by Ann » Sat May 11, 2019 6:48 am
Confused wrote: ↑Sat May 11, 2019 5:06 am
I think this is the most confusing explanation I have read. It starts out by saying something about the Milky Way and I got the impression it was going to say the teeny tiny amount of light here on Earth illuminated the entire Milky Way.
The Milky Way shines by its own light, and it emits a lot of light:
EarthSky wrote:
The Milky Way galaxy is a collection of hundreds of billions of stars. This island of stars contains our sun and planets. Astronomers have estimated that the total luminosity of the central dozen or so light-years of our galaxy is equal to about 10 million suns. That sounds big and bright – until you recall that the center of our galaxy is 25,000 light-years away.
...
If there were no dust between us and the galactic center,
the light of all the stars located toward the galaxy’s core would easily exceed that of a full moon. If you looked in that direction, you wouldn’t see much else but the combined glow of billions of stars.
But because the core of the Milky Way is totally hidden by dust from our vantage point, so that we can't see it at all with our eyes, and because the stars that we can see inside the glowing band of the Milky Way are generally very far away and widely separated, the Milky Way looks very faint to us in the sky. But the trail of the launch in today's APOD is very bright.
Therefore it is impossible to capture both the bright launch trail of the rocket and a lot of details in the faint light of the Milky Way in just one exposure. Because of that, today's APOD is a combined stitched together image of two different exposures, one of the galaxy, on e of the rocket launch. There is no way it could have been otherwise.
Ann
[quote=Confused post_id=292127 time=1557551183 user_id=106445]
I think this is the most confusing explanation I have read. It starts out by saying something about the Milky Way and I got the impression it was going to say the teeny tiny amount of light here on Earth illuminated the entire Milky Way.
[/quote]
The Milky Way shines by its own light, and it emits a lot of light:
[quote][url=https://earthsky.org/space/what-does-the-center-of-the-galaxy-look-like]EarthSky[/url] wrote:
The Milky Way galaxy is a collection of hundreds of billions of stars. This island of stars contains our sun and planets. Astronomers have estimated that the total luminosity of the central dozen or so light-years of our galaxy is equal to about 10 million suns. That sounds big and bright – until you recall that the center of our galaxy is 25,000 light-years away.
...
If there were no dust between us and the galactic center, [b][color=#FFBF00][size=120]the light of all the stars located toward the galaxy’s core would easily exceed that of a full moon[/size][/color][/b]. If you looked in that direction, you wouldn’t see much else but the combined glow of billions of stars.[/quote]
But because the core of the Milky Way is totally hidden by dust from our vantage point, so that we can't see it at all with our eyes, and because the stars that we can see inside the glowing band of the Milky Way are generally very far away and widely separated, the Milky Way looks very faint to us in the sky. But the trail of the launch in today's APOD is very bright.
Therefore it is impossible to capture both the bright launch trail of the rocket and a lot of details in the faint light of the Milky Way in just one exposure. Because of that, today's APOD is a combined stitched together image of two different exposures, one of the galaxy, on e of the rocket launch. There is no way it could have been otherwise.
Ann