Stargazing in the October Sky

by Cam Wipper, CFHT remote observer

What You Need: Just your eyes! Everything in this guide can be seen with nothing more than your very own eyes. No special equipment required.

Where To Go: We here on the Big Island are blessed with some of the greatest night skies on Earth. You can find many of the targets listed here from your own backyard. Of course, if you live in Waimea, Hilo or Kailua, the lights of your town can make fainter objects more difficult to see. The best locations are those far from light sources. Some of my favourite locations are Pu’u Huluhulu off of Saddle Road (across from the Maunakea Access Road), along Chain of Craters Road in Hawai’i Volcanoes National Park (remember: there is no entrance fee after 8pm— perfect for stargazers) and along Mana Road on the slopes of Maunakea.

Surprisingly, the summit of Maunakea, though unbeatable for telescopes, is not the best site for human observers. Due to the thinness of the air, and resultant dearth of oxygen, at the altitude of the summit, human night vision becomes far less efficient than at altitudes closer to sea level. For this reason, it is best to stargaze no higher than 10,000 feet (3000 m). The Maunakea Visitor Information Station is an example of a site located near this elevation.

What To Look For: October is an great month for stargazers. We have meteor showers, a Supermoon, a number of planets and some of the best constellations of in sky all to look forward to this month.

Moon phases for Waimea
Moon phases for Waimea

We’ll start with one of the most well-known of phenomena’s: a Supermoon. A Supermoon occurs when the Moon’s full phase coincides with the Moon being at perigee—or closest to Earth. While the instances of Supermoon’s have been recently well-known in popular culture, Supermoon is not an ‘official’ astronomical term and as such there are no official rules that determine when a Supermoon will occur. In fact, isn’t an astronomical term at all: it’s an astrological one. The most common definition of a Supermoon was given by astrologer Richard Nolle in 1979. He defined a Supermoon to be a, “new or a full Moon that occurs when the Moon is at or near (within 90% of) its closest approach to Earth in its orbit”. According to timeanddate.com, it is unclear, and possibly totally arbitrary, why he chose 90%. For our purposes, we will use the same definition as timeanddate: a Supermoon occurs when the full moon is less than 360,000 km (223,700 miles) from Earth. Using this definition, the full Moon of October 15th is a Supermoon. The full Moon at these times can appear about 30% larger in area than it does at apogee (farthest from Earth), and can be similarly brighter.

In addition to our Supermoon, we have two minor meteor showers this month. The first of these is the Draconids. This shower peaks on the night of October 7th and will have an hourly peak of 10 meteors per hour. Unlike the majority of meteor showers, which peak in the early morning hours, this one is at its best as soon as the sky is dark. Look to the north into the constellation Draco, which sets by 2:00am.

Sunrise, sunset times for Waimea
Sunrise, sunset times for Waimea

Our second shower is the Orionids, which peaks on the nights of October 21st and 22nd. This shower has been observed since ancient times as it is the result of the most famous comet in history: Halley’s Comet. The Moon is not at it’s most favorable (we are only a week past the Supermoon), but you should still be able to find some of the 20 meteors per hour forecasted. For this shower, we are back to the usual, “best viewing after midnight” recommendation, along with a view to the east, as they will appear to radiate from our famous hunter, Orion who rises around 11:30pm.

As for our planets: as we have had for the past few months, our pair of Mars and Saturn are still visible in the western early evening sky. Joining Saturn low in the west, around mid-month is Venus. With each passing night, these two words will get closer and closer together until October 27th. On this night, from sunset to around 7:00pm, Saturn, Venus and the brilliant red star Antares of the constellation Scorpius will form a perfect line in the sky.

Moving on the stars: As it was last month, visible this month, in the very early evening sky is the beautiful star: Arcturus. As the fourth brightest star in the night sky, it is highly visible and part of the Greek constellation of Boötes. While, a prominent star in Western astronomy, this star has extra significance here in Hawai’i. In the islands, it is known as Hōkūleʻa, the “Star of Joy”. Hōkūleʻa is the zenith star, or the star that passes directly through the highest point in the night sky, here in the Hawaiian Islands. Because of this, it could be used by ancient Polynesian and Hawaiian navigators as a guide to the Hawaiian Islands, when voyaging up from more southerly islands like Tahiti or the Marquesas Islands. Hōkūleʻa is also part of the largest of the Hawaiian Starlines, Ka Iwikuamo’o, “the backbone” of the sky.

'Imiloa's sky map of Kaiwikuamo'o
‘Imiloa’s sky map of Kaiwikuamo’o

This starline also contains one of the most special objects visible in the Hawaiian skies—Hōkūpa’a. The name Hōkūpa’a means “fixed star”—hōkū, the name of our CFHT newsletter, is “star” and pa’a is “stuck or firm”—and this is a very good name for this object. Of all the stars in the sky, this is the only one which does not move. You may know it as Polaris, the North Star. Polaris is not an extremely bright star, though it can be found by connecting the two stars at the end of the scoop portion of the Big Dipper—also part of Ka Iwikuamo’o known as Nā Hiku, “the Seven”—and then continuing that line into the north. This will point directly to the Polaris.

Polaris can be used to determine the latitude of your location on Earth. Since it is (almost) directly above the northern celestial pole, it’s elevation above the northern horizon from a given location on Earth matches that same location’s latitude north of the equator. For example, here on the Big Island, which is between 19°N and 21°N latitude, Polaris appears ~20° above the northern horizon at the end of the handle of the Little Dipper.

All the way at the other end of Ka Iwikuamo’o, we find the one of my personal favorite night sky objects: Hānaiakamalama here in Hawai’i. It is known as the Southern Cross in most other parts of the world. Hawai’i is the only one of the fifty U.S. states that the Southern Cross can be viewed from, though unfortunately it has set for now for the year. It will be visible again nest spring.

Now most of what was previously mentioned, is only visible in the early evening. If you’re up late, what can you find?

At around 11:30pm, one of the most famous constellations rises in the east: Orion. The famous Belt of Orion is one of the easiest night sky features to find. Look for a vertical row of three bright stars almost due east. To the north of them you will find Betelgeuse, a huge red supergiant star nearing the end of it’s life. To the south, you will see Rigel, a blue-white supergiant, estimated to be around 200,000 times more luminous than the Sun. These two stars are the ninth- and seventh-brightest stars in the night sky respectively.

Rising just before Orion is Taurus, the Bull. Taurus contains the bright red star, Aldebaran, often called the “Eye of the Bull”. Greek mythology describes Taurus and Orion as fighting in the sky, with Taurus defending the Seven Sisters from Orion’s rather lustful advances.

Merope Nebula in the Pleiades imaged by CFHT.
Merope Nebula in the Pleiades imaged by CFHT.

These sisters, in reality a stunning group of stars known as an Open Cluster, can be found as well. They are more commonly known as the Pleiades, and are positioned just above Taurus. A quick way to find them is to locate Betelgeuse. Then trace a line in the sky to connect Betelgeuse with Aldebaran. Finally continue that line past Aldebaran, and you will come to the Pleiades.

The Pleiades are well known across the Northern Hemisphere for their beauty and cultures around the world have their names for the group. In Hawaii, they are known as Makali’i, and they are mentioned several times in the Kumulipo, the Hawaiian Creation Chant, including on the fifth line of very first verse.
In Japan they are known as Subaru, a name which graces not only a successful automobile manufacturer (now you know my their logo are stars!), but also a telescope on Maunakea, which as you may guess, is owned by Japan.

Finally, we have the great legend of Perseus and Andromeda, playing out in the skies above our heads. The characters of this legend, the hero Perseus, the princess Andromeda, the king Cepheus, the queen Cassiopeia, the winged-horse Pegasus and the great monster Cetus can all be found in the sky tonight. The easiest of these characters to find are Pegasus and Cassiopeia. Pegasus most recognizable feature is the ‘Great Square’, as asterism of four stars which can be found in the east in the early evening, rising as the night goes on. Just to the north, we can see the characteristic ‘W’ shape of Cassiopeia. By 10:00pm, all of our characters have risen, with Perseus appearing last, just above the aforementioned Taurus the Bull.

For our retelling of this great legend check back later this month for the first entry of our Star Tales series.

With that, I wish you clear skies and happy stargazing!

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