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SESK: Stuff Everyone Should Know · sesk.info/astro-solar-wind-speed

About how fast does the solar wind flow out from the Sun?

About 400 km per second, almost 1 million miles per hour.

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  1. About 4 km per second
  2. About 400 km per second ✔
  3. About 300,000 km per second

Why: The solar wind is a stream of charged particles, mainly protons and electrons. Corona gas is so hot and fast that solar gravity cannot hold it back. 300,000 km/s would be light speed.

Huh, didn't know that: The solar wind was first discovered by its effects on the charged tails of comets.

The dad joke
The solar wind never stops blowing. The Sun really needs to vent.
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References

Answer: About 400 km per second. The solar wind is a stream of charged particles, mainly protons and electrons. Corona gas is so hot and fast that solar gravity cannot hold it back. 300,000 km/s would be light speed.

  1. Astronomy 2e, 15.1 The Structure and Composition of the Sun openstax.org/books/astronomy-2e/pages/15-1-the-structure-and-composition-of-the-sun
    These particles flow outward from the Sun into the solar system at a speed of about 400 kilometers per second
    Checked 2026-10-10.

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