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OBSERVATORY
Telescope
A telescope is basically a “light bucket”. It works by capturing as
much light as possible from a given region of the sky and concentrating it
into a focused beam, which can be viewed through an eye-piece for
analysis. By doing this, observers like us get a chance to view celestial
objects. During the daytime, the sun is usually the only heavenly body that
we can see. Its light is so bright that it overwhelms all other stars and
planets from our view. However, sometimes we can see the Moon and
Venus. The other planets that we can observe through a telescope, like
Jupiter, Saturn, and Mars, are best seen in the night sky. There are many
other celestial objects like stars, black holes, and comets that are out there
to be studied.
An optical telescope is one designed to collect wavelengths of light
visible to the human eye. Optical telescopes fall into two basic categories:
reflectors and refractors.
Reflection
Refraction
Focal Point
Focal Point
Eyepiece
Eyepiece
Lens
Reflecting telescopes use a curved mirror to gather and concentrate a
beam of light. A refracting telescope uses a lens to focus the incoming light
by funneling it down to a small point. Refraction is the bending of a beam
of light as it passes from one transparent medium, like air, into another,
such as glass. Both the refractor and the reflector aid the naked eye in two
ways: they collect more light than the eye could on its own, and they
magnify the image. Certain lenses bend light more precisely then others.
Similarly, some reflectors have smoother curves and shinier surfaces. In
both cases the better the equipment, the sharper and brighter the image
will be. Take a look into our telescope. See anything cool?
Refractor
Reflector
The Zeiss Refracting Telescope
This particular telescope was custom built for the institute in 1931.
We ordered it from the famed telescope builder Carl Zeiss, a German
native who knew and loved the science of astronomy.
Our telescope is very powerful. With a German refractor lens 10
inches in diameter and a 40 mm eyepiece, we have the ability to magnify a
heavenly body 91.4 times. A magnifying power that large prevents us from
seeing the entire sun in one field of view. To get an idea of what this
means, take a look at the sun right now—does it take up the whole field of
view of your eyes? Not at all! The sky is most of what you see right now.
If you look at how small the sun appears to be in the sky, and compare it to
the size it appears in our telescope, you can get an idea of the magnifying
power of this telescope.
When we look at the sun through this telescope, we place a certain
filter over the lens to cut out the wavelengths of light that would harm our
eyes. This filter is called a Hydrogen-Alpha filter and it makes the sun
appear red in color. Thanks to the reddish coloring; it is easier to see solar
prominences, which are streams of glowing gas that explode from the sun.
Look at the edge of the sun. Can you see the fuzzy result of those solar
gases? The other filter we use is a Mylar filter, which reduces the sun’s
apparent brightness. This makes it easier to view sunspots, the darkened
areas where the surface of the sun is cooler.
Each body in space has its own coordinates that tell us where it is in
the sky. You can think of the coordinates as a star’s address; it always
stays the same whether the earth is in a good position to see it or not.
These numbers work much the way latitude and longitude do on the Earth,
except these numbers are for the sky! The numbered dials on the
telescope allow us to point the lens in the direction of certain stars or
galaxies using two different numbers.
Another component of the Zeiss is the huge white disc on the side.
Actually, there are two—one on both side—and hanging from them are the
counter weights. Thanks to these, the telescope is balanced so that it is
easily movable.
A hydrogen alpha (Ha) filter is used for special kinds of solar observing. The name
comes from the alpha emission line of hydrogen, which is in the red portion of the
visible spectrum. Many solar features are most prominent in the red light of this line,
and get drowned out by the intense yellow-white light of the photosphere. With an
Ha filter, many solar features, notably prominences, that are invisible normally
become easy to see (without an Ha filter, about the only way to see prominences is
to be fortunate enough to see a total solar eclipse).
Staffing the New & Improved Observatory
1. Check the eyepiece view to make sure the sun is visible.
2. Adjust the focus if needed. First, loosen the twist knob on top of the brass
section of the eyepiece. Then using the two brass knobs under the
eyepiece adjust the focus. Finally, re-tighten (lightly) the twist knob on top
to lock the focus in place.
3. If the edge of the sun is not in view or sunspots are not visible on a
particular section of the sun, move the telescope by pressing any one of
the four big buttons on the paddle. Use only one button at a time. The
button positions correspond to the direction of movement.
4. If the sun is not visible at all in the eyepiece…stand back from the
telescope and move the scope to line up the shadows on the sun-sighting
target near the finder-scope.
5. When you reach the sun, look through the eyepiece and center the sun
again using the directional buttons on the paddle.
6. When you release the directional motion buttons, the drive motors are
automatically set on the speed needed to follow the sun continually
throughout the day.
7. Position the staircase so that visitors can comfortably and safely reach the
eyepiece.
8. Adjust the view through the telescope as needed throughout your time in
the observatory using the paddle.
The SUN
The Sun is a ball of hot gasses that get denser as you move deeper and
deeper into the Sun. The Sun is mostly made up of Hydrogen and Helium
but does contain some other small amounts of different elements. The
photosphere (sphere of light) is the visible layer of the Sun: it makes the
sun appear to have a surface, because this is where most of the visible
light comes from. The temperature of the photosphere is about 10,000F.
When looking at the Sun you may notice that the edge of the sun looks
darker: this is called limb darkening. The reason this happens is because
when we look at the sun, we are looking through layers of hot gasses. At
the limb, or the edge of the sun, we don’t get to look through as much of
the gasses and end up only looking through higher, cooler, and darker
gasses.
Features of the QUIET Sun:
When looking at the surface of the sun, we can see blotchy patterns called
granulation on the photosphere. The lightly colored granules are
surrounded by darkish boundaries. Hot gasses rise upward in the center
of each granule and that gas radiates its energy out into space, therefore
cooling the gasses. When this happens, the gasses don’t give off as much
light and are darker: they eventually sink back towards the center of the
sun. Hotter regions emit more photons per square meter than do cooler
regions, which makes them appear brighter.
The chromosphere is directly above the photosphere and is the area
where the edge of the sun meets the sky. If you look at the edge of the
sun, you will see small spikes coming off the edge of the sun; they are
called spicules. The other thing that you can see on the surface of the
sun is large areas of gases that are rising and falling in the chromosphere.
Each supergranule is made up of hundreds of granules in the
photosphere below. The corona is the outermost region of the Sun’s
atmosphere, and it extends several million kilometers from the top of the
chromoshpere. As you move away from the center of the sun, the heat
source for the sun, you would think that it gets cooler, but it does not. The
temperature can rise to 2 to 4 million F. When gases are moving fast
enough, they can escape the gravitational pull of the sun. The outflowing
gas is called solar wind.
Features of the ACTIVE Sun:
The Sun’s atmosphere is periodically changed by its magnetic fields, and
the most common features of these changes are sunspots. These are
areas of the photosphere that appear dark because they are cooler than
the rest of the Sun’s lower atmosphere. Most of the time, they appear in
groups or clusters. Sunspot numbers have a cycle of eleven years-the
next is a sunspot minimum predicted for 2007. A typical sunspot is about
10,000 km across, about the size of the Earth, and can last from a few
hours to a few months. Each sunspot has tow parts: a dark center area
called the umbra and a brighter ring called the penumbra. The umbra is
about 7300F while the penumbra is about 8500F. Sunspots were used by
Galileo to discover that the Sun rotates once in about four weeks. A
typical sun spot group can last around 2 months; you can see about two
rotations. The Sun spots also help us see how the sun rotates at different
speeds depending on what latitude you are at on the sun.
In 1908, the American astronomer George Ellery Hale discovered that
sunspots were directly linked to intense magnetic fields on the Sun.
Sunspots are areas where concentrated magnetic fields project through
the hot gases of the photosphere. These jumbled regions of magnetic field
block gases from expanding and becoming buoyant and floating up
through the solar surface. Scientists have also studied and noticed that
sunspots come in pairs and that the magnetic field is always opposite each
other in the pair. This means in any pair of sunspots, there will be one N
and one S. The magnetic field lives leave the surface of the sun with a
north polarity and re-enter at a south polarity. At these two spots, you get
sunspots, areas where the magnetic field is stronger and does not allow
the hotter warmer gases move towards the surface of the sun. This buckle
in the magnetic filed also creates a prominence. As the magnetic field
stretches away from the surface of the sun so do the gases of the sun,
which follow the magnetic field line.
The Sun’s magnetic field is reversed every 11 years. A full solar cycle is
22 years long. Sometimes these solar cycles do not work perfectly.
Sometimes there are no sunspots, and the sunspot cycle has vanished for
decades at a time. In 1645 to 1715, historic data shows that there may
have been no sunspots at all. This time period coincides with a period of
cold in Europe so extreme that is was called the Little Ice Age. At the
same time, western North America was subject to severe drought. It does
remain to be proven that the number of sunspots is the cause for these
weird weather patterns.
More things that the solar magnetic fields create:
Bright areas on the surface of the sun are called plages pronounced
“plahj”. They are hotter and brighter areas usually near or just before
sunspots appear. They are thought to be made by magnetic fields under
the photosphere crowding upward just before they emerge through. This
pushing from the field compresses the gases making them hotter and
brighter.
Dark streaks in the corona are called filaments. These are huge volumes
of gas lofted upward from the photosphere by the sun’s magnetic field.
When viewed from the side rather than from above, they are shown to form
big loops or arches called prominences. These gases can get really hot
about 90,000F. They are almost always associated with sunspots and can
last for a few hours to months. Some can escape the magnetic fields that
hold them in and go out into space.
Violent, eruptive events on the Sun, called solar flares, also send out
huge amounts of particles like X-rays and ultraviolet radiation. At the
maximum of the sunspot cycle there are 1,100 flares per year! Most flares
last for less than an hour but can get really hot – about 9 million F. A flare
is sometimes associated with coronal mass ejections, which expel 2 trillion
tons of matter at 400kmm/s and can last up to a few hours. This energy
coming from the Sun in a flare, prominences, or coronal mass ejections
can reach the earth in about 8 minutes and their high-energy particles
arrive a few days later. This can give us cell phones problems, satellite
issues, cause harm to astronauts, and pretty aurorae.
Magnetic Field
A field of force that is generated by electric currents. The Sun’s
large-scale magnetic field, like that of the Earth, exhibits a north and
a south pole linked by lines of magnetic force.
Magnetic Field Lines
Imaginary lines that indicate the strength and direction of a magnetic
field. The orientation of the line and an arrow show the direction of
the field. The lines are drawn closer together where the field is
stronger. Charged particles move freely along magnetic field lines,
but are inhibited by the magnetic force from moving across field
lines.
Sunspot
A temporary disturbed area in the solar photosphere that appears
dark because it is cooler than the surrounding areas. Sunspots
consist of concentrations of strong magnetic flux. They usually
occur in pairs or groups of opposite polarity that move in unison
across the face of the Sun as it rotates.