What’s Up This Week – Feb 21 – 27, 2005

M 41 credit: NOAO/AURA/NSF
Monday, February 21 – Tonight let’s head four degrees south of the incredible Sirius and locate an easy binocular or telescope object – M 41. Noted as early as 325 B.C. by Aristotle – and cataloged by Messier in 1765, the M 41 is a beautiful, loose, looping collection of around two dozen bright stars and many more faint members that range with aperture. At around 2,300 light years away, it’s remarkable we can see it at all! Spanning approximately 25 light years, it is estimated this cluster could be as much as 240 million years old. Although the presence of the Moon will harm some of its fainter members, the M 41 sports many red “giant” stars – especially the one in the center!

Now, let’s have a look at the Moon and identify a new crater. Near the terminator and south of Mare Humorum you will find a very notable walled plain known as Schickard. While it doesn’t appear to be much, Schickard is almost as large as the Netherlands! Notice its bright white wall underscored with shadow along the northeast inner wall. Schickard is an unusual crater because of its curvature – it’s convex! At its center, the walled plain is just a little bit more than 213 meters (700 feet) higher than the area at the edges. If you were standing in the middle of this crater and scanning the horizon, you could never see the walls!

Tuesday, February 22 – Since the Moon will dominate the evening sky, let’s start by observing and identifying an “on the edge” feature. Return to previous study area, Sinus Iridum and head north! Near the terminator you will see a slender, bright ellipse with a bright northwest wall and a dark southeast wall. This is the deep, walled plain of class one Pythagoras. Note the bright twin central peak that rises around 1829 meters (6000 feet) high. Considering the angle that we see this area from, that type of elevation is comparable to the height of El Cielo – Mexico’s “Cloud Forest”!

And while we have our head in the clouds, let’s have a look at the eighth brightest star in the sky – Procyon. At around 11.3 light years away from us, the “Little Dog Star” is the fifth nearest star to Earth. It is well known that Procyon is a double star – but that’s a challenge beyond the ordinary backyard scope. Very much like Sirius, the 13th magnitude companion is also a dwarf star – one that’s about twice the size of our Earth!

Wednesday, February 23 – Although the Moon appears full tonight, it’s just not official. According to folklore, this is known as both the “Snow Moon” and the “Storm Moon”… Let’s hope that doesn’t mean certain areas of the world are about to get buried again! Tonight let’s have a look at Selene with either binoculars or telescope. We are looking for the pale, shallow form of Langrenus on the eastern edge of Mare Fecunditatis. It won’t appear very impressive tonight, but let’s see how much it changes in 48 hours!

With incredibly bright skies tonight, let’s turn a little attention toward the dominant star in Auriga – Capella. As the sixth brightest star in the sky, lovely yellow Capella is around 45 light years away. As with most stars, the “Goat” is actually a multiple system! Although its members are too close to be split with average equipment, if skies are steady you might be able to glimpse 10th magnitude red dwarf – Capella H – toward the southeast!

Thursday, February 24 – It’s official… Full Moon at 4:54 UT! Tonight let’s scan the western limb of the Moon and look for the Cordillera Mountains south of Grimaldi. Although this will appear as nothing more than a rough edge, we do this so we may see the effects of lunar libration. Remember what you see… We’ll be back in two days.

And speaking of two, let’s try our hand at Rigel tonight . As you may have noticed for the most part – the brighter the stars are – the closer they are. Not so Rigel! As the seventh brightest star in the sky, it breaks all the “rules” by being an amazing 900 light years away! Can you imagine what an awesome supergiant this white hot star really is? Rigel is actually one of the most luminous stars in our galaxy and if it were as close as Sirius it would be 20% as bright as tonight’s Moon! As an added bonus, most average backyard telescopes can also reveal Rigel’s 6.7 magnitude blue companion star. And if these “two” aren’t enough – note the companion is also a spectroscopic double!

Friday, February 25 – Before the rising Moon interferes tonight, let’s have a go at C/2003 K4 LINEAR. At around magnitude 9, this small comet will be fairly easy to locate telescopically just west of Tau 3 Eridanus.

Let’s return to the Moon tonight to have another look at class 1 crater Langrenus. What a difference! Instead of the bright ring we saw two nights ago, Langrenus is now alive with detail. With the lunar terminator just to its east, we can now see its dual central mountain. Just outside of the crater rim to the northwest, a cluster of three tiny punctuations are revealed – Langrenus F (Bilharz), B (Naonobu) and K (Atwood). Look for tiny crater Acosta just to the north, and Lohse to the south!

Saturday, February 26 – For those living in time zones where 13:00 UT (5:00 a.m. PST) presents you with an opportunity to look at the moon, the libration will now be correct for Mare Oriental. Return to the Cordillera Mountains south of Grimaldi and see if the extra 5.7 degrees of shift reveals the dark edge of this seldom seen area!

Tonight Atlas and Hercules will steal the lunar show to the north, but let’s head to the south and identify class crater Rheita on the terminator. Although the crater itself is not terribly impressive, look closely at its west rim. You will pick up on a very noticeable black streak with a bright edge to the east. This is the Rheita Valley, and much older than the crater which bears its name! It curves slightly south-east towards the terminator and it is believed to be a chain of craters which have merged ending in larger crater Young.

Sunday, February 27 – Heads up for Southern Australia! The Moon will occult Jupiter for you on this universal date. Please check IOTA for the viewing area and universal timing. We wish all of you clear skies for this awesome event!!

If the Sun is shining today in the northern hemisphere, have a look at your “marker” that we picked at solstice. You’ll see its shadow is one-third shorter!

And for those in the north, Comet Machholz is still putting on a wonderful display as it has become a circumpolar object. Before “you know who” decides to light up the night sky, try looking east of Gamma Cepheus. By this time, the “Magnificent Machholz” with be approaching magnitude 6, but it will still be a great object even for small binoculars!

As we visit the Moon again tonight, we will be looking a rather prominent feature south of Mare Nectaris – Piccolomini. In bold black and white relief, you can’t miss this small crater’s striking central peak!

Until next week, remember Saturn and Jupiter also are wonderful things to look at during “moonshine”, and don’t forget double stars! Me? I’m looking forward to dark skies again! Light speed… ~Tammy Plotner