WHAT S UP? JULY 2013 The monsoon season begins in earnest in July (we hope!), which could definitely affect evening viewing, at least shortly after sunset, until the storm clouds die down. Constellations (starting towards the east and moving west): Cygnus is becoming more prominent, but will be directly overhead next month; Sagittarius is low in the southeast with the smoke of the Milky way pouring out of its Teapot asterism; Hercules will be directly overhead; Scorpius takes center stage to the south; the Big Dipper, overhead last month, is rotating around to the northwest; Leo will be placed just above Venus mid-month, but will be setting at sunset by month s end. The Milky Way now spans across the sky from the south to the northeast. The Night Sky for Mid-Month at 10PM (Credit: Cartes du Ceil)
Here is the planetary roundup for July: Mercury moves into the morning sky this month. At month s end, it will be at its furthest position from the Sun and located for good viewing (by you early risers). Mercury, Jupiter and Mars will be very close together towards the end of the month. Venus continues to slowly rise higher in the west as it swings around the Sun towards Earth. It will brighten slightly, even though its surface will become less illuminated. Yes, it has phases (crescent, half full, gibbous, full), just like the moon. Mercury does as well. Mars is finally coming out of the morning glare and will pass by Jupiter in the latter half of the month. It still should be a dim object, however. Look to the east northeast to see it. Jupiter also climbs higher away from the Sun s glare during the month. It will be brighter than Mars, but will be visible for only a short time after rising. Saturn is well placed in the western sky after sunset and will remain visible for quite a few hours. At the beginning of the month, it will set just after 02:00, but will be setting at midnight by month s end. Aster-what? An asterism, just like a constellation, is a group of stars that resembles an object. In the case of the Teapot, it is a sub-set of the constellation Sagittarius. The Milky Way really does resemble smoke coming out of the Teapot s spout. There will be much more about asterisms next month. Events for July: Date Friday, the 5 th Monday, the 8 th Wednesday, the 10 th Tuesday, the 16 th Sunday, the 21 st Monday, the 22 nd Tuesday, the 23 rd Sunday, the 28 th Tuesday, the 30 th Description Earth at aphelion (furthest from the Sun) New Moon Venus 7 north of the Moon Saturn 3 north of the Moon Moon at perigee (will appear very large) Full Moon Mars 0.8 north of Jupiter (morning sky) Southern Delta Aquarid Meteors peak Mercury at greatest elongation (furthest [visually] from the Sun)
Furthest from the Sun??? Yep. In the hottest month of the year (for the northern hemisphere, anyway), we are further from the Sun than we are at any other time of the year. When are we the closest? In January. How can that be? That s just how our orbit around the Sun works out. It is slightly elliptical (oval) and so we move slightly closer or further away from the Sun as we swing around it each year. It turns out our temperature is more affected by how much atmosphere the Sun s rays encounter than our distance from the Sun itself. In winter, the Sun is closer to the horizon, so the Sun s rays pass through more of the Earth s atmosphere and less energy reaches the ground. In summer, just the opposite occurs. Make no mistake; the distance plays a factor as well (Icarus, whose wings were made of wax, found out the hard way). For the southern hemisphere, the closer proximity and higher altitude of the sun pretty much coincide and it makes for hotter summers. Just ask the people who live in the Australian Outback Moon-Venus Pairing On the evening of the 10 th, the Moon will pass close to Venus. It will be below and to the left of Venus, about 7 degrees away. The Moon will be a small crescent that evening, since the New Moon will have been just two days before. Also, look for the head of Leo just above the pair. A two-day-old Moon will be near Venus on the 10 th. Look to the west northwest to see it. (Credit: Sky Safari Pro).
Delta Aquarid Meteor Shower(s) At the end of the month there will be a meteor shower that radiates from the constellation Aquarius. However, there are two different radiant points. Meteors may be visible from the southern radiant from roughly 14 July to 18 August with the peak around the 28 th of July. The meteors from the northern radiant occur a little later, starting around 16 July and going until around 10 September, with the peak around the 13 th of August. I ll mention this one again next month. Look for the meteors after midnight. As can be seen in the diagram below, the radiant points will be towards the south, so the meteors will appear to fan out towards the north, east and west. Locations of the Delta Aquarid meteor showers. Look for the southern shower to peak around July 28 th. (Credit: Sky Safari Pro)
Focus On Scorpius Look due south in July to see Scorpius (Credit: Sky Safari Pro) If you look to the south, you will see Scorpius, one of the two constellations (Sagittarius is the other read about it next month) that sit near the heart of the Milky Way. Three stars at the top (highest above the horizon) form the head and a series of stars form a long arc that represent the tail. According to Mythology, Orion (the Hunter) once boasted that he could kill any animal on Earth. Gaia, the Goddess of Earth, was offended and cracked open the Earth and released a giant scorpion, which killed Orion. Zeus decided to put both Orion and the scorpion in the heavens, but placed them on opposite sides of the sky. This was to signify that Orion was running away from the scorpion, so Orion is seen ducking below the horizon just as Scorpius rises. The most notable star in Scorpius is Antares ( Rival of Mars ), a bright red star near the constellation s head. Antares is a red supergiant that is a 400 times as wide and 10,000 times as bright as the Sun. Antares and Betelgeuse (in the constellation Orion) are the two reddest stars in the sky. Antares appears so red for two reasons: first, because of the color of the star itself, but it is surrounded by a large cloud of gas which also glows red. The gas is caused to glow by the star s intense radiation. Note that the two bloodiest stars in the sky are in Orion and Scorpius the two characters that fought each other. Coincidence? You be the judge Shaula, at the very end of the tail, is the 2 nd brightest star in the constellation. In fact, the name means stinger in Arabic. Shaula is actually a triple star system and the three blue-white stars can be resolved with a small telescope.
When looking at Scorpius, you are looking towards the center of the Milky Way and there are quite a few interesting objects in that direction. One of them is M4, a globular cluster and the 4 th object in Charles Messier s list of non-comets. M4 can be easily seen with binoculars; it is one of the closest globular clusters to Earth at a distance of 7200 light years. M4 Binocular View M4 105mm Telescope View M4 Hubble Telescope View (Credit: NASA) There are also some notable open clusters near Scorpius. One of them is M6, also known as the Butterfly Cluster because of its shape. M6 is a naked-eye object (for those with good eyes observing under dark skies) that contains about 80 stars spread over an area about 12 light years across. Visually, M6 appears almost a big in diameter as the Moon. M6 Binocular View M6 105mm Telescope View Another naked-eye open cluster is M7 ( Ptolemy s Cluster ) which also contains about 80 stars. It is closer to us than M6 and appears almost twice the diameter of the Moon. The cluster is approaching us at a little less than 9 miles per second but not to worry at that rate, they won t get here until 17,002,013 AD.
M7 Binocular View M7 254mm Telescope View (Credit: Rolf Wahl Olsen) Open What? An open cluster is a group of stars that are weakly bound together by gravity. Open clusters can contain anywhere from a few dozen to a few thousand stars. They form from the same cloud of gas and, thus, are all approximately the same age. Since the pull of gravity is fairly weak, the cluster is easily disturbed by any passing object (gas cloud, star, etc.) and so the cluster won t maintain its integrity for more than a few hundred million years. Globular clusters, because they contain millions of stars, have a much stronger gravitational pull and maintain their structure for billions and billions of years.