Star Clusters and Stars

M45, the Pleiades - January 2017 issue of Sky & Telescope magazine, Pleiades, Rising Thro' the Mellow Shade - Seeing the Pleiades Bubble

"Although this is the same drawing of the Pleiades as shown in the Nebulae section, I'm posting it here as well to focus on just the star cluster.

The constituent stars of the Pleiades open cluster are 115 million years old so have burned through their original gas and dust. The nebulosity we see around the stars today comes from an independent cloud of interstellar dust passing through the region by chance. So that means all the reflection nebulosity associated with the Pleiades is part of the IFN, and that includes the Merope, Alcyone, Electra and Maia nebulae. Ignoring the nebulosity leaves us with a stunning galactic cluster that's as much fun to observe with a telescope, binoculars or the naked eye.

A wide field instrument is needed to for the best optically aided view of the cluster so the stars are seen in context with their stellar surroundings. The most accessible instruments are short focus refractors and binoculars, but a short focus Newtonian can provide a stunning view as well."

M45, the Pleiades naked eye sketch - January 2017 issue of Sky & Telescope magazine, Pleiades, Rising Thro' the Mellow Shade - Seeing the Pleiades Bubble

"It’s possible to see more than the 6 brightest stars even under a relatively bright sky. The nine brightest stars in the Pleiades range from magnitude 2.86 to 5.64, and are visible if you take the time to look. Patience will be rewarded. Making a quick sketch is an easy way to keep track of what you’ve seen. Averted vision is useful but can be imprecise when pinpointing the exact location of the fainter stars even if you’re careful.

This sketch shows my best naked eye count of Pleiads (twelve) which was made on a night of exceptionally steady seeing in the Oregon Coast Range mountains. The circled star with a question mark is actually a positive observation - it's the star I plotted below and to the right of Electra that's not real. 

Some observers have seen fourteen Pleiads. Former Sky & Telescope columnist Walter Scott Houston’s logged a total of eighteen, and Mel Bartels has seen twenty!"

M5,  with V42 and V84 at their maximum brightness - June 2014 issue of Sky & Telescope magazine, M5 Surprise

"Have you seen the two Cepheids in M5 lately?” asked Tom. “They’re both near maximum brightness.”

Caught completely by surprise, I could only stammer, “What? Cepheids in M5? I’ve never heard of such a thing!”

“Sure!” said Tom, “Come have a look in my scope. They stand out best during twilight like this.”

This was, more or less, how Tom Osypowski introduced me to V42 and V84, M5’s two Type II Cepheid variables, at the 2013 Golden State Star Party. It seemed that none of the other observers nearby had heard about M5’s Cepheids either, making Tom the only person there who knew about this surprising sight. So I looked in Tom’s 20-inch scope and immediately noticed two rather bright stars near M5’s core. Tom confirmed that they were the Cepheids, and I was instantly hooked. The idea of observing the northern sky’s brightest globular cluster (M5 is a hair brighter than M13) and watching its brightest stars change night after night was irresistible.

At their brightest (V42 varies from magnitude 10.5 to 12.1 while V84 varies from 10.8 to 12.3) these are by far the brightest two stars in M5 and change the visual character of the cluster."

M5 - with V42 and V84 at their minimum brightness - June 2014 issue of Sky & Telescope magazine, M5 Surprise

"I watched V42 and V84 go through their full cycles in August of 2013 as well as making as accurate a sketch of M5 as I could. Sketching this beautiful globular cluster was sometimes a tedious exercise in trying to draw dots in correct relation to each other. But as the sketch became a drawing, those dots — stars — had become familiar landmarks. I see these landmarks every time I look at M5 now, as well as in photos.

The process of sketching worked its magic again; seemingly random stars became familiar, because sketching is really just a disciplined way of focusing attention. Without that night by night attention I would never have come to appreciate M5’s dynamic nature. Following the slow variations of V42 and V84 breathed a new kind of life into what I’d previously considered a beautiful but staid ball of stars, and provided a glimpse of the great globular’s ever changing, 13 billion year old pulse."

M5, with Cepheid's V42 and V84 circled - June 2014 issue of Sky & Telescope magazine, M5 Surprise

"V84 is the circled star below, and just outside the main body of M5, and V42 is the circled star to the lower right of the main cluster. The lines connect them to nearby reference stars, and the two sets of connected stars in the upper left quadrant of the drawing are reference stars that helped me visually orient the cluster. The circle in the main body of the cluster is the location of a group of the brightest stars near the center of M5."

M7 - June 2023 issue of Sky & Telescope magazine , The Many Delights of Messier 7

"There are other naked eye open clusters in the sky – heck, M6 is just a few degrees to the northwest – so that’s not what makes M7 special. It’s all the extra goodies that do that. M7 is located in a wonderfully rich Milky Way field intertwined with dark nebula, and three other open clusters that overlap or touch its boundaries. There are even three challenging planetary nebulae seen through M7. Perhaps most fascinating of all, there’s an NGC globular cluster on M7’s western boundary. You can spend an entire evening observing just this field of view. "

Above, M7 as seen through an 8-inch f/3.3 Dobsonian. My rendering captures the view through a 25mm eyepiece, producing 2.5-degree field of view and a magnification of 38x, which was supplemented with higher magnifications. The star colors were seen best with the 30-inch and its silver coated primary mirror at 95x. This sketch was built up at the eyepiece over six nights during the summer of 2022 while M7 was between 14 to 7 degrees above the southern horizon. Sky Quality Meter (SQM) readings between 21.67 and 21.76 during this time. North is up.

Above, this annotated version of my original pencil sketch shows how crowded this field of view is with deep sky objects. 

Barnard's Star - May 2024 issue of Sky & Telescope magazine, Tracking Barnard's Star

"Barnard’s Star is the fourth-closest star to our Sun and has a proper motion of 10.4″ per year — this makes it the (currently known) fastest-moving star in the sky. Over six years (or, more accurately, 5.96 years, the most precise estimate we have of its distance), this amounts to a bit more than one arcminute, which is greater than the apparent diameter of Jupiter. Combined with the star’s accessible visual magnitude of 9.5, this opens up the possibility of tracking its motion across the sky with a small telescope.

My first sighting of Barnard’s Star was in 1983, and since then I’ve noted its position six more times. These sightings form a set of visual observations that have become priceless to me."

"Barnard’s Star is located about ¾° northwest of 4.8-magnitude 66 Ophiuchi, and it’s well-placed for most of the spring, summer, and autumn in a distinctive part of northeastern Ophiuchus. It’s variable and hence is also designated V2500 Ophiuchi. Its variability is attributed to infrequent flares — in fact, old M dwarfs, such as Barnard’s Star, don’t undergo regular flaring activity, so it was a surprise when it erupted in the late 1990s. During that episode, the star brightened by half a magnitude."

"Barnard’s Star rotates once every 145 days or so, which is typical for a red dwarf of its age of 7 to 10 billion years. At only 16% of the Sun’s mass and 18% of its radius, it occupies a spot on the lower end of the main sequence, where it will stay for several trillion years. Along with its two-dimensional proper motion, it’s also moving toward us — and in about 9,800 years will be only 3.75 light-years away."

"I noted the position of Barnard’s Star each time I observed it from 1983 to 2023 on the chart on page 1,252 in Volume Two of Burnham’s Celestial Handbook — this adds up to a running total of 6.90′ of proper motion. The small flying-geese asterism appears just right of center, pointing at the 1960 location."

A nifty animated gif showing Barnard's Star motion from 2007 and 2017 can be seen here.