Blog
Night Sky: August 2019
2nd The, α (Alpha) Capricornid meteor shower (figure 1 & 2) reaches maximum rate of activity. Some shooting stars associated with the shower are expected to be visible each night until 20th August.
The radiant of the shower will appear 26° above Southern horizon at midnight. It will only be likely to see approximately 2 meteors per hour, since the radiant will be low in the sky, reducing the chance of seeing more meteors.
The Moon will be 1 day old at time of peak activity, presenting minimal interference.
Figure 1: α (Alpha) Capricornid meteor shower.
Figure 2: α (Alpha) Capricornid meteor shower.
13th Will see the Perseid meteor shower (figure 3 & 4) reaching maximum activity. Some shooting stars associated with the shower are expected to be visible each night until 20th August.
The radiant will appear 35° above North Eastern horizon at midnight. Approximately 46 meteors per hour may be seen, since the radiant will be high in the sky, maximising the chance of viewing.
The best place to look is not at the radiant, but at any dark patch of sky approximately 30–40° away from it. It will be at this distance from the radiant meteors will show reasonably long trails without being too spread out.
Figure 3: Perseid meteor shower occurs when the Earth passes through a stream of dust from the Comet Swift-Tuttle, as shown in this orbit diagram.
Figure 4: Location of Perseid radiant.
21st α (Alpha) Cygnid meteor shower (figure 5) will reach maximum activity. Some shooting stars are expected to be visible each night between July and August.
The radiant will appear 68° above Eastern horizon at midnight. Approximately 4 meteors per hour may be seen, since the radiant will be high in the sky, maximising the chance of observing meteors.
Figure 5: α (Alpha) Cygnid meteor shower location.
The Moon will be 20 days old at peak activity, presenting significant interference in the pre-dawn sky.
The best place to look is at any dark patch of sky approximately 30–40° away from the radiant. It is at this distance from the radiant that meteors will show reasonably long trails without being too spread out.
30th The Moon will reach closest point (perigee) along its orbit to the Earth and will appear slightly larger than at other times (figure 6).
The Moon's distance from Earth varies because its orbit is not perfectly circular, it is slightly oval-shaped, tracing out a path called an ellipse.
As the perigee will occur close to the time of new moon, the moon will appear as no more than a thin crescent.
As the Moon traverses this elliptical path around the Earth each month, its distance varies by approximately 10%, between 363000 km and 405000 km. Its angular size also varies by the same factor and its brightness also changes, though this is difficult to detect in practice, given the Moon's phases are changing at the same time.
Figure 6: The moon’s orbit around Earth is not a circle, but it is very nearly circular, as the above diagram shows. Diagram by Brian Koberlein.
WARNING: Never attempt to view through binoculars, telescope or any optical aid an object close to the Sun. Also, never attempt to view the Sun unaided, doing so may result in immediate and permanent blindness. Always use astronomical approved viewing equipment.
The Stellarium software will assist greatly in locating objects in the sky.
Mark R Smith FRAS
Physicist
Nuclear Fusion & Astrophysics.