Starship Asterisk*

A Solar Filament Erupts

Explanation: What's happened to our Sun? Nothing very unusual -- it just threw a filament. Toward the middle of 2012, a long standing solar filament suddenly erupted into space, producing an energetic coronal mass ejection (CME). The filament had been held up for days by the Sun's ever changing magnetic field and the timing of the eruption was unexpected. Watched closely by the Sun-orbiting Solar Dynamics Observatory, the resulting explosion shot electrons and ions into the Solar System, some of which arrived at Earth three days later and impacted Earth's magnetosphere, causing visible auroras. Loops of plasma surrounding the active region can be seen above the erupting filament in the featured ultraviolet image. Our Sun is nearing the most active time in its 11-year cycle, creating many coronal holes that allow for the ejection of charged particles into space. As before, these charged particles can create auroras.

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SDO orbits the Earth, not (directly) the Sun. The SOHO is in L1

This image hasn't generated a lot of traffic.

It's not my kind of image either, partly because I tend not to be all that enthusiastic about pictures of the Sun, but mostly because it really irks me that the Sun is shown as orange. Again. Come on, people, the Sun isn't orange!!!

But in spite of this, the picture is impressive. It really is. I like that the picture appears to have been taken very close to the Sun, slightly above (or below) its orbital plane, so that the picture almost gives us a feeling that we are orbiting the Sun ourselves at really close quarters, veering above and below the solar equator, in the same way that Cassini and Juno viewed Saturn and Jupiter really close up and personal and sometimes from "above" or "below".

So, yeah. It's an impressive picture, it really is.

And that's all I have to say about it!

Ann

Ann wrote: ↑Sun May 26, 2024 2:30 pm It's not my kind of image either, partly because I tend not to be all that enthusiastic about pictures of the Sun, but mostly because it really irks me that the Sun is shown as orange.

The image appears to be constructed from a single channel of data made by selecting the brightest pixels in a stack of two layers, one for 0.304 nm and one for 0.171 nm (so two UV channels).

How would you represent that visually?

Chris Peterson wrote: ↑Sun May 26, 2024 2:40 pm

Ann wrote: ↑Sun May 26, 2024 2:30 pm It's not my kind of image either, partly because I tend not to be all that enthusiastic about pictures of the Sun, but mostly because it really irks me that the Sun is shown as orange.

The image appears to be constructed from a single channel of data made by selecting the brightest pixels in a stack of two layers, one for 0.304 nm and one for 0.171 nm (so two UV channels).

How would you represent that visually?

How about showing the UV Sun as purple? I don't understand those who say that it would be horribly wrong to show the UV Sun as purple, but OK to show it as orange.


Ann

I'll only add that "the resulting explosion shot electrons and ions into the Solar System, some of which arrived at Earth three days later" means those electrons and ions were moving at about 1,300,000 mph! (That's 93,000,000 miles / 3 days / 24 hours.)

Ann wrote: ↑Sun May 26, 2024 2:52 pm

Chris Peterson wrote: ↑Sun May 26, 2024 2:40 pm

Ann wrote: ↑Sun May 26, 2024 2:30 pm It's not my kind of image either, partly because I tend not to be all that enthusiastic about pictures of the Sun, but mostly because it really irks me that the Sun is shown as orange.

The image appears to be constructed from a single channel of data made by selecting the brightest pixels in a stack of two layers, one for 0.304 nm and one for 0.171 nm (so two UV channels).

How would you represent that visually?

How about showing the UV Sun as purple? I don't understand those who say that it would be horribly wrong to show the UV Sun as purple, but OK to show it as orange.

Our white Sun. The Sun isn't purple, of course, but it really isn't orange, either. Credit: ContemporAd/Getty Images

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Ann

Well, this is single-channel data. So the basic presentation would be grayscale. But then we'd only have 256 intensity levels on our screen, and our eye wouldn't distinguish them well. So a pseudocolor palette is chosen, which maps intensity to color and allows us to discriminate much more detail. The choice of palette depends on the object, but the most common is one that goes from black to white through orange. Because that is the one that generally maximizes our ability to resolve detail. Purples and blues are rarely used because our eyes have less resolution there, both in terms of intensity and distinguishing adjacent colors. The color choice here is not aesthetic, it is practical in terms of letting us see the most detail.
_

Ann wrote: ↑Sun May 26, 2024 2:52 pm How about showing the UV Sun as purple? I don't understand those who say that it would be horribly wrong to show the UV Sun as purple, but OK to show it as orange.

Here's another pseudocolor palette example, using today's Sun image. I think that, objectively, the palette they've chosen allows us to see more detail than either the original grayscale or a purple one.
_

Chris Peterson wrote: ↑Sun May 26, 2024 3:31 pm

Ann wrote: ↑Sun May 26, 2024 2:52 pm How about showing the UV Sun as purple? I don't understand those who say that it would be horribly wrong to show the UV Sun as purple, but OK to show it as orange.

Here's another pseudocolor palette example, using today's Sun image. I think that, objectively, the palette they've chosen allows us to see more detail than either the original grayscale or a purple one.
_

Click to view full size image

To me, the orange picture looks two-colored (orange, yellow and obviously white), whereas the purple one looks merely one-colored (purple and white).

Therefore, the orange/yellow picture does show more detail.

Ann

If one is going to map grayscale to a color scale, why limit ourselves to just purple or orange, when we could have both? The perceptually uniform colormap "plasma" or "inferno" freely available from matplotlib might look really good, and they seem appropriately named.

Ann wrote: ↑Sun May 26, 2024 2:30 pm
...So, yeah. It's an impressive picture, it really is.

And that's all I have to say about it!

Ann

Personally, I am particularly impressed by the dynamics of the event when you compare it with the size of the Earth. The effective discharge only took about 15 minutes. What tremendous energies and discharge speeds. Only 60 minutes later the event was over again. Crazy!

Observatory: PROBA2
INSTRUMENT: SWAP

florid_snow wrote: ↑Sun May 26, 2024 6:18 pm If one is going to map grayscale to a color scale, why limit ourselves to just purple or orange, when we could have both? The perceptually uniform colormap "plasma" or "inferno" freely available from matplotlib might look really good, and they seem appropriately named.

Yes, and many of these are used for scientific visualization. But they do create a very artificial appearance, which is why they are seldom used for "press release" type images targeting the general public. The palette used in today's image is pretty good for that purpose, though.

APOD, please, please, please, be more specific in description of each image!
After spending 5+ minutes of my time, I could not find how this image was obtained - what tool, method or interpretation was used? I guess the picture is made in UV? References to NASA etc do not help! This is very important, we don't want science (data or scientific artist) images to turn into AI art fake reality.

I'm an astrophysicist working in areas other than the Sun, which means the general public viewer won't even think about it.
It's not just about pretty pictures, it's about science, right?

kberzins wrote: ↑Sun May 26, 2024 11:53 pm APOD, please, please, please, be more specific in description of each image!
After spending 5+ minutes of my time, I could not find how this image was obtained - what tool, method or interpretation was used? I guess the picture is made in UV? References to NASA etc do not help! This is very important, we don't want science (data or scientific artist) images to turn into AI art fake reality.

I'm an astrophysicist working in areas other than the Sun, which means the general public viewer won't even think about it.
It's not just about pretty pictures, it's about science, right?

Usually, there is a link to the source of the image, commonly identified with the phrase "featured image". This APOD is no different, and if you follow that link you'll get to the source page, which includes information about the filters used (which I also noted above in the discussion about the color palette used here).