WHAT’S UP IN THE SKY THIS SEPTEMBER 2017?

WHAT’S UP IN THE SKY THIS SEPTEMBER 2017?

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The “Ber” months have come. The season is about to change as summer is going to end soon and in the UAE, many holidays are approaching. Wondering what’s going to be up in the sky for the coming month? The following is a list of astronomical events for September 2017. All dates and times were given in Gulf Standard (UAE Local) Time.

September 5, 2017: Neptune at Opposition

Figure 1. Illustrated View of Neptune through the 80EDF 3” telescope at 16x magnification (Image Credit: Stellarium)

By night time of this day, Neptune will be in opposition and at its close approach to Earth. This simply means that the blue gas giant will appear at its brightest and largest than ever before. Neptune will be situated directly opposite of the Sun in the sky, which would give it further illumination. However, due to the (nearly full; about 98% illuminated) waxing gibbous moon located near to it within the constellation of Aquarius (the water bearer), and the fact that it is very far away from Earth, it will not be easily seen through naked eye and will need some astronomical equipment. When viewed through powerful telescopes or binoculars, it would look like a faint bluish “star”. Long exposure photography is very much needed to reveal its detail and moons. The planet will be visible all night round; starting at around 8:25PM after the twilight fades; positioned about 24° above the eastern horizon, reaches its highest point around 57° above the southern horizon at 12:20AM of September 6, 2017, until sunrise when it completely sets.

September 6, 2017: Full Moon

Figure 2. The Full Moon and its Surface Features just after the Partial Lunar Eclipse taken from Al Sadeem Observatory last August 8, 2017

Situated on the opposite side of the Earth as the Sun, the moon will be fully illuminated (100%) on this day. For selenophiles (individuals who love the moon), this is the best time to observe all the surface features of this celestial object, including the craters and maria (dark patches). It will start appearing at around 6PM at it rises from the east, and can be seen throughout the night until sunrise; positioned in the constellation of Aquarius (the water bearer). Because of its full illumination during this phase, it will not be a good time for deep-sky observation with the entire moonlight glaring out most of the faint celestial objects.

September 12, 2017 – Mercury at Greatest Western Elongation

Figure 3. Illustration of Mercury at Greatest Western Elongation (about 12° above the eastern horizon) just before sunrise on September 12, 2017 (not to scale) (Image Credit: Stellarium)

The smallest planet in the Solar System, Mercury will appear at its highest point just few moments before sunrise.  The maximum extent of angular separation from the Sun as seen from Earth will be at around 12° (in the UAE). This means Mercury can be only seen up to 12° above the eastern horizon, from 4:48AM until 5:47AM, before disappearing from view caused by the glare of daylight from the Sun as it rises. Though it is moderately bright, observing it will be quite of a challenge from the fact that Mercury is situated near the Sun in the sky.

September 20, 2017: New Moon

On this day, the moon will not be visible as it will be situated at the same side of the Earth as the Sun, in the constellation of Virgo (the virgin). With no moonlight glaring much of the night sky, this is the best time to observe the deep sky objects throughout the night. It is predicted that this lunar phase will occur on this day. However, the month transition from Dhu l-Hidjdja 1438 to Muharram 1439 (Islamic New Year) shall take place two days later (September 22) in accordance to the Hijri Calendar.

September 22, 2017 – September Equinox

Figure 4. Diagram showing Earth’s Orientation during the September Equinox (Image Credit: eclipsegeeks.com)

On this day, the Earth’s axis is not tilted towards nor away from the Sun. This results in an approximately equal duration of day and night in all areas of the Earth (about 12 hours). During this period, the Sun lies perpendicular to the Earth’s equator, it will appear to rise and set exactly from due east and west respectively; while in the equator, the Sun will be directly overhead at noon. This marks the beginning of autumn or fall in the Northern Hemisphere and spring in the Southern Hemisphere. After this day, daytime (nighttime) will gradually decrease (increase) in length for the Northern Hemisphere and the inverse occurs in the Southern Hemisphere as the Earth’s axis slowly inclines.

September 27, 2017: Close Approach of the Moon and Saturn

Figure 8. Illustration of the Close Approach of the Waxing Crescent Moon and Saturn with Antares on September 27, 2017 (not to scale) (Image Credit: Stellarium)

The Moon and planet Saturn would appear close to each other (around 3°27’ angular separation) at the sky when viewed from Earth. These celestial objects will be observed at the south-southwestern portion of the sky in the constellation of Ophiuchus (the serpent bearer) as the dusk fades at around 7:15PM until it sets at the west-southwestern horizon at 11PM.  The moon will be at the Waxing Crescent phase (about 46% illuminated). Saturn would look like a “yellowish/reddish unblinking star”. Antares, the reddish star in Scorpius can be seen southeast of these celestial objects.

References

Astronomy Calendar of Celestial Events 2017 . (n.d.). Retrieved from Sea and Sky: www.seasky.org/astronomy/astronomy-calendar-2017.html

Calendar of Astronomical Events. (n.d.). Retrieved from In-The-Sky.org: http://in-the-sky.org/newscal.php?year=2017&month=7&maxdiff=5

Islamic calendar 2017. (n.d.). Retrieved from Calendar.sk: https://calendar.zoznam.sk/islamic_calendar-en.php

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