July 2008
Skywatchers’ Guide for July 2008
PLANETS
HIGHLIGHTS: Mars creeps closer in our sky to Saturn and away from the bright star Regulus in the evening sky this month, with a spectacular grouping of these same four objects on July 5 and 6. By July 9-11 Mars is within 0.6 degrees from Saturn in our sky! In addition bright Jupiter is at opposition (opposite from the Sun in our sky) on July 9 and visible all night long (see below).
Mars is visible starting 30 minutes after sunset this month and starts the month paired with the bright star Regulus, in Leo, the Lion, above the western horizon in evening twilight. The Red Planet is a tiny 4.3 arc seconds in apparent size (near its smallest apparent size possible) and not very bright (at magnitude 1.8). Mars drifts 0.5 degrees per day in July towards Saturn, moving through Leo, the Lion. A wonderful grouping occurs when the 4 day old waxing crescent Moon is nearest but below Mars and Saturn in our sky on Saturday evening July 5 and northeast or ‘left’ of Saturn and Mars on Sunday evening July 6. By July 8 Mars will lie one degree from Saturn; The two are closest at about 0.4 degrees apart on July 9 and 10. The Mars Phoenix Mission, led by the University of Arizona, has landed on the north pole of Mars: For information on and images from this first University led mission to another planet see the Phoenix Mars Mission Home page
Saturn is paired with much dimmer Mars from July 7-13, with the two only 0.4 degres apart on July 9/10 as seen from the Desert Southwest. Saturn is a 0.9 magnitude star-like object in July and is sinking in the western evening sky, so sharp views of its ring system may be difficult, especially late in the month. The ringed planet is dimmer this year (compared to previous years) because its rings are more edge-on, and will be seen more edge-on as the year progresses. Early in July Saturn is found well above the western horizon in the constellation of Leo the Lion at 8:30 p.m. However, as Saturn moves lower in our sky it sinks to only 5 degrees above the western horizon by the end of the month, one hour after sunset. Saturn continues eastward or ‘direct’ motion, drifting farther (from four to over seven degrees) from Leo’s brightest star Regulus this month. Saturn sets early by around 2 hours after sunset by July 1 but only about an hour after sunset by the end of the month. Saturn sinks out of sight and into the glare of the Sun by August. As stated earlier, look for the wonderful grouping of a 4 day old waxing crescent Moon below Saturn, Mars and Regulus in our sky on Saturday evening July 5, and the 5 day old Moon northeast or ‘left’ of Saturn and Mars on Sunday evening July 6.
Bright Jupiter rises just after 8:00 p.m at the start of July but rises at sunset on Tuesday, July 8 when it is at opposition. At opposition a planet rises at sunset and is visible all night long. Opposition for Jupiter is also near to when it is closest to Earth in space, but due to Jupiter’s large apparent size good telescopic views of Jupiter can be obtained for months on end. In early July Jupiter is highest (transiting the southern horizon) by 1:00 a.m. Whitish Jupiter is east of the Teapot of Sagittarius and is the brightest star like object well up in the late night sky. The nearly full, waxing gibbous Moon slides well below Jupiter in our sky on Wednesday evening July 16. The full Moon on July 17 is also not far from Jupiter in our sky.
The Brilliant planet Venus has sunk out of sight into the glare of the Sun and will not be easily visible to the unaided eye until August. Venus might be glimpsed to the naked eye starting 20-30 minutes after sunset, just a few degrees above the west-northwestern horizon, during the last few days of July.
Mercury fades into view after June 25 in the morning sky. Mercury is easily visible above a clear east-northeastern horizon in early July, starting 50 minutes before sunrise. Mercury is more easily visible after July 3, as it brightens to a zero magnitude object. By July 4 the elusive world is visible 5 degrees above the east-northeastern horizon at 4:30 a.m. when at 0.3 in brightness. Observers in most of the continental United States (including mid-northern latitudes) can see bright Mercury. Mercury continues to brighten gradually in early July, is a magnitude brighter by July 11 and is most easily seen in the morning sky from July 6-11. Mercury is lost in the glare of the Sun by around July 19. The first spacecraft to orbit Mercury, the MESSENGER spacecraft, arrived early this year in its first flyby of Mercury. For a link to see the latest images, and find details about the MESSENGER spacecraft and the Mission Operations Center, click here.
Visitors to Flandrau’s 16-inch telescope should note that Mars and Saturn are only visible in the telescope during public hours before 8:30 p.m. early in the month. Jupiter becomes visible in the latter half of July after 9 p.m. Flandrau Science Center and its observatory will be closed on July 4, for the Independence Day holiday. Flandrau’s 16-inch telescope is open for viewing during public hours, weather permitting, Wednesday through Saturday nights (excluding select holidays), from 7-10 p.m. Finally, remember that in spotting planets there is a general rule: ’stars twinkle, planets don’t’. This is because stars are point sources of light; therefore starlight is easily disturbed and shifted by air currents in the Earth’s atmosphere. However when looking at Mercury or even Mars this month, note that they July appear to twinkle somewhat; however, this twinkling is of a slower nature than that of the bright stars.
JULY EVENING STARS
The Big Dipper is easy to find in July, high in the northern half of the evening sky. Look for the Big Dipper high in the north 1 hour after sunset. Take the two end stars off of the bowl (the ‘pointer stars’) and point down to Polaris, the North Star. Polaris is a star of ordinary brightness, and marks the end of the handle of the Little Dipper. Polaris can also be found about 30 degrees (or 3 fists) above the northern horizon. Polaris stays put in the sky; to the eye it doesn’t appear to move. This is because Earth’s axis is pointed toward Polaris in space.
Bright stars of the July evening sky (1 hour after sunset) include ruddy Antares in the south, the bright yellow star Arcturus high overhead, and the blue star Spica, high in the southwest. Locate the bright yellow star Arcturus and the blue star Spica by recalling, “Follow the arc (of Big Dipper’s handle) to Arcturus and drive a spike to Spica”, or simply “Arc to Arcturus and spike to Spica”. Although Spica is said to mark the spike or ear of wheat in the hand of Virgo, it really looks like the bottom of a group of stars in Virgo that make up a diamond or kite shape.
High above the northeastern horizon in early July one hour after sunset is bright Vega, the brightest star of the summer sky. Blue-white Vega high in the northeastern sky contrasts sharply with Antares, the baleful red super-giant star of summer, now above the southern horizon in early July evenings. Throughout July the orange-red twinkling of Antares enlivens the southern sky, giving reason to its name “the rival of Mars”. From the southern United States Antares does not get very high, only about 30 degrees (or three fists held at arm’s length) above the southern horizon (due to its location in the southern sky). From Australia though Antares can be seen overhead in June and July. Antares is the brightest part of a most impressive scroll of stars, sort of like a long letter S fallen halfway forward. In this case the S stands for the constellation it is part of: Scorpius.
The Milky Way Prominent in the Late Night Hours!
Look for the Milky Way to rise late on moon-less July evenings. It will be brightest around the constellation Scorpius, the Scorpion in the south. The Milky Way, the galaxy of stars, gas and dust our solar system resides in, is prominent all summer long, and is brightest after 10 p.m. in early July, but by late July can be seen well at the end of evening twilight. To see it, you’ll need to get away from city lights to a dark location, and look on a night when there’s not much interference from the moon. The Milky Way will appear as a “cloudy” band stretching clear across the sky. High power binoculars and telescopes reveal the Milky Way to be clouds of stars, millions of them, with attendant star clusters and gas clouds making up some of the “fuzzier” spots you’ll see.
MOON PHASES
The new moon in July occurs on Wednesday July 2. The July first quarter Moon will occur on Wednesday evening, July 9. The July Full (Buck/Thunder) Moon rises not far from Jupiter on the evening of Thursday, July 17 and sets on the morning of Friday, July 18. This full moon is the second lowest in the sky this year, and should appear deceptively large to many people. The July 2008 last quarter Moon will occur on Friday morning July 25. These dates and times are for southern Arizona, and are not necessarily Greenwich Mean Time dates, the moon phase dates used for calendars.
Note: Additional information can be accessed by phone at Flandrau Science Center’s Astronomy Newsline at (520) 621-4310 or as a menu option at 621-S-T-A-R.
Graphics done using Starry Night Enthusiast and Adobe Photoshop. To purchase Starry Night Enthusiast go to http://StarryNight.com
Graphics done using Starry Night Pro, Starry Night Enthusiast and Adobe Photoshop. To purchase Starry Night Pro or Enthusiast, go to http://StarryNight.com