Sky at a Glance | June 19th, 2009

Some daily events in the changing sky for June 19 – 27.

Moon and three planets at dawn
Look early in the dawn to catch Venus and Mars at their closest.

Friday, June 19

  • A small telescope will almost always show Titan, Saturn's largest moon. Tonight Titan is four ring-lengths to Saturn's west. A guide to identifying other satellites of Saturn (and Jupiter!) for amateur scopes is in the June issue of Sky & Telescope, page 47.

    Saturday, June 20

  • Tonight is the shortest night of the year (for the Northern Hemisphere); the solstice is at 1:46 a.m. on the 21st EDT, marking the start of summer. Paradoxically, this is called "Midsummer" Night — traditionally a time of all-night bonfires and partying, when the veil between our world and the world of elves and fairies was supposed to be unusually thin.

  • To end Midsummer Night, busy things are happening at dawn Sunday morning the 21st! About 45 minutes before your local sunrise, clear the bonfire smoke from your eyes and spot bright Venus in the east with faint little Mars just to its upper left. Using binoculars, look well to the left of Venus for the Pleiades, and look about 24° to Venus's lower left to pick up the thin crescent Moon and (lower right of the Moon for North America) Mercury.

    Mercury in turn is just 0.2° from Epsilon Tauri, magnitude +3.5, in the Hyades. Can you see this star? It marks the upper tip of the "V" shape of the Hyades emerging from the sunrise for the year. First-magnitude Aldebaran 3° below them marks the V's southern tip. See the illustration above.

    Rouse the other members of the party to take a look. Welcome to summer.

    Sunday, June 21

  • Have a dark sky? With the arrival of summer, the Milky Way now arches across the eastern heavens after the last lingering twilight finally fades away. The Milky Way runs from Cassiopeia low in the north-northeast through lower Cepheus, then across Cygnus, the Summer Triangle, and Aquila, and down to Sagittarius and Scorpius in the south-southeast.

    Monday, June 22

  • New Moon (exact at 3:35 p.m. EDT).

  • Pluto is at opposition.

    Tuesday, June 23

  • Watch Titan slowly fade into eclipse by Saturn's shadow around 9:50 p.m. Pacific Daylight Time. (Titan re-emerges into sunlight 6 hours 3 minutes later).

    Wednesday, June 24

  • In late June, the head of Scorpius is highest in the south not long after dark. Of the line of three stars forming the head, the middle one, Delta Scorpii, still looks distinctly the brightest.

    It wasn't always so. Prior to July 2000, Delta Scorpii was slightly fainter than Beta above it. Delta's major flareup lasted five years, then the star faded partway down again (see light curve at the AAVSO). To me it looks suspiciously bright again. See our previous article with labeled photo.

    Western view in twilight
    Back in the evening sky, the waxing crescent Moon again passes Regulus and Saturn on successive days. (These scenes are drawn for the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date.)
    Thursday, June 25

  • Another variable star near the head of Scorpius: Bradley Schaefer predicts that the recurrent nova U Scorpii, currently resting at 18th magnitude, is likely to erupt to 8th or 9th magnitude sometime this year. To catch it during its expected 5-hour rise, a lot of telescope users will have to be checking it often. Want to join them? See our article. Observers are especially needed at longitudes around the world that are sparsely populated with astronomers.

    Friday, June 26

  • The waxing crescent Moon is lower left of Regulus at dusk, as shown at right.

    Saturday, June 27

  • Latest sunset of the year (if you're near latitude 40° north).

  • The Moon is lower left of Saturn this evening, as shown at right.

  • Titan is at greatest eastern elongation from Saturn.


    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 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).

    Pocket Sky Atlas
    The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets — galaxies, star clusters, and nebulae — to hunt among the stars.
    Sky & Telescope
    Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts; 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 more detailed and descriptive Night Sky Observer's Guide by Kepple and Sanner, or the classic Burnham's Celestial Handbook). Read how to use them effectively.

    Can a computerized telescope take their place? I don't think so — not for beginners, anyway, and especially not on mounts that are less than top-quality mechanically. As Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand and a curious mind." Without these, "the sky never becomes a friendly place."

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


    This Week's Planet Roundup

    During the second half of June, six of the seven planets (not counting Earth) are positioned at dawn within a 100° span of sky, from low in the east to fairly high in the south. From left to right they're Mercury, the Venus-Mars pair, Uranus, and the Jupiter-Neptune pair.

    This comes 25 years after very the rare gathering of all seven planets — and then-planet Pluto — into a span of only 60° in January 1984.

    Jupiter on June 17, 2009
    Jupiter's Great Red Spot (GRS) is pale this year, and the South Equatorial Belt, which the Red Spot sits in, looks pretty quiet. But the North Equatorial Belt (NEB, below center) is going nuts! In the parts of the NEB north of the Great Red Spot, the prominent white swirls of three weeks ago have morphed into dark chaos. Also note the very long, straight, diagonal red-brown line crossing the NEB.

    Christopher Go took this image at 17:54 UT June 17, 2009, when the central-meridian longitude (System II) was 150°. South is up.


    For all of the Red Spot's central-meridian crossing times, good worldwide, use our Red Spot calculator or print out our list for 2009.


    Mercury (about magnitude 0) is having a poor apparition deep in the glow of dawn. Look for it in morning twilight about 25° lower left of Venus and Mars. Binoculars will help.

    Venus and Mars (magnitudes –4.3 and +1.1, respectively) remain together due east during dawn. Venus is a dazzler; Mars is 150 times fainter. They're only 2° or 3° apart this week, hardly more than a finger's width at arm's length. June 22nd is their conjunction date, when they're separated by 2.0°. Look for Mars to Venus's upper left early in the week, and directly above Venus later.

    Four reasons combine to create their great disparity in brightness. Mars is farther from the Sun so it's illuminated less brightly than Venus, Mars is a smaller planet, its surface is darker and less reflective than Venus's white clouds, and Mars is currently farther from Earth.

    Jupiter (magnitude –2.6, in Capricornus) now rises before midnight and shines brightly in the south by dawn. The sharpest telescopic glimpses may come during morning twilight, when the atmospheric seeing sometimes turns very steady.

    Dim-ringed Saturn on June 16, 2009
    On June 16th Saturn's rings were still tipped 3.7° to our line of sight, but they were tipped a mere 0.8° to the incoming sunlight. All year the rings' tilt to the Sun has been steadily decreasing, and accordingly, the rings have been getting darker and darker. Keep watch! Saturn is becoming harder to observe as it moves lower in the west each evening.


    S&T's Sean Walker took this stacked-video image using a 14-inch Schmidt-Cassegrain scope at f/22, a DMK21AU04.AS camera, and Custom Scientific RGB filters.

    S&T: Sean Walker
    Saturn (magnitude +1.0, in Leo) is still fairly high in the west at dusk, but it sinks lower as the evening advances. In a telescope Saturn's rings are narrowing again, appearing only about 3.5° from edge on. And see how they've dimmed! The caption at right tells why.

    Uranus (magnitude 5.8, in Pisces) is between Venus and Jupiter before dawn.

    Neptune (magnitude 7.9, in Capricornus) remains only 3/4° from Jupiter, but it's 16,000 times fainter. See our finder charts for Uranus and Neptune.

    Pluto (14th magnitude, in northwestern Sagittarius) is highest in the south around midnight or 1 a.m. See the finder chart in the June Sky & Telescope, page 53.

    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 (also known as UT, UTC, or GMT) minus 4 hours.


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