The autumn constellations are rising: You can then see our neighboring galaxy Andromeda. And in September, bright planets appear: at the end of the month, Jupiter faces the Sun.
Stuttgart – In the last few months, the evening sky has been emptied of bright planets – now they are gradually appearing.
As soon as darkness falls, the ring-bedecked Saturn can be made out in the constellation of Capricorn in the southeastern sky. The ringed planet is slowly retreating from the morning sky. At the end of September it sets shortly before three o’clock in the morning.
Soon after Saturn, Jupiter appears as a conspicuously bright star on the eastern horizon. On September 26, the giant planet will be directly opposite the sun – i.e. in opposition. In opposition, a star is represented in the firmament throughout the night. In the hour after midnight Jupiter can be seen high in the southern sky. He resides in the faint constellation Pisces. It is fascinating to follow the dance of the four bright Jupiter moons Io, Europa, Ganymede and Callisto from night to night with binoculars. At opposition, Jupiter is 591 million kilometers from Earth. This corresponds to four times the distance between earth and sun. The light from Jupiter travels 33 minutes to Earth.
Jupiter, Mars, Venus
A Jupiter day lasts just under ten hours. Because of its rapid rotation, Jupiter is severely flattened. The planetary disc therefore appears oval in the telescope. Jupiter takes twelve years to orbit the sun once. On the evening of September 11, the still almost full moon can be seen south of the giant planet.
Mars in the constellation of Taurus appears to the northeast late in the evening. At the beginning of the month the reddish planet rises ten minutes after 11 p.m., at the end of September already at 9 p.m. From the 9th Mars passes the orange Aldebaran, the main star of Taurus. During the night of the 16th/17th, the waning crescent moon will pass north of Mars. In the course of the month, the marsh brightness increases significantly.
Venus can still be seen low in the eastern sky in the morning. She slowly withdraws from the morning sky and becomes invisible at the end of September. It will overtake the Sun on October 22 and then appear in the evening sky in December. This completes her change from the morning to the evening star. One will look in vain for Mercury in September.
Neptune and Uranus
Neptune, the planet furthest from the sun in the constellation Aquarius, comes in opposition to the sun on the night of the 16th to the 17th. It is 30 times farther from the sun than Earth. It takes 165 years to go around the sun once. Because of its great distance, it is so faint that it can only be seen with binoculars or a telescope. On the day of opposition Neptune separates 4325 million kilometers from the earth. This corresponds to a light runtime of a good four hours. In a telescope, Neptune appears as a tiny bluish marble.
On the night of the 14th to 15th, the greenish planet Uranus will be covered by the waning moon from 11 p.m. to 12:30 a.m. The exact times depend on the location. This event can also only be followed with a telescope.
Full Moon occurs on the 10th at 11:59 am in the constellation Aquarius. Already on the 7th the moon comes close to the earth at 364,492 kilometers, while on the 19th it separates from us at a distance of 404,555 kilometers. New moon is reached five minutes before midnight on the 25th.
The earth binds the moon to itself with its gravity. But the sun also attracts the moon with its enormous mass. However, it is 400 times farther from the moon than Earth. Due to tidal friction, the moon moves four centimeters away from earth every year. The moon is currently 384,400 kilometers away on average.
How far can he get away from us before the sun snatches him from the earth? The US astronomer Georg William Hill (1838 – 1914) asked himself this question. In 1877 he came to the conclusion that if the moon moves more than a million kilometers away from the earth, then we will lose our night star. The area in which the earth can tie up natural and artificial satellites is called the Hill sphere. So there is no risk of losing our moon. It will stay with us for the next billion years.
A look at the evening sky shows: the heavenly chariot has descended to the north-west, the heavenly W, Cassiopeia, but has risen to the north-east. The summer triangle with Wega, Deneb and Atair has meanwhile clearly shifted to the west. Vega is the bright main star of the Lyra, represented by a small but easily recognizable stellar rhombus. Between the two stars remote from Vega you can see a small, round spot of light in the binoculars, which turns out to be a ring in the telescope.
This ring nebula is well known to star friends. Here, an aging star has shed its outer layer of gas, which is expanding further and further into space. What remains is the extremely hot star core. Its intense ultraviolet radiation causes the Ring Nebula to glow. Today we receive the light that this star formation sent out 2200 years ago.
The march of the autumn constellations has begun in the eastern sky. First and foremost is the guiding star of autumn: the star square of Pegasus, also known as the autumn square. At its north-east corner hangs the chain of stars of Andromeda. The hapless Princess Andromeda is rescued by the hero Perseus at the last minute before she can be devoured by the sea monster Ketos. Perseus and Ketos, Cetus in Latin, are also represented as constellations in the autumn sky. In German, Cetus is called a whale. But he is neither a fish nor a whale, but a mythical creature with dagger-sharp teeth and claws.
In the Andromeda constellation, the Andromeda galaxy can be seen as an elongated patch of light when the sky is very dark and the air is clear. It is our neighboring Milky Way. Their more than 400 billion suns are 2.5 million light-years away from us.
The Sun changes from the constellation Leo to Virgo in the early hours of the morning on the 17th. On the 23rd it crosses the celestial equator in a southerly direction at exactly 3:04 a.m., the autumn equinox is reached. Day and night arcs of the sun are equal in size on this day. The winter half-year begins with the autumn equinox. dpa