Cumberland Times-News

Columns

June 22, 2013

Can we count on our sun to be reliable?

One constant in our lives is the radiation from our sun. Of course, how much sunlight we receive from our star depends on the weather, subject to changes each day. But above our atmosphere’s weather layer, the sun’s outpouring of radiation hardly varies.

In 2011, Astronomy columnist Bob Berman wrote “The Sun’s Heartbeat”, a fascinating account of the many aspects of our sun. “Heartbeat” was published by Little, Brown and Company with ISBN 978-0-316-09101-3.

In the Introduction and Chapter One, Berman relates that there are six spacecraft in orbit dedicated to observing our sun. For our bodies, sunlight powers the production of Vitamin D, a potent anti-cancer agent.

But at the same time, solar ultraviolet radiation can cause skin cancer. A 1 percent increase in solar ultraviolet radiation leads to a 1 percent increase in the incidence of skin cancer. So what should we do?

Berman responds that we should limit our bare skin’s exposure to about 20 minutes a day. Beware of the most intense sunlight, which occurs from 10 am. to 4 p.m. Applying sun screen on our skin stops Vitamin D production. So some bare skin exposure to sunlight is good, too much is bad.

Until a century ago, the sun’s great energy was a mystery. Physicists in the late 1800s proposed that the sun was a shrinking ball of gas with its energy stemming from the collision of gas atoms as the sun converted gravitational energy into thermal energy.

But this source would only account for the sun’s energy flow for a few hundred million years, far too short for the history of life embedded in our rock layers.

In 1920, Arthur Eddington proposed that the merging of hydrogen nuclei could account for the sun’s energy flow over billions of years. About 20 years later, Hans Bethe of Cornell showed how this conversion could take place in the sun’s core.

Our sun converts hydrogen into helium in a three stage process called the proton-proton cycle. Every second, our star converts 4 million tons of hydrogen into energy. The conversion of mass into energy is by Einstein’s famous equation, E = mass x (speed of light squared) or E = m*c squared.

In the early 1600s a number of observers with telescopes announced the discovery of dark blemishes on the sun’s blinding face. There were many interesting explanations including dark clouds in our sun’s atmosphere, and openings in hot clouds that surrounded the sun.

In the late 1800’s, an analysis of sunlight from these dark regions revealed that they were regions of intense magnetism on the sun’s glowing surface (photosphere). The intense magnetism reduces the flow of upward energy, cooling these regions temperature by several thousand degrees (versus the average surface temperature of the photosphere of 6000 C or nearly 11,000 F).

Solar observers had records of these planet sized magnetic storms since their telescopic discovery. These sunspots seem to have a curious effect on Earth’s surface temperature.

Whenever there is a prolonged absence of these storms (several decades or more), the Earth’s surface temperature drops. This happened in the late 1600’s resulting in “The Little Ice Age” in both Europe and North America. Recently, there was a stretch of 801 days when no solar storms or sunspots were seen.

Now the sunspots have come back again. But the next cycle is predicted to be quite weak. The sunspot cycle (number of storms rising and falling) lasts about 11 years. The reduced solar radiation in the past few years might actually be masking the warming due the high level of carbon dioxide in our atmosphere (has increased from 280 to 400 ppm since the industrial revolution in the early 1800’s).

SKY SIGHTS AHEAD: The moon is full tonight (actual time of full phase is 7:33 a.m. this morning). This full moon is in the southernmost part of the zodiac, so the moon sky track is very low.

The moon this morning was very close to its closest distance to the Earth, so there will be very high high tides and very low low tides today.

Tomorrow evening the brilliant planet Venus will nearly line up with Vesta, the brightest asteroid seen from Earth,

But presently Vesta is not close to the Earth so you will need binoculars to see Vesta, lost in Venus’ glare as Venus is more than 60,000 brighter than Vesta. Vesta will appear about one moon width to the North (or right) of Venus.

Bob Doyle invites any readers comments and questions. E-mail him at rdoyle@frostburg.edu . He is available as a speaker on his column topics.

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