What’s Up in the Night Sky? May 2016

Fred Barrett | May 04, 2016

May is Mars month!

Every 780 Earth days (2.14 years) Mars has its closest approach to Earth when it is in opposition, which occurs when it is in a line between the Earth and the Sun. Mars has the second greatest eccentricity after Mercury. Eccentricity is a measure of how non-circular an orbit is. Mars has an elliptical orbit and thus the distance at opposition can change depending on where it is in its orbit.

Due to orbital mechanics, Mars’ point of closest approach actually occurs eight days after opposition. Opposition is at 7:17 a.m. EDT on May 22 and eight days later, on May 30 at 5:34 p.m. EDT, Mars will be 75,280,000 km from Earth. It will be roughly in the middle of the constellations Ophiuchus, Libra and Scorpius. It will also be to the upper right of the bright star Antares, which, funnily enough, translates to mean “rival of Mars”!

A telescope larger than 4 to 6 inches is good for observing Mars, which will be about 28 degrees above the southern horizon, which is on the low side. This means a thicker atmosphere to view through and that will have some effect on resolution and clarity.

The best time to observe Mars is right now and on into late summer. Its diameter won’t vary that much during this period.

May is also Mercury month! Mercury will make a transit across the face of the Sun on May 9. This last happened in November, 2006 and will only occur 14 times in the 21st century. Mercury usually passes slightly above or below the Sun due to its axial tilt of 7 degrees to the Earth’s orbital plane. The transit begins at about 7:12 a.m. EDT at the middle of the western limb (left side) of the Sun. For the next seven and a half hours Mercury will cross down to the south-east limb of the Sun. It will be half way across about 10:57 a.m. EDT and will leave the face of the Sun about 2:40 p.m. EDT. Mercury’s disk will be a quite small, so watch that you don’t confuse it with a sunspot. Look for a perfectly circular and black dot. A sunspot looks like a messy, multi-shaded blob. This event won’t happen again until November, 2019.

CAUTION! Do not look at the Sun directly with your eyes or through any binoculars or telescope without a proper solar filter, and that filter should be tightly fixed on the front of the instrument you use. You can also project an image of the Sun through your optical device onto a white surface about 12 to 20 inches from the eyepiece.

Gravitational waves have been discovered! LIGO (Laser Interferometer Gravitational-wave Observatory) has finally been successful in detecting gravitational waves from the collision of two small black holes. Einstein predicted their existence a hundred years ago. The merging of the two black holes took place about 1.3 billion light years away. There are two LIGO observatories and that allows astronomers to triangulate roughly where in the sky it occurred. LIGO is composed of two 4km laser paths at right angles to each other. When there are no gravitational waves, they cancel each other out. When gravitational waves occur, the compression and expansion of one path causes a detectable difference in the laser beams. I expect that the technology will improve quickly now that it has been shown to work.

May 5: The Eta Aquarid meteor shower peaks. Watch for them several days before and after the peak. It is best in early morning before dawn.

May 6: The Moon is at perigee (222,300 miles from Earth), closest distance.

May 9: Mercury is at inferior conjunction and crosses the face of the Sun (see above). Use a telescope with a proper solar filter to observe.

May 18: The Moon is at apogee (252,230 miles from Earth), farthest distance.

May 21: Full Moon. This Moon is called the Full Flower Moon or Full Corn Planting Moon. I’ve planted tulips at random all over my place and they’re coming up gang busters. They are my excuse for not mowing the lawn. Who wants to mow down beautiful flowers! Sadly, it often happens that the grass grows so high that I can’t find the lawn mower!

May 22: Mars is at opposition. The Moon is to the upper left of Mars.

May 30: Mars is closest to the Earth (46,800,000 miles). It is 18.6 arc seconds across and the closest and largest it has been since 2005.

Have a good month and if you have any questions or special topics that you would like to see in this column, please email me or make contact though this newspaper. Let me know how your observing has gone this month, especially anything unusual.  

You may contact Fred Garrett through this paper or email to This email address is being protected from spambots. You need JavaScript enabled to view it.

The Beginner’s Observer’s Guide by Leo Enright is available at the Sharbot Lake Pharmacy or by contacting the Royal Astronomical Society of Canada www.rasc.ca/publications, subscriptions for our very own excellent Canadian astronomy magazine, Sky News, are also available from RASC..