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[Arata]

Remember the topic I posted a while back about both the Milky Way & Andromeda being larger than scientists once thought, and us holding the crown of the largest galaxy in our local group? Well, shortly after that, I thought, "If both galaxies are larger than thought, then what is there precise number of stars?
I know that both galaxies now have more than 5 trillion stars orbiting their center, but what is the right amount?

Here is what I believe.

The Milky Way was thought to have about 400 billion stars.
Now 15 times larger, around 1.5 million light years across.

4x15=60
60 trillion stars
I personally believe that is too many, so I'll say from 10 to 40 trillion stars.

Andromeda was once thought to have 1 trillion stars.
Now 5 times larger, around 1 million light years across.

1x5=5
From 5 to 10 trillion stars.
I

[Bla]

Interesting. But why do you believe 60 trillion is too many and that 10-40 sounds more realistic?

[witold]

Then. We will "eat" Andromeda 

[monmarfori]

Andromeda has only 700 billion stars.

[Arata]

No it doesn't.
 

[Dan Dixon]

[Milky Way] Now 15 times larger, around 1.5 million light years across.

Where did you hear this?

These all say 100000 light years.
http://en.wikipedia.org/wiki/Milky_way
http://www.wolframalpha.com/input/?i=diameter+of+the+milky+way

[Arata]

Search on google.
The milky way is larger than thought, and so is andromeda.
When you view a photo of andromeda, you are looking at the bright area, but the disc extends to the size of the big dipper.

[Dan Dixon]

Search on google.

Do you have a link?

[Bla]

Found this, but this only claims that it was 15% wider:
Article on BBC News on 20090106
This article from 20090220 suggests that the disc is twice as thick as earlier thought (12,000 ly instead of 6,000 ly):
Article from CosmosMagazine

But I didn't find anything claiming that it was so extremely big as 1.5 million ly across... Containing a trillion stars...

[monmarfori]

Our own galaxy has only 400 billion stars or 400,000,000,000 stars. but some says that it is 1.5 in diameter will look like 600 billion stars.

[Arata]

Well, if the milky way is 15 times larger, then I suggest that you multiply the old size with 15, and you get 1.5 million light years across.

[monmarfori]

Too big? it would have 15 trillion stars.

[Arata]

I believe you are talking about the size of our galaxy, not the amount of stars.
The Milky Way has about 60 trillion stars (not including the globular clusters).

[Bla]

But we don't assume The Milky Way is so big, all the sites (I've found at least) show that it's about 100,000 ly across and has 100-400 billion stars. What evidence do you have to show that it is so much bigger? Please send a link.

[Arata]

But people dont know that we are larger, because not much people has seen information showing We are the largest in local group.

http://www.cbc.ca/technology/story/2009/01/06/milky-way-mass.html
http://news.bbc.co.uk/2/hi/science/nature/7813635.stm
http://www.space.com/scienceastronomy/070107_andromeda_halo.html

No matter what the sizes actually are, MW & Andromeda are still the largest galaxeis in the local group.

[Bla]

But it only said that it was the faint stars in Andromeda's halo that made it bigger, some stars orbiting at very large distances. We can't just multiply the number of stars with the times the new radius is bigger.
And we can't apply it to The Milky Way if we don't find similar stars at so big distances. The articles about The Milky Way, I would say, are based on the "old" discoveries, or measuring the real visible disc, and not all the stars in the halo or far away from the core.
I don't think the new discovery means that Andromeda or our Milky Way contains trillions of stars. The article states that The Milky Way is discovered to be 50% more massive than before thought, so I assume it contains 200-800 billion stars then, if most isn't dark matter.

I won't go too deep into it before I've got some real numbers and information though. What we're doing now is mostly guessing.