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  Night Sky
 

Enjoy our starry night skies.
Be a considerate neighbor: reduce nighttime glare.
Shield your outside lights downward.
Let the stars light up the night.

April 2013 Night Sky

—Charlie Christmann

Every eleven years or so, solar activity peaks: sunspots dot the surface, flares flutter over the surface, and coronal mass ejections pound the solar system. Scientists are very interested in how the sun behaves, especially during its most active state, scheduled for this spring.

The cycle uses the number of sunspots observed on the surface of the sun as an indicator of how active the sun is. At its minimum, it is not unusual to go days without seeing a sunspot. During the cycle’s maximum, however, it is common to find a dozen or more dotting the sun. Sunspots are dark areas on the surface where temperatures fall several thousand degrees below the surrounding area. They are extremely concentrated magnetic fields, several thousands of times stronger than the Earth’s magnetic field that prevent hot material from deeper inside the sun from boiling up to the surface—the darker the area, the stronger the field and the cooler the temperature. Because magnets must have a north and a south pole, sunspots normally form in pairs, one north and one south. Most sunspots are huge, easily swallowing several Earths.

With sunspots come solar flares. A flare is a sudden increase in the brightness on a small area of the sun. The huge magnetic fields, normally associated with the sunspots, become tangled up and snap like a tightly wound rubber band. Enormous amounts of energy are released in the process creating electromagnetic radiation from radio waves to visible light to gamma rays. The higher energy X-rays and gamma rays can be dangerous to spacecraft and astronauts in space. Unfortunately, the light from a flare and its associated radiation arrive at the same time. There is no way for us to warn the astronauts or protect our spacecrafts.

Larger flares are powerful enough to blow some of the sun into space. Billions of tons of solar material leave the surface of the sun traveling hundreds of miles per second in a Coronal Mass Ejection (CME). CMEs are filled with charged particles, protons and electrons, which can damage electronics in spacecraft, and can be more dangerous to astronauts than the X-rays. Fortunately, Earth’s magnetic field and our atmosphere protects life on the surface; but, depending upon the strength of the CME and the direction of the CME’s magnetic field, some material gets through our magnetic shield, producing auroras, near the North and South Poles. Very large flares and CMEs can damage electrical systems on the ground. On March 17th, a powerful CME, ejected from the sun two days earlier, rocked our magnetic field, allowing particles to leak down to the atmosphere, producing red and green auroras as far south as Colorado.

Scientists expect the current solar cycle to peak in the Spring of 2013, but something unexpected is happening: solar activity is already waning. Just don’t count the sun out quite yet. The previous cycle exhibited a “double peak” several months apart.  No matter what happens, this peak looks to be much weaker than the 2000-2002 peak.

A challenge

It is time to get outside in the evenings, enjoy our dark skies, and do some observing. So, I am challenging you to go out on Friday and Saturday evenings and find some satellites. I suggest using Heavens-Above.com to see what is coming over each night. Use the “Daily Prediction” link. Don’t forget to set your location: 35.308N 106.724W for Placitas.

Easiest to see will be the Space Station; hardest will be the dim rocket bodies. Keep a log of your observations and send it to sky@civicplaza.net by April 15th. I will recognize those with the most observed objects and those with the dimmest objects.

 
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