Local stellar distribution and galactic spiral structure

1970 ◽  
Vol 38 ◽  
pp. 189-198 ◽  
Author(s):  
S. W. McCuskey
Keyword(s):  
Spiral Structure ◽  
The Sun ◽  
Long Period ◽  
Classical Cepheids ◽  
Galactic Clusters ◽  
The Galaxy ◽  
Galactic Spiral Structure ◽  
Ob Associations ◽  
Galactic Spiral ◽  
Spiral Arm

Aside from the well-known spiral arm tracers such as the OB associations, young galactic clusters, WR stars and possibly the long-period classical cepheids, the more common stars in the neighborhood of the sun within 2 kpc show little or no relationship to the local spiral structure of the galaxy.

scholarly journals Spiral structure of the Galaxy Derived from the Hat Creek survey of neutral hydrogen

1970 ◽  
Vol 38 ◽  
pp. 126-139 ◽  
Author(s):  
H. Weaver
Keyword(s):  
Pitch Angle ◽  
Spiral Structure ◽  
Neutral Hydrogen ◽  
The Sun ◽  
General Picture ◽  
Contour Maps ◽  
The Galaxy ◽  
External Galaxies ◽  
Perseus Arm ◽  
Spiral Arm

The extensive Hat Creek survey of neutral hydrogen combined with southern observations provides the basis for a new discussion of the spiral structure of the galaxy. The purpose of this investigation is to provide a general picture of the galaxy. It is found that the pitch of the spiral arms is approximately 12°.5 and that there are many spurs and interarm features as we observe in external galaxies.The sun is not located in a major spiral arm, but rather in a spur or offshoot originating near or at the Sagittarius arm, which is a major structure in the galaxy. The young stars in the general vicinity of the sun delineate this spur, not a major arm structure. The stars and the gas are in agreement in indicating a large pitch angle (20°–25°) for this local structure, which differs from the smaller pitch angle for the arms which form the system as a whole.In the presentation a computer-produced movie of the galaxy based on Hat Creek hydrogen contour maps similar to those in Figure 1 was shown. It was used to illustrate generally the complexity of the gas structure and, in particular, to show (i) observational aspects of the spur in which the sun is located and (ii) the point of origin of the so-called Perseus arm.

scholarly journals Space distribution of interstellar dust in connection with the galactic spiral structure

1970 ◽  
Vol 38 ◽  
pp. 228-231
Author(s):  
T. A. Uranova
Keyword(s):  
Interstellar Dust ◽  
Spiral Structure ◽  
Space Distribution ◽  
Dust Density ◽  
Galactic Spiral Structure ◽  
Galactic Spiral

A maximum of dust density along the inner edge of the Cygnus arm is found. It seems that the same happens along the inner edges of the Perseus and the Sagittarius arms.

scholarly journals Galactic spiral structure

2009 ◽  
Vol 465 (2111) ◽  
pp. 3425-3446 ◽  
Author(s):  
Charles Francis ◽  
Erik Anderson
Keyword(s):  
Pitch Angle ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Stellar Orbits ◽  
Grand Design ◽  
Galactic Spiral Structure ◽  
Pattern Speed ◽  
Galactic Spiral ◽  
Almost All ◽  
Spiral Arm

We describe the structure and composition of six major stellar streams in a population of 20 574 local stars in the New Hipparcos Reduction with known radial velocities. We find that, once fast moving stars are excluded, almost all stars belong to one of these streams. The results of our investigation have led us to re-examine the hydrogen maps of the Milky Way, from which we identify the possibility of a symmetric two-armed spiral with half the conventionally accepted pitch angle. We describe a model of spiral arm motions that matches the observed velocities and compositions of the six major streams, as well as the observed velocities of the Hyades and Praesepe clusters at the extreme of the Hyades stream. We model stellar orbits as perturbed ellipses aligned at a focus in coordinates rotating at the rate of precession of apocentre. Stars join a spiral arm just before apocentre, follow the arm for more than half an orbit, and leave the arm soon after pericentre. Spiral pattern speed equals the mean rate of precession of apocentre. Spiral arms are shown to be stable configurations of stellar orbits, up to the formation of a bar and/or ring. Pitch angle is directly related to the distribution of orbital eccentricities in a given spiral galaxy. We show how spiral galaxies can evolve to form bars and rings. We show that orbits of gas clouds are stable only in bisymmetric spirals. We conclude that spiral galaxies evolve toward grand design two-armed spirals. We infer from the velocity distributions that the Milky Way evolved into this form about 9 billion years ago (Ga).

scholarly journals The Galactic spiral structure as revealed by O- and early B-type stars

2019 ◽  
Vol 487 (1) ◽  
pp. 1400-1409 ◽  
Author(s):  
B-Q Chen ◽  
Y Huang ◽  
L-G Hou ◽  
H Tian ◽  
G-X Li ◽  
...  
Keyword(s):  
Spiral Structure ◽  
Galactic Spiral Structure ◽  
Galactic Spiral
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