Updated for the month of: July, 1996
Red Supergiant Sparkles in Summer SkyAntares is the brightest star in the constellation Scorpius - "the Scorpion". Scorpius clearly resembles the creature after which it was named ( or a fish hook), with the curving path of stars that form the Scorpion's tail dipping down and left to the southern horizon, then curving back up. In July, Scorpius can be found due south around 10:30 pm, daylight savings time.Antares, which is the fairly bright reddish star toward the upper part of Scorpius, belongs to a rare class of stars called "red supergiants". It is a monster compared to our own sun, with a diameter 300 times as large. (Don't confuse it with the brighter, bluer, and closer planet Jupiter, which is east of Scorpius in Sagittarius and is not due south until around midnight in July, 1996). Antares is a distant star, 330 light years away from Earth (Jupiter is currently only about 35 light minutes away). The light photons from Antares that hit your eye in July, left the star 330 years ago.
From dark locations Antares is a beautiful, reddish sparkling sight with the naked eye. With a pair of binoculars you can clearly see its unusual salmon color. Antares is part of a double star system (see Star Facts article for July, 1995, "Star Twins", for more about double stars), but its companion star is so close to it and so much dimmer that it takes a powerful telescope to see it.
"The Teapot" - A Look Into the Probably the best recognized and prettiest of the summer constellations is Sagittarius, better known as "the Teapot". From mid-northern latitudes in July, it is found low in the southern sky around midnight. It clearly resembles an old teapot, tilted down toward the right, with its spout on the right side, its handle on the left side and a triangular top.When we look at Sagittarius we are actually looking in the direction of the center of the Milky Way, the nucleus of our galaxy. This is the densest concentration of stars, gas and dust in the sky - it is an astronomical garden of rich star fields, beautiful nebulae, and sparkling star clusters. With binoculars or a low power eyepiece on a telescope, scan the areas above and on either side of the top of the Teapot, and the area between the Teapot and its neighbor toward the west, Scorpius. The glowing cloud-like areas are nebulae , places where new stars are being born from the gravitational collapse of interstellar dust and gas. The areas with tightly packed groupings of stars, known as open star clusters, are litters of young stars still "huddled" around one another before going off on their individual journeys through the galaxy. The dim fuzzy balls of light are ancient and distant groupings of thousands of stars, called globular star clusters, that date back to the beginnings of our galaxy, and travel in a ball-like shape in and out of the main disk of the Milky Way.
Jupiter at its Brightest & Closest Point
On July 4, 1996, the largest planet in our solar system, Jupiter, will come to opposition - the point in its orbit at which the Sun, the Earth, and Jupiter are in a straight line, and Earth and Jupiter are closest to each other. Jupiter remains a good sight all summer and into early fall. It is currently found in the constellation Sagittarius. In July, 1996, it rises in the southeast around 9:00 pm, Daylight Savings Time, travels a somewhat low path across the southern sky, and reaches its highest point, about 30 degrees above the horizon, due south around midnight. Other than the Moon and Venus (Venus doesn't rise until shortly before sunrise in July), Jupiter is the brightest object in the night sky - you can't miss it.Take a look through even a small telescope and you get a better treat. Like a string of pearls, the four largest moons of Jupiter appear in a diagonal line that crosses the giant planet. Their names are Io, Europa, Ganymede, and Callisto in order of increasing distance from Jupiter. Not all of these moons are always visible. At various times only three or even two can be seen, as the moons circle behind or in front of the planet, even eclipsing each other at times. Their positions change visibly from night to night, or even during a several hour period on the same night. Look closely at the planet itself with a telescope and, under good conditions, you can see one or two of the dark bands that go around Jupiter like a belt.
Jupiter is a giant gas planet. About one hundred Earths would fit inside of it. Jupiter is so big, it was almost a small sun. If it had been big enough to be a sun ( that is, if it had enough mass to support thermo-nuclear fusion), our solar system would have two suns . We would sometimes see them both in the sky at the same time. At other times they would alternate so that as one was setting the other would rise, resulting in no night. (See Star Facts article for January, 1996, "How and Where Stars are Born" for more details about what causes a sun to turn on.)
As you look at Jupiter and it's four largest moons with a telescope, imagine Galileo's amazement about 300 years ago when he used the first astronomical telescope to look at Jupiter, and became the first human being to see the moons of another planet. You can repeat that same amazement for yourself tonite! (See Calvin Hamilton's "Views From the Solar System" for more information about and pictures of Jupiter and its moons).
A Bright, Crescent Venus Right Before Sunrise!Shortly before sunrise in July, 1996, as the sky begins to lighten, the extremely bright object in the eastern sky is the planet Venus. Because Venus, our next door neighbor in space, is closer to the Sun than Earth is, we see it going through phases that are similar to the Moon's phases. When it is on the opposite side of the Sun from Earth we see it far away but full-face, a "full Venus". When there is a 90 degree angle between Earth, Sun, and Venus, we see a brighter "half Venus" as only the half that faces the Sun is lit up from our angle.When the angle between Earth, Sun and Venus is less than 90 degrees, as is the case in July 1996, we see an even brighter "crescent Venus".Look now with a telescope and you will see an amazing sight - a thin crescent Venus!
M13 - The Fuzzy Mothball Crowded With Suns
High in the sky, and directly overhead at about 10:00 pm in July, is the finest globular star cluster visible from mid northern latitudes. It is called M13, and it is in the constellation Hercules. It travels toward the western horizon as the night goes on, setting around 5:00 am.Globular star clusters are ancient groupings of stars believed to have formed early in the history of our galaxy. They contain some of the oldest stars known, ten to twelve billion years old. That is more than twice the age of our Sun. They are made up of hundreds of thousands of stars packed together much more closely than stars normally are, into a sperical shape. Interestingly, though globular star clusters are considered part of our galaxy, most of them lie outside the plane of the main disk of stars that form the Milky Way. They lie mostly above or below the central core of the galaxy, forming a halo-like pattern around the galactic nucleus.
M13 appears with the naked eye or binoculars as a soft glowing ball of light, a fuzzy mothball. It takes a reflector telescope with an 8 to 10 inch mirror to begin resolving some of the individual stars around the edge of the cluster. Most estimates of the number of stars in M13 put it at between 300,000 and one million stars! (See time exposure amateur photos of M13 on the website of the Students for the Exploration and Development of Space.)
To find M13 between the period of about 10:00 pm to midnight in July, face south and look directly overhead, or a bit west of overhead. Locate a dim keystone pattern formed by four stars. This is a square-like shape (positioned a bit diagonally as you face south), with the top two stars being a little wider apart than the bottom two stars. Unless it is a very dark location, it takes a while to identify this keystone shape because the four stars that form it are relativley dim. The "keystone" is the center of the constellation Hercules. M13 is about 1/3 of the way down on the imaginary line connecting the top right star to the bottom right star of the keystone.
M6 & M7: Two Prominent Star ClustersTwo of the brightest "open" star clusters known are visible in July after about 10:00 pm. Both are in the constellation Scorpius. They are known as M6 and M7. Both can be seen with a pair of binoculars or a small telescope. On very dark, clear nights, M7 can actually be seen with the naked eye. (See photo of M6 and photo of M7 from the University of Arizona SEDS web site).To find these star clusters, follow the curving tail of Scorpius in the southern sky down toward the horizon, hooking left and back up a little to the two side-by-side stars at the top of the tail. From these two stars, scan a short distance to the left to see M7. From M7 scan a short distance up and to the right to see M6.
Open star clusters are groups of "young" stars within our galaxy, the Milky Way, that were created around the same time and are still relatively close to each other as they travel through space. The stars in M7 are about 260 million years old (our sun is about 4 billion years old) and are 800 light years away. M6 is 1,300 light years away.
Night Owls Get a Preview of Next Season's Stars
Do you want to get a preview of the prime time stars of the next season? If you want to see what the evening sky will look like three months from now, look now, but look six hours later! Look at the sky at 3:00 a.m. and you will get a preview of what will be visible in three months at 9:00 p.m. See Star Facts article for June, 1996, "See a Preview of Next Season's Prime Time Stars Now!" for explanation of this phenomenon.
A Red Giant, 25 Times Bigger Than Our Sun!
The star Arcturus, in the constellation Bootes, appears high in the western sky as dusk turns into darkness during July. It continues westward during the night, setting around 1:00 am. The easiest way to find it is to follow the curve of the handle of the Big Dipper, backward from the bowl, and "arc to Arcturus".Arcturus is a red giant, a cooling sun nearing its death. It is the third brightest star in the sky. In its bloated last stages of existence Arcturus has swollen to a diameter of about 25 times the size of our Sun's. It lies about 36 light years away. Its orange-red color is distinct with binoculars.
Giant Question Mark in Northern Sky
As darkness falls in July the Big Dipper appears as an upside down question mark in the northern sky. The Big Dipper is the most recognized shape in the sky. From most of the northern half of the Earth it never sets! It just goes around the North Star, making one giant circle each 24 hours. Even though the Big Dipper is one of the largest star shapes in the sky, it is only part of a still larger constellation called Ursa Major, or Big Bear (good luck seeing a bear - the people who named it must have been smoking some of that funny stuff). A recognizable shape, such as the Big Dipper, that is part of one or more constellations is called an "asterism".The Big Dipper can save your life if you are ever lost at sea or in a wilderness area, by providing a way to determine which direction is north. The two stars at the dipper end (not the handle) are called the "pointers". They point to Polaris, the North Star. If you follow an imaginary line extending from the pointers 3 fist widths across the sky (the width of your fist with arm extended) in the direction of the open side of the dipper, you come to the North Star. It is not a bright star, but it is the brightest in that part of the sky.
Full MoonThe next full moon occurs on the night of July 29/30. The moon is full when it is on the opposite side of the Earth from the Sun, so that the part of the moon that faces us also faces the Sun. Therefore, at the time of a full Moon, the Moon rises in the east at about the same time that the Sun sets in the west.
The best times to view the moon with binoculars or telescope is definitely not around the times of a full Moon. It is during the times when the moon is in the crescent to half moon shape. It is at this time that the shadows on the Moon are the longest, making the craters and mountains on the Moon more visible and three dimensional. The best place to look is around the areas where the light and dark sides of the Moon meet. This dividing line, called the "terminator", is where sunset or sunrise is occurring on the Moon, and shadows are the longest.
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