Questions About the Sun

[Fishlore]

I have two hypothetical questions.

1.
Let's say a sunspot was born on the sun, but not yet viewable from Earth. Due to the sun's rotation, how long would it take the sunspot to get from the very edge of the sun, where it is first visible to us, to get all the way to the other edge of the sun and disappear from view? Would we view the sunspot moving right to left or left to right?

2.
Let's say the most massive CME in the history of the sun hit the Earth head on and we had some everyday items sitting unprotected on a desk when that happened. I'm under the impression that anything with a circuit would potentially be destroyed. What would happen to the following items.

Flashlight - would it still work?
Car battery - would it still hold a charge?
Not on a table, but what would happen to a jumbo jet flying overhead?

I'm trying to understand the implications of an EMP or major solar event.

Thank you for your time.

 

[MeteorWayne]

The answer to your first question is around 12 or 13 days at the most. The equator of the sun rotates at about 27 days, toward the poles it is faster. So the half of it we can see is about half of that.

Regarding the rst:

Flashlight - would it still work?---YES, no effect
Car battery - would it still hold a charge? YES-, no effect
Not on a table, but what would happen to a jumbo jet flying overhead? --- No problem, other than radio communication issues.

I'm trying to understand the implications of an EMP or major solar event.

Hope my answers help. This refers to a solar event, and EMP is a whole different beast. The effects of a solar event become important with long wires...many kilometers long. They act as an antenna and collect the energy from a solar event and shove it into systems that are not designed to handle the extra voltage and current.

 

[CalliArcale]

Excellent answers, MeteorWayne. The only part unanswered is whether we'd perceive a sunspot as travelling from left to right or right to left across the Sun. The answer, I'm afraid, is "it depends".

The sunspots will travel from west to east across the solar disk. But we the observers are standing on the rotating surface of the Earth at various different latitudes. We tend to interpret "left" and "right" on a celestial body in relation to what appears to be the top and bottom from our vantage point, and we tend to define "bottom" as "the bit closest to the horizon". And obviously that changes depending on the time of day, the season, and the observer's latitude. (Just watch the Moon; it's got a lot of great visual references to see which part seems to be "up" at any given time, and it's not always the same. The Moon's axis isn't changing, of course; just our position relative to it and the horizon.)

But, if you correct for all that and orient the image of the Sun such that its south pole is at the bottom, the sunspot will travel from left to right. This is how SOHO and other solar images released to the public are usually oriented.

A great reference for you is the website SpaceWeather.com. It features lots of sun pictures and a nearly-live image of the solar disk taken by SOHO. Visit it daily and you'll see sunspots creep across from left to right. Right now, the excitement is Sunspot 1019, a relatively modest spot, but a member of new Solar Cycle 24 and thus a harbinger of things to come. You can also get a firehose of image data from the SOHO website.

 

[Fishlore]

Thank you both very much for the answers and also for the links. I guess one of my biggest misunderstandings was that a massive CME impacting us and a detonated EMP behaved in similar ways. I'm beginning to see how their different, but would love more information. The reason I ask was one of those "Armageddon" type shows on the History channel talking about the sun and solar storms.


Thanks again!

 

[michaelmozina]

But, if you correct for all that and orient the image of the Sun such that its south pole is at the bottom, the sunspot will travel from left to right. This is how SOHO and other solar images released to the public are usually oriented.

As Wayne and Calli have pointed out, the overall rotation speed and direction of solar rotation dictates the time it takes for the sunspot to become visible on our side of the sun, and the direction it's traveling relative to Earth. Fortunately with STEREO images we can now see the active regions that drive these sunspot events well in advance. It's kind of interesting to see the active regions form in STEREO behind images and track them in the STEREO-Ahead images after they pass from SOHO's view. I tend to still find myself mostly using the SOHO images to get a feel for what's going on, but it's also interesting to watch the active regions coming over the horizon in STEREO images before they become visible in SOHO images. The 195A images in particular tend to be useful in 'predicting' the locating and formation of sunspots, but the correlation is not one to one. An area can be rather active in 195A, yet not form a sunspot at the surface of the photosphere, but all sunspots tend to be located near and around active regions.

STEREO images can be found here:

http://stereo-ssc.nascom.nasa.gov/browse

Relative to SOHO images, the STEREO-B (Behind) images show what is about to come over the horizon in SOHO images, and the STEREO-A (ahead) images tend to show the active regions after they rotate out of SOHO's view. STEREO adds a 3D ability to track active regions in real time, but SOHO images tend to be the ones I reference first thing in the morning to see what's going on on our side of the sun.

 

[MeteorWayne]

Thanx michael, good explanation of the the SOHO and STEREO images correlate in perspective.

 

[uncommon]

Binary?

Is it possible that the sun is one of a binary?
I've heard that the other 'sun' may be a brown color (due to it's imminent death)
and difficult or impossible to see.

 

[Saiph]

the sun is most definetly not part of a binary, near far, large small, bright or dim.

We'd have seen it by now.

 

[CalliArcale]

Also, brown dwarfs aren't really old stars; they're very small ones. In fact, it's debatable whether or not they actually qualify as "stars", since they are too small to have self-sustaining nuclear fusion going on at their cores. They're the fuzzy area between "stars" and "planets", and it's probably just as fair to think of them as really big gas giants.

I've heard it suggested that the red dwarf Barnard's Star could be a distant companion of our Sun, but it's not a very popular idea because it has very little evidence to support it.

The chance of the Sun having an undiscovered brown dwarf companion is nonzero, but extremely small given how intensively the outer solar system is being searched. Right now, astronomers are excited when they find something half the size of Pluto out there; if there was a brown dwarf out there, it's hard to imagine how they would have missed it unless it's so far out that it's not even orbiting our Sun.

 

[williammook]

I have two hypothetical questions.

1.
Let's say a sunspot was born on the sun, but not yet viewable from Earth. Due to the sun's rotation, how long would it take the sunspot to get from the very edge of the sun, where it is first visible to us, to get all the way to the other edge of the sun and disappear from view? Would we view the sunspot moving right to left or left to right?

2.
Let's say the most massive CME in the history of the sun hit the Earth head on and we had some everyday items sitting unprotected on a desk when that happened. I'm under the impression that anything with a circuit would potentially be destroyed. What would happen to the following items.

Flashlight - would it still work?
Car battery - would it still hold a charge?
Not on a table, but what would happen to a jumbo jet flying overhead?

I'm trying to understand the implications of an EMP or major solar event.

Thank you for your time.

The sun rotates with a speed that varies with latitutde because it isn't a solid surface, but a plasma.

http://en.wikipedia.org/wiki/Solar_rotation

At the equator the solar rotation period is 24.47 days. This is the sidereal rotation period. It is measured relative to the stars.

The synodic rotation period is 26.24 days, which is the time for a fixed feature on the sun to rotate to the same apparent position as viewed from Earth.

Since your question asked about the spot appearing on the sun at one side of the disk and disappearing on the other side, as viewed from Earth you're asking about a synodic observation.

Since the sun rotates in the same direction as the Earth moves around the sun, the synodic period is longer because the sun must rotate an extra amount due to the motion of the earth.

One rotation is 360 degrees nominally. To go from one side of the solar disk to the other means the sunspot must travel 180 degrees.

Not only does the synodic period vary with latitude (most sunspots occur at 26 degrees from the equator, but is varies with Earth's orbital speed. Orbital speed varies by time of year according to Kepler's laws. If the rotation as viewed from earth took 28 days - it would take 14 days for a sunspot to traverse the solar disk.

The direction of the sunspot would be parallel to the plane of rotation. This plane is inclined to the orbital plane of Earth - tht plane of theEarth's orbit is also called the Ecliptic. For this reason as the Earth orbits the Sun is precesses - or nods as we rise above the rotational plane or fall below it.

http://www.springerlink.com/content/v0m154n57l616k75/


To answer your question, get a small telescope and project the image of the sun onto a white piece of cardboard - do you have an erecting lens? If so, you'll get something like this

http://solar.physics.montana.edu/ypop/C ... /Rotation/

At noon lay down on a beach with your head oriented parallel with the sun's rotation - shown in the last URL. Your head will be pointing within 23 degreess of North (depending on year/)

Sunspots come from the left (your east the sun's west) and move to the right (your west the sun's east) This isn't mysterious, its what happens when you face someone - an audience and an actor on stage - stage left is different from left for this reason.

At noon the Earth is moving to your right from your left - within 23 degrees (the Earth's rotation is tilted 23 degrees relative to the ecliptic.

 

[mmrbrownn77777]

I just registered to the site. There are a lot of information right here that I have been interested for some time now. How many satellites/heavenly bodies in our galaxy that is just like our sun?

 

[3488]

I've heard it suggested that the red dwarf Barnard's Star could be a distant companion of our Sun, but it's not a very popular idea because it has very little evidence to support it.

The chance of the Sun having an undiscovered brown dwarf companion is nonzero, but extremely small given how intensively the outer solar system is being searched. Right now, astronomers are excited when they find something half the size of Pluto out there; if there was a brown dwarf out there, it's hard to imagine how they would have missed it unless it's so far out that it's not even orbiting our Sun.

Hi Calli,

IMHO Barnards Star is not a companion to the Sun. At just over 6 LY away, it is far beyond the Sun's Hill Sphere. Also Barnards Star appears o be far older than the Sun, approx 12 GYO, as against our Sun's 4.6 GYO, nearly three times our Sun's age (so the two could not have formed together at least).

Another clue is the fact that Barnards Star is quiet, only the odd flare episode, the most recent in July 1998 & also the very slow 130 day rotation period of the Red Dwarf. Not as slow as that of the red giants Arcturus (approx 18 Months) or Aldebaran (two years), but still quiet slow as compared to the Sun.

Interesting subject.

Also I agree with you regarding the doubts of a companion Brown Dwarf. I do not think the Sun has one either. Some time back there was speculation of a very distant massive object, in the constellation of Delphinus, near the border with Equuleus (based on purported slight pertubations of long period comets towards that point), but there is no such object there. As a star, I think the Sun is alone. Could be wrong, but so far there is no evidence to support the existence of a companion star to our Sun.

Andrew Brown.

 

[MeteorWayne]

mmrbrownn77777

Welcome to Space.com!!

The answer to your question is hundreds of millions to billions, depending on exactly how you define "just like our sun".

 

[williammook]

What's the difference between the Hill Sphere and Sphere of influence (SOI)? Both are part of a 3 body problem. If you place a massless fiduciary observer (FIDO) at arbitrary distances from Sol aren't you asking when does the sun's influence no longer dominate motion? Wouldn't this be near the halfway point between Sol and the nearest stars? That's 2.2 light years. Also if you track back the proper motions of stars in time, do any interact strongly with the sun? These seem relevant to the earlier question - though I tend to agree that 8 light years is likely not to be correlated in any way with Sol, but I can't a-priori reject the notion without looking at the details.

 

[CalliArcale]

IMHO Barnards Star is not a companion to the Sun. At just over 6 LY away, it is far beyond the Sun's Hill Sphere. Also Barnards Star appears o be far older than the Sun, approx 12 GYO, as against our Sun's 4.6 GYO, nearly three times our Sun's age (so the two could not have formed together at least).

Oh, I agree; I just mentioned it because it's the closest thing I've ever seen to the idea of the Sun being part of a binary star system, and even that isn't very plausible.