Starship Asterisk*

Dawn s Grande Finale

Explanation: After more than a month, the lovely lineup of four naked-eye planets in dawn skies is coming to a close. Still, on May 31st a slender Moon joined the grouping along the eastern horizon for a final celestial performance, presented in this early morning scene from a beach near Buenos Aires, Argentina. A favorable view of the configuration in the southern hemisphere autumn, the photo was taken about 30 minutes before sunrise. In order from bottom to top, wandering Mercury, Venus, Mars, and Jupiter are stretched along the ecliptic plane. The Moon's sunlit crescent is sinking into the colorful twilight glow just left of Mercury. In dawns to come, Mars and Jupiter will continue to rise while Venus and Mercury sink toward the horizon, drawing closer to the rising Sun.

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Oooooh, I like this, image, the slight smile of the moon, text, poem, links -- all of it. What a perfect APOD.

The moon does not sink in the east at dawn. It rises.
Same as the sun.

owlice wrote: ..... the slight smile of the moon .......

Owlice - those words could be a line right out of a poem!


Enjoyed exploring Luis Argerich's website with all the early dawn photos.

Rusty Brown in Canada wrote:The moon does not sink in the east at dawn. It rises.
Same as the sun.

This.

Why are Mercury and Venus not crescents?

rholden wrote:Why are Mercury and Venus not crescents?

Venus's phase is 93% and Mecury's phase is 84%. Even if these objects weren't overexposed and bloated in the image, it wouldn't be all that easy at this image scale to see their slight lack of roundness.

Rusty Brown in Canada wrote:The moon does not sink in the east at dawn. It rises.
Same as the sun.

That depends on your viewpoint. In at least two ways it can reasonably be considered to "sink": since the twilight glow is rising faster than the Moon, the Moon appears to sink into that twilight glow- which is actually what the caption says. Also, since the Moon moves eastward with respect to the fixed background stars, it is said to move eastward- thus, the Moon sinks further east each day of its cycle. Even as it rises in the east and moves towards the western horizon, it is actually moving eastwards in terms of its celestial coordinates.

This photograph shows at top the intense blue sky often seen in Buenos Aires. Last year, while there in March and also in December, on most days, the sky in Buenos Aires often appeared of a noticeable darker, deeper blue than skies normally are at the Northern latitude where I spend most of my time.

In a cursory Web search, I read a bit on the scattering of light in the Web site Hyperphysics http://hyperphysics.phy-astr.gsu.edu/hb ... lusky.html . At one point the explanation says Mie scattering of light (which appears white to us) is absent "...in the particle-free air of the polar regions." Could proximity to the South pole account for the intense blue sky I observed in Buenos Aires?

Thank you a lot for the comments!
I tried and tried to get Mercury and Venus as crescents but it was impossible with the focal length I used.
Happy to be at APOD, it was a great show of conjunctions during May and fighting against the weather was hard.

Chris P: What a great explanation of the apparent movement of the Moon! Your contributions are some of the best. Thanks!!!