Found Images: 2015 August

[geckzilla]

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Have you seen a great image or video somewhere that you think would make a great APOD? Nominate it for APOD! Please post as much information here as you have about the image/video with a link to any source(s) for it you know of here, and the editors will take a look.

When posting the image itself, please do not post anything larger than a thumbnail here; please honor the copyright holder's copyright.

Please keep hotlinked images under 400K.

Thank you!

[bystander]

White Dwarf Resurrection
ESO Picture of the Week | 2015 Aug 03

[img3="Credit: ESO, VLT, FORS"]http://cdn.eso.org/images/screen/potw1531a.jpg[/img3][hr][/hr]

The bright star in the centre of this image is not the star of this show. At the bottom centre is a rather unremarkable smudge of red which is in fact a rare and valuable object.

First discovered by amateur Japanese astronomer, Yukio Sakurai, in 1996, and noted as a nova-like object, Sakurai’s discovery turned out to be far more interesting than the supernova he initially supposed it to be.

The object is actually a small white dwarf star undergoing a helium flash — one of only a handful of examples of such an event ever witnessed by astronomers.

Normally, the white dwarf stage is the last in the life cycle of a low-mass star. In some cases, however, the star reignites in a helium flash and expands to return to a red giant state, ejecting huge amounts of gas and dust in the process, before once again shrinking to become a white dwarf.

It is a dramatic and short-lived series of events, and Sakurai’s Object has allowed astronomers a very rare opportunity to study the events in real time. The white dwarf emits sufficient ultraviolet radiation to illuminate the gas it has expelled, which can just be seen in this image as the ring of red material.

This image was taken using the FORS instrument, mounted on ESO’s Very Large Telescope.

[bystander]

Little Gem Nebula (NGC 6818)
ESA Hubble Picture of the Week | 2015 Aug 03

[img3="Credit: ESA/Hubble and NASA
Acknowledgement: Judy Schmidt (geckzilla.com)"]http://cdn.spacetelescope.org/archives/ ... w1531a.jpg[/img3][hr][/hr]

This colourful bubble is a planetary nebula called NGC 6818, also known as the Little Gem Nebula. It is located in the constellation of Sagittarius (The Archer), roughly 6000 light-years away from us. The rich glow of the cloud is just over half a light-year across — humongous compared to its tiny central star — but still a little gem on a cosmic scale.

When stars like the Sun enter retirement, they shed their outer layers into space to create glowing clouds of gas called planetary nebulae. This ejection of mass is uneven, and planetary nebulae can have very complex shapes. NGC 6818 shows knotty filament-like structures and distinct layers of material, with a bright and enclosed central bubble surrounded by a larger, more diffuse cloud.

Scientists believe that the stellar wind from the central star propels the outflowing material, sculpting the elongated shape of NGC 6818. As this fast wind smashes through the slower-moving cloud it creates particularly bright blowouts at the bubble’s outer layers.

Hubble previously imaged this nebula back in 1997 with its Wide Field Planetary Camera 2, using a mix of filters that highlighted emission from ionised oxygen and hydrogen (opo9811h). This image, while from the same camera, uses different filters to reveal a different view of the nebula. A version of the image was submitted to the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

[starsurfer]

White Dwarf Resurrection
ESO Picture of the Week | 2015 Aug 03

[img3="Credit: ESO, VLT, FORS"]http://cdn.eso.org/images/screen/potw1531a.jpg[/img3][hr][/hr]

The bright star in the centre of this image is not the star of this show. At the bottom centre is a rather unremarkable smudge of red which is in fact a rare and valuable object.

First discovered by amateur Japanese astronomer, Yukio Sakurai, in 1996, and noted as a nova-like object, Sakurai’s discovery turned out to be far more interesting than the supernova he initially supposed it to be.

The object is actually a small white dwarf star undergoing a helium flash — one of only a handful of examples of such an event ever witnessed by astronomers.

Normally, the white dwarf stage is the last in the life cycle of a low-mass star. In some cases, however, the star reignites in a helium flash and expands to return to a red giant state, ejecting huge amounts of gas and dust in the process, before once again shrinking to become a white dwarf.

It is a dramatic and short-lived series of events, and Sakurai’s Object has allowed astronomers a very rare opportunity to study the events in real time. The white dwarf emits sufficient ultraviolet radiation to illuminate the gas it has expelled, which can just be seen in this image as the ring of red material.

This image was taken using the FORS instrument, mounted on ESO’s Very Large Telescope.

That's some great two posts about stellar evolution! Sakurai's Object is indeed very mysterious and rare, the phenomenon of helium flash has been observed in "born again" planetary nebulae, most notably Abell 78 and Abell 30. It is interesting in that it's evolution can be observed over a period of many years, reminiscent of the expansion of the knots in the nova shell surrounding GK Persei. On another note, there is evidence that the shaping of planetary nebulae occurs in the proto-planetary nebula phase, an area that will be greatly expanded upon by future observatories such as the James Webb Space Telescope and the Thirty Metre Telescope.

[starsurfer]

IC 1396 and Sh2-129
http://www.capella-observatory.com/Imag ... ithOu4.htm
Copyright: Stefan Binnewies and Rainer Sparenberg

http://www.capella-observatory.com/Imag ... h2-129.htm

Click to view full size image 1 or image 2

[starsurfer]

M33
http://www.martinpughastrophotography.id.au
Copyright: Martin Pugh

[bystander]

The Ghost of a Dying Star (ESO 378-1)
ESO Photo Release | VLT | 2015 Aug 05

This extraordinary bubble, glowing like the ghost of a star in the haunting darkness of space, may appear supernatural and mysterious, but it is a familiar astronomical object: a planetary nebula, the remnants of a dying star. This is the best view of the little-known object ESO 378-1 yet obtained and was captured by ESO's Very Large Telescope in northern Chile.

[img3="Credit: ESO/VLT"]http://cdn.eso.org/images/screen/eso1532a.jpg[/img3][hr][/hr]

Nicknamed the Southern Owl Nebula, this shimmering orb is a planetary nebula with a diameter of almost four light-years. Its informal name relates to its visual cousin in the northern hemisphere, the Owl Nebula. ESO 378-1 [1], which is also catalogued as PN K1-22 and PN G283.6+25.3, is located in the constellation of Hydra (The Female Water Snake).

Like all planetary nebulae, ESO 378-1 is a relatively short-lived phenomenon, lasting only a few tens of thousands of years, compared to a typical stellar lifetime of several billion years [2].

Planetary nebulae are created by the ejected and expanding gas of dying stars. Although they are brilliant and intriguing objects in the initial stages of formation, these bubbles fade away as their constituent gas moves away and the central stars grow dimmer.

For a planetary nebula to form, the aging star must have a mass less than about eight times that of the Sun. Stars that are heavier than this limit will end their lives in dramatic fashion as supernova explosions.

As these less massive stars grow old they start to lose their outer layers of gas to stellar winds. After most of these outer layers have dissipated, the remaining hot stellar core starts to emit ultraviolet radiation which then ionises the surrounding gas. This ionisation causes the expanding shell of ghostly gas to begin to glow in bright colours. ...

[starsurfer]

M81
http://www.imagingdeepsky.com/Galaxies/M81/M81.htm
Copyright: Ken Crawford

[starsurfer]

NGC 2451 and NGC 2477
http://www.astro-austral.cl/imagenes/st ... 7/info.htm
Copyright: José Joaquín Pérez

NGC 2451 is the large bright cluster on the right while NGC 2477 is the smaller one on the left. The nebulosity in the area belongs to the Gum Nebula.

[starsurfer]

Vela Supernova Remnant
http://www.astrobin.com/162764/
Copyright: John Gleason

[starsurfer]

NGC 6752
http://www.chart32.de/index.php/component/k2/item/143
Copyright: CHART32
Processing: Bernd Flach-Wilken

[swag72]

Meteorite explosion
https://flic.kr/p/wFUKGQ
Copyright Andre Van Der Hoeven

Meteorite explosion by Andre van der Hoeven, on Flickr

http://asterisk.apod.com/viewtopic.php?p=246643#p246643

[starsurfer]

Eskimo Nebula (NGC 2392)
http://www.caelumobservatory.com/gallery/n2392.shtml
Copyright: Adam Block/Mount Lemmon SkyCenter/University of Arizona

[bystander]

A Mess of Stars (NGC 428)
ESA Hubble Picture of the Week | 2015 Aug 10

[img3="Credit: ESA/Hubble, NASA, and S. Smartt (Queen's University Belfast)
Acknowledgements: Nick Rose and Flickr user penninecloud"]http://cdn.spacetelescope.org/archives/ ... w1532a.jpg[/img3][hr][/hr]

Bursts of pink and red, dark lanes of mottled cosmic dust, and a bright scattering of stars — this NASA/ESA Hubble Space Telescope image shows part of a messy barred spiral galaxy known as NGC 428. It lies approximately 48 million light-years away from Earth in the constellation of Cetus (The Sea Monster).

Although a spiral shape is still just about visible in this close-up shot, overall NGC 428’s spiral structure appears to be quite distorted and warped, thought to be a result of a collision between two galaxies. There also appears to be a substantial amount of star formation occurring within NGC 428 — another telltale sign of a merger. When galaxies collide their clouds of gas can merge, creating intense shocks and hot pockets of gas and often triggering new waves of star formation.

NGC 428 was discovered by William Herschel in December 1786. More recently a type Ia supernova designated SN2013ct was discovered within the galaxy by Stuart Parker of the BOSS (Backyard Observatory Supernova Search) project in Australia and New Zealand, although it is unfortunately not visible in this image.

This image was captured by Hubble’s Advanced Camera for Surveys (ACS) and Wide Field and Planetary Camera 2 (WFPC2). ...

[Ann]

On this page, NGC 428 is described as "spectacularly blue". But in the picture that bystander posted, NGC 428 looks all but perfectly non-blue. An explanation can be found in the filters used and how they were mapped for the ESA/Hubble, NASA, and S. Smart picture. According to this page, a 450 nm filter, corresponding to about this color, was mapped both as blue and as green. But a 606 nm filter, corresponding to about this color, was also mapped as green.

So there is a lot of mapped green color in that picture, but little blue.

It should be pointed out that not all mergers lead to a lot of star formation, which can be seen on the SDSS page that I previously linked to. But NGC 428 is vigorously starforming indeed, and it is also spectacularly blue.

Ann

[bystander]

...
According to this page, a 450 nm filter, corresponding to about this color, was mapped both as blue and as green. But a 606 nm filter, corresponding to about this color, was also mapped as green.

So there is a lot of mapped green color in that picture, but little blue. ...

Green is simulated from the red (orange?) and blue channels.

[starsurfer]

NGC 1999
http://www.astroimager.net/Page-RHA-CCD-354.html
Copyright: Jim Janusz

[starsurfer]

IC 1284
http://astrophotography.aa6g.org/Astrop ... f8300.html
Copyright: Chuck Vaughn

[starsurfer]

NGC 6164-5
http://www.robgendlerastropics.com/NGC6164-B.html
Copyright: Robert Gendler, Don Goldman and Steve Crouch

This nebula is not a planetary nebula or a Wolf Rayet nebula, it is a rare ejecta nebula around an O-type star.

[starsurfer]

NGC 2163
http://afesan.es/Deepspace/slides/NGC%2 ... C1578.html
Copyright: Antonio Sánchez

[observingspace]

Orion & red sprites photographed from the ISS
Copyright: Expedition 44 Crew, International Space Station

http://eol.jsc.nasa.gov/SearchPhotos/ph ... rame=45576
http://eol.jsc.nasa.gov/DatabaseImages/ ... -45576.JPG

http://www.observingspace.com/623/orion ... m-the-iss/
http://i.imgur.com/yUSPxJB.jpg



Note: The above image is cropped to make it easier to see Orion and the sprites.

[starsurfer]

M15
http://bf-astro.com/m15/m15-2014.htm
Copyright: Bob Franke

[bystander]

A Cosmic Rainbow in Ultra HD
ESO Picture of the Week | 2015 Aug 17

[img3="Credit: ESO/Babak Tafreshi (TWAN)"]http://cdn.eso.org/images/screen/potw1533a.jpg[/img3][hr][/hr]

In this panoramic image taken by Babak Tafreshi — a member of the ESO Ultra HD Expedition team — the ALMA Observatory’s antennas appear to take in the sight of the Milky Way, arching like a galactic rainbow of dust and stars over the Chajnantor Plateau in the Chilean Andes.

Located 5000 metres above sea level, the Chajnantor Plateau serves as an ideal hunting ground for ALMA. The array uses observations at the millimetre and submillimetre wavelengths to explore the coldest parts of the Universe. The superb aridness of the plateau means that far less submillimetre radiation is absorbed and attenuated by water vapour than would be the case closer to sea level.

As ALMA seeks to capture the secrets of the Universe, Babak Tafreshi and his fellow team members seek to capture the beauty and grandeur of ESO’s observatories and their unusual surroundings. Comprising four celebrated astrophotographers and ESO Photo Ambassadors, the ESO Ultra HD expedition aimed to raise public awareness of the ongoing work in Chile through astonishing Ultra HD photos and videos.

[bystander]

A Cosmic Couple (WR 124, M1-67)
ESA Hubble Picture of the Week | 2015 Aug 17

[img3="Credit: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt"]http://cdn.spacetelescope.org/archives/ ... w1533a.jpg[/img3][hr][/hr]

Here we see the spectacular cosmic pairing of the star Hen 2-427 — more commonly known as WR 124 — and the nebula M1-67 which surrounds it. Both objects, captured here by the NASA/ESA Hubble Space Telescope are found in the constellation of Sagittarius and lie 15 000 light-years away.

The star Hen 2-427 shines brightly at the very centre of this explosive image and around the hot clumps of gas are ejected into space at over 150 000 kilometres per hour.

Hen 2-427 is a Wolf–Rayet star, named after the astronomers Charles Wolf and Georges Rayet. Wolf–Rayet are super-hot stars characterised by a fierce ejection of mass.

The nebula M1-67 is estimated to be no more than 10 000 years old — just a baby in astronomical terms — but what a beautiful and magnificent sight it makes.

A version of this image was released in 1998, but has now been re-reduced with the latest software.

[geckzilla]

That's kinda strange. ESA's version clips off the bottom dimmest portion of the nebula, making it hard to discern the faintest aspects of it. For comparison: