Starship Asterisk*

OK - this is a nice view of Jupiter - but I do not think this is an actual view of it rotating over time. It appears to be a static map of surface detail acquired over several days of imaging that was then mapped onto Jupiter's shape and rendered in a rotating animation. There are at least two seams...

My reason for saying the true growth rate is diametrically 2 ly/yr is to remind people that the only thing that needs to move in a light echo situation is light itself - and the true diametric rate is 2 ly/yr rather than 1 ly/yr. I sure hope this basic point is understood. If its diameter had gone f...

DonMannino is correct. The six Light Year diameter was a typo. The actual diameter of the initial light echo was four LY. The apparent superluminal velocity here was due to multiple light echoes, not from geometry or relativistic effects. Read the Wikipedia entry on light echoes more carefully. (ht...

I am puzzled by the explanation for this photo. If the star became bright in 2002, and the picture was taken in 2004, shouldn't the size of the light echo ring be 4 light years (radius of 2 light years)? The picture explanation says the reflected light ring is 6 light years in diameter. A quick ans...

This isn't a thin, straight, horizontal contrail high up in daylight with the sun overhead shining down. It is a nearly vertical, wide, jagged and multi-segmented rocket contrail after sunset with the sun shining up from below. This makes the shadow a cross between a crepuscular ray and a volumetric...

Hmm - I think you both are missing my main point. The shadow itself was visible over a wide range of locations perpendicular to the "plane" - and those locations all had a great lookin' shadow - but it didn't go right through the center of the moon. The center of a given plane would have t...

Your first thought was correct, zloq: it is the same picture. Huh? Same event, same photographer, same date, same lens, different time, different location, different foreground, different, plume, different shadow -> different (and better) picture. It is perhaps 30-60 seconds later would be my guess...

Thanks for the comments. I think it's a rich image on many levels. For people who are still interested in the topic - I did find more info to take it even further. It turns out, there is another picture credited to the same photographer and at first I thought it was the same picture, but it is very ...

I have gone back and forth on this image, as to how coincidental it is. A key thing is that there are many people with cameras around, so the issue isn't how rare it is for a single person to get this shot - but for *someone* to get it - and that removes a big part of the coincidence caused by the f...

What is the circular light in the upper left of the screen from about 3:20 to 3:25? It can't be something on the Earth itself, since it's keeping pace with the ISS. It almost looks like a spotlight shining from the ISS but I can't imagine that's what it would be. Anyone know? There is something sim...

Where's all the space junk? As I mentioned earlier, you can see several passing satellites at around 1:40. They would need to be in sunlight to show well, and not moving either too slow or too fast in the timelapse. This view is toward the pole and I assume they are far enough away and higher up so...

I think this was nicely done. At 1:40 you can see 4 satellites going by in the sky. At the very end of that section you see something move fast within the band of atmosphere itself. It might just be another fast satellite seen through the atmosphere, and it appears to move faster because it isn't co...

Good catch. The original APOD caption says it is 6,500 light years away and 2,000 across. That would mean it would span a big chunk of the sky from Earth. http://www.spitzer.caltech.edu/images/1949-ssc2008-15a-Spitzer-Reveals-Stellar-Family-Tree- says that the distance is correct at 6,500 light year...

I appreciate that the image is an inverted H-alpha image but nevertheless, to me, "The gradual brightening towards the Sun's edges is caused by increased absorption of relatively cool solar gas and called limb darkening" sentence is still very confusing. The information brought up through...

I suppose the background was masked and excluded from the inversion technique. I wouldn't have suspected that it had been done. Yes - that seems like a possibility - but in other articles on his technique he does consistently mention "inverting" the image. I tried some things in photoshop...

I know there are wavelengths that can make sunspots appear bright - but I also see many H-alpha images where the sunspots are dark. The key issue is - whether the raw data for these images are that way or not. Just google sun and h-alpha and you will see plenty with a dark limb and dark sunspots. He...

I think this is a nice looking rendering and I have seen others by him like it, but it wasn't until I read the caption that I realized something was amiss. Normally the limb is darkened, as alluded to in the caption, but the caption explains its brightening as the result of inverting and false color...

Not a handy one. But I've read several peer reviewed papers on the subject, with a rigorous analysis of the optical characteristics of lens materials and pupil response, and supported by statistical information regarding cataract rates and age of onset. Those papers would have been published in the...

FWIW, we are riding a peak in cataracts (and I made my fortune designing cataract removal instruments, so I'm not complaining <g>) caused by the popularity of sunglasses after the 1940s. For 50 years, people have worn sunglasses that didn't block UV, and this has resulted in the formation of many c...

Yes - it is interesting that features do show up - even though it's abstract. But that's because a generally smooth surface with just a few features on it would have those features mapped locally onto the image - as long as each feature has a unique-ish range and velocity pair of coordinates. As it ...

Yes - my mistake. I got your link mixed up with Brenner, who did the Goldstone observations. Emily writes a blog for the planetary society. Either way - I thought her write up and animated diagram, which you embedded in your response, were pretty good. She didn't specifically say users complained ab...

Yes - there is an inversion process to recover geometry - but you can't do it with just one frame. If you have never seen a frequency/range image of an asteroid - then I don't know what to say. They are the input to the inversion process - and the output is a 3D model - not an image - though once yo...

Perhaps I'm misunderstanding you here. This is not an abstract image with range on one axis and frequency on the other. I think if you study the lower right plot in the link provided by neufer you will get the idea. In that plot, as it is formed, frequency is vertical and range is horizontal. In th...

I don't know about anyone else, but this is pretty counter-intuitive to me. I think the image is really hard to interpret if it's viewed literally as an x/y image - but the figures and text linked to by neufer above are pretty good - especially the plot that gets drawn at the very lower right of th...

It's amazing that that legendary story of Galileo dropping those cannonballs off the Leaning Tower of Pisa didn't permanently ruin science (if not Pisa itself) for all time. (Apparently Galileo was totally unaware of Newton's third law of motion.) I suggest that you petition the White House for NAS...