BEAUTY: 
BRAGGING RIGHTS: An amazing sight
HOW EASY IS IT TO SEE? Requires special equipment
TYPE: Sun
DISCOVERED: Known since antiquity
The sun is full of mysteries—an unnerving fact given how much we rely on it to sustain all life on Earth. Around 150 years ago, German scientist Julius Mayer calculated that if the sun were a huge ball of burning coal, it would only take a few thousand years for it to burn out. William Thomson—later Lord Kelvin—considered whether energy released by a slowly contracting sun could explain why it shines. He concluded that in such a case it would only last a few million years.
It wasn’t until the twentieth century and the notion of nuclear fusion before scientists could begin to explain the sun’s prodigious and seemingly inexhaustible output. Yet even then mysteries remained: in the mid-1960s, astronomers measured the number of neutrinos emitted by the sun and discovered far fewer than expected. Since nuclear fusion inevitably produces neutrinos, astronomers wondered whether fusion in the sun’s core had decreased or even stopped—a frightful idea. Many years (and one Nobel Prize) later, scientists concluded that the sun was healthy, and that neutrinos were simply morphing into undetectable forms.
Even today, we are far from understanding the sun. In the late nineteenth century, astronomers Annie and Walter Maunder showed that the late 1600s, an unusually cold period in history, coincided with a marked absence of sunspots. Could decreased solar activity have caused the so-called Little Ice Age? And could it happen again?
WHAT YOU MIGHT SEE THROUGH AMATEUR EQUIPMENT
Sunspots increase and decrease over an 11-year cycle, and they are caused by the turbulent electromagnetic forces churning at the heart of the sun. At peak times in this cycle, solar activity increases, causing more solar outbursts and more sunspots.
Yet as the Maunders showed, the sun isn’t that simple. Not all cycles are equally active, and sometimes the sun is unusually quiet for many cycles at a time. As of this writing, the current solar cycle, known as Cycle 24, is on track to have the fewest sunspots since modern records began. Will sunspots continue to decrease? Are we heading into another Little Ice Age? We don’t know. The sun is full of mysteries.
The sun is almost an ideal observing target. It’s visible in the sky every day, barring clouds, and it’s easy to find. Unfortunately, it is also the only astronomical object that presents real danger. Looking at the sun directly can harm your eyes and viewing it through unprotected binoculars or a telescope will blind you for life. Do not take any chances when observing the sun, particularly when doing so around children.
To view sunspots and prominences, I recommend purchasing a reputable solar filter, which you can place over the front of your telescope or binoculars. These filters look like mirrored or dark glasses and must be securely and reliably attached before using them. In particular, I’d recommend a hydrogen-alpha filter. These filters are more expensive, but they reveal much more detail than others.
Sunspots. Sunspots are areas in which an intense magnetic field has decreased the convection of superheated gases, resulting in cooler—and hence darker—spots. Sunspots have a dark central area, known as the umbra, surrounded by a lighter-colored penumbra.
Prominences. Look at the edge of the sun and you might spot some flame-like structures; these are often looped. These are prominences, and they are vast plumes of superheated gas flowing along a tangled magnetic field.
Chromosphere. A hydrogen-alpha filter allows you to see complex details across the entirety of the solar surface. This is the chromosphere, and it looks like a boiling cauldron of incandescent gas. Like other solar features, the chromosphere is governed by magnetic forces. All the detail you see is caused by the complex rippling magnetic forces of the sun.
