Flare
Flares are sudden releases
of energy stored in sunspot
magnetic fields.Coronal mass ejection
Billion-ton clouds of charged
particles leave the Sun moving
at millions of miles per hour.Corona
This is the Sun’s outer
atmosphere and source
of the solar wind.Photosphere
This is the Sun’s
visible surface.Tachocline
The Sun spins like a solid body below
the tachocline, and like a fluid above.
Intense shear here helps create the
Sun’s magnetic field.Global magnetic field lines
The Sun’s global magnetic field is about 10 times
more powerful than Earth’s. Field lines exit the Sun
at the positive pole and enter at the negative pole.Core
This is the Sun’s energy
source, where hydrogen
fuses into helium.Sunspots
Dark spots mark where amplified
magnetic fields anchored far within
the Sun break through the surface.
Carried by the deep meridional flow,
sunspot fields emerge closer to the
equator as the solar cycle progresses.Magnetic field lines
Magnetic field lines are pulled
into an east-west rotation and
become twisted as the lines
rotate faster at the equator
and slower at the poles.Prominence
Magnetic fields suspend
an arch of gas far above
the Sun’s surface.Solar wind
This thin, ionized gas speeds
away from the Sun.Chromosphere
This is the middle layer of
the Sun’s atmosphere.Radiative zone
Deep inside the Sun, energy
generated through nuclear
fusion travels outward as
radiation, or photons.Convective zone
In the upper layers of the Sun,
energy is moved via convection:
Hot material rises and radiates heat
away, then sinks as it cools.Meridional flow
A current of plasma that
acts as a conveyor belt
in the convection zone.of your specific telescope, or
you may prefer to buy a sheet
of polymer filter material and
make your own. To make a
homemade filter cell, look for
Baader AstroSolar Safety Film
5.0, then visit Baader’s website
for detailed instructions on
how to construct the cell. Be
sure to purchase a filter speci-
fied as neutral density (ND)
5.0, not ND 3.8. The latter
is designed for photography
and is not safe for visual
observations.
Before using the filter,
make sure to check that it’s
still performing properly.
While some filters are made
to resist scratches, it’s better
to be safe then sorry. To check
whether your filter is safe,
simply turn on your phone’s
f lashlight and shine it directly
behind the filter. If you only
see a dim shine, you should
be safe. But if you see particu-
larly bright spots or streaks,
your filter is damaged and
should not be used.
Depending on filter coat-
ing, the Sun will appear a dif-
ferent color. Most glass filters
create a yellow-orange tint,
while many polymer filters
provide a white image with
a hint of blue.
White-light solar filters let
you confirm that the Sun is
alive and well, as groups ofsunspots trek across its photo-
sphere. These dark blemishes
mark regions where distur-
bances in the Sun’s powerful
magnetic field hamper the
convective f low of energy
from deep within. As a result,
that area of the Sun’s surface
cools slightly compared to its
surroundings. The tempera-
ture of the photosphere is
9,900 degrees Fahrenheit
(5,500 degrees Celsius), while
sunspots are cooler, ranging
between about 4,900 F and
7,600 F (2,700 C and 4,200 C).
So, sunspots have roughly the
same temperatures as the sur-
faces of the giant, puffy stars
Betelgeuse and Antares. Butbecause sunspots are cooler
and dimmer than their sur-
roundings, they appear dark
through our filters. If you
could surgically remove a
sunspot and place it alone
in the sky, it would appear
crimson in color and shine
brighter than the Full Moon.
Sunspots can range in size
from hundreds to thousands
of miles in diameter. Some
are large enough to be seen
through binoculars — and
even with the unaided eye,
using proper filtered glasses
— but most require a tele-
scope. At magnifications of
50x or more, sunspots reveal
two sections. The darker,44 ASTRONOMY • APRIL 2021
This illustration highlights some of the Sun’s most striking features, many of which you can easily view using the right equipment. ASTRONOMY: ROEN KELLY
The anatomy
of the Sun