NASA spacecraft ‘touches’ the Sun for the first time ever

Re:NASA spacecraft ‘touches’ the Sun for the first time ever by l0b0 on Wednesday December 15, 2021 @02:00AM (#29562907)

From the article:

  > A NASA spacecraft has entered a previously unexplored region of the Solar System — the Sun’s outer atmosphere, or corona. 

  > The mission’s closest approach is scheduled for 2025 at a distance of just 6.2 million kilometres from the solar surface, well within the orbit of Mercury.

From the paper, it looks like the closest approach was

  > 18.4 solar radii (R⊙ ≡ 6.95 × 10⁵ km) from the center of the Sun

Wait, what? NASA says[1] the corona extends 5 million km, so 6.2 million km would be outside the corona. 18.4 × 6.95 × 10⁵ = 12.788 million km, which is more than twice the quoted number. And according to Wikipedia[2], Mercury's orbit is ~58 million km from the sun. So it's already well within that orbit. I've had a couple beers, but I didn't think I was that drunk already. What's going on?

[1] https://www.nasa.gov/content/goddard/nasas-stereo-maps-much-...

[2] https://en.wikipedia.org/wiki/Mercury_(planet)

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Re:NASA spacecraft ‘touches’ the Sun for the first time ever by steventharlow on Wednesday December 15, 2021 @02:26AM (#29563022)

For one, the NASA article says 5 million miles (12 solar radii), not kilometers. So it's actually about 2/3 the quoted number.

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Re:NASA spacecraft ‘touches’ the Sun for the first time ever by kwhitefoot on Wednesday December 15, 2021 @04:28AM (#29563727)

Doesn't NASA have some sort of educational duty? Surely they should be using SI units always so as to avoid exactly this kind of confusion.

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Re:NASA spacecraft ‘touches’ the Sun for the first time ever by nine_k on Wednesday December 15, 2021 @10:11AM (#29566982)

I'd rather have them always use both units, so that people would eventually learn intuitively, by example, what a km is relayed to a mile, or a kg to a pound, etc.

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Re:NASA spacecraft ‘touches’ the Sun for the first time ever by kwhitefoot on Wednesday December 15, 2021 @02:14PM (#29570335)

Yes, but the primary units should always be SI. They can put the US Customary units in brackets after.

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Re:NASA spacecraft ‘touches’ the Sun for the first time ever by dataflow on Wednesday December 15, 2021 @02:17AM (#29562974)

I think the 5 million km figure is just an order-of-magnitude/ballpark estimate, not something precise.

"The corona starts at 10,000 kilometers and extends out to about 10 million kilometers, where the gas finally escapes the sun's gravity and becomes part of the solar wind." [1]

[1] https://www.scientificamerican.com/article/i-read-that-the-s...

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Re:NASA spacecraft ‘touches’ the Sun for the first time ever by ceejayoz on Wednesday December 15, 2021 @09:59AM (#29566797)

> NASA says[1] the corona extends 5 million km, so 6.2 million km would be outside the corona.

The corona is not a perfect sphere. See the various pictures on https://en.wikipedia.org/wiki/Stellar_corona - it's irregular.

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Re:NASA spacecraft ‘touches’ the Sun for the first time ever by heyoni on Wednesday December 15, 2021 @02:17AM (#29562971)

I haven’t read any of this cause I’m on my phone but wouldn’t the closest approach occur in 2025? And isn’t the 6.95 quoted the closest distance so far?

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