APOD: Solar System Portrait (2017 Feb 11)

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APOD Robot
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APOD: Solar System Portrait (2017 Feb 11)

Post by APOD Robot » Sat Feb 11, 2017 5:12 am

Image Solar System Portrait

Explanation: On Valentine's Day in 1990, cruising four billion miles from the Sun, the Voyager 1 spacecraft looked back one last time to make this first ever Solar System family portrait. The complete portrait is a 60 frame mosaic made from a vantage point 32 degrees above the ecliptic plane. In it, Voyager's wide angle camera frames sweep through the inner Solar System at the left, linking up with gas giant Neptune, the Solar System's outermost planet, at the far right. Positions for Venus, Earth, Jupiter, Saturn, Uranus, and Neptune are indicated by letters, while the Sun is the bright spot near the center of the circle of frames. The inset frames for each of the planets are from Voyager's narrow field camera. Unseen in the portrait are Mercury, too close to the Sun to be detected, and Mars, unfortunately hidden by sunlight scattered in the camera's optical system. Closer to the Sun than Neptune at the time, small, faint Pluto's position was not covered.

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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by Boomer12k » Sat Feb 11, 2017 6:33 am

Interesting...

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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by alter-ego » Sat Feb 11, 2017 6:33 am

APOD Robot wrote: ...Unseen in the portrait are Mercury, too close to the Sun to be detected, and Mars, unfortunately hidden by sunlight scattered in the camera's optical system.
Although hidden by optical scatter, visibility is probably not reduced due to a non-uniform scatter background.

Edited
It turns out the angular separations of both Mars and Earth from the Sun are nearly the same (Mars is a tad bit more), I guess the optical glare/scatter due proximity to the Sun are also pretty close (Mars should be located near the center of the adjacent blank frame containing the Sun). Primarily, I'd say the phase of Mars wrt Voyager and its albedo are probably the major contributors its lack of visibility. Unlike Earth which is about 50% 56% illuminated wrt Voyager, Mars is only 10% to 15% 9.8% illuminated. Also, Mars' albedo is ~40% that of Earth. I'd bet these factors push the detection limit close to the background optical scatter existing in those two frames.
Mars from Voyager 1, 14 Feb 1990.JPG
Earth from Voyager 1, 14 Feb 1990.JPG
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Last edited by alter-ego on Sun Feb 12, 2017 1:35 am, edited 1 time in total.
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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by Coil_Smoke » Sat Feb 11, 2017 7:04 am

Rays coming from our star are some of the more interesting things imaged. They appear to converge near the position of Earth. Looks like the Sun should be directly behind Earth and Venus. I am assuming those planets are between the probe and the Sun. How could Earth appear 50% illuminated in either position? Amazing Earth is not lost in solar glare with the blazing sun behind it.

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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by De58te » Sat Feb 11, 2017 12:50 pm

Coil_Smoke wrote:Rays coming from our star are some of the more interesting things imaged. They appear to converge near the position of Earth. Looks like the Sun should be directly behind Earth and Venus. I am assuming those planets are between the probe and the Sun. How could Earth appear 50% illuminated in either position? Amazing Earth is not lost in solar glare with the blazing sun behind it.
I checked the planet positions for that date on fourmilab dot ch, and that matches up to the picture. Jupiter being the only planet on the far side of the sun. Earth and Venus were about 90 degrees to the left of the sun given them a quarter lit view, Uranus and Neptune were on the right given that Voyager 2 had just left Neptune about half a year earlier., they don't orbit so fast so would still be in half view. Mars however was directly in front of the sun, so you would only see its dark night side in front of the blazing sun. No wonder they didn't capture Mars.

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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by bls0326 » Sat Feb 11, 2017 2:15 pm

" small, faint Pluto's position was not covered. "

Pluto left out of the family portrait, then kicked out of the planet family a decade or so later.

Brian

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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by neufer » Sat Feb 11, 2017 2:48 pm

SSP1.jpg
SSP2.jpg
De58te wrote:
Coil_Smoke wrote:
Rays coming from our star are some of the more interesting things imaged. They appear to converge near the position of Earth. Looks like the Sun should be directly behind Earth and Venus. I am assuming those planets are between the probe and the Sun. How could Earth appear 50% illuminated in either position? Amazing Earth is not lost in solar glare with the blazing sun behind it.
I checked the planet positions for that date on fourmilab dot ch, and that matches up to the picture. Jupiter being the only planet on the far side of the sun. Earth and Venus were about 90 degrees to the left of the sun given them a quarter lit view, Uranus and Neptune were on the right given that Voyager 2 had just left Neptune about half a year earlier., they don't orbit so fast so would still be in half view. Mars however was directly in front of the sun, so you would only see its dark night side in front of the blazing sun. No wonder they didn't capture Mars.
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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by DavidLeodis » Sun Feb 12, 2017 2:38 pm

The information brought up through the 'Voyager Project' link in the credit includes the distance of Voyager 1 and 2 from the Sun and Earth. As I would have expected both are getting further from the Sun, but to my surprise while Voyager 2 is getting further from the Earth that is not the case for Voyager 1 as it is getting nearer the Earth (at least when I just used the link). :?

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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by rstevenson » Sun Feb 12, 2017 2:41 pm

DavidLeodis wrote:The information brought up through the 'Voyager Project' link in the credit includes the distance of Voyager 1 and 2 from the Sun and Earth. As I would have expected both are getting further from the Sun, but to my surprise while Voyager 2 is getting further from the Earth that is not the case for Voyager 1 as it is getting nearer the Earth (at least when I just used the link). :?
I think it would be more accurate to say the Earth is getting nearer to it, as the Earth orbits the Sun. After a while we'll be getting further away again. At this point, it's really only useful to think about how far the Voyagers are from the Sun.

Rob

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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by DavidLeodis » Mon Feb 13, 2017 1:20 pm

rstevenson wrote:
DavidLeodis wrote:The information brought up through the 'Voyager Project' link in the credit includes the distance of Voyager 1 and 2 from the Sun and Earth. As I would have expected both are getting further from the Sun, but to my surprise while Voyager 2 is getting further from the Earth that is not the case for Voyager 1 as it is getting nearer the Earth (at least when I just used the link). :?
I think it would be more accurate to say the Earth is getting nearer to it, as the Earth orbits the Sun. After a while we'll be getting further away again. At this point, it's really only useful to think about how far the Voyagers are from the Sun.

Rob
Thanks for that help Rob :).

PS. I see that the Earth is currently still getting nearer to Voyager 1 :wink:.

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Re: APOD: Solar System Portrait (2017 Feb 11)

Post by rstevenson » Mon Feb 13, 2017 2:34 pm

DavidLeodis wrote:PS. I see that the Earth is currently still getting nearer to Voyager 1 :wink:.
The gravity of the situation is overwhelming.

Rob