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Space · The Sun and its family

The solar wind

The Sun sends out more than light

Only spacecraft can see it

The solar wind
The breath of particles comes from the Sun and parts around the Earth, turned aside by the magnetic field.

The numbers

Speed near the Earth
250mi/s(400 km/s)120 to 560 mi/s (200 to 900 km/s)
Trip from the Sun to the Earth
4days2 to 9 days
Matter the Sun loses
880,000tons per second(800,000,000 kg/s)

How it happens, step by step

  1. The corona boils

    The Sun's outer atmosphere is extremely hot, hotter than the surface. Its particles move so fast that they do not stay bound.

  2. Particles escape

    The farther out you go, the weaker the Sun's gravity gets. At some point it cannot hold them, and the gas escapes.

  3. The breath spreads

    The flow travels in straight lines in every direction and is not turned aside by the planets. It carries the Sun's magnetic field.

  4. It hits the Earth

    Here it meets Earth's magnetic field, which steers it around the planet the way a ship's bow parts the water.

  5. In at the poles

    Only near the poles do the field lines open upward. There a few particles get in, and light up the auroras.

To get an idea

Sunlight gets here in eight minutes; the breath of particles takes days.

The Sun loses matter all the time, but compared with its mass it is a loss nobody would ever notice.

Fun facts

These are not in the book: there was no room on paper.

  1. Probes in the 1960s confirmed the idea by measuring the solar wind directly in space.

  2. The breath is faster than the escape speed of any planet, Jupiter included: it is never captured.

  3. The solar wind carries the Sun's magnetic field with it and stretches it across the whole Solar System.

  4. In Finland, scientists are studying an electric sail that would use this breath to push probes along.

  5. Its speed and its temperature change over time, following the Sun's eleven-year cycle.

  6. The Sun's outer atmosphere reaches about two million degrees Fahrenheit, far hotter than the surface below.

Test yourself

The first question is the one printed under the QR code, with the answer the book did not give. The other four only exist here.

Question 1 of 5★ is the one from your book

What is the solar wind?

Question 2 of 5

How did people figure out it existed?

Question 3 of 5

What protects us from the solar wind?

Question 4 of 5

Where do the particles manage to get in?

Question 5 of 5

How long does it take to arrive from the Sun?

Riddles

I leave the star that warms you and I never stop, in any direction. I do not move leaves, because where I pass there is no air, and yet I blow comet tails away. What am I?

People discovered me without seeing me, by looking at which way a comet's tail pointed. A man wrote it down in 1958, and the journal said no. What am I?

Against the Earth I can do nothing, because an invisible field splits me in two and sends me off to the side. Only near the poles can I get in, and then I turn on the lights. What am I?

Try it yourself

Activity 1

Bring a magnet near a compass and watch the needle swing. Earth's magnetic field does the same thing with the particles coming from the Sun.

Activity 2

Look online for a space weather forecast. It is the weather report for this breath, and people who send satellites into orbit really use it.

The words

plasma
A gas so hot that its particles carry an electric charge.
Earth's magnetic field
The invisible shield that turns aside the particles coming from the Sun.

Sources: Wikidata (Q79833), Wikipedia (Vento solare).