[kjs3]

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 seem to support that (try as we might here on earth). So...pretty clear it's not a planet.

[danparsonson]

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

[kjs3]

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

[danparsonson]

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.

[kjs3]

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

[danparsonson]

Happens to the best of us :-)

https://xkcd.com/1053/

[ithkuil]

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

[kjs3]

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.