點樣知道同第2個星體距離幾遠同質量

-終場ソ使者-

哈,離晒題-.-

john456

咁不如
我開左post厄多5分~_~
好唔好?

john456

呢度唔係大學區- -
p445hkk20001 發表於 12-9-2010 18:32

中學物理4個選修項目入面好似有一個係關星體太空事

-終場ソ使者-

中學物理4個選修項目入面好似有一個係關星體太空事
john456 發表於 12-9-2010 19:00

長遠左D喎-.-

p445hkk20001

中學物理4個選修項目入面好似有一個係關星體太空事
john456 發表於 12-9-2010 05:00 AM

選修無咁快讀架

john456

我都唔知啊囧

[H]bunbunbunbun

Distance between earth and star can be measured by the difference between the angle observed at different times with reference to other background stars (assuming that the background stars are stationary)

Mass of a star can be measured by the doppler effect (i.e. red shift/blue shift)
this method measures the wavelength of light emitted by the star, which changes over time due to circular motion. (change in wavelength/actual wavelength = velocity/speed of light)
with the calculated velocity and the period, you can calculate the semimajor axis of orbit.
Then you can use Kepler's third law to fin the mass of the binary system (stars move in pairs, so you'll have to find the doppler shift of the other star/ assume one is neglectable in order to find the mass of a particular star.)

john456

Distance between earth and star can be measured by the difference between the angle observed at diff ...
[H]bunbunbunbun 發表於 13-9-2010 17:36

有冇中文囧囧囧
小弟今年係第1年讀英理...

-終場ソ使者-

見到呢個POST好想答番添-.-
搵恆星既質量其實係要睇個粒恆星既星等(光度)
因為恆星既質量同該恆星既星等係有一個函數關係,d科學家研究左好耐plot左條graph
即係透過恆星既星等去搵番佢相對既質量
最大問題係,點樣搵一個恆星既星等(光度)呢?
因為當一個恆星離地球越遠,光度就會越暗,我地點樣知道佢既光度呢?
答案就係恆星放出黎既radiation,再透過分析佢既electromagnetic spectrum得知個星等
我地知所以見到物質,係因為佢放左d visibe radiation出黎,離地球好遠既恆星都係一樣
所以我地可以搵到恆星既質量
至於行星既質量就更加唔洗講,用簡單圓周運動既公式就可以搵到