Category: Skywatching

Greetings, Fellow SkyWatchers! Is it hot enough for you where you live? Not if you’re in the southern hemisphere… But this weekend the southern hemisphere is the place to be if you’re interested in catching a total solar eclipse! If you can’t travel that close, then let’s travel far, far away as we take a look at the season’s globular clusters… from easy to challenging! Be sure to keep an eye on Saturn and Mars as they draw closer together and look for bright Jupiter in the morning skies! Whenever you’re ready? Grab your optics and I’ll see you in the backyard…

July 9, 2010 – On this date in 1979, Voyager 2 quietly made its closest approach to Jupiter. How about if we take a close approach before dawn as well? Enjoy the waltz of the Galileans and all the fine details! If you enjoy watching the planets swim against the night sky, then be sure to keep an eye on the early evening visage of Saturn as Mars “back strokes” its way towards the Ring King!

Tonight let’s head on out toward two more close objects that appear differently from the rest (and each other)—same-field binocular pair M10 and M12. Located about half a fist-width west of Beta Ophiuchi, M12 (RA 16 47 14 Dec –01 56 52) is the northern most of this pair. Easily seen as two hazy round spots in binoculars, let’s go to the telescope to find out what makes M12 tick.

Since this large globular is much more loosely concentrated, smaller scopes will begin to resolve individual stars from this 24,000-light-year-distant Class IX cluster. Note that there is a slight concentration toward the core region, but for the most part the cluster appears fairly even. Large instruments will resolve out individual chains and knots of stars.

Now let’s drop about 3.5 degrees southeast and check out Class VII M10 (RA 16 57 08 Dec –04 05 57). What a difference in structure! Although they seem to be close together and similar in size, the pair is actually separated by some 2,000 light-years. M10 is a much more concentrated globular, showing a brighter core region to even the most modest of instruments. This compression of stars is what differentiates one type of globular cluster from another and is the basis of their classification. M10 appears brighter, not because of this compression but because it is about 2,000 light-years closer than M12.

July 10, 2010 – Today we celebrate the 1832 birth on this date of Alvan Graham Clark. An astronomer himself, Clark was also a member of a famous American family of telescope makers. He helped to create the largest refractor in the world—the lenses for the 40″ Yerkes Telescope. Perhaps the stress of worrying for their safety took its toll on Alvan, for he died shortly after their first use. Tonight let’s honor Clark’s work by studying a globular cluster suitable for all optics, M4. All you have to know is Antares!

Just slightly more than a degree west (RA 16 23 35 Dec –26 31 31), this major 5th magnitude Class IX globular cluster can even be spotted unaided from a dark location. In 1746 Philippe Loys de Cheseaux happened upon this 7,200-light-year-distant beauty, one of the nearest to us. It was also included in Lacaille’s catalog as object I.9 and in Messier’s in 1764. Much to Charles’s credit, he was the first to resolve it!

As one of the loosest, or most ‘‘open,’’ globular clusters, M4 would be tremendous if we were not looking at it through a heavy cloud of interstellar dust. To binoculars, it is easy to pick out a very round, diffuse patch, yet it will begin to resolve with even a small telescope. Large telescopes will also easily see a central ‘‘bar’’ of stellar concentration across M4’s core region, which was first noted by Herschel. As an object of scientific study, in 1987, the first millisecond pulsar was discovered within M4, which turned out to be ten times faster than the Crab Nebula pulsar. Photographed by the Hubble Space Telescope in 1995, M4 was found to contain white dwarf stars—the oldest in our galaxy—with a planet orbiting one of them! A little more than twice the size of Jupiter, this planet is believed to be as old as the cluster itself. At 13 billion years, it would be three times the age of the Solar System!

July 11, 2010 – Today marks the 1732 birth on this date of Joseph Jerome Le Francais de Lalande, who determined the Moon’s parallax and published a comprehensive star catalog in 1801. While we might not be determining the Moon’s parallax against the background stars, we’re certainly going to see its effects against the background Sun! Right now the southern hemisphere is the place to be if you’re interested in catching a total solar eclipse – but this eclipse isn’t going to be an easy one to observe unless you’re on the water.

Starting roughly 2000 kilometers northeast of New Zealand at 18:15 UT, totality will begin at local sunrise over the ocean. Minutes later the shadow pass will actually cross land as it encounters the island of Mangaia for about 3 minutes total time. Totality will brush by Tahiti, encompass the uninhabited atolls of the Tuamotu Archipelago and slide its way across the mysterious Easter Island. The Moon’s shadow will take once again to the water for another 3700 kilometers where it will reach its end at the very southernmost tip of South America. For those of you who have the great fortune to eclipse chase? We wish you the very best of skies and luck!

For hard-core observers, tonight’s globular cluster study will require at least a mid-aperture telescope, because we’re staying up a bit later to go for a same-low-power-field pair—NGC 6522 (RA 18 03 34 Dec –30 02 02) and NGC 6528 (RA 18 04 49 Dec –30 03 20). You will find them easily at low power just a breath northwest of Gamma Sagittarii, better known as Al Nasl, the tip of the ‘‘teapot’s’’ spout. Once located, switch to higher power to keep the light of Gamma out of the field, and let’s do some study.

The brighter, and slightly larger, of the pair to the northeast is Class VI NGC 6522. Note its level of concentration compared to the Class V NGC 6528. Both are located around 2,000 light years away from the galactic center and are seen through a very special area of the sky known as ‘‘Baade’s Window’’—one of the few areas toward our galaxy’s core region not obscured by dark dust.

Although each is similar in concentration, distance, etc., NGC 6522 has a slight amount of resolution toward its edges, while NGC 6528 appears more random. Although both NGC 6522 and NGC 6528 were discovered by Herschel on July 24, 1784, and both are the same distance from the galactic core, they are very different. NGC 6522 has an intermediate metallicity. At its core, the red giants have been depleted, or stripped tidally by evolving into blue stragglers. It is possible that core collapse has already occurred. NGC 6528, however, contains one of the highest metal contents of any known globular cluster collected in its bulging core!

Until next time? Keep reaching for the stars!

This week’s awesome images are: M10, M12, M4, NGC 6522 and NGC 6528 from Palomar Observatory, courtesy of Caltech. Alvan Clark historical image and eclipse information courtesy of NASA. We thank you so much!

Greetings, fellow SkyWatchers! If you’re a die-hard amateur astronomer, then you’ll recognize this as one of the prime times to undergo the rigorous “Messier Marathon” – an all night race to see how many Messier objects you can capture! If you need a bit of assistance, be sure to visit the Guide To Space section of Universe Today where you’ll find plenty of information to help you along with your quest. If you’re into a more quiet weekend, then come along as we discover some galactic star clusters that are a little bit more off the beaten path. Whenever you’re ready, I’ll see you in the backyard…

March 12, 2010 – Today let’s celebrate three births! First comes Simon Newcomb. Born on this date in 1835, Newcomb was a Canadian–American astronomer who was really good with numbers. We have him to thank for ephemerides, those great tables of computed places of celestial bodies over long periods of time. Next is 1824 and Gustav Robert Kirchhoff, a physicist who established the theory of spectral analysis. Kirchhoff’s rule states: ‘‘When light passes through a gas, the gas absorbs the wavelengths it would emit if heated.’’ Kirchhoff was very knowledgeable in the field of electricity as well. In 1845, he proved current would flow at the speed of light in a zero resistance conductor. Last is Dorrit Hoffleit (b. 1906), the author of the Yale Bright Star Catalog. Dorrit enjoyed an 80-year career in astronomy and was one of the last living links to Annie Jump Cannon and the senior women’s astrophysics team at Harvard. In her 100-year life, Hoffleit certainly saw a lot of advances in astronomy!

While this is traditionally a “Messier Marathon Weekend”, tonight we’ll break with tradition and locate 6 Canis Minoris about three finger-widths northwest of Procyon. This normal K-type orange giant is around 560 light-years away from Earth, but aim a telescope its way for an opportunity to study an overlooked open cluster—Dolidze 26 (RA 07 30 06 Dec +11 54 00).

In the eyepiece, you’ll find a faint collection of stars that aren’t related to 6 Canis Minoris. Clusters of this type aren’t highly studied yet, but they belong to a group near in age and population and sharing similar star formation processes. Unlike other open clusters, these odd collections contain peculiar stars that produce very high velocity stellar winds and steady X-ray emission. Although it might not be as splashy as a Messier object, Dolidze 26 may very well accelerate cosmic ray particles!

March 13, 2010 – Today note the 1886 birth of Albert William Stevens, a daring balloonist who took the Explorer II to an altitude of 72,395 feet. He took the first photo showing Earth’s curvature and the first solar eclipse photo of the Moon’s shadow on Earth. Also, salute the 1855 birth on this date of Percival Lowell, who predicted the existence of Pluto (but Clyde Tombaugh was the one who actually discovered it, on Lowell’s 75th birthday!). Sir Percival was a determined soul who spent his life trying to find proof of life on Mars. He founded Lowell Observatory in 1894, where he studied Mars intensively, drawing the Red Planet covered with canals and oases. As Lowell once said: ‘‘Imagination is as vital to any advance in science as learning and precision are essential for starting points.’’

Tonight we’ll look at a bright collection of stars located less than a handspan west of Procyon. Its name is Collinder 106 (RA 06 37 19 Dec +05 57 55).

At a combined magnitude of 4.5, this expansive open cluster can be spotted as a hazy patch with the unaided eye and comes to full resolution with binoculars. It contains only around 14 members, but this widely scattered galactic collection has helped scientists determine size scales and dispersion among groups of its type. Viewed telescopically at low power, the observer will find it rich in background stars and a true delight in a low power, wide field eyepiece. If you’d like a challenge, hop a half degree to the northeast to spot Collinder 111 (RA 06 38 42 Dec +06 54 00). While visually only about one-tenth the apparent size of its larger southwestern neighbor, spare little Collinder 111 also belongs to the same class of open clusters. Who knows what may lurk around these understudied clusters?

March 14, 2010 – Celebrate today’s famous astro births, starting with astronaut Frank Borman (b. 1928), a crew member of Apollo 8, the first manned flight around the Moon. Next, astronaut Eugene Cernan (b. 1934), who floated in space for more than 2 hours during the Gemini 9 mission and piloted Apollo 10. How about Giovanni Schiaparelli (1835), the Italian astronomer who described Mars’s ‘‘canali’’ and named its ‘‘seas’’ and ‘‘continents.’’ Schiaparelli’s comet studies demonstrated that meteoroid swarms existed in the path of cometary orbits, and thus predicted annual meteor showers. He was first to suggest that Mercury and Venus rotate and discovered the asteroid Hesperia. Still not enough? Then wish a happy birthday to Albert Einstein (b. 1879), the German–American physicist considered the most brilliant intellect in human history!

For a moment let’s reflect on Einstein’s Cross, proof of his genius. We can’t observe this Pegasus based gravitational lens right now, but we can try to understand Einstein’s theory of gravity as an effect of the curvature in space–time. For example, if you draw a line around the center of a ball, the line would be straight, eventually coming back to its point of origin. We don’t see the point until we reach it, but we know it’s there. Einstein knew this dimension existed and predicted any object with mass will bend space and time around it, just like our line around the ball. He predicted light would also follow a curved path around an object. . .such as a distant quasar located behind a closer galaxy!

Tonight’s object is a ‘‘cross’’ of stars that we’ll dub “Einstein’s Asterism”. Begin at Procyon and shift about 10 degrees southwest (or 2 degrees south of 18 Monocerotis) to locate this pretty grouping of stars. Yes it’s true. It’s just an unknown, undocumented, and unnamed asterism, but how fitting to honor all these famous astro figures and a brilliant man who once said: ‘‘The fairest thing in life we can experience is the mysterious. It. . .stands at the cradle of true art and true science.’’

Until next week, best of luck and clear skies to our marathoning friends!

This week’s awesome images are a historical collection of famous astronomers, “Einstein’s Cross” as imaged by the HST and provided by NASA, and all the great cluster images as done by Palomar Observatory, courtesy of Caltech. We thank you so much!