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  Night Sky

July 2009

—Charlie Christmann

Sunspots

Lazy Sun

Sunspots are planet-sized “islands” on the surface of the sun. They are dark, cool, powerfully magnetized regions on the sun that come and go. A typical sunspot lasts only a few days or weeks before it breaks up. As soon as one disappears, however, another usually emerges to take its place. There is a cycle of sunspots that occurs about every eleven years or so—some cycles have been as short as eight years, others as long as fourteen years. The cycle goes from a quiet, calm sun with few spots to a more active sun with flares and many spots, then back to quiet over this cycle.

The cycle that started in 1996, cycle 23, produced some very large flares just after its peak in 2000. In fact, the largest flare recorded since we have been measuring flares occurred on April 11, 2003. Other very large flares happened in 2001, 2003, and 2005. Such large flares cause havoc for satellites and astronauts in orbit.

So, with the waning of cycle 23, what would cycle 24 hold, and when would it start? All the chaos started in 2003, when Dr. David H. Hathaway with the NASA Marshall Space Flight Center in Huntsville, AL thought he and his team had deciphered the secrets to predicting the start of the next solar cycle: 2006. They determined that the peak should be about 2010.

On schedule, in March 2006, NASA announced the end of cycle 23. Sunspots had all but vanished. Solar flares were nonexistent. The sun was extremely quiet. In the same announcement, NASA said, “This week researchers announced that a storm is coming—the most intense solar maximum in fifty years. The prediction comes from a team led by Mausumi Dikpati of the National Center for Atmospheric Research (NCAR). The next sunspot cycle will be thirty to fifty percent stronger than the previous one.” These predictions caused much concern for NASA and satellite operators. NASA has several Moon missions planned over the next few years, and without the protection of the Earth’s magnetic field, solar storms can be deadly to electronics and humans alike. The 2003 and 2005 flare events permanently damaged several communications satellites and disrupted radio communications worldwide.

In April 2007, another announcement from the “experts” said, “Expected to start last fall, the delayed onset of Solar Cycle 24 stymied the panel and left them evenly split on whether a weak or strong period of solar storms lies ahead…”

Then in January 2008, there was much hand-wringing over the continued lack of sunspots. There had been months on end with no spots on the sun. Everyone was still very confused. Was this to be the start of another great solar minimum like the Maunder Minimum of 1645-1715 that lasted an incredible seventy years? During that minimum, there was a mini ice age with some extraordinarily bitter winters in Earth’s northern hemisphere.

Well, it is now mid-2009 and the sun is still sleeping. Yes, we have seen some small and short-lived sunspots here and there, yet the sun has been quiet for weeks and months on end. The latest NASA predictions put the switch from cycle 23 to cycle 24 in November or December 2008 and maximum in March or April 2013. And as for the intensity, they now predict a peak about two-thirds of the last cycle, giving satellite operators and astronauts alike a bit more comfort while traveling in space.

Recently, the American Astronomical Society researchers announced that a jet stream deep inside the sun is migrating slower than usual through the star’s interior, giving rise to the current lack of sunspots. The researchers found that the jet stream associated with the next solar cycle has moved much more slowly than expected. It has taken three years to cover a ten-degree range in latitude; normally, the jet stream covers that distance in only two years for the previous solar cycle. The stream will need to reach a critical latitude of twenty-two degrees before the new cycle sunspots start to appear. The jet stream is now finally reaching that critical latitude. We will be watching for the return of solar activity in the months and years ahead.

The Planets and the Moon

Mercury will be in the glare of the Sun this month.

Venus is getting higher in the morning sky. It will be easier to spot as the month goes on, as it is now a brilliant magnitude 4.4 and its disk is about sixty-five percent illuminated.

Earth reaches apogee (farthest point in its orbit from the Sun) on the 3rd at 8:00 p.m. MDT. I predict many shooting stars over our cities and towns on July 4th.

Mars is across the solar system from us and is a small red object rising at about 2:00 a.m. It is currently in a retrograde motion, moving eastward against the background stars.

Jupiter is rising around 10:00 p.m. this month and is high in the sky by 2:00 a.m., with the Milky Way all around it. Jupiter joins the Moon in a conjunction on the 10th.

Saturn is low in the west just after sunset.

Neptune can be found most easily on the 8th using Jupiter. With binoculars, look one lunar diameter above the Jovian planet.

The Moon reaches its apogee and will be new on the 7th. It will produce a penumbral eclipse where the tip of the moon may appear redder than normal. Take a look between 2:30 a.m. and 4:45 a.m. The Moon will be full and will reach its perigee (closest to Earth) on the 21st. The next evening, there will be a total eclipse visible in India and China.
     

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