APOD: A February without Sunspots (2019 Mar 06)

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Expand view Topic review: APOD: A February without Sunspots (2019 Mar 06)

Re: APOD: A February without Sunspots (2019 Mar 06)

by BDanielMayfield » Sat Mar 09, 2019 12:05 am

geoffrey.landis wrote: Fri Mar 08, 2019 7:23 pm True. But over the five billion years that the sun has been around, even a very very slight self interaction would equilibrate the concentration.
What do you mean by this?

I used to wonder about how much of the Sun's mass, the Earth's mass, etc. might be dark matter, but Chris' logical points about momentum put my mind at ease about these questions.

If a significant amount of the mass internal to stars is dark matter it throws off the equations of state re the conditions inside stars and therefore stellar lifetimes. Simply stated, stars can't run on dark matter, so if their cores aren't fully normal matter they couldn't last as long as they are observed to be doing universally.

Bruce

Re: APOD: A February without Sunspots (2019 Mar 06)

by Chris Peterson » Fri Mar 08, 2019 7:29 pm

geoffrey.landis wrote: Fri Mar 08, 2019 7:23 pm True. But over the five billion years that the sun has been around, even a very very slight self interaction would equilibrate the concentration.
Maybe... depending on the kind of interaction. If it's gravity alone, the result could be dilution, as well, like the way that globular clusters evaporate. The transfer of orbital angular momentum concentrates some mass, but also scatters some. So any concentration may be paired with an overall mass reduction.

Re: APOD: A February without Sunspots (2019 Mar 06)

by geoffrey.landis » Fri Mar 08, 2019 7:23 pm

True. But over the five billion years that the sun has been around, even a very very slight self interaction would equilibrate the concentration.

Re: APOD: A February without Sunspots (2019 Mar 06)

by Droffarc » Fri Mar 08, 2019 2:53 pm

Just what are sunpots please (see index) . I know about sunspots :?: :?:

Re: APOD: A February without Sunspots (2019 Mar 06)

by Chris Peterson » Thu Mar 07, 2019 7:35 pm

geoffrey.landis wrote: Thu Mar 07, 2019 7:05 pm
Chris Peterson wrote: Wed Mar 06, 2019 5:21 pm ... There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.)
Dark matter accumulates inside a gravity well (since it has mass), and the amount by which it is concentrated in the gravity well depends on the mass and temperature (according to the law of Jeans' escape). So, yes, dark matter would be somewhat concentrated inside the sun. Different models predict different temperatures-- cold dark matter, warm dark matter, and hot dark matter are all models still in contention.

However, the density of dark matter is so low, and its interaction with ordinary matter so extraordinarily low, it's unlikely to have any significant effect (it only plays a role in galactic rotation because even a very low density of matter adds up over volumes of space measured in trillions of cubic parsecs).
In the absence of interaction with other matter, it is unclear why dark matter would concentrate in an gravity well. It might orbit around a gravity well, but would not necessarily concentrate. To do that, it would required some mechanism for transferring momentum. With ordinary matter that's mostly via electromagnetic interactions. Of course, we don't know how dark matter interacts with itself (other than straightforward gravitational interaction), so that's a big unknown in terms of hydrodynamic equivalents in dark matter.

Re: APOD: A February without Sunspots (2019 Mar 06)

by geoffrey.landis » Thu Mar 07, 2019 7:05 pm

Chris Peterson wrote: Wed Mar 06, 2019 5:21 pm ... There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.)
Dark matter accumulates inside a gravity well (since it has mass), and the amount by which it is concentrated in the gravity well depends on the mass and temperature (according to the law of Jeans' escape). So, yes, dark matter would be somewhat concentrated inside the sun. Different models predict different temperatures-- cold dark matter, warm dark matter, and hot dark matter are all models still in contention.

However, the density of dark matter is so low, and its interaction with ordinary matter so extraordinarily low, it's unlikely to have any significant effect (it only plays a role in galactic rotation because even a very low density of matter adds up over volumes of space measured in trillions of cubic parsecs).

Re: APOD: A February without Sunspots (2019 Mar 06)

by orin stepanek » Thu Mar 07, 2019 12:02 am

:shock: Cool period on the sun! 8-)

Re: APOD: A February without Sunspots (2019 Mar 06)

by Chris Peterson » Wed Mar 06, 2019 11:06 pm

Fred the Cat wrote: Wed Mar 06, 2019 8:10 pm
Chris Peterson wrote: Wed Mar 06, 2019 5:21 pm
Fred the Cat wrote: Wed Mar 06, 2019 5:09 pm If dark matter is involved in solar cycles mapping it, via its effects, would seem to be the best plan to elucidate a scheme that may explain how it will impact Earth and all its inhabitants. :idea:

Whatever the mechanism, detected by geology or sunspots, solar cycles point to something remarkable. 8-)
There is no reason to believe that dark matter is involved in the solar cycle. There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.) While there is much about the solar cycle that is not understood, its basic relationship with the Sun's magnetic field (which largely eliminates any dark matter effect) is well understood.

There is little evidence that solar cycles, including extreme minimums or maximums, play a very large role in Earth's climate. Indeed, there is some evidence that they do not.
But aren't deeper ( Milankovitch Cycles) sun-related cycles reflected in Earth's geology by climate change?
But these cycles are the product of ordinary orbital dynamics in a multiple body system. Dark matter is not needed to explain them.

Re: "Pictured in inverted black & white"

by MarkBour » Wed Mar 06, 2019 10:58 pm

alanfgag wrote: Wed Mar 06, 2019 10:34 pm Below you can see the two original images that were used to make this comparison of an active and a quiet sun ...
Thanks for posting those! The originals are very nice!

For those who wanted a more current image, pertaining to the "spotless February" story, here is a link:
https://sdo.gsfc.nasa.gov/gallery/potw/item/952
Now that pic is very plain.

Re: "Pictured in inverted black & white"

by alanfgag » Wed Mar 06, 2019 10:34 pm

Chris Peterson wrote: Wed Mar 06, 2019 4:31 pm
geoffrey.landis wrote: Wed Mar 06, 2019 4:02 pm I'm puzzled. Why are the solar prominences bright, instead of dark, if it's inverted?
And why is the sun surrounded by a bright halo in the image on the right, but not on the left?
The image is not inverted, just the face of the Sun. Alan's workflow involves masking and selective inversion.

Not sure about the difference in the halos. Maybe his processing method has changed a little over the years, or maybe it's a consequence of bringing up the levels just outside the limb to make more visible the much fainter prominences that we have at solar minimum.
Thanks for the explanation, Chris. For the sky background, the tonality in the original data is black. The solar filter allows only a very small percentage of the sun's energy to pass so the sky background is not illuminated at all. In processing the images, I have used a gradient to add back some sky light (and in the original images, color). The techniques I have used for this have varied over the years. Below you can see the two original images that were used to make this comparison of an active and a quiet sun.

2018 http://www.avertedimagination.com/img_p ... lues2.html

2012 http://www.avertedimagination.com/img_p ... y_sun.html

Re: APOD: A February without Sunspots (2019 Mar 06)

by Fred the Cat » Wed Mar 06, 2019 8:10 pm

Chris Peterson wrote: Wed Mar 06, 2019 5:21 pm
Fred the Cat wrote: Wed Mar 06, 2019 5:09 pm If dark matter is involved in solar cycles mapping it, via its effects, would seem to be the best plan to elucidate a scheme that may explain how it will impact Earth and all its inhabitants. :idea:

Whatever the mechanism, detected by geology or sunspots, solar cycles point to something remarkable. 8-)
There is no reason to believe that dark matter is involved in the solar cycle. There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.) While there is much about the solar cycle that is not understood, its basic relationship with the Sun's magnetic field (which largely eliminates any dark matter effect) is well understood.

There is little evidence that solar cycles, including extreme minimums or maximums, play a very large role in Earth's climate. Indeed, there is some evidence that they do not.
The simplest answer usually turns out correct so by reading I ''a'muse" my head out loud. As always, I appreciate your thoughts on these topics. I didn't realize there was such a hullabaloo. :?

But aren't deeper ( Milankovitch Cycles) sun-related cycles reflected in Earth's geology by climate change?

Re: APOD: A February without Sunspots (2019 Mar 06)

by RJN » Wed Mar 06, 2019 7:10 pm

BDanielMayfield wrote: Wed Mar 06, 2019 6:59 pm
De58te wrote: Wed Mar 06, 2019 10:20 am If the sunspots last month were zero, then why show a photo from August 2018, instead of last month's?
Good catch, and good question.

My guesses, one spotless Sun photo is as good as another, and/or they didn't think anyone would notice.
Good question. Typically, APOD will run images that are submitted rather than compose its own. It would have been nice if the photographer submitted an image that included a spotless Sun from February, but he did not. No one did. So we went with the best and most educational image that we had.

- RJN

Re: APOD: A February without Sunspots (2019 Mar 06)

by BDanielMayfield » Wed Mar 06, 2019 6:59 pm

De58te wrote: Wed Mar 06, 2019 10:20 am If the sunspots last month were zero, then why show a photo from August 2018, instead of last month's?
Good catch, and good question.

My guesses, one spotless Sun photo is as good as another, and/or they didn't think anyone would notice.

Re: APOD: As the Sun Turns ...

by Chris Peterson » Wed Mar 06, 2019 6:51 pm

BDanielMayfield wrote: Wed Mar 06, 2019 6:41 pm
Chris Peterson wrote: Wed Mar 06, 2019 6:15 pm Yes, but that doesn't mean that the Sun didn't have any sunspots during that 28 day month. It's quite common for sunspots to last only a few days. It's even possible (although very unlikely) that the Sun had sunspots every single day of February!
Yikes. We've been trying to stamp out the "Dark side of the Moon" saying. Now you've raised the specter of the Dark Side of the Sun! :lol2:
There was a time period when the two STEREO spacecraft could see the entire Sun at the same time (including the Dark Side). I don't think we have anything in place right now that can do that, though.

Re: APOD: As the Sun Turns ...

by BDanielMayfield » Wed Mar 06, 2019 6:41 pm

Chris Peterson wrote: Wed Mar 06, 2019 6:15 pm Yes, but that doesn't mean that the Sun didn't have any sunspots during that 28 day month. It's quite common for sunspots to last only a few days. It's even possible (although very unlikely) that the Sun had sunspots every single day of February!
Yikes. We've been trying to stamp out the "Dark side of the Moon" saying. Now you've raised the specter of the Dark Side of the Sun! :lol2:

Re: APOD: As the Sun Turns ...

by Chris Peterson » Wed Mar 06, 2019 6:15 pm

BDanielMayfield wrote: Wed Mar 06, 2019 6:08 pm
Chris Peterson wrote: Wed Mar 06, 2019 3:35 pm
De58te wrote: Wed Mar 06, 2019 10:20 am Could it be that the sunspots are just on the side facing away from the Earth?
Sure. But the convention for counting sunspots does not consider whether there are any on the opposite side. The count is based on what is observed on the visible face.
Consider also the Sun's rotation:
The Sun rotates faster at its equator than at its poles. This differential rotation is caused by convective motion due to heat transport and the Coriolis force due to the Sun's rotation. In a frame of reference defined by the stars, the rotational period is approximately 25.6 days at the equator and 33.5 days at the poles. Viewed from Earth as it orbits the Sun, the apparent rotational period of the Sun at its equator is about 28 days.
So last month as the sun turned we got to see both sides during a 28 day month.
Yes, but that doesn't mean that the Sun didn't have any sunspots during that 28 day month. It's quite common for sunspots to last only a few days. It's even possible (although very unlikely) that the Sun had sunspots every single day of February!

Re: APOD: As the Sun Turns ...

by BDanielMayfield » Wed Mar 06, 2019 6:08 pm

Chris Peterson wrote: Wed Mar 06, 2019 3:35 pm
De58te wrote: Wed Mar 06, 2019 10:20 am Could it be that the sunspots are just on the side facing away from the Earth?
Sure. But the convention for counting sunspots does not consider whether there are any on the opposite side. The count is based on what is observed on the visible face.
Consider also the Sun's rotation:
The Sun rotates faster at its equator than at its poles. This differential rotation is caused by convective motion due to heat transport and the Coriolis force due to the Sun's rotation. In a frame of reference defined by the stars, the rotational period is approximately 25.6 days at the equator and 33.5 days at the poles. Viewed from Earth as it orbits the Sun, the apparent rotational period of the Sun at its equator is about 28 days.
So last month as the sun turned we got to see both sides during a 28 day month.

Re: APOD: A February without Sunspots (2019 Mar 06)

by Chris Peterson » Wed Mar 06, 2019 5:21 pm

Fred the Cat wrote: Wed Mar 06, 2019 5:09 pm If dark matter is involved in solar cycles mapping it, via its effects, would seem to be the best plan to elucidate a scheme that may explain how it will impact Earth and all its inhabitants. :idea:

Whatever the mechanism, detected by geology or sunspots, solar cycles point to something remarkable. 8-)
There is no reason to believe that dark matter is involved in the solar cycle. There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.) While there is much about the solar cycle that is not understood, its basic relationship with the Sun's magnetic field (which largely eliminates any dark matter effect) is well understood.

There is little evidence that solar cycles, including extreme minimums or maximums, play a very large role in Earth's climate. Indeed, there is some evidence that they do not.

Re: APOD: A February without Sunspots (2019 Mar 06)

by Fred the Cat » Wed Mar 06, 2019 5:09 pm

If dark matter is involved in solar cycles mapping it, via its effects, would seem to be the best plan to elucidate a scheme that may explain how it will impact Earth and all its inhabitants. :idea:

Whatever the mechanism, detected by geology or sunspots, solar cycles point to something remarkable. 8-)

Re: "Pictured in inverted black & white"

by Chris Peterson » Wed Mar 06, 2019 4:31 pm

geoffrey.landis wrote: Wed Mar 06, 2019 4:02 pm I'm puzzled. Why are the solar prominences bright, instead of dark, if it's inverted?
And why is the sun surrounded by a bright halo in the image on the right, but not on the left?
The image is not inverted, just the face of the Sun. Alan's workflow involves masking and selective inversion.

Not sure about the difference in the halos. Maybe his processing method has changed a little over the years, or maybe it's a consequence of bringing up the levels just outside the limb to make more visible the much fainter prominences that we have at solar minimum.

"Pictured in inverted black & white"

by geoffrey.landis » Wed Mar 06, 2019 4:02 pm

I'm puzzled. Why are the solar prominences bright, instead of dark, if it's inverted?
And why is the sun surrounded by a bright halo in the image on the right, but not on the left?

Re: APOD: A February without Sunspots (2019 Mar 06)

by Joe25 » Wed Mar 06, 2019 3:55 pm

Now today's APOD is wonderful ! Terrific ! Totally gorgeous photos !!! And a worthy description/explanation !!! !!! Today's APOD is why we come here !!! Well Done !!! Keep up the Good Work, and don't let the Mainstream 'deep space' 'crackpot theories' take this place over ! Best, Joe25

Re: APOD: A February without Sunspots (2019 Mar 06)

by Chris Peterson » Wed Mar 06, 2019 3:35 pm

De58te wrote: Wed Mar 06, 2019 10:20 am Could it be that the sunspots are just on the side facing away from the Earth?
Sure. But the convention for counting sunspots does not consider whether there are any on the opposite side. The count is based on what is observed on the visible face.
Also is it a coincidence that some of the flares particularly the one at about 5 o'clock are in the same location as in 2012? Another one is at about 2 o'clock and another one at about 10:30. Could they be the same flares that have lasted for 6 years?
Keep in mind that the Sun has no stable longitude system. So nothing can be in the "same place" after a few rotations have scrambled things. There is a pattern of what latitude activity occurs at depending on the solar cycle. So yes, what you're seeing is just a coincidence of the time the images were made (and each would look different if they had been taken a day or two earlier or later). The areas of magnetic activity that produce sunspots and flares are short lived. Really big sunspots sometimes last long enough to make it around the back and return to visibility on the front (so hidden for about two weeks). A few historical examples are known of sunspots that persisted for months. But nothing will persist for half a solar cycle.

Re: APOD: A February without Sunspots (2019 Mar 06)

by Ann » Wed Mar 06, 2019 10:24 am

There was a year in the 1800s that was called "The year without a summer". But that was probably due to volcanoes spewing a lot of soot and smoke into the atmosphere, and it likely had little to do with the activity of the Sun.

Nevertheless... if the Sun is very quiet now, and temperatures on the Earth are still rising, that is not a good sign.

Ann

Re: APOD: A February without Sunspots (2019 Mar 06)

by De58te » Wed Mar 06, 2019 10:20 am

If the sunspots last month were zero, then why show a photo from August 2018, instead of last month's? Another question, I heard I believe as a layman that solar flares mostly happen above or near sunspots. Yet in the 2018 photo I can still see a few flares right on the limb of the Sun. Could it be that the sunspots are just on the side facing away from the Earth? Also is it a coincidence that some of the flares particularly the one at about 5 o'clock are in the same location as in 2012? Another one is at about 2 o'clock and another one at about 10:30. Could they be the same flares that have lasted for 6 years?

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