APOD: Zeta Oph: Runaway Star (2017 Apr 08)

[APOD Robot]

Zeta Oph: Runaway Star

Explanation: Like a ship plowing through cosmic seas, runaway star Zeta Ophiuchi produces the arcing interstellar bow wave or bow shock seen in this stunning infrared portrait. In the false-color view, bluish Zeta Oph, a star about 20 times more massive than the Sun, lies near the center of the frame, moving toward the left at 24 kilometers per second. Its strong stellar wind precedes it, compressing and heating the dusty interstellar material and shaping the curved shock front. What set this star in motion? Zeta Oph was likely once a member of a binary star system, its companion star was more massive and hence shorter lived. When the companion exploded as a supernova catastrophically losing mass, Zeta Oph was flung out of the system. About 460 light-years away, Zeta Oph is 65,000 times more luminous than the Sun and would be one of the brighter stars in the sky if it weren't surrounded by obscuring dust. The image spans about 1.5 degrees or 12 light-years at the estimated distance of Zeta Ophiuchi.

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[BDanielMayfield]

What is the galactic escape velocity for Zeta Oph and stars in the Sun's neighborhood?

Bruce

[Ann]

What is the galactic escape velocity for Zeta Oph and stars in the Sun's neighborhood?

Bruce

Well, what do I know, Bruce, but at least I found this:

TildalWave at Stack Exchange Space Exploration wrote:
RAVE took a sample of 90 high-velocity Milky Way stars (some moving at over 300 km/s) for which their position and velocity was determined sufficiently precise, and then compared their movement to models of other, similar spiral galaxies, to reach an estimate of Milky Way's total mass at about 1.6 trillion solar masses. Once they had that, they could calculate estimated escape velocities for our stellar neighbourhood, for which mass distribution and radial velocity with respect to the galactic barycenter are of course most well understood.

Solar system's orbital velocity is estimated at roughly 220 km/s, and galactic escape velocity for our vicinity at about 537 km/s. So in the direction of Solar system's velocity vector, velocity required to escape Milky Way is ~ 317 km/s. And much more, if this Solar system's own orbital momentum cannot be used to full extent and a launch in other directions is required. This is of course assuming you can launch on a trajectory that avoids getting too close to gravitational influence of other solar systems.

The RAVE survey: the Galactic escape speed and the mass of the Milky Way, Piffl et al., 17 Sep 2013 (Complete PDF)

The RAVE Survey: Constraining the Local Galactic Escape Speed, Smith et al., 9 May 2007 (Complete PDF)

Ann

[Alexander331]

What are these two isolated red dots left and right the arc bow, around the middle of the frame ?

[heehaw]

So in the direction of Solar system's velocity vector, velocity required to escape Milky Way is ~ 317 km/s. And much more, if this Solar system's own orbital momentum cannot be used to full extent and a launch in other directions is required. This is of course assuming you can launch on a trajectory that avoids getting too close to gravitational influence of other solar systems.
Ann

Hey, now THERE"S a project for NASA!! Let's get this solar system OUT of this darned galaxy that we're currently stuck in! Let's hit the road! Outside this mucky interstellar medium we are at the moment surrounded by, we'd get a much cleaner view of that lovely universe out there! And we could look back and really see our own Galaxy for the first time!

[NCTom]

Given this came from Spitzer and enhanced with false color, what does the heavy green represent even to coloring a nice spiral galaxy near the bottom? I also wondered about the red dots, the left one of which has a pretty halo.

[starsurfer]

Click to play embedded YouTube video.

[cytophile]

The measurement of the velocity of the star seems to imply consideration of a particular inertial frame of reference, appropriate to this context. Is it's motion assumed to be relative to the sun, the galactic center, the whole cosmos?

[De58te]

Given this came from Spitzer and enhanced with false color, what does the heavy green represent even to coloring a nice spiral galaxy near the bottom? I also wondered about the red dots, the left one of which has a pretty halo.

The "stunning infrared portrait" link says, " For this Spitzer image, infrared light at wavelengths of 3.6 and 4.5 microns is rendered in blue, 8.0 microns in green, and 24 microns in red. "

[Chris Peterson]

Given this came from Spitzer and enhanced with false color, what does the heavy green represent even to coloring a nice spiral galaxy near the bottom? I also wondered about the red dots, the left one of which has a pretty halo.

The "stunning infrared portrait" link says, " For this Spitzer image, infrared light at wavelengths of 3.6 and 4.5 microns is rendered in blue, 8.0 microns in green, and 24 microns in red. "

FWIW, that nominally translates to 450° C material for blue, 90° C material for green, and -150° C material for red. (Those are the blackbody peaks; the curves are very broad, of course, so the numbers only give a sense of the temperature range for each filter.)

[Ann]

The measurement of the velocity of the star seems to imply consideration of a particular inertial frame of reference, appropriate to this context. Is it's motion assumed to be relative to the sun, the galactic center, the whole cosmos?

Click to view full size image

Ophiuchus constellation. Map: Torsten Bronger.

The velocity of Zeta Ophiuchi is probably measured either relative to the Sun, or, perhaps more likely, relative to other stars at more or less the same distance from us in more or less the same part of the sky. Zeta (ζ) Ophiuchi is moderately close to Beta1 (β) Scorpii, Graffias, in the sky. The two stars belong to very similar spectral classes and are at relatively similar distances from us. It's just possible that these two stars are related.

They have very different proper motions, which makes sense if one of them is a runaway star.

Ann

[BDanielMayfield]

What is the galactic escape velocity for Zeta Oph and stars in the Sun's neighborhood?

Bruce

Well, what do I know, Bruce, but at least I found this:

... Solar system's orbital velocity is estimated at roughly 220 km/s, and galactic escape velocity for our vicinity at about 537 km/s. So in the direction of Solar system's velocity vector, velocity required to escape Milky Way is ~ 317 km/s.

Ann

That's what I was looking for. Thanks Ann.
It shows that Zeta Oph isn't really running all that fast. It's [destiny is] still firmly stuck in this galaxy.

Bruce

[ta152h0]

I want a poster, and an ice cold one to help look at it

[Ann]

Given this came from Spitzer and enhanced with false color, what does the heavy green represent even to coloring a nice spiral galaxy near the bottom? I also wondered about the red dots, the left one of which has a pretty halo.

The "stunning infrared portrait" link says, " For this Spitzer image, infrared light at wavelengths of 3.6 and 4.5 microns is rendered in blue, 8.0 microns in green, and 24 microns in red. "

FWIW, that nominally translates to 450° C material for blue, 90° C material for green, and -150° C material for red. (Those are the blackbody peaks; the curves are very broad, of course, so the numbers only give a sense of the temperature range for each filter.)

450^o C doesn't do justice to 32,000K Zeta Ophiuchi. That's infrared for you.

I remember, long ago when three-color mapped infrared photography was pretty new, I saw a splendid-looking apparently RGB picture of a star field in, I think, Carina. There were two bright and extremely blue stars in that field, and they looked terrific. I spent hours trying to identify them, until, to my horror (yes!), I realized that they were actually a pair of red M-type giants!! They looked so blue because they are so red - well, they sure emit a lot of 450^o C infrared light! If Venus was photographed in infrared light and color-mapped in the same way, it too would look brilliantly blue!

But Zeta Ophiuchi's bow shock looks great in infrared. The center of the Milky Way galaxy does, too.

Ann

[BDanielMayfield]

The measurement of the velocity of the star seems to imply consideration of a particular inertial frame of reference, appropriate to this context. Is it's motion assumed to be relative to the sun, the galactic center, the whole cosmos?

It would have to be the local average motion that this 24 km/s is measured against. Wikipedia says that the radial velocity of Zeta Oph is -15 km/s, so it is moving away from the Sun at 15 km/s.

Bruce

[Chris Peterson]

The "stunning infrared portrait" link says, " For this Spitzer image, infrared light at wavelengths of 3.6 and 4.5 microns is rendered in blue, 8.0 microns in green, and 24 microns in red. "

FWIW, that nominally translates to 450° C material for blue, 90° C material for green, and -150° C material for red. (Those are the blackbody peaks; the curves are very broad, of course, so the numbers only give a sense of the temperature range for each filter.)

450^o C doesn't do justice to 32,000K Zeta Ophiuchi.

Actually, in a way it does, since a 32,000 K object emits extremely little of its total energy in the infrared, and yet, this star is so bright that it even appears so at a 4 micrometer wavelength!

[BDanielMayfield]

Wikipedia says that the radial velocity of Zeta Oph is -15 km/s, so it is moving away from the Sun at 15 km/s.

That means this star once was much closer to us than it is now. I wonder how close it was to the Sun when its partner popped?

Bruce

[BDanielMayfield]

Hey, now THERE"S a project for NASA!! Let's get this solar system OUT of this darned galaxy that we're currently stuck in! Let's hit the road! Outside this mucky interstellar medium we are at the moment surrounded by, we'd get a much cleaner view of that lovely universe out there! And we could look back and really see our own Galaxy for the first time!

Galactic Control and The Big Giant Head would never ok such a mission.

[geckzilla]

The red dots I think are artifacts. They don't show up anywhere else—not WISE or any of the other Spitzer channels. I haven't worked with Spitzer data as much as Hubble though, so I'm not totally certain.

[Chris Peterson]

Wikipedia says that the radial velocity of Zeta Oph is -15 km/s, so it is moving away from the Sun at 15 km/s.

That means this star once was much closer to us than it is now. I wonder how close it was to the Sun when its partner popped?

A negative radial velocity means it is getting nearer to us (although the actual direction is determined by combining the radial and tangential velocities).

[Whiskybreath]

An excellent photograph; I wonder if anything can be deduced or surmised by the clearly-defined 'tendrils' in the bow-wave?

[Mokurai]

It is incorrect to say that Zeta Oph was "flung out" of its binary system when its companion exploded. It simply continued at the same speed it had in orbit, in the direction it was going when the supernova blew past it. This is just Newton's First Law:

An object in motion tends to remain in motion in a straight line.

[ta152h0]

I just bought a handfull of filters I am going to " play with " in preparation to image the upcoming total eclipse just soutj of here ( 48 North )

[BDanielMayfield]

Wikipedia says that the radial velocity of Zeta Oph is -15 km/s, so it is moving away from the Sun at 15 km/s.

That means this star once was much closer to us than it is now. I wonder how close it was to the Sun when its partner popped?

A negative radial velocity means it is getting nearer to us (although the actual direction is determined by combining the radial and tangential velocities).

Thanks for the correction Chris. I'd rather be embarrassed than permanently in error.
That is one reason I make comments at times even when I'm not 100% sure of correctness, so I can improve my understanding.

Bruce

[jpicciri]

I've read many explanations for runaway stars that involve a supernova that then "releases" its companion star.
Doesn't the companion still revolve around the center of mass? Does the runaway happen after the supernova
remnants pass the orbit of the companion star? I'm not understanding the kinematics.

Thanks,
John-