Found images: 2017 January

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geckzilla
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Re: Found images: 2017 January

Postby geckzilla » Mon Jan 16, 2017 7:54 pm

bystander wrote:A Slice of Sagittarius
ESA Hubble Picture of the Week | 2017 Jan 16

This stunning image, captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS), shows part of the sky in the constellation of Sagittarius (The Archer). The region is rendered in exquisite detail — deep red and bright blue stars are scattered across the frame, set against a background of thousands of more distant stars and galaxies. Two features are particularly striking: the colours of the stars, and the dramatic crosses that burst from the centres of the brightest bodies.

While some of the colours in this frame have been enhanced and tweaked during the process of creating the image from the observational data, different stars do indeed glow in different colours. Stars differ in colour according to their surface temperature: very hot stars are blue or white, while cooler stars are redder. They may be cooler because they are smaller, or because they are very old and have entered the red giant phase, when an old star expands and cools dramatically as its core collapses.

The crosses are nothing to do with the stars themselves, and, because Hubble orbits above Earth’s atmosphere, nor are they due to any kind of atmospheric disturbance. They are actually known as diffraction spikes, and are caused by the structure of the telescope itself. Like all big modern telescopes, Hubble uses mirrors to capture light and form images. Its secondary mirror is supported by struts, called telescope spiders, arranged in a cross formation, and they diffract the incoming light. Diffraction is the slight bending of light as it passes near the edge of an object. Every cross in this image is due to a single set of struts within Hubble itself! Whilst the spikes are technically an inaccuracy, many astrophotographers choose to emphasise and celebrate them as a beautiful feature of their images.



I've got a version of that Sagittarius picture if interested. They cut it in half because there is some unspoken rule about never filling the chip gap with anything but real data, but I have no qualms with it as long as I mention that I did so in the description...
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Re: Found images: 2017 January

Postby Ann » Tue Jan 17, 2017 12:48 am

Thanks, Geck! Can you tell us the coordinates of the field we are seeing? And what magnitudes are the brightest stars?

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Re: Found images: 2017 January

Postby geckzilla » Tue Jan 17, 2017 5:20 am

The coordinates are 17:47:47.522 -24:42:13.11
I don't have any measurements on the stars in the frame. A nearby one that looks similarly bright to the brightest star in the image has some flux measurements here: http://simbad.u-strasbg.fr/simbad/sim-i ... &NbIdent=1 (I think the B and V ones are the ones that interest you?)
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Re: Found images: 2017 January

Postby Ann » Tue Jan 17, 2017 5:35 am

geckzilla wrote:The coordinates are 17:47:47.522 -24:42:13.11
I don't have any measurements on the stars in the frame. A nearby one that looks similarly bright to the brightest star in the image has some flux measurements here: http://simbad.u-strasbg.fr/simbad/sim-i ... &NbIdent=1 (I think the B and V ones are the ones that interest you?)


They are! :wink:

But the star you gave me a link to is faint 11th magnitude, and if the stars in the picture are similar, my software likely has very little information on them.

Thanks a lot, though!

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Re: Found images: 2017 January

Postby geckzilla » Tue Jan 17, 2017 5:42 am

Terzan 5 is just a little bit southeast of the field. Might be something of interest there.
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Re: Found images: 2017 January

Postby starsurfer » Tue Jan 17, 2017 5:55 pm

vdB38 and Sh2-265
http://www.atacama-photographic-observatory.com/page_photo.php?id=61
Copyright: Thierry Demange, Richard Galli and Thomas Petit
vdb38.jpg
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Re: Found images: 2017 January

Postby starsurfer » Tue Jan 17, 2017 5:58 pm

Medusa Nebula (Abell 21)
http://www.cxielo.ch/gallery/v/nebulae/pk205-cx.jpg.html
Copyright: Martin Rusterholz
pk205.jpg
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Re: Found images: 2017 January

Postby starsurfer » Wed Jan 18, 2017 2:21 pm

vdB149 and vdB150
http://www.straightontillmorning.me/Astronomy/Nebula/Colour/i-8KpxgCq/X2
Copyright: Hytham Abu-Safieh
vdb149.jpg
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Re: Found images: 2017 January

Postby starsurfer » Thu Jan 19, 2017 2:34 pm

NGC 7662
http://www.pbase.com/skybox/image/164786525
Copyright: Kevin Quin
164786525.15R3WRBq.jpg
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Re: Found images: 2017 January

Postby starsurfer » Thu Jan 19, 2017 2:37 pm

vdB133 and Sh2-106
http://www.astrobin.com/232784/
Copyright: Tommy Nawratil
1bcfd478ecd6f9d73408af87bfc0efc7.1824x0.jpg

vdB133 is the blue reflection nebula in the bottom left corner and Sh2-106 is the red emission nebula in the top right corner.
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Re: Found images: 2017 January

Postby starsurfer » Thu Jan 19, 2017 2:40 pm

DI Chamaeleontis
https://www.spacetelescope.org/images/potw1543a/
Copyright: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt

This nebula can also be found somewhere in this image by CEDIC.

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Re: Found images: 2017 January

Postby starsurfer » Mon Jan 23, 2017 2:07 pm

Abell 39
http://www.capella-observatory.com/ImageHTMLs/PNs/Abell39.htm
Copyright: Stefan Binnewies and Josef Pöpsel
Abell39.jpg
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Re: Found images: 2017 January

Postby starsurfer » Mon Jan 23, 2017 2:09 pm


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Re: Found images: 2017 January

Postby starsurfer » Mon Jan 23, 2017 2:12 pm

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Re: Found images: 2017 January

Postby starsurfer » Mon Jan 23, 2017 2:13 pm

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

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Re: Found images: 2017 January

Postby Ann » Mon Jan 23, 2017 2:59 pm

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


Thanks!

Wow! That's seriously blue stuff!!

My software classifies this object as multiple, and the brightest part of it, which is indeed IC 4662, has the following color indexes: 0.410 (B-V) and −0.370 (U-B). Yes, that's blue, and it looks even bluer!

My software, Guide, includes this piece of information about IC 4662: It is not a planetary! Fancy that!

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Re: Found images: 2017 January

Postby Ann » Mon Jan 23, 2017 3:18 pm



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!

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HEIC: Starbirth with a Chance of Winds? (NGC 4861)

Postby bystander » Mon Jan 23, 2017 4:02 pm

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

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.
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Re: Found images: 2017 January

Postby starsurfer » Thu Jan 26, 2017 3:14 pm

Ann wrote:


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

Yes this galaxy has four prominent globular clusters that can be observed in telescopes by amateurs. I'm glad these galaxy images are making you happy! :D

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Re: Found images: 2017 January

Postby starsurfer » Thu Jan 26, 2017 3:15 pm


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Re: HEIC: Starbirth with a Chance of Winds? (NGC 4861)

Postby Ann » Thu Jan 26, 2017 6:00 pm

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

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.


WOW!!! That's amazing!!!

My software, Guide, reports (through Principal Galaxy Catalog) that the effective U-B index of NGC 4861 is −0.670!!!

Shhh...yes... I must admit... I don't really know the difference between the total and the effective U-B index. But seriously... whatever the difference, any sort of U-B index that is −0.670 is amazing!!!

Oh, and - yes, the effective B-V index is 0.350, which is certainly blue, too. And seriously, this is a killer blue and pink galaxy!!!

Although Dash of the Incredibles is talking about something else entirely, I feel almost as excited and delighted as he does in this video clip!

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Re: Found images: 2017 January

Postby Ann » Thu Jan 26, 2017 6:19 pm

Yes, I know - the reason why NGC 4861 could get so blue is because the galaxy is small, with a weak and faint yellow population. One extremely powerful starburst in one restricted part of the galaxy is enough to totally skew the color indexes into something that would be impossible for a Milky Way-sized galaxy with a bright yellow population.

Just looking at the starburst cluster makes me think that this is a really major starburst, comparable to R136 in the Tarantula Nebula in the Large Magellanic Cloud.

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Re: Found images: 2017 January

Postby starsurfer » Fri Jan 27, 2017 4:53 pm

NGC 3256
http://www.astrobin.com/236628/0/
Copyright: Ray Johnson
0cdef30d8ee875fb1b637b4964b3ec8e.1824x0.jpg
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Re: Found images: 2017 January

Postby starsurfer » Fri Jan 27, 2017 4:55 pm


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Re: Found images: 2017 January

Postby Ann » Fri Jan 27, 2017 7:30 pm

NGC 383
https://commons.wikimedia.org/wiki/File ... GC_383.jpg

This is elliptical/lenticular galaxy NGC 383 and its inner disk. The picture has been created by Judy Schmidt, Geckzilla, using various Hubble data (I think).

Fantastic image!

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