~ St. Maarten’s Backyard Astronomy for July 16 &17 ~
Sun rises at 5:45am
Sun sets at 6:51pm
Moon phase: Second Quarter, Waxing Gibbous
Moon rises at 4:15pm
Moon sets at 3:36am
Plenty of Planets
Look to the west Saturday evening just after sunset, so about 7:00, the planets Mercury and Venus will have a conjunction (which means they will appear at their closest in our sky). It won’t be easy to spot them, though, you’ll need a clear western sky; and don’t wait too long after the sun goes down as they follow the sun below the horizon within 30 minutes.
Bring binoculars, if you have them, to increase your chances of spotting these embracing worlds – Mercury and Venus – which on Saturday will reside only one-half degree apart. For reference, the moon is about one-half degree across.
It’ll be much easier to spot the planet Jupiter and the star Regulus, as they’ll still be out after Mercury and Venus have set. Regulus sinks below the horizon roughly an hour after Venus and Mercury do, and then Jupiter sets approximately one hour after Regulus.
The planets Mars and Saturn will be much easier to see in these evenings. On Saturday evening especially, because on that night, Mars and Saturn line up with the waxing gibbous moon.
Day by day, Mercury and Venus will climb away from the glare of sunset; in contrast, the planet Jupiter and the star Regulus will fall toward the sunset glare. Although both Mercury and Venus are moving upward, in the direction of Regulus and Jupiter, Mercury climbs at a swifter pace than Venus does.
Therefore, Mercury will meet up with Regulus first, on July 30. Venus will then stage its rendezvous with Regulus about a week later, on August 5.
Likewise, Mercury will pair up with Jupiter on August 20. Then, about a week later, Venus will couple up with Jupiter on August 27, to present the closest conjunction of two planets for the entire year.
A Gibbous Moon
Cast your eye to the waxing gibbous moon this weekend and see if you can make out the dark areas on its surface. These are smooth, low-lying lunar plains, called mare (singular) or maria (plural), which are the Latin words for sea or seas. In times past, astronomers really thought the dark areas contrasting with the light-coloured, highlands were lunar seas. They weren’t far off! These lunar plains are actually solidified lava flows, the remnants of ancient seas of molten basalt.
You should be able to see the maria on the moon with the naked eye. To observe lunar details more closely, use binoculars or a telescope. Interestingly, the view will be better around twilight, because the dark of night accentuates the moon’s harsh glare.
The lighter-coloured highland regions of the moon are composed of anorthosite, a certain kind of igneous rock. On Earth, anorthosite is not common, except for in the Adirondack Mountains and the Canadian Shield. For this reason, people in this part of the world like to fancy that the moon originated from their region.
The prevailing theory states that the moon was formed when a Mars-sized object crashed into the Earth, creating a ring of debris that eventually condensed into the moon. I suppose time will tell whether this explanation for the moon’s origin is true or false.
More about Mars
Mars is one world in our sky whose brightness changes dramatically over about a two-year cycle. The red planet was at its largest and brightest a couple of months ago, when we passed between it and the sun. As the Earth and Mars orbit the sun, our relative positions can get seven times closer than at their most remote distances.
A year from now – in July 2017 – Mars will pass behind the sun and disappear from view. In other words, Earth will have travelled so far ahead of Mars in our smaller, faster orbit that we’ll turn the corner ahead of Mars in orbit, leaving Mars behind the sun’s glare.
So maybe you can see that July 2016 is good viewing for Mars! Right now – July 2016 – is a great time to watch Mars. So enjoy the red planet before it fades into oblivion in 2017, as seen from our earthly perspective!
Thank you for keeping up with the Night Sky articles. Comments and feedback are always welcome. If you are out later on in the week, each star rises about four minutes earlier each day than written here, and the moon rises 50 minutes later. Night Sky is researched and compiled by Lisa Davis-Burnett, email: email@example.com