October 23 - 29, 2006
SUMMARY:Greetings, fellow SkyWatchers! Join us this week as we journey across the Cosmos on a voyage of discovery. We open with galaxies and bright globular clusters and end the week with the Moon. Grab your binoculars and telescopes and turn an eye to the sky, because....
Here's what's up!
Monday, October 23 - With tonight's dark skies, let's head toward a big scope challenge before the lunacy resumes. Tonight we'll seek out 10.0 magnitude, 5 arc-minute sized galaxy IC 10 in Cassiopeia.
Starting at Beta, shift a degree and a half east. First noted by Lewis Swift in 1889 at the Warner Observatory in Rochester, NY, it wasn't until the 1960s that motion studies confirmed that this dwarf galaxy was a true member of our Local Group.
Tuesday, October 24 - Tonight the slender crescent Moon will offer a real challenge for visual observation low on the western horizon. If you do see it, this delicate sliver will be faintly illuminated by the glow of what was once known as the "da Vinci effect" - but is now called Earthshine. Look for Jupiter and Mercury very nearby.
If you do look to the lunar surface tonight to the extreme north, you could possibly see the beginning of crater Gauss on the edge, or Mare Marginis about one quarter the way along the limb to the south. Perhaps Mare Smythii will show well just north of central, or crater Humboldt will be seen just to the south.
Today in 1851, William Lassell was busy at the eyepiece of his privately-owned 24 inch reflector telescope in Liverpool, England. His discovery was Uranus' moons Ariel and Umbriel. At magnitudes 14.4 and 15.1, this pair is beyond most backyard equipment, but you can give it a try. Have a look at this distant world - now easily found a little less than a degree south-southwest of Lambda Aquarii. Keep in mind that these two natural satellites of Uranus are tougher to spot than Oberon and Titania, not only because they are slightly fainter - but also because they orbit close to the planet.
Tonight the Moon will set well before skydark. Let's have a look at a real "class act" - M75. Start at Beta Capricorni and head southwest about four finger-widths.
This Class I, 8.6 magnitude study was discovered by Pierre Méchain on the night of August 27, 1780. William Herschel went on to resolve this 68,000 light-year distant cluster in 1784. Often described as a fainter version of M3 in Canes Venatici, it has a high intrinsic brightness of magnitude -8.3. M75 and M80 are two of the most highly compressed of all globular studies.
Wednesday, October 25 - And who was watching the planets in 1671? None other than Giovanni Cassini who had just discovered Saturn's moon Iapetus. Early risers can look for this 10th magnitude Saturnian satellite about an hour or so before sunrise.
Today is the birthday of Henry Norris Russell. Born in 1877, Russell was the American leader in establishing the modern field of astrophysics. As the namesake for the American Astronomical Society's highest award (for a lifetime of contributions to the field), Mr. Russell is the "R" in H-R diagrams - a word first used in a 1914 paper.
Tonight on the lunar surface you will see the beginnings of Mare Crisium, a unique feature since it is not connected to any other mare. This highly curved, low reflecting area is about the size of the state of Washington. Further south you will see the emerging and ancient crater Langrenus. Look for equally old crater Petavius about one-third the way north of the southern cusp. Using binoculars see if you can spot crater Vendelinus between the two. This eroded ancient will disappear in the days ahead.
And when the Moon disappears just before skydark, have a look at 8.2 magnitude galaxy M110. It's not hard to find. Just use low power and travel off the Andromeda Galaxy's western edge. This dwarf elliptical satellite galaxy of the Milky Way's Local Group has the combined mass of 10 billion suns and extends some 25,000 light-years on the major axis. Visible in binoculars as a patchy elongation, small scopes require very dark nights and low magnifications to truly appreciate its expansive nature. M110 is to M31 what M43 is to M42 - a superb study in isolation...but made less so by having an extraordinary companion.
Thursday, October 26 - Tonight look again at the lunar surface and how our study craters have changed. Relocate Petavius and power up on its southern edge. If skies are steady you will see a series of confluent craters with dark interiors. At the northern end of this series lies the small, Class 2 punctuation of crater Hase.
When the Moon disappears just before skydark, have a look at 8.2 magnitude dwarf galaxy M32. Just return to the Andromeda galaxy and look along its eastern edge. This satellite has the combined mass of 3 billion suns and is 8,000 light-years in diameter. Visible in binoculars as a faint diffuse star, small scopes will see it much like a small globular cluster, but no matter how much aperture and magnification you give it, this one remains totally unresolved.
Friday, October 27 - Tonight on the lunar surface, let's head well northwest of Mare Crisium for some of the Moon's most impressive craters. Near the terminator is Atlas to the east and Hercules to the west. Note how deep and rugged they appear. As your eye moves back towards Mare Crisium, you will also see another impressive pair, smaller Cepheus and larger Franklin.
When we've finished lunar study, let's track down the two outer planets - Uranus and Neptune - while waiting for the Moon to set. 8.0 magnitude Neptune is now well placed near Iota Capricorni. Uranus is within a degree southwest of Lambda Aquarii. At magnitude 5.8, binoculars should have no trouble revealing it as the second brightest "star" in the field.
Once it gets dark turn your scope toward tiny Delphinus and its two brightest stars - Alpha and Beta. Point your scope at the star northeast - Gamma Delphini - and enjoy the lovely yellow and green pair at the "nose" of this beautiful Celestial Dolphin.
Saturday, October 28 - Today in 1971, Great Britain became the 6th nation to launch a satellite into space.
Tonight let's study lunar features. Along the terminator, the majority of Mare Tranquillitatis will be visible and joined to the north by the beginnings of Mare Serenitatis. Here you will find our first "marker" - the ancient walled plain Posidonius. Inside Serenitatis and running parallel with the terminator are the snake-like lines of Smirnov - a beautiful collection of wrinkled ridges known as "dorsa." To the south look for the "three ringed circus" of craters Theophilus, Cyrillus, and Catharina. Focus on sunlit Mare Nectaris to the southeast. Cutting between Theophilus in the north, and shallow open crater Beaumont in the south is a thin, bright line. Congratulations! You've just spotted an officially "unnamed" lunar feature we can refer to as Dorsum Beaumont. Very cool...
Now turn binoculars towards the cluster-rich region of Cassiopeia. Just for fun, take a blank sheet of paper and make a large "W." As you are sweeping Cassiopeia, jot down some marks where you see stars condense. Then later reference star charts to identify precisely what you've "discovered for yourself!"
Sunday, October 29 - On this night in 1749, Guillaume-Joseph-Hyacinthe-Jean-Baptiste Le Gentil was at the eyepiece of his 18' focal length telescope. His study of choice was the Andromeda Galaxy, which he believed to be a nebula. Little did Le Gentil know at the time, but his descriptive notes also included M32. It was the first small galaxy discovered and another 175 years would pass before such a thing would be recognized by Edwin Hubble as such.
Tonight, all of Mare Tranquillitatis, and the majority of Mare Serenitatis will be revealed just north of the terminator's mid-point. On the northwestern shore of Serenitatis, the eastern portion of the Caucasus Mountains will emerge in the sunlight. Tonight let us again take an historic journey to the southwest edge of Tranquillitatis and visit with the Apollo 11 landing area. Although we can never see the "Eagle" telescopically, we can find where it landed. Tracing the western wall of Tranquillitatis, look for the small circles of craters Sabine and Ritter. Once located, switch to your highest magnification. Look in the smooth sands to the east to see a parallel line of three tiny craters. From west to east, these are Aldrin, Collins, and Armstrong - the only craters to be named for the living. Just south of these three tiny punctuations is where Apollo 11 touched down, forever changing our perception of space exploration.
May all your journeys be at light speed... ~Tammy Plotner.
M75 - Credit: NOAO/AURA/NSF