APOD: Melotte 15 in the Heart (2017 Feb 10)

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APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by APOD Robot » Fri Feb 10, 2017 5:05 am

Image Melotte 15 in the Heart

Explanation: Cosmic clouds form fantastic shapes in the central regions of emission nebula IC 1805. The clouds are sculpted by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster, Melotte 15. About 1.5 million years young, the cluster stars are scattered in this colorful skyscape, along with dark dust clouds in silhouette against glowing atomic gas. A composite of narrowband and broadband telescopic images, the view spans about 15 light-years and includes emission from ionized hydrogen, sulfur, and oxygen atoms mapped to green, red, and blue hues in the popular Hubble Palette. Wider field images reveal that IC 1805's simpler, overall outline suggests its popular name - The Heart Nebula. IC 1805 is located about 7,500 light years away toward the boastful constellation Cassiopeia.

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Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by saturno2 » Fri Feb 10, 2017 6:12 am

Very interesting image

heehaw

Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by heehaw » Fri Feb 10, 2017 11:50 am

Terrific 3D effect!
We tend, I think, to forget that almost all of the matter in the universe is just (like this APOD) floating in space: is not subject to a g-force in a particular direction, as we are: and is floating in a universe that is not just expanding but that is, quite literally, exploding! And we are stuck to one of the fragments! Hold tight!

Roger V.

Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Roger V. » Fri Feb 10, 2017 1:30 pm

This picture is particularly beautiful.

One of the interesting things about the Heart Nebula is the bright star to the upper right of the center of this image. The one I am referring to is the upper one of the two brightest stars in the image. It is HD 15558, and it is a double star, a spectroscopic binary with an orbital period of 442 days, and masses estimated at 152 and 46 solar masses. (It looks like a visual double star in this image, but that is not the companion star I speak of. As a spectroscopic binary, the two stars are much too close together to resolve in any telescope.) Wikipedia has an informative article about this star, and it's interesting that so much has been learned about it.

At 152 solar masses, the primary is considered to be approximately the 8th most massive star known, and the most massive one visible to to those of us who cannot see the Large Megallanic Cloud in our northern skies. It's of spectral type O4.5, while its 46-solar mass companion is of type O7.

The pair has a visual magnitude of 8, easily seen in binoculars.

-- Roger V.

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Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Chris Peterson » Fri Feb 10, 2017 1:57 pm

heehaw wrote:Terrific 3D effect!
We tend, I think, to forget that almost all of the matter in the universe is just (like this APOD) floating in space: is not subject to a g-force in a particular direction, as we are: and is floating in a universe that is not just expanding but that is, quite literally, exploding!
This matter (and all matter in the Universe) is surely subject to gravitational forces! In fact, this matter, like our solar system, is in orbit within the Milky Way, following Kepler's and Newton's laws just like everything else. Neither is it exploding. Some material is dispersing, while other regions are coming together under the influence of gravity.
Chris

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Doink

Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Doink » Fri Feb 10, 2017 5:24 pm

Chris Peterson wrote:
heehaw wrote:Terrific 3D effect!
We tend, I think, to forget that almost all of the matter in the universe is just (like this APOD) floating in space: is not subject to a g-force in a particular direction, as we are: and is floating in a universe that is not just expanding but that is, quite literally, exploding!
This matter (and all matter in the Universe) is surely subject to gravitational forces! In fact, this matter, like our solar system, is in orbit within the Milky Way, following Kepler's and Newton's laws just like everything else. Neither is it exploding. Some material is dispersing, while other regions are coming together under the influence of gravity.
O.K., points taken, but I took HeeHaw's statements slightly differently. In the case of nebulae, et al the local effects of gravitation would seem much less intense/imeadiate than on the surface of a planet or other dense body to our senses. Regarding "not just expanding but that is, quite literally, exploding" I assumed HeeHaw was referring to the expansion of the universe and Big Bang. Just my perspective.

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Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Chris Peterson » Sat Feb 11, 2017 12:34 am

Doink wrote:
Chris Peterson wrote:
heehaw wrote:Terrific 3D effect!
We tend, I think, to forget that almost all of the matter in the universe is just (like this APOD) floating in space: is not subject to a g-force in a particular direction, as we are: and is floating in a universe that is not just expanding but that is, quite literally, exploding!
This matter (and all matter in the Universe) is surely subject to gravitational forces! In fact, this matter, like our solar system, is in orbit within the Milky Way, following Kepler's and Newton's laws just like everything else. Neither is it exploding. Some material is dispersing, while other regions are coming together under the influence of gravity.
O.K., points taken, but I took HeeHaw's statements slightly differently. In the case of nebulae, et al the local effects of gravitation would seem much less intense/imeadiate than on the surface of a planet or other dense body to our senses.
Of course. With our senses, we would not be able to detect the difference between a nebula and the most distant reaches of intergalactic space. Similarly, we do not detect the effects of the Milky Way's gravity, although they are profound.
Regarding "not just expanding but that is, quite literally, exploding" I assumed HeeHaw was referring to the expansion of the universe and Big Bang. Just my perspective.
Not how I took it, but he can clarify that comment if he wants.
Chris

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Robolt

Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Robolt » Sat Feb 11, 2017 2:57 am

...on a more serious note, I like the little running ostrich (center of the field) whose head seems about ready to pluck out the bright double star.

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Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Ann » Sat Feb 11, 2017 4:51 am

Roger V. wrote:This picture is particularly beautiful.

One of the interesting things about the Heart Nebula is the bright star to the upper right of the center of this image. The one I am referring to is the upper one of the two brightest stars in the image. It is HD 15558, and it is a double star, a spectroscopic binary with an orbital period of 442 days, and masses estimated at 152 and 46 solar masses. (It looks like a visual double star in this image, but that is not the companion star I speak of. As a spectroscopic binary, the two stars are much too close together to resolve in any telescope.) Wikipedia has an informative article about this star, and it's interesting that so much has been learned about it.

At 152 solar masses, the primary is considered to be approximately the 8th most massive star known, and the most massive one visible to to those of us who cannot see the Large Megallanic Cloud in our northern skies. It's of spectral type O4.5, while its 46-solar mass companion is of type O7.

The pair has a visual magnitude of 8, easily seen in binoculars.

-- Roger V.
Thanks for calling my attention to this star, Roger V.! I have never taken much of an interest in IC 1805 (the nebula) or Melotte 15 (the stars), because of, obviously, the colors. The reddened stars, the flat red hue of the nebula, or the Hubble palette version of it - plus the scattered, almost sparse appearance of the cluster...
Image
But the suggested mass of HD 15558 is just amazing!! :shock: According to this list, HD 15558 A is indeed the 8th most massive star known anywhere! Not only that, but the seven stars ahead of it on the list are all in the large Magellanic Cloud, in or near the titanic cluster of supermassive stars, R136! And the next Milky Way star on the list is in 12th place! So according to this list, HD 15558 A would be the most massive star that we know of in the entire Milky Way!!!! :shock:

Sorry for all the exclamation marks, but I'm just stunned.

I'm just a tad doubtful, too. All the seven stars that are listed as more massive than HD 15558 A are all more than 3 million times more luminous than the Sun. HD 15558 A, by contrast, is "only" ~660,000 L. That's a huge difference in luminosity. Admittedly six of the seven stars ahead of HD 15558 A are Wolf-Rayet stars, which are particularly luminous even for their mass, and HD 15558 A is an O-type giant. But there is another O-type star ahead of HD 15558 A on the list, Melnick 42, whose luminosity is 3,600,000 solar. Of course, Melnick 42 is an "extreme" O-type star of spectral class O2If, with a surface temperature of 47,300 K and a radius of 21.1 solar, whereas HD 15558 A is "only" 39,500 K and 16.4 R. So all in all, I can't help thinking that HD 15558 A appears somewhat faint, cool and small for the tremendous mass it is believed to contain.
Wikipedia wrote:
The primary may itself be a double star, suggested by the improbably large mass found from the binary orbit when compared to the other stellar parameters.
That's what I thought, too.

We may compare HD 15558 A with NGC 3603-B, the only other Milky Way star among the top twelve. NGC 3603-B is a Wolf-Rayet star of spectral class WN6h. At 2,900,000 L it is more than four times more luminous than HD 15558 A, and at 42,000 K and 33.8 R it is both hotter and (very much) larger. It gives every appearance of being a much more powerful star than HD 15558 A.

So I'm doubtful that HD 15558 A is as massive as >152 ± 51 M. But clearly it is a fantastic star in any case, and I must really thank you, Roger V., for calling my attention to it! :D

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Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by neufer » Sat Feb 11, 2017 5:05 pm

Ann wrote:
Roger V. wrote:
One of the interesting things about the Heart Nebula is the bright star to the upper right of the center of this image. The one I am referring to is the upper one of the two brightest stars in the image. It is HD 15558, and it is a double star, a spectroscopic binary with an orbital period of 442 days, and masses estimated at 152 and 46 solar masses. (It looks like a visual double star in this image, but that is not the companion star I speak of. As a spectroscopic binary, the two stars are much too close together to resolve in any telescope.) Wikipedia has an informative article about this star, and it's interesting that so much has been learned about it.

At 152 solar masses, the primary is considered to be approximately the 8th most massive star known, and the most massive one visible to to those of us who cannot see the Large Megallanic Cloud in our northern skies. It's of spectral type O4.5, while its 46-solar mass companion is of type O7.

The pair has a visual magnitude of 8, easily seen in binoculars.
https://en.wikipedia.org/wiki/HD_15558 wrote:
The primary may itself be a double star, suggested by the improbably large mass found from the binary orbit when compared to the other stellar parameters.
We may compare HD 15558 A with NGC 3603-B, the only other Milky Way star among the top twelve. NGC 3603-B is a Wolf-Rayet star of spectral class WN6h. At 2,900,000 L it is more than four times more luminous than HD 15558 A, and at 42,000 K and 33.8 R it is both hotter and (very much) larger. It gives every appearance of being a much more powerful star than HD 15558 A. So I'm doubtful that HD 15558 A is as massive as >152 ± 51 M. But clearly it is a fantastic star in any case, and I must really thank you, Roger V., for calling my attention to it! :D
  • --------------------------------------------------------
    • Toilus and Cressida: IV, iv
    PANDARUS: What a pair of spectacles is here!
    . Let me embrace too. 'O heart,' as the goodly saying is,
    . '--O heart, *HEAVY HEART*,
    . Why sigh'st thou without breaking?

    --------------------------------------------------------
    • Love's Labour's Lost: V, ii
    PRINCESS: *A HEAVY HEART* bears not a nimble tongue:
    --------------------------------------------------------
    • Othello: V, ii
    LODOVICO: [To IAGO] Myself will straight aboard: and to the state
    . This heavy act *with HEAVY HEART* relate.

    --------------------------------------------------------
    • King Richard II: V, i
    KING RICHARD II: Twice for one step I'll groan, the way being short,
    . And piece the way out *with a HEAVY HEART*.

    --------------------------------------------------------
    • King Richard III: III, i
    PRINCE EDWARD: ... and *with a HEAVY HEART*,
    . Thinking on them, go I unto the Tower.

    --------------------------------------------------------
Art Neuendorffer

Catalina

Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Catalina » Sat Feb 11, 2017 7:41 pm

What keeps massive binary stars from immediately colliding with each other versus the gradual exchange of matter via a spiral tendril?

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Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Chris Peterson » Sat Feb 11, 2017 8:02 pm

Catalina wrote:What keeps massive binary stars from immediately colliding with each other versus the gradual exchange of matter via a spiral tendril?
They are in orbit around each other. The same thing that keeps the Earth from immediately colliding with the Sun, or the Earth with the Moon.
Chris

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Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by neufer » Sat Feb 11, 2017 8:25 pm

Chris Peterson wrote:
Catalina wrote:
What keeps massive binary stars from immediately colliding with each other versus the gradual exchange of matter via a spiral tendril?
They are in orbit around each other. The same thing that keeps the Earth from immediately colliding with the Sun, or the Earth with the Moon.
Red supergiants like Betelgeuse & Antares have enormous radii ~1,000 times the radius of the Sun. However, blue supergiants like HD 15558 have relatively compact radii only ~20 R and so will have little interaction with neighboring stars orbiting at 726 R (as is the case with the companion to HD 15558).
Art Neuendorffer

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Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Chris Peterson » Sat Feb 11, 2017 10:20 pm

neufer wrote:
Chris Peterson wrote:
Catalina wrote:
What keeps massive binary stars from immediately colliding with each other versus the gradual exchange of matter via a spiral tendril?
They are in orbit around each other. The same thing that keeps the Earth from immediately colliding with the Sun, or the Earth with the Moon.
Red supergiants like Betelgeuse & Antares have enormous radii ~1,000 times the radius of the Sun. However, blue supergiants like HD 15558 have relatively compact radii only ~20 R and so will have little interaction with neighboring stars orbiting at 726 R (as is the case with the companion to HD 15558).
Of course, once the surfaces of the stars overlap they're going to spiral into each other quite quickly. Even most binary supergiant systems, though, have their members far enough apart to avoid that.
Chris

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Re: APOD: Melotte 15 in the Heart (2017 Feb 10)

Post by Ann » Sun Feb 12, 2017 5:21 am

This very short video shows stars orbiting the central black hole of the Milky Way. Stars so rarely collide with one another or fall into black holes. It happens, but it is very rare.
Click to play embedded YouTube video.
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