The bright stars of the Summer Triangle shine from high in the southern skies during the evenings in September. Three bright stars — Vega, Deneb, and Altair — that are actually part of the their own constellations, mark the “corners” of the triangle. Deneb is one of the brightest stars in the sky. Shining with the brightness of 170,000 suns, this star is 2,500 light years away. The combination of actual brightness and distance makes it the 19th brightest star seen in the sky at night. Compared to its neighbor, Vega appears as the 5th brightest star, although it is only 60 times brighter than our sun and 25 light years distant. The third star, Altair, ranks as the 12 brightest star with an actual brightness of about 11 suns with a distance of 17 light years. The brightness that a star appears in our sky is related to the star’s actual brightness and distance.
Deneb is part of the constellation Cygnus, the swan. It represents its tail. The head of the swan is marked by Albireo. Look at this star through a small telescope. It will reveal a wonderful double star, one golden, one blue.
|Moon Phases September 2011|
On September 3, the moon appears near the bright star Delta Scorpii as seen from mid-latitudes. The moon can been seen covering the star from the southeastern US. This link provides more details. For others, the moon appears very close to the star with the bright star Antares nearby.
The Autumnal Equinox occurs at 4:05 a.m. CDT on September 23. At this time, the sun is directly above the earth’s equator. On this date at noon the sun will go directly overhead for people living at the equator. For residents of mid-latitudes, the sun will about halfway up in the south at noon, rising at the east direction point and setting at the west cardinal direction. The equinox also brings equal daylight and darkness at 12 hours each. From this date until the Vernal Equinox in March, the length of nighttime is longer than daylight hours.
Mercury is usually difficult to see as it rapidly shuttles from morning sky to evening sky. During early September, Mercury makes a brief appearance in the morning sky. The chart above shows Mercury and Regulus, the bright star in Leo, at 6 a.m. on September 9. Locate an observing spot with a clear horizon. Looking with binoculars locate Mercury and Regulus in a close pairing.
Venus begins its evening appearance late in the month. Venus passed behind the sun in mid-August. Venus and Earth are like two cars on a race track; Earth is in an outside lane and Venus an inside lane. Along with a shorter course, Venus moves faster than Earth. In September, Venus is nearly on the other side of the track and the infield spectators (the sun) are blocking our view of the planet. It will move faster and catch up to our planet and move between us in the sun (inferior conjunction) in June 2012.
As the chart above indicates, the sunset time between Venus and sun will be between about 30 minutes and 45 minutes throughout September. Sharp observers may note it very close to the horizon in the west after sunset. Binoculars will be helpful. As Venus begins to catch up to Earth, it will appear longer and longer in the western evening sky, outshining all other objects in the night sky besides the moon. It can be easily mistaken for lights on an airplane.
As Venus closes in on Earth, it will grow brighter until April 30. The greatest separation (marked greatest elongation on the diagram) between Venus and the sun is March 27, 2012, with Venus setting nearly 7 hours after the sun. It’ll be a spectacular sight in the spring night sky, when the tilt of the solar system provides marvelous views of the inner solar system. Venus will make interesting viewing as it passes bright stars and other planets during its evening appearance. We will note them here in future postings.
Mars is visible in the eastern, predawn sky. Late in the month, the moon appears near Mars. The chart above shows Mars with the moon and bright distant stars (Pollux, Castor, and Procyon) on September 22 and 23. During September, Mars shines nearly equal to the bright stars in its background. While distinctly reddish-orange, the moon helps identify it late in the month.
Jupiter shines brightly from the eastern sky during late evenings as it rises in the east around 10 p.m. early in the month. It is in the sky until sunrise and it dominates the southern sky just before sunrise. Late in the month, it rises in the east around 9 p.m. The chart above shows the moon and Jupiter on September 15 and September 16. The bright star Hamal is nearby.
Saturn disappears into the sun’s bright sunlight as it moves behind the sun in October.
We’d appreciate reading what you are observing. Please post any interesting observations in the comments section.
The player above is for the Abrams Planetarium Podcast for August 2011
Let’s start this month’s sky watching with an “extra for experts.” Mercury is an elusive planet and usually very difficult to see. It is best seen during either autumn mornings or spring evenings when the plane of the solar system makes a very favorable angle with the horizon. Mercury is visible late in the month about 30-45 minutes before sunrise. With binoculars and with a good view of the natural horizon, look for it low in the eastern sky. A thin crescent moon is nearby about 30 minutes before sunrise on August 27.
Venus is not visible during August. It is at superior conjunction on August 16; that is, it is behind the sun and lost in the bright sunlight of daytime.
Mars is a morning star in front of the stars of Gemini, starting to rise early enough to be seen in a dark sky in the east. While visible throughout the month in the predawn eastern sky, it rises around 3:30 a.m. at mid-month, later earlier in the month. On the morning of August 25, the moon is nearby as shown in the chart above. Castor and Pollux, the Gemini Twins, are nearby throughout the month.
Jupiter shines brightly in the predawn sky throughout the month. It easily outshines the other stars in that region of the sky. On the morning of August 20, the moon appears near Jupiter and Hamal, the brightest star in Aries.
Saturn shines from the western sky throughout August. The moon passes near Saturn early in the month as shown in the diagram above. The bright star Spica is nearby.
The chart above shows the planets on August 15, 2011.
In early August the moon passes in front of the stars of Scorpius during the early evening hours. One bright star, Antares, makes a nice pairing with our lunar neighbor on the evening of August 7th. The stars do not have vivid colors, although Antares shines in a ruddy color. The star’s name is sometimes translated as the “Rival of Mars.” Ares is the Greek version of the god of war (Mars).
Antares is quite unusual. Its distance is measured at about 600 light years. A star like our sun is not visible at that distance without the assistance of a telescope. Antares is known as a red supergiant. In the final stages of its life cycle, it shines at the brightness of 65,000 suns. It is enormous with a volume that, if empty, would hold over 500 million stars the size of our sun. Placed in our solar system, its volume would extend into the vicinity of Jupiter, some 480 million miles from the center of our solar system.
Antares lies to on the west side of the Milky Way, the greatest density of stars, that outlines the plane of the galaxy by the same name. The Milky Way stretches high in the eastern sky and then into the north. As August evenings progress, the great mass of stars rises higher in the sky. The faint Milky Way glow can be seen during times when the moon is dimmer, such as before First Quarter and after Last Quarter, and in the countryside that is free from the glow of bright streetlights. The time-lapse video above shows the Milky Way rising. In the movie look carefully for Antares as it rises and it is low in the sky to the west (right) of the Milky Way. The movie is made in the spring when Antares and the Milky Way rise later in the night.
Take a look at the sky events and tell us what you are observing on the comments section of this posting.
|New||7/1 & 7/30|
July has two new moons. As infrequent as two full moons in a month, popularly known as a “blue moon,” the two-new-moon month has no official astronomical name. The “blue moon” designation has no official astronomical name, but somewhat goes along with the “once in a blue moon” phrase. Additionally, sometimes after volcanic eruptions, ash in the atmosphere gives the moon a bluish cast. Since these eruptions are infrequent, the blue moon color effect related to these events is also very infrequent. The second new moon in a month is sometimes called a “black moon” in some circles — though again this event has no official name.
In celebration of the beginning of summer 2011!
June 2011 Moon Phases
New June 1
First Quarter June 8
Full Moon June 15
Last Quarter June 23
The month of maximum sunlight opens with three bright planets in the predawn sky and Saturn in the evening sky. The amount of sunlight is consistent throughout the month, only gaining about 15 minutes of daylight from June 1 through the solstice on June 21. The maximum amount of daylight is 15 hours, 15 minutes in the Chicago area.
The chart below shows the predawn sky on June 2 at 4:30 a.m. in Chicago. Bright Venus is near the east-northeastern horizon with Mars to the upper right. Higher in the eastern sky is Jupiter. Quickly moving Mercury has disappeared into the sun’s glow, moving directly behind the sun (superior conjunction) on June 13. It appears low in the west-northwest at month’s end.
On the evening of June 2, look for the thin crescent of a new moon in the western sky. At 8:50 p.m., less than 29 hours after the new moon (in the Chicago area), look low in the west-northwest to see this young moon. You’ll need a good view of the natural horizon. While the photograph at the top of this posting is tilted at a different angle, the thin crescent represents the view. Additionally, during the next few nights, as the moon’s crescent grows and it appears in a slightly darker sky, the moon’s night portion will gently glow. While the moon is just past the new phase, from the moon, Earth is just past the full phase. Just as when the bright full moon, casts shadows and illuminates the terrestrial landscape, the nearly full Earth does the same to the lunar landscape. Look for this “Earthshine” on the moon during early June.
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As the moon moves through its celestial orbit and its phases, it will appear in the direction of Saturn on June 9 and June 10. Through a telescope, Saturn’s rings are tilted slightly. Saturn appears near the star Gamma Virginis, which itself a double star — two stars held together in a gravitational embrace, throughout the month.
Back in the morning sky, Jupiter rapidly moves higher, rising noticably early each week. By solstice day, Jupiter, Mars, and the Pleiades appear in the eastern predawn sky. As noted in the Sky Calendar panel for this date, the next visible grouping of Mars and the star cluster is in 2017.
With maximum daylight during June, the planetary display continues in the predawn sky. The golden jewel of the solar system, appears in the southern sky during the evening hours of the month.
The charts above show the planets on May 1 and May 2 at around 5:20 a.m. CDT in Chicago. On May 1, a thin crescent moon appears to the left of Venus. With binoculars or telescope locate Mars and Jupiter beneath it. The next morning, the moon is much lower, although the planets are visible again low in the eastern sky. This clustering of the planets is from a seemingly complex motion of the four planets and Earth.
Mercury is the fastest planet, revolving around the sun in 88 days, although it catches up to Earth and passes our planet every 115 days. That’s three times every year.
Venus revolves through its solar orbit every 224 days, but it takes 584 days (1 year, 7 months) to catch our moving planet.
Mars revolves around the sun slower than Earth, taking 1 year, 292 days for one solar revolution. Our planet catches Mars every 2 years, 51 days.
The fourth planet moves slowest. At its distance from the sun, Jupiter takes nearly 12 years to revolve around the sun and our faster moving planet catches up to and passes Jupiter in one year, one month intervals.
On April 9 Mercury passed between the earth and the sun and emerged into the morning sky. It climbed higher into the morning sky. On May 7, it reaches its greatest separation (elongation) from the sun as seen by Earth.
Venus has been in the morning sky for several months and it is slowly disappearing in the sun’s glare as to moves behind the sun on August 16. As the days and weeks, pass Venus appears lower in the sky until it disappears in the sun’s brilliant glare.
Mars appears to be emerging from behind the sun as our planet’s faster motion carries us around the sun faster. The combination of speeds makes Mars appear to move more slowly than we might think. This Red Planet moves at about half the speed of our planet so Mars appears to slowly move across the sky as compared to the other planets. Mars was directly behind the sun on February 4 and has slowly emerged from the sun’s glare since then.
While Jupiter revolves more slowly than Mars, our planet catches it sooner than it catches Mars. Its annual progression across our night sky is very similar to the stars. After conjunction, it appears in the morning sky, rising earlier each week. After several weeks, it rises around midnight. Then it rises around sunset as Earth passes between Jupiter and the sun. From that point it rises sooner each day. Before you know it, it appears in west just after sunset, shortly thereafter disappearing in the sun’s brilliant glare only to repeat the cycle. However, there is one small difference, Jupiter’s slight orbital motion carries it slightly eastward as compared to the stars during this sequence. So that in nearly 12 years, Jupiter has moved eastward on full circle in front of the stars behind the plane of the solar system, commonly known as the zodiac. As Mercury and Venus disappear into the sun’s glare after this display, Jupiter will rise rapidly in the morning sky when weekly observations are made. In comparison, Mars will not appear to move much as its orbital motion is only half our planet’s speed. For example, compare Jupiter’s position near the horizon in the May 1 diagram above and then again in the May 22 diagram below.
The chart below shows the relative position of the five planets and the sun on May 15, 2011, as viewed from north of the solar system. From Earth, all the planets appear nearly in a line. They are not easily observed because the line is near the brilliant sun.
As the month progresses, Jupiter appears higher in the sky, Mercury and Venus appear lower, and Mars appears nearly in the same place.
While all the planet clustering occurs in the morning sky, the moon appears near Saturn on the evenings of May 12-14.
With the changing weather patterns and increased daylight, May 2011 brings an interesting clustering of planets in the bright predawn skies. Use binoculars or a telescope; be patient; and watch the changing display of planets.
A note about the Abrams Planetarium Sky Calendar. The publication is an excellent way to learn about the sky. Written by expert sky watcher, Robert C. Victor, with an accompanying monthly sky map by D. David Batch, the Sky Calendar is written in calendar form that shows notable sky events that interested sky watchers can find. Victor uses the moon to help locate bright stars and planets. The calendar is published as a quarterly set, but subscriptions can start any time. Send $11 to Sky Calendar, Abrams Planetarium, Michigan State University, East Lansing, Michigan 48824.
For purposes of full disclosure, this writer studied planetarium and astronomy education at Abrams Planetarium, and received a master’s degree in the subject from Michigan State University. At the time, we graduate students were informally called “Abrams Interns.” Graduates have served at planetariums and astronomy education organizations across the world. Victor, Batch and other Abrams staff schooled us in how to connect with the public on observational astronomy. If we former Interns were in another field, we would be praising our Abrams mentors in our resumes and our bios. It was an honor to study with them and to see what they continue to do with constant commitment and devotion to their field of communicating astronomy to the public.
I received no compensation for this endorsement. TheSky Calendar is a worthy publication that needs our support. Subscribe today!
Podcast above is from Abrams Planetarium.
April 2011 brings more daylight hours. On April 1st, the sun is in the sky for about 12 hours, 45 minutes in the northern part of the United States. By April 30, the daylight hours increase to 14 hours.
Saturn is the only bright planet that shines throughout the night this month. The yellowish ringed planet rises in the eastern sky around sunset, is in the southern sky at midnight, and sets in the western sky near sunrise. On April 2, Saturn is at oppostion; that is, it is opposite the sun in the sky. At this time, our planet is directly betwen the sun and Saturn. Saturn takes nearly 30 years to revolve around the sun, but because of its slower speed, Earth catches up to and passes Saturn every 378 days (1 year, 13 days). In 2012, Saturn’s opposition is April 15.
On April 16, the moon appears near Saturn and Spica. Use the moon as a guide at mid-month to locate those objects. Saturn is distinctly yellow and the star Spica is blue in color. The chart above shows the moon, Saturn and Spica on April 16 at 9 p.m.
In contrast, Venus and Mercury are never seen at midnight from the skies of Earth. Both planets are between the earth and sun. Because of this geometry, the two planets are seen near sun, either in the west after sunset or in the east before sunrise. With Mercury being closer to the sun, it is rarely seen in a dark sky. Unless the moon, bright planet or bright star is the vicinity, Mercury goes unnoticed. In contrast, Venus is farther from the sun and can appear high in the east before sunrise or in the west after sunset. Because of its brilliance, Venus has been called the “Morning Star” or “Evening Star.” Generically, any bright planet can be given those names.
Mercury was visible in March in the evening sky. By early April, its rapid revolution carries it between the sun and Earth (inferior conjunction) and into the morning sky. During the past several weeks, brilliant Venus has moved farther from Earth, appearing low in the eastern predawn sky. The manner in which we view the solar system during spring mornings places the planets low in the sky.
Similarly, Jupiter was visible in the western sky at sunset during March. From our view on Earth, Jupiter passes behind the sun (conjunction) early in April and moves into the morning sky. Jupiter moves at about twice the speed of Saturn around the sun, yet Earth catches up and passes Jupiter every year and 34 days. In contrast, Mars moves about half the speed of Earth and our planet catches it every 2 years, 50 days.
In late April 2011, four planets are clustered near the horizon. This occurs in bright twilight, so a binocular or telescope is necessary to locate these objects. As shown in the diagram above on April 30 at 5:30 a.m., a crescent moon appears above bright Venus. Dimmer Mercury appears to the lower left of Venus. Both Mars and Jupiter appear just above the horizon.
The podcast player shown above for the month of March 2011 is from Abrams Planetarium.
March is a month of rapid change. Weather shuffles from the depths of winter into the promises of May. This year the Moon and planets provide interesting views during the early evening and early morning.
Early in the month, Jupiter, Mercury, and the moon appear in the western sky after sunset. The moon will appear as a very thin crescent. As the diagram above shows, the moon, just 46 hours past its new phase, and Jupiter make an interesting display during twilight on March 6 with elusive Mercury much lower and near the horizon. Houses, trees and other terrestrial features will block a view of Mercury. Binoculars will help locate it from a spot with a clear horizon. The accompanying chart shows the trio at 6:15 p.m.
Mercury is difficult to view, although twice each year in our planet’s celestial orbit, we can get an optimal view of the planet. During spring evenings and autumn mornings, we have an excellent view of the solar system objects that are near the sun. Because of Mercury’s solar proximity, it always sets before the sky completely darkens. During spring and autumn the solar system is oriented so that Mercury sets later than average or rises sooner than its average time, making it best viewed if it is appropriately placed in its orbit.
As the days of March step forward, watch Mercury climb higher in the sky each evening at 6:15 p.m. (Remember that Daylight Saving Time begins March 13. Beginning on that date the times will advance one hour.) By March 15, Jupiter and Mercury appear near each other at 7:30 p.m. (See the diagram above.) Mercury will continue to climb higher for another week and then rapidly dim and disappear into the sun’s bright glare by month’s end.
Venus, the crescent moon, and the star Antares make a bright sky watching configuration during the predawn hours of late January 2011. Venus entered the morning sky during November, and it has put on a bright display as it appeared near the moon, planets and bright stars during early mornings.
The chart above shows the Venus, the moon, and Antares at 5:45 a.m. on January 29, 2011. The bright trio appears low in the southeastern sky. The moon will appear near Venus and Antares on the day before the chart date and the following morning.
The moon appears near Antares each month as it travels its celestial orbit, but with the addition of Venus, the trio is visually attractive.
Venus is the nearest planetary neighbor outside the earth-moon system. On this morning it is 77 million miles from Earth. It is the brightest starlike object in the sky, with only the moon and sun regularly appearing brighter.
Antares is the bright star in Scorpius, marking the celestial scorpion’s heart. The star is quite unusual. It is around 600 light years away. Antares has a distinctive ruddy color, similar to that of the planet Mars. One interpretation of the star’s name is “the Rival of Mars” because both have nearly the same color and brightness.
While Mars is nearby and shines by reflected sunlight, Antares is a very large and bright star. Antares’ color indicates that it about half the sun’s temperature and so to shine as the 16th brightest star, it is about 400 times larger than our sun. Only Betelgeuse (the bright star at Orion’s shoulder) is larger in our region of the Milky Way. If the sun were replaced by Antares, the star would extend beyond the orbit of Mars; that is, the orbits of Mercury, Venus, Earth, and Mars would be inside the star!
As the days begin to lengthen again, slowly at first, look for the bright configuration of Venus, the moon, and Mars near the end of January.