Thu. Dec 7th, 2023
red gases on black starry sky

Stargazing in July is always a special pleasure. This is because this season marks the return of the three bright stars that make up the Summer Triangle: Deneb, Vega and Altair.

The asterism (pattern of stars) that forms the Summer Triangle really became popular in big cities over the last 75 years and with the writings of HA Rey (famous for being the author of the Curious George books).

The popularity of this asterism is a negative reminder that, with increasing amounts of light pollution, urban observers often cannot see many stars besides the three bright stars of the Summer Triangle.

However, looking at the Summer Triangle from the city helps us practice finding those three bright stars: Deneb (top left), Vega (top right), and Altair (bottom).

Star triangle in dull night sky, tree in foregroundView of the Summer Triangle over north Toronto on a moonless night

The Summer Triangle and the Milky Way

To truly appreciate the Summer Triangle and the constellations of stars and objects it encompasses, it is necessary to travel to darker skies.

(Might we suggest our three Dark Sky Preserves: Killarney Provincial Park, Lake Superior Provincial Park, and Quetico Provincial Park?)

Telescope in foreground against starry sky with Milky WayView of the Summer Triangle over Kchi Waasa Debabing Killarney Provincial Park Observatory Dome

In the Summer Triangle image above, you can clearly see the three bright stars that appear to cradle the Milky Way.

In fact, because we look toward the center of our own galaxy, the Milky Way is rich and full of interesting objects to see. If you have binoculars and are at one of our dark sky sites, you will be able to see some of these interesting objects.

Let’s take a look at some of them:

Image of the starry sky of the Milky Way, with nebulae labeled.

The North American Nebula

The North American Nebula is an emission nebula, an interstellar cloud of gas and dust that is charged with light from nearby stars and fluoresces like a neon sign.

red gases in the black starry skyThe North American Nebula (left) and Pelican Nebula (right) captured from a 61mm refractor with specialized filters to improve contrast.

In this case, it looks a lot like central and eastern North America. (For those of you California lovers, don’t worry because it doesn’t appear here. There is a unique nebula that looks like California visible in winter skies!)

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The North American Nebula is located just to the left of Deneb, the upper left star of the Summer Triangle.

The Ring Nebula

The vast majority of Sun-like stars will generate a large amount of energy that will expel (or outgas) a large amount of material in their last few million years of normal life. This material receives energy from radiation from a hot central star (and re-emits light that we can easily see).

M57, the Ring Nebula, is an example of a planetary nebula. This type of emission nebula looks like a ring, but is actually spherical in shape. “Planetary” nebulae were so named because in the low-power telescopes of those who first observed them hundreds of years ago, they resembled planets in shape and relative size.

color ring in the black starry skyM57, the Ring Nebula, imaged by the 0.41 m telescope at the Kchi Waasa Debabing Killarney Provincial Park Observatory Complex Dome

That hot central star is what astronomers call a white dwarf, the hot carbon core of what was once a main sequence star. White dwarfs can continue to shine for billions of years, but eventually they will fade into a black dwarf, the dead ember of a once bright star.

The Ring Nebula is located just below Vega, the upper right star of the Summer Triangle.

The Veil Nebula

The end of a massive star’s life is an explosive event known as a supernova. This incredible explosion shatters the star and sends a shock wave into space.

For a brief period, the supernova can eclipse its host galaxy. (In the image below, the bright spot marked by the perpendicular lines is a supernova in a galaxy, NGC 4647, 60 million light years away. The core of the galaxy is the soft-looking star slightly above and to the right ).

deep blue sky with starsImage captured by York University resident astronomer Blake Nancarrow using the 0.4m telescope inside the Kchi Waasa Debabing Dome at the Killarney Provincial Park Observatory complex

The Veil Nebula (pictured below) is the supernova remnant (SNR) of a star that exploded within our own galaxy between 10,000 and 20,000 years ago.

red gases in black starry skiesThe Veil Nebula imaged with a 61 mm refractor attached to the 0.41 m telescope at the Kchi Waasa Debabing Dome of the Killarney Provincial Park Observatory complex

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The shock wave from the supernova spread in all directions and charged the gases that exist between the stars. This charged gas glows red and is quite spectacular if photographed with the right equipment. Of the objects mentioned, this is the only one that is difficult to observe only with binoculars.

It is located just below and to the left of Deneb, the upper left star of the Summer Triangle.


Deneb, the upper left star of the Summer Triangle, also marks what is known as the “Northern Cross.” Four stars, including Deneb, can trace their path downward and to the right, ending in the star Albireo.

Albireo is a double star, although astronomers are still determining whether the two contrastingly colored stars are physically bound to each other through gravity or simply an optical double that makes them appear part of a single system.

two dots, one blue, one red, on blackAlbireo, photographed by the 0.41 m telescope at the Kchi Waasa Debabing Killarney Provincial Park Observatory Complex Dome

Albireo is perhaps one of the most famous double stars because it is relatively bright and has a beautiful blue and gold appearance.

The colors of double stars are directly related to their mass and life stage. The blue star on the left is a hot main sequence star that has more than twice the mass of our sun. Its surface temperature is very high, creating the blue color. In contrast, the amber star on the right is an example of a star that left the main sequence and is now a red giant star. Its outer atmosphere has swollen and cooled, hence the red color.

The Wild Duck Open Group

Newly formed stars produce tremendous pressure caused by the radiation they emit, pushing against the nebular cocoon of gas in which they formed. What remains is a loose star cluster.

star cluster in the black skyM11, the wild duck cluster, photographed by the 0.25 m telescope at the this debabing Killarney Provincial Park Observatory Complex Dome

The Wild Duck open cluster (M11) is one of the richest open clusters in the sky, composed of a thousand stars.

It is located below and to the right of Altair, the lowest star of the Summer Triangle.

Want to know more about the stars you can see in Ontario parks? We’ve got you covered!