night sky

Eyes on the skies — July, 2017

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.

July has finally arrived. Summer is the perfect time to escape the noise, air and light pollution of the larger urban areas and head to the peace and serenity of a provincial park.

July also hosts a number of beautiful constellations, full of interesting stories to tell.

Here are our astronomical highlights for July, 2017:

The sun

As described in our January edition, Earth is actually farther from the sun during the summer than during the winter, with July 3 being the day that we are farthest away. The small difference in distance is more than made up for by the intensity of the sun’s more direct light during the summer months (see our March edition).

The moon

moonrise

The moon has long captivated observers of all ages. July’s lunar phases of the moon occur as follows:

  • First quarter on July 1
  • Waxing gibbous on July 5
  • Full moon on July 9
  • Waning gibbous on July 12
  • Last quarter on July 16
  • Waning crescent on July 19
  • New moon on July 23
  • Waxing crescent on July 27
  • First quarter (2nd) on July 30

The planets

There are two planets prominently on display this summer. Jupiter, discussed in our May edition, is well up in the constellation of Virgo (near Spica) at sunset.

Saturn can be found low in the south near the border of Ophiuchus, Scorpius and Sagittarius around midnight.

Saturn

Saturn is one of the original “wandering stars” known in ancient times. Of all the planets known to ancient societies, Saturn moved the slowest (it takes 30 years to orbit the sun), and was associated with majesty and grandeur.

When Galileo turned his “optic tube” towards the stars, he observed the rings and drew them in his journal. His views through his first telescope (in 1610) were quiet poor. However, his observations made just over 400 years ago (in 1616), were good enough to show him that Saturn was different from all the other planets. He didn’t understand what he was seeing but we have since learned that this planet is surrounded by an immense and spectacular ring system.

 sketches of saturn

Like Jupiter, Saturn is a gas giant of immense size (around 120,000 km across). Its rotation rate is just over 10 hours which, compared to Earth’s 24-hour day, is quite speedy. Like Jupiter, Saturn’s rotation rate and chemical composition have created cloud belts, although they are fainter and show less contrast then Jupiter’s (see Killarney Provincial Park Observatory photo below).

saturn

Though very large, Saturn is actually not very dense. If you dropped Saturn in a giant bathtub, it would probably float! Despite its lightness, its ring system earned Saturn the nickname “crown jewel of the planets.”

Saturn’s rings are made of ice and dust particles, ranging from thumbnail size up to a small building. They are most likely leftover debris from the initial formation and collisions of the planets and early solar system material. Saturn has over 60 moons at last count and it is believed that many of these moons help to “shepherd” the ring material into a constant orbit.

Saturn’s largest moon – Titan – is larger than the planet Mercury and has its own atmosphere. Titan is easy to see in an amateur telescope. Titan goes through its own liquid cycle; like Earth, it rains on Titan. The rain pools in rivers, ponds and lakes which then evaporate, forming clouds. Unlike the Earth, however, Titan’s liquid cycle is made up of methane rather than water.

Featured constellations: the Birds of Summer

In this month’s edition of Eyes on the Skies, we will discuss the Summer Triangle and the constellations of Lyra, Cygnus, Aquila, and Scorpius.

constellations

The summer triangle

High overhead, as seen at the end of July twilight (which tends to last until near midnight), are three very bright stars that make out an upside-down isosceles triangle:

  • Vega (pronounced “Vee-gah”)
  • Deneb (pronounced “Deh nehb” with the “e” sounds used as in “them”)
  • Altair (pronounced”All tair” (last part as in “chair”)

Summer Triangle

While the Summer Triangle is quite noticeable it is not recognized as an official constellation. From city skies, it is sometime all one can see through the light pollution. However, in the often pristine skies visible in our parks, we can see much more of the constellations that each one of these stars anchors.

Lyra the Harp

Vega, a beautiful blue star, is the brightest in the small constellation of Lyra the Harp. The name “Vega” come from the Arabic al nasr al waqi or “Swooping Eagle.” The harp is said to be the instrument made by Hermes, son of Zeus, and used by Orpheus.

Lyra

Lyra has two interesting objects that lie within its realm. A beautiful double star (stars in orbit around each other) lies just to top-left from Vega: Epsilon Lyrae. Epsilon Lyrae is special in that it is actually a “double double.” Two pairs of double stars, each in orbit around each other!

The other interesting object is the ring nebula M57 (number 57 in Charles Messier’s catalogue). This smoke-ring-looking object is actually discarded gas given off by a star near the end of its life. The core of the star remains in the center, but you need a good telescope to see it.

Cygnus the Swan: a bird of many feathers

To the east of Lyra is a much larger pattern of stars that forms a cross. Four stars running north to south from Deneb are met with three stars running east to west. This pattern forms the “Northern Cross” that many people have learned to find. The name of the star Deneb comes from the Arabic Dhaneb meaning “tail” (as in tail of the bird).

So where is the bird?

Cygnus

There are at least two birds hidden within the same stars. The Anishinaabe people recognize a beautiful crane lying among these stars. The star Deneb is the tail of the bird and its body stretches down the long axis of the cross. By adding one star on each side of the short axis of the cross, we complete the wings.

The ancient Greeks envisioned these stars as a swan representing Nemesis, in her escape from Zeus. The head of Cygnus is marked by a star known as Alberio. Alberio is one of the most beautiful double stars in the sky. A blue and gold pair are visible in a telescope of even lower power.

Running through Cygnus is a band of light broken up by some dark patches. This, of course, is the Milky Way. It is formed by the light of millions of distant stars. They are so far away that we cannot see the individual points of light but the combined glow of their merged light. A careful look with binoculars reveals the myriad of stars within. Indigenous traditions recognize this region as a river upon which their ancestors travelled in the afterlife. The stars in this area were the campfires lit by those ancestors as they traversed the river.

Aquila the Eagle

The last star of our Summer Triangle is Altair. The name Altair come from the Arabic al nasr al tair or”soaring eagle.” Altair marks out the eye of the eagle and the body stretches down and towards the west.

Aquila Scutum

Altair is a fascinating star in that it rotates incredibly rapidly – once every 9 hours (compared to about 25 days for our sun). The Milky Way continues to run down through Aquila towards Sagittarius. A binocular view through this area reveals many star groups and clusters of stars.

The Summer Triangle and the Time Machine

Perhaps one of the most surprising revelations that was uncovered in the past few years is that the brightness of a star does NOT indicate how close it is to us. In fact, some dim stars are quite close while some bright stars are quite far away.

Take the Summer Triangle, for example. All the stars look about the same brightness but, as we will soon see, they are at very different distances.

Astronomers measure the distances to the stars in a unit known as the light year, or the distance that a beam of light can travel in one year – just under ten trillion (10,000,000,000,000) kilometres. The star Altair is about 16.7 light years away. Vega is about 25 light years away. But Deneb is over 2,500 light years away or 100 times further than Vega.

starry night at Woodland Caribou PP

Since nothing can travel faster than a beam of light, the light that we see from Altair (16.7 light years away), left us 16.7 years ago. Imagine a courier asked to bring us a package from the star Altair. This intergalactic space courier travels at maximum speed (the speed of light) and since Altair is 16.7 light years away, it take the courier 16.7 years to reach us.

The light that we see today from Deneb left the star about 2,500 years ago. One of the furthest objects that we can see in a dark sky is the Andromeda Galaxy. At 2.5 million light years away, the light that we are seeing now left the Galaxy during the early Stone Age! When we look to the heavens, we look back in time to the beginning of everything.

Scutum the Shield

Down and to the right of Aquila the Eagle is Scutum the Shield. Scutum looks just like a mini Corona Borealis (see the June edition). Scutum’s full name is “Scutum Sobiescianum” or “King Sobieski’s (of Poland) shield.”

Towards the lower-right side is a fuzzy patch. This is a beautiful open cluster known as M11 or the “Wild Duck” cluster.

Aquila Scutum

Stars are born from interstellar gas clouds that have condensed into balls of rotating gas. Under the extreme pressures from the mass of gas, star cores become hot enough to fuse hydrogen into helium. Eventually, over time, the original interstellar gas cloud disperses and what is often left behind is a loose cluster of between a few dozen to several hundred stars. That is what we are seeing when we view M11: the remnants of star birth.

Scorpius the Scorpion

The final constellation for this July edition is that of Scorpius the Scorpion. The bright red star Antares, meaning “rival of Mars,” marks the heart of the scorpion. Two claws extend towards the right (west) from Antares and the body extends towards the left (east) ending in a very well-formed stinger.

This is one of the best-looking constellations (in terms of it looking like what it is supposed to represent!):

Scorpius

The star Antares is a luminous red supergiant in the final stages of its life. It is truly massive. In fact, if you were to replace our sun with Antares, the planets Mercury, Venus, Earth and Mars and much of the asteroid belt would all be within the outer atmosphere of the star itself.

This is a very rich area of our Milky Way with gas clouds, clusters of newly formed stars and globular clusters found in droves. When we look in this region, we are actually looking near the centre of our Milky Way galaxy.

Meteor showers

There are two meteor showers that become present in July. The Capricornids are slow-moving meteors that appear to come from the eastern part of the sky and are present from July 5 through August 15. This meteor shower is relatively weak with only 5 to 10 meteors per hour at best visible in a dark sky.

On the other hand, the Delta Aquarid meteors peak in the latter half of July. They are faster with a peak of between 10 to 20 meteors an hour. They also appear to be coming from the eastern part of the sky.

This completes our review of the July skies…

Come back next month to learn about our galaxy and how to create a calendar from the back of a turtle.

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