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

by l0b0 5y ago

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-larger-solar-atmosphere-than-previously-observed/ https://www.nasa.gov/content/goddard/nasas-stereo-maps-much-... [2] https://en.wikipedia.org/wiki/Mercury_(planet) https://en.wikipedia.org/wiki/Mercury_(planet)

heyoni 5y ago
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?
dataflow 5y ago
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-suns-surf/ https://www.scientificamerican.com/article/i-read-that-the-s...
steventharlow 5y ago
For one, the NASA article says 5 million miles (12 solar radii), not kilometers. So it's actually about 2/3 the quoted number.
- kwhitefoot 5y ago
  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.
  - nine_k 5y ago
    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.
    - kwhitefoot 5y ago
      Yes, but the primary units should always be SI. They can put the US Customary units in brackets after.
ceejayoz 5y ago
> 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 https://en.wikipedia.org/wiki/Stellar_corona - it's irregular.

by l0b0 5y ago

heyoni 5y ago

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?

dataflow 5y ago

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-suns-surf/ https://www.scientificamerican.com/article/i-read-that-the-s...

steventharlow 5y ago

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

kwhitefoot 5y ago
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.
- nine_k 5y ago
  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.
  - kwhitefoot 5y ago
    Yes, but the primary units should always be SI. They can put the US Customary units in brackets after.

ceejayoz 5y ago

> 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 https://en.wikipedia.org/wiki/Stellar_corona - it's irregular.