June 12, 2010
Stargazer #533
Some Stargazing Ideas While Camping Out
Recently I received the following email from Joe Garcia who reads Stargazer in the Kingsville Record: "I am a Cub Scout leader and am taking my boys camping June 11-13. I want to do an astronomy section one of these nights, something that the boys will enjoy and learn from. I would greatly appreciate any suggestions you might have. I am new to this and want my boys to learn and have fun. Thank you for your time."
After re-reading my response to Joe, it occurred to me that my ideas might be of interest to others, especially those who, like Joe, work with kids. So here are some of my offerings.
As the Sun is setting in the west, have the kids watch the western sky and see who can be the first to spot the "evening star." After it gets darker and other stars begin to appear, it will be apparent that this "star" is much brighter than all the other stars because it's not really a star -- it's the planet Venus, the nearest planet to Earth.
Then as it gets darker, have the kids to look all around the night sky and try to find the Moon. They won't be able to, so ask them why there's no Moon out. Answer: June 12 happens to be new Moon when the Moon is in the same direction as the Sun, thus it sets at sunset and won't rise until sunrise the next morning. Each night thereafter, the Moon rises and sets nearly an hour earlier than the previous night. This can lead to a discussion about the phases of the Moon.
Depending upon how near to a city you are camping, you will likely encounter light pollution. Point this out to the kids, especially if you can see more light pollution in one direction than another. Show how the more light pollution there is, the fewer stars one can see. If you happen to be far from city lights, show them the Milky Way which they can't see from town.
For a final activity, help the kids learn to use the stars to find north and the other directions. Have them search the sky for the Big Dipper. Then tell how the dipper's "pointer stars" point to Polaris, the North Star. As they find and identify Polaris, have them notice that it is NOT the brightest star in the sky as many think.
To dig a bit deeper, these and other topics are elaborated in previous "Stargazer" columns which are archived at COLUMNS in this Web site, and in my book, Learning the Night Sky, about which you can also learn more at BOOK elsewhere in this Web site.
- Next Two Weeks. Avg. sunrise: 6:24 a.m.; avg. sunset: 8:36 p.m. (exact for Waco, TX)
* Early this evening Venus and Gemini's brightest stars Pollux and Castor are aligned and equally spaced low in the west at dusk, and the Moon is new.
* Monday evening a crescent Moon is below Venus.
* Wednesday evening the crescent Moon is below Mars, and then to Mars' left the next night.
* The 1st quarter Moon is below Saturn Friday evening.
* The early evenings of June 19 and 20, Venus is within two moonwidths of the Beehive cluster low in the west; use binoculars to see the cluster.
* June 21 is the summer solstice, the start of summer in the Northern Hemisphere.
- Naked-eye Planets. Evening: Venus is prominent in the west northwest, Mars is mid way up in the west, and Saturn is high in the southwest. Morning: Jupiter, rising around 2 a.m., is brilliant in the southeast by dawn.
- Star Party. The Stargazer is hosting a program and star party tonight (Saturday) at Waco's Reynolds Creek Park beginning at 8:30 p.m. (weather permitting). For directions to Reynolds Creek Park,, see MAPS & DIRECTIONS elsewhere in this Web site.
May 29, 2010
Stargazer #532
The Big Dipper
Of the very brightest stars, called 1st-magnitude stars, none are in the northern-most night sky. Yet that part of the sky holds seven moderately bright stars that form a pattern more familiar than any of the brightest stars.
The Big Dipper, probably the best-known pattern in the entire Northern Hemisphere, is part of the constellation named Ursa Major, the Big Bear.
The Little Dipper, part of Ursa Minor, the Little Bear, is not so easy to identify as four of its seven stars are faint. It does, however, contain the North Star, also known as Polaris. Since it is straight up from Earth's North Pole, Polaris never moves in our sky. It is always due north and the same distance (in degrees) above the horizon as the latitude from which it is being viewed. The two stars forming the outer end of the Big Dipper's bowl are "pointer stars" pointing toward Polaris.
Polaris is like the center of a 24-hour clock with all the other stars moving around it like the clock's hands, although in a counterclockwise direction. And just as stars circle Polaris, so do star patterns, including the Big Dipper. Depending upon the season and time of night, the Big Dipper might be above, below or east or west of Polaris.
There's a legend that helps know where to look for the Big Dipper in the early evening. In the fall the dipper is due north below Polaris, down near Earth filling its bowl with water.
In the winter it is to the east (right) of Polaris with its bowl tilted on its side and its handle pointing downward. The water doesn't spill out because, being winter, it's frozen.
In the spring the Big Dipper is again due north but above Polaris in an upside-down position. The water, now thawed, is pouring out of the dipper's bowl bringing us spring rains.
By summer, the dipper has swung around to the west (left) of Polaris with its bowl again tilted on its side and its handle pointing upward. It no longer has any water to spill on Earth, accounting for our dry, hot summers.
And the next fall it again swings down near Earth to again fill its bowl with water and begin the cycle anew. Right now in the early evening, as spring is about to turn to summer, the Big Dipper is to the upper left of Polaris.
- Next Two Weeks. Avg. sunrise: 6:24 a.m.; avg. sunset: 8:31 p.m. (exact for Waco, TX)
* The Moon is at 3rd quarter Friday.
* The morning of June 6, the crescent Moon is to the upper right of Jupiter in the east, and that evening reddish Mars is two moonwidths to the upper left of the star Regulus in the west.
* The morning of June 8 bright Jupiter is less than a moonwidth from greenish Uranus; seeing Uranus requires binoculars.
* The morning of June 10 the crescent Moon is above Mercury low in the east northeast at dawn, and the next morning to Mercury's left.
* The early evenings of June 10-12, brilliant Venus aligns with Gemini's brightest stars, Pollux and Castor, low in the west at dusk.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.) Evening: "Evening star" Venus is prominent in the west northwest, Mars is mid way up in the west, and Saturn is high in the southwest. Morning: Jupiter rises two hours before the break of dawn with Mercury very low in the east at dawn.
- Star Party. The Central Texas Astronomical Society's free monthly star party is Saturday, May 5, at the Lake Waco Wetlands beginning at 8:30 p.m. For directions see my Web site.
May 15, 2010
Stargazer #531
Halley's Comet 100 Years Ago
About every 76 years, Halley's Comet becomes visible in our night sky for several weeks, and I, like surely many of you, vividly recall its most recent return in 1986. Having heard of the famous comet from my 81-year old stargazing mentor, Margaret Willits, in 1954, I was thrilled to finally see it after a three-decade wait.
It was Ms. Willits who ignited my childhood interest in astronomy, but it was seeing Halley's Comet that rekindled the flame that has been burning brightly ever since. While Ms. Willis told me of her excitement at seeing the comet during its 1910 visit, she didn't tell me about the stir it caused at the time.
Comet Halley is one of several comets whose orbits intersect with Earth's orbit. Of course, should Earth and a comet pass through the same place at the same time, there would be a major catastrophe, such as the one believed to have led to the extinction of the dinosaurs -- but fortunately that's quite rare.
However, the intersection of the orbits of Earth and a dozen or so comets does have some interesting consequences, the most common of which are annual meteor showers. Comets leave tiny pieces of dust, ice and rocks scattered along their orbital path. So when Earth, traveling at the incredible speed of 67,000 miles per hour, passes though the debris-laden path of a comet, friction between the debris and Earth's atmosphere causes bits of debris to burn and glow, producing meteors, those brilliant streaks that flash across the night sky, also called shooting stars.
Twice each year we pass through Halley's path, producing the Eta Aquarid meteor shower in May and the Orionid shower in October.
But when Halley came by in May 1910, the encounter was closer than usual, and Earth actually passed through the end of Halley's 24-million mile long tail.
Throughout history comets have elicited fear and dread. They have even been seen as harbingers, if not the causes, of dreadful things like earthquakes, volcano eruptions, wars, epidemics, fires, and even massacres. (Isn't it curious how natural events are so often blamed for human-caused catastrophes?)
When scientists announced that Halley's tail contained traces of cyanide, though not nearly enough to be of concern, the last part of the message wasn't heard by all. While some panicked, others cashed in on the irrational fears by selling "anti-comet" pills and "comet-protecting gas masks." Of course, Halley's Comet passed uneventfully, only to return in another 76 years and help inspire me to begin writing this column.
- Next Two Weeks. Avg. sunrise: 6:28 a.m.; avg. sunset: 8:23 p.m. (exact for Waco, TX).
* Early this evening the crescent Moon is below Venus low in the west, and above the brilliant planet tomorrow evening.
* Wed. evening the Moon is below Mars.
* The Moon is at 1st quarter Thursday.
* The Moon is below Saturn the night of May 22.
* The May 27 full Moon, called Milk Moon, Flower Moon, Corn Moon, and Planting Moon, accompanies Scorpius' bright reddish star Antares across the sky all night.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.) Evening: "Evening star" Venus dominates the early evening sky in the west; Mars is high in the southwest; Saturn is high in the south. Morning: Jupiter, now rising 3+ hours before sunrise, is well up in the southeast by morning; Mercury is at its best late in the month low in the east at dawn.
May 1, 2010
Stargazer #530
The Missing Milky Way
If you go outside soon after dark and look up, you might notice the Milky Way seems to be missing. Fortunately, there's no cause for alarm. The month of May is the one time of year when the most dense part of our galaxy, that breathtaking band of concentrated starlight stretching from horizon to horizon, isn't visible in the early evenings.
Of course, if you live in an urban area (like most of humanity) light pollution made the Milky Way disappear from your night sky long ago. (We'll talk more about light pollution in a future column.) But even from the darkest sky, you won't now see the Milky Way unless you stay out a few hours.
Our galaxy, a huge swarm of a hundred billion or more stars, is shaped like a pancake with a bulge in the center. Since we're inside the pancake, all we see with our naked eyes, even under the darkest sky, are stars and other objects within our home galaxy. (A couple of faint galaxies can barely be seen with naked eyes, but most require binoculars or telescopes.)
So to be precise, virtually everything we see every night is in our Milky Way galaxy, however when we speak of "seeing the Milky Way," we're referring to the most densely concentrated band of stars along the plane of the pancake.
The part of the Milky Way we seen in the summer, specifically in the direction of Sagittarius and Scorpius, is toward the galaxy's center, making the summer Milky Way the richest of the year. During the other seasons, when we're looking in other directions along the galaxy's plane, the view isn't as dramatic.
So, why can't we see the Milky Way in the early evenings of May? It's the only time of the year when the galaxy is laying around the horizon, on the same plane with what appears to be the "flat" Earth around us. If you have clear views of the horizon in all directions, you might barely see it hovering just above the horizon, but for all practical purposes, it seems to have temporarily disappeared.
But not to worry -- it won't stay hidden long. As the Earth rotates on its axis, in a few hours the Milky Way will gradually reappear as it rises above the eastern horizon -- and the part that rises first is the magnificent Scorpius-Sagittarius central region. So be prepared to be dazzled.
- Next Two Weeks. Avg. sunrise: 6:37 a.m.; avg. sunset: 8:13 p.m. (exact for Waco, TX).
* Today is May Day, also called Beltane, a cross-quarter day celebrating the middle of spring.
* Wed. morning, the Moon is at 3rd quarter.
* The morning of May 9, the crescent Moon is above Jupiter low in the east before dawn.
* The Moon is new May 13.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.) Evening: Venus is low in the west, Mars is high in the west, and Saturn is high in the southeast. Morning: Jupiter rises 2 hours before sunrise.
- Star Party. The Central Texas Astronomical Society's free monthly star party is Saturday, May 8 at the Lake Waco Wetlands beginning at 8 p.m., weather permitting. For directions to the Wetlands, see MAPS & DIRECTIONS elsewhere in this Web site.
April 17, 2010
Stargazer #529
Happy 20th Birthday HST
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April 25 marks the 20th anniversary of the much-anticipated deployment of the Hubble Space Telescope by Discovery space shuttle astronauts in 1990. Then to the dismay of scientists and the public, it was quickly found that the HST had an optical defect that seriously degraded its views. However, once corrective optics were installed in 1993, the magnificent telescope has been revealing a universe never before known in such depth and grandeur.
In 1609-1610, Galileo and his new telescope revolutionized astronomy by revealing a cosmos humans had scarcely imagined, much less seen, and altered our understanding of our place in the universe.
Then in 1924 a young American astronomer, Edwin Hubble (1889-1953), again revolutionized astronomy. The then-prevailing theory was that our Milky Way galaxy constituted the entire universe. But using the then-largest telescope in the world, the 100-inch Hooker Telescope on Mt. Wilson near Los Angeles, he discovered the universe to be vastly larger than had been imagined, and that our galaxy is but one of billions of galaxies.
Many argue that the HST, named for Edwin Hubble, has been no less revolutionary. It has enabled astronomers to determine the age of the universe (13.7 billion years) and confirm that supermassive black holes reside at the center of most galaxies. It has enabled scientists to better understand how stars and planets are formed and has detected organic molecules beyond our solar system, increasing the possibility for the existence of other organic life in the cosmos. In its 20-year history, data from the HST has generated over 7,500 scientific papers, making it one of the most productive scientific instruments in history.
Although not the largest telescope in the world, HST's 94-inch (diameter) mirror is larger than McDonald Observatory's original 82-inch telescope which is still in use. At 43 feet long and 14 feet in diameter, our Toyota 4Runner and 23-foot travel trailer could park inside the body of the HST. It also has two rectangular solar panels, each 8.5 feet by 23 feet.
If you want to see the HST in the night sky, the Web site www.heavens-above.com provides exact viewing information on many Earth-orbiting satellites, including the HST. You'll need to register (free) and enter your viewing location the first time you use the site, but then you won't need to do it again.
- Next Two Weeks. Avg. sunrise: 6:50 a.m.; avg. sunset: 8:03 p.m. (exact for Waco, TX)
* Tonight and for the next few nights, Mars passes very near the Beehive star cluster high in the west -- a sight best seen in binoculars.
* Wed. night the 1st quarter Moon is below Mars.
* The Lyrid meteor shower which peaks Thur. morning is best seen after the Moon sets at 3 a.m.
* The evening of Apr. 25, Venus passes near the Pleiades (Seven Sisters) star cluster low in the west at dusk.
* The Apr. 28 full Moon is called Egg Moon, Grass Moon, and Easter Moon.
- Naked-eye Planets. Evening: Brilliant Venus is low in the west with much fainter Mercury to its lower right, Mars is high overhead, and Saturn is high in the southeast. Morning: Before dawn Saturn is setting in the west as Jupiter is rising in the east.
- Star Party. The Central Texas Astronomical Society's free monthly star party is tonight at the Lake Waco Wetlands beginning at 8 p.m., weather permitting. For directions to the Wetlands, see MAPS & DIRECTIONS elsewhere in this Web site.
April 03, 2010
Stargazer #528
The "Evening Star" Points to Mercury
Even though it's often brighter than the brightest stars, Mercury is always a challenge to spot. Being the planet nearest the Sun, its elusiveness derives from its proximity to our blindingly bright star.
While we might tend to forget it, the daytime sky is just as full of stars as the nighttime sky. We just don't see them since they are obscured by the glare of the Sun. Likewise with Mercury. Since it orbits close to the Sun, it is up virtually all day every day, but it, too, is hidden by the Sun's glare.
During about half of Mercury's orbit, it is either behind the Sun or between Earth and Sun, and thus too near the Sun for us to see. But there are two windows of opportunity in its orbit when it can be seen, even if briefly and with some effort.
Three to four times each year Mercury can be seen, usually for a couple of weeks, low in the east in the morning as dawn breaks, and likewise, three to four times low in the west in the evening at dusk.
Since Mercury's orbit is highly elliptical (it deviates notably from a perfect circle), some of its appearances are better than others. When it is farther from the Sun than usual, it can be seen sooner before sunrise or longer after sunset, and can be spotted a bit farther from the horizon.
It is now having its best appearance for this year, and to our good fortune, it is near "evening star" Venus, making it easier to spot. The two are low in the west at dusk and remain above the horizon more than an hour after sunset. As they are low, you'll need a viewing site with a good view of the western horizon.
Begin looking soon after sundown. The much brighter Venus will appear first; then a few minutes later Mercury will pop into view to Venus' lower right. Binoculars can help spot Mercury sooner although as the sky darkens a bit, it will become visible to naked eyes.
The two are at their nearest Apr. 4 with Mercury six moonwidths to Venus' lower right. Mercury is at its farthest from the setting Sun Apr. 8.
A week later a guest joins the pair for a special show. Apr. 15, a very thin the crescent Moon is three moonwidths to the upper right of Mercury with Venus farther to their upper left. Then the next evening, the Moon is above the two planets just below the lovely Pleiades (Seven Sisters) star cluster.
While this is Mercury's best appearance for 2010, its best morning appearance is in mid September, although Venus won't be nearby.
- Erratum: Thanks to teachers Steve Salvesen and John Herbert and their Lake Waco Montessori 5th graders for noting an error in last column's diagram. The Moon, of course, orbits the Earth as it now states in the diagram.
- Next Two Weeks. Avg. sunrise: 7:06 a.m.; avg. sunset: 7:54 p.m. (exact for Waco, TX)
* This morning the Moon is two moonwidths above the star Antares in the south.
* The Moon is at 3rd quarter Tues.
* The morning of Apr. 11 the crescent Moon is above Jupiter low in the east at dawn, then to the planet's left the next morning.
* The Moon is new Apr. 14.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.) Evening: Venus and Mercury are low in the west with Saturn well up in the southeast and Mars high overhead. Morning: An hour before sunrise, Saturn is setting in the west as Jupiter is rising in the east.
March 20, 2010
Stargazer #527
The Lunar Math of the Moon's Phases
Only in the night sky does a quarter equal a half and a half is full. It's not new math -- it's lunar math. When we see a first quarter Moon, it looks like a half moon, so perhaps you've wondered why it's called quarter.
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Like planets, the Moon emits no light but rather reflects sunlight as it orbits Earth every four weeks (more precisely, 29.53 days). When it's between Earth and Sun at new Moon, we don't see it as the Sun illuminates the side facing away from us.
A day or so after new Moon, we begin seeing a slight sliver soon after sunset, called a waxing crescent -- waxing because it gets more illuminated each night and crescent because of its appearance from our perspective.
In a week, when it has traveled a quarter of the way around Earth, its 1st quarter phase looks half-lighted to us.
Then for the next week as the Moon continues to wax, it appears more than half illuminated, but less than full -- a phase called gibbous (Latin for hump).
After two weeks, the Moon has completed half its journey and is on the opposite side of Earth from the Sun which illuminates the entire half of the Moon facing us -- called a full Moon.
Then for the next two weeks, the Moon become less illuminated each night, called a waning Moon. During the third week it is in its waning gibbous phase on its way to 3rd quarter (sometimes called last quarter) when it again appears half illuminated.
And during the last week of it sojourn, it is in its waning crescent phase (seen in the morning sky) until it again reaches new Moon and starts its next monthly cycle.
Regardless of how much of its surface we happen to be seeing on any given night (or day), half of the Moon, just like half of the Earth, is always illuminated -- whichever half is facing the Sun.
- Next Two Weeks. Avg. sunrise: 7:24 a.m.; avg. sunset: 7:45 p.m. (exact for Waco, TX)
* Today is the spring (vernal) equinox, the Northern Hemisphere's first day of spring when day and night are each (about) 12 hours long.
* Tonight a crescent Moon grazes the Pleiades star cluster, a sight best seen in binoculars; the reddish star to their upper left is Aldebaran, the "red eye" of Taurus the bull.
* Tomorrow Saturn is at opposition on the opposite side of Earth from the Sun; it rises at sunset, is up all night, and sets at sunrise.
* The Moon is at 1st quarter Tues.
* Wed. evening it is to the lower right of Mars, and then to the planet's lower left the next night.
* The night of Mar. 28, the Moon accompanies Saturn across the sky.
* The Mar. 29 full Moon is called Lenten Moon, Sap Moon, Crow Moon, and Worm Moon.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.) Evening: Saturn is low in the east with Mars high overhead; Venus is very low in the west after sunset. Morning: Saturn, low in the west, is now the only morning planet.
March 6, 2010
Stargazer #526
Galileo's Sun and Ours
Everyone knows the Sun is a brilliant round ball that travels around Earth each day. Perfect and unchanging, it is made of shiny quintessence, a heavenly substance not found on Earth.
At least that's what sophisticated Europeans thought in the early 17th century when Galileo and others began studying the heavens with the newly invented telescope 400 years ago.
That view of the Sun began to crumble when Galileo and other early astronomers discovered sunspots. They seemed to be clear evidence that the Sun wasn't perfect after all. Further, the sunspot blemishes came and went and changed sizes, demonstrating that the Sun isn't unchanging. And seeing the sunspots move across the Sun's surface indicated that the Sun was rotating on its axis. However, neither Galileo nor his contemporaries had any idea what sunspots were, or what the Sun was made of.
Galileo's observations, especially of Jupiter and Venus, also led him to accept Copernicus' theory that the Sun doesn't go around the Earth, but rather Earth and the other planets go around the Sun. And as mentioned in previous columns, his promotion of these heretical ideas got him in serious trouble with the ecclesiastical-governmental authorities.
Today, of course, the Sun-centered view of our solar system is universally accepted, and we have a much better understanding of the nature of our Sun.
An ordinary star, the Sun is a huge gaseous ball composed not of any exotic heavenly substance but primarily of hydrogen, the most common element in the known universe. It's heat, light, and other forms of energy come from nuclear reactions deep within its core.
At its center, the temperature is 27 million degrees whereas the temperature at the visible surface (called the photosphere) is a mere 10,000 degrees. The sunspots which so intrigued and baffled Galileo are now known to be areas of magnetic disturbance; they are darker in appearance because they are cooler.
And finally, our Sun, like all stars, is not eternal. It was born 5 billion years ago and will die in another 5 billion years.
[Much of this information is from Stephen P. Maran and Laurence A. Marschall's book, Galileo's New Universe, reviewed in this column; my Web site contains an archive of previous columns.]
- Next Two Weeks. Avg. sunrise: 6:41 a.m.; avg. sunset: 6:35 p.m. (exact for Waco, TX)
* The Moon is at 3rd quarter tomorrow and new Mar. 15.
* The evening of Mar. 16 a very thin crescent Moon is to the lower right of Venus low in the west at dusk, and above the planet the next evening.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.) Evening: Mars is high in the east as Saturn rises an hour after sunset; Venus is visible very low in the west after sunset. Morning: Saturn, low in the west, is currently the only morning planet. Mercury and Jupiter are now in the Sun.
- Star Party. The Central Texas Astronomical Society's free monthly star party is tonight at the Lake Waco Wetlands beginning at 7 p.m. For directions to the Wetlands, see MAPS & DIRECTIONS elsewhere in this Web site.
- Astro Milestones. Mar. 13 is the birthday of William Herschel (1738-1822) who discovered the planet Uranus in 1781 from Bath, England. Mar. 14 is the birthday of Albert Einstein (1879-1955), who set forth the theories of relativity in the early 1900s.
- Time Change. Set clocks forward ("spring forward") to Daylight Saving Time next Sunday, Mar. 14, at 2 a.m.
February 20, 2010
Stargazer #525
Where the Months Got Their Names
Since the earliest times, the natural cycles of the Sun and Moon have been used to measure intervals of time. Solar cycles define days, years, and seasons while the Moon marks off months ("moonths").
There are two major lunar cycles, the best known being the 29 1/2-day synodic month during which the Moon goes from new Moon to new Moon. ("Synodic" refers to the meeting of the Sun and Moon). Less apparent is the 27 1/3-day sidereal month which is based on the Moon's position as seen against the background stars. If Earth wasn't orbiting the Sun, synodic and sidereal months would be equal, but since we are moving, the synodic month takes longer.
In a sidereal month, the Moon travels 360 degrees (one complete circle) around Earth before re-passing the same background stars. During this time, however, Earth has traveled nearly 1/12 of the way around the Sun, meaning the Moon must travel nearly 390 degrees, and two more days, before reaching the next new Moon.
A year being 365 1/4 days, there is not an even number of synodic or sidereal months in a year. This was not a problem for cultures who referred to these intervals by the names they gave full Moons, like Harvest, Hunter's, and Long Night Moon.
But when our ancestors devised formal calendars, adjustments were required, like adding or subtracting days and even ignoring periods of time. These months approximate but no longer exactly correspond with the lunar cycles. The names we use for our months derive from the Romans and their Latin language.
Originally, the Roman year had 10 months that began with March, named for Mars, the god of war. The second month, April, was named for Aphrodite (Venus), the goddess of love and beauty. May is the month of Maia, goddess of spring. June honors Juno, goddess of women, childbirth, and marriage.
July was originally called Quintilis (quintus being Latin for fifth) as the fifth month; it was renamed by Julius Caesar in 46 BCE to honor himself. Similarly, August, first known as Sextilis (sex = six) as the sixth month, was changed by Augustus Caesar.
The next four retained their Latin numeric names: September (septem = seven) as the seventh month, October (octo = eight) as the eighth month, November (novem = nine) as the ninth month, and December (decem = ten) as the tenth month.
The winter months apparently went unnamed until about 700 BCE when the eleventh and twelfth months were added. January was named for Janus, the double-faced god of beginnings and endings who could see the past and the future. February came from Februa, the festival of purification.
So like the names we use for many constellations, as well as the days of the week, the names of our months were invented by our ancient ancestors.
- Next Two Weeks. Avg. sunrise: 6:58 a.m.; avg. sunset: 6:24 p.m. (exact for Waco,TX)
* The Moon is at 1st quarter tomorrow (Sunday).
* Thursday evening (and all night), Mars is to the left of the bright gibbous Moon.
* The Feb. 28 full Moon is called Wolf Moon, Snow Moon, and Hunger Moon.
* The evening of Mar. 1, the Moon is to the right of Saturn as they rise around 8 p.m. and accompany each other across the sky all night; by morning the Moon is to Saturn's lower left.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.) Evening: Mars is prominent high in the east as Saturn rises some two hours after sunset. Morning: Saturn is in the west southwest.
February 6, 2010
Stargazer #524
Pluto and New Horizons
Feb. 18, 1930, 24-year old Clyde Tombaugh discovered a faint, remote object on photographic plates he had taken Jan. 23 & 29 from Lowell Observatory in Flagstaff, Arizona. Astronomers credited him with discovering the ninth planet orbiting the Sun, and it was named Pluto.
It was so distant -- further than Neptune -- and so small and faint that for several decades little was learned about Pluto beyond its orbital characteristics.
During the explorations of the 1970s and 1980s, knowledge about our planetary neighbors was greatly expanded when space craft landed on or flew by every other planet, except Pluto. And we've still not visited Pluto, but that's about to change.
Jan. 19, 2006, NASA's New Horizons spacecraft began its 9 1/2 year journey to the planet Pluto and beyond. But ironically before the craft even left the inner solar system, planet Pluto ceased to exist.
In July 2006, the International Astronomical Union, in a highly publicized and controversial decision, redefined "planet," and Pluto was reclassified as a dwarf planet. It is now seen as one of the largest objects in the Kuiper belt, a swarming cluster of small icy objects orbiting the Sun beyond Neptune -- similar to asteroid belt, the swarming cluster of small rocky objects orbiting between Mars and Jupiter.
In July 2015 New Horizons will fly past Pluto and its three moons making them the most remote objects to be studied up-close. It won't land but after zooming within 6,000 miles of Pluto, it should return images to dazzle our imagination and enough data to keep scientists busy for years.
If funding is available, New Horizons will continue its exploratory journey with fly-by visits to one or more other more distant Kuiper Belt objects between 2016 and 2020. To read more about the New Horizons mission, visit www.pluto.jhuapl.edu.
[Image: Artist's conception of the New Horizons spacecraft as it approaches Pluto and its three moons in summer 2015. / Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute]
- Next Two Weeks. Avg. sunrise: 7:12 a.m.; avg. sunset: 6:14 p.m. (exact for Waco, TX)
* Tomorrow morning the crescent Moon is to the upper right of Scorpius' brightest star Antares low in the southeast.
* Thursday morning the crescent Moon is to the upper right of Mercury very low in the east southeast at dawn, and then to the planet's lower left the next morning.
* The Moon is new Feb. 13.
* The early evening of Feb. 14 Jupiter is four moonwidths above brighter Venus with an ever-so-thin crescent Moon to their left near the west southwestern horizon; they will become visible soon after sunset and set soon thereafter; binoculars will help.
* Then the early evening of Feb. 16 Jupiter is one moonwidth to the right of Venus very low in the west southwest just after sunset.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.) Evening: As twilight ends, Jupiter is setting in the west as Venus begins its stint as the "evening star;" Mars is still prominent in the east. Morning: At dawn Mercury is very low in the southeast, Saturn higher is in the southwest, and Mars is setting in the west northwest.
- Star Party. The Central Texas Astronomical Society's free monthly star party is tonight at the Lake Waco Wetlands beginning at 7 p.m., weather permitting.
For directions to the Wetlands, see MAPS & DIRECTIONS elsewhere in this Web site.
- Astro Milestones. Feb.15 is the 446th birthday of Galileo Galilei (1564-1642). Feb. 19 is the 537th birthday of Nicolaus Copernicus (1473-1543).
January 23, 2010
Stargazer #523
Mars Closest for This Trip Around the Sun
If you've been out in the early evening lately, perhaps you've noticed Jupiter, which has been dominating the evening sky the past several months, now sinking closer to the setting Sun in the west. And if you turned around and looked behind you, perhaps you've also noticed another star rising after dark and dominating the sky in the east, that "star" being the planet Mars.
Traveling nearly 67,000 miles per hour, Earth orbits the Sun once each year. Mars, the next planet out from the Sun, moves only 54,000 miles per hour, has further to travel, and thus takes nearly two Earth-years to orbit the Sun.
Since we speed around the Sun more quickly, we regularly pass between Mars and the Sun about every two years. When we do, Mars is on the opposite side of Earth from the Sun, which astronomers call opposition -- and this is about to occur Jan. 29.
At opposition, Earth and Mars pass nearest each other making Mars appear larger and brighter than usual. So now and for the next few weeks, Mars outshines all the brightest stars (except Sirius which is now in the southeast in the early evening.)
If Earth and Mars orbited the Sun in perfect circles, Mars would appear the same size and brightness at each opposition. But since their orbits are elliptical, at some oppositions Earth and Mars pass nearer than at others. On average we pass within 48 million miles (rounding to the nearest million), but the distance can be as little as 34 million miles or as much as 64 million miles.
This time around, we're passing at 62 million miles, so this is not one of Mars' more spectacular oppositions although it will still be well worth noting. (Perhaps you recall the excitement in August 2003 when Mars passed less than 35 million miles and was extraordinarily bright -- that was pretty spectacular.)
All the planets further out from the Sun come to opposition regularly. The period between Jupiter's oppositions is about 13 months, and for the more distant Saturn, Uranus, and Neptune, just over a year.
At opposition, planets rise around sunset, are up all night, and set around sunrise. And since they are then at their largest and brightest, the few weeks before and after opposition are the best times for observing them.
By coincidence, on the night of Mars upcoming opposition, it has a companion to escort it across the sky -- the almost full Moon. And then the first week of February, the Red Planet passes near the lovely Beehive star cluster. They will be in the same binocular field of view several nights in a row -- a sight you won't want to miss.
- Next Two Weeks. Avg. sunrise: 7:23 a.m.; avg. sunset: 6:01 p.m. (exact for Waco, TX)
* The Moon is at 1st quarter tonight.
* The Jan. 30 full Moon is called Old Moon and Moon After Yule.
* Feb. 2, commonly known as Groundhog Day, is also Candlemas, a cross-quarter day celebrating the middle of winter.
* The morning of Feb. 4, the gibbous Moon is below Virgo's brightest star Spica high in the south.
* The Moon is at 3rd quarter Feb. 5.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.)
* As evening twilight ends, Jupiter is setting in the west as Mars is rising in the east.
* At the first light of dawn, Mercury is very low in the southeast, Saturn is in the southwest, and Mars is in the west.
January 9, 2010
Stargazer #522
Twenty Years of Stargazer
With this column, Stargazer, first published in January 1990, is 20 years old. And there's more than one irony associated with its existence.
Back in 1958, had anyone predicted to my University of Texas freshman English instructor that her immature 18-year-old student would become a published writer, she would have laughed while marking another "D" on yet one more of my weekly 500-word themes.
Not only did I have poor writing skills, but I had to struggle to come up with 500 words on the topics we were assigned. Now, every other week, I struggle to keep my column down to the 500-word range.
For reasons I still can't fathom, amateur astronomy is a hobby dominated by males, yet three women are largely responsible for helping me launch Stargazer.
In 1954 as a 14-year-old growing up on the banks of Galveston Bay, it was 81-year-old Margaret Willits who lit the stargazing flame in me. I was amazed as she pointed out stars and told me their names, outlined constellations, and knew which "stars" were really planets. She described seeing Haley's Comet in 1910, and told me some day I could see it for myself -- a day that came in 1986.
Years later in late 1989, I came up with the idea of a column, drafted four pilots, and submitted them to my hometown newspaper, the Waco Tribune-Herald. In her rejection letter, then-managing editor Barbara Elmore offered some helpful critique and invited me to resubmit if I cared to.
Disappointed, but also encouraged, I asked journalist friend Becky Gregory (who is now the Trib's managing editor!) to give my pilots a no-holds-barred assessment -- and, boy, did she ever. Her multi-page response, akin to a Journalism 101 crash course, was incredibly helpful. I rewrote and resubmitted the pilots, and the Stargazer column was born.
In 1998 I retired from my career as social worker and college professor and began devoting more time to my amateur astronomy passion. In 2002, I began offering Stargazer to other newspapers, and it now appears in some 65 papers in 5 states.
The free email version of the column goes out to 200 people in 21 states and 7 countries, and is archived on this Web site.
As I approach my 70th birthday still loving the stars, I anticipate many more Stargazers, and I welcome your letters and emails with comments and questions. I answer every one.
- Next Two Weeks. Avg. sunrise: 7:28 a.m.; avg. sunset: 5:49 p.m. (exact for Waco, TX).
* Monday morning a thin crescent Moon nearly grazes the star Antares low in the southeast before dawn.
* Wednesday morning a thinner crescent Moon is to Mercury's lower right near the eastern horizon as dawn breaks; binoculars will help.
* Friday's new Moon produces an annular eclipse of Sun which unfortunately won't be visible here.
* The evening of Jan. 17, a crescent Moon is to the lower right of Jupiter low in the west at dusk.
* The following night the Moon is above the king of the planets.
- Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth's west-to-east rotation on its axis.)
Evening: Jupiter is setting in the western sky as Mars is rises in the eastern sky.
Morning: Mercury is very low in the east, Saturn is high in the south, and Mars is in the west. Venus is now in the Sun.
- Star Party. The Central Texas Astronomical Society's free monthly star party is tonight at the Lake Waco Wetlands beginning at 7 p.m., weather permitting. For directions see my Web site.
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