Sky at a Glance | June 20th, 2008

By: Alan MacRobert June 20, 2008 0

Some daily events in the changing sky for June 20 – 28.

All week, Mars draws closer to Regulus and Saturn in the western twilight.

Friday, June 20

The June solstice occurs at 7:59 p.m. Eastern Daylight Time, marking the start of summer in the Northern Hemisphere; winter in the Southern Hemisphere. This is when the Sun reaches its farthest north in Earth's sky and begins its six-month return southward.

In the Northern Hemisphere, it's the longest day and shortest night of the year. The night of the summer solstice was traditionally called Midsummer's Night, a misnomer by the modern definition of the seasons. Traditionally, on this night spirit creatures were thought to be especially apparent (hence Shakespeare's A Midsummer Night's Dream), and the event was celebrated with all-night bonfires.

Pluto is at opposition.

Saturday, June 21

With summer now here, it's only appropriate that the big Summer Triangle is up after dark. Its top star is Vega, the brightest star in the eastern sky. Look two or three fists lower left of Vega for Deneb. Look farther to Vega's lower right for Altair. A finger-width above Altair is its little 3rd-magnitude companion star Gamma Aquilae, or Tarazed.

Sunday, June 22

If you can see Jupiter in a telescope from your location between 10:40 and 11:44 p.m. EDT (2:40 to 3:44 June 23rd UT), you can see a double shadow transit on Jupiter's face. The shadows are of big Ganymede and little Europa.

A complete schedule of Jupiter's interesting satellite events for the month, good worldwide, is in the June Sky & Telescope, page 58. For more about observing Jupiter's satellites, see the July issue, page 62.

Monday, June 23

Saturn, Regulus, and Mars are equally spaced in a diagonal line low in the west at dusk, in that order from upper left to lower right. Each planet is slightly more than 4° from the star tonight.

Tuesday, June 24

Look a third of the way from Arcturus to Vega for the dim little semicircle of Corona Borealis, the Northern Crown, with its modestly bright "jewel star," Gemma. Look two thirds of the way from Arcturus to Vega for the dim Keystone of Hercules.

In Keystone of Hercules is one of the most familiar deep-sky objects for binocular observers: the globular star cluster M13. But do you know where to pick up the equally bright globular M92 nearby? For both, see "Binocular Highlight" in the July Sky & Telescope, page 54. Get M92 once and it'll be there for you forevermore.

Wednesday, June 25

The red long-period variable star V Bootis should be at maximum light this week, 7th or 8th magnitude and visible in binoculars. It's just 1° from Gamma Bootis; use the comparison-star chart in the May 2007 Sky & Telescope, page 62.

Thursday, June 26

Last-quarter Moon (exact at 8:10 p.m. EDT).

Friday, June 27

This is the time of year when the dim Little Dipper extends straight up from Polaris after dark, like an escaped helium balloon trailing its string as it rises into the night sky.

Saturday, June 28

Late tonight a 5.6-magnitude star is just 5 arcminutes south of Jupiter, looking like an out-of-place Jovian moon. Meanwhile Jupiter's moon Callisto, similarly bright, is 10′ east of the planet, about as far as it gets.

By the end of June, Mars will partner up with similarly bright Regulus under the watch of slightly brighter Saturn off to one side. The blue 10° scale is about the size of your fist held at arm's length.

Sky & Telescope diagram

Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly foldout map in each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of maps; the standards are Sky Atlas 2000.0 or the smaller Pocket Sky Atlas) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion by Strong and Sinnott, the even more detailed Night Sky Observer's Guide by Kepple and Sanner, or the classic Burnham's Celestial Handbook). Read how to use them effectively.

More beginners' tips: "How to Start Right in Astronomy".

This Week's Planet Roundup

Mercury and Venus are still deep in the glare of the Sun.

Mars and Saturn (magnitudes +1.6 and +0.8) are close together in Leo, getting low the west at dusk. Regulus (magnitude +1.4) is between them; midway between on June 23rd. Look early before they sink too low and set.

Mars will pass ¾° from Regulus on June 30th and July 1st.

Jupiter (magnitude –2.7, in eastern Sagittarius) rises in twilight, left of the Sagittarius Teapot. It shines highest in the south around 2 a.m. daylight saving time. Jupiter will reach opposition on July 9th.

Uranus and Neptune (magnitudes 6 and 8, respectively, in Aquarius and Capricornus) are high up in the southeast before the first light of dawn. Use our article and finder charts.

Pluto (magnitude 14.0, in northwestern Sagittarius) is highest in the south around midnight or 1 a.m. But wait till about June 27th, when moonlight will be gone from the sky at that hour.

All descriptions that relate to your horizon or zenith — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) equals Universal Time (UT, UTC, or GMT) minus 4 hours.

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