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Astronomy From Your Backyard - 9/29 to 10/5 2010

By Dave Grosvold

The weather this week will be absolutely perfect for sky-watching, with low humidity providing above-average transparency all week and the temperatures low enough after dark to make it very comfortable.

By Wednesday, the Moon will not rise until 11:03 PM CDT, late enough that the glare will no longer interfere with evening observing. The Moon reaches Last Quarter at 10:53 PM CDT on Thursday evening, though it will not rise until after midnight. Moonrise occurs about an hour later each night.

With the Moon gone from the evening sky, now is the time to start looking for Comet 103P/Hartley (Hartley 2.) Comet Hartley 2 is just now becoming visible, reaching magnitude 5.9 on Wednesday evening. Comet Hartley 2 should brighten to magnitude 5.4 by Tuesday evening. The comet will continue to brighten in magnitude over the next three weeks.

Wednesday evening, 103P/Hartley lies in the north-northeast, in the constellation of Cassiopeia, the Beauty Queen, approximately 0.87 above Zeta Cassiopeiae. Over the course of the week, Comet Hartley 2 will track down to the southwest, as shown in the finder chart. At magnitudes dimmer than 5, you will need binoculars or a small telescope to see Comet Hartley 2 in any but the darkest of skies.

In late evening, as Jupiter rises high in the southeast, look for Fomalhaut, (pronounced FOAM-a-lot, or less commonly, FOAM-al-howt.) Fomalhaut is known as the Autumn Star, sparkling far to Jupiter's lower right in the south-southeast. The name Fomalhaut means "the mouth of the whale" in Arabic, and it is the brightest star in the constellation Piscis Austrinus, the Southern Fish.

Uranus, at magnitude 5.7, is only 1° to 1.5° to the left of Jupiter this week, still close, but you may need to move a few field-of-view widths in a telescope or binoculars to spot it. Neptune is also a relatively easy target early in the evening on the border between Capricornus, the Goat-Horn, and Aquarius, the Water Bearer. Can you see any color in Uranus and/or Neptune? There should be just the tiniest hint of pale green in Uranus and an equally pale blue in Neptune.

Even though Venus is at its brightest now at magnitude –4.8, it is becoming a thin, long crescent. Venus is sinking very low in the southwest during bright twilight, setting well before dark ahead of Mars, 6.5° to Venus's upper right all week. That's about one field-of-view width in a typical pair of 7 x 50 binoculars, which you'll definitely need to spot either of them.

Mercury is still very bright at magnitude -1, and is a fine morning target for planet watchers. Once again this week, look for it low in the east about 45 minutes before sunrise. It sinks lower as the week advances, getting lost in the glare of the sun by mid-next week.

After Venus sets, look to the west-northwest, and notice that five constellations form a line descending from the zenith down to the horizon. Remember from earlier articles that the zenith is the point directly overhead from your observing position. Near the zenith is the bright star Deneb: the head of the Northern Cross asterism, which is actually the tail of Cygnus, the Swan. Next down is Lyra, the Lyre, with the bright star Vega, then comes dim Hercules, the Kneeler, the then little Corona Borealis, the Northern Crown, and finally big Boötes, the Herdsman, with bright reddish Arcturus low in the west-northwest.

Hiding in Hercules is one of the most beautiful jewels of the night sky, the Great Cluster in Hercules (M 13,) the brightest globular cluster in the northern hemisphere. M 13 lies two-thirds of the way along the longest side of the Keystone asterism, a quadrangle in Hercules formed by the stars Pi (π,) Eta(η,) Zeta(ζ,) and Epsilon (ε) Herculis. Look about mid-way up to the zenith in the west-northwest for the Keystone, and then look to the north end of the longest side to find M 13,in a clear dark sky, it should be visible as a fuzzy patch slightly larger than a star. A telescopic view reveals a myriad of stars swarming around in a big ball — about a hundred thousand of them in all. M 13 is a spectacular sight on a crisp clear night like the ones we'll have this week, and should not be missed.
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Astronomy From Your Backyard - 9/22 to 9/28 2010

By Dave Grosvold

  
Wednesday evening, Jupiter and Uranus were almost directly below the full Harvest Moon, which is officially full at 4:18 AM CDT Thursday morning. Also on Wednesday evening, the Autumn Equinox for the Northern Hemisphere occurred at 10:09 PM CDT. This time of year, the equinox marks the beginning of Autumn at the point when daylight and darkness are the same length. The Full Moon closest to (either preceding or following) the Autumn Equinox is known as the Harvest Moon. In any given year, the Harvest Moon can occur as early as September 8th, or as late as October 7th.

This year, however, the Harvest Moon and the Autumn Equinox occur on the same night. Some astronomers refer to this event as a Super Harvest Moon. The coincidence of these two events happens about once every twenty years, and so the event is relatively rare. The “Super Harvest Moon” nickname seems to be a relatively recent invention, but as young as it is, it has made its way into the media this year.

  
One unusual aspect of a Super Harvest Moon is that “twilight” is truly what the term implies — two separate light sources, the Sun and the Moon, are directly opposite one another in the sky. Therefore the Earth is bathed completely in light from both sides. As a result, the evening light takes on an unusual appearance, and can be seen for about three days surrounding the Equinox.

Jupiter and Uranus are still very close together this week and can be spotted in a wide-field telescope or binoculars. See if you can pick out the Galilean Moons in a pair of binoculars as well.

This time of year after nightfall, the dim Little Dipper (Ursa Minor) is upside down (you'll need a fairly dark sky,) and looks like it's dumping water into the bowl of the Big Dipper (Ursa Major) far below it. Perhaps this is a harbinger of the coming autumn rains!

  
Venus, is very low in the southwest during brighter part of twilight. It sets before dark, but is visible as it is at its brightest point of the year at magnitude -4.8. Mars is quite a bit dimmer than Venus at magnitude 1.5, and is 6° or 7° to Venus's upper right all week. A pair of binoculars may mean the difference between spotting Mars or not.

Mercury is brightening from magnitude 0.0 to –0.8. Look for it low in the east about 45 minutes before sunrise. Look for Regulus twinkling above or to the upper right of Mercury, rising higher every morning. Regulus marks the base of the Sickle, an asterism in the constellation Leo.

Neptune and Uranus are both visible in the evening sky this week, but may take some patience to spot. As mentioned earlier, Uranus is very close to Jupiter and can be easily found in binoculars. Neptune, however, will probably require higher magnification. See last week's Backyard Astronomy article for help in finding Neptune.

On Monday and Tuesday evening, the waning gibbous Moon will not rise until after 9:00 PM, giving us a wonderful opportunity to get a good view of NGC 869 and NGC 884, a pair known as the Double Cluster, in the constellation Perseus. The Double Cluster is a beautiful pair of large open clusters that are actually visible to the naked eye when viewed from a dark sky. They can be found in the seemingly empty space between Perseus and Cassiopeia in the northeastern sky. A low-power view through binoculars or a telescope reveals a myriad of tiny points of light sparkling in the darkness. A beautiful sight for anyone!
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Astronomy From Your Back Yard - 9/15 to 9/21 2010

By Dave Grosvold

  
This week, the Moon is just past First Quarter, and shines to the left of the handle of the Sagittarius Teapot on Friday evening. Watch over the course of the next week, and you can observe the waxing gibbous Moon appear farther eastward in the sky at the same time each night.

This is a good time to view most of the planets in the Solar System. On Friday and Saturday evenings, Uranus will come within 0.8° of Jupiter. Uranus is easily visible in binoculars at magnitude 5.7, just to the north of mighty Jupiter, who is nearly 3,000 times brighter at magnitude –2.9. In binoculars or a small telescope with a low-power eyepiece, Pale-green Uranus appears about as bright as one of Jupiter's four Galilean Moons. Mercury is should be clearly visible low in the east about 45 to 30 minutes before sunrise all this week. It's easy to confuse Mercury with Regulus in the dim light of dawn. Regulus lies almost directly above it at the base of the Sickle of Leo.

Venus is now setting in the west before dark, and Mars is about 6° to the right, just above her. Mars is almost lost in the glow of sunset, so you may need binoculars to get a good view.

  
Jupiter reaches opposition on the night of Monday, the 20th. Opposition occurs when Jupiter is directly opposite the Sun in the sky as seen from Earth. Rising just after dusk in the east southeast, Jupiter is the brightest object in the sky after Venus sets. This year at opposition, Jupiter will be closer to Earth than at any other time from 1963 to 2022, and even though it's only about 1% to 2% larger than the preceding and following oppositions, Jupiter now appears nearly 49 arc-seconds wide. With the South Equatorial Belt still nearly invisible, the Great Red Spot is easy to identify in a small telescope.

Saturn is now completely lost in the glow of sunset, and won't be visible again until late October, when it appears in the eastern sky at early dawn.

Neptune, at magnitude 7.8, is visible in east-southeast about an hour after dark, and lies between the constellations of Capricornus and Aquarius. You can pick it out from a good dark-sky site, and a telescope will reveal it's pale, blueish-tinged disk.

Did you know about the supposedly “secret” US spaceplane? X-37B, the unmanned successor to the space shuttle, launched from Florida in April 2010 and began its first mission with very little public notice – because no one knew where it was going or what it was doing. The spaceplane was shrouded in operational secrecy. However, civilian specialists reported that it might go on mysterious errands for as long as nine months before touching down again.

  
Even though the X-37B mission was — and remains — secret, amateur astronomers first identified it after observing the object and determining it was orbiting the Earth once every 90 minutes at an inclination of 39.99 degrees. They then shared their findings with other amateurs, who have confirmed their observations and helped determine that the object was indeed the X-37B.

If the weather allows, you can catch the X-37B as it passes overhead every night this week. The X-37B does not reach anywhere near the brightness of Iridium Flares or even the International Space Station (ISS), but with magnitudes between 5.5 and 2.2, you can spot it if the conditions are right. The brightest passes occur on Saturday and Sunday evenings at magnitude 2.2 and 2.3 respectively. Look for it to pass high at altitude 85° in the south-southwest on Saturday evening at 8:35 PM CDT. Look again on Sunday evening at 7:51 PM CDT, only this time it will be at altitude 78° in the north-northeast.

For comparison, the following stars are very close to magnitude 2.2 in brightness: Denebola in Leo (Beta Leonis,) Almach in Andromeda (Gamma Andromedae,) and Mizar A in Ursa Major (Zeta Ursa Majoris.)

The ISS makes one pass overhead this week, at magnitude -0.8. Look for it to pass low in the southwest at 7:50 PM CDT on Friday, the 17th. There will also be several very bright (magnitude -8.0) Iridium Flares visible right at dusk this Thursday, Friday and Saturday. Check out the specific times and celestial coordinates for the X-37B, ISS, and Iridium Flares at the Heavens-Above web site.
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Astronomy From Your Back Yard - 9/1 to 9/7 2010

By Dave Grosvold

The Last-Quarter Moon occurs at 12:22 PM CDT on Wednesday afternoon. Fortunately, moonset occurs before dusk until early next week so we are lucky to have dark skies in the evening for observations.

On Wednesday and Thursday evenings, Venus, Spica, and Mars form a fairly straight line about 5° long, low in the west-southwest about a half hour after sunset as shown in the illustration. Despite how it appears in the image, Venus is over 175 times brighter than Spica, even though Spica is the brightest star in the constellation Virgo!

Beginning in September, the Great Square, an asterism in the constellation Pegasus has risen well up in the eastern sky after dark. The Great Square appears to be balanced on one corner, the sign of autumn to come. This year, bright Jupiter becomes a helpful landmark, shining to the lower right of the Great Square. The lower left corner star in the Great Square is Alpheratz, which is actually in the constellation Andromeda, rather than Pegasus.

From Alpheratz, follow the stars of Andromeda in a diagonal line down to the left of the Great Square, to Mirach, the second star from Alpheratz in the line. Then follow a line straight up from Mirach to the next brightest star, Mu Andromedae (μ And), and then beyond that to an even dimmer star, known as Nu Andromedae (ν And). Directly above and to the right of ν And, you will find the Great Galaxy in Andromeda, or M31. Also known as the Andromeda Galaxy, at a distance of 2,500,000 light years from Earth, M31 is one of the most distant galaxies in the night sky that can be seen from Earth with the naked eye.

If you find the right combination of a dark night, good transparency, and you've taken the time to get your eyes dark-adapted (1.5 hours or more,) you should be able to see this wonder of the heavens as a dim smudge just above ν And. A good pair of binoculars will bring the smudge out to a very prominent hazy streak across the field of view.

M31 is actually 6 times larger than the Full Moon when viewed through a large telescope, but the surface brightness is so low that you only see the center of the galaxy with the naked eye or binoculars. With a small telescope, see if you can pick out the two companion galaxies, M32 and M110. In a medium-sized telescope (8" - 12",) you should be able to see a wonderful image of the galaxy, including M32 and M110. It's almost as good as a photograph!

Like M31, M33, the Triangulum Galaxy, Is another great deep sky target, and it lies just below Mirach in Andromeda, and above and to the right of the constellation Triangulum. M33 is also visible to the naked eye in the right conditions. The Triangulum Galaxy is somewhat more distant from us than M31 at 3 million light years. That's a long way to see without any kind of optical aid!

Although both are spiral galaxies, the Triangulum galaxy presents itself to us face-on, so we can see the spiral structure much more prominently than we can with M31, which is situated at an angle to us. Along with the Milky Way and the Andromeda Galaxy, the Triangulum Galaxy is part of the Local Group of galaxies, being the third largest. The Local Group also includes about 30 smaller galaxies. The galaxies in the Local Group are gravitationally bound together, so as a whole, they move through space as one, even though the individual members are moving around within the group - sort of like a swarm of bees!
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Astronomy From Your Back Yard - 8/25 to 8/30 2010

By Dave Grosvold

With the Moon just past full this weekend, much of the deep sky will be difficult to observe, and the Moon itself is so bright that much of the detail will be lost in the glare. However, that doesn't mean we have to throw in the towel and stay indoors. There are plenty of celestial targets still available for summer observing.

Jupiter rises well below the Moon about an hour after dark. Although they look close together, Jupiter will be 1,500 times farther from us than the Moon is when they pass on the 26th and 27th. A small telescope or larger binoculars will reveal Jupiter's Galilean Moons. The positions of these moons change from night to night, so a planetarium program or online Galilean Moon Graph utility is essential for identifying these four Jovian satellites.

Uranus is only about 2° west of Jupiter. In a telescope Uranus is only 3.7 arcseconds wide, compared to Jupiter's unusually wide 48 arcminutes. Uranus can be hard to spot. Look for a greenish-white object that is slightly more disk-like than the surrounding stars.

Beginning mid-week, look low in the west-southwest during twilight. Here, Venus forms the bottom of an upside down flat, symmetrical triangle with much fainter Mars and Spica a little higher. By now, Saturn has moved far off to Venus' right or lower right. By Monday, the Venus-Spica-Mars triangle distorts significantly as Venus moves closer to Spica.

Don't forget as well that although the Moon is bright and the deep sky is washed out, The International Space Station still presents a bright target for night sky observers. On Wednesday at 8:30 PM CDT, the ISS should pass high overhead in the SE at an altitude of 50°, shining brightly at magnitude -3.4. The ISS makes several more passes this week, though none is as bright as this one.

On Thursday, look for the ISS at 8:57 PM CDT, as it passes a little less than halfway up the sky (34°) in the NW, reaching magnitude -1.9. On Saturday evening, look for it at 8:17 PM CDT, this time just a bit lower in the NW at altitude 29°. The ISS will shine a bit less brightly at magnitude -1.5. The ISS passes overhead just about every night this week, but these are the brightest.

Also this week, Iridium 3 flares to magnitude -2 in the early morning hours on Friday at 5:21 AM CDT. Look for the Iridium 3 flare at an altitude of 52° in the SW. Iridium 76 flares to a stunning magnitude -8 early on Saturday morning at 5:15 AM CDT, also at 52° altitude in the SW. Sunday evening, Iridium 7 will flare to magnitude -1 at 9:37 PM CDT. Look for it low on the northern horizon at an altitude of 12°. Check the charts at Heavens Above to find out when and which direction to look to catch the both the ISS and Iridium Flares.
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Astronomy From Your Back Yard - 7/21 to 7/28 2010

By Dave Grosvold

This week, the planets Mercury, Venus, Mars, and Saturn continue to mark a nice straight line along the ecliptic, with Mercury in the lead as they sink into the western horizon. Mercury will set very soon after dusk, so you will have to watch carefully as the sun sets to catch it.

On Friday evening, Saturn's largest moon, Titan, is below and to the right of the Ringed Planet this evening. A small telescope will show it at magnitude 9. In the image at left, Titan is above and to the left of Saturn, which is the orientation that matches the mirror-reverse image found in a refracting telescope. Titan orbits Saturn every 16 days, so you can watch it swing from one side of Saturn to the other over a bit more than a two week period. Saturn's Rings, have widened a bit in the last several weeks to 3° from edge-on, even as the planet recedes from Earth.

Jupiter is at magnitude –2.6, in the constellation Pisces this week, and it rises around 12 AM CDT. Jupiter shines as the bright “Morning Star”, high in the southeast in the early morning hours before dawn. Jupiter's smaller, more distant cousin, Uranus is within 3° of the King of Planets at magnitude 5.8. In a telescope, Uranus is a tiny 3.6 arcseconds wide, compared to Jupiter's 44 arcminutes. Uranus will be hard to spot with the Moon reaching its Full phase by 8:37 PM CDT Sunday evening, July 25th.

The latter part of this week, Thursday and Friday evenings are a good time to look at some of the Moon's more prominent features. Most visible in small telescopes are the lunar maria (MAR-ee-ah,) or seas. These are darker areas, or plains on the surface of the Moon that stand out from the surrounding terrain because of their apparent smoothness and lack of albedo, or reflectivity. These maria are actually areas where basaltic lava has been laid on the lunar surface by volcanic activity.

Other prominent features include craters and mountain ranges. Copernicus and Tycho are very prominent craters since they both have relatively high albedos and are surrounded by ray systems, which are the remnants of ejected lunar material due to impacts. Other prominent craters include Ptolemaeus, Plato, Hercules, Atlas, and Endymion. Prominent mountain ranges include Montes Apenninus, Montes Caucasus, Montes Carpatus, and Montes Riphaeus. These mountain ranges are the rough edges that remain from huge, ancient impact craters.

The study of the surface and physical features of the Moon is known as Selenography, which is concerned not with geology so much as lunar mapping and the naming of lunar features. Although there had been earlier attempts to draw maps of lunar features. including a map by Michel Florent van Langren in 1645, the first real lunar atlas was produced by Johannes Hevelius in 1647 and titled Selenographia. Van Langren's map and the name of lunar features had distinctly Catholic origins, where Hevelius' work corresponded to features on Earth and on the Greek and Roman civilizations. If you're interested in Selenography, you should check out Virtual Moon Atlas, which is a great free software download you can use to learn about lunar features.
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Astronomy From Your Back Yard - 7/14 to 7/20 2010

By Dave Grosvold

Wednesday evening will be a good time to look for a thin crescent Moon below Venus in the fading western sky. At 9:00 PM CDT, the waxing crescent Moon will be about 7° to the lower left of brilliant Venus. Also on Wednesday evening, look for the International Space Station (ISS) to make a fairly bright overhead pass starting at 9:31 PM CDT. Look for it low in the NW, and then watch it swing up to an altitude of 57° in the SW before fading into the horizon in the SSE.

On Thursday evening, July 15th, the Moon is farther left of Venus. Now they both appear to be close to the same altitude above your horizon. Also on Thursday, Saturn's largest satellite, Titan, is at its eastern elongation from the planet this evening, and should be easy to pick out in a small telescope at high power. By Friday evening, the Moon has moved far to the left of Mars and Saturn.

Iridium 25 makes a bright pass overhead on Saturday evening at 9:41 PM CDT. Look for it to flare to magnitude -6 at an altitude of only 14° above the horizon in the NNW. There are several more Iridium Flares occurring this week, all in the early morning hours. You can find out the times and directions of Iridium Flares and ISS passes at Heavens Above.

Look for the bright stars Vega, Deneb, and Altair, the apices of the Summer Triangle in the eastern sky soon after dusk. This week, the Summer Triangle asterism will slightly higher in the sky than it was at the same hour last week. There are several Messier objects to be found within the Summer Triangle. These are wonderful jewels that can be captured by a pair of binoculars or a small-to-medium (6” - 10”) telescope.

If you want to learn more about these jewels of the night sky, check out this Astronomy From Your Backyard PDF file. If you want to actually see these objects in a telescope, come to the AOAS Star Party this Saturday, July 17th at Lake Fort Smith State Park, weather permitting. We will be holding a presentation in the Visitor Center at 8:00 PM, CDT, and then we'll move to the boat ramp area where we will have club members and their telescopes set up for public viewing. Come on out and enjoy the night sky!
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Astronomy From Your Back Yard - 7/7 to 7/13 2010

By Dave Grosvold

This week, look for Venus shining bright in the western sky at dusk. Venus moves lower in the sky every week as the year marches on. In the evening on Saturday, July 10th, look for Regulus straight below Venus. Regulus is 150 times dimmer than Venus, and is very close to it — only about 1.2°.

On Sunday, July 11th, the New Moon occurs exactly at 2:40 PM. CDT. Mercury and the thin crescent Moon are far to the lower right of Venus in early evening Sunday, and visible only at locations with a clear view to the west. Catching them together will require some searching and the aid of a pair of binoculars. Sunday evening, Mercury and the Moon will be about 10° apart at dusk.

After Sunday, the waxing crescent Moon moves along a diagonal line south of the one described by Mercury, Venus, Mars, and Saturn. The planets lie on, or very close to the ecliptic, which is the plane of the Solar System. Watch each evening, and you will see the Moon higher and farther south than the night before, while the Crescent grows fatter until it reaches First Quarter at the end of next week.

With the darker skies due to the New Moon, this week is also a great time to look for objects in the deep sky. Deep sky objects are objects in the night sky other than individual stars and the planets of our own Solar System. The deep sky is rich with star clusters, various type of nebulae, galaxies, and supernovae remnants. In mid-summer, Scorpius is high in the south after dusk, and the Scorpion's Tail is only visible for a short window of time during this part of the year.

Scorpius is one of the most recognizable constellations in the sky, since it so closely resembles its namesake. The Scorpion's Tail is an area rich in deep sky objects, and is a great place to spend some time browsing with a telescope or binoculars. Look for Messier objects M7, the Ptolemy Cluster, and M6, the Butterfly Cluster, in the area above and to the east of the tip of the Scorpions Tail. A bit higher, in the body of the Scorpion, lies M4, a brilliant globular cluster, and one of the jewels of the night sky.

There are also many objects from the NGC, or New General Catalogue visible in the Scorpion's Tail as well. Open clusters NGC 6383, NGC 6425, NGC 6416, NGC 6242, NGC 6281, NGC 6231, NGC 6322, and NGC 6250 are in the Tail, as well as globular clusters NGC 6441, NGC 6338, and NGC 6541. Click this link for a finder chart.

This time of year, the Summer Triangle is prominent in the eastern sky about an hour after dusk. This asterism is made up of three bright stars from separate constellations: Vega, in the constellation Lyra is at the top of the triangle. Deneb, in Cyngus, is farther down on to the left (astronomers say it is North of Vega.) And finally, Altair, in the constellation Aquila, is even farther down from Vega to the right (or South for astronomers.)
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Astronomy From Your Back Yard - 6/30 to 7/6 2010

By Dave Grosvold

You can spot 1 Ceres any night this week as it moves through the constellation Ophiuchus (pronounced Oh-FEE-eh-kuss) with binoculars or a small scope. Ceres, the largest astronomical body in the asteroid belt, was discovered on Jan 1, 1801 by Giuseppe_Piazzi. After having been designated as a planet in 1801, Ceres enjoyed that elevated status for only a short time, until a number of other small objects were discovered in the space between Jupiter and Mars. In 1802, William Herschel coined the term asteroid ("star-like") to refer to these small bodies — bodies that were too much like stars to be planets, but wandered in the same way.

Ceres was reclassified as a dwarf planet after the status of Pluto was debated and demoted in 2006. Ceres is now the smallest dwarf planet in the Solar System, rather than the largest asteroid, but remains designated formally as 1 Ceres since it was the first such body to be discovered. 1 Ceres is currently still as bright as magnitude 7.3, and can be located by using the finder chart. The best way to distinguish Ceres from the background stars is to observe it on several different nights. The obvious movement from night to night compared to the background will give it away.

Some very bright Iridium Flares may be visible this week! On Wednesday evening, June 30th, Iridium 26 will flare to a magnitude of -3.0 in the WSW at 11:36 PM CDT. Look for it at an altitude of 19° above the horizon. Any time we refer to magnitude in this article, we are actually referring to apparent magnitude, which is how the brightness of an object appears to observers on Earth, as opposed to its intrinsic brightness, or absolute magnitude.

In the early morning hours of Thursday, July 1st, you may be able to catch Iridium 12 flaring to a very bright magnitude -7.0 at 4:16 AM CDT, 27° above the horizon in the ESE. Iridium 23 also flares to a brilliant -7.0 magnitude on Thursday evening at 11:30 PM CDT. Look for it at an altitude of 19° in the WSW. A magnitude of -7.0 is several orders of magnitude brighter than Venus at its brightest! Venus only reaches -4.67 when it is in it s crescent phase and closest to Earth. So these flares will be very bright.

Another pair of bright Iridium Flares appropriately occur on Independence Day, Sunday, July 4th. At 4:04 AM CDT in the ESE, look for Iridium 91 at 23° above the horizon, flaring to a -4.0 magnitude. Again at 11:21 PM in the WSW, Iridium 22 hits magnitude -6.0 at altitude 18°.

Finally, look for Iridium 56 and Iridium 41 in the early morning on Tuesday, July 6th flaring to -5.0 and -7.0 in the SE at 28° and the E at 12° respectively. Iridium 56 will flare at 3:54 AM CDT and Iridium 41 at 5:14 AM, CDT.

The International Space Station (ISS) makes only one pass low in the NNW this week, starting at 11;56 PM CDT on Monday, July 5th. The ISS starts at altitude 10° in the NNW, then barely swings up to a maximum altitude of 11° in the NNW, and quickly fades from view. The ISS will only reach a maximum brightness of magnitude 0.0, or just slightly brighter than Vega in the constellation Lyra at magnitude 0.03.

Venus closes in on Regulus in the constellation Leo day by day, while Mars closes in on Saturn. The diagonal line of Saturn, Mars, Regulus, and Venus is shrinking every day. The three planets will be very close together low in the west at sunset by early August. A telescope shows Saturn's Rings a mere 2° from edge-on right now, but the rings will continue to increase their tilt with respect to Earth over the next 15 years.

The waning gibbous Moon rises around midnight on Friday, July 2nd, and about 45 minutes later, Jupiter rises beneath it. Jupiter is slowly working its way back into the evening sky, and should be a bright Evening Star by mid-autumn, while Venus sinks into the glare of the autumn sunset

As night falls this time of year, look for red Arcturus high in the southwest straight above Spica in the constellation Virgo. The kite shape of the rest of the constellation Boötes extends straight up from Arcturus. By the way, Boötes is pronounced "Bo-OH-teez" or "Bo-OH-tiss," not "BEWT-eez", as some might assume. Pronunciation of constellation names is open to debate, but there are several accepted pronunciations for most constellations. If you're interested, See the Sky & Telescope magazine web site for a Pronunciation Guide.
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Astronomy From Your Back Yard - 6/23 to 6/29 2010

By Dave Grosvold

The waxing gibbous Moon lies in the head of the constellation Scorpius after dusk on Wednesday evening. Reddish-orange Antares is still bright, riding below and to the Moon's lower left. On Thursday evening, Antares and the upper part of Scorpius lie to the right of the nearly full Moon after dusk.

June's Full Moon occurs on Saturday morning at 6:31 AM which will be after daylight begins. The first Full Moon of June is known as the Strawberry Moon, so named by the Algonquin tribe because the relatively short season for harvesting strawberries comes each year during the month of June It is also known as the Flower Moon or Planting Moon.

Observers in most of North America will also be able to witness a partial Lunar Eclipse on Saturday morning when the Moon will be setting in Sagittarius as the Sun rises. For observers in our neck of the woods, the Moon will be entering the penumbra at around 4:30 AM, and then will enter the actual eclipse phase by 5:17 AM. For observers in Arkansas, the Moon will be below the horizon before it reaches the maximum point of the eclipse. The image at left shows the Moon just starting to enter the umbra as it begins to set at 5:20 AM CDT.

Venus is in the constellation Cancer at magnitude -4.0 and is still the bright Evening Star, shining in the west-northwest during and just after twilight this week. While Venus sinks in the west, Mars shines at magnitude +1.3 to Venus' upper left, a match in brightness for Regulus in Leo. The contrast in color between reddish Mars and blue-white Regulus is obvious to observers at darker-sky viewing sites. Regulus is falling farther to Mars' lower right each evening. The star to the upper right of Mars and Regulus is Gamma Leonis, which is only a little dimmer than these two.

Jupiter is now rising around 1:00 AM CDT this week along with the constellation Pisces, and shines high in the southeast before dawn. Nothing else in the sky at that time of night is as bright as Jupiter at magnitude -2.28. Jupiter's Great Red Spot is still free of the missing South Equatorial Belt for telescopic observers.

Saturn glows in the south west during evening, to the upper left of Mars. The diagonal line of Saturn, Mars, Regulus, and Venus, is shrinking; the three planets will bunch up low in the sunset in early August. This week right after dusk, you can catch Saturn, Mars, Regulus, Venus, Praesepe (the Beehive Cluster,) and Pollux in a single diagonal line drawn down the western sky.

Saturn's Rings are tilted 2° from edge-on in a telescope. Note the thin black shadow-line that the rings cast on Saturn's globe. The tilt of the rings will steadily increase over the next 15 years so that we can see more and more of the rings. As they tilt farther, observers with small telescopes will be able to see the Cassini Division, a thin dark band in the rings first observed by Giovanni Cassini in 1875.

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