by rstevenson » Mon Nov 17, 2014 2:39 pm
It's so very rare that I dislike an APOD that I must analyse why I dislike this one so much. I think it's the almost cartoonish scale of the planets that is the problem. But what does the math say? ...
Following the link from the other thread to the original article, I find this illustration of that stellar system...
As you can see, those planets are supposed to be somewhere between about 7 AUs to 70 AUs from the star. An AU (Astronomical Unit) is about 150,000,000 km, so the planets are somewhere between 1.05 x 10^8 km and 1.05 x 10^9 km from the star.
The planets themselves are described in the article as possibly being 5 to 7 times the mass of Jupiter. Mass and size are tricky to relate for gas giants, since increased mass won't necessarily mean a similar increase in size, due to compression of the gases. So I think I'll just go with a bit more than Jupiter-sized, which gives us a diameter of about 1.5 x 10^5 km. So the planets should appear to be very roughly 1/700 to 1/7000 of the width of the dust gap in size. Of course, the artist can't very well illustrate them that size, because they'd be at most a single pixel on screen, but making them look like Christmas tree decorations floating in a whirlpool isn't a good option either.
I think, in this case, it would have been a more honest representation of our current state of knowledge to just make them small dots, say a few pixels wide, just barely big enough to indicate where they were perhaps orbitting, and leave off the entirely conjectural ring systems. After all, the main story is the double dust ring itself, and that's certainly worthy of a serious illustration.
Rob
It's so very rare that I dislike an APOD that I must analyse why I dislike this one so much. I think it's the almost cartoonish scale of the planets that is the problem. But what does the math say? ...
Following the link from the other thread to the original article, I find this illustration of that stellar system...
[attachment=0]hd95086_schem_horizontal_white.jpg[/attachment]
As you can see, those planets are supposed to be somewhere between about 7 AUs to 70 AUs from the star. An AU (Astronomical Unit) is about 150,000,000 km, so the planets are somewhere between 1.05 x 10^8 km and 1.05 x 10^9 km from the star.
The planets themselves are described in the article as possibly being 5 to 7 times the mass of Jupiter. Mass and size are tricky to relate for gas giants, since increased mass won't necessarily mean a similar increase in size, due to compression of the gases. So I think I'll just go with a bit more than Jupiter-sized, which gives us a diameter of about 1.5 x 10^5 km. So the planets should appear to be very roughly 1/700 to 1/7000 of the width of the dust gap in size. Of course, the artist can't very well illustrate them that size, because they'd be at most a single pixel on screen, but making them look like Christmas tree decorations floating in a whirlpool isn't a good option either.
I think, in this case, it would have been a more honest representation of our current state of knowledge to just make them small dots, say a few pixels wide, just barely big enough to indicate where they were perhaps orbitting, and leave off the entirely conjectural ring systems. After all, the main story is the double dust ring itself, and that's certainly worthy of a serious illustration.
Rob