{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# Lec11 - Assignments For Friday 30 Sep Do Written HW#2...

This preview shows pages 1–9. Sign up to view the full content.

Assignments For Friday, 30 Sep: – Do Written HW #2 E xercise 07 ("Light & Spectroscopy" tutorial deferred to Monday, 03 Oct. – see updated course Calendar Extra help session today at 5:15 p.m. here in SHL131

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Newton’s Generalized Version of Kepler’s Third Law M + m = a 3 / P 2 where: M+m is combined mass of 2 orbiting bodies in Solar masses a is their mean separation in AU P is the period of their orbit in years This law is a key linchpin of modern astronomy!
Sample question 1. Two identical stars orbit each other with a period of 2 years and mean distance of 2 AU. In solar masses, what is the mass of EACH star? a. 1 b. 1/2 c. 4 d. 2

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Earth’s orbit from a star Suppose you observe the earth’s orbit with radius s=1 AU from a star at distance D. The angular size would be very small, about 1 arcsec = (1/3600) of a degree! Solve for the distance: a D s a s * For s=1 AU, a=1 arcsec, get: D = 1.5 x 10 8 km 360x3600/(2 π ) = 1.5 x 10 13 km = 3.26 l.y. This is defined to be 1 parsec (PC) 360 o D = s _____ 2 π a
Angle, distance, parallax a = 360 o s/2 π D • a arcsec = s au /D pc a = angular size (here in degrees) s = linear size D = distance a arcsec = angle in arcsec s au = separation size in au D pc = distance in parsec (pc) a D s a s

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Parallax For earth’s orbit with size/radius s =1 au, then a (in arcsec) represents the parallax angle to an star/object at distance D in parsec (pc). * a D s a s 1 D/ pc = ______ a/ arcsec
Parallax Ex. #1: Alpha Centauri is nearest star – parallax angle a=0.7 arcsec – distance D = 1/0.7 = 1.3 pc Ex.#2: Star at D=10 pc – parallax angle a= 1/10 = 0.1 arcsec

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Parallax Ex. #1: Alpha Centauri is nearest star – parallax angle a=0.7 arcsec
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 38

Lec11 - Assignments For Friday 30 Sep Do Written HW#2...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online