Categories: AstronomyObserving

Weekend SkyWatcher’s Forecast – May 21-23, 2010

Greetings, fellow SkyWatchers… Are you enjoying the typical “change of seasons” weather in your area? If skies should clear for you this weekend, we have some very nice lunar challenges along with some very interesting stars! Why not spend a little time contemplating lunacy and gathering a few photons? When ever you are ready, I’ll see you in the back yard…

May 21, 2010 – Today we’d like to wish a happy birthday to Nils Christofer Duner. Born in 1839, this classical astronomer studied the rotational period of the Sun. Duner was an outstanding observer and made 2,679 measurements of 445 double and multiple stars. He also specialized in observing the spectra of red stars, and later made a series of measurements of the Doppler shift caused by solar rotation. As you know, one of our own Sun’s main ingredients is helium. If you would like to see a helium-rich star, look no further tonight than Alpha Virginis See Spica— Spica . As the 16th brightest star in the sky, this brilliant blue-white ‘‘youngster’’ appears to be about 275 light-years away and is about 2,300 times brighter than our own Sun. Although we cannot see it visually, Spica is a double star. Its spectroscopic companion is roughly half its size and is also helium rich.

Now, let’s have a look at the Moon! Tonight’s challenges are craters Cassini and Cassini A, which come into view just south of the black slash of the Alpine Valley.


The major crater spans 57 kilometers and reaches a floor depth of 1,240 meters. Your assignment, should you decide to accept it, is to spot the central crater A. It only spans 17 kilometers, yet drops down another 2,830 meters below the primary crater’s floor!

May 22, 2010 – Let’s begin the day by honoring the 1920 birth on this date of Thomas Gold, an astronomer known for
proposing the ‘‘steady-state’’ theory of the universe; for explaining pulsars; and for giving the magnetosphere its name. Gold was also an auditory research genius. In his interview with D.T. Kemp he stated: ‘‘I’m a compulsive thinker, I never turn my brain off, I’ve never in my life complained of being bored because I’m constantly thinking about some problem, mostly physics I suppose. A problem is always on my mind—evidently even in my sleep because I often wake up with a solution clearly spread out.’’

Tonight let’s take a long Moonwalk together and do some major crater exploration. Try using mid-range magnification in your telescope and see how many of the features you can identify:


(1) Sinus Asperitatis, (2) Theophilus, (3) Cyrillus, (4) Catharina, (5) Rupes Altai, (6) Piccolomini, (7) Sacrobosco, (8) Abulfeda, (9) Almanon, (10) Taylor, (11) Abenezra, (12) Apianus, (13) Playfair, (14) Aliacensis, (15) Werner, (16) Blanchinus, (17) Lacaille, (18) Walter, (19) Regiomontanus, (20) Purbach, (21) Thebit, (22) Arzachel, (23) Alphonsus, (24) Ptolemaeus, and (25) Albategnius.

May 23, 2010 – If you like to venture to the lunar surface tonight, we can enjoy a strange, thin feature that’s a nice challenge! Look toward the lunar south, where you will note the prominent rings of craters Ptolemaeus, Alphonsus, Arzachel, Purbach, and Walter descending from north to south. Just west of them, you’ll see the emerging Mare Nubium.


Between Purbach and Walter, you will see the small, bright ring of Thebit, with a crater caught on its edge. Look further west to spot a long, thin, dark feature cutting across the mare. Its name? Rupes Recta , better known as the ‘‘Straight Wall,’’ or sometimes Rima Birt. The Straight Wall is one of the steepest known lunar slopes, rising around 366 meters from the surface at a 41 degree angle. Be sure to mark your lunar challenge notes and visit this feature again!

If you’d like to take a look at a ‘‘habitable zone,’’ look no further than AX Microscopii (RA21 17 15 Dec – 38 52 02). AX is a dwarf red flare star, which resides only 12.9 light-years from us. Although it might not seem that important, it is the target of interferometric studies searching for planets that may have formed in habitable zones around stars similar to our own. Even though AX is slightly smaller than Sol, this cool main sequence star might in fact be inhospitable, due to its daily flare activity.

Until next week? Ask for the Moon… But keep on reaching for the stars!

This week’s awesome images (in order of appearance) are: Cassini – courtesy of Wes Higgins, Thomas Gold (archival image), Lunar Photo courtesy of Greg Konkel – Annotations by Tammy Plotner, Rupes Recta courtesy of Damien Peach and AX Microscopi was done by Palomar Observatory, courtesy of Caltech. We thank you so much!

Tammy Plotner

Tammy was a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She’s received a vast number of astronomy achievement and observing awards, including the Great Lakes Astronomy Achievement Award, RG Wright Service Award and the first woman astronomer to achieve Comet Hunter's Gold Status. (Tammy passed away in early 2015... she will be missed)

Recent Posts

A Hopping Robot Could Explore Europa Using Locally Harvested Water

Various forms of hopping robots have crept into development for us[e in different space exploration…

5 hours ago

Resources on Mars Could Support Human Explorers

In the coming decades, multiple space agencies and private companies plan to establish outposts on…

12 hours ago

Exoplanet Could be an Enormous Version of Europa

Certain exoplanets pique scientists' interest more than others. Some of the most interesting are those…

1 day ago

The Moon Occults Spica This Weekend For North America

The ‘Great North American Occultation’ sees the Moon blot out Spica Saturday night.

1 day ago

Webb Detects the Smell of Rotten Eggs in an Exoplanet’s Atmosphere

Studying the atmospheres of exoplanets is helpful for several reasons. Sometimes, it helps in understanding…

2 days ago

Ancient People Saw a Kilonova Light up the Sky

What happens when aging white dwarf stars come together? Observers in feudal Japan in the…

3 days ago