by Ann » Sun Oct 08, 2023 3:17 am
Fred the Cat wrote: ↑Sat Oct 07, 2023 5:35 pm
Ann wrote: ↑Sat Oct 07, 2023 5:04 pm
Annette Ferguson of Astronomy Magazine wrote:
So, on average, we expect that roughly six to seven new stars form in the Milky Way every year.
While this might seem small,
the star-formation rate of the Andromeda Galaxy (M31) has been estimated to be even smaller at roughly 0.4 solar mass per year (or just one to two stars on average).
Looking at other spiral galaxies in the nearby universe, we see a range of star-formation rates, but it seems like the rates measured for the Milky Way and Andromeda are fairly typical overall.
P.S. I read your links, but I couldn't find the claim that Andromeda is forming 100 new stars per year. Can you provide us with a quote?
Ann
Just averaging star estimate over age. I'd be
curious about a more recent count too.
I'd say that Andromeda has not formed all those trillion stars by itself. Instead, it has probably "stolen" quite a few of them, by capturing a lot of hapless nearby dwarf galaxies and laying claim to their stars.
I didn't even try to find images or even much info on all the merging events of Andromeda, but there are some interesting tidbits about the merging history of the Milky Way (and we have no reason to believe that Andromeda has been any less diligent than the MW when it comes to eating galactic snacks):
ESA wrote:
Our galaxy, the Milky Way, began forming around 12 billion years ago. Since then, it has been growing in both mass and size through a sequence of mergers with other galaxies.
...
When a foreign galaxy falls into our own, great gravitational forces known as tidal forces pull it apart. If this process goes slowly, the stars from the merging galaxy will form a vast stellar stream that can be easily distinguished in the halo. If the process goes quickly, the merging galaxy’s stars will be more scattered throughout the halo and no clear signature will be visible.
But the merging galaxy may contain more than just stars. It could also be surrounded by a population of globular star cluster and small satellite galaxies.
So some of the globulars that now belong to the Milky Way may have originally come from smaller galaxies that were captured by the Milky Way. And the way I understand it, the number of globular clusters of a galaxy says something about its "merging history". As for Andromeda, it has more than twice as many globulars as the Milky Way (~150):
Wikipedia wrote:
There are approximately 460 globular clusters associated with the Andromeda Galaxy. The most massive of these clusters, identified as Mayall II, nicknamed Globular One, has a greater luminosity than any other known globular cluster in the Local Group of galaxies.
Ann
[quote="Fred the Cat" post_id=334270 time=1696700119 user_id=143303]
[quote=Ann post_id=334269 time=1696698240 user_id=129702]
[quote="Fred the Cat" post_id=334268 time=1696696679 user_id=143303]
Averaging 100 stars per year, [url=https://lowell.edu/views-from-mars-hill-andromeda-galaxy/] Andromeda[/url] seems pretty good at [url=https://www.mdpi.com/2218-1997/9/8/349] star formation[/url]. :thumb_up:
[url=https://cfa.harvard.edu/news/massive-star-forming-galaxy-early-universe] Prototypical?[/url] :wink:
[/quote]
[quote][url=https://www.astronomy.com/science/ask-astro-how-many-stars-are-born-each-year-in-the-milky-way/]Annette Ferguson of Astronomy Magazine[/url] wrote:
So, on average, we expect that roughly six to seven new stars form in the Milky Way every year.
While this might seem small, [b][color=#FF0000]the star-formation rate of the Andromeda Galaxy (M31) has been estimated to be even smaller at roughly 0.4 solar mass per year[/color][/b] (or just one to two stars on average).
Looking at other spiral galaxies in the nearby universe, we see a range of star-formation rates, but it seems like the rates measured for the Milky Way and Andromeda are fairly typical overall.
[/quote]
P.S. I read your links, but I couldn't find the claim that Andromeda is forming 100 new stars per year. Can you provide us with a quote?
Ann
[/quote]
Just averaging star estimate over age. I'd be [url=https://www.universetoday.com/82207/star-birth-and-death-in-the-andromeda-galaxy/] curious[/url] about a more recent count too. :yes:
[/quote]
I'd say that Andromeda has not formed all those trillion stars by itself. Instead, it has probably "stolen" quite a few of them, by capturing a lot of hapless nearby dwarf galaxies and laying claim to their stars.
I didn't even try to find images or even much info on all the merging events of Andromeda, but there are some interesting tidbits about the merging history of the Milky Way (and we have no reason to believe that Andromeda has been any less diligent than the MW when it comes to eating galactic snacks):
[img3="Remnants of smaller galaxies that have merged with the Milky Way. Credit: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO"]https://www.esa.int/var/esa/storage/images/esa_multimedia/images/2022/02/gaia_reveals_a_new_member_of_the_milky_way_family/23954169-1-eng-GB/Gaia_reveals_a_new_member_of_the_Milky_Way_family_pillars.jpg[/img3]
[quote][url=https://www.esa.int/ESA_Multimedia/Images/2022/02/Gaia_reveals_a_new_member_of_the_Milky_Way_family]ESA[/url] wrote:
Our galaxy, the Milky Way, began forming around 12 billion years ago. Since then, it has been growing in both mass and size through a sequence of mergers with other galaxies.
...
When a foreign galaxy falls into our own, great gravitational forces known as tidal forces pull it apart. If this process goes slowly, the stars from the merging galaxy will form a vast stellar stream that can be easily distinguished in the halo. If the process goes quickly, the merging galaxy’s stars will be more scattered throughout the halo and no clear signature will be visible.
But the merging galaxy may contain more than just stars. It could also be surrounded by a population of globular star cluster and small satellite galaxies. [/quote]
So some of the globulars that now belong to the Milky Way may have originally come from smaller galaxies that were captured by the Milky Way. And the way I understand it, the number of globular clusters of a galaxy says something about its "merging history". As for Andromeda, it has more than twice as many globulars as the Milky Way (~150):
[quote][url=https://en.wikipedia.org/wiki/Andromeda_Galaxy#Globular_clusters]Wikipedia[/url] wrote:
There are approximately 460 globular clusters associated with the Andromeda Galaxy. The most massive of these clusters, identified as Mayall II, nicknamed Globular One, has a greater luminosity than any other known globular cluster in the Local Group of galaxies.[/quote]
Ann