Cymek said:
mollwollfumble said:
mollwollfumble said:
Pulsating white dwarfs exist, and are found along the same line of instability in the HR diagram as mira (long term variables) and RR Lyrae variables. They are known as ZZ Ceti type white dwarfs. Or type DAV.
It’s not clear from the OP whether it is these that are being referred to, because they don’t need an adjacent red dwarf in order to pulsate.
Indeed, pulsing white dwarfs were known before the first pulsars were discovered. The first pulsars were thought to be pulsating white dwarfs until observations proved otherwise.
> “White dwarf stars are the most common stellar fossils. When in binaries, they make up the dominant form of compact object binary within the Galaxy and can offer insight into different aspects of binary formation and evolution. One of the most remarkable white dwarf binary systems identified to date is AR Scorpii (AR Sco). AR Sco is composed of an M dwarf star and a rapidly spinning white dwarf in a 3.56 h orbit. It shows pulsed emission with a period of 1.97 min over a broad range of wavelengths, which led to it being known as a white dwarf pulsar. Both the pulse mechanism and the evolutionary origin of AR Sco provide challenges to theoretical models. Here we report the discovery of a sibling of AR Sco, J191213.72-441045.1, which harbours a white dwarf in a 4.03 h orbit with an M dwarf and exhibits pulsed emission with a period of 5.30 min. This discovery establishes binary white dwarf pulsars as a class and provides support for proposed formation models for white dwarf pulsars.”
It would have to be a very close binary to generate pulses in that way, but that’s certainly not impossible.
With us humans removed both in space and time what sort of error margin creeps in with our observations.
Is the theory in need of tweaking or can the observation be flawed because of the distance and our technological limitations.
There are three methods to measure stars that I know of.
1 Distance to stars is measured by parallax
https://lco.global/spacebook/distance/parallax-and-distance-measurement/
Stellar parallax diagram, showing how the ‘nearby’ star appears to move against the distant ‘fixed’ stars when Earth is at different positions in its orbit around the Sun. Image credit: Alice Hopkinson, LCO
2 Measuring the Brightness of Stars
https://astrocamp.org/blog/brightness-of-stars/
We measure the brightness of these stars using the magnitude scale. The magnitude scale seems a little backwards. The lower the number, the brighter the object is; and the higher the number, the dimmer it is. This scale is logarithmic and set so that every 5 steps up equals a 100 times decrease in brightness.
https://science.howstuffworks.com/question224.htm
There is no direct method currently available to measure the distance to stars farther than 400 light years from Earth, so astronomers instead use brightness measurements. It turns out that a star’s color spectrum is a good indication of its actual brightness. The relationship between color and brightness was proven using the several thousand stars close enough to earth to have their distances measured directly. Astronomers can therefore look at a distant star and determine its color spectrum. From the color, they can determine the star’s actual brightness. By knowing the actual brightness and comparing it to the apparent brightness seen from Earth (that is, by looking at how dim the star has become once its light reaches Earth), they can determine the distance to the star.
3 Using Gravitational Lensing to Measure Age and Size of Universe
https://www.universetoday.com/58488/using-gravitational-lensing-to-measure-age-and-size-of-universe/