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> “Nor is there any information yet that indicates the star has a rich planetary system like ours.” Could it just be that, if there are any planets around Pro

> “Nor is there any information yet that indicates the star has a rich planetary system like ours.” Could it just be that, if there are any planets around Proxima Centauri, they don't transit the star as observed from Earth? Or is there other data suggesting the absence of planets?

goodcanadian 9y ago
I think the implication is that the stellar activity cleared the dust from the system preventing planets from forming.
KodiakLabs 9y ago
The passing of exoplanets (planets outside or solar system) if front of the host star is not the only way to detect the planets. The most common method used to be the Radial Velocity method. Essentially, planets and stars orbit a common center of mass (which often lies witching the star’s radius). This effect essentially wobbles the parent star. Because we know the constituents of the star and it’s spectrum, this wobble causes a period red and blue shift (the Doppler effect). From the magnitude of this effect you can describe a lot of the planet’s orbit, but not everything. For example: you can describe the minimum mass of the planet but not the actual mass. I’m not sure if the have used the radial velocity method of this star, but assume they would have.
- kazagistar 9y ago
  You can't see a doppler shift if the pole of the orbit is facing sol, right? So there are still systems with invisible planets.
  - roywiggins 9y ago
    You can measure the position of the star in the sky and use that to detect systems that are "face on" to us (with the axis pointing at us) but it's harder. http://www.planetary.org/explore/space-topics/exoplanets/astrometry.html http://www.planetary.org/explore/space-topics/exoplanets/ast...
    - martinpw 9y ago
      Sounds like 'harder' is an understatement - according to that article no planets have been discovered with this technique, and it is unlikely to yield any discoveries any time soon. (Technique is to directly observe the star wobbling in space rather than measure doppler shifts.)
  - KodiakLabs 9y ago
    You are correct. A component of the velocity of the wobble has to be in the line of sight. If not, it would be an edge case.
fjfaase 9y ago
In the abstract, it says that they conclude this from the absent of "quiescent excess emission". I do not know what this exactly means, could not find an explaination for it, but maybe it is a technical term for "light echo" or something related to it. If a star suddenly becomes 1000x brighter, one would expect that after some time, planets and dust would also light up after the star has returned to normal brightness. https://en.wikipedia.org/wiki/Light_echo https://en.wikipedia.org/wiki/Light_echo
- kwoff 9y ago
  The web page links to a journal article that you have to pay for, but you can find the freely-readable version of the full article at https://arxiv.org/abs/1802.08257 https://arxiv.org/abs/1802.08257 . Section 4.2 discusses dust emission. The original paper they're correcting is at https://arxiv.org/abs/1711.00578 https://arxiv.org/abs/1711.00578 (section 3.2). This paper concludes that the previous paper had wrong assumptions because a flare happened during their measurement, so they didn't need to hypothesize that there is a dust belt (at least the 2 inner ones; they didn't have info about the far outer belt) to account for the supposed "excess emission".
bonzini 9y ago
Planetary systems are more rare around binary systems and planets are smaller too (making them harder to detect). Proxima Centauri is the smallest star in a triple system.

goodcanadian 9y ago

I think the implication is that the stellar activity cleared the dust from the system preventing planets from forming.

KodiakLabs 9y ago

The passing of exoplanets (planets outside or solar system) if front of the host star is not the only way to detect the planets. The most common method used to be the Radial Velocity method. Essentially, planets and stars orbit a common center of mass (which often lies witching the star’s radius). This effect essentially wobbles the parent star. Because we know the constituents of the star and it’s spectrum, this wobble causes a period red and blue shift (the Doppler effect). From the magnitude of this effect you can describe a lot of the planet’s orbit, but not everything. For example: you can describe the minimum mass of the planet but not the actual mass. I’m not sure if the have used the radial velocity method of this star, but assume they would have.

kazagistar 9y ago
You can't see a doppler shift if the pole of the orbit is facing sol, right? So there are still systems with invisible planets.
- roywiggins 9y ago
  You can measure the position of the star in the sky and use that to detect systems that are "face on" to us (with the axis pointing at us) but it's harder. http://www.planetary.org/explore/space-topics/exoplanets/astrometry.html http://www.planetary.org/explore/space-topics/exoplanets/ast...
  - martinpw 9y ago
    Sounds like 'harder' is an understatement - according to that article no planets have been discovered with this technique, and it is unlikely to yield any discoveries any time soon. (Technique is to directly observe the star wobbling in space rather than measure doppler shifts.)
- KodiakLabs 9y ago
  You are correct. A component of the velocity of the wobble has to be in the line of sight. If not, it would be an edge case.

fjfaase 9y ago

In the abstract, it says that they conclude this from the absent of "quiescent excess emission". I do not know what this exactly means, could not find an explaination for it, but maybe it is a technical term for "light echo" or something related to it. If a star suddenly becomes 1000x brighter, one would expect that after some time, planets and dust would also light up after the star has returned to normal brightness. https://en.wikipedia.org/wiki/Light_echo https://en.wikipedia.org/wiki/Light_echo

kwoff 9y ago
The web page links to a journal article that you have to pay for, but you can find the freely-readable version of the full article at https://arxiv.org/abs/1802.08257 https://arxiv.org/abs/1802.08257 . Section 4.2 discusses dust emission. The original paper they're correcting is at https://arxiv.org/abs/1711.00578 https://arxiv.org/abs/1711.00578 (section 3.2). This paper concludes that the previous paper had wrong assumptions because a flare happened during their measurement, so they didn't need to hypothesize that there is a dust belt (at least the 2 inner ones; they didn't have info about the far outer belt) to account for the supposed "excess emission".

bonzini 9y ago

Planetary systems are more rare around binary systems and planets are smaller too (making them harder to detect). Proxima Centauri is the smallest star in a triple system.