Sky at a Glance May 18 – 25

Graphic showing the path of the International Space Station (ISS) from the Heavens Above website.

This Week’s Sky at a Glance, 2019 May 18 – 25 ~by Curt Nason

Amateur astronomers have a Messier Marathon around the new Moon in mid-March to early April, in which they try to observe all 110 fuzzy objects in the Messier catalogue in one night. This week casual stargazers have an opportunity to do an ISS marathon.

The International Space Station (ISS) orbits the earth at an altitude of about 400 km, and at this height it completes an orbit in approximately 90 minutes. The ISS has large solar panels that reflect sunlight earthward, which make it bright enough to rival Jupiter and Venus at times. Usually, we can catch it once or twice in morning twilight for a period of about ten days, then in the evening twilight for the same stretch, and then it is unseen for a while as the overhead passes are in daylight. For a few weeks either side of the summer solstice, when we have long periods of twilight, the ISS can be seen four or five times from evening through to morning. If you see it in each pass throughout the night you have completed the ISS marathon. This week is one of those times.

To determine when and where to look I use the website Heavens-Above, but there are other apps such as Satellite Safari that give the same information and may even give you an alert when a pass is about to occur. Heavens-Above defaults to zero degrees latitude and longitude so be sure to enter your location. Information includes the date and time, brightness, and altitude and azimuth of when it is first visible (usually ten degrees above the horizon), at its highest, and when it disappears into earth’s shadow or below ten degrees. Brightness is given in stellar magnitude, where the lower the number the brighter is the object, and the ISS is usually bright enough to be a negative number (magnitude -3 is about 2.5 times brighter than -2). With the Heaven’s-Above website, clicking on the date brings up a sky map showing the path of the ISS through the constellations. Since earth rotates under the satellite, the path through the constellations will differ with each pass but it is always approximately west to east.

This Week in the Solar System

Saturday’s sunrise in Moncton is at 5:43 am and sunset will occur at 8:48 pm, giving 15 hours, 5 minutes of daylight (5:51 am and 8:50 pm in Saint John). Next Saturday the Sun will rise at 5:36 am and set at 8:55 pm, giving 15 hours, 19 minutes of daylight (5:44 am and 8:58 pm in Saint John).

The Moon is full this Saturday, the Mi’gmaw Frog Croaking Moon. Jupiter rises around 10:30 Monday evening, about 20 minutes before the Moon. Mars passes just above the M35 star cluster in Gemini on Sunday evening, making a pretty sight in binoculars or a telescope. Saturn rises at 12:30 and is well placed for early morning observing. Venus can be seen in morning twilight rising 50 minutes before sunrise, and Mercury reaches superior conjunction behind the Sun on Tuesday.

The provincial astronomy club, RASC NB, meets at the UNB Fredericton Forestry-Earth Sciences building this Saturday at 1 pm. All are welcome. The Ganong Nature Park near St. Stephen is hosting a presentation on the Moon and a full Moon hike this Saturday at 8:30 pm, weather permitting. Donations to the park are welcome.

Questions? Contact Curt Nason.

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