What blocks the light during the deep, irregular dips?
Most likely: clumps of fine dust orbiting the star, released by comets, planetesimals or other bodies close to itAhead on the evidence, not yet confirmed. It needs two reviews to be accepted.
Where it stands
Five answers have been proposed. Clumps of fine dust orbiting the star, released by comets, planetesimals or other bodies close to it. leads, with evidence 2 for, 2 against: supported by its tests. Four are still possible. Of the three narrower questions under it, none is answered yet.
Why it matters
The dips are the phenomenon that made the star famous and the one any explanation must reproduce: depths up to about 20 per cent, irregular shapes, no period, and no infrared excess[1]. The 2017 colour measurements narrowed the field to material that absorbs blue light more than red[2][3], but several sources of such material remain in play.
Answers 5
History
- Boyajian et al. puts forward: clumps of fine dust orbiting the star, released by comets, planetesimals or other bodies close to it.
- Wright & Sigurdsson puts forward: material between us and the star, not bound to it, such as structure in the interstellar medium or a small…
- Wright & Sigurdsson puts forward: variability of the star itself, for example in its photosphere, rather than an occulter.
- Wright et al. puts forward: large artificial structures orbiting the star.
- Boyajian et al.: there is no infrared excess, so there is no large reservoir of warm dust near the star.Against: Clumps of fine dust orbiting the star, released by comets, planetesimals or other bodies close to it.
- Boyajian et al.: dip ingress and egress times of days fit material moving at orbital speeds close to the star better than a…Against: Material between us and the star, not bound to it, such as structure in the interstellar medium or a small…
- Deeg et al.: grains this small are blown out by radiation pressure and must be renewed from a comoving body within days.Against: Clumps of fine dust orbiting the star, released by comets, planetesimals or other bodies close to it.
- Boyajian et al.: the 2017 dips were deeper in blue than red with no change in spectrum or polarisation; the authors favour…For: Clumps of fine dust orbiting the star, released by comets, planetesimals or other bodies close to it.
- Deeg et al.: gTC spectrophotometry gives an Ångström coefficient of 2.19 ± 0.45, consistent with grains of 0.0015 to 0.15…For: Clumps of fine dust orbiting the star, released by comets, planetesimals or other bodies close to it.
- Boyajian et al.: no change in the stellar spectrum or polarisation was seen during the 2017 dips.Against: Variability of the star itself, for example in its photosphere, rather than an occulter.
- Boyajian et al.: the 2017 campaign notes its data may also be consistent with variations intrinsic to the photosphere.For: Variability of the star itself, for example in its photosphere, rather than an occulter.
- Boyajian et al.: the 2017 dips were chromatic, which large opaque structures would not produce.Against: Large artificial structures orbiting the star.
- Session 1: worked on two of its sub-questions