The southern circumpolar region
By PAUL DERRICK
In the northern hemisphere we have a section of the night sky we call the Circumpolar Region consisting of those stars and constellations that never dip below the northern horizon as they circle the north celestial pole (and Polaris) each day. We should call it the North Circumpolar Region since the southern hemisphere has a comparable South Circumpolar Region consisting of the stars and constellations that never dip below the southern horizon as they circle the south celestial pole.
And it is those stars, constellations, and other night sky objects of the South Circumpolar Region that we in the U.S. can’t see from our mid-northern latitudes, as they never rise above our horizon. Getting to see these hidden jewels is why we northern stargazers get excited about viewing below the equator in places like New Zealand. In a recent column, we cited some of these, like the Southern Cross constellation, stars Alpha and Beta Centauri, Canopus, and Achernar, and the Eta Carina Nebula.
The South Circumpolar Region is also home to two small galaxies known as the Large and Small Magellanic Clouds. Although the explorer Ferdinand Magellan gets credit for “discovering” them in 1519, they were, of course, undoubtedly known to southern hemisphere natives long before the 16th century. But since neither they nor Magellan knew about galaxies at that time, the Europeans called them clouds and named them for Magellan.
The LMC and SMC are each composed of millions of stars and are believed to be companion galaxies gravitationally bound to our much larger Milky Way Galaxy. Whereas the Milky Way is 100,000 light years in diameter, the LMC is 33,000 light years and the SMC 20,000 light years in diameter. The LMC is 163,000 light years away and the SMC 196,000 light years distant – quite close compared to the Andromeda Galaxy’s distance of 2+ million light years.
Easily visible to the naked eye under dark skies, they appear like cosmic clouds, hence their names. Being galaxies, it’s not surprising that they look like someone took two patches out of the Milky Way and placed them some distance away. The LMC spans some five degrees with the SMC half that size. (Your fist held at arm’s length is about 10 degrees wide.)
Ironically, the Southern Circumpolar Region, which we never see, is always visible to most residents of the southern hemisphere all night and throughout the entire year, just as the Northern Circumpolar Region is always visible to us. And while in New Zealand, I was reminded by fellow stargazer Gary Roberts, who has lived in New Zealand all his life, that they never see the stars, constellations, and other night sky objects in the North Circumpolar Region. He lamented that has never seen the Big Dipper, Cassiopeia, Polaris, or even the Andromeda Galaxy.
* April 12 is the 51st anniversary of Yuri Gagarin’s 1961 historic 108-minute orbital flight around Earth – the first for humankind.
* April 21 is the 50th anniversary of the 1962 landing of Ranger 4, the first American spacecraft on the Moon. Intended to soft-land scientific instruments on the lunar surface, a malfunction caused the craft to crash-land, but even that was progress as previous attempts had missed the Moon entirely.
* Apr. 25, 1990, the 8-foot (in diameter) Hubble Space Telescope was deployed by Discovery space shuttle astronauts, but the almost-immediate discovery of defective optics was met with bitter disappointment. Thanks to some ingenious scientists, engineers, and astronauts, corrective optics were installed in 1993, and to this day astronomers are using HST to make remarkable discoveries. And its thousands of images of our cosmos continue to dazzle us like no other scientific instrument.
It’s now only 12 years until the Apr. 8, 2024, total solar eclipse passes over the U.S. from Texas to Maine.
Evenings: Jupiter, Venus, Mars, Saturn
Mornings: Mercury, Saturn
* Mercury, low in the east all month, is at its best during mid-month.
* Venus, the dominating “evening star” in the west, still sets nearly four hours after the Sun.
* Mars is up most of the night, setting just before dawn.
* Jupiter, low the west in the early evening, starts getting lost in the setting Sun by month’s end.
* Saturn, up by 9 p.m., is in the southwest by morning.
Night sky events
** Apr. 2 Mon. and 3 Tue. evenings: Venus grazes the beautiful Pleiades star cluster (AKA the Seven Sisters) and should create a beautiful sight with naked eyes and through binoculars.
3 Tue. evening: The bright waxing gibbous Moon is 10 degrees below Mars.
6 Fri.: The full Moon, called the Egg Moon, Grass Moon, and Easter Moon, is immediately to the right of Spica (nearest) and Saturn, although the Moon’s glare will make seeing them challenging.
13 Fri.: Friday the 13th, considered unlucky by the superstitious, comes around for the second of three 2012 occurrences, the last time coming in July.
11 – 16 Wed. – Mon. evenings: Venus passes within 10 degrees to the right of the star Aldebaran and the V-shaped Hyades star cluster.
13 Fri. morning: The Moon is at 3rd quarter.
15 Sun.: Mars, having moved back to within 4 degrees of Regulus, resumes direct (eastward) motion (as seen against the background stars) and will again begin moving away from the star.
15 Sun. all night: Saturn is at opposition – rising in the east at sunset and setting in the west at sunrise – and is at its nearest, brightest, and largest-appearing for the year.
18 Wed. morning: Mercury is at greatest elongation 27 degrees west of the rising Sun. The crescent Moon is less than a fist-width (7 degrees) above the tiny planet, and the next morning an even thinner crescent Moon is one fist-width to the left – very low in the east as dawn breaks. Binoculars will help.
21 Sat.: The Moon is new.
22 Sun. morning: Lyrid meteor shower peaks with no Moon interference this year.
22 Sun. early evening: The thin crescent Moon is 4 degrees above Jupiter near the west northwestern horizon at dusk.
23 Mon. early evening: The crescent Moon is in Taurus with the Pleiades star cluster 6 degrees to its lower right and the star Aldebaran 8 degrees to its upper left – all near the west northwestern horizon as the evening sky darkens.
24 Tue. early evening: Tonight the crescent Moon is now 7 degrees above Aldebaran with Venus 6 degrees to the Moon’s upper right.
29 Sun. evening: The Moon is at 1st quarter.
30 Mon. evening: “Evening star” Venus is at its brightest at magnitude -4.5; other than fleeting events like fireball meteors, only the Sun and Moon outshine Venus.
30 Mon. evening: Reddish Mars (left), the Moon (below), and the star Regulus (upper right) form a triangle high in the SSW.
* * *
Paul Derrick is an amateur astronomer who lives in Waco. His website (www.stargazerpaul.com) contains an archive of past Stargazer columns, a schedule of his upcoming programs, star parties and classes, and other basic stargazing information. Contact him at: email@example.com, or 254-723-6346, or 918 N. 30th St., Waco, TX 76707.
Story filed under: Big Bend Blog