csmyth3025

2011-Mar-02, 08:41 PM

I realize this thread is 3 years old, but it's the first one in the search list that specifically references the subject of my question, as follows:

I was reading about PSR J0737-3039 - a binary pair of pulsars - and I came across this table in Wikipedia:

Property..........................Pulsar A.............................Pulsar B

Spin period...................23 milliseconds..................2.8 seconds

Mass..........................1.337 solar masses..........1.250 solar masses

Orbital period 2.4 hours

(ref. http://en.wikipedia.org/wiki/PSR_J0737-3039#Known_double_pulsars)

I was wondering what effect frame dragging would have on this system. Do they appear to a distant observer (us) to be orbiting each other faster than their masses would otherwise indicate if they weren't rotating at such high rates?

I ask this because both components are massive, compact, have high spin rates (especially pulsar A) and are very close to each other (~about 800,000 km according to a related article here: http://www.skyandtelescope.com/news/3310106.html?page=1&c=y )

I tried using the formula for orbital periods to see what the orbital period without any frame dragging would be:

The mass would be (1.25+1.337)=~2.587 solar mass

The semi-major axis would be 400,000,000 meters

When I plug these numbers into the WolframAlpha site, I get 45.21 min.

(ref. http://www.wolframalpha.com/input/?i=orbital+period&a=*C.orbital+period-_*Formula.dflt-&a=*FS-_**KeplersThirdLaw.T-.*KeplersThirdLaw.a-.*KeplersThirdLaw.m1--&f3=4x10%5E8+m&f=KeplersThirdLaw.a_4x10%5E8+m&f4=2.659x10%5E30+kg&f=KeplersThirdLaw.m1_2.659x10%5E30+kg&f5=2.486x10%5E30+kg&f=KeplersThirdLaw.m2_2.486x10%5E30+kg&x=4&y=10 )

When I make this calculation on paper I come up with ~2700 seconds (~45 min.).

There's a bit of a difference between my calculation and the published orbital period :eek:

Can anyone tell me what I'm doing wrong?

This is my first post here, so if I've put it in the wrong place or made some other miss-step, please let me know.

Thanks,

Chris

I was reading about PSR J0737-3039 - a binary pair of pulsars - and I came across this table in Wikipedia:

Property..........................Pulsar A.............................Pulsar B

Spin period...................23 milliseconds..................2.8 seconds

Mass..........................1.337 solar masses..........1.250 solar masses

Orbital period 2.4 hours

(ref. http://en.wikipedia.org/wiki/PSR_J0737-3039#Known_double_pulsars)

I was wondering what effect frame dragging would have on this system. Do they appear to a distant observer (us) to be orbiting each other faster than their masses would otherwise indicate if they weren't rotating at such high rates?

I ask this because both components are massive, compact, have high spin rates (especially pulsar A) and are very close to each other (~about 800,000 km according to a related article here: http://www.skyandtelescope.com/news/3310106.html?page=1&c=y )

I tried using the formula for orbital periods to see what the orbital period without any frame dragging would be:

The mass would be (1.25+1.337)=~2.587 solar mass

The semi-major axis would be 400,000,000 meters

When I plug these numbers into the WolframAlpha site, I get 45.21 min.

(ref. http://www.wolframalpha.com/input/?i=orbital+period&a=*C.orbital+period-_*Formula.dflt-&a=*FS-_**KeplersThirdLaw.T-.*KeplersThirdLaw.a-.*KeplersThirdLaw.m1--&f3=4x10%5E8+m&f=KeplersThirdLaw.a_4x10%5E8+m&f4=2.659x10%5E30+kg&f=KeplersThirdLaw.m1_2.659x10%5E30+kg&f5=2.486x10%5E30+kg&f=KeplersThirdLaw.m2_2.486x10%5E30+kg&x=4&y=10 )

When I make this calculation on paper I come up with ~2700 seconds (~45 min.).

There's a bit of a difference between my calculation and the published orbital period :eek:

Can anyone tell me what I'm doing wrong?

This is my first post here, so if I've put it in the wrong place or made some other miss-step, please let me know.

Thanks,

Chris