Starship Asterisk*

Chris Peterson wrote:

BDanielMayfield wrote:As bowshocks go, this one doesn't appear particularly violent. At least, that's the impression it gives me. This fits with its [the star's] velocity being not that extraordinarily fast.

I'm not sure any bowshocks are really what I'd call "violent". They are slow, evolving over thousands to millions of years. Their densities are lower than the hardest vacuums we make in a lab. Really, it's just particles colliding with particles resulting in enough heat to produce rather high energy photons. But the total energy is small.

neufer wrote:https://apod.nasa.gov/apod/ap001128.html

BDanielMayfield wrote:As bowshocks go, this one doesn't appear particularly violent. At least, that's the impression it gives me. This fits with its [the star's] velocity being not that extraordinarily fast.

Case wrote:

APOD Robot wrote:The image spans about 1.5 degrees or 12 light-years at the estimated distance of Zeta Ophiuchi.

Superimposed over a DSS2 image (from Wikisky: blue/red/near infrared) of the same area, it is made obvious how different the Spitzer Space Telescope sees things than a ground based survey does. Not just the brightness of Zeta, but also the invisibility of that nebulosity in the DSS2 plates, which is so prominent in the APOD.

Ann wrote: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.

Wikipedia has an interesting article about Beta Scorpii, in that it is a system with no less than six stars. β¹ would then be a subgroup of three stars. The article also mentions the common origin of the Scorpius-Centaurus Association of stars.

Ann wrote:Thanks, Case, that is a brilliant "image comparison"!

Case wrote:

APOD Robot wrote:The image spans about 1.5 degrees or 12 light-years at the estimated distance of Zeta Ophiuchi.

Superimposed over a DSS2 image (from Wikisky: blue/red/near infrared) of the same area, it is made obvious how different the Spitzer Space Telescope sees things than a ground based survey does. Not just the brightness of Zeta, but also the invisibility of that nebulosity in the DSS2 plates, which is so prominent in the APOD.

APOD Robot wrote:The image spans about 1.5 degrees or 12 light-years at the estimated distance of Zeta Ophiuchi.

Ann wrote: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.

Mokurai wrote:
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.

jpicciri wrote: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-

jpicciri wrote: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.

Chris Peterson wrote:

BDanielMayfield wrote:

BDanielMayfield wrote: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).

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

BDanielMayfield wrote:

BDanielMayfield wrote: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?

heehaw wrote: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!

BDanielMayfield wrote: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.

Ann wrote:

Chris Peterson wrote:

De58te wrote: 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.

cytophile wrote: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?

Chris Peterson wrote:

De58te wrote:

NCTom wrote: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.)