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Astrophysics/How many stars are in our local galaxy group?


QUESTION: Hi! How many stars have been estimated to be in our local galaxy group?

ANSWER: Hello,

By "local galaxy group" I presume you mean the Milky Way galaxy. However, the estimate is not a single number but rather a range given all the uncertainties (e.g. stars with widely varying mass from red dwarfs to blue supergiants) and obscuring dust not to mention the existence of a massive black  hole at the galaxy center. So the range estimate is usually from about 200 billion to 400 billion stars.

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QUESTION: Not actually. I meant how many stars would you estimate that Milky Way, Andromeda, Triangulum Galaxy and their satellites would have in total. So is there estimations for the number of stars in these galaxies? Wikipedia shows no amount of stars for most dwarf galaxies in our local group.


I was actually afraid you might have meant that. But, of course, if the uncertainty in the stellar numbers of our galaxy alone displays such a vast range you can imagine it would be dramatically greater including all the galaxies you mention. Could be anywhere from 5 trillion stars to 50 trillion. Depending on which mass estimates are being used, accounting for other factors such as methodological defects, errors - including from presence of dark matter or obscuring interstellar dust.

So, it is no wonder Wikipedia provides no estimate given there is really no practical way to obtain one.  Of course, any site or person could fire off a number - like 15 trillion - but in the end they'd have to admit it was pure guesswork.

One must admit that for some areas of astronomy there is simply too wide a gap between the data and observations to be able to provide any degree of precision. Or even 'ball park' estimates!


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Philip A. Stahl


I specialize in stellar and solar astrophysics. Can answer questions pertaining to these areas, including: stellar structure and evolution, HR diagrams, binary systems, collapsars (black holes, neutron stars) stellar atmospheres and the spectroscopic analysis of stars as well as the magnetohydrodynamics of sunspots and solar flares. Sorry No homework problems done or research projects! I will provide hints on solutions. No nonsense questions accepted, i.e. pertaining to astrology, or 'UFOs' or overly speculative questions: 'traveling through or near black holes, worm holes, time travel etc. Absolutely NO questions based on the twaddle at this Canadian site: purporting to show a "new physics". Do not waste my time or yours by wasting bandwidith with reference to such bunkum.


Have constructed computerized stellar models; MHD research. Gave workshops in astrophysics (stellar spectroscopy, analysis) at Harry Bayley Observatory, Barbados. More than twenty years spent in solar physics research, including discovery of SID flares. Developed first ever consistent magnetic arcade model for solar flares incorporating energy dissipation and accumulation. Developed first ever loop-based solar flare model using double layers and incorporating cavity resonators. (Paper presented at Joint AGU/AAS Meeting in Baltimore, MD, May 1994)

American Astronomical Society (Solar physics and Dynamical astronomy divisions), American Geophysical Union, American Mathematical Society, Intertel.

Papers appearing in Solar Physics, Journal of the Royal Astronomical Society of Canada, Journal of the Barbados Astronomical Society, Meudon Solar Flare Proceedings (Meudon, France). Books: 'Fundamentals of Solar Physics', 'Selected Analyses in Solar Flare Plasma Dynamics', 'Physics Notes for Advanced Level', 'Astronomy & Astrophysics: Notes, Problems and Solutions', 'Modern Physics: Notes, Problems and Solutions'

B.A. degree in Astronomy; M.Phil. degree in Physics - specializing in solar physics.

Awards and Honors
Postgraduate research award- Barbados government; Studentship Award in Solar Physics - American Astronomical Society. Barbados Astronomical Society award for service (1977-91) as Journal editor.

Past/Present Clients
Caribbean Examinations Council (as advisor, examiner), Barbados Astronomical Society (as Journal Editor 1977-91), Trinidad & Tobago Astronomical Society (as consultant on courses, methods of instruction, and guest speaker).

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