Triplet of astronomical events for
21 December
and, with the
winter solstice
which is also the
shortest day of the year
and greets a phenomenon that has not been observed for about 400 years:
Jupiter and Saturn
as close as they were only in
1623
, when Galileo and Kepler were still alive.
The conjunction of the two planets was probably the Christmas 'star' which, according to the Gospels, would have guided the Magi.
The
solstice
is scheduled for
11.02
am
Italian time
and marks the beginning of winter.
On this day "the Sun in its apparent movement along the ecliptic, that is the projection of the Earth's orbit into the sky, reaches the southernmost position with respect to the celestial equator, which is the projection of the terrestrial equator into the sky "explains astrophysicist Gianluca Masi, head of the Virtual Telescope.
"This means - he continues - that on the day of the winter solstice the arc corresponding to the path of the Sun above our boreal horizon is the most modest of the year and, consequently, gives us
the longest night
" .
The solstice is greeted by the rare
conjunction between Jupiter and Saturn
, which are so close that they can be observed together in the field of a telescope.
Of course it is an apparent approach, visible from Earth.
The phenomenon could be the
Christmas star of
the Gospels: "in 7 BC - explained Masi - the conjunction between the two planets even took place three times and it was Kepler who suggested that the Magi were inspired by it, also because the duration of the triple conjunction takes months and this is compatible with the organization of a long journey, while other phenomena, such as a comet, have a more modest window of visibility ".
Furthermore, in the Gospels there is no mention of a comet but of a star.
Giotto
continued to give her the 'dress' of a comet
: "frescoing the scene of the Adoration of the Magi in the Scrovegni chapel, he depicted a beautiful comet, with great likelihood because he himself had seen the comet pass of Halley and was evidently inspired by that vision ".
The conjunction between Jupiter and Saturn is a
sight not to be missed
and
to better observe it,
Paolo Volpini, of the Italian Amateur Astronomers Union (Uai) recommends "waiting for the sun to set and looking in that direction. Around 5.00 pm you can begin to see the two very close planets. The highlight is expected
between 5.30 pm and 6.30 pm on December 21.
It is important to look for a place with
a free South West horizon
. The phenomenon is visible to the eye naked, but with a small telescope it is possible to see the rings of Saturn and the moons of Jupiter ".