In this month of October 2020, we have two rather rare events: an opposition from Mars and a “blue” Moon.
On day 1, the Moon reaches the full moon phase. The next day, our satellite and the planet Mars, about 4 degrees apart, are born around 20:00, that is, just after dark. But, over the next few hours, they get closer and closer and, as the sun approaches dawn on the 3rd, the Moon passes less than 1 degree from the planet Mars.
As our planet is closer to the Sun, it takes less time than Mars to complete its orbit. For this reason, approximately every 2 years and 2 months, the Earth gives you an advance lap.
Of course, this also means that Earth and Mars reach the point of closest approximation between them – the perigee. The next takes place on the 6th, with the two planets "only" 62 million kilometers from each other.
On the 10th, the Moon reaches the waning quarter phase, and on the 13th, the opposition of Mars occurs. This is the day when the Sun, Earth and Mars are perfectly aligned in the Solar System, and, in our sky, Mars appears to be completely opposite the Sun. If the orbits of the two planets were perfectly circular, the perigee and opposition would be coincident, but since the orbit of Mars is a little more elliptical, there is a slight mismatch between the two.
This is also the day that Mars will look brighter in the next 26 months. In fact, for the entire month of October, Mars will be the third brightest object in the night sky (just after the Moon and Venus), a place normally occupied by Jupiter.
On the 14th, a very thin moon, almost new, passes at 4 degrees from the planet Venus, with the two stars rising around 5 in the morning. The 16th is the day of the new moon.
On the 22nd, the Moon passes less than 3 degrees from Jupiter and the two make a triangle with Saturn, at 5 degrees from the Moon. On the 23rd, it reaches the crescent phase.
Two days later it's time to get out of summer time and go back to the hour closest to true solar time for our country. This 25th day will last 25 hours, because, at 2 am in mainland Portugal and Madeira, and at XNUMX am in the Azores, we will set the clocks back one hour. Take the opportunity to catch up on sleep.
On the 29th, the Moon passes 3 degrees from Mars.
And on the 31st, the second full moon of this month occurs. When there are two full moons in a single month, the second is popularly known as the “Blue” Moon. But let's be clear that the Moon won't even change color!
As our satellite takes 29 and a half days to go from one full moon to the next, a Blue Moon can only happen when the first full moon is on the 1st or 2nd of the month (and never in February), which on average occurs every 33 months.
Author Ricardo Cardoso Reis (Porto Planetarium and Institute of Astrophysics and Space Sciences)
Science in the Regional Press – Ciência Viva
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