Whats Up in the Sky May 2005

History shows a woman’s place is in outer space

Remember the old Beach Boys’ lyric, “And she purrs like a kitten till the lake pipes roar”? They were referring, of course, to their little deuce coupe. For centuries men have been referring to ships and machines with feminine pronouns. Although not as common anymore, there was a time when the most famous computers were, literally, women.

Maria Mitchell was America’s first well-known woman astronomer. On Oct. 1, 1847, while her parents entertained dinner guests downstairs, she discovered a comet. At one point in her career she worked as a computer (one who performed lengthy mathematical calculations) for 19 years out of her home, calculating positions of Venus.

In 1875, three women were hired to work at the Harvard College Observatory performing the involved mathematical computations necessary to calculate orbits, measure positions and brightness of stars, and classify stellar spectra. Due to an increasing number of photographic plates exposed through the telescopes, the observatory needed helpers to search the plates and perform long, detailed calculations to determine the information about the stars recorded on them. In the notions of the day, women were considered ideally suited for such routine, meticulous, and tedious work (men being better suited to creative projects). And, since a woman could be paid considerably less than a man, three or four times as many assistants could be hired for the same amount of money. Between 1877 and 1919, a total of 45 women were employed by the Harvard College Observatory to work as “computers.”

Some very important discoveries were made thanks to the work done by these women. Annie J. Cannon established the system of classifying the spectra of stars that, with minor modifications, is still in use today.

Henrietta Leavitt may have made the most significant discovery of all the women computers. Leavitt discovered a property of certain stars that vary in brightness, known as the Period-Luminosity Relation, that allows astronomers to determine the star’s actual brightness, or luminosity, by measuring how long one bright-dim-bright cycle takes. (Such stars are known as Cepheid variables). By comparing the real brightness of a star with how bright it appears, astronomers can determine the distance to the star. (You do the same thing when you drive at night and see headlights approaching). Her work led to fundamental improvements in our understanding of the size of our own galaxy and, ultimately, to the discovery of the expanding universe.

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Here are this month’s viewing highlights:

• May 1 and May 30: Last quarter moon
• May 8: New Moon
• May 9: using binoculars, look WNW to see Venus below the crescent moon; also look for the star Aldebaran and the Pleiades cluster to Venus’ left and right, respectively
• May 16: First quarter moon
• May 24: Full Moon occults Antares – 4:00 a.m.
• May 31: two hours before sunrise look for Mars right above crescent moon in ESE
• Planets this month: Jupiter, the brightest object in the sky after the moon, dominates the southern sky throughout the month; Saturn sinks in the west as the month progresses; Mars is in the southeast at dawn; Venus follows the sun over the western horizon and becomes easily visible by month’s end.

Peter Burkey is president of the Shoreline Amateur Astronomical Association and has been an amateur astronomer and astrophotographer for 25 years. He also taught astronomy at Fennville High School from 1981 to 2003.

Peter Burkey – SAAA President

Whats Up in the Sky April 2005

Good science measures age of universe

Last month I asked readers to send in questions that I would attempt to answer today. My thanks to Albert Holthof whose question dealt with the age of the universe and how it is determined. As soon as I received his question, I knew I was in trouble. After three days of research and writing I realized I could never fit an adequate answer into this column. However, I do owe Albert (and you) some sort of explanation, so here goes.

Albert Einstein’s general theory of relativity provides the framework for our understanding of the universe’s evolution. All of our observations clearly indicate that the universe began with a “big bang” which caused space to expand, carrying all of its matter and energy with it. When we look at distant galaxies, we see that they are all moving away from us like raisins in a rising loaf of raisin bread dough. If we run the clock backwards, we find them coming together until all matter (and space) was crowded to a single point about 13.7 billion years ago.

The best alternative method for estimating the age of the universe is from calculations of the evolution of the oldest known stars, those found in globular clusters. Those calculations agree very closely to the 13 billion year age.

Another important piece of evidence was the discovery, in 1964, of cosmic microwave background radiation, energy left over from the “glow” of the big bang. Careful analysis of this radiation confirms several important features of the big bang theory and allows us to calculate the universe’s age based on the theory’s predictions.

I find it interesting that we accept without question certain scientific theories while others are greeted with doubt and skepticism. No one argues any more about whether the earth orbits the sun or vice versa. I don’t think many of us would question the validity of the theories governing or cell phones, weather satellites, or iPods. Yet these items work because of the same theory (general relativity) that governs the universe. It should be noted that Einstein’s theories have never failed a test and are now accepted as fact, even though everyone thought he was nuts when he first published them.

Scientists must be willing to accept experimental results which seem to contradict current beliefs or even common sense. Recently it has been discovered that not only is the universe expanding, but the rate of expansion is increasing due to some mysterious unknown force called “dark energy.” Astronomers have had to rethink their entire understanding of the cosmos based on these new discoveries. That’s the essence of science.

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Congratulations to Lowell Winne of Fennville who correctly answered last month’s trivia question, “What human-made object is farthest from the earth”? Answer: Voyager 1, launched September 5, 1977, holds that distinction at a distance of almost 95 AU (1 astronomical unit, or AU, equals the average distance between the earth and the sun). The spacecraft is still functioning although it takes more than 13 hours for transmitted data to reach us.

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Here are this month’s viewing highlights:

• April 3: Jupiter is at opposition and is visible all night
• April 8: New Moon – solar eclipse visible across Pacific ocean and South America
• April 11: thin crescent moon close to Pleiades low in west after sunset (great in binoculars)
• April 15: first quarter moon near Saturn, Castor, Pollux
• April 24: full Moon
• April 28: use binoculars to see Venus near west horizon 15 minutes after sunset

Peter Burkey is president of the Shoreline Amateur Astronomical Association and has been an amateur astronomer and astrophotographer for 25 years. He also taught astronomy at Fennville High School from 1981 to 2003.

Peter Burkey – SAAA President