APOD: Phases of Venus (2017 Mar 17)

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APOD: Phases of Venus (2017 Mar 17)

Postby APOD Robot » Fri Mar 17, 2017 4:06 am

Image Phases of Venus

Explanation: Just as the Moon goes through phases, Venus' visible sunlit hemisphere waxes and wanes. This composite of telescopic images illustrates the steady changes for the inner planet, seen in the west as the evening star, as Venus grows larger but narrows to a thin crescent from December 20, 2016 through March 10. Gliding along its interior orbit between Earth and Sun, Venus grows larger during that period because it is approaching planet Earth. Its crescent narrows, though, as Venus swings closer to our line-of-sight to the Sun. Closest to the Earth-Sun line but passing about 8 degrees north of the Sun on March 25, Venus will reach a (non-judgmental) inferior conjunction. Soon after, Venus will shine clearly above the eastern horizon in predawn skies as planet Earth's morning star.

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heehaw

Re: APOD: Phases of Venus (2017 Mar 17)

Postby heehaw » Fri Mar 17, 2017 9:23 am

How disappointing it is, that there is extremely close to zero water in the atmosphere of Venus. So beautiful hanging in the morning or evening sky, and yet sterile forever. And there are probably billions of "Venuses" in our galaxy. And Marses. But our one Earth does not mean that there are billions of Earths in our galaxy or in any galaxy: the fact that there is one in our solar system means nothing because we are on it and wouldn't exist if it didn't exist. And our Moon suggests the possibility that Earths are rare indeed: maybe we're a one-off. Maybe that's why we've not detected radio messages from other civilizations in our galaxy: perhaps there are none.
We'll never colonize Venus. We'll never colonize Mercury. We'll never ... Mars may have underground aquifers! Sounds good? Do you know how much water we humans use per capita daily? Antarctic at least has plenty of water, and you see how its population has grown with time. How much does it cost to send colonists to Antarctica? Where can I sign up?
Message: Earth rocks!

heehaw

Re: APOD: Phases of Venus (2017 Mar 17)

Postby heehaw » Fri Mar 17, 2017 9:26 am

http://epod.usra.edu/blog/ It's a small world!

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby BDanielMayfield » Fri Mar 17, 2017 12:52 pm

heehaw wrote:How disappointing it is, that there is extremely close to zero water in the atmosphere of Venus. So beautiful hanging in the morning or evening sky, and yet sterile forever. And there are probably billions of "Venuses" in our galaxy. And Marses. But our one Earth does not mean that there are billions of Earths in our galaxy or in any galaxy: the fact that there is one in our solar system means nothing because we are on it and wouldn't exist if it didn't exist. And our Moon suggests the possibility that Earths are rare indeed: maybe we're a one-off. Maybe that's why we've not detected radio messages from other civilizations in our galaxy: perhaps there are none.
We'll never colonize Venus. We'll never colonize Mercury. We'll never ... Mars may have underground aquifers! Sounds good? Do you know how much water we humans use per capita daily? Antarctic at least has plenty of water, and you see how its population has grown with time. How much does it cost to send colonists to Antarctica? Where can I sign up?
Message: Earth rocks!


What a pessimistic tone heehaw. The Rare Earth view, in a nutshell, from a ... No ! The Rare Earth hypothesis actually does fit observations to date, but many dispute it out of wishful thinking, imo. Supporters of the Rare Earth idea, even though it does fit facts and it does help explain things like the Fermi paradox are dismissed as nuts.

I myself also wish that really Earthlike planets were common, but reality doesn't care about our wishes.

But you ended on a high note heehaw. Yes, the Earth does rock! We need to take care of it.

Bruce
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Re: APOD: Phases of Venus (2017 Mar 17)

Postby neufer » Fri Mar 17, 2017 1:36 pm

heehaw wrote:
How disappointing it is, that there is extremely close to zero water in the atmosphere of Venus.
So beautiful hanging in the morning or evening sky, and yet sterile forever.

    It wasn't always that way; it's probably just a phase she's going through.
https://en.wikipedia.org/wiki/The_Birth_of_Venus wrote:
<<The Birth of Venus (Italian: Nascita di Venere) is a painting by Sandro Botticelli generally thought to have been made in the mid 1480s. It depicts the goddess Venus, having emerged from the sea as an adult woman, arriving at the shore. The painting is in the collection of the Uffizi Gallery in Florence.

The iconography of The Birth of Venus is similar to a description of the event (or rather, a description of a sculpture of the event) in a poem by Angelo Poliziano, the Stanze per la giostra. No single text provides the precise imagery of the painting, however, which has led scholars to propose many sources and interpretations.

For Plato – and so for the members of the Florentine Platonic Academy – Venus had two aspects: she was an earthly goddess who aroused humans to physical love or she was a heavenly goddess who inspired intellectual love in them. Plato further argued that contemplation of physical beauty allowed the mind to better understand spiritual beauty. So, looking at Venus, the most beautiful of goddesses, might at first raise a physical response in viewers which then lifted their minds towards the godly. A Neoplatonic reading of Botticelli's Birth of Venus suggests that 15th-century viewers would have looked at the painting and felt their minds lifted to the realm of divine love.

Another interpretation of the Birth of Venus is provided here by its author, Charles R. Mack. According to his reading of the painting, the scene was inspired by the text in a Homeric hymn published in Florence in 1488 by the Greek refugee Demetrios Chalkokondyles:

    Of august gold-wreathed and beautiful
    Aphrodite I shall sing to whose domain
    belong the battlements of all sea-loved
    Cyprus where, blown by the moist breath
    of Zephyros, she was carried over the
    waves of the resounding sea on soft foam.
    The gold-filleted Horae happily welcomed
    her and clothed her with heavenly raiment
.
Art Neuendorffer

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby Guest » Fri Mar 17, 2017 1:50 pm

I wonder at which point in its cycle does Venus appear the brightest from earth.

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby neufer » Fri Mar 17, 2017 2:20 pm

Guest wrote:
I wonder at which point in its cycle does Venus appear the brightest from earth.
http://www.nakedeyeplanets.com/venus.htm wrote:
    February 18, 2017 : apparent magnitude = -4.5
(approximately half way between Greatest Elongation & Inferior Conjunction)
Art Neuendorffer

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby rstevenson » Fri Mar 17, 2017 2:33 pm

BDanielMayfield wrote:... The Rare Earth hypothesis actually does fit observations to date, but many dispute it out of wishful thinking, imo. Supporters of the Rare Earth idea, even though it does fit facts and it does help explain things like the Fermi paradox are dismissed as nuts. ...

The Rare Earth hypothesis, like any other hypothesis arguing the point one way or the other, has so little data available to support or refute it that the discussion is nearly pointless. Not even our recent successes in identifying exo-planets is helpful, since the ones we can easily identify occur around smaller less bright stars -- like the recent 7-planet announcement -- or they're incredibly large and close to their star, like most of the others. And all of them are in our immediate neighbourhood within the Milky Way, and therefore shouldn't be assumed to be a representative sample.

We'll just have to wait -- perhaps for quite a long time -- to see whether Earth is truly rare.

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby Whiskybreath » Fri Mar 17, 2017 2:43 pm

I'm just glad that someone else does all the mathematics.

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby neufer » Fri Mar 17, 2017 2:49 pm

rstevenson wrote:
BDanielMayfield wrote:
... The Rare Earth hypothesis actually does fit observations to date, but many dispute it out of wishful thinking, imo. Supporters of the Rare Earth idea, even though it does fit facts and it does help explain things like the Fermi paradox are dismissed as nuts. ...

The Rare Earth hypothesis, like any other hypothesis arguing the point one way or the other, has so little data available to support or refute it that the discussion is nearly pointless. Not even our recent successes in identifying exo-planets is helpful, since the ones we can easily identify occur around smaller less bright stars -- like the recent 7-planet announcement -- or they're incredibly large and close to their star, like most of the others. And all of them are in our immediate neighbourhood within the Milky Way, and therefore shouldn't be assumed to be a representative sample. We'll just have to wait -- perhaps for quite a long time -- to see whether Earth is truly rare.
https://en.wikipedia.org/wiki/Ytterby wrote:
Click to play embedded YouTube video.

<<Ytterby (Swedish: "outer village") is a village on the Swedish island of Resarö, in Vaxholm Municipality in the Stockholm archipelago. At a quarry and mine near the village, the rare earth mineral yttria was discovered and named after the village. This crude mineral eventually proved to be the source of four new elements that were named after the mineral ore and the village. These elements are yttrium (Y), erbium (Er), terbium (Tb), and ytterbium (Yb) and were first described in 1794, 1842, 1842, and 1878, respectively. In addition, three other lanthanides, holmium (Ho, named after Stockholm), thulium (Tm, named after Thule, a mythic analog of Scandinavia), and gadolinium (Gd, after the chemist Johan Gadolin) can trace their discovery to the same quarry making it the location with most elements named after it.

Despite their name, rare earth elements are – with the exception of the radioactive promethium – relatively plentiful in Earth's crust, with cerium being the 25th most abundant element at 68 parts per million, or as abundant as copper. They are not especially rare, but they tend to occur together in nature and are difficult to separate from one another. However, because of their geochemical properties, rare earth elements are typically dispersed and not often found concentrated as rare earth minerals in economically exploitable ore deposits.>>
Art Neuendorffer

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby CURRAHEE CHRIS » Fri Mar 17, 2017 3:29 pm

This was a very helpful picture/chart as it allowed me to understand what I have been seeing with Venus (and also through explanations from Ann :))
Thank you APOD!!!

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby Chris Peterson » Fri Mar 17, 2017 3:39 pm

heehaw wrote:How disappointing it is, that there is extremely close to zero water in the atmosphere of Venus. So beautiful hanging in the morning or evening sky, and yet sterile forever. And there are probably billions of "Venuses" in our galaxy. And Marses. But our one Earth does not mean that there are billions of Earths in our galaxy or in any galaxy: the fact that there is one in our solar system means nothing because we are on it and wouldn't exist if it didn't exist. And our Moon suggests the possibility that Earths are rare indeed: maybe we're a one-off. Maybe that's why we've not detected radio messages from other civilizations in our galaxy: perhaps there are none.
We'll never colonize Venus. We'll never colonize Mercury. We'll never ... Mars may have underground aquifers! Sounds good? Do you know how much water we humans use per capita daily? Antarctic at least has plenty of water, and you see how its population has grown with time. How much does it cost to send colonists to Antarctica? Where can I sign up?
Message: Earth rocks!

It is beyond reason to believe that we are singular. No matter how statistically rare Earth's might be (and realistically, do we need anything close to Earth to actually develop life?), it is certain beyond reasonable doubt that there must still be billions of planets very similar to Earth in the Universe.

(Humans need very little water; many of us use if profligately because we have it in such abundance. Look at how it's used- and reused- on the ISS to see what is possible.)
Chris

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Larry Keohn

Re: APOD: Phases of Venus (2017 Mar 17)

Postby Larry Keohn » Fri Mar 17, 2017 7:04 pm

Animation of Venus in the morning sky from March 25th to December 2nd https://youtu.be/KfbfNpc08u8

heehaw

Re: APOD: Phases of Venus (2017 Mar 17)

Postby heehaw » Fri Mar 17, 2017 8:30 pm

Chris Peterson wrote: .... there must still be billions of planets very similar to Earth in the Universe.

If the universe is infinite (which it may well be) then there are, in fact, infinitely many planets almost identical to Earth, even to having copies of me typing this message or variations on it such as @&$%# or happy brillig!

Fernangarc54

Re: APOD: Phases of Venus (2017 Mar 17)

Postby Fernangarc54 » Fri Mar 17, 2017 8:47 pm

This beautiful sequence lacks one piece of information: Can you tell us the apparent brightness of Venus at each moment in the sequence? Closer is brighter, but wane shows less area.
Thanks!

Catalina

Re: APOD: Phases of Venus (2017 Mar 17)

Postby Catalina » Fri Mar 17, 2017 9:11 pm

There is more information on the brightness of Venus and its relationship to distance from the Earth and Sun as well as % of illumination on today's Earth Science Picture of the Day site: http://epod.usra.edu/

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby rstevenson » Sat Mar 18, 2017 1:51 am

heehaw wrote:If the universe is infinite (which it may well be) then there are, in fact, infinitely many planets almost identical to Earth, ...

I've seen that argument or very similar arguments probably hundreds of times in my life. Yet there's always been something about it that bugs me. Can it really be true? Here are two things that are problematic about it, I think...

1. It's usually stated as a fact, as you did here, but how could anyone of finite intelligence verify it? Not possible, of course, so it cannot be seen as a fact. A weak supposition, or perhaps even a strong one, but not a fact.

2. If we were to try to measure all aspects of the Earth including all the aspects of its natal cloud and all the coincidental events that went in to making it, then added in all the tiny events that combined to produce life and then to produce mammalian life and then intelligent (more or less) life, would we not have an infinitude of factors and possible combinations of factors? And is that infinitude any less than the putative infinitude of the universe? In other words, stating unequivically that there is an identical Earth, even down to an identical you on it, suggests that all these factors that went into making it and you are not themselves just one discreet outcome of an infinitude of possibilities.

I would say that even given an inifinite universe, there is only one of you, one of me, and one Earth in it. And speaking only for myself, one is most certainly enough.

Rob

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby Chris Peterson » Sat Mar 18, 2017 4:55 am

rstevenson wrote:
heehaw wrote:If the universe is infinite (which it may well be) then there are, in fact, infinitely many planets almost identical to Earth, ...

I've seen that argument or very similar arguments probably hundreds of times in my life. Yet there's always been something about it that bugs me. Can it really be true? Here are two things that are problematic about it, I think...

1. It's usually stated as a fact, as you did here, but how could anyone of finite intelligence verify it? Not possible, of course, so it cannot be seen as a fact. A weak supposition, or perhaps even a strong one, but not a fact.

Well, I think you could make an extremely strong case for the supposition given the "almost" qualification he used. It might even be mathematically provable that given an infinite number of planets, there will be an infinite number that approach being the same as Earth. I also think it might be mathematically provable that none would be identical, either to Earth or each other.

I would say that even given an inifinite universe, there is only one of you, one of me, and one Earth in it. And speaking only for myself, one is most certainly enough.

In an infinite universe, there is probably only one of anything. That's not to say there's not something very, very similar to each of us out there. I rather doubt that the Universe is infinite, however, so that means there's likely not even anything close.
Chris

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby Ann » Sat Mar 18, 2017 5:44 am

Chris Peterson wrote:
rstevenson wrote:
heehaw wrote:If the universe is infinite (which it may well be) then there are, in fact, infinitely many planets almost identical to Earth, ...

I've seen that argument or very similar arguments probably hundreds of times in my life. Yet there's always been something about it that bugs me. Can it really be true? Here are two things that are problematic about it, I think...

1. It's usually stated as a fact, as you did here, but how could anyone of finite intelligence verify it? Not possible, of course, so it cannot be seen as a fact. A weak supposition, or perhaps even a strong one, but not a fact.

Well, I think you could make an extremely strong case for the supposition given the "almost" qualification he used. It might even be mathematically provable that given an infinite number of planets, there will be an infinite number that approach being the same as Earth. I also think it might be mathematically provable that none would be identical, either to Earth or each other.

I would say that even given an inifinite universe, there is only one of you, one of me, and one Earth in it. And speaking only for myself, one is most certainly enough.

In an infinite universe, there is probably only one of anything. That's not to say there's not something very, very similar to each of us out there. I rather doubt that the Universe is infinite, however, so that means there's likely not even anything close.


I'm absolutely convinced that there is nothing like us out there. Let me put it like this: if we could somehow rewind history and make the Earth start its history from scratch, it would turn into something quite different from what we see around us today. And I'm personally convinced that evolution on the Earth wouldn't produce Homo Sapiens from scratch a second time. Of course, just because I think so doesn't make it true!

But Chris, you said that you rather doubt that the universe is infinite. What exactly do you mean? If our universe isn't infinite, does that mean that it is finite? Some people would say that a finite universe is closed, and it is going to end in a Big Crunch. Is that what you mean? Or do you mean that the universe most likely isn't going to end in a Big Crunch, but it is finite anyway?

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby neufer » Sat Mar 18, 2017 11:43 am

Ann wrote:
I'm absolutely convinced that there is nothing like us out there. Let me put it like this: if we could somehow rewind history and make the Earth start its history from scratch, it would turn into something quite different from what we see around us today. And I'm personally convinced that evolution on the Earth wouldn't produce Homo Sapiens from scratch a second time.
http://www.phrases.org.uk/meanings/star ... ratch.html wrote:
Image
<<Boxing, golf, cricket and also any sport that involves some form of race use lines on the ground as part of their regulations and historians of each sport encourage the belief that their 'scratch' was the first. Cricket has the strongest claim. Everyone who ever played cricket as a child will be familiar with the batting and bowling 'creases' and will have scratched them on the ground to mark out the pitch. The first time that such a 'scratch' is referred to in print is in a cricketing manual - John Nyren's Young Cricketer's Tutor, 1833, which records this line from a 1778 work by Cotton: "Ye strikers... Stand firm to your scratch, let your bat be upright."

The expression 'start from scratch' came about in 'handicap' races where weaker entrants were given a head start. Other sports, notably golf, have taken up the figurative use of 'scratch' to mean 'with no advantage - starting from nothing'. The first person who is recorded as 'starting from scratch' was participating in 'pedestrianism' - what we would now call running. The British sporting newspaper The Era reported on a handicap running event in Sheffield in December 1853: The match on the Hyde Park Ground, Sheffield... has already created quite a furore of excitement among the sporting men of the North. The manner in which the men have been handicapped [is]: James Pudney (of Mile-end) and James Sherdon (of Sheffield), start from scratch; John Syddall, six yards; Richard Conway, twelve; John Saville, twenty...>>
https://en.wikipedia.org/wiki/Convergent_evolution wrote:
ImageImage
Two succulent plant genera, Euphorbia and Astrophytum, are only distantly
related, but the species within each have converged on a similar body form
.

<<Convergent evolution is the independent evolution of similar features in species of different lineages. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The cladistic term for the same phenomenon is homoplasy. The recurrent evolution of flight is a classic example, as flying insects, birds, and bats have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are analogous, whereas homologous structures or traits have a common origin but can have dissimilar functions. Bird, bat and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions.

The opposite of convergence is divergent evolution, where related species evolve different traits. Convergent evolution is similar to but different from parallel evolution. Parallel evolution occurs when two independent but similar species evolve in the same direction and thus independently acquire similar characteristics; for instance, gliding frogs have evolved in parallel from multiple types of tree frog.

Many instances of convergent evolution are known in plants, including the repeated development of C4 photosynthesis, seed dispersal by fleshy fruits adapted to be eaten by animals, and carnivory.>>
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Re: APOD: Phases of Venus (2017 Mar 17)

Postby DavidLeodis » Sat Mar 18, 2017 2:01 pm

It's a fascinating set of images of Venus. :clap:

The information on the montage is very interesting, particularly that the distance between Venus and Earth decreased by about 50 million miles over the only about 3 months period covered. In looking up Wikipedia for information about Venus I found this "When Venus lies between Earth and the Sun in inferior conjunction, it makes the closest approach to Earth of any planet at an average distance of 41 million km (25 million mi). The planet reaches inferior conjunction every 584 days, on average. Because of the decreasing eccentricity of Earth's orbit, the minimum distances will become greater over tens of thousands of years. From the year 1 to 5383, there are 526 approaches less than 40 million km; then there are none for about 60,158 years".

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby Chris Peterson » Sat Mar 18, 2017 2:13 pm

Ann wrote:
Chris Peterson wrote:Well, I think you could make an extremely strong case for the supposition given the "almost" qualification he used. It might even be mathematically provable that given an infinite number of planets, there will be an infinite number that approach being the same as Earth. I also think it might be mathematically provable that none would be identical, either to Earth or each other.

I'm absolutely convinced that there is nothing like us out there. Let me put it like this: if we could somehow rewind history and make the Earth start its history from scratch, it would turn into something quite different from what we see around us today. And I'm personally convinced that evolution on the Earth wouldn't produce Homo Sapiens from scratch a second time. Of course, just because I think so doesn't make it true!

We're in complete agreement about that. The question is, what would happen if we rewound history an infinite number of times? The Earth is still only made of a finite number of particles, each of which has a finite number of states. What uncertainties are left? Maybe something related to quantum mechanics. Maybe something related to chaos theory. But it seems very possible to me that rewinding history an infinite number of times would result in versions of Earth at least very similar to our version.

But Chris, you said that you rather doubt that the universe is infinite. What exactly do you mean? If our universe isn't infinite, does that mean that it is finite? Some people would say that a finite universe is closed, and it is going to end in a Big Crunch. Is that what you mean? Or do you mean that the universe most likely isn't going to end in a Big Crunch, but it is finite anyway?

It isn't certain if the Universe is infinite or not. I think the more common view is that it isn't, but theory doesn't provide a clear answer and we don't know how to make an observation that would provide a clue. An infinite universe would be infinite in extent and volume, and probably contain an infinite amount of energy. It could still be expanding just as we observe, that expansion could still be accelerating just as we observe. If the Universe is infinite, then it can't be closed. But it can be open or flat, and the best observational evidence we have puts it very, very close to flat.

Of course, both open and flat universes expand forever, and this is true whether they are infinite or not. I'm not sure if a closed, infinite universe is possible, or what the fate of such a universe would be. Right now there is very strong theoretical and observational evidence against any Big Crunch, regardless of the shape of the Universe.
Chris

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astronut

Re: APOD: Phases of Venus (2017 Mar 17)

Postby astronut » Sat Mar 18, 2017 11:41 pm

based on the chart of venus phase provided here whichis the bightest phase and how would you determine it

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby Ann » Sun Mar 19, 2017 5:26 am

astronut wrote:based on the chart of venus phase provided here whichis the bightest phase and how would you determine it


Venus is brightest when the largest "surface" of it is illuminated, as seen from the Earth.

When Venus is "full", an entire hemisphere of it is bathing in sunlight, as seen from the Earth. Unfortunately that only happens when Venus is on the other side of the Sun from the Earth. When that happens, Venus looks quite small in our skies, and Venus is far from maximum brightness.

So when Venus is full, it is as far away from the Earth as it can be. At that point, Venus is said to be at opposition. After that, Venus approaches us. That is because its orbit is inside the Earth's orbit, and it moves faster than the Earth does.

As Venus approaches us, it first turns gibbous, then "half", then it becomes a crescent. But while only a smaller and smaller part of Venus becomes illuminated, as seen from the Earth, the illuminated part grows larger and larger.

Venus is, as I said, brightest when the illuminated part of it covers the maximum amount of "surface" in our skies. That happens when Venus is a crescent, but not when it is a tremendously thin crescent.

I believe Venus was at its brightest in early or mid February this year. Now, its crescent is growing thinner and thinner. Soon Venus will be "right in front of the Sun", it will show us its unilluminated side only, and we wouldn't be able to see it right in front of the Sun anyway.

In January, February and March, Venus has shown itself in the Earth's evening skies. When Venus returns to our skies after it has been invisible because it was unilluminated and was right in front of the Sun, it will be a morning object.

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Re: APOD: Phases of Venus (2017 Mar 17)

Postby neufer » Sun Mar 19, 2017 12:33 pm

Ann wrote:
I believe Venus was at its brightest in early or mid February this year. Now, its crescent is growing thinner and thinner. Soon Venus will be "right in front of the Sun", it will show us its unilluminated side only, and we wouldn't be able to see it right in front of the Sun anyway.
neufer wrote:
http://www.nakedeyeplanets.com/venus.htm wrote:
Venus was at its brightest (apparent magnitude = -4.5) on February 18, 2017
(approximately half way between Greatest Elongation & Inferior Conjunction).
Art Neuendorffer


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