Autumn Sky Offers Celestial Delights

Dr. Rishi Shah

The night sky of this autumn month would provide sky-gazers with some spectacular sights of Jupiter and Saturn and their moons, along with copious celestial entities that could be spotted all over the heavens. On September 22, the elusive planet Mercury would reach its greatest western elongation from the Sun. This would be the best time to view Mercury since it will be at its highest point above the horizon in the eastern morning sky.

Mercury could be marvelled at very shortly, towards the end of the month, in the eastern sky before sunup. Otherwise, it would be lost in solar glare as it would be too close to the sun. It would be mingling with stars that sketch the roaring constellation Leo (lion).

Planet Venus could be visualised well early in the eastern sky at dawn. It would then fade out with the sunrise. It would be cavorting with the stars of the compact constellation Cancer (crab). The red planet Mars will linger out of sight this month. It would be marching through the confounding constellation Virgo (maiden) during the daytime. The stretch of glorious galaxies dubbed Markarian's Chain could bejewel the constellation Virgo. The binary star Spica (Chitra) would be scintillating serenely in Virgo. It would be utterly 250 light-years away.

 The giant planet Jupiter could be discerned late at night in the eastern sky. It would climb high in the southern sky after midnight. It would slowly sink towards the western horizon before daybreak. With its mesmerising moons, the giant planet would be located as a shiny speck in the sparse, sprawling section of the puny constellation Aries (Ram). 

Far-flung planet Uranus could be relished to the east of Jupiter in the late hours of the night as a fulgurating nib of light dwelling in the barren-akin expanse of the constellation Aries. It would be evanescent in the western sky in the morning. The ringed planet Saturn could be admired in the eastern sky after sundown.

It would be ascending into the southern sky late at night. It would be sliding towards the western horizon before the day would commence. It could be recognised as a lambent light staying in the eastern segment of the charming constellation Aquarius (water bearer). The distant planet Neptune could be noticed in the eastern sky after sundown. 

It would be creeping high in the southern sky till the wee hours of the night. It would slip sluggishly towards the western horizon by day's end. The resplendent Neptune would be resting below the famed circlet-asterism of the rolling constellation Pisces (fishes).

On September 19, the far-away giant planet Neptune will be in opposition. It would be nearest to Earth, and its face would be illuminated by the sun. It would be more intense than any other time of the year and would be visible all night long. It would be the most appropriate time to ogle and photograph Neptune. Since it is extremely far away, it would appear as a tiny blue dot in most professional telescopes.

 The new moon would be on September 15, while the full moon would be on September 29. Its popular sobriquet would be full corn or harvest moon, as the farmers would have harvested corn during this time of the year. This full moon would also fall closest to the September equinox each year.

This moon would coincidentally be the last of four super moons in 2023. The moon would be sitting in immediate proximity to Earth and may seem slightly larger and brighter than usual. The September equinox would transpire on September 23, 2023. 

The sun would shine directly on the equator, and there would be almost equal amounts of day and night throughout the world. It would herald the first day of fall (autumnal equinox) in the Northern Hemisphere and the first day of spring (vernal equinox) in the Southern Hemisphere.

The word equinox has been eponymously derived from the Latin words aequus (equal) and nox (night). Equinoxes occur because the so-called polar axis of the earth's spin has been tilted trickily at an angle of a paltry 23.5 degrees to the plane of the earth’s orbit around the Sun. The earth would hurtle around the sun once every 365.242 days, and this would describe the period over which the cycle of the earth's seasons would repeat from one year to the next. The precise position of the sun at the moment it passes over the equator on September 23, 2023, would lie in the constellation Virgo.

The 8-day-old waxing gibbous moon would be 60 per cent full. Father’s Day will be observed on September 14. A colourful Teej ceremony, especially for women, would be celebrated on September 8. Rishi Panchami will be venerated on September 19. Kumari and Indra Jatra festivals will be revealed respectfully and with exuberance on September 28.

 The unmanned Chandrayaan-3, meaning moon craft in Sanskrit, had touched down successfully for the first time near the moon's uncharted South Pole. The Chandrayaan-3 mission has captivated public attention since its launch practically six weeks ago. Schoolchildren had followed the final moments of the landing through live broadcasts in classrooms. Chandrayaan-3 had traversed a more extended route to the moon than those taken by NASA’s Apollo crafts.

For the venture, less powerful rockets than those utilised in the US had been deployed. Consequently, the probe had to rush around the earth several times to build up sufficient speed before embarking on its month-long journey. Lander Vikram, which would translate to valour in Sanskrit, had detached from its propulsion module and had been dispatching images after entering lunar orbit.

The solar-powered, six-wheeled robotic rover Pragyaan (wisdom in Sanskrit) would explore the lunar topology meticulously and transmit data to control rooms over its two-week lifespan. India has been closing in on global space-faring nations such as the United States, Russia, and China by conducting many assignments at much lower costs.

This latest trip has a frugal price tag of 74.6 million US dollars. The Indian Space Research Organisation (ISRO) will be sending off a crewed expedition into space by next year.

 Our romantic moon (alias Luna) is our earth’s only natural satellite and was allegedly formed 4.6 billion years ago, not long after the formation of Earth in our solar system. The moon is in synchronous rotation with the earth. The first uncrewed trek to the moon took place in 1959 by the Soviet Lunar Programme, while the first humans landed on the moon with US Apollo 11 in 1969. The moon’s diameter is 3475 kilometres across. It would glide around Earth from an average distance of 384.4 thousand kilometres in 27.3 days. Its mean surface temperature recorded would vary from minus 233 degrees Celsius to 123 degrees Celsius. 

The dark side of the moon has been a conundrum-akin myth. This is because the moon would rotate on its axis at the same time it would need to scamper around Earth. Hence, the same side would always be facing the earth.

The opposite portion lurking away from Earth has been perceived by human eyes from spacecraft. The rise and fall of the tides on Earth would be a result of the moon’s tugs. There are two watery bulges in the earth due to the gravitational pull that the moon would exert: one on the side facing the moon and the other on the opposite side that would lie away from the moon. The moon has been drifting approximately 3.8 centimetres away from Earth annually.

The moon has much weaker gravity than the earth due to its minute mass. One person would weigh one-sixth (16.5 per cent) of the weight of the earth. Since the moon is devoid of an atmosphere, it would be unprotected from cosmic rays, meteorites, and solar winds. 

Thus, tremendous temperature variations are obvious. The lack of atmosphere would insinuate that no sound could be heard on the moon, and the sky would always look pitch black. Quakes on the moon could have been caused by the gravitational attraction of the earth. A prevailing theory has stipulated that the moon was once part of Earth and was created from a chunk that had broken off due to a mysteriously huge object colliding with Earth when it was relatively young.

(The author is an academician at NAST and patron of Nepal Astronomical Society or NASO)