August starts with the full moon on the 2nd, and on the 9th it reaches the waning quarter. Continuing its monthly journey through the sky, on the 12th it passes very close to the planet Jupiter (at 3 degrees away), with both being born around 2 am.
Also on the 12th the maximum of the Perseid star shower occurs. This owes its name to the constellation Perseus, where the radiant is located – the central point from which all meteors seem to emanate. The constellation is made up of dim stars, which are difficult to see in a city.
Although the Perseid peak is forecast after midday, this rain usually has bright meteors. So, and especially in dark skies, it should be worth waking up before (or going to bed after) sunrise, to see a few crossing the sky. At most, around 100 meteors are predicted per hour.
On the 15th Venus rises around 3 am, and reaches its greatest elongation – the farthest point in the sky from the Sun.
On the 17th, New Moon day, Mars and Saturn will be just 3 degrees away, with the Moon joining them on the 22nd. them can be difficult.
On the 24th, the Moon reaches the fourth crescent and a week later, on the last day of August, the second Full Moon of the month – a Blue Moon. This is an unusual event, as it is only every 2 or 3 years that there is a month with two Full Moons – the second is called the Blue Moon. The next Blue Moon will be on the 31st of July 2015.
Finally, I could not fail to clarify the myth that annually announces "on August 27, Mars is the size of the Moon". I want to make it very clear that this is impossible. And the reason I describe below.
The size of an object varies linearly, that is, if something is twice the distance, it looks 2 times smaller. As an example, the Sun is 400 times larger than the Moon, but it's 400 times farther away, so in our sky, they appear to be the same size.
Since Mars is twice the size of the Moon, to appear the same size, it would have to be twice the distance, about 760 km from Earth.
But being farther from the Sun than Earth, Mars takes longer to complete an orbit. Therefore, it is only every 26 months that the two planets are “on the same side” of the Sun, at the point of closest approximation to each other.
Even at this point, the minimum possible distance between the two planets is 55 million km, that is, almost 145 times farther than the Moon. This means that, at most, the size of Mars in the sky will be 0,007 times the size of the Moon!
So, whoever is waiting to see “two moons” in the sky, it's better to wait sitting down.
Good remarks!
Author Ricardo Cardoso Reis (CAUP)
Science in the Regional Press – Ciência Viva
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