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# Rotation Curve

Rotation Curve
Galactic rotation curves plot a galaxy's circular velocity (which can be measured using the of of the trailing and leading sides as viewed from the Earth) vs. the distance from the center of rotation.

s: As discussed in the disk-dynamics section, real disk galaxies show flat s which require a density distribution approximately scaling as 1/R, ...

ROTATION CURVE - Plot showing how orbital velocity (V) varies with distance from the centre of an object (R).

A quantitative description of how fast each part of a galaxy is rotating about the center. A rotation velocity is the velocity of a rotating galaxy at a certain distance from the center of the galaxy.

Rotation Curve
A graph of orbital velocity versus radius in the disk of a galaxy.
RR Lyrae Variable ...

- A plot of the speed of revolution of the stars and gas in a galaxy versus distance from the center of the galaxy
RR Lyrae Star - A member of a class of giant pulsating stars, all of which have pulsation periods of about 1 day ...

The rotation curve is a plot of the orbital velocity of the clouds around the galactic center vs. their distance from the Galaxy center.

The Galactic plots the orbital speed of matter in the disk versus distance from the Galactic center. By applying Newton's laws of motion, astronomers can determine the mass of the Galaxy.

Rotation Curves for 3 Spiral Galaxies - Galaxy Image(left), Spectrum (center - photographic negative), & Plot (right).
The flatness of the rotation curve with no downward turn indicates that the mass distribution extends far beyond ...

:
rapid rise, then constant (at ~200 km/s)
differential rotation (inner stars overtake)
dark matter extends beyond stars (unknown) ...

rotation curve Plot of the orbital speed of disk material in a galaxy against its distance from the galactic center. Analysis of rotation curves of spiral galaxies indicates the existence of dark matter.

of a typical spiral galaxy: predicted (A) and observed (B). The distance is from the galactic core.

A rotation curve is flat when the velocity is constant. If you look at this equation, this means that M/R must also be constant.

A is a plot of speed versus distance from the center of an astronomical system.

Galactic rotation curves, which illustrate the velocity of rotation versus the distance from the galactic center, cannot be explained by only the visible matter.

Since then the s of many more galaxies were studied (bigger telescopes, much more sensitive electronic light detectors) and flat s were the general rule.

Rotation Curves as evidence of a dark matter halo
The presence of dark matter in the halo is demonstrated by its gravitational effect on a spiral galaxy's rotation curve.

Figure 16. The for the Milky Way. The curve varies at different distances from the center. Our location is at roughly 8 kpc from the center. Graph is from a paper by Clemens, 1985.

1977 - Brent Tully and Richard Fisher discover the Tully-Fisher relation between the luminosity of an isolated spiral galaxy and the velocity of the flat part of its rotation curve, ...

A plot of orbital speed versus the distance from the galactic center is known as a .
The along the above formula points to mystery regarding the Galaxy.

Because galaxies are so faint, measuring the rotation curve is a difficult business. But by the early 1970's, instruments advanced far enough to allow very precise measurements of galaxy rotation from the center out to the visible edge of the disk.

For nearby galaxies, the mass is often estimated by measuring the (for spiral galaxies) or the velocity dispersion (for elliptical galaxies). The higher the velocities, the greater the mass which must be enclosed.

Among this data was each galaxy's 'rotation curve,' a graph that plots the rotational speed of the stars in the galaxy as a function of their distance from the galaxy's center.

For example, the quantity and distribution of luminous matter within disk galaxies cannot account for the s observed, implying a significant invisible component.

Definition: Dark Matter: Name given to the amount of mass whose existence is deduced from the analysis of galaxy rotation curves but which until now, has escaped all detections. There are many theories on what dark matter could be.

The gravitational potential of the bulge is important for the dynamical behavior of the inner regions of the galaxy, but further out, the mass of the disk and the dark matter dominate, producing flat galactic s.

Measuring the Doppler shifts of the great interstellar clouds of hydrogen that line the Milky Way's spiral arms allows astronomers to measure the rotation curve of the Galaxy and infer its mass, ...

Symmetric Theory: D - an unclassifiable mess. Example: "a flat implies solid body rotation."
Why the Big Bang is Wrong: F - more tired light but with the added failure of a mechanism that just won't work.

See also: Rotation, Galaxy, Galaxies, Astro, Orbit