# PCS 181 Lecture Notes - Quasar, Angular Diameter

23 views3 pages
School
Ryerson University
Department
Physics
Course
PCS 181 PCS 181
Page 1
PCS 181
Thursday, February-07-13
Class 7
Similarly, 3C48 quasars are known and all are extremely red-shifted
What is the distance to 3C273:
d= Vr/Ho
d= (4.8*10^4km/s)/(75km/s/Mpc)
d= 640Mpc
d= (640*10^16pc)(3.26ly) = 2.09*10^9ly
d= 2 billion ly away
Relativistic Velocity Equation
Consider one of the fastest, most distant quasars at Z=5.82
Since Vr = cz, is this quasar moving at 5.82 times the speed of light?
No, no material object can exceed the speed of light
For z > 0.5, we turn to relativity
Relativistic velocity formula: Vr = ((z-1)^2)-1) *c
((z+1)^2)+1)
Ex: z = 5.82
((5.82-1)^2)-1) *c
((5.82-1)^2)-1)
=(45.51) *c
(47.51)
=0.958*c = 96% the speed of light (3*10^8 m/s)
Distance to the Quasar
If the Hubble law is valid, this quasar must be very far away
D =V/Ho
= ((0.958(3*10^5km/s))
75km/s
D= 3832Mpc = 12.5*10^9ly
D = 12.5 billion ly away
To see quasars over such vast (“cosmological”) distances, they must be intrinsically very bright
Quasars often emit as much energy as 100-1000normal galaxies combined
The size may be determined by a technique known as Lunar Occultation
Apparent size of a quasar: d = vt =
Unlock document

This preview shows page 1 of the document.
Unlock all 3 pages and 3 million more documents.

## Document Summary

Similarly, 3c48 quasars are known and all are extremely red-shifted. What is the distance to 3c273: d= vr/ho d= (4. 8*10^4km/s)/(75km/s/mpc) d= 640mpc d= (640*10^16pc)(3. 26ly) = 2. 09*10^9ly d= 2 billion ly away. Consider one of the fastest, most distant quasars at z=5. 82. No, no material object can exceed the speed of light. For z > 0. 5, we turn to relativity. Relativistic velocity formula: vr = ((z-1)^2)-1) *c ((z+1)^2)+1) Ex: z = 5. 82 ((5. 82-1)^2)-1) *c ((5. 82-1)^2)-1) =0. 958*c = 96% the speed of light (3*10^8 m/s) If the hubble law is valid, this quasar must be very far away. To see quasars over such vast ( cosmological ) distances, they must be intrinsically very bright. Quasars often emit as much energy as 100-1000normal galaxies combined. The size may be determined by a technique known as lunar occultation. Apparent size of a quasar: d = vt = After we connect for the distance to the quasar, we find that: