April Night Sky Wonders

We could call April ‘The month of the Hairy Beasts’ as we’ll encounter more than a few as we leapfrog across the constellations over the next few weeks! And will you see a galaxy-sized monster rearing up out of the darkness somewhere in space? Well as there’s only one way to find out, why not put a coat on some evening this month and turn your eyes towards the heavens for a few minutes?

Look for the profile of a ‘sphinx-like’ star formation to locate the constellation of the Great Lion.
(image credit: Wikimedia Commons)

Mid-month, dead centre in the south at 10pm we’ll see the “Lion’s Heart”, Cor Leonis, (also called Regulus) and the brightest star in the constellation of Hercules’ bane that is the dreaded lion sent from the Moon, Leo. Directly above it and not far from the zenith we’ll also be able to see the Great Bear’s distinctive star pattern. Between the Great Lion’s sphinx-like head and the hind paws of Ursa Major we can look for our first constellation. Once accustomed to the dark your eyes may be able to pick out a small collection of stars that, connected up in our mind’s eye perhaps looks more like a simplistic stick figure mouse than anything else.

Although according to myth this creature’s timid behaviour may have revealed a somewhat ‘mouse-like’ nature, its physical form ought instead to strike terror into any surrounding constellation wildlife because this is in fact the star pattern of Leo Minor the Little Lion or lioness! While its stars are easily outshone by those of its neighbouring constellations Leo Minor contains stars that on a clear night are certainly visible to the naked eye. Praecipua, or “excellent one” as named by Hevelius is an orange giant and the brightest star in the pattern with an apparent magnitude of 3.8, the second brightest, or ‘Beta’ star has a magnitude of 4.4, and 21 Leonis Minoris, the star coming in at third place in terms of radiance has an apparent magnitude of 4.5. So in this star pattern’s dot-to-dot mouse-like form the brightest star is its nose, the second brightest its ear, the third the start of its tail, and the fourth the tip of its tail.

Hanny’s Voorwerp underneath galaxy IC 2497: Cosmic dragon in suspended animation or celestial enigma variation? Although seen with a ghostly bluish hue, Hanny’s Voorwerp has been “corrected” in post-production to its would-be reptilian greenish pallor.
(Image credit: NASA, ESA, W. Keel (University of Alabama), and the Galaxy Zoo Team)

Although this constellation is ‘minor’ in many aspects it does have one unique feature that no other star pattern can boast. If you are interested in seeing great star cities in space then look to the celestial king and queen of the beasts, for in space Leo and Leo Minor certainly contain the lion’s share of galaxies. However beneath one of the lioness’ beautiful spiral galaxies, IC 2497 by name, something considerably less pretty appears to be lurking. First discovered by amateur astronomer Hanny Van Arkel participating in the Galaxy Zoo project in 2007, the disturbing and mysterious Milky Way-sized form has so baffled astronomers that they’ve named it in part after its first observer and for the rest, simply called it “the object”, or in Dutch, Hanny’s ‘Voorwerp’. With a maw-like hole 16 000 light years in diameter, a burning yellow eye and amber horns, Hanny’s Voorwerp resembles the head of a giant space lizard emerging from the cold void of space.

WARNING, SPOILER: While NASA don’t appear to believe that the Voorwerp is actually some enormous space monster coming to feed on an unsuspecting spiral galaxy, their no less interesting hypothesis explains the creation of the galactic spotlight that is illuminating the top of this large intergalactic cloud and possible former mass of ‘galactic vomit’.
(Image credit: NASA, ESA, and A. Feild (STScl))

Previously recognised by astronomers as the tuft of Leo’s tail, this tiny asterism featured so prominently in a constellation tale that it underwent celestial emancipation from Leo, was renamed Coma Berenice and listed as one of the 88 constellations. Since Leo is standing in the heavens facing to the right, this star pattern’s territory is evidently the territory of space immediately to his left. This constellation takes its name somewhat unusually from a non-fictional character, Queen Berenice II of Egypt in 243BC. The intriguing tale that alludes to her hair follows the tragic slaying of the king’s sister by the Seleucids. Although very proud of her long blonde hair the king’s wife was so concerned for her husband’s safe return from his avenging mission that she vowed to sacrifice her golden tresses to the goddess Aphrodite if she ensured his safe return. When King Ptolemy III Euergetes returned to his kingdom unscathed his wife fulfilled her side of the bargain by leaving her locks in the goddess’s temple. However when the queen’s beautiful offering was discovered to have mysteriously disappeared during the night, the king was outraged. In an attempt to appease his wrath, Conon the court astronomer pointed to a cluster of stars and suggested that Aphrodite had approved of Queen Berenice’s offering so much that the goddess had placed it in the heavens.

Like Leo Minor this constellation has few really bright stars. Its second brightest star called the “Diadem” however is a great cosmic example of two heads are better than one, as this binary system’s individual components are only-just-visible 5^th magnitude stars, but looking like only one stellar object to naked eye observers on Earth their combined star power improves Alpha Comae Berenices’ radiance to an apparent magnitude of 4.3. If you can get hold of a small telescope or good pair of binoculars a beautiful object worth looking out for in this right-angle-shaped star pattern’s patch of sky is the Needle Galaxy. Despite being conveniently angled to Earth so that all we see is the edge of the galaxy’s pancake-like shape, this particular stellar structure located 30 to 50 million light years away has earned the title “needle” as it is one of the flattest of its kind known.

Just so we don’t get stiff where we’re standing, let’s change our stance and orientate ourselves to look in the direction of northeast (a little left of where the Sun rises in the morning). Sometimes we can quite accurately predict the future by looking to the past. This is true when it comes to anticipating meteor showers. By careful observations of the skies over the centuries astronomers now know more or less exactly where to look, what to expect, and when to expect it. It is for this reason we can be fairly certain that this month should not fail to delight us with those brief and silent celestial beauties of the night sky, the Lyrids.

Where to look: Leo Minor, Coma Berenices, and Lyra constellations on the 21st April. (CLICK TO ENLARGE)
(Image credit: Nick Parke/Stellarium)

If however you are still finding yourself more than a little baffled at why year in, year out, meteor showers seem to reoccur with the regularity of clockwork and are only associated with certain months in particular, the answer can be found if, in our mind’s eye, we step back from Earth into space and briefly consider the inner workings of the Solar System. One analogy for meteor showers is a child on a playpark merry-go-round passing through a swarm of midges on each time around. If the child were to represent Earth orbiting around the Sun and we could imagine the swarm of midges magically glowing like fireflies every time the child goes through the swarm, then this is not unlike the transformation that formerly non-luminous meteoroids and comet debris undergoes when our planet glides through comet trails. Earth’s gravitational pull does the rest of the work and the meteoroids acquire meteors (fiery tails) behind them as they burn their way through Earth’s atmosphere. Although one of the more modest meteor showers in our astronomical calendar, the Lyrids, which peak on the 21^st of April, could rain down 15 to 20 shooting stars per hour from Lyra’s constellation “radiant”. Lyra the harp’s celestial domain should be right in front of us and easily located low on the horizon beneath its brightest star, Vega.

Also this month in the southeast Saturn will continue to rise to a more conspicuous position from 11pm, moving up from the horizon to the left of Virgo and taking the guise to naked-eye observers of a bright golden star. While the chances may be slim, it is perhaps now just within the bounds of possibility that an observer armed with a large telescope in their back yard could stumble upon the smallest “Saturn-wannabe” ever discovered. Having just moved beyond the yellow gas giant, the 17^th magnitude half-asteroid-half-comet (or “centaur”) Chariklo that is less than one-thousandth Saturn’s diameter and surrounded by two rings 7km and 3km wide respectively, is now the smallest Solar System body ever discovered to have rings.

So as you look forward to the sights of the April night sky, happy hunting and enjoy the celestial star show put on just for you!

(Article by Nick Parke, Education Support Officer)