I understand that total eclipses are a fantastic time to study the sun's corona, and the reason for this is because the much brighter photosphere is blocked by the moon. But, couldn't the Parker solar probe, which is so much closer, and without an atmosphere, capture better data? And, I'm not sure if this should be its own question, but if there is still something unique about totality for solar physics, is there any way to position a probe so that it constantly experiences totality? Such as in Lagrange point L2 of some planet? If not, is there some way to get a probe where it experiences a lot of totality? Or is constantly traveling around earth every year and a half to study the corona through our atmosphere for a few minutes at a time the best it gets?
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$\begingroup$ Related: en.wikipedia.org/wiki/Coronagraph $\endgroup$– PM 2RingCommented May 5 at 7:53
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2$\begingroup$ Do you have examples of major scientific efforts taken to study anything about the sun during an eclipse in modern times? From what I understand, the existing satellites provide way more information now. As you pointed out getting intrumentation in the path of an eclipse, hoping the weather cooperates, only to get a few minutes of data every couple years, isn't that helpful. I believe most of the science done is either citizen science (reproducing what we already know), or studying the effects the eclipse has on the Earth. $\endgroup$– Greg MillerCommented May 5 at 15:10
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$\begingroup$ There's a lot of scientific research that's done during a total solar eclipse. But it does not study the Sun. Sounding rockets are launched to study Earth's ionosphere to see how it responds to the sudden lack of ionizing radiation. See for example NASA to Launch Sounding Rockets into Moon’s Shadow During Solar Eclipse and Why the thermal imaging of Mercury's surface requires a telescope on a jet flying through an eclipse? $\endgroup$– uhohCommented May 5 at 16:41
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$\begingroup$ and CNN's Why NASA is launching rockets into the solar eclipse path and Phys.org's NASA to launch sounding rockets into moon's shadow during solar eclipse which includes a cool video $\endgroup$– uhohCommented May 5 at 16:49
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1$\begingroup$ @PM2Ring That was actually going to be another question I had. Is there science that can be performed during totality in a way that coronagraphs do not allow? Or is a coronagraph the exact same thing as totality? $\endgroup$– Curious LaymanCommented May 5 at 23:25
2 Answers
It is true that many of the things that we used to use eclipses for can now be done from space, continuously.
Eclipses are still important because they are usually much more easily accessible than space. They happen right here on the surface, if you want to observe one, all you need is an aeroplane ticket. It's a lot less than a rocket!
That means that lots more and different people can be involved in observations, and with this you get repeatability and cross-checking. You can get amateurs confirming the relativistic displacement of stars due to the sun's gravity. You can use a wide range of heavyweight equipment to repeat the observations by spacecraft, and by repeating, confirm them. You can use eclipse timing to confirm and refine models of Earth's rotation and lunar perturbation.
So, it certainly is possible to observe the solar corona more easily from space, but that doesn't mean that observations can't be done from Earth, or that these have no value.
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1$\begingroup$ How about studies of "shadow bands"... Can't study those in space. Also my Earth rotatation timing examples $\endgroup$– James KCommented May 6 at 5:40
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1$\begingroup$ @CuriousLayman There's a number of biological/geological/atmospheric phenomenon (e.g. animal behavior or wind patterns) which can't be studied from space. There's probably no astronomical phenomenon which can be studied from earth during an eclipse that can't also be studied from LEO under the same eclipse. There are things which can be observed during an eclipse which are difficult or impossible to observe not during an eclipse, though there's ways (e.g. with a precisely sized metal plate) of effectively making artificial eclipses, though sun-moon interactions wouldn't come into play there. $\endgroup$– R.M.Commented May 6 at 17:34
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1$\begingroup$ "You can get amateurs confirming the relativistic displacement of stars due to the sun's gravity. " --- WHAT?? How can I do that? $\endgroup$– BЈовићCommented May 7 at 11:41
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2$\begingroup$ @BЈовић With today's optics, pretty much anyone can recreate Arthur Eddington's 1919 experiment that showed that Einstein was right and gravity can bend light. A lot of universities do it as a student project. Basically you're going to take a photo of the stars near the edge of the sun during the eclipse, then compare them to a photo of the same stars taken on any random night (ideally six months apart, I guess) and as you flip between them, you can see that the stars near the sun in the eclipse photo are out of place, which is due to their light being bent by the sun's gravity. $\endgroup$ Commented May 7 at 15:44
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2$\begingroup$ @BЈовић It's not as easy as Darth suggests. See the links from astronomy.stackexchange.com/questions/34830/… that is skyandtelescope.com/astronomy-news/… and skyandtelescope.org/sky-and-telescope-magazine/… and eclipse2017.nasa.gov/testing-general-relativity $\endgroup$– James KCommented May 7 at 16:47
"is there any way to position a probe so that it constantly experiences totality? Such as in Lagrange point L2 of some planet?"
Careful reading of your linked Wikipedia page shows that the Sun-Earth L2 experiences a constant annular eclipse that would make corona studies difficult to impossible.
The usual energy source for a long-duration satellite is solar panels. The downside of parking a satellite in the shadow of a planet should be obvious.
Finally, unlike L4 & L5, L2 is an "unstable point", meaning that objects placed there "tend to slide off".
"some planet" is, perhaps, a bit too vague a question as star systems come in all shapes and sizes.
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2$\begingroup$ Yes, L2 is unstable, but we can put a satellite into a halo / Lissajous orbit "near" L2 that doesn't require much fuel to maintain. The JWST is in such an orbit, but its distance from L2 is actually larger than the Earth-Moon distance. It varies from ~450000 km to 790000 km, (mean 635200 km). From JWST, the Earth's angular diameter is occasionally larger than the Sun's i.sstatic.net/itavE7aj.png but of course the JWST must never look towards the Sun! $\endgroup$– PM 2RingCommented May 5 at 22:24
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$\begingroup$ @PM2Ring Good to know. Thanks for that clarification. :-) The 3D math is beyond me, but, intuitively, I'd take this to mean that the OP's suggested satellite would spend only a small "percentage" of its time in totality. Even worse would be any haziness added by sunlight diffracting through the planet's (Earth's) atmosphere. $\endgroup$– user56535Commented May 5 at 22:33
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1$\begingroup$ Well, the JWST's halo orbit is never anywhere near the Earth-Sun line, so it can't experience totality. And as you mention, it would be bad for the solar power supply for such a satellite to be in shadow. You can see the JWST orbit in 3D, in a frame corotating with L2, using a script in my answer: astronomy.stackexchange.com/a/49616/16685 $\endgroup$– PM 2RingCommented May 5 at 23:02
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1$\begingroup$ @PM2Ring made my point. I was told that spacecraft can be put into pseudo-orbit where the craft requires occasional course corrections. As for the final bit "some planet" refers to the planets/planetesimals in our solar system. I am only concerned about our own solar system. $\endgroup$ Commented May 5 at 23:23
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$\begingroup$ @CuriousLayman Re: "other planets orbiting Sol" Gut reaction? Might be only possible with Venus. The formulas seem to be in Wikipedia to calculate the Sun-Venus L2 spot and the angles to both Venus and the Sun. My gut is telling me "yes, totality", but the degree of totality may exclude a large part of the "near surface" corona.) And, the diameter of the orbit around L2? And, what to do about the solar panels being unworkable... Then, there's that atmosphere problem, again. Luna is just an airless rock. Lucky for us!!
:-)$\endgroup$– user56535Commented May 7 at 10:14
