重庆滴滴专车:This Week's Sky at a Glance for June 24 - July 2

This Week's Sky at a Glance
Some daily events in the changing sky, June 24 - July 2
by Alan M. MacRobert
Frenchobserver Stéphane Lamotte Bailey created this animation of theWhirlpool galaxy's new supernova using images he took with his 8-inchtelescope on May 30 and June 2, 2011.
Stéphane Lamotte Bailey
M51 Supernova update. Supernova 2011dh, which was discovered onMay 31st at 14th magnitude in M51 (the Whirlpool Galaxy by the BigDipper), seems to have topped out at magnitude 12.6. It's visible inmany amateur telescopes now, especially with moonlight gone from theevening sky, but don't delay. Here's an up-to-datelight curve from the American Association of Variable Star Observers. See our originalarticle and finder photo. Plot anAAVSO comparison-star chart (enter the name SN 2011dh).
Friday, June 24
With summer here, looksouth-southeast after dark for the bright constellation Scorpius, "theOrion of summer," now reasonably high and standing upright. Just likeOrion, Scorpius is marked by several 2nd-magnitude blue-white stars andone of the two brightest red supergiants in the sky (Antares in the caseof Sco, Betelgeuse for Ori). However, Scorpius is some 30° farthersouth.
Saturday, June 25
These evenings, look highin the east to spot bright Vega. The brightest star to its lower left,by two or three fist-widths at arm's length, is Deneb (the head of theNorthern Cross). Farther to Vega's lower right is bright Altair. Thesethree stars form the Summer Triangle. The summer Milky Way runs rightthrough the Triangle, along the length of the Northern Cross — if youhave a dark enough sky.
Sunday, June 26
This is the time of yearwhen the Little Dipper floats straight upward from Polaris after dark,like a helium balloon escaped from a summer evening party.
Thewaning Moon passes the Pleiades, Mars, and Aldebaran in the dawn. Thevisibility of the faint objects in bright twilight is exaggerated here.(These scenes are drawn for the middle of North America. Europeanobservers: move each Moon symbol a quarter of the way toward the one forthe previous date. For clarity, the Moon is shown three times actualsize.)
Sky & Telescope diagram
Monday, June 27
About an hour before sunriseTuesday morning, look east. Above and below the waning crescent Moon arethe Pleiades and Mars, respectively, as shown at right. Binoculars willhelp.
A tiny new near-Earth asteroid named 2011 MD,discoveredby the LINEAR project on June 22nd, passes less than one Earth diameterfrom Earth's surface. It's estimated to be 8 to 18 meters (25 to 55feet) wide. Updated June 24: The asteroid should be visible inthe hours leading up to the closest approach across Australia, NewZealand, southern and eastern Asia, and the western Pacific. The farthersouth you are the better. The farther west you are within this zone,the shorter the period of visibility, but the closer to Earth theasteroid will be when it disappears from view. See updatedarticle.
You can create a new ephemeris for your exact observing location using theJPL Horizons ephemeris service. Enter the name 2011 MD.
And yes, there's now aniPhone app for this event (as part of the sky charting program Sky Safari 3).
Tuesday, June 28
Before sunrise Wednesdaymorning, the crescent Moon forms a nice triangle with Mars and Aldebaranto its right, as shown above.
Wednesday, June 29
Vega high in the east,and Arcturus high in the southwest, are the two brightest stars ofsummer. Sometime between 10 and 11 p.m., depending on where you live,they will be equally close to the zenith. How accurately can you timewhen this occurs?
All this week, Mercury climbs higher after sunset toward its June 30th lineup with fainter Pollux and Castor.
Sky & Telescope diagram
Thursday, June 30
Low in the west-northwestduring twilight, Mercury finally forms a straight line with fainterCastor and Pollux, as shown here. Look about 45 minutes after sunset.
Friday, July 1
A small telescope showsSaturn's largest moon, Titan, about four ring-lengths east of the planetthis evening and tomorrow evening. They're a little less that 3arcminutes apart. Bright Porrima is 32 arcminutes to Saturn's northwest.And a little closer to Saturn's northeast is a yellow star of 6thmagnitude.
New Moon (exact at 4:54 a.m. EDT). A slightpartial eclipse of the Sun is theoretically visible just above thehorizon for a small section of the stormy winter ocean off Antarctica.This is an eclipse that not a single human is likely to see, andprobably not even penguins or albatrosses.
Saturday, July 2
Mercury is becoming betterplaced for observers at mid-northern latitudes; look low above thewest-northwest horizon as the glow of sunset fades, as shown below. Thisevening, see if you can spot the very thin crescent Moon below it about20 or 30 minutes after sunset. Bring binoculars.
Watch the waxing crescent Moon thicken and advance eastward from day to day as July gets going.
Sky & Telescope diagram
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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 the center of each issue ofSky & Telescope, the essential magazine of astronomy. Or download our freeGetting Started in Astronomy booklet (which only has bimonthly maps).
ThePocket Sky Atlasplots 30,796 stars to magnitude 7.6 — which may sound like a lot, butthat's less than one star in an entire telescopic field of view, onaverage. By comparison,Sky Atlas 2000.0plots 81,312 stars to magnitude 8.5, typically one or two stars pertelescopic 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 must have a detailed, large-scale sky atlas (set of charts). The standards are thePocket Sky Atlas, which shows stars to magnitude 7.6; the largerSky Atlas 2000.0 (stars to magnitude 8.5); and the even larger and deeperUranometria 2000.0 (stars to magnitude 9.75). And readhow to use sky charts effectively.
You'll also want a good deep-sky guidebook, such asSky Atlas 2000.0 Companion by Strong and Sinnott, or the more detailed and descriptiveNight Sky Observer's Guide by Kepple and Sanner, or the classic if dated Burnham's Celestial Handbook.
Can a computerized telescope take their place? I don't think so — notfor beginners, anyway, and especially not on mounts that are less thantop-quality mechanically. As Terence Dickinson and Alan Dyer say intheirBackyard Astronomer's Guide,"A full appreciation of the universe cannot come without developing theskills to find things in the sky and understanding how the sky works.This knowledge comes only by spending time under the stars with starmaps in hand."
This Week's Planet Roundup
Mercury(about magnitude –0.7) is deep in the glow of sunset. Try looking forit just above the west-northwest horizon about 40 minutes after sunset.Don't confuse it with fainter Pollux nearby, or with Regulus much higherdue west.
Venus (magnitude –3.8) shines barely above the east-northeast horizon as dawn grows bright. Look for it about 20 minutes beforesunrise.
Mars (magnitude +1.4) is low in east-northeast in early dawn, far lower left of Jupiter.
Jupiter is coming into better view now low in the dawn, but it's still very far from its best.Christopher Goobtained this fine stacked-video image on June 8th. Jupiter's darkSouth Equatorial Belt (above center) has fully returned and is verywide. The narrower North Equatorial Belt remains darker red-brown, witheven darker barges. At the time of the photo the Great Red Spot had justbarely passed the planet's central meridian (where the System IIlongitude was 163°). The SEB practically encompasses the Red Spot, andthe Red Spot Hollow around the spot has changed from white to dark.South is up.
Christopher Go
Jupiter (magnitude –2.2, in southern Aries) shines prominently in the east before and during dawn.
Saturn (magnitude +0.9, in Virgo) is southwest after dusk andgetting lower. Shining 14° left of it is similar Spica. And just ½° toSaturn's upper right is fainter Porrima (Gamma Virginis), turning Saturninto a naked-eye "double star."
In a telescope Saturn's rings are 7.5° from edge on. The rings arecasting a their shadow southward onto the globe as a thin black line,and the globe's shadow on the rings is visible just off the globe'scelestial east (following) side. The North Equatorial Belt is a duskyband. North of it, Saturn's seven-months-old white outbreak is stillapparent in good images, as shown here.
See how many of Saturn's satellites you can identify in your scope using ourSaturn's Moons tracker.
And don't skip over Porrima — a fine, close telescopic binary with equalcomponents and a current separation of 1.7 arcseconds. Use high powerand hope for good seeing.
Uranus (magnitude 5.9, in western Pisces) and Neptune(magnitude 7.9, in Aquarius) are about equally high now just before thefirst light of dawn, in the southeast and south, respectively.
Pluto (magnitude 14.0, in Sagittarius) is highest in the south around 1 a.m. A big finder chart for it is in the JulySky & Telescope, page 64.
All descriptions that relate to your horizon — including the wordsup, down, right, and left — are written for the world's mid-northernlatitudes. Descriptions that also depend on longitude (mainly Moonpositions) are for North America. Eastern Daylight Time (EDT) equalsUniversal Time (also known as UT, UTC, or GMT) minus 4 hours.
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