December 16, 2018

Astro-Event of the Week: Can You Spy Sirius B?

This week’s challenge is a tough one, and may deserve a re-visit or two over the coming decade  to yield success. Everyone knows that Sirius is this brightest star in the sky, but did you know that it has a tiny, elusive white dwarf companion? Tough to locate, this +8.7 magnitude object currently lies at an apparent separation of 9” arc seconds and growing. Usually, that wouldn’t be a tough split, except for the fact that bright Sirius A swamps it out by its -1.42 magnitude brightness! To spot it, you’ll need a telescope of at least 4” aperture, high magnification, and clear, pristine skies. Also, an eyepiece equipped with an occulting bar could prove helpful; the trick is to cover up the bright primary to the northeast while Sirius B lies to the left at a south western position angle.

The waxing Moon shouldn’t interfere too much with this endeavor, as it involves high magnification. Use Rigel in the foot of Orion as a test star as it is also a magnitude contrast binary, although one much easier to split. At its closest, Sirius B is only 3” seconds of separation; this last happened in 1994 and will happen again in 2043 once Sirius B completes one 50 year orbit. Maximum separation of 11.5” arc seconds occurs in 2025. Never seen it? We’re right there with you, although we’ll be looking to add it to our life list in the coming decade!

…And yes, we know of the myth of the Dogon and their “knowledge” of the Dog Star… trust me, this fascinating tale can and will fill a future blog post!

The Astro-word for this week is Degenerate Matter. No, we’re not talking about the moral status of a star; this state occurs in white dwarf stars like Sirius B when the density of the collapsed star rises to a point that the pressure from the Pauli Exclusion Principle is the only outward force supporting the star from total collapse. The force of electron degeneracy occurs in the final white dwarf stage of a star’s life up to about 1.44 solar masses. White dwarfs simply dissipate energy via radiation, like slowly cooling cinders. Eventually, they will cool to a point where they stop shining, known theoretically as a black dwarf.  The period for this to occur, however, is calculated to be 1015 years, much longer than the current age of the universe!

Trackbacks

  1. [...] is the nearest white dwarf to the Earth at 8.6 light years distant. Shining at magnitude +8.5, Sirius B would be a cinch to see, if only dazzling Sirius A — the brightest star in our sky at magnitude [...]

  2. [...] is the nearest white dwarf to the Earth at 8.6 light years distant. Shining at magnitude +8.5, Sirius B would be a cinch to see, if only dazzling Sirius A — the brightest star in our sky at magnitude [...]

  3. [...] approaches, we challenge you to see of the most famous white dwarf of them all, as it reaches a favorable viewing position over the next few years: Sirius B. Sirius A and B in x-rays courtesy of Chandra. Credit: [...]

Speak Your Mind

*