APOD: Symbiotic R Aquarii (2022 Feb 05)

[APOD Robot]

Symbiotic R Aquarii

Explanation: Variable star R Aquarii is actually an interacting binary star system, two stars that seem to have a close symbiotic relationship. Centered in this space-based optical/x-ray composite image it lies about 710 light years away. The intriguing system consists of a cool red giant star and hot, dense white dwarf star in mutual orbit around their common center of mass. With binoculars you can watch as R Aquarii steadily changes its brightness over the course of a year or so. The binary system's visible light is dominated by the red giant, itself a Mira-type long period variable star. But material in the cool giant star's extended envelope is pulled by gravity onto the surface of the smaller, denser white dwarf, eventually triggering a thermonuclear explosion, blasting material into space. Astronomers have seen such outbursts over recent decades. Evidence for much older outbursts is seen in these spectacular structures spanning almost a light-year as observed by the Hubble Space Telescope (in red and blue). Data from the Chandra X-ray Observatory (in purple) shows the X-ray glow from shock waves created as a jet from the white dwarf strikes surrounding material.

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[Ann]

Symbiotic R Aquarii. X-ray: NASA/CXC/SAO/R. Montez et al.,
Optical: Data: NASA/ESA/STScI, Processing: Judy Schmidt

I tried to make sense of today's APOD, but it wasn't easy! What do the colors mean? I found the original source of the image here, but it contained no useful information about the colors of the image. Then I found this:

---

Lo and behold, this is a Geckzilla image! Judy Schmidt! And she has written a very interesting caption for this Wikimedia image:

Judy Schmidt wrote:

Last night when I saw Space Telescope Live tweet out that it was looking at this, I thought wow, what a cool-looking thing, can't wait to see Hubble images of it. Then I decided to check the archive to see if it already had, and lo and behold, it had. The telescope seems to be doing somewhat yearly observations of the object to characterize and measure the movement of the jets on this thing.

In 2013, and then in 2014 on this same day Hubble did these observations. I presume it is no coincidence that it is once again looking this year after a three-year gap. Keep it up for a thousand years and you'll have a nice animation! I'm pretty sure movement can be seen by Hubble even with one year intervals, so the jets are quite fast. Surprisingly, the proposal for these observations suggests a twelve-year interval would be good to measure them, but I'm not totally sure the entire twelve years is necessary? Well, I could be mistaken. I was comparing the F502N data from 2013 to the F658N data from 2014, and those are pretty different bands, so it might not be movement.

A few months ago this object was featured on APOD, and now that I look at that image again I do recall seeing it, but wow, what a difference. In the APOD image, which combines ground data from Adam Block, and x-ray data from the Chandra space telescope, one is able to see the outer parts of the nebula which didn't quite fit on Hubble's detector. It's hard to say what shape the nebula is in, but it does remind me of a clumpy version of an hourglass-type nebula, sort of like Hb 12, but with jets too. I feel like there is a lot to learn about this object, but I've only just begun.

This system is curiously bright at certain infrared bands, and I'm not entirely sure why. I'd love to see what JWST makes of this thing. Being such a well-studied object, I would guess that it will eventually become a Webb target.

There were some nice, short exposures I was able to use to clear off the charge bleeds. Some of the nebula was cropped off to satisfy compositional aesthetics, and because it was crossed by the evil chip gap. I rotated the diffraction spikes in the F502N data to match the F658N spikes. It looks a bit less funny that way.

I made use of data from the following proposal: R Aqr: a prototype for non-relativistic astrophysical jets and a key for understanding jet formation

Red: WFC3/UVIS F658N (ic9k07020_drc) Green: WFC3/UVIS F656N (ic9k06020_drc) & WFC3/UVIS F631N (ic9k01020_drc) Blue: WFC3/UVIS F502N (ic9k01010_drc)

North is NOT up. It is 86.18° counter-clockwise from up.

Date 18 October 2017, 23:05

Source Symbiotic System R Aquarii
Author Judy Schmidt from USA

Wow! Judy Schmidt wrote this, our own Geckzilla! Thank you, Geck!

Anyway. In Geck's image, red means inozed nitrogen at 658 nm. Green means hydrogen alpha at 656 nm. Blue means ionized oxygen at 501 nm.

Please note that ionized nitrogen might play a larger role here than H-alpha, at least for the outer structures.

My guess, however, is that the red structures that we are seeing in the APOD are a combination of N II, ionized nitrogen, and Hα. The blue structures are, I suppose, doubly ionized oxygen, OIII.

It seems reasonable to me that the weird orange hue of the red structures in the APOD has been chosen precisely because this color represents both N II and Hα in the APOD.

Ann

[bystander]

...
Wow! Judy Schmidt wrote this, our own Geckzilla! Thank you, Geck!

Anyway. In Geck's image, red means inozed nitrogen at 658 nm. Green means hydrogen alpha at 656 nm. Blue means ionized oxygen at 501 nm.

Please note that ionized nitrogen might play a larger role here than H-alpha, at least for the outer structures.

My guess, however, is that the red structures that we are seeing in the APOD are a combination of N II, ionized nitrogen, and Hα. The blue structures are, I suppose, doubly ionized oxygen, OIII.

It seems reasonable to me that the weird orange hue of the red structures in the APOD has been chosen precisely because this color represents both N II and Hα in the APOD.

Ann

Actually, today's image is a composite. Optical data from Hubble, processed by geckzilla; and X-ray data from Chandra, shown in purple. See Fast Facts for R Aquarii about the middle of the page here.

[Ann]

...
Wow! Judy Schmidt wrote this, our own Geckzilla! Thank you, Geck!

Anyway. In Geck's image, red means inozed nitrogen at 658 nm. Green means hydrogen alpha at 656 nm. Blue means ionized oxygen at 501 nm.

Please note that ionized nitrogen might play a larger role here than H-alpha, at least for the outer structures.

My guess, however, is that the red structures that we are seeing in the APOD are a combination of N II, ionized nitrogen, and Hα. The blue structures are, I suppose, doubly ionized oxygen, OIII.

It seems reasonable to me that the weird orange hue of the red structures in the APOD has been chosen precisely because this color represents both N II and Hα in the APOD.

Ann

Actually, today's image is a composite. Optical data from Hubble, processed by geckzilla; and X-ray data from Chandra, shown in purple. See Fast Facts for R Aquarii about the middle of the page here.

You are absolutely right, bystander. I think the purple parts of the APOD are easy to discern and understand: They represent X-rays.

What I didn't understand about the APOD was the orange color of the so called "red" features, and I also wondered why the outer orange features had never shown up in any other images (at least not in any other images that I could find).

But if the outer features are really faint in Hα and brighter in N II, then that might explain why these features had not previously been seen (at least not in images that are easily found by googling). Very many astrophotographers use an Hα filter to photograph nebulas, but few, I think, use an N II filter to bring out details.

Ann

[orin stepanek]

The big and the little of it makes a fantastic view; the golds and the
purples go so good together: twinkle twinkle, big and little!

[Fred the Cat]

Geck - There must be a space cowboy nearby.

[Ann]

Click to view full size image

Geck - There must be a space cowboy nearby.

Thanks for showing us the cowboy hat of R Aquarii, Fred! The similarity is striking!

Ann

[neufer]

Geck - There must be a space cowboy nearby.

You don't see the cowboy under the hat

[Fred the Cat]

Geck - There must be a space cowboy nearby.

You don't see the cowboy under the hat

I think it's in Boötes.

[MarkBour]

Judy Schmidt wrote:
This system is curiously bright at certain infrared bands, and I'm not entirely sure why. I'd love to see what JWST makes of this thing. Being such a well-studied object, I would guess that it will eventually become a Webb target.

Thanks Ann, bystander, and Geck for the info!

It would be great to see a time lapse as the data builds up.

Here's a question about the JWST. So, it's in a halo orbit around L2 and this incredible telescope stays on the far side of its sunshield. How much range of movement does it have for pointing? I guess that scheduling observation of a given target in deep space is restricted to certain times of year. I wonder what is the longest continuous exposure it can take of a location. I don't really know anything much about this -- how exactly does it point at targets? I guess motors in the spacecraft bus point the mirror assembly, rather than that thrusters move the entire JWST for targeting (?)

[neufer]

Here's a question about the JWST. So, it's in a halo orbit around L2 and this incredible telescope stays on the far side of its sunshield. How much range of movement does it have for pointing? I guess that scheduling observation of a given target in deep space is restricted to certain times of year. I wonder what is the longest continuous exposure it can take of a location. I don't really know anything much about this -- how exactly does it point at targets? I guess motors in the spacecraft bus point the mirror assembly, rather than that thrusters move the entire JWST for targeting (?)

<<Observability with JWST is very dependent on a given target's ecliptic latitude. Below 45° ecliptic latitude, JWST can observe targets in 2 visibility windows per year centered about 6 months apart, with each window lasting at least 50 days. Above 45° and below 85° ecliptic latitude, the visibility windows transition to one much longer visibility period. Ecliptic latitude determines the number of days per year that targets are observable by JWST. Also, the allowed field of view position angles on the sky available for a given target are affected by the target's ecliptic latitude. These windows and allowed position angles can be calculated for a particular target using one of the JWST target visibility tools.

JWST has a relatively small continuous viewing zone (CVZ), located within 5° of the ecliptic poles. The CVZ is important for some science programs that involve monitoring throughout the year and will be useful for calibration observations. Although the roll flexibility is still about ±5°, the JWST field of view rotates around the V1 axis (boresight) through the entire available 360° over the course of the year.>>

[VictorBorun]

a bilobed violet creature with a blindigly bright point-like waist seems to jump through an orange loop.
But in fact that X-ray creature just hangs there, right?

[VictorBorun]

I wonder if the brighter lobe (on the left) is towards us and the other is blowing away and is darkened by Doppler's shift

[Chris Peterson]

Anyway. In Geck's image, red means inozed nitrogen at 658 nm. Green means hydrogen alpha at 656 nm. Blue means ionized oxygen at 501 nm.

Please note that ionized nitrogen might play a larger role here than H-alpha, at least for the outer structures.

My guess, however, is that the red structures that we are seeing in the APOD are a combination of N II, ionized nitrogen, and Hα. The blue structures are, I suppose, doubly ionized oxygen, OIII.

It seems reasonable to me that the weird orange hue of the red structures in the APOD has been chosen precisely because this color represents both N II and Hα in the APOD.

The narrowband filters used here are actually not very narrow at all. In fact both the 656 nm filter and the 658 nm filter are highly transmissive to both the N and H emissions. The channels don't separate these two significantly.

[Chris Peterson]

I wonder if the brighter lobe (on the left) is towards us and the other is blowing away and is darkened by Doppler's shift

Why would you expect darkening from Doppler shift? We'd only see that if the motion shifted the wavelength of the light out of the passband of the filter... and that could happen for material moving towards us as easily as away... or both, most likely.

[VictorBorun]

I wonder if the brighter lobe (on the left) is towards us and the other is blowing away and is darkened by Doppler's shift

Why would you expect darkening from Doppler shift? We'd only see that if the motion shifted the wavelength of the light out of the passband of the filter... and that could happen for material moving towards us as easily as away... or both, most likely.

to blue-shift 658 nm wavelength down to 656 nm you need the distance to shorten at 300,000 km/s (658-656)/656 = 900 km/s. Why not ?

[Chris Peterson]

I wonder if the brighter lobe (on the left) is towards us and the other is blowing away and is darkened by Doppler's shift

Why would you expect darkening from Doppler shift? We'd only see that if the motion shifted the wavelength of the light out of the passband of the filter... and that could happen for material moving towards us as easily as away... or both, most likely.

to blue-shift 658 nm wavelength down to 656 nm you need the distance to shorten at 300,000 km/s (658-656)/656 = 900 km/s. Why not ?

Again, why would you expect something moving away to darken and moving towards us to be brighter?

[VictorBorun]

why would you expect something moving away to darken and moving towards us to be brighter?

sorry, that was my misconception. Real Doppler's darkening is at large z, not (900 km/s) / (300,000 km/s) = .003
So the shift can change the filtering, like make the jet toward us all green in the posted pic and the other jet all red.
Which in fact is not so.
Still, the jet to left has a segment much brighter than the rest. May it hit something to burn bright?

[Chris Peterson]

why would you expect something moving away to darken and moving towards us to be brighter?

sorry, that was my misconception. Real Doppler's darkening is at large z, not (900 km/s) / (300,000 km/s) = .003
So the shift can change the filtering, like make the jet toward us all green in the posted pic and the other jet all red.
Which in fact is not so.
Still, the jet to left has a segment much brighter than the rest. May it hit something to burn bright?

It only needs to shift a few nanometers, either blueshift or redshift, to darken because it hits the filter cutoff.

[VictorBorun]

Now the gas in the pic is mostly orange which means it's red (nitrogen at 658 nm) and half as much green (hydrogen alpha at 656 nm).
There are a few filaments of blue (oxygen at 501 nm).
Suppose the 3 filters were narrow and showed bright white in one place with some large Doppler's shift.
But why then just a white bright spot? Why don't we get to see some wild colors, too?

[Chris Peterson]

Now the gas in the pic is mostly orange which means it's red (nitrogen at 658 nm) and half as much green (hydrogen alpha at 656 nm).
There are a few filaments of blue (oxygen at 501 nm).
Suppose the 3 filters were narrow and showed bright white in one place with some large Doppler's shift.
But why then just a white bright spot? Why don't we get to see some wild colors, too?

White with Doppler shift? Not sure what you mean by that.

Most of the time a white pixel just means that all three channels are saturated, so we've lost most of the information.

[bystander]

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