Sunspots and faculae
The most prominent features on the solar disk are sunspots - dark blots that range from Earth-size motes to large complex regions covering billions of square kilometers. Sunspots are essentially areas where the forces of concentrated magnetic fields inhibit currents of rising hot gas from deep within the Sun. With less hot gas reaching the surface, that part of the Sun is cooler (by about 1,500 kelvins) and thus appears darker. Despite their dark color, sunspots are actually hotter than the...
The Magellanic Clouds
Just 15 and 36 southwest of Canopus, respectively, lie two bar-shaped patches of light that, to the naked eye, look for all appearances like detached pieces of the Milky Way. These clouds are not fragments of our galaxy, but separate, nearby galaxies that astronomers think may be gravitationally bound to our own, like the Moon is to the Earth. They are named the Large and Small Magellanic Clouds, after the Portuguese explorer Ferdinand Magellan, who recorded them in 1519 during his voyage in...
Shooting stars from Orion
If you can't sleep this week, try counting a few shooting stars. There will be a few more of them in the night sky than usual, especially during the wee hours of October 22. Go outside around 2 a.m. and look toward the southeast for faint, fleeting streaks of light among the stars. If you see one streaking out of the asterism forming Orion's upheld club, you'll have spotted an Orionid meteor. The term 'meteor shower' is a misnomer. Meteors don't 'rain' down from the sky, and neither do they...
The Summer Triangle
Go out tonight as dusk settles and look halfway up into the eastern sky. As twilight fades, you should be able to see three bright stars arranged in a large triangle. This venerable star pattern, known to amateur astronomers as the Summer Triangle, has long been the starting place for people wanting to learn the constellations. Highest in the sky around 9 o'clock is Vega, a blue-white star whose name means 'swooping eagle.' Vega is not only the brightest luminary in the Triangle, it is also the...
Fomalhaut solitary star in the south
Late September skies are still rich with summer stars. Just after sunset, the northern Milky Way stretches across the top of the sky, with Deneb, Vega, and Altair huddled around the zenith, and Sagittarius crossing the meridian. In another month, however, these stars will slide off toward the west, and the autumnal constellations will begin taking their place, although without much fanfare from bright stars. There is, however, one notable exception. Low in the southeast around 9 o'clock is a...
The Perseids celestial fireworks
A bright shooting star is one of the most breathtaking sights in the night sky. What makes it all the more delightful is the fact that the observer happened to be looking in the right place at the right time when the unexpected event occurred. Centuries ago, however, a meteoric display was an unwelcome sight, especially to people in power, because in most cases, a meteor was considered an ill omen that reflected on kings and military leaders. SirJames Frazer in his book The Golden Bough tells...
The Beehive Cluster
In the southern part of the Northern Hemisphere this week, spring begins to manifest itself in fields and meadows as wild flowers bloom and tender new buds push out into the sunlight. You may see hummingbirds and bees working the blossoms of morning glories and trumpet vines. How appropriate, then, that near the apex of the night sky this week is a star cluster just visible to the naked eye that goes by the name, the Beehive Cluster. Located in the faint constellation Cancer the Crab, the...
The winter clock
Many people live under the mistaken belief that they cannot learn to recognize constellations. They may recall looking up on some clear summer night in their past and feeling overwhelmed by the thousands of points of light that seem scattered randomly across the sky. But the stars are, in fact, quite easy to learn if you use their constant positions as pointers to other stars and star groups. In the Northern Hemisphere, if you go outside this week around 9 '' 1 '' CANIS MAJOR,-'' 1 The 'winter...
The tides
Fishermen, harbormasters, and coastal dwellers around the world can't help but notice an astronomical phenomenon that affects their region, sometimes dramatically, every day the ebb and flow of the tides. The Earth's daily rotation, along with the Moon's incremental eastward revolution, produces two high tides and two low tides during each 24-hour period. Because the Moon rises approximately 50 minutes later each day, high tides occur about 50 minutes later on successive days, at intervals of...
The Sky by Seasons
December 21 - 27 December 28 - January 3 January 4 - 10 January 11 - 17 January 18 - 24 January 25 - 31 February 1 - 7 February 8 - 14 February 15 - 21 February 22 - 28 (or 29) March 1 - 7 March 8 - 14 March 15 - 21 March 22 - 28 March 29 - April 4 New year,new millennium,same stars 14 The second-brightest star in the night sky 26 Spring arrives 39 Finding true north 42 Finding true south 45 April 5 - 11 April 12 - 18 April 19 - 25 April 26 - May 2 May 3 - 9 May 10 - 16 May 17 - 23 May 24 - 30...
Familiarizing yourself with the night sky
Like our ancestors did thousands of years ago, it's quite natural for us today to view the night sky as an inverted bowl upon which the stars are attached and the Sun, Moon, and planets move. And it requires only a little imagination to further visualize that the inverted bowl of stars is actually the hemisphere of a globe - a celestial sphere - which we see from the inside out. Earth floats freely in space within this sphere, which lies at an immense but arbitrary distance. The sphere revolves...
The smile in the sky and the watery realm
Rising in the southeast this week around 7 o'clock, and well up by 8 30, is a faint wallflower of a constellation, but one that offers a big smile if you can find it. In fact, it is often referred to as the 'smile in the sky' Capricornus the Seagoat. This constellation has come down through the ages unaltered in form. In the ancient star atlases, Capricornus was depicted as a goat with the tail of a fish. The constellation resides in a region once known as 'the Sea.' But more on that later....
The Sun stands still
Summer officially arrives in the Northern Hemisphere this week, in the form of the summer solstice, the instant the Sun reaches its most northerly position for those living north of the equator. In the Southern Hemisphere, meanwhile, the Sun reaches its lowest point in their sky, hence this week marks the beginning of southern winter. On the first day of summer, the Sun is directly overhead at noon for people living at latitude 23.3 N, a region denoted as the Tropic of Cancer. There's nothing...
Stellar nomenclature
At least fifty of the brightest stars have names that are either of Greek or Latin origin (Sirius, Castor, Pollux), or Arabic (Altair, Fomalhaut). Many of the brighter naked-eye stars in the constellations, however, are designated not by name but by small letters of the Greek alphabet. In this system, introduced in 1603 by Johannes Bayer, the brightest star in a constellation generally is labeled Alpha or a, the second-brightest star is Beta or p, and so on down to Omega or ra. (There are...
Bootes the Herdsman
High overhead as darkness falls in the Northern Hemisphere these early summer evenings shines a lone, bright orange-hued star. Just go out and look almost straight up around 9 o'clock you can't miss it. This star is Arcturus, the luminary of the constellation Bootes the Herdsman. If you live in a suburban location, you can probably just make out the constellation's star pattern. It looks like an ice-cream cone with bright Arcturus at the cone's apex and the ice-cream end pointing more or less...
The flashing Dog Star
On a winter's evening, with the snow crunching beneath your boots and your breath hanging in frosty clouds in the air, your eye may catch upon a single star glimmering like a multifaceted diamond through the dark silhouettes of bare trees in the southeast. As you gaze upon this scene, you may imagine a kind of stillness settling upon the world, or perhaps within yourself. At such contemplative times it is hard to tell. But something about 'lone stars' strikes an emotional chord within us all....
Predicting moonrise
Many people get confused when it comes to predicting when and where the Moon will appear in the sky. Unlike the Sun, the Moon doesn't rise and set daily, nor does it appear in the same part of the sky on a nightly basis. Moreover, sometimes it appears in the the evening, while at other times it's in the morning. The Moon just seems all over the sky. Once you learn a few lunar basics, though, it is not difficult to master the comings and goings of our nearest neighbor in space. First, the Moon...
The Pleiades rise at sunset
Just before dawn in early June, a tiny dipper-shaped group of stars in Taurus can be seen shining faintly through the strong twilight. This event is the 'helical rising' of the Pleiades, the cluster's first appearance after coming from behind the Sun. For the rest of the year, the Pleiades rise earlier each day, mounting ever higher in the sky until this week, when they rise as the Sun sets and are in the sky all night. Look toward the east after sunset to see this distinctive nest of stars...
Finding true south
The Northern Hemisphere has the bright North Star as its guiding light to astronomers, navigators, surveyors, and Boy Scouts everywhere. Not so the Southern Hemisphere. The place in the sky toward which Earth's south polar axis points appears virtually starless. Except, that's not exactly true. Sigma (o) Octantis, which can just be seen with the unaided eye in a dark sky, is designated Polaris Australe, the South Pole star. Sigma, which resides in the dim constellation Octans the Octant,...
The seasonal lag
Winter, which usually arrives on or about December 22, never seems to be appropriately on time, no matter where you live. In the southern realms of the Northern Hemisphere, the first day of winter can be quite mild, even tropical, while in the north, cold air has been infiltrating since late September and several inches of snow may already be on the ground. Depending on where you live, you are either surprised that winter has snuck up on you or incensed that someone would make a big deal about...
Three star clusters
Auriga the Charioteer (January 25-31) holds more fascination than just ancient star myths. The pentagonal-shaped figure is home to a trio of bright star clusters that, under certain sky conditions, can be seen with the naked eye. Our galaxy contains hundreds of millions of star clusters, of which we can see mere thousands from Earth. Most star clusters are too faint to be seen without optical aid, but a handful can be glimpsed as misty patches between the stars. Lying in the star-thronged...
Five southern birds
Call it a starry roost or celestial aviary, but this week after sunset, five constellations representing exotic or mythical birds flock around the south celestial pole. Furthest north, and thus visible low on the southern horizon from mid-latitudes in the Northern Hemisphere, are Grus the Crane and Phoenix, the great bird that rose from the ashes of its predecessor. Three other birds lie closer still to the southern pole Tucana the Toucan, Pavo the Peacock, and Apus the Bird of Paradise. Of...
Who was Auriga the Charioteer
With the winter Milky Way mounting high in the sky in late January evenings, it is a good time to locate a bright constellation that represents both a star lore mystery and high mythological drama. I'm speaking of Auriga the Charioteer, a pentagonal figure that resembles either a squatty roofed house or a crude baseball home plate, whichever form you prefer. For people at mid-northern latitudes (30-40 N), Auriga is first seen early December evenings rising just after sunset, following first the...
The secondbrightest star in the night sky
One of nature's more pleasing coincidences is that the two brightest stars in the night sky - Sirius mag - 1.46 and Canopus mag - 0.72 - lie only 35 from one another - that's about three and a half fist-widths held at arm's length. What's not so pleasing, however, is that for many sky-watchers in the Northern Hemisphere Canopus never rises very high in the southern sky. Its peak altitude at latitude 36 N is only about 1 . To see Canopus, you're going to have to travel south. In Dallas latitude...
