Welcome to the Ontario Parks “Eyes on the Skies” series. This space (<– see what we did there?) will cover a wide range of astronomy topics with a focus on what can be seen from the pristine skies found in our provincial parks.
For those of us in Ontario, April is that transition month between winter and spring weather. The snows start to melt away, the lakes start to open up and, by month’s end, the first buds may appear on the trees. Because of Daylight Savings Time, we now have later sunsets and sunrises, and more time to enjoy the activities of the day.
Here are our astronomical highlights for April, 2017:
April’s phases of the moon occur as follows:
- First quarter on April 2
- Waxing gibbous on April 5
- Full moon on April 11
- Waning gibbous on April 13
- Last quarter on April 18
- New moon on April 25
- Waxing crescent on April 28
Venus has dropped out of sight for evening viewers and is now only visible in the morning sky (albeit not for a few weeks into April). Mercury, however, is prominent at the beginning of the month before it too drops below the western horizon at sunset.
Like Venus, Mercury goes through phases as it orbits the sun. Also, like Venus, Mercury can be sighted in the evening sky and sometimes in the morning sky but never is visible too far away from the sun.
Unlike Venus, however, Mercury has practically no atmosphere and it has a very strange rotation rate. Mercury is in what is known as a tidal resonance with the sun; Mercury rotates three times for every two orbits around the sun. As a result of this peculiar behavior, there are times in which the sun appears to never move as viewed from the surface of Mercury.
Mercury, the closest planet to the sun, is never very far away from the sun. As a result, viewing Mercury is quite challenging (even though it is actually one of the brightest planets). The best way to view Mercury is to watch for it when it is far from the sun (such as April 1) and to ensure that you have a great western horizon such as from the Agawa Bay Campgrounds at Lake Superior Provincial Park.
Featured constellations: the Bears and a Dragon
In last month’s blog, we discussed some of the constellations that are prominent in the spring: Leo the Lion, Cancer the Crab and Coma Berenices (Queen Berenice of Egypt’s hair). This month, we will focus on two of the most well-known, as well as one of the longest, constellations visible in the night sky: Ursa Major, the Great Bear (Big Dipper) and Ursa Minor, the Little Bear (Little Dipper).
The Big Dipper (Ursa Major)
Though many people know it simply as “the Big Dipper” (think: ladle), this constellation is typically associated with bears.
According to the Haudenosaunee tradition, the four stars of the rectangle form the shape of a bear, while the other three stars represent three hunters actively engaged in the hunt. The first hunter, closest to the bear, is Robin (a completely black-coloured bird). The next star/hunter is Chickadee, and the farthest hunter/star from the bear is Moosebird.
The trio pursue the bear from spring to fall, with the bear constantly outpacing the hunters. However, in the fall the tired bear stops and stands to fight the hunters. At this point, Robin shoots an arrow at the bear and wounds it. The blood from the bear falls onto the trees, explaining why they change colour in the fall. Likewise, the bear’s blood also completely covers Robin. While Robin does his best to shake the blood off, a red streak remains down his midsection permanently, explaining why robins today have red breasts.
Classical mythology also sees this constellation as a bear, accounting for the name Ursa Major or “Great Bear.” The story of Ursa Major comes from the story of Callisto and Arcus. Callisto was transformed into a bear by Zeus’ jealous wife Hera, and was about to be killed by her son Arcus, who did not recognize his mother in bear form. Just as he was about to spear Callisto, Zeus took pity on the situation and transformed both mother and son into two constellations: “Ursa Major” (Great Bear) and “Ursa Minor” (Little Bear).
In our light-polluted skies, it is difficult to see all of the faint stars that make up the body of the Great Bear. However, we can see the enormous tail and midsection of the bear forming what we know as the “Big Dipper.” It is amusing to note that the most prominent feature of the Great Bear – its long tail – is almost completely absent on the bears wandering our wilderness today.
Finding North from the Big Dipper
Step: 1 – Finding the Big Dipper
To find the Big Dipper, try to find the four stars in a rectangle (that make up the bowl of the dipper / the body of the bear) and then try to find three stars in a gentle triangle towards the bowl’s left (that make up the handle of the dipper).
Step: 2 – Finding the Pointer Stars
Find the two stars of the bowl that are opposite where the handle meets it. These two stars “Dubhe” and “Merak” are known as the “Pointer Stars.”
Step: 3 – Finding Polaris the North Star
Using the distance between the Pointer Stars as a guide and following along their direction to a point about halfway up in the sky, shift your gaze about five times the distance between the pointer stars. You should now be looking at Polaris, the North Star.
Step: 4 – Finding North
Once you have found Polaris, simply follow a line directly to the ground and that will be north. Because these constellations never set from Ontario (they’re always visible, no matter what time of the night or day of the year), you can use this skill to find North with a fairly high degree of accuracy.
Draco the Dragon
The last of the constellations to be discussed for the April edition of “Eyes on the Skies” is the constellation of Draco the Dragon.
In Greek mythology, Draco is the dragon Ladon who is tasked by Hera to guard her apple trees. As one of his 12 labours, Hercules had to bring back some of the apples from the tree and kill the dragon. Today, the constellation of Draco sit prominently amongst the northern stars and the constellation of Hercules (discussed in a future edition) sits by its head.
Thuban (the used-to-be North Star)
One of the brighter stars of Draco – Thuban – lies between the bowl of the Little Dipper and the stars Mizar and Alcor. Because the Earth’s poles slowly move over many thousands of years (we call this procession), Thuban and not Polaris was actually the North Star between about 4000 to 2000 BC. Many of the Egyptian pyramids were aligned in such a way whereby a passageway was aligned to Thuban, the North Star!
The Lyrid Meteor Shower
The Lyrid Meteor Shower peaks on the night of April 21/22 with somewhere around several dozen meteors per hour visible in early morning skies. Meteors with this shower seem to originate back to the constellation of Lyra the Harp, which is more prominent during the summer.
Late April Fireballs
When a meteor becomes very bright, brighter than Venus, it is often given the title of fireball!
For reasons still not completely clear to science, there are a large number of fireballs that can be seen in the last week of April. These meteors are not related to the ones coming from Lyra as they are slower, brighter and seem to come from Corvus the Crow (much further south during the spring season). So between the Lyrids and the Late April Fireballs, an observer should have a great final week or two observing the April night skies.
This completes our review of April skies…
Remember to bundle up and enjoy the view from our parks. The stars await those who make the effort to enjoy them!