The science of eclipses, ideas about black holes

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Photo courtesy Jerry Granok Viewers of the Oct. 23 solar eclipse were treated to a display of the largest sunspot group in 25 years, which was visible to the unaided eye. The largest dark spot was more than twice the diameter of the earth and the entire group was larger than the planet Jupiter. The San Juan Stargazers, who hosted a viewing parting for the eclipse, will meet on Nov. 20 and discuss ideas about black holes.
Photo courtesy Jerry Granok
Viewers of the Oct. 23 solar eclipse were treated to a display of the largest sunspot group in 25 years, which was visible to the unaided eye. The largest dark spot was more than twice the diameter of the earth and the entire group was larger than the planet Jupiter. The San Juan Stargazers, who hosted a viewing parting for the eclipse, will meet on Nov. 20 and discuss ideas about black holes.

By Jerry Granok
Special to The PREVIEW

Pagosa Springs enjoyed (mostly) clear skies the afternoon of Oct. 23, giving those looking skyward a clear view of the partial solar eclipse.

The local San Juan Stargazers astronomy club held a public eclipse viewing party at Yamaguchi Park with two telescopes set up for safely viewing the eclipse, as well as providing eclipse glasses for viewing the eclipse without any optical aids.

Too, viewers were treated to a display of the largest sunspot group in 25 years, which was visible to the unaided eye. The largest dark spot was more than twice the diameter of the earth and the entire group was larger than the planet Jupiter.

A good number of adults, junior astronomers and peewee astronomers turned out to enjoy the spectacle. Although the youngest viewers hadn’t yet mastered looking through an eyepiece, they were nonetheless able to view the sun with the eclipse glasses.

A solar eclipse occurs when the moon comes directly between sun and the earth and the cone of the moon’s shadow reaches the surface of the earth.

Every solar eclipse happens at the time of a new moon, but not every new moon produces an eclipse. This is because the plane of the moon’s orbit around the earth is tipped relative to the plane of the earth’s orbit around the sun by about 5.1 degrees and only when the moon is at the intersection point of the two planes can the eclipse occur.

Further complicating the situation is the fact that the earth’s distance from the sun varies between 91,400,000 and 94,510,000 miles, while the moon’s distance from the earth varies between 225,622 and 252,088 miles.

If the moon is too far from the earth, it cannot completely cover the sun, resulting in an annular or ring eclipse, which is what occurred on May 20, 2012.

If, however, the moon is not too far from the earth, it can cover the face of the sun, exposing only the solar corona in a total solar eclipse, which will occur on Aug. 21, 2017.

These conditions only apply to locations on the earth’s surface that lay directly in the path of the moon’s shadow as it courses across the earth. Everywhere else will experience a partial solar eclipse with a varying degree of coverage of the sun’s face depending on the distance a location is from the centerline of the shadow’s path.

In 2012, Pagosa saw 92 percent of the sun’s diameter covered and in 2014 we saw only 52 percent of the sun’s diameter covered. In the 2017 eclipse, we will see 85 percent of the sun’s diameter covered.

Fortunately, the path of totality for the 2017 eclipse will be less than a day’s drive away from Pagosa, so experiencing totality shouldn’t be too difficult for someone wishing to see what could be a once-in-a-lifetime event.

Eclipse chasers have been known to go to extremes to see total eclipses. If you want to wait for it, Pagosa will experience an annular eclipse of six-minute duration on the morning of Nov. 15, 2077.

For detailed information on and forecasts of eclipses, I suggest three websites: the NASA website, eclipse.gsfc.nasa.gov/eclipse.html, mreclipse.com by Fred Espenak who does the eclipse calculations for NASA, and shadowandsubstance.com, which has some excellent animations on eclipses.

Next meeting

The next meeting of the San Juan Stargazers will be on Thursday, Nov. 20, at 7 p.m. at the Chamber of Commerce on Hot Springs Boulevard. We will be reading and discussing several articles about the latest ideas about black holes.

Please note that this meeting and next month’s meeting will take place on the third Thursday of the month instead of the usual fourth Thursday of the month because conflicts with the Thanksgiving and Christmas holidays.

If you are a visiting amateur astronomer or are just interested in astronomy, you are invited to join our club meeting and share your interests and activities with us. We value new ideas.

The San Juan Stargazers are part of the Astronomical League, which includes clubs from all over the U.S. We have a great website, www.SanJuanStargazers.com, as well as an email address, sjstargazers@gmail.com, and a club phone number, 335-8286.