Search found 17370 matches
- Thu May 02, 2024 1:34 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
- Replies: 23
- Views: 482
Re: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
I was declaring the Snowman's height, not estimating. Well, yes... not really an option with most astronomical objects, though! Because no subtended angle was explicitly mentioned, my brain decided there were only 2 knowns in a 3-variable equation relating angle, distance and width, and the width e...
- Thu May 02, 2024 12:33 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
- Replies: 23
- Views: 482
Re: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
I think, regardless of the observer's distance to the object, its width, in light-years, is static. I.E. Q:"How tall is Snowman?" A: 2 meters Q: I've doubled my viewing distance from Snowman; now how tall is Snowman? A: 2 meters But in order to determine that the snowman is 2 meters high,...
- Wed May 01, 2024 3:10 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
- Replies: 23
- Views: 482
Re: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
"The absolute distance (which is a useful thing to know) is calculated from the angular size of the object. The majority of APOD images of deep sky objects present a physical (absolute) size based upon subtended angle and estimated distance". Yes, the descriptions usually give the angular...
- Wed May 01, 2024 2:13 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
- Replies: 23
- Views: 482
Re: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
Your last post mentions spanning an angle, which is reasonable. The article didn't - it mentioned an absolute width. I think the author should re-state the width as an angular diameter, or relative to something else E.G. Moon radius, not light-years. The absolute distance (which is a useful thing t...
- Wed May 01, 2024 1:46 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
- Replies: 23
- Views: 482
Re: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
I think, regardless of the observer's distance to the object, its width, in light-years, is static. I.E. Q:"How tall is Snowman?" A: 2 meters Q: I've doubled my viewing distance from Snowman; now how tall is Snowman? A: 2 meters But in order to determine that the snowman is 2 meters high,...
- Wed May 01, 2024 1:29 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
- Replies: 23
- Views: 482
Re: APOD: IC 1795: The Fishhead Nebula (2024 May 01)
"At that distance, IC 1795 would span about 70 light-years across." I don't understand how a width, expressed here in absolute units, is related to distance. I believe the number is incorrect... but probably because they've identified the nebula incorrectly. IC 1795 is just the "head...
- Mon Apr 29, 2024 1:53 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Rings Around the Ring Nebula (2024 Apr 28)
- Replies: 15
- Views: 543
- Sun Apr 28, 2024 4:09 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Rings Around the Ring Nebula (2024 Apr 28)
- Replies: 15
- Views: 543
Re: APOD: Rings Around the Ring Nebula (2024 Apr 28)
So, something similar will likely be the fate of our own Sun, correct? From the link - Planetary Nebulae Planetary nebulae (PN) represent the last stages of evolution for low- and intermediate-mass stars whose Main Sequence mass was less than about 8 solar masses. After evolving through the Asympto...
- Sun Apr 28, 2024 3:06 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Rings Around the Ring Nebula (2024 Apr 28)
- Replies: 15
- Views: 543
Re: APOD: Rings Around the Ring Nebula (2024 Apr 28)
Interesting adjective "elongated". Implies ovoid, but outermost wisps are almost perfectly circular. We do not know the viewing aspect. Could be looking down the barrel of somethig like the butterfly nebula. In fact, we understand both the viewing aspect and the 3D structure of the Ring N...
- Sun Apr 28, 2024 2:29 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Rings Around the Ring Nebula (2024 Apr 28)
- Replies: 15
- Views: 543
Re: APOD: Rings Around the Ring Nebula (2024 Apr 28)
The instruments of the observers of the 16th and 17th centuries were less precise than the 150 mm amateur telescopes, but with the desire to discover they solved it. When the Ring Nebula is observed with an amateur telescope, a milky circle appears to the eye with a dark center and nothing more res...
- Sun Apr 28, 2024 2:20 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Rings Around the Ring Nebula (2024 Apr 28)
- Replies: 15
- Views: 543
Re: APOD: Rings Around the Ring Nebula (2024 Apr 28)
Had Messier discovered this planetary nebula with the same fine details seen here, I'm sure he would have ditched the term "planetary" nebula right away! We read over and over that it's a misnomer; what would be a better term? Red giant remnant? I've always liked the term, and wouldn't la...
- Sat Apr 27, 2024 7:51 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: All Sky Moon Shadow (2024 Apr 27)
- Replies: 15
- Views: 455
Re: APOD: All Sky Moon Shadow (2024 Apr 27)
This image really showcases just how tiny this phenomenon really looks to the unaided eye. Still, though, it's a great image! Actually, to the unaided eye, it looks much larger. What this picture illustrates is just how small it actually is, despite the powerful illusion of it appearing much larger...
- Sat Apr 27, 2024 3:13 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Colors of Twilight vs. Sunset/Sunrise
- Replies: 28
- Views: 2138
Re: Colors of Twilight vs. Sunset/Sunrise
Thanks for the suggestion, Chris, I didn't think of that! :D 🐐 That's a lovely goat, by the way. What's her name? She looks very feminine to me! :D 👱🏾♀️ Ann Gretel. She'll be kidding in a couple of weeks. Thanks for teaching me a new word, Chris! I only knew one meaning of the word "kidding&q...
- Sat Apr 27, 2024 3:05 pm
- Forum: Open Space: Discuss Anything
- Topic: Weather!
- Replies: 2853
- Views: 989819
- Fri Apr 26, 2024 2:13 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Regulus and the Dwarf Galaxy (2024 Apr 26)
- Replies: 18
- Views: 759
Re: APOD: Regulus and the Dwarf Galaxy (2024 Apr 26)
Well I was going to ask at what point we differentiate between a star cluster and dwarf spheroidal galaxy, but thanks to the color commentary I am guessing the black hole at the center may be a factor. :idea: Some globular clusters have central black holes. I think there are at least two difference...
- Fri Apr 26, 2024 1:58 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Regulus and the Dwarf Galaxy (2024 Apr 26)
- Replies: 18
- Views: 759
Re: APOD: Regulus and the Dwarf Galaxy (2024 Apr 26)
So many unanswered questions - flabbergast to the max. First - what mechanism causes a star to rotate at such an enormous rate? Sucking gas off another star won’t do it. Second - try tracking down the two assertions about LEO I. Central density comes from a model which requires a central black hole...
- Fri Apr 26, 2024 12:55 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Regulus and the Dwarf Galaxy (2024 Apr 26)
- Replies: 18
- Views: 759
Re: APOD: Regulus and the Dwarf Galaxy (2024 Apr 26)
Well I was going to ask at what point we differentiate between a star cluster and dwarf spheroidal galaxy, but thanks to the color commentary I am guessing the black hole at the center may be a factor. :idea: Some globular clusters have central black holes. I think there are at least two difference...
- Thu Apr 25, 2024 3:55 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: NGC 604: Giant Stellar Nursery (2024 Apr 25)
- Replies: 7
- Views: 531
Re: APOD: NGC 604: Giant Stellar Nursery (2024 Apr 25)
I'm still somewhat puzzled by JWST colour choices. Is there a scientific reason why they chose pink/red for NGC 604 but a kind of rusty brownish not-really-red for the Tarantula Nebula? Is it to reflect different molecular properties or are these different colours for no real reason? 604.png 2070.j...
- Thu Apr 25, 2024 2:54 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: NGC 604: Giant Stellar Nursery (2024 Apr 25)
- Replies: 7
- Views: 531
Re: APOD: NGC 604: Giant Stellar Nursery (2024 Apr 25)
I'm still somewhat puzzled by JWST colour choices. Is there a scientific reason why they chose pink/red for NGC 604 but a kind of rusty brownish not-really-red for the Tarantula Nebula? Is it to reflect different molecular properties or are these different colours for no real reason? 604.png 2070.j...
- Tue Apr 23, 2024 6:12 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Contrail Shadow X (2024 Apr 23)
- Replies: 20
- Views: 610
Re: APOD: Contrail Shadow X (2024 Apr 23)
They are most certainly the condensation trails produced by passing jet airplanes. Contrails.P. Mitchell wrote: ↑Tue Apr 23, 2024 6:08 pm These are not 'contrails'.
- Tue Apr 23, 2024 3:52 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Contrail Shadow X (2024 Apr 23)
- Replies: 20
- Views: 610
Re: APOD: Contrail Shadow X (2024 Apr 23)
from beneath https://www.globe.gov/documents/16792331/47233527/cld_pers1.jpg/f3c94d07-4a38-414c-b856-1566e7e7c5ae?t=1581356571539 Right... but relevance to my comments? ok I am fitting the shadow, the trails and Sun… and you are right, Sun is high in the sky Contrail Shadow X (2024 Apr 23)-.jpg I'm...
- Tue Apr 23, 2024 2:27 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Contrail Shadow X (2024 Apr 23)
- Replies: 20
- Views: 610
Re: APOD: Contrail Shadow X (2024 Apr 23)
I agree with others here that we are seeing the shadows of the contrails cast down onto the clouds, not up. (I'm not convinced it's even possible to have a contrail shadow cast up onto a cloud... the Sun would have to be on or slightly below the horizon, and I think the directly illuminated cloud w...
- Tue Apr 23, 2024 1:49 pm
- Forum: The Observation Deck: Latest Sky Photography
- Topic: Submissions: 2024 April
- Replies: 103
- Views: 4173
Re: Submissions: 2024 April
NGC 2403 This spiral galaxy in Camelopardalis is often compared to M33, but is imaged much less often. Visually, it is a bright binocular object. It is strikingly populated by H II regions, one of which is so large it has its own catalog designation (NGC 2404) inside its parent galaxy. NGC 2403 is ...
- Tue Apr 23, 2024 12:53 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Contrail Shadow X (2024 Apr 23)
- Replies: 20
- Views: 610
Re: APOD: Contrail Shadow X (2024 Apr 23)
I agree with others here that we are seeing the shadows of the contrails cast down onto the clouds, not up. (I'm not convinced it's even possible to have a contrail shadow cast up onto a cloud... the Sun would have to be on or slightly below the horizon, and I think the directly illuminated cloud wo...
- Mon Apr 22, 2024 3:26 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Moon and Smoke Rings from Mt. Etna (2024 Apr 22)
- Replies: 6
- Views: 437