Starship Asterisk*

SDO s Multiwavelength Sun

Explanation: Today, the solstice is at 17:11 Universal Time, the Sun reaching the southernmost declination in its yearly journey through planet Earth's sky. The December solstice marks the astronomical beginning of winter in the northern hemisphere and summer in the south. To celebrate, explore this creative visualization of the Sun from visible to extreme ultraviolet wavelengths, using image data from the orbiting Solar Dynamics Observatory (SDO). Against a base image made at a visible wavelengths, the wedge-shaped segments show the solar disk at increasingly shorter ultraviolet and extreme ultraviolet wavelengths. Shown in false-color and rotating in a clockwise direction, the filters decrease in wavelength from 170 nanometers (in pink) through 9.4 nanometers (green). At shorter wavelengths, the altitude and temperature of the regions revealed in the solar atmosphere tend to increase. Bright at visible wavelengths, the solar photosphere looks darker in the ultraviolet, but sunspots glow and bright plasma traces looping magnetic fields. Watch the filters sweep around the solar disk in this animation of SDO's multiwavelength view of the Sun.

<< Previous APOD

This Day in APOD

Next APOD >>

[/b]

That video in different wavelengths is a good representation of why different filters are used to view different aspects of astronomical things.

Interesting wavelength display/presentation.
Can we assume that higher temps produce shorter wavelengths then ??

In some parts of the Southern Hemisphere, summer officially began on the 1st December.
In Australia at least.

That spambot filter is getting quite challenging, are the spambots getting smarter ?

Merry Xmas to all, although we are not quite there yet.

So why is the visible-light portion of the Sun shown in false color?

Cousin Ricky wrote:
So why is the visible-light portion of the Sun shown in false color?

So that you don't go blind.

neufer wrote:

---

The visible spectrum in that diagram is way too broad, covering most of the range between 1 nm and 1 µm. It should actually cover 380 nm to something over 700 nm, or a fraction of the range between 1 µm and the tick mark above it (100 nm). I don't normally expect the government to tell the truth, but I figured NASA would be an exception.

Cousin Ricky wrote:The visible spectrum in that diagram is way too broad, covering most of the range between 1 nm and 1 µm. It should actually cover 380 nm to something over 700 nm, or a fraction of the range between 1 µm and the tick mark above it (100 nm). I don't normally expect the government to tell the truth, but I figured NASA would be an exception.

It isn't clear what the credit for NASA is in that image. It could be just one of the little sun images. I tried an image search on it and could only find it at the ISRO website so I think the whole chart was not created by anyone at NASA.

The start of so called "meteorological seasons" are aligned with the first day of December, March, June and September.

The start of so called "astronomical seasons" are aligned with the December Solstice, March Equinox, June Solstice and September Equinox.

In pure terms of solar angles of incidence on the Earth, the solstices and equinoxes would mark the middle of each season. However, the effects of the air, ocean and land on Earth, combine to cause a thermal lag, such that temperatures tend to lag behind what the solar angle might otherwise indicate. In some parts of the world, "astronomical seasons" are considered to be a better fit to the measured thermal lag, and in other parts -- especially those more regulated by the oceans -- "meteorological seasons" are preferred.

Happy Solstice!

I'd simply like to note what an exquisitely beautiful image this is - especially in the animated version found by following the last link in the text. It quite took my breath away.

Happy Solstice, everyone.
M

To Genna Duberstein at NASA:

Hi Genna

http://svs.gsfc.nasa.gov/goto?11385

APOD directed me to your animation. Two things I’d like to say.

One is, how very much I appreciate your outreach and the effort put into making these images accessible and understandable. Hence this e-mail.

Two is, this animation is just (pedagogically) terrible. Just as I’m getting the idea of comparing a particular surface feature under different wavelengths, the shot changes arbitrarily to a completely disconnected shot. I then have to try again, but that shot lasts for what seems like 3 nanoseconds before yet another completely different shot (different colour, frame, size, focus, movement; permute all four possibilities) disrupts me. Argh! There is nothing educational about this, it is like being in a disco with random lights and a total inability to focus thoughtfully on anything.

This is a really creative display!

geckzilla wrote:
It isn't clear what the credit for NASA is in that image. It could be just one of the little sun images. I tried an image search on it and could only find it at the ISRO website so I think the whole chart was not created by anyone at NASA.

It is clearly credited to Nasa:

Nasa : a Brazilian association football player
Nasa : a Native American people of Colombia
Nasa : a mountain in the north of Sweden, near Arjeplog
Nasa : a genus of plants in the family Loasaceae

This display would be what is called an 'instructable' and serve very nicely in a lecture on the light our planet evolved with. It very nicely shows the incredible brevity of our light sensing ability and should be taught by an owl or an eagle whose light sensing abilities exceed primate skills.

I don't know what was in those brownies she gave me for breakfast on that reservation west of Santa Fe, but that's what I saw a half hour after eating them.

The Sun has many facets, and you need multiple ways to study it....

:---[===] *

Boomer12k wrote:
The Sun has many facets, and you need multiple ways to study it....

:---[===] *

Nitpicker wrote:...

In pure terms of solar angles of incidence on the Earth, the solstices and equinoxes would mark the middle of each season. However, the effects of the air, ocean and land on Earth, combine to cause a thermal lag, such that temperatures tend to lag behind what the solar angle might otherwise indicate. In some parts of the world, "astronomical seasons" are considered to be a better fit to the measured thermal lag, and in other parts -- especially those more regulated by the oceans -- "meteorological seasons" are preferred.

Happy Solstice!

Thank you, and a belated happy Solstice to all.

It makes the most sense to me to consider the solstices and equinoxes as the midpoints of their respective seasons. And we here in the northern hemisphere still refer to this time of year as midwinter, and the longest days as midsummer.

I measured my shadow at solar noon yesterday, three hours after the moment of solstice. I'm 169 cm tall, and my shadow was 330 cm long. What was the height of the Sun in the sky? What is my latitude? And how do you calculate these numbers? I've tried to brush up my long-forgotten trigonometry, but I've given up for now. I expect there's a mathematician here for whom these are easy questions. I'm planning to try to measure my shadow when the Sun is at each multiple of 30 degrees ecliptic longitude and see what pattern emerges.

Anthony Barreiro wrote:It makes the most sense to me to consider the solstices and equinoxes as the midpoints of their respective seasons. And we here in the northern hemisphere still refer to this time of year as midwinter, and the longest days as midsummer.

I don't think you can speak for the entire population of the northern hemisphere, Anthony.

Those terms are rarely used here in eastern Canada, and certainly never in relation to the solstices and equinoxes. Maybe you'd hear the occasional spaced-out astrologer use the terms, but not most folk.

Rob

rstevenson wrote:

Anthony Barreiro wrote:It makes the most sense to me to consider the solstices and equinoxes as the midpoints of their respective seasons. And we here in the northern hemisphere still refer to this time of year as midwinter, and the longest days as midsummer.

I don't think you can speak for the entire population of the northern hemisphere, Anthony.

Those terms are rarely used here in eastern Canada, and certainly never in relation to the solstices and equinoxes. Maybe you'd hear the occasional spaced-out astrologer use the terms, but not most folk.

Rob

Hi Rob. Seasons greetings to you and yours, and best wishes for a good new year, however you mark its turning.

Anthony Barreiro wrote: I measured my shadow at solar noon yesterday, three hours after the moment of solstice. I'm 169 cm tall, and my shadow was 330 cm long. What was the height of the Sun in the sky? What is my latitude? And how do you calculate these numbers? I've tried to brush up my long-forgotten trigonometry, but I've given up for now. I expect there's a mathematician here for whom these are easy questions. I'm planning to try to measure my shadow when the Sun is at each multiple of 30 degrees ecliptic longitude and see what pattern emerges.

Based on your measurements, the elevation of the Sun was:
arctan(169/330) = 27.1°

From the equator at the solar noon nearest the solstice, the elevation of the Sun would have been 66.6°.

The difference gives you your latitude, 39.5°. This is ~200km further North than San Fran, so either you are currently out of town, or there are some errors in your measurements.

Nitpicker wrote:

Anthony Barreiro wrote: I measured my shadow at solar noon yesterday, three hours after the moment of solstice. I'm 169 cm tall, and my shadow was 330 cm long. What was the height of the Sun in the sky? What is my latitude? And how do you calculate these numbers? I've tried to brush up my long-forgotten trigonometry, but I've given up for now. I expect there's a mathematician here for whom these are easy questions. I'm planning to try to measure my shadow when the Sun is at each multiple of 30 degrees ecliptic longitude and see what pattern emerges.

Based on your measurements, the elevation of the Sun was:
arctan(169/330) = 27.1°

From the equator at the solar noon nearest the solstice, the elevation of the Sun would have been 66.6°.

The difference gives you your latitude, 39.5°. This is ~200km further North than San Fran, so either you are currently out of town, or there are some errors in your measurements.

Thanks! Arctangent! I knew it had to do with tangent, but that was as far as my tired old brain got.

Measurement error, I'm sure. I may not have been standing exactly perpendicular to the sidewalk, the sidewalk might not be perfectly level, and I could only judge the top of my shadow approximately. I may have failed as a navigator, but if I do the same measurement each month at the same place, wearing the same shoes and no hat, the errors should all cancel out and I should get an interesting curve.

Anthony Barreiro wrote:
The sidewalk might not be perfectly level.

They have level sidewalks in San Francisco

neufer wrote:

Anthony Barreiro wrote:
The sidewalk might not be perfectly level.

They have level sidewalks in San Francisco

I live in the Mission district which is an old alluvial plain between the hills and the bay. The padres built Mission Dolores here because the land was flat and there was a year-round creek and spring-fed ponds. Unfortunately Mission Creek and the ponds have all been paved over. But when we get a good rain, they make their presence known.

But are there any turtles there?