Relativity Science Calculator - Some Consequences of Kepler, Galileo, and Newton Equations
The Local Group of Galaxies ( LG ) - comprises over 50 galaxies
Satellites distance to solar system[a] diameter[b] mass[c] number of stars shape[d] other characteristics
Milky Way
(The Galaxy)
approx. 13 2.5 x 104 ly
(galactic center to earth)
(1.0 - 1.2) x 105 ly
10,000 ly thick
5.7 x 1011 solar masses
including dark matter: 1.9 x 1012 solar masses
200 - 400 billion barred spiral Second largest galaxy in the group - most massive of Local Group due to dark matter
Canis Major Dwarf Galaxy 2.5 x 104 ly winding stream 1.0 x 109 solar masses 1.0 x 109 forms a ring around The Galaxy orbits while merging into The Galaxy
Virgo Stellar Stream 3.0 x 104 ly 3.0 x 104 ly (length) -- few 100-thousands stream merging into The Galaxy
Sagittarius Dwarf Elliptical Galaxy (SagDEG) 8.0 x 104 ly 1.0 x 104 ly 5.8 x 107 solar masses 1.0 x 109 elliptical will collide with The Galaxy in next 100 million years
The Large Magellanic Cloud Galaxy ( LMC ) 1.8 x 105 ly 25,000 ly 10.0 x 109 solar masses 10.0 x 109 very prominent center bar probably an early barred spiral
The Small Magellanic Clouds ( SMC ) 2.1 x 105 ly 15,000 ly 2.0 x 109 solar masses 2.0 x 109 contains center bar probably an early barred spiral
Andromeda
(M31)
approx. 14 or 15 dwarf galaxies 2.54 ± 0.06 M ly 2.2 x 104 ly 7.1 x 1011 solar masses
including dark matter: 1.23 x 1012 solar masses
1.0 x 1012 spiral Largest member of group - nearest spiral galaxy to Milky Way approaching the sun with velocity approx. 300 km/sec
Andromeda I 2.43 M ly 2,200 ly ? 100 variable stars dSph estimated age is approx 10 billion yrs
Andromeda II 2.13 M ly 2,000 ly 2 billion solar masses ( dark matter ) 73 variable stars dSph
Andromeda III 2.44 M ly 3,000 ly ? 56 variable stars dSph
Andromeda V 2.52 M ly ? ? ?
Andromeda VI ( Pagasus Dwarf ) 2.55 M ly 3,000 ly ? 118 variable stars
Andromeda VII ( Cassiopeia Dwarf ) 2.49 M ly 1,900 x 1,500 ly ? dSph dominated by very old stars, with ages up to 10 billion years
Andromeda VIII 2.7 M ly length 30,000 ly ? 400,000 elongated stream widespread and transparent
Andromeda IX 2.5 M ly 3,000 ly probably mostly free-floating dark matter mini-galaxy dSph most diffuse known galaxy - the least luminous galaxy
Andromeda X 2.9 M ly ? dim dwarf most faint satellite galaxy - lies about 280,000 - 450,000 ly from M -31
Triangulum Galaxy ( M33 ) 2.59 M ly 50,000 ly 10 to 40 billion solar masses 10 - 40 billion spiral 3rd largest member of group
SagDIG[e] --- 3.5 M ly 1.5 x 103 ly high gas/mass ratio 665 million ± 5% dwarf irregular at the remotest edge of the Local Group
Barycenter located somewhere between the Milky Way and the Andromeda Galaxy - -
caveat lector! reader, please beware of these unsettled observations and numbers.
a,b  ly = light year; M ly = million light years
c  solar mass = sun's mass
d  shapes are disk, elliptical or non - uniform irregular; dSph = dwarf spheroidal
e  Sagittarius Dwarf Irregular Galaxy; ancient galaxy formed in early universe; highest gas/star ratio ( i.e., low - mass ) making it ideal for study of star formation;

relatively few elements heavier than helium unlike our sun, hence metal - poor galaxy.