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| For education orders please call 1-877-290-8256. Welcome to the July Featured Article! Spot Pluto at Opposition Geoff Gaherty, Starry Night EducationOn the morning of July 4 at 4 a.m. EDT, Pluto will be in opposition to the Sun. Opposition means that Pluto is directly opposite the Sun in our sky. Pluto will rise as the Sun sets, and set as the Sun rises, the only night in the year that it is visible all night.  To find Pluto at opposition, first locate the "teapot" of Sagittarius in the southern sky. Then zero in on Xi2 Sagittarii (magnitude 3.5) and from there hop to the double star BB Sagittarii. Credit: Starry Night software. Pluto was discovered by Clyde Tombaugh at Lowell Observatory in 1930. At the time it was considered to be the ninth planet in the Solar System, but astronomers in 2006 reclassified it as a "dwarf planet," and later created a new category, "plutoid," for objects like Pluto. Pluto was also the first object to be discovered in the Kuiper Belt, so it is also classified as a "Kuiper Belt Object" or "KBO." So many names for such a tiny world.  With BB Sagittarii in your telescope at high power, scan the star field for tiny Pluto. Credit: Starry Night software. Pluto is a rocky world 1485 miles (2390 km) in diameter, with a tenuous atmosphere. It has an unusual orbit. Although its average distance from the Sun is 39.3 astronomical units (3,653 million miles or 5,879 million km), at times it ventures closer to the Sun than Neptune, and at other times much farther away. Its orbit is also inclined 17.2 degrees to the plane of the ecliptic. Pluto is now known to have at least 5 moons, one of which, Charon, is more than half as large as Pluto itself. In slightly more than a year from now, on July 15, 2015, we will get our first close look at Pluto when NASA’s New Horizons probe flies by it. Until then, the most we have seen is a blurry image made with the Hubble Space Telescope. In all but the largest telescopes, Pluto looks just like a star. Although it is not much to look at, there are bragging rights among amateur astronomers for having seen Pluto with their own telescopes. Here’s how to do it. First of all, you need a fairly large telescope, at least 10 inches aperture, because Pluto is currently at magnitude 14.0. Secondly you need a very good chart of the stars through which Pluto is passing. The best printed star atlases go down to 11th magnitude, which is not faint enough. The answer is to print your own finder charts using software like Starry Night. I’ve made two charts to help you on your quest. The first chart shows Pluto in relation to the familiar "Teapot" asterism of Sagittarius. Look first for Xi2 Sagittarii, 5 degrees north of the Teapot’s handle. Close to Xi2 you will find the optical double star BB Sagittarii. Switching to the more detailed second chart, we will use BB Sagittarii to find Pluto. BB Sagittarii is an optical double: two unrelated stars which happen to fall close to the same line of sight. The star on the left is magnitude 7.5, located 2,249 light years away. The star on the right is a Cepheid variable, ranging in brightness from 6.5 to 7.3 magnitude with a period of 6.6 days, and is more than twice as far away at 5,436 light years. No matter where it is in its cycle of variation, it should be brighter than the left star in the pair. The two stars in BB Sagittarii point to a 12th magnitude double star, and just beyond that is where you will find 14th magnitude Pluto. Since Pluto is currently passing in front of a scattering of stars of similar brightness, how will you recognize it? The only way is to plot all the stars in the area on two successive nights: Pluto will be the one that moves. There are two things to watch out for when trying to spot Pluto. First is that Pluto is a moving target. My chart shows it at the exact time of opposition, 4 a.m. EDT on July 4. At any other time or date, it will be elsewhere. That’s why you need to use a planetarium program like Starry Night that will allow you to set the exact time and date of your observation. To give you some idea of how much Pluto moves in 24 hours, it is about the same angle as the separation between the two components of BB Sagittarii. The other problem is that, when you get down to stars as faint as 14th magnitude, no planetarium program is 100 percent accurate. All use various star catalogs, but no star catalog is 100 percent perfect. This is another reason for sketching the stars yourself at the eyepiece. What I often do is to start with the chart generated by Starry Night, and then compare it with what I actually see through the eyepiece. Then I plot anything that isn’t on the printed chart. Finally, the next night I revisit the area, and plot the stars all over again. Once you have spotted Pluto, you can truthfully say that you have seen the farthest object in our Solar System visible with the human eye. There have been many new Kuiper Belt Objects discovered in the last few years, but all are fainter than magnitude 16, and well beyond the reach of amateur telescopes. Coming Events Here is a rundown of events coming soon to a sky near you!Planets Mercury sets just after the Sun for the first two weeks of the month, but will be too close to the Sun to be seen for the last two weeks. 
Venus is low in the eastern sky, rising just before the Sun.
Mars is now fading rapidly in brightness as it moves towards the far side of the Sun.
Jupiter is now low in the western sky at sunset, and is lost behind the Sun at the end of the month.
Saturn, in Libra, is well placed in the southern sky for most of the night.
Uranus is located in the constellation Pisces, rising just before the Sun.
Neptune is in Aquarius all month, rising after midnight.
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