SKY REPORTER: June 2011

Sky Data

Hubble Space Telescope image showing pillars of hydrogen gas and dust capped by sites of emerging bright young stars.
Credit: J. Hester, P. Scowen (ASU), HST, NASA

During June the Sun reaches its highest annual elevation in our sky and summer returns to the northern hemisphere.

Wednesday June 1st, civil twilight begins at 4:54 a.m. and sunrise is at 5:27. That evening the sun sets at 8:21 p.m. and civil twilight concludes at 8:53. Earliest sunrises of the year, at 5:25 a.m., occur from Sunday June 5 until June 20th. The latest sunsets take place at 8:31 p.m. from Wednesday June 22 through the end of the month.

On the last day of June civil twilight begins at 4:54 with sunrise is at 5:28 a.m. That evening sunset occurs at 8:31 p.m. and civil twilight ends at 9:04.

Average overnight temperatures rise from 59 degrees Fahrenheit at the start of June to 67 degrees the night of June 30 - July 1.

Principal Phases of the Moon during this month are:

Sky Cast

On the evening of Saturday June 4th, the waxing crescent moon is low in the west-northwest among stars of the constellation Gemini, including the “Twins” Castor and Pollux.

At the start of June the only bright planet in the evening sky is Saturn. On the nights of June 9th and 10th the waxing gibbous Moon is in the constellation Virgo near Saturn. That planet currently is at visual magnitude 0.77, about the same as Spica, brightest star in Virgo.

During the second week of June Saturn is in proximity with renowned third magnitude double star Porrima, a.k.a. Gamma Virginis. Apparent separation between the star and Saturn that week is about half the diameter of the moon’s disk. By the end of June Saturn, as it moves eastward through the zodiac, will have doubled its apparent distance from Porrima. Current separation between stellar components in the Gamma Virginis binary system is about one arcsecond. This dramatically compares to maximum separation of about six arcseconds, which last occurred during the 1920’s. Seeing any gap between these components is currently a difficult task even when using rather large telescopes under excellent sky conditions.

At ten p.m. Thursday the ninth of June, brilliant star Arcturus is near the celestial meridian. This dividing line extends from north to south through the zenith, cleaving the sky into eastern and western halves. The meridian provides the “m” in our a.m. and p.m. designations of time. The designation a.m. (“ante” meridian) means the Sun has not yet reached the meridian and p.m. (”post” meridian) indicates the center of the Sun’s disk has passed the meridian.

Here’s a quick question: when do most people eat lunch? Around 12 am or 12 pm? The answer is neither! Midday is properly called 12 noon, and every new calendar date begins at 12midnight. However references to 12 a.m. and 12 p.m. are pervasive and use of these designations seems to be on the increase. Show astronomical awareness by encouraging use of more rational alternatives such as 12 mn for midnight and 12 nn for noon.

Jupiter, Mars, and Venus are all visible in the eastern sky during early morning hours throughout June. On Wednesday June 15th, the planets rise in turn at the following times: Jupiter at 2:42 a.m., Mars at 3:45 a.m., and Venus at 4:25 a.m., shortly before beginning of civil twilight.

Combined images of the Galactic Center region, from the Hubble Space Telescope in near-infrared light, the Spitzer Space Telescope in infrared light, and the Chandra X-ray Observatory in X-ray light. The bright spot below and to the right of center is the Sagittarius A radio source which surrounds the supermassive black hole at the center of the Milky Way Galaxy. North on this image is towards the upper left. The long axis of the picture spans a distance in the sky of about 30 minutes of arc, equal to the diameter of the lunar disk.
Credit: NASA, ESA, SSC, CXC, and STScI

At midnight, June 15-16, the Full Moon is in the constellation Sagittarius, very close to the direction of Milky Way Galaxy’s center. That is nearly the same place in the sky where the Sun is located on the first day of winter—December 21st every year.

Among many magnificent objects in the sector of sky near this month’s Full Moon is the nebula designated Messier 16. It has yielded some of the most spectacular Hubble telescope images. Although M16 has also long been called either the Eagle or Star Queen Nebula, due to Hubble’s high resolution images and M16’s role as an active site of star formation, the name “Pillars of Creation” is frequently used. The nebula’s distance from the solar system is about 7,000 light years.

Nearly overhead around midnight during last weeks of June, the magnificent globular star cluster Messier 13 is well placed for viewing. Binoculars and telescopes reveal its presence when seen from dark sites far from urban centers. This nearly spherical grouping of about 100,000 stars spans 150 light years and is about 20,000 light years from us. It is believed to have formed over 12 billion years ago.

On Sunday June 21st at 1:16 p.m., the center of the Sun's disk is directly above Earth’s surface on the Tropic of Cancer at a point between the Bahamas and Cuba. At that time summer begins in the northern hemisphere.

The early morning of Sunday June 26th at about four a.m., the Moon is five degrees of arc from Jupiter, which shines vividly at magnitude -2.3 in the constellation Aries.

Sky Lore

During June evenings look toward the eastern sky for stars Vega, Altair, and Deneb. They form the star pattern of the Summer Triangle. Each object is the brightest star in constellations Lyra, Aquila, and Cygnus. Vega is the brightest of the group with an apparent magnitude near zero, approximately the same as Arcturus, which on June evenings is not far from the meridian. Both stars are among the most vivid in our sky.

In the constellation Lyra, near Vega, observers with binoculars or small telescopes can detect an object called the “Double Double” star. More formally known as Epsilon Lyrae, small instruments show just two points of light, but with magnifications over 100 a total of four component stars may be visible.

Due to its great luminosity Deneb in Cygnus the Swan is one of the most distant stars we can see without optical assistance. It is prominent in our sky even at its tremendous distance of about 3,000 light years. By comparison, relatively close Vega is just 25 light years from us.

The third corner of the Summer Triangle is marked by first magnitude Altair in the constellation Aquila the Eagle. It and its immediately adjacent stars Alshain and Tarazed form a small asterism called the “Family of Aquila”. Altair’s distance from Earth is about 17 light years.