer wrote:IC 4662
http://www.chart32.de/index.php/component/k2/item/174
Copyright: CHART32
Processing: Bernd Flach-Wilken

Click to view full size image