Dark Matter

[David Levy]

In the Hebrew version of Wikipedia it is stated that there is no need for dark matter at the elliptical galaxy due to the low velocity:

 

"כאשר נערכו תצפיות דומות בגלקסיות אליפטיות,היה נראה שהחומר האפל אינו נחוץ שם, וניתן להסביר את התנועה בתוך הגלקסיה בהסתמך עלהחומר הנראה בלבד"

 

In English: "When similar observations were made in elliptical galaxies, dark matter would seem there is not needed, and can be explained by the movement within the galaxy,

 

based only on visible matter "

 

בגלקסיות אליפטיות קיימת תנועה מן המרכז והחוצה, שאינה מתגלה בקלות עלידי אפקט דופלר על-פי גישה זו, מהירותם של הכוכבים בגלקסיות אליפטיות גבוהה מזו שנדמית לנו, ולכן גם בהן מתחייב קיומו של חומר אפל

 

In English: "In elliptical galaxies there is movement from the center and out, is not easily revealed by the Doppler effect - this approach, the speed of stars in elliptical galaxies is higher

 

than that seems to us, so also are committed to the existence of dark matter"

 

So, the idea is that based on Doppler effect verification, the velocity is normal - no need for dark matter.

 

Never the less, they consider that there might be some difficulties to measured correctly the speed, therefore, they estimate that the velocity should be higher than the test result...

 

 

 

Do you agree?

 

Edited June 5, 2012 by David Levy

[David Levy]

Any feedback???

 

 

[Spyman]

Why don't you use the English version of Wikipedia? In general the English pages contains more information than what other languages provide.

 

* Elliptical galaxies. Some elliptical galaxies show evidence for dark matter via strong gravitational lensing, X-ray evidence reveals the presence of extended atmospheres of hot gas that fill the dark haloes of isolated ellipticals and whose hydrostatic support provides evidence for dark matter. Other ellipticals have low velocities in their outskirts (tracked for example by planetary nebulae) and were interpreted as not having dark matter haloes. However, simulations of disk-galaxy mergers indicate that stars were torn by tidal forces from their original galaxies during the first close passage and put on outgoing trajectories, explaining the low velocities even with a DM halo. More research is needed to clarify this situation.

http://en.wikipedia.org/wiki/Dark_matter#Galactic_rotation_curves