The full Moon will be partially obscured by Earth’s shadow on September 18, and recent photographs of comet C/2023 A3 Tsuchinshan-ATLAS seem to portend some great sightings this fall.
© Guillaume Cannat
As summer ends and the nights get longer The stars have reserved some beautiful appointments for us in September, in particular with the opposition of the planet Saturn, whose brightness will reach its peak on the 8th and which will reveal its rings in the smallest telescopes, and, above all, a beautiful partial eclipse of the Moon which will slide to the edge of the Earth’s shadow cone during the night of the 17th to the 18th in mainland France. The last total lunar eclipse dates from November 8, 2022 and was not even observable in Europe, so we must take advantage of this “appetizer” which announces to us the two total lunar eclipses that we will be able to enjoy next year . The full moon may seem dazzling to us, but I remind you that observing it is not dangerous, whether with the naked eye or with an optical instrument: binoculars, telescope or spotting scope. So, if the sky is clear enough, do not hesitate to admire this magnificent celestial encounter visible both in town and in the countryside, as it is not disturbed by light pollution.
This partial lunar eclipse will be visible in Europe, Africa, the Antilles and the American continent. In mainland France, the Moon will enter the penumbra zone enclosing the Earth’s shadow on September 18th starting at 02:40 (legal time, universal time + 2 hours); entry into the umbra will begin around 4:10 am, maximum will occur at 4:45 am and the lunar disk will emerge from the umbra at 5:15 am and from the penumbra around 6:45 am. At maximum, the slightly indented full Moon will shine about thirty degrees above the southwestern horizon and, at the end of the penumbra, it will be only ten degrees above the west-southwestern horizon. The Earth’s shadow will be clearly visible to the naked eye as an indentation to the north of the lunar disk, but it will still be too dazzling for us to capture its delicate copper hue. The next total lunar eclipse will take place on March 14, 2025 and will be partially observable in France.
News about comet C/2023 A3 Tsuchinshan-ATLAS
Discovered in early 2023, comet C/2023 A3 Tsuchinshan-ATLAS is expected to pass at its closest point to the Sun (perihelion) on September 27, at a distance of nearly 58 million kilometres. A fortnight later, on October 12, it is expected to pass as close to Earth as possible, still 71 million kilometres away. Taking into account the evolution of its activity since its discovery, astronomers estimate that the brightness of its nucleus could rival that of some of the brightest stars in the celestial vault and that, photographically, its tails of gas and dust could extend more than ten degrees in the evening sky in mid-October, more than the width of a fist at arm’s length; French astrophotographer Nicolas Lefaudeux offers on his site a magnificent work simulating the possible appearance of the tails of this comet. But, as always with a new comet, there is great uncertainty about its behaviour during its closest passage to the Sun because, depending on its size and cohesion, its nucleus could disintegrate at this time, as has happened to many comets in the past.
© Guillaume Cannat
If all goes well, comet C/2023 A3 Tsuchinshan-ATLAS could be observable in the early hours of late September under difficult conditions for European latitudes and, above all, it could become a very beautiful celestial object to observe and photograph in the twilight and night sky after October 10. Telescopic observations made in July and August, especially in the southern hemisphere, and images recently taken by the solar space probe STEREO-A They show that its core is not disintegrating – as some announced a little prematurely in July – that its tail is developing and that the growth of its brightness corresponds for the moment to the predictions. To be continued…
Some views to admire in the September sky.
Moon phases in September
the moon is news on 3 in Leo, in First district on the 11th in Ophiuchus, Completed on the 18th in Aquarius and last quarter on the 24th in Gemini.
The sky in September
In September, astronomical twilight ends less than two hours after sunrise. The Summer Triangle is then clearly visible, high in the sky above the southern horizon. Vega and Deneb follow one another at the zenith and Altaïr points towards the ground. Looking west, the brightness of Arcturus stands out and seems to swing gently under the great parachute of the Bouvier. Higher up, your neck begins to feel stiff! – the arc of the Corona Borealis – where we are still awaiting the explosion of the nova T CrB (see this post) – and the bow tie of Hercules transport you back to Vega. To the northwest, the Big Dipper continues its circumpolar course and the Casserole will be on the northern horizon after midnight. The stars Merak and Dhubé, which serve to find the polar stars in the northern hemisphere, can also lead you to the square of Pegasus on the other side of the sky. Not far from the Eagle, the Dauphin, a very small figure that can be hidden with an outstretched thumb, is a diamond with an extension that fairly well resembles the arched body of a dolphin leaping through the waves. To the northeast, in front of the narrowest part of the Milky Way, are the O of Cassiopeia and the Perseus arc and, in the best places, it is easy to see with the naked eye the oblong spot of the double cluster of stars that separates them, just as one can distinguish the grayish spot of the Andromeda galaxy below Cassiopeia, which descends at an angle towards the east. The entire winter sky now settles into the celestial dome at the edge of dawn and we find the immense Hexagon and the more modest Winter Triangle. Saturn is in opposition and accompanies us all night; Jupiter and Mars rise after midnight and ascend towards the meridian until dawn.
