The month of July is named for Julius Caesar. This is the first full month of summer for us in the northern hemisphere, and the days will remain long and the nights will be warm and short. There will be many interesting highlights to pack into those short nights this month.

All five of the brightest planets will be visible, we are farthest from the sun, the dwarf planet Ceres will be at opposition, there will be a blue moon and a meteor shower, and the most exciting event of all will be the closest approach of the New Horizons spacecraft to Pluto on July 14.

The epic conjunction of Venus and Jupiter will still be unfolding throughout this month, but now Venus will be drifting noticeably farther away from Jupiter each evening. This pair of our brightest planets will start the month just half a degree apart, which is the width of the full moon in the sky. They will drift to about 7 degrees apart, but then you will notice an interesting effect as Venus starts its retrograde, or western motion, with respect to the fixed background of stars on July 23, so it will again be getting closer to Jupiter from the other side.

Try to look at Venus through a telescope and you will see that it is rapidly getting thinner as it gets closer to the earth. It starts the month about one third illuminated by the sun, but it will end the month appearing as a tiny sliver only 8 percent lit by the sun and almost twice as large as it will start July. It will reach its brightest for the year at minus 4.7 magnitude by the middle of the month. On July 18, the slender waxing crescent moon will be directly below Venus, almost seeming to touch it in the sky. Jupiter will be just to the right and Regulus, the brightest star in Leo, will be just above this illustrious pair of the second and third brightest objects in our sky after the sun itself.

Saturn is still very well placed in the eastern sky in the constellation of Scorpius as soon as it gets dark enough to spot its glowing orb at just fainter than zero magnitude, or fully 100 times fainter than Venus. The ringed planet is still moving in retrograde toward Libra all month. Its rings are still tilted well open at 24 degrees.

Mars finally makes its reappearance in our morning sky just after the middle of the month. The red planet will be very close to Mercury for a few days, but they will be hard to see because the sky will already be quite bright when they rise just 45 minutes before sunrise. Mars is about as small and far away as it can get now, on the other side of the sun from us, with over a year to go before its next opposition. Then Mercury will sink back down into the morning sky for its superior conjunction with the sun, also on the other side of the sun from us.

Pluto will not be the only dwarf planet to make the headlines this month. The largest and first discovered of all the asteroids, Ceres, will reach opposition on July 25 in the constellation of Sagittarius, only about 20 degrees east of where Pluto will be in the same constellation during its historic encounter with New Horizons. Ceres will reach 7.5 magnitude, which means that it will be visible in just a pair of binoculars, unlike Pluto, which will require a 12- inch or larger telescope because it will only reach 14.1 magnitude, or over 500 times fainter than Ceres. The ion-drive powered Dawn spacecraft reached Ceres in March and is slowly descending closer to its icy surface to map it in good detail. It will reach its lowest orbit of just 232 miles in November, when many more well-hidden mysteries of this icy dwarf will begin to be revealed.

July 14 is the big day for Pluto, so mark your calendars. After an uneventful journey of three billion miles over 91/2 years, the highly efficient New Horizons spacecraft is in perfect health and more than ready for its epic encounter. This is the fastest spacecraft we have ever launched. Averaging 36,000 miles per hour, or about half the speed that the earth is always traveling around the sun, New Horizons travels the diameter of our sun every day, which is 865,000 miles.

We have four other spacecraft that are farther out than New Horizons, but none of them have studied any objects beyond Neptune. Since Pluto is tilted almost 90 degrees on its side, similar to the planet Uranus, all five of its known moons orbit perpendicular to the ecliptic plane of our solar system. So New Horizons will essentially act like an arrow shot from earth passing right through Pluto’s perfect miniature solar system, trying to discern the true nature of this distant, enigmatic and complex target.

About the size of a baby grand piano, New Horizons is armed with seven highly sophisticated scientific instruments that will measure many features of this extremely interesting and unknown part of our solar system. These include two cameras in different wavelengths of light, a spectrometer, a radio science experiment, a plasma and solar wind spectrometer, and an interplanetary dust counter.

We already know that little Pluto has more moons than all four of our terrestrial planets combined. During the two days of hectic activity for this probe’s very brief and close encounter with this ancient and alien primordial world, much data will be gathered, and eventually many new discoveries will reveal themselves over the next two years as all this data slowly gets transmitted to us on Earth.

New Horizons will also pass right through the shadows that Pluto and Charon are always casting into deep space, which will give us new insights into their atmospheres and many other details about them that we could not otherwise see. New Horizons will get as close as 6,200 miles above the surface of Pluto and will be able to resolve features as small as a quarter of a mile across.

This is the first mission to pass close by a distant planetary body in 26 years. The last close encounter was Voyager 2 and Neptune in 1989. This will also be the last such mission planned for several more generations. New Horizons will also be able to visit at least one and maybe two more Kuiper belt objects after this great encounter. They are about one billion miles farther out, so it will take about another three years to get there.


July 1: Venus and Jupiter are still very close, about the width of the full moon apart. The moon is full at 10:20 p.m. This is also called the Hay or Thunder Moon.

July 4: The Crab nebula was first seen on this day in 1054. It is about 6,500 light years away, which means that it actually exploded about 7,500 years ago, but the light of this supernova just got to us about 1,000 years ago.

July 6: Isaac Newton published his Principia on this day in 1687. Earth is at aphelion, or farthest away from the sun for the year at 94,506,507 miles today.

July 8: Last quarter moon is at 4:24 p.m.

July 12: The moon will occult Aldebaran in Taurus for observers in Japan and part of Siberia.

July 15: New moon is at 9:24 p.m.

July 16: The first of 21 fragments of Comet Shoemaker-Levy 9 hit Jupiter in the year 1994.

July 18: Venus and the waxing crescent moon are just two degrees apart this evening.

July 20: The first humans walked on the moon in 1969.

July 24: First quarter moon is at 12:04 a.m.

July 25: The moon is near Saturn one hour after sunset. Ceres is at opposition.

July 30: The Delta Aquarid meteor shower peaks this morning.

July 31: The second full moon of July is 6:43 a.m.

Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.