Starship Asterisk*

"Even though the Moon is above your horizon half of the time" is incorrect. depends on the phase, time of year and location How so? In December in the Northern Hemisphere, the full moon is above the horizon more than half of each day. Similar to the sun in summer. Though the moon can be a...

A much better animation of the contact (101MB): https://svs.gsfc.nasa.gov/vis/a010000/a013700/a013744/A_samcam_approach_and_tag_37x_2.gif (be patient, after the first loop the animation will be quicker and smoother) Great discussion of the event by Scott Manley (12 min): https://youtu.be/cmQfWuFbLNg

This photo would be helpful in any elementary school class, when helping students develop a fundamental understanding of astronomy. Imagine a class making an image like this from scratch, mapping the sun from solstice to solstice. Since the sun moves 0.4 degrees a day at the equinoxes, which is les...

This photo would be helpful in any elementary school class, when helping students develop a fundamental understanding of astronomy. Imagine a class making an image like this from scratch, mapping the sun from solstice to solstice. Since the sun moves 0.4 degrees a day at the equinoxes, which is les...

Trying to infer how far apart the images were taken. The sun images along the equinox path are spaced a little further than one diameter apart. By crude measurement of 49/21 pixels, or 2 and 1/3 diameters apart. The sun averages 32 minutes of arc in the sky so that's 74.7 minutes of arc between imag...

Astronomy Pi of the Day.

Can someone explain x-ray irradiance and why smaller K and M stars give off more than the sun? I remember black body curves and don't understand why a smaller star would give off more. Thanks! I wondered this too. Those X-rays must not be part of the star's thermal radiation . Red dwarfs are known ...

Are all the "big" stars here part of the Milky Way? There's one bright one coincidentally appearing very near the center of M33 ... that's not in M33 right?


Closeup of the center

So the Moon's apparent motion must also be subject to these shifts. Most welcome MarkBour. Yes you're right there must be a diurnal parallax of the moon too. Earth's umbra is a cone 870K miles long (1.4 gigameters) that every nighttime we slip inside of. I'm guessing the brownish circle in the vide...

I think the "intriguing pattern" is formed by virtue of the observer's location on the surface of a spinning Earth over the course of the two or three days straddling the eclipse. That is, it is topocentric, not geocentric. In other words, we're seeing the diurnal parallax of earth's shad...

What makes the view yellowish on the right? Other views of M24 don't show this. What is scattering longer wavelengths?

Infrared reveals...



...Eagle tastes like chicken.

The original animation:

(Click to enlarge)

From the 2-frame animation at europlanet plus a little translation, stretch, and rotate. But no further funny business.

At 0:38 in the video it is neat to watch the Moon move slightly leftward against the starry background, but the Earth's shadow remains fixed.

The "Saros Numbers" hyperlink seems incorrect and does not take one to another webpage ? I was just going to say this. It appears the date is missing a digit. https://apod.nasa.gov/apod/ap17811.html the "Saros numbers" link https://apod.nasa.gov/apod/ap170811.html should be

I've always thought of this nebula as Orion's Kneecap

I'd say "half as close" is a phrase to be avoided. I'm not saying it's great usage. Just that in this context it's obvious what it means. Here Comet Machholz is seen approaching the Sun much closer than Mercury ever does (; or to be specific: "half as close" ). Got it. The comet...

geckzilla wrote:

Chris Peterson wrote: I just meant that one day resolution is all APOD should ever need, but gravitational wave detections may need finer than that.

I still can't tell if we're joking or not.

Some days I wish there were an APOH.

since the ordered field significance allows for logical sorting. It does??? Ann That YYMMDD date code is "monotonic" in the sense that you can compare two codes alphabetically and know which one refers to an earlier time. So "171231" is less than "180101" in the same w...

What a fascinating read, that story Einstein's double reversal , about the changing minds over whether gravitational waves are real or abstract. ...in the end, Einstein had fully accepted the objections that had initially so upset him. And then Feynman's contribution: ...after the introduction of th...

I understand that Smith Rock is toward the south border of the totality zone, but still, how did that make the "diamond ring" appear where it does in the photo? Oh good angle on this question, haha pun intended. Simply by moving laterally one could "put" the diamond ring at any ...

One letter is wrong in the video link, it should be: https://www.youtube.com/watch?v=lgAksIb1NGo

Looking more like a moon and less like a licorice turd:

Explanation: The best known asterism in northern skies, The Big Dipper is easy to recognize , even when viewed upside down, though some might see a plough or wagon . What is this expression “upside down” of which you write? Wouldn't an upside down dipper be one positioned such that it can't hold wa...

Correction to the first link, an article about The Big Dipper from the wayback machine.