Celestia -- A Stargazer's Log

Yankee Stargazer's Almanac

Welcome to an almanac for those of us who are afflicted with a highly contagious and very addictive malady best described as celestial voyeurism. Luckily, the affliction is not fatal. The focus of this site is to provide interesting, meaningful and timely stuff about the important stars and non-stellar objects parading around up there while they are at their very best annual appearance.
I live some 50 miles north of Boston in Goffstown, New Hampshire, where on clear dark nights the constellations are easily distinguished, all four stars of the Little Dipper's bowl shine prominently, and 6th-magnitude stars still make an appearance for the naked eye every now and then -- not a Stellafane mind you, but all in all, pretty good seeing.

Period: May 10 - 16
.... Mars in Gemini, Saturn in Leo, and Mercury low in the west following the setting Sun are the sole evening planets visible to the unaided eye during this period.
.... The Moon visits the famous NGC 2632 (M44, Praesepe, Beehive Cluster) Saturday evening. One of the many "little clouds" that perplexed Aristotle, this remarkable open cluster is very quick to disappear whenever the seeing fades, even just a wee bit. When that happened, sailors of yore knew that a storm was brewing. To the naked eye, M44 appears as a tiny round cloud on clear nights (a sure sign that the seeing is superb) that very easily resolves into individual stars with binoculars.   Interesting is that Galileo's simple telescope (the first ever built, in 1609) enabled him to realize that M44 was composed of some 40 stars, which is just about the count in modern binoculars.
.... The Moon's continuous wobble (known as libration) best reveals Mare Smythii over the current weekend (10th-14th).
.... The Moon is at its monthly prettiest for naked-eye observers on Sunday evening (11th). This always happens on lunar day 5 when Earth, Sun, and Moon are at their optimum spatial relationship to yield this phenomenon.
.... The Moon's First Quarter arrives just before midnight at 23:47 Sunday evening (11th). Note that the terminator is then right down the middle of the lunar face.
.... Use binoculars to check out the Moon, planet Saturn, and the major star Regulus all visiting together on Monday evening (12th).
.... The Moon's continuous wobble (libration) best reveals Mare Humboldtianum over the next weekend (16th-19th). Lunar features exposed by the ongoing wobble are found in the current Sky & Telescope (May 2008, p63).

Anniversaries
May 11, 1999 .... The solar wind suddenly and inexplicably subsides to almost nothing. Consequently, Earth's magnetosphere swells to huge proportions and slowly oozes out into space, losing its atomic charge for two months. Until now, no one ever knew this sort of thing happened.
May 14, 1973 .... SkyLab, the first space station put into orbit, is launched.
May 15, 1713 .... French astronomer Nicolas Lacaille (1713-1762) is born. While using a tiny half-inch telescope during 1751-52 from Cape Town, South Africa, Lacaille put together the first celestial survey of the southern sky for the French Academy of Sciences. In the process, he gave names to 14 new constellations and cataloged nearly 10,000 stars, all of which are visible to the naked eye or in binoculars. For more information regarding this remarkable astronomer see Sky & Telescope (Jul 2002, p39 and Jun 2005, p55).

Celestial Objects
    The better known stars and objects considered to be the cream of the crop during this period are already covered in the unique reference book entitled Up There -- Notes From a Stargazer (2004) and will not be discussed here. These remarkable objects include Alphecca (Alpha Coronae Borealis), the sparkling lucida (major star) of the Northern Crown; the gorgeous Emerald Star (Beta Librae), the type star for all stars with a B8 spectrum; the inimitable Polaris (Alpha Ursae Minoris), the navigator's North Star; Delta Bootis, a wide and pretty double star for binocularists; Mu Bootis, yet another favorite double star for binocularists; the showpiece Delta Serpentis, a very tight double star; the wider but more challenging
5 Serpentis, also a showpiece double star; and NGC 5904 (M5), a magnificent globular cluster in Serpens Caput (the Head of the Serpent) that often shows up to the unaided eye. And should you want the pertinent observational data on all these important objects in one handy reference book then purchase "Up There." See Editor's Notes below for how to order your copy.
    Also up there on display at their annual best are the following less well-known but nevertheless important stars and objects which include a ...
Type Star .... The orange Nu1 Bootis at Ra 15 30.9 Dc 40 50, one of a naked-eye duo of stars and the nearest to the big "kite" asterism of Bootes, serves as a type star for what all stars with a K5 spectrum are supposed to look like. Check it out with binoculars during your evening walk. Look high in the south, to the upper left of the Bootes kite. Incidentally, the Nu Bootis duo is discussed by Seronik in Sky & Telescope (Jun 2007, p46).
Double Stars .... The bluish-white Zeta Coronae Borealis in northwestern Corona Borealis at Ra 15 39.4 Dc 36 38 is an easy double star of very delicate pastels (white & bluish-green) with the numbers 5.1,6.0 B7V,B7V 6". Zeta is considered an outstanding sight by many observers .... Eta Coronae Borealis at Ra 15 23.2 Dc 30 17 on the corona's west side is a very tight binary with the numbers 5.6,5.9 G2V,G2 1" that is a challenging white & gold duo. Eta serves well as a nice test for the small, expensive refractor .... Libra's Struve 1962 at Ra 15 39 Dc -08 47 is a star well off the beaten path. To find it take a small telescope of any size, focus squarely on Beta Librae (the Emerald Star), let the telescope drift unattended for 22 minutes, and voila! -- an easy, very pretty, matched double star (a rarity) with the numbers 6.5,6.6 F6V,F6V 12" some 80 light-years away. Once you have spotted the star look at it with the naked eye to see what our Sun more or less looks like from some 80 light-years away .... Iota Librae, a complex multiple star at Ra 15 12.2 Dc -19 47 is an easy double star with the numbers 4.5,9.4 A0 58" that showed up as pale yellow & purple in Admiral Smyth's 5-inch telescope back in the 1830s. A more modern but nevertheless rare picture of this pretty double appears in Sky & Telescope (June 2003, p106). Incidentally, the primary star of Iota Librae is itself a binary double (Norton) thus making Iota Librae a complex multiple star.
Variable Stars .... The very red star V Ophiuchi at Ra 16 26.7 Dc -12 26 should be at peak (mag 7.5) about now, making it one of the more prominent stars (in your finderscope) just southwest (lower right) of the naked-eye Zeta Ophiuchi. Use your telescope and look right at this beauty to appreciate the deep-red hue of this N-type carbon star. See Sky & Telescope (July 2002, p89) for its sky chart and more details .... T Ursae Majoris, a reddish Mira-type variable star with a 257-day period found at Ra 12 36.4 Dc 59 29, is now rising from the depths of magnitude 13 to an easy binocular magnitude of 6.6 (its historical max). Look for it about one degree northeast of the prominent duo of 74-75 Ursae Majoris which is easily found on the north side of the Delta-Epsilon segment of the Big Dipper's handle. This star was once featured in Sky & Telescope (Nov 2004, p69) .... The star R Bootis, a long-period Mira-type variable, hides out at magnitude 13 most of the time but every now and then it comes up to magnitude 6.2 (almost naked-eye magnitude) for everyone to admire. This red beauty is due up about now. Look for it nightly in the same binocular field as the very prominent naked-eye Epsilon Bootis, just to its west (your right). Class M or Mira-type stars are red, long-period, giant, variable stars with a period between 80 to 1000 days (R Bootis' cycle is about 223 days) and a range in amplitude that can sometimes exceed 5 magnitudes or more. Class M stars are not only quite common but also quite pretty to watch as they rise to their peak.
Globular Cluster .... The challenging globular cluster NGC 5897 at Ra 15 17.4 Dc -21 01 will appear as an isolated smudge in your view-finder. This object was not included in the first edition of "Up There" but it will appear in a subsequent edition as: "Harrington's comment that NGC 5897 is an "ill-defined [binocular] smudge of grayish light" seems to say it all about Libra's most prominent globular cluster. But its lackluster reputation is largely undeserved. Take a look at its pretty picture in Burnham's Celestial Handbook (p1109). Granted, this globular cluster is perhaps the wispiest thing I have ever seen but it is nevertheless unique for being resolvable right to its very core. This thing is so thin that it simply defies the more usual mental image of a globular as a huge tight ball of stars. Listed as a binocular object by Night Sky and reported by Tom Polakis (Astronomy, June 1999, p77) as "fairly easy to spot in 11x80 binoculars," look for this large (13') globular less than two degrees southeast of the naked-eye Iota Librae. Hunt for NGC 5897 with binoculars on a dark night and when it shows up, take out the telescope and look right into its very core."
Galaxy .... About 10 degrees east of the Northern Pinwheel (NGC 5457, M101) and about 3.5 degrees southwest of the prominent naked-eye Iota Draconis lies the 10th-magnitude NGC 5907 (Splinter Galaxy) at Ra 15 15.9 Dc 56 19 that, being an edge-on spiral (12x2'), looks exactly like its namesake, a splinter. This is yet another Herschel 400 List member that fascinates astronomers. The story: An unusually extended, luminous halo was discovered surrounding this galaxy in 1994 by a team investigating dark matter. Five years later (1999) another team used Hubble's near-infrared capabilities to further discover that its halo is virtually empty. The team had expected to find bright, giant stars; but concluded instead that the halo must be composed of a large, homogeneous population of dwarf stars too faint to be picked up by Hubble. However, the knot here is that no such strange population is known to exist anywhere else. Stay tuned. The Splinter is featured as NASA's astronomy picture of the day for May 10, 2001.

Lunar Objects
Features on the Moon are always best seen when sunlight strikes them at its lowest angle -- the main reason why veteran lunar observers monitor the terminator (the night-day line) which is right down the middle of the lunar face by Sunday evening (11th) when the Moon is at First Quarter.
May 10 (lunar day 4) .... Situated about midway amidst a strip of highlands serving as the common boundary between Mare Crisium and Mare Tranquillitatis, the rather small but very bright crater Proclus (Wood's #12 at E46.8 N16.1) is not only polygonal in shape but is also the center of an unusual "oblique impact ray system." The interior of this 18 mile (29 km) wide, 12,000 feet (3,700m) deep sharply-edged crater contains in part a large sector of exceptionally bright material and is the epicenter for two conspicuous fans of bright ejecta extending south and northwest respectively for a whopping 200 miles (320 km), while other less prominent rays extend eastward onto Mare Crisium itself. Cherrington notes that this system of very lengthy rays is not immediately apparent however but requires repeated observations under different light conditions to be seen. The mechanics of oblique impacts is discussed more fully by Wood in Sky & Telescope (July 2007, p55). By the way, Proclus is one of the dozen most active transient lunar phenomena (TLP) sites on the Moon's face.
May 11 (lunar day 5) .... Mare Nectaris (Sea of Nectar at E35 S15), the smallest of the moon's major seas, is bathed in a lunar sunrise as the "sunrise" terminator slowly progresses westward. Pickering assigned a "No 2" to Mare Nectaris on his list of easiest naked-eye lunar features because he probably wanted to point out that all the lunar mare, even the smallest, are quite visible to the naked eye. But note also that the area seen at first glance as Mare Nectaris is really the lava-filled central portion of Mare Nectaris which is actually much larger than at first perceived. This "mega-Nectaris" concept is pictured and discussed by Wood in Sky & Telescope (Jun 2004, p68).
May 12 (lunar day 6) .... The Altai Scarp (Wood's #7 at E22.6 S24.3) appears as a long mountainous range, some 600 miles (960 km) in length, with one side marked by a 3,000-foot cliff; whereas the other side is steep but not cliff-like. The scarp (the surface expression of a fault) extends in a long arc from west of crater Catharina in the north to crater Piccolomini well south of Fracastorius. The cliffs of the Altai Scarp are most noticeable when sunlight is coming in at a very low angle. Some lunar geologists believe the Altai Scarp marks the true southwestern rim of the massive Nectaris Basin.
May 13 (lunar day 7) .... The large, nondescript, and difficult to locate crater Sacrobosco at E16.7 S23.7, often called a "walled plain" because its 98 km (61 mi) diameter exceeds 70 km (44 mi), is one of many craters found amidst the rather tortured topography known as the southern lunar highlands. William Pickering named the bright Sacrobosco area as number 10 on his list of the 12 easiest naked-eye lunar features. I am not sure why, but I think he was pointing out the absolute naked-eye threshold size of bright lunar craters visible under optimum conditions. Incidentally, the Pickering brothers were American astronomers associated with Harvard Observatory. The elder Edward Pickering (1846-1919) distinguished himself as director of this renowned institution for many years, whereas his less than distinguished younger brother William (1858-1938), known more for his bizarre ideas than his discovery of Saturn's tiny moon Phoebe in 1898, was eventually entrusted to establish Harvard's southern observatory high in the Andes Mountains of Peru.
May 14 (lunar day 8) .... According to selenographers (guys who map the Moon), the small bright crater called Mosting A (Wood's #61 at W05.2 S03.2) is the central point of the Moon's near side. The full coordinates of this tiny crater, only 13 km (8 mi) in diameter, are given in Rukl's "Atlas of the Moon" (1990) and its picture appears in Sky & Telescope (July 2004, p69).
May 15 (lunar day 9) .... Now coming into view is Mare Imbrium, a vast and rather featureless mare that almost wholly occupies the Moon's northwest quadrant. The "Sea of Rains" was named as such by the Italian professor of Astronomy, Giovanni Riccioli (1598-1671), whose interesting but rudimentary lunar map published in 1651 essentially established the lunar nomenclature that we know today. Mare Imbrium is the largest lunar basin on the near side of the Moon. It was created by a collision with a huge impactor nearly four billion years ago and it quickly filled with runny lava suspected of being as much as 5 kilometers (3 miles) thick some in places. A rectified view of the entire Imbrium basin is published in Sky & Telescope (Feb 2005, p72).
May 16 (lunar day 10) .... Kies Pi (Wood's #60 at W24.2 S26.9) is perhaps the easiest to spot of the rare volcanoes found on the lunar surface. Now that the terminator is nearby, look for this isolated dome just to the west of the large flooded crater Kies in western Mare Nubium. According to Wood, domes are volcanoes "constructed of ash or lavas erupted from a central vent" (Sky & Tel, June 2005, p63).

Editor's Notes
.... The specific works of authors mentioned herein are found in the list of references given in my book "Up There - Notes From a Stargazer" on pages 167-169.
.... Two of my recently released observational astronomy books are recommended to stargazers of all levels of expertise looking to gain a solid background for their fascinating pastime. These are:
.... Looking Up - An Introduction to Stargazing (2007) describes in non-technical language the various animals of the celestial zoo through historical episodes in order to better understand the very things often discussed on this website.
The cover price is $10.95 and it is currently available directly from the publisher, Vantage Press, through their toll-free number: (800) 882- 3273.
.... Up There - Notes From a Stargazer (2004) is a more comprehensive offering to the practicing stargazer and presents information on the hundreds of popular celestial objects that should be explored at least once during the observer's lifetime. The book is priced at $19.95 (in US funds, please) and is available only through direct mail order. Shipping and handling fees are included. Send your check to: Roger Ducharme, 10 Foxtail Lane, Apt 1, Goffstown, N.H. 03045.
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