Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Two-Faced Star Exposed

caltech.edu

Post reply on HN
Print view View original

11–18 of 18 posts

Re: Two-Faced Star Exposed

#11

Post by ithkuil »

kjs3 wrote: post #10
riskable wrote: post #8

Could it be that it's not actually a white dwarf? Perhaps we're making the wrong assumption because it gives off light like a white dwarf and the surface that we see appears to be hydrogen and helium based on spectrometry. Maybe it's a planet that had its atmosphere ignited? That way it could have a super strong magnetic (iron) core while the exterior would appear like that of a white dwarf. This would explain a magn…

Maybe it's a planet that had its atmosphere ignited? Because a white dwarf is about 250,000 times as dense as a planet, with the associated higher gravity, which you can measure at distance. And the magnetic field looks to be a couple of orders of magnitude higher than you could get from a 'normal matter' iron core, no matter how fast you spin it. And the hydrogen and helium are fusing, not burning, and planets don't…

How can we measure the gravitational field of such a distant object?

Re: Two-Faced Star Exposed

#12

Post by danparsonson »

kjs3 wrote: post #10
riskable wrote: post #8

Could it be that it's not actually a white dwarf? Perhaps we're making the wrong assumption because it gives off light like a white dwarf and the surface that we see appears to be hydrogen and helium based on spectrometry. Maybe it's a planet that had its atmosphere ignited? That way it could have a super strong magnetic (iron) core while the exterior would appear like that of a white dwarf. This would explain a magn…

Maybe it's a planet that had its atmosphere ignited? Because a white dwarf is about 250,000 times as dense as a planet, with the associated higher gravity, which you can measure at distance. And the magnetic field looks to be a couple of orders of magnitude higher than you could get from a 'normal matter' iron core, no matter how fast you spin it. And the hydrogen and helium are fusing, not burning, and planets don't…

Sorry - I don't mean to shoot you down, but while your overall point is correct, those are not the reasons we know why:

1) We can only estimate gravitational fields remotely when objects are interacting, by measuring the time it takes them to orbit each other - the article specifically says that the object is "floating alone in space".

2) The paper (https://assets.researchsquare.com/files/rs-2029380/v1_covere...) discusses the possibility of a magnetic field being responsible for the two-sided effect, but doesn't mention that they specifically measured it. Apparently measurement is possible for large magnetic fields by looking for circular polarisation but I don't think they have found that in this case.

3) There is no fusion happening in a white dwarf - they glow with residual heat from the original star.

Wikipedia has a lot of detail in their article: https://en.wikipedia.org/wiki/White_dwarf

Re: Two-Faced Star Exposed

#13

Post by danparsonson »

riskable wrote: post #8

Could it be that it's not actually a white dwarf? Perhaps we're making the wrong assumption because it gives off light like a white dwarf and the surface that we see appears to be hydrogen and helium based on spectrometry. Maybe it's a planet that had its atmosphere ignited? That way it could have a super strong magnetic (iron) core while the exterior would appear like that of a white dwarf. This would explain a magn…

If you're willing to invoke 'alien technology' as an explanation then no-one could really argue differently because we don't know what aliens are capable of. A few things that come to mind:

a) That seems like an awful lot of trouble to go to when you could surely directly harvest the energy of a star much more easily, and use that to drive whatever machinery you wanted to build.

b) How would one ignite an atmosphere and once having done so, keep it burning? Would it not all burn up in a short time? Say a few weeks at most?

c) You can't fool a spectrum - the light coming from such an object would indicate its chemical composition; if it looks like primarily H and He then that's what it is. Planetary atmospheres tend to be low in those elements because they get blown away over time.

d) As another commenter points out, the magnetic field of a planet is tiny in comparison to that required for the effect the paper is postulating - Earth's magnetic field strength for example is less than 1 gauss, whereas the scientists here are suggesting fields of a few thousands to a million gauss. Still not that high for a stellar object, but very high for a planet.

Of course I'd love for us to find evidence of aliens - but I don't think this is it.

Re: Two-Faced Star Exposed

#14

Post by kjs3 »

danparsonson wrote: post #12
kjs3 wrote: post #10

Earlier quoted context omitted.

Maybe it's a planet that had its atmosphere ignited? Because a white dwarf is about 250,000 times as dense as a planet, with the associated higher gravity, which you can measure at distance. And the magnetic field looks to be a couple of orders of magnitude higher than you could get from a 'normal matter' iron core, no matter how fast you spin it. And the hydrogen and helium are fusing, not burning, and planets don't…

Sorry - I don't mean to shoot you down, but while your overall point is correct, those are not the reasons we know why: 1) We can only estimate gravitational fields remotely when objects are interacting, by measuring the time it takes them to orbit each other - the article specifically says that the object is "floating alone in space". 2) The paper ( https://assets.researchsquare.com/files/rs-2029380/v1_covere... ) d…

I stand corrected. I definitely missed the "floating alone in space" part...for some reason I got in my head there was a companion.

Re: Two-Faced Star Exposed

#15

Post by danparsonson »

kjs3 wrote: post #14
danparsonson wrote: post #12

Earlier quoted context omitted.

Sorry - I don't mean to shoot you down, but while your overall point is correct, those are not the reasons we know why: 1) We can only estimate gravitational fields remotely when objects are interacting, by measuring the time it takes them to orbit each other - the article specifically says that the object is "floating alone in space". 2) The paper ( https://assets.researchsquare.com/files/rs-2029380/v1_covere... ) d…

I stand corrected. I definitely missed the "floating alone in space" part...for some reason I got in my head there was a companion.

They did discuss that possibility, at least in the paper, and it was my first thought for an explanation, but I think they discounted it because it would require an unrealistic or impossible orbit.

Re: Two-Faced Star Exposed

#16

Post by kjs3 »

danparsonson wrote: post #15
kjs3 wrote: post #14

Earlier quoted context omitted.

I stand corrected. I definitely missed the "floating alone in space" part...for some reason I got in my head there was a companion.

They did discuss that possibility, at least in the paper, and it was my first thought for an explanation, but I think they discounted it because it would require an unrealistic or impossible orbit.

I jumped to a similar conclusion. Not my best post.

Re: Two-Faced Star Exposed

#17

Post by kjs3 »

ithkuil wrote: post #11
kjs3 wrote: post #10

Earlier quoted context omitted.

Maybe it's a planet that had its atmosphere ignited? Because a white dwarf is about 250,000 times as dense as a planet, with the associated higher gravity, which you can measure at distance. And the magnetic field looks to be a couple of orders of magnitude higher than you could get from a 'normal matter' iron core, no matter how fast you spin it. And the hydrogen and helium are fusing, not burning, and planets don't…

How can we measure the gravitational field of such a distant object?

Influence on the movement relative to closeby objects. But as astutely pointed out above, I'm wrong here because the paper thinks there's no closeby objects.

Re: Two-Faced Star Exposed

#18

Post by danparsonson »

kjs3 wrote: post #16
danparsonson wrote: post #15

Earlier quoted context omitted.

They did discuss that possibility, at least in the paper, and it was my first thought for an explanation, but I think they discounted it because it would require an unrealistic or impossible orbit.

I jumped to a similar conclusion. Not my best post.

Happens to the best of us :-)

https://xkcd.com/1053/

Post reply on HN