APOD 17 July 2009 - Starburst Galaxy M94

[meep]

How can light from a star less than 10 milliion years old reach us from a galaxy that is 15 million light years away??? APOD 17 July 2009

[Qev]

As we see them now, they're ten million years old, but the light that we see from them now left that galaxy 15 million years ago (since the galaxy is 15 million light-years away).

[p1gnone]

I see, without caption comment, a faint disk DOUBLING the radius of the apparent galactic disk. Any ideas on this larger disk?

[emc]

http://apod.nasa.gov/apod/ap090717.html

Someone please correct me if I am wrong, but here is my take on star gazing. Gazing at stars is looking at the past and that is something that was strangely difficult for me to wrap my head around. My sense is somewhat introverted so I tend to think in terms of “my perception” of things. My perception, without scientific knowledge, tells me that it is now everywhere at the same time. But scientifically, relatively, it is "now" only within a specific point of reference. So when I see a galaxy 15 million light years distant, that galaxy’s “now” is 15 million years into the future from what I see. And that galaxy sees the Milky Way as it was 15 million years ago. So if the caption is speaking in terms of our relative reference, those 10 million year old starbursts are "now" 25 million years old...

[neufer]

http://apod.nasa.gov/apod/ap090717.html

Someone please correct me if I am wrong, but here is my take on star gazing. Gazing at stars is looking at the past and that is something that was strangely difficult for me to wrap my head around. My sense is somewhat introverted so I tend to think in terms of “my perception” of things. My perception, without scientific knowledge, tells me that it is now everywhere at the same time. But scientifically, relatively, it is "now" only within a specific point of reference. So when I see a galaxy 15 million light years distant, that galaxy’s “now” is 15 million years into the future from what I see. And that galaxy sees the Milky Way as it was 15 million years ago. So if the caption is speaking in terms of our relative reference, those 10 million year old starbursts are "now" 25 million years old...

The time plane/sheet of "NOW" is a somewhat relative term for casually separated objects in accordance with both general & special relativity.

It can be defined as pretty much anything you want.

Often it is convenient to define it as the earth's past light cone.

[neufer]

I see, without caption comment, a faint disk DOUBLING the radius of the apparent galactic disk. Any ideas on this larger disk?

http://antwrp.gsfc.nasa.gov/apod/ap021121.html
http://antwrp.gsfc.nasa.gov/apod/ap010613.html
http://antwrp.gsfc.nasa.gov/apod/ap951016.html

[emc]

It can be defined as pretty much anything you want.

Often it is convenient to define it as the earth's past light cone.

http://en.wikipedia.org/wiki/Light_cone

I did a little light reading and it made me want an ice cream.

[emc]

I see, without caption comment, a faint disk DOUBLING the radius of the apparent galactic disk. Any ideas on this larger disk?

http://antwrp.gsfc.nasa.gov/apod/ap021121.html
http://antwrp.gsfc.nasa.gov/apod/ap010613.html
http://antwrp.gsfc.nasa.gov/apod/ap951016.html

So galaxies leak too.

[bystander]

I see, without caption comment, a faint disk DOUBLING the radius of the apparent galactic disk. Any ideas on this larger disk?

http://antwrp.gsfc.nasa.gov/apod/ap021121.html
http://antwrp.gsfc.nasa.gov/apod/ap010613.html
http://antwrp.gsfc.nasa.gov/apod/ap951016.html

I think what p1gnone is referring to is the faint outer halo of M94 in the current apod. I assume it is not an artifact, since it shows up in APOD 2002 Nov 21, also. I'm fairly certain the bright UV rings in APOD 2001 June 13 and APOD 1995 Oct 16 are the same as the blue ring of young stars in the current apod. None of these address the halo. Is it a part of M94 and is it included in the 30,000 ly diameter.