Have you looked up on a clear night and been in awe of the brilliance of the stars and the depth of the universe? If so, or if you’re just curious to explore what the night sky has to offer, you’re in the right place. September arrives with astronomical phenomena that are worth looking at. You don’t need fancy telescopes or advanced knowledge in astronomy (although we will include some tips for those who do). You only have to cast your gaze to the sky in the nights to come to marvel at what is in view.
Before starting with the astronomical phenomena of the month, it may be useful to comment on how choose a good site to carry out our astronomical observation. The most important thing is to find a place with minimal light pollution. If you do not have a car or motor vehicle, simply try to get as far as possible from the town or city in which you live. You should especially stay away from streetlights and public lighting, which generate most of the pollution that bothers you when observing the sky. You should also try to make your observation in a night close to the new moonbecause the brightness of the moon can prevent you from enjoying the firmament.
If you have a car to travel further, use one of the light pollution maps that you can find online. It will suffice to search for “light pollution map” or its equivalent in English, “light pollution map” to find several pages that show the pollution present throughout the world. The general rule is that the less contamination you can find, the better. You can always find a clearer sky, in the middle of the ocean or the desert, but the best sky to practice astronomy is the one we have on our heads. With that said, let’s begin our review of this month’s events.
The disk of the Milky Way is glimpsed between a crop field. Photo: José Luis Oltra
Moon phases
Since August ended with its second full moon, we will start September with a waning moon, which will lose its brightness completely on September 15, then reaching the new moon. Although it will be difficult to see, this new moon will pass very close to the Sun, in preparation for the eclipse solarnext month (which can be seen from the US, Mexico, Colombia, Brazil and Central America). After this day the brightness of the moon will increase, until reaching the full moon at the end of the month, the September 29th specifically. This full moon will also pass close to the earth’s shadow, in preparation for the eclipse lunarfrom the end of October. This means that the best dates for astronomical observation will be the days around September 15.
If we only have those dates to go out into the field to see the stars, observing the moon itself with binoculars or a modest telescope can also be a fantastic option. It is especially interesting to observe the moon on the days close to the waxing and waning quarters, since it is at this time of the lunar cycle when more craters and relief can be distinguished on its surface. During the new moon we cannot observe it due to its darkness and its proximity to the Sun and during the full moon any relief is blurred, since the moon is being illuminated “from above” and the shadows disappear from its surface.
September equinox
With September also comes change of seasons. In the northern hemisphere we say goodbye to summer and welcome autumn, while in the south they say goodbye to winter to make way for spring. Although we understand the seasons as a climatic continuum in which heat gradually gives way to cold or vice versa, in the astronomical sense the seasons begin and end at a specific minute of a specific day. He september equinox this year will take place, for example, the September 23 at 8 hours and 50 minutes Spanish peninsular time. Autumn will begin at exactly that time in Spain.
The seasons are caused by tilt of the earth’s axis of rotation. During the summer, the corresponding hemisphere points towards the Sun, while during the winter it points in the opposite direction. Specifically, these seasons begin on the day that the hemisphere points exactly to the Sun or exactly in the opposite direction. If we projected the circle defined by the terrestrial equator, during the summer we would see how the Sun is located on this circle, while in winter it is below it. The equinoxes are nothing more than the precise moment in which the sun crosses the circle, going from being on one side to being on the other. For the northern hemisphere, on September 23, the Sun will pass from being above the celestial equator and will go below. The consequence of this is that the Sun will fall less directly on this hemisphere and will stop heating it as intensely as in summer. In the southern hemisphere the opposite will occur.
opposition of neptune
The day September 19th the planet Neptuneit will be in opposition, that is to say, it will occupy the position diametrically opposite to that of the Sun in the sky. This will be so because on that day the Earth will be “overtaking” Neptune in its orbit around the Sun. will be located at the shortest distance of the entire year on Earth and it will be the perfect time for its observation. However, Neptune is the most distant of the planets in the solar system, so this observation will not be easy. will reach a magnitude about 7.8, so it will not be visible to the naked eye. we will need a modest telescope and a lot of patience to locate it among the countless stars that will surround it. Still it will be worth it.
References:
- Astronomical Agenda: Year 2023 – astronomia.ign.es
