White Dwarf Binaries

I decided to create a separate page focusing on Binary systems in which one or both of the components is a White Dwarf star. White Dwarfs stars are fascinating celestial objects. In fact when you think about it they really aren’t stars at all – they are not burning or consuming fuel through nuclear fusion but are the solidified white-hot remnant of a dead star. White Dwarfs are incredibly dense objects; they can be nearly as massive as our sun but are squeezed down to the size of the earth due to their end-stage gravitational collapse. They will gradually radiate their latent heat for billions, if not trillions, of years before becoming a cold dark crystallized mass. Because they are small and not very luminous, they are very faint objects – we can only see those that are relatively close to our Solar System. When viewing any binary system that contains a White Dwarf it should be kept in mind that at an earlier time in the evolutionary history of the system, that the White Dwarf was the more massive and more luminous star.

Where spectral types are listed on the photos below, White Dwarf Stars will have a “D” prefix.

  • DA – a hydrogen-rich atmosphere or outer layer.
  • DB – a helium-rich atmosphere, indicated by neutral helium.
  • DO – a helium-rich atmosphere, indicated by ionized helium.
  • DQ – a carbon-rich atmosphere, indicated by atomic or molecular carbon lines.
  • DZ – a metal-rich atmosphere, indicated by metal spectral lines.
  • DC – no strong spectral lines indicating one of the above categories.
  • DX – spectral lines are insufficiently clear to classify into one of the above categories.

Where the “D” spectral-type of the White Dwarf is followed by a number (N) this reflects the effective surface temperature of the white dwarf in degrees Kelvin according to the equation : (Teff = 50400/N).

The Brightest star in the night sky – Alpha Canis Major also named “Sirius” – is a Binary system whose diminutive companion is both the closest and one of the most massive White Dwarf stars known. Sirius B currently has a mass equal to that of the Sun but started out with a mass 5 times that. Sirius A on the other hand, currently has a mass only 2.1 times that of the Sun. For more information on this fascinating pair I will refer you to the article “Why So Sirius?“.
40 Eridani is one of the most beautiful triple star systems and contains the second brightest and perhaps the most easily viewed White Dwarf star. This is one system that I can’t resist looking back in time and try to imagine what this system looked like when the White Dwarf was the brightest and most massive star of the trio.
* * *
* * *
GRV 1037 is wide Red-Dwarf / White-Dwarf Binary.
* * *
The soft blue glow of both components of the faint binary system GWP 650 is characteristic of White Dwarf stars.
* * *
* * *
* * *
* * *
* * *
Hip 38594 also known as Ross 429, is an early type M dwarf star with a White Dwarf companion. It also has two super-earth type planets orbiting around it (HIP 38594b & HIP 38594c). The closer of the two planets – HIP 38594b – lies within the “Habitable Zone” of the star with a mass ~9 times that of earth and an orbital period of 60 days.
LDS 275 is another binary system where both components are White Dwarf stars. The magnitudes and separation of this pair would suggest that this would not be a particularly difficult system to photograph, but from my location this very southerly system rises only 12 degrees above my local horizon as well as being enveloped by the light-dome of the city of Castle Rock. Despite these challenges this stacked image (17 frames x 30 sec) captures the soft blue glow of the White Dwarfs as well as the elongation of the system.
Here is my most recent capture of a white dwarf binary system which shows a very nice color contrast between the White Dwarf primary and its M5 companion. The nearby system moves at a rate of 0.17 arc-sec per year.
* * *
* * *
* * *
* * *
* * *
The binary system LDS 1222 is very similar in many particulars (distance, magnitudes, and separation) to LDS 3742 above.
* * *
* * *
* * *
* * *
This White Dwarf binary contrasts markedly from the Sirius binary system since the companion star is a very low-mass, low-luminosity Red Dwarf Star. Here both stars are roughly equal in mass (~1/2 Msun) though the Red Dwarf is still much larger in size (~ 1/2 Rsun) and is still consuming its store or hydrogen through nuclear fusion. At magnitude 16 these stars are very faint – the photo above was taken through my C9.25 SCT using a 50 second exposure.
* * *
* * *
* * *
* * *
FAR 9 appears to resemble some of the other physical White-Dwarf/Red-Dwarf pairs shown above. In this case though, while their proper motions are similar in magnitude and direction, they are separated from each other by nearly 200 light-years.
* * *
* * *
* * *
* * *
Farihi 45 is a triple system made up of a White Dwarf primary and two Red Dwarf companions – only one of which is resolved in my photo.