Starship Asterisk*

https://apod.nasa.gov/apod/calendar/S_200609.jpg Orion over Argentine Mountains Explanation: Do you recognize the constellation of Orion? It may be harder than usual in today's featured image because the camera has zoomed in on the center, and the exposure is long enough to enhance nebulas beyond w...

Gottit! Black drop effect! https://atoptics.wordpress.com/2013/08/27/the-black-drop-effect-is-not-an-atmospheric-phenomenon/ Cool. Aka "the shadow bridge effect". Despite reading that article I still don't quite understand what's happening optically. Is it just the overlapping fuzziness o...

A ring around Mercury? Really? How is that possible? There is no thick atmosphere on this planet. I'm baffled too. How can Mercury display a ring of fire during its transit of the Sun? Ann Yeah, doesn't make much sense to me either. But I did find this pic that sort of shows an orange ring around m...

If radius is proportional to time back, it looks like at first there was no rotation (outer third), then equal emission in all directions (middle third), and now leisurely rotation (inner third). Is this a correct interpretation? If so, what caused the change in rotation, perhaps asymmetric emissio...

Earth is a product of accretion of particles over a long time. What makes the center of the Earth a fireball? pass the ice cold one Doesn't it have to do with radioactive decay in the large iron/nickel core of the Earth? Ann Yes, plus two other factors. From https://www.scientificamerican.com/artic...

¿Can anyone explain what the spokes are like Japanese parasol rods seen in some images? I don't seek "spokes" in this image of the cat's eye nebula, rather, there seem to be net-like filaments of denser gas. Not sure what causes that - perhaps magnetic fields? Or maybe it's just random de...

I just noticed something odd about the APOD page for this (https://apod.nasa.gov/apod/ap130530.html). If you click on the Discuss link there, it takes you to http://bb.nightskylive.net/asterisk/discuss_apod.php?date=130530, which ends up being a broken link and falls back to a page that proclaims &...

I just noticed something odd about the APOD page for this (https://apod.nasa.gov/apod/ap130530.html). If you click on the Discuss link there, it takes you to http://bb.nightskylive.net/asterisk/discuss_apod.php?date=130530, which ends up being a broken link and falls back to a page that proclaims &q...

Fascinatingly, Comet PanSTARRS seems to pay regular visits to the Earth, and grow an anti-tail around May 23 perhaps every seventh year. Which "Comet PanSTARRS"? The Pan-STARRS survey has discovered more than 200 comets so far. In any case, the subject of today's APOD, properly designated...

So, how long before I get promoted from "Science Officer" (inre: the avatar and personal info tag) to "Court Jester, Junior Grade"? (neufer is Court Jester, First Class) B^) From the rules page - http://asterisk.apod.com/viewtopic.php?f=8&t=26696 : A person who posts on the ...

Yes, that must be it. Ann Ok. I found this pic that better shows - at least to my mind - that blur of stars as a more convincingly distinct object: view the expanded image to see it clearly. I can even imagine that it could be one of NGC 3628's "Magellanic clouds"! Great picture, Johnny! ...

It also reveals a small galaxy nearby, likely a satellite of NGC 3628 So, is this the nearby small galaxy being referred to? NGC3628.jpg Yes, that must be it. Ann Ok. I found this pic that better shows - at least to my mind - that blur of stars as a more convincingly distinct object. I can even ima...

These kinds of gradients are distributed over thousands or even millions of light years. They simply aren't significant over one light year. Ok, but then how close are nearby stars getting to our sun to nudge Oort cloud objects as I've often seen posited as the cause of some mass extinctions on Ear...

The tidal forces are infinitesimally small on the scale of something the size of a planetary system. There would be no detectable impact. Well, couldn't there be an increased chance of nearby star perturbations nudging Oort cloud objects inward and thereby increasing the likelihood of planetary imp...

APOD Robot wrote: ↑Thu Jun 04, 2020 4:05 am It also reveals a small galaxy nearby, likely a satellite of NGC 3628

So, is this the nearby small galaxy being referred to?

Let's say you had a solar system in one of these tidal fields...would life on a planet go on as normal? I know this would be an incredibly slow process. The tidal forces are infinitesimally small on the scale of something the size of a planetary system. There would be no detectable impact. Well, co...

...just how dense are these dust clouds? I'm thinking they would be much less dense than water vapor clouds on earth. Most cosmic dust particles measure between a few molecules & 10 -7 m. The light-year is ~10 16 m Hence, the optical cross section: σ d ~ (10 -7 m) 2 Optical depth τ d ~ [σ d x 1...

https://www.esa.int/var/esa/storage/images/esa_multimedia/images/2003/05/ngc_6523_lagoon_nebula/10180764-2-eng-GB/NGC_6523_Lagoon_Nebula_pillars.jpg Sometimes I just can't point to a feature of an image based on the description given. Like here: "Visible near the image center, at least two lon...

Sometimes I just can't point to a feature of an image based on the description given. Like here: "Visible near the image center, at least two long funnel-shaped clouds, each roughly half a light-year long". Just what funnel-shaped clouds is it referring to? At the center of the image I do...

https://apod.nasa.gov/apod/calendar/S_200601.jpg The Lively Center of the Lagoon Nebula Explanation: The center of the Lagoon Nebula is a whirlwind of spectacular star formation. Visible near the image center, at least two long funnel-shaped clouds, each roughly half a light-year long, have been fo...

Does anyone know what the object, visible in the full sized view, at approx. 5:00 of Mercury is? I'm not finding what you are referring to. All I see is haze and trees all around both Mercury and Venus. How close to Mercury is it? It’s about an inch below and to the right of Mercury as it first bec...

Tszabeau wrote: ↑Fri May 29, 2020 2:17 pm Does anyone know what the object, visible in the full sized view, at approx. 5:00 of Mercury is?

I'm not finding what you are referring to. All I see is haze and trees all around both Mercury and Venus. How close to Mercury is it?

The amount of light that is reflected off a still water surface depends on the angle of incidence. Taking that to be about 45° here, and solving the Fresnel equation, puts the reflected intensity at about 5%. Photographically, that means there is more than a 4-stop difference between the intensity ...

Orin, that's mysterious the disappearing clouds. My guess is though that the clarity is less in the reflection is that the water is dimmer so the photographer had to ramp the exposure f-stop up thereby making the sky look overexposed. By the way compliments to Helmut the photographer, I find this c...

NCTom wrote: ↑Sun May 24, 2020 11:55 am That was some crack considering after a couple of billion years of dust storms the thing is still 8 kilometers deep!

Hmm, that's an interesting thought. I wonder if the canyon really does have a very thick layer of dust at its bottom...