Lab 6 – The Earth’s Orbital VelocityLab 6 – The Earth’s Orbital Velocity

My radial velocity is 0

mph?

V = 80 mph V = 80 mph

I’m approaching the bus at 20

mph.

I’m receding from the

ambulance at 20 mph.

V = 40 mph V = 60 mph

I’m approaching the sports car at

160 mph?

V = 80 mph V = 80 mph

V = 60 mph V = 40 mph

Vstar

Arcturus

VA

VB

? ?

VA = Vstar + Vearth

VB = Vstar - Vearth

Vo

ArcturusV

To Ecliptic

 Vearth = 1/2(VA - VB)/0.86

 Vstar = 1/2(VA + VB)

Vearth = 1/2(VA - VB)

 Vstar = 1/2(VA + VB) 

- Vearth

+ Vearth

Earth Distant Star

Laboratory - No Radial motion

Radial Velocity = 0

Radial Velocity -

Radial Velocity +

Laboratory Spectrum

Blueshift

Redshift

Spectral Lines Match

o

or

cv

Arcturus

VA

VB

? ?

0A λ

Δλcv

o

RedRedBlueBlue

Measure for Plate Scale

-0.15-0.15

4260.48 A4260.48 A4307.91 A4307.91 A

A

cm 0.41

A4260.48-4307.91

(cm) 7 and 1 between distanceP.S.

-0.37-0.37

km/s 25.6 A4294.13

A)0.37km/s 300,000

λ

ΔλcvB

(

-25.6-25.60.37Acm/A 0.41

cm 0.15-

r

Vearth

Finding the Radius of the Earth’s OrbitFinding the Radius of the Earth’s Orbit

Circumference of the Earth's Orbit = 2r Vearth = distance/time time =1 year,

distance = 2r

Vearth = 2r / time

r = (Vearth X time)/2

The EndThe End