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The Night Sky of June

Dr. Wayne Wooten
Professor of Astronomy

The June Full Moon, the Honey Moon, occurs on June 5th. The waning gibbous moon passes below Jupiter in the dawn sky on June 8th, and Saturn on the 9th. The last quarter moon and brightening Mars rise about midnight on June 13th. The most spectacular conjunction of June is the very thin waning crescent moon joining newly visible Venus (also a slender crescent in binocs!) in the dawn on June 19th. The moon is new on June 20th, in parts of Africa and Asia, this is a annular solar eclipse, but it will all be over for us by sunrise. The first quarter moon is on June 28th.

This June Mercury is visible in the NW twilight for the first week; it appears as a half lit disk at greatest elongation of 24 degrees from the sun on June 3rd, but is rapidly lost in the Sun’s glare by midmonth. Venus switches from evening to morning sky, passing inferior conjunction on June 3rd as well. It may be seen just before dawn in the NE by midmonth as a very slender crescent…remember the similarly thin crescent moon joins it on the 19th. Try capturing both crescents in a single telescopic view then! Moving rapidly past us, Venus rises an hour before the Sun by month’s end, and is at its brightest then. Try following it in the day sky with the naked eye!

Mars comes to a historically close opposition this fall, and is already bright red and easy to spot in the dawn in Aquarius. On June 13th, it passes 1.6 degrees below tiny, distant blue Neptune with binoculars for early risers. For perspective, remember Mars is half the size of Earth, and Neptune four times larger, but over 100X more distant!

We are overtaking Jupiter and Saturn now, and both come to opposition at sunset in July. With binoculars, the four large Galilean moons of Jupiter are visible in a row around Jupiter’s equator. Larger scopes will see the famed Great Red Spot is still evident in the belts and zones. Saturn’s rings are slowly closing, but still put on a fine show. Its large moon Titan is also visible even in 60mm refractors at 30X. By month’s end, both are rising within two hours of sunset in the SE. Download the program Stellarium at www.stellarium.org and you can zoom in on the planets to find the layout of the moons of Jupiter and Saturn at any moment.

If you drop south from the bowl of the Big Dipper, Leo the Lion is in the SW. 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. Jupiter lies just east of Spica this June. North of Corvus, in the arms of Virgo, is where our large scopes will show members of the Virgo Supercluster, a swarm of over a thousand galaxies about 50 million light years distant.

Directly below Corvus on the southern June horizon is Crux, the Southern Cross. From West Florida, only its top star, gamma Crucis, is visible, but in Miami, the "Southern Cross Astronomical Society" boasts of their more southern latitude and their ability to see the whole cross. Directly above the Cross and easily visible from the Gulf coast is the largest and brightest globular cluster, omega Centauri. It appears as a round 4th magnitude blur with the naked eyes under dark skies, and is easily mistaken for a new comet, without growing a tail yet.

Alas, as they patiently watched the next few evenings, the comet only a few million miles distant moved rapidly northward, but the great ball of stars stayed fixed in the sky, some 16,000 light years distant. It is the largest such cluster known associated with our Milky Way Galaxy, and is probably itself the core of a small elliptical galaxy that has been stripped of most of its outlying stars in many passes through the plane of our barred spiral. Its gravity in fact may be why our own Galaxy developed its bar!

To the east, Hercules is well up, with the nice globular cluster M-13 marked on your sky map and visible in binocs. 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. At the opposite end of the parallelogram of Lyra is M-57, the Ring Nebula.

Northeast of Lyra is Cygnus, the Swan, flying down the Milky Way. Its bright star Deneb, at the top of the "northern cross" is one of the luminaries of the Galaxy, about 50,000 times more luminous than our Sun and around 3,000 light years distant. Under dark skies, note the "Great Rift", a dark nebula in front of our solar system as we revolve around the core of the Milky Way in the Galactic Year of 250 million of our own years.

To the east, Altair is the third bright star of the summer triangle. It lies in Aquila the Eagle, and is much closer than Deneb; it lies within about 13 light years of our Sun. Use your binocs to pick up many clusters in this rich region of our own Cygnus spiral arm rising now in the east.

To the south, Antares is well up at sunset 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! Scorpius is the brightest constellation in the sky, with 13 stars brighter than the pole star Polaris! Note the fine naked eye clusters M-6 and M-7, just to the left of the Scorpion’s tail.

Just a little east of the Scorpion’s tail is the teapot shape of Sagittarius, which lies toward the center of the Milky Way. From a dark sky site, you can pick out the fine stellar nursery, M-8, the Lagoon Nebula, like a cloud of steam coming out of the teapot’s spout.

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