The Night Sky of June

Dr. Wayne Wooten
Professor of Astronomy

For June 2010, the Moon will be Last quarter on June 4th, so the two weeks finds the moon waning in the morning sky. On the 6th, the waning crescent moon passes 4 degrees north of Jupiter in the morning sky. The new moon is June 12th, with the waxing crescent moon passing by brilliant Venus on June 15th, then below Mars on June 17th. The first quarter moon is June 19th, and the full moon on June 26th. This is the Flower, Strawberry, Rose, or "Honey" moon, depending on the culture. The beginning of summer occurs at 6:29 AM CDT on June 21, the longest day of the year, with about 14 hours of daylight for the Gulf Coast.

While the naked eye, dark adapted by several minutes away from any bright lights, is a wonderful instrument to stare up into deep space, far beyond our own Milky Way, binoculars are better for spotting specific deep sky objects. For a detailed map of northern hemisphere skies, about May 30th visit the www.skymaps.com website and download the map for June 2010; it will have a more extensive calendar, and list of best objects for the naked eyes, binoculars, and scopes on the back of the map.

The brightest planet now in the evening sky is Venus, dominating the western sky. In the telescope, Venus appears only as a bright gibbous disk, but as it approaches the earth, it appears larger but thinner. On June 1st, it is 80% sunlit, but only 13" of arc across. By the 31st, it is only 70% sunlit, but up to 16" of arc across.

Mars is also out overhead in the evening sky, but much fainter than during the earth’s close approach to it in late January. It moves from Cancer into Leo in June, and passes just a degree north of Regulus, the brightest star of Leo, on June 7th. Its tiny disk is only 6" across, and most telescopes will show only a reddish ball without any detail currently. Still it is first magnitude, and its reddish color with the naked eye makes it stand out well.

High up in the southern sky is the most beautiful planet, Saturn, in the arms of Virgo now. Saturn’s rings are now open about 5 degrees; they will continue opening up wider until 2017, when they are tilted 27 degrees toward us and the Sun. You may also see some belts and zones on the planet’s disk. The largest, Titan, will be seen in any small telescope, but others will need larger scopes to spot.

The winter constellations are being swallowed up in the Sun’s glare, but you might spot Sirius low in the SW as June begins. Sirius vanishes into the Sun’s glare by mid-June, and this sets the period as "Dog Days", when Sirius lies lost in the Sun’s glare. In reality, Sirius is about 20x more luminous than our star, but also lies eight light years distant, while our star is eight light minutes away from us.

The brightest star in the NW is Capella, distinctively yellow in color. It is a giant star, almost exactly the same temperature as our Sun, but about 100X more luminous. Just south of it are the stellar twins, the Gemini, with Castor closer to Capella, and Pollux closer to the Little Dog Star, Procyon. By the end of June, all the winter stars, like Sirius, are vanished behind the Sun.

Overhead, the Big Dipper rides high. Good scouts know to take its leading pointers north to Polaris, the famed Pole Star. For us, it sits 30 degrees (our latitude) high in the north, while the rotating earth beneath makes all the other celestial bodies spin around it from east to west.

If you drop south from the bowl of the Big Dipper, Leo the Lion rides high. Saturn lies just west of the bright star Regulus, the heart of the King of Beasts. Note the Egyptian Sphinx is based on the shape of this Lion in the sky.

Taking the arc in the Dipper’s handle, we "arc" SE to bright orange Arcturus, the brightest star of Spring. Cooler than our yellow Sun, and much poorer in heavy elements, some believe its strange motion reveals it to be an invading star from another smaller galaxy, now colliding with the Milky Way in Sagittarius in the summer sky. Moving almost perpendicular to the plane of our Milky Way, Arcturus was the first star in the sky where its proper motion across the historic sky was noted, by Edmund Halley.

Spike south to Spica, the hot blue star in Virgo, then curve to Corvus the Crow, a four sided grouping. It is above Corvus, in the arms of Virgo, where our large scopes will show members of the Virgo Supercluster, a swarm of over a thousand galaxies about 50 million light years away from us. Much closer, in the back yard of our own Milky Way, is the closest globular cluster, Omega Centauri. It is faintly visible to the naked eye directly below Corvus, and is a telescopic treat at our June gazes about ten degrees up over the horizon.

The photo give you an idea how this great "star ball" will appear in larger telescopes, and will be one of the most impressive things you can glimpse through the eyepiece of any telescope. This huge cluster is now suspected of being the surviving remnant of a dwarf galaxy, like our deep southern companions, the Large and Small Magellanic Clouds, but with most of its gas and dust long ago stripped away by repeated passes through the disk of our own Galaxy.

To the east, Hercules is rising, with the nice globular cluster M-13 marked on your sky map and visible in binocs. While not as close as Omega Centauri, it is much higher in the sky, and also one of the top telescopic sights in good sized scopes. Several other good globular clusters are also shown and listed on the best binoc objects on the map back page.

The brightest star of the northern hemisphere, Vega (from Carl Sagan’s novel and movie, "Contact"), rises in the NE as twilight deepens. Twice as hot as our Sun, it appears blue-white, like most bright stars. But to the south, Antares rises about the same time in Scorpius. It appears reddish (its Greek name means rival of Ares or Mars to the Latins) because it is half as hot as our yellow Sun; it is bright because it is a bloated red supergiant, big enough to swallow up our solar system all the way out to Saturn’s orbit!

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