Stargazing in the May Skies

by Cam Wipper, CFHT remote observer

editor’s note: Cam had an April column, it didn’t get posted here, however excerpts shared on social media.

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.

Sunrise/sunset times for Waimea
Sunrise/sunset times for Waimea

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: This is a fantastic month for stargazing: on tap we have a meteor shower, ALL naked eyes planets as well, as excellent viewing of the Southern Cross!

CFHT cloud cam image from May 4th.  Meteor is part of this month's Eta Aquarids meteor shower
CFHT cloud cam image from May 4th. Meteor is part of this month’s Eta Aquarids meteor shower

The month starts with a bang, as the Eta Aquarids Meteor Shower runs from April 19th to May 28th, with the peak occurring on the nights of May 6th and May 7th. On these nights, you will see up to 30 meteors per hour; one of the highest rates of the year (though only half of what those viewers in the Southern Hemisphere will see). As the name suggests, meteors will appear to radiate from the constellation Aquarius which rises at 3:30am. Meteors, of course, can appear across the sky, and at all hours of the night—though viewing will be considerably better after moonset, which roughly coincides with the appearance of Aquarius in the early morning.

Moving on to the planets: Right at the start of the night is Mars. It can be found chasing the Sun into the west just after sunset early in the month. By the end of the month, it will be pretty well lost in twilight’s glare.

Across the sky in the east we have the giant planet Jupiter. Likely the very first “star” visible in the sky after sunset, Jupiter will be available for viewing until around 3:00am all month.

Next up we have the perennial favorite, Saturn. Our ringed world appears in the east around 22:30 at the start of the month and as early as 20:30 at the end of the month. It is located in a very special place right now—Saturn is nestled in the heart of the Milky Way. If you’re up to view Saturn will find it sitting just above the constellation Sagittarius, surrounded by the glowing nebulosity of the Galactic Core.

After Saturn, we have our nearest planetary neighbor: Venus. Appearing around 4:00am at the beginning of the month (a little earlier at 3:30am at the end), Venus will appears as a brilliantly bright object—only outshone by the Moon. Look for a really special pairing with the waning crescent Moon on the morning of May 22nd. On this morning, the Moon will sit just below Venus, with both clearing the horizon by 3:45am.

Finally, we have Mercury. Mercury reaches a position known as ‘Greatest Western Elongation’ on May 17th. When here Mercury is as far from the Sun as is possible, making it the best time to view it. Look east, starting around 04:30, through to morning twilight to see the smallest planet in the Solar System.

Moving on the stars: At the start of the night, we have one of the most famous constellations in the sky: 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.

Moving into the spring and summer sky, we have the famous Southern Cross moving into our Hawaiian skies. With Hawaii being the only state in the USA to have a view of this iconic southern constellation, it’s appearance is a real treat for visitors and kama’aina alike. It will appear around 19:00 and reach it’s highest point around 22:30. This is some of the best times of the year to view it, so don’t miss this chance!

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

With both the Southern Cross and Polaris, the North Star, visible in the sky this month (see the March guide for how to find the Polaris), this means that the largest of our traditional Hawaiian constellations, or ‘starlines’ is visible: Ka Iwikuamo’o (“The Backbone”). When included with this starline, the Southern Cross is known as Hanaiakamalama (“Cared for by the Moon”) and Polaris is Hokupa’a (“Fixed Star”). Ka Iwikuamo’o stretches north-south across the sky connecting these two constellations. In between them is a star called Hokule’a. Known as Arcturus is western astronomy, Hokule’a, is a very special star in Hawaii. It is the zenith star, the brightest star in the sky that passes directly through the top—or zenith—of the sky. Ancient Hawaiian and Polynesian navigators knew this and used it as a marker to help guide them to the Hawaiian Islands.

Moon phases for May 2017
Moon phases for May 2017

Lastly, rising in the southeast in the second half of the night we have one of the most spectacular sights in the sky: the aforementioned Milky Way. The center of our galaxy, the Galactic Core, is found between the constellations of Sagittarius and Scorpius, right near Saturn. You’ll need dark skies (i.e no Moon) to find it, so the best times will be at the end of the month around the May 25th New Moon.

The appearance of Scorpius also signals the disappearance of Orion. According to mythology, the two are enemies and when placed among the stars, the separated. This means that you can never see them both in the same sky—if you see one, the other will be hidden.

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

If you have any questions, comments or are new to stargazing and would like some tips on getting started, email me at wipper@cfht.hawaii.edu. Aloha!

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