The Night Sky This Month (June 2013)

The Planets Mercury In the evening twilight as June starts, innermost Mercury can be seen setting in the west. To its lower right Venus glows brighter, and after another small span to the lower right of Venus is the planet Jupiter. This is the tightest three-planet grouping visible with the naked eye until the year 2026! The three planets fit within a 5° circle, meaning you can see all of them in the same binocular field of view. Despite seemingly

crossing paths, the planets remain quite a distance from the Earth and each other. Mercury is 96 million miles away, Venus 150 million miles and Jupiter is 567 million miles away.

For Mercury, this June apparition is the best of this year. Setting almost two hours after the Sun early in the month, the planet stands about 10° above a good, low horizon in the west at mid-twilight.

By June 7th, though, the little planet slowly begins to sink toward the horizon and also starts to fade. It remains on view until about June 25th, appearing no brighter than the stars Castor and Pollux above it. Inferior conjunction does not occur until July 9th.

Finder map (early June) - 30 minutes after sunset, looking west.
Finder map (mid-June) - 30 minutes after sunset, looking west.

Venus

Venus' thick atmosphere was photographed above in ultraviolet light by the Hubble Space Telescope. NASA/JPL [larger image]

Venus is often considered the Evening Star or the Morning Star, depending on which time of day it is up and dominating the twilight. For example, until early January, 2014, Venus will appear as a brilliant yellow star in the evening sky, right after sunset. Located 10° above the western horizon half an hour after sundown, it remains on view until after 10 P.M. local daylight time. At the beginning of June, Venus spans 10.3" across and shows a disk 96-percent lit. By late in the month, the disk has grown to 11.2" and the phase has shrunk to 90-percent illumination. The planet shines at a stunning -4 magnitude, about ten times brighter than the brightest star Sirius, and by far the brightest celestial object after the Sun and Moon. Venus is so bright due to a combination of factors. Venus is covered with an opaque layer of highly reflective clouds of sulfuric acid. These clouds reflect 70-percent of the sunlight that hits them. For comparison, the Earth reflects 36- percent and Mars and the Moon around

15-percent of the sunlight striking them. Venus is also rather large, being only a bit smaller than the Earth - its radius is 95-percent as large as Earth's. The final piece of Venus' brightness puzzle is its close distance to Earth. Right now, the planet is 1.6 astronomical units (150 million miles) from Earth.

Finder map (early June) - 30 minutes after sunset, looking west.
Finder map (mid-June) - 30 minutes after sunset, looking west.
Finder map (late June) - 30 minutes after sunset, looking west.

Mars

Telescopic observations of Mars in the late 19th century showed long surface lines that some believed were irrigation canals. Above, a map of Mars by Giovanni Schiaparelli. "Meyers Konversations- Lexikon" Encyclopedia [larger image]

Mars is very slowly returning to dawn visibility. In late June, skywatchers can use binoculars to look for its magnitude +1.5 speck a mere 5° lower right of Alnath, the star Beta in the constellation Taurus. The planet comes up approximately one hour before the Sun and can be glimpsed briefly very low in the east- northeast during early dawn.

Of the possible nearby sites for life, Mars has traditionally been everyone's top of the list. In the late 19th century, some astronomers astounded the general public by claiming that thin, straight lines could be seen crisscrossing the surface of Mars. They were first described by the Italian astronomer Giovanni Schiaparelli during the opposition of 1877, and confirmed by later observers.

These "canals" bespoke the existence of an advanced society on the Red Planet. Unfortunately, the canals turned out to be just optical illusions. Nevertheless, of all the worlds in our solar system, Mars is most like Earth. It still beckons us with the prospect of nearby, primitive alien life.

Finder map (late June) - 30 minutes before sunrise, looking east.

Jupiter

Gas giant Jupiter requires your attention as soon as it gets dark, before it gets too low to observe. In the first days of June, look for Jupiter well below Mercury and Venus, just a few degrees above the western horizon.

After about June 5th, Jupiter will probably be swallowed in the afterglow of sunset and will become impossible to observe. The planet will be in conjunction with the Sun on June 19th.

Jupiter orbits the Sun 5.2 times further out than the Earth. At this distance, the Sun's light and heat are only 1/27 as strong as at Earth, so without any other source of heat the planet and its satellites would be very cold.

However, Jupiter's atmosphere gets almost as much heat from the interior of the planet as it does from the Sun. The heat is a result of the planet's great size, and it seems that it is also what drives the atmospheric storms that can be seen with amateur telescopes as white and dark ovals.

Finder map (early June) - 30 minutes after sunset, looking west.

Saturn

Pictured above, Saturn's famous rings are visible along with two of its largest moons, Dione and Rhea. NASA's Voyager 2 took this "true color" photograph on July 21, 1981. NASA [larger image]

Saturn reached opposition in late April, and now it slowly heads towards its conjunction with the Sun on November 6th. Look for it in the south as evening twilight fades, to the lower left of Spica and farther lower right of Arcturus. A small telescope will reveal Saturn's system of rings which span 40", surrounding a disk about 18" in diameter. The rings are tilted 18° to our line of sight, the widest open they have been since the year 2006. The planet's ring system is unique, and quite unlike the obscure rings of Jupiter, Uranus and Neptune. Six major rings all lying in the equatorial plane of Saturn have been identified, of which three, in addition to the Cassini division and a subtler demarcation called the Encke division, can be seen from the Earth with a good telescope. Saturn's rings are made up of many small particles, all moving round the planet in the manner of tiny moons. There is no mystery about their composition; they are made primarily of water ice.

Finder map (early June) - 30 minutes after sunset, looking southeast.
Finder map (mid-June) - 30 minutes after sunset, looking south.
Finder map (late June) - 30 minutes after sunset, looking south.

Uranus

Uranus' blue-green color shows up through backyard telescopes, but you will not see storms or the rings Hubble viewed here. NASA/ESA/M. Showalter [larger image]

The ice-giant planet shines at magnitude +5.8 (it is a borderline naked eye object under dark skies) and currently lies among the dim background stars of Pisces the Fish, near the constellation's southern border. To find it, wait until 3 A.M. local daylight time or later for this region to climb reasonably high. Then, locate the two stars that form the eastern side of the Great Square of Pegasus, Alpheratz and Algenib. Next, draw an imaginary line between these two bright stars and continue it 15° to Algenib's south. Uranus should now be centered in your eyepiece's field. Uranus was discovered on March 13, 1781 by German-born British astronomer William Herschel, using a 6.2-inch reflector with a magnification of 227x. Herschel realized that the object - at that time in the constellation Gemini - was not a star, but he believed it to be a comet, and indeed his communication to the Royal Society was headed "An Account of a Comet". There was prolonged debate over the naming of the new planet. J. E. Bode suggested Uranus,

after the first ruler of Olympus. Other names were proposed - for example Hypercronius and "The Georgian Planet", by Herschel himself in honor of his patron, King George III. It was not until 1850 that the name "Uranus" became universally accepted.

Finder map - field width 15°, stars to magnitude +8.

Neptune

Seek out Neptune just before dawn, in central Aquarius, 1° northwest of the 5th-magnitude star Sigma Aquarii. The distant world lies 2.8 billion miles from Earth and glows dimly at magnitude +7.9. A 4-inch diameter telescope is probably the minimum required to see the planet and resolve its disk, only 2.5" across.

Neptune takes almost 165 years to complete one journey round the Sun, so that it was discovered about one "Neptunian year" ago. Like Uranus, Neptune shows a light bluish color (from methane in the atmosphere). The main constituents are molecular hydrogen and helium; methane makes up a minor amount.

Neptune's atmosphere is marked by cirrus clouds and large storms, most notably the Great Dark Spot. This darker bluish-gray region circling the planet's Southern Hemisphere rotates counterclockwise in a few days. A region of high pressure, the Dark Spot is surrounded by white clouds of ammonia and is similar to storms on Jupiter.

Finder map - field width 15°, stars to magnitude +8.5.

Pluto

Clyde Tombaugh, the American astronomer best known for discovering the dwarf planet Pluto in 1930, at his family farm in Kansas. Tombaugh had been a gifted telescope builder - over the course of his life, he built more than 30 instruments. NASA [larger image]

Next month, on the night of July 1st, Pluto comes to opposition. Throughout June, it can be found in the constellation Sagittarius, close to the 3rd-magnitude star Xi 2 Sagittarii. Search for it well after midnight, under a dark, moonless sky. Pluto glows at magnitude +14, and as a result, it is a challenge to spot. An 8-inch telescope on a perfect night brings Pluto to the edge of visibility. For a direct view, however, you will want to use at least a 10-inch scope. The dwarf planet was discovered in 1930 as a result of an extensive search by American astronomer Clyde Tombaugh. He used a blink comparator to reveal the motion of any planet relative to the background stars on pairs of photographic plates taken a few nights apart. On plates taken on January 23rd and January 29th, Tombaugh found a faint object which was moving by the amount expected of a trans Neptunian planet. The newly discovered object was named Pluto, after the ancient Greek god of the underworld.

The two finder maps below will help you identify Pluto. First locate its general position on the coarse finder map, and after you have identified the 6th-magnitude guide star HD 173425 use the fine finder map which shows the position of the dwarf planet on each night of the month.

Coarse finder map - field width 10°, stars to magnitude +8.5.
Fine finder map - field width 1°, stars to magnitude +14.5.

The Deep Sky

Nebulae are enormous clouds of gas ("nebula" is Latin for cloud). Our Milky Way Galaxy is permeated with gas, most of it hydrogen and helium, which is concentrated in its spiral arms. In most cases, this gas can form into dense nebulae. If they are illuminated by nearby stars, nebulae shine brightly and appear as wispy clouds when seen through a telescope; if unilluminated, they appear as blotches of darkness silhouetted against the background stars. There is no

The "Pipe Nebula" is easily visible with the naked eye in the constellation Ophiuchus, the Snake Holder. ESO/Yuri Beletsky [larger image]

difference between a dark nebula and a bright one, except for the lack of illumination.

Dark nebulae (or absorption nebulae) can be enjoyed with the unaided eye, with binoculars and rich-field telescopes (RFTs), or with the largest amateur instruments. They range from small black voids a few arcminutes across to the Great Rift of Cygnus, stretching more than 120° from Deneb to Alpha Centauri.

Few dark nebulae are as prominent as the Great Rift, however. Most are subtle contrast features winding through the richest star clouds. A perfect example is the 7°-long Pipe Nebula, a beautiful naked eye object in southern Ophiuchus.

Start your search about 10° east of Antares. Look for a line of three stars of magnitudes +3 and +4, the only prominent stars in that area of sky. The brightest, Theta Ophiuchi, lies at the line's midpoint and the bowl of the Pipe Nebula is centered 3° southeast of Theta. The bowl, designated Barnard 78, appears as a jagged rectangular formation, with an opacity of 5. In a 1 to 6 scale, the most opaque dark nebulae are classed as opacity 6, and the least opaque as opacity 1.

The pipe's stem is formed from Barnard 59, 65, 66, and 67. It extends for over 5° to the west from the base of the bowl. With the unaided eye, the stem looks like a nearly straight dark cloud. The subtle details come to light when viewed through binoculars, only if the skies are especially clear.

Finder map - field width 25°, stars to magnitude +7.

Asteroids

Scorpius anchors the southern summer sky on late evenings. This June, asteroid 88 Thisbe lies 10° to the upper right of Antares, Scorpius' brightest star. T. Credner & S. Kohle, AlltheSky.com [larger image]

A great way to see the solar system in motion is to track an asteroid. This June, look toward the south in the late evening and locate the twinkling red star Antares (Alpha Scorpii). Normally, 1st-magnitude Antares ranks second in the southern summer sky only to 0- magnitude Arcturus to its upper right. But this year, blazing Saturn also upstages it. Look for Antares about 30° to Saturn's lower left. Antares is your signpost to this month's asteroid highlight: 88 Thisbe. From the star, move your telescope 10° to the northwest and 88 Thisbe should be somewhere in your eyepiece's field. The finder map below shows all background stars as bright as Thisbe (up to magnitude +11). This will help you identify the asteroid using basic pattern-shapes. If you are not sure which dot of light is Thisbe, sketch the field including as many stars as you can, then come back in a night or two to see which one moved. 88 Thisbe was discovered by the German- American astronomer C. H. F. Peters in 1866, and was named after a heroine of a Roman

fable. It is one of the largest main belt asteroids, with a mean diameter of around 130 miles.

Finder map - field width 5°, stars to magnitude +11.

Comets

Comet C/2012 F6 Lemmon put on a nice show for Southern Hemisphere observers, from January and well into March. It approached the Sun down to 0.73 astronomical units (68 million miles) on March 24th, when it brightened up to 5th magnitude. On April 20th the comet crossed the celestial equator, and in early May it became observable from mid-northern latitudes.

This month, you can search for Comet Lemmon in the wee morning hours, well above the eastern horizon. Begin by sweeping slowly with binoculars about one hour before sunrise, looking for a fuzzy "star" with a short stub of a tail. The most recent magnitude estimates put the comet at around 7th magnitude, making it an easy target even in suburban skies.

In the coming months, the comet will get progressively higher in the sky. It will pass within 10° of the north celestial pole on August 10, only to head back out into the outer fringes of the solar system once again. Comet Lemmon will not return for another 11,000 years!

Finder map - field width 35°, stars to magnitude +6.5.

Comet PanSTARRS passed close to the Andromeda Galaxy, M31, during the first week of April. Brendan Alexander [larger image]

Comet C/2011 L4 PanSTARRS was discovered in June 2011, using the PanSTARRS telescope located near the summit of Haleakala, on the island of Maui in Hawaii. At the moment of discovery it had an apparent magnitude of +19, but preliminary calculations soon made it clear that this new object had the potential to become a comet of considerable interest for observers in the Northern Hemisphere. By early May last year, the comet had brightened to

magnitude +13 and could be seen visually with large amateur telescopes. In the months since then, comet PanSTARRS grew even brighter and was spotted with the naked eye in early February this year, by Southern Hemisphere observers.

On March 10th, PanSTARRS passed closest to the Sun and many observers glimpsed it with just naked eyes. Throughout April and May, the comet's rapid northward motion gradually carried it away from the Sun and higher into the evening sky. At the same time, PanSTARRS grew fainter; at magnitude +5 or +6 it was only visible through small telescopes or binoculars.

Now, in June, the comet is circumpolar for observers located at mid-northern latitudes. It never sets and can be viewed all night, in the constellation Ursa Minor the Smaller Bear. PanSTARRS glows at 8th magnitude and appears as a dim, round fuzz ball roughly 5' across, with no hint of a tail. The comet's orbit is bringing it by the Sun for the first time; in the coming months it will fly back out again, never to return.

Finder map - field width 35°, stars to magnitude +6.5.

Meteors

People spend a lot more leisure time outdoors during the summer months, so it is no wonder they observe more meteors at this time of the year. If you can survive the onslaught of hungry mosquitoes, a June evening can be a great time to view a few shooting stars blazing across the sky. The only equipment you will need is your eyes and a modest amount of patience. The best meteor shower of June, in terms of both sky position and meteor activity, is the June Bootid stream. This well-known annual shower usually produces just a few visible meteors per hour, yet fifteen years ago, on June 27, 1998, northern sky watchers were surprised when dozens of bright meteors suddenly began to stream out of the constellation Bootes the Herdsman. It was not the first time: similar June Bootid outbursts had

Meteors are tiny specks of space dust that burn up during their fatal encounter with the Earth's upper atmosphere. Yuichi Takasaka [larger image]

been recorded many decades ago, in 1916, 1921, and 1927.

This year the June Bootids reach a peak on June 27th, and can be seen from about June 22nd through until July 2nd. The shower's radiant - the point in the sky from which meteors appear to originate from - is located in northern Bootes, and will be excellently positioned as darkness falls. It will appear nearly overhead and will remain in view through the whole night.

This is great news, but will you see a large number of meteors coming from Bootes on Thursday evening, June 27th? Unfortunately, the answer is probably not; no outburst is expected this year. However, it is worth keeping an eye open. No one knows why the June Bootid shower spiked in 1998, or when it might again.

Keep in mind that members of this shower are extremely slow, with a velocity of only eleven miles per second. Meteors coming from the same radiant in Bootes, but not traveling more slowly than most other meteors visible at that time, are not June Bootids.

Map - June Bootids radiant position.

Some meteors do not belong to any known shower. These are the sporadic meteors, caused by random bits of comet debris spread throughout the inner solar system. They appear randomly across the sky all year long.

In this month's night sky careful observers can expect around six sporadics per hour during the morning hours and two during the dark evening.

Observing Aids

Northern Hemisphere's Sky - This map portrays the sky as seen near 40° north latitude at 11 P.M. local daylight time in early June and 10 P.M. in late June.

Southern Hemisphere's Sky - This map is plotted for 35° south latitude. It shows the sky at 8 P.M. local time in early June and 7 P.M. in late June.

Visibility of the Planets - The table provides general information about the visibility of the planets during the current month.

Phases of the Moon - This Moon Phase Calendar shows the Moon's phase for every day in June.

Jupiter's Moons - The diagram shows the positions of Galilean satellites on each day in June at midnight.

Sky Events

June 8 - New Moon at 10:56 A.M. EDT.

June 9 - The Moon is at apogee, the point in its orbit when it is farthest from the Earth.

June 10 - The Moon is 5.9° south of Venus at 6:19 A.M. EDT.

June 12 - Mercury is at greatest eastern elongation, 24.3° east of the Sun in the evening sky.

June 16 - First Quarter Moon at 12:24 P.M. EDT.

June 18 - The Moon is 0.1° south of Spica (Alpha Virginis) at 2:56 P.M. EDT.

June 19 - Jupiter is in conjunction with the Sun. The Moon is 3.7° south of Saturn at 12:45 P.M. EDT.

June 20 - Mercury is 1.9° south of Venus at 2:18 A.M. EDT.

June 21 - The June solstice occurs at 12:04 A.M. EDT; summer begins in the Northern Hemisphere. Venus is 5.2° south of Pollux (Beta Geminorum) at 11:47 P.M. EDT. June 23 - The Moon is at perigee, the point in its orbit when it is nearest to Earth. Full Moon at 6:32 A.M. EDT. June 27 - The June Bootid meteor shower is at peak activity. June 29 - Last Quarter Moon at 11:54 P.M. EDT.

The information provided on this page is accurate for the world's mid-northern latitudes. Finder maps for the five naked eye planets are plotted for 40° north latitude, but can also be used from other latitudes close to 40° north. Except the two all-sky maps, all other maps can be used no matter the latitude. Local time (local daylight time during summer) represents the time of the reader.

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