4 ms·

> ESO ... has taken the first direct image of a planetary system around a star like our Sun, located about 300 light-years away... > The two gas giants orbit t

> ESO ... has taken the first direct image of a planetary system around a star like our Sun, located about 300 light-years away... > The two gas giants orbit their host star at distances of 160 and about 320 times the Earth-Sun distance. For our purposes, a parsec [pc] is 3 ly, so the host star is at 100 pc. The inner planet is at 160 AU, which we'll round to 100 AU. So the angular separation is 100 AU / 100 pc = 1 AU/pc = 1 arcsec, and their resolution must exceed this. And then we have this handy chart: https://astronomy.stackexchange.com/questions/20695/how-big-is-one-arcsecond-at-various-distances https://astronomy.stackexchange.com/questions/20695/how-big-... This illustrates that the key issue is not resolution itself. It's contrast, at this high resolution. Because the planet must be distinguished from the host star. I don't know what the contrast difference here is. For Earth-like exoplanets (smaller targets at 1AU), the contrast difference is 10^10. That is, for every 10 billion photons from the host star, you get one reflected from the exoplanet. [edited to add: using the link provided by @teraflop, Table 1, column 3 seems to show a contrast of about 10-12 in magnitude units, which is 10^4 to 10^5 in physical units like photons]

raducu 6y ago
300 AU? Isn't that exeedingly far? Like 10 times farther away from Pluto? Would we even be able to detect such a planet if it orbited the Sun?
- vl 6y ago
  In the article they say that these planets are young and hot and they detected them in infrared by blocking light from the host star using special device. We would easily detect such super-massive hot planet at 300 AU in the solar system, but there is no reason for them to exist here since solar system is much older.
  - raducu 6y ago
    I was thinking that in out case hot or cold is not the main issue, but the area where to look. If you look at a star 300 light years away, you just have to search a couple of pixels away from the star. But if you searched for such a planet at 300 AU from out Sun, you would have a massive amount of space to search throug -- like a massive cilindrical wall of space around the Sun(if it was not exactly on our plane around the Sun). But in anycase, I was wondering if we had such a planet in our solar system, but obviously cold by now, could we detect it?
    - riidom 6y ago
      If it has a gravitational influence on other planets, then yes, same way as the discovery of Neptune. https://en.wikipedia.org/wiki/Discovery_of_Neptune https://en.wikipedia.org/wiki/Discovery_of_Neptune Now, 300 AU is far away, but then, 14 times the mass of jupiter is heavy. But I'm not knowledged enough to do the math here. On a 2nd thought, maybe not. How long would a year be for a planet that far outside? Maybe several hundred years? We'd need to be in the right window of time to spectate such effects in first place.
      - cgriswald 6y ago
        To be equivalent to the gravitational impact of Neptune the mass would have to be about 70,000 times the mass of Neptune. This is more equivalent to trying to find Planet Nine [0], which, although was also “discovered” through gravitational effects, those effects are much subtler and the planet might not exist and if it does, hasn’t been found. [0] - https://en.m.wikipedia.org/wiki/Planet_Nine https://en.m.wikipedia.org/wiki/Planet_Nine
    - nitrogen 6y ago
      (if it was not exactly on our plane around the Sun) On that matter, are there any significant objects (natural or artificial) orbiting way outside the plane of the solar system?
      - Cogito 6y ago
        Pluto is inclined at 17 degrees to the ecliptic plant. Haley's Comet is inclined at -18 degrees, and is highly elliptic which means that most of the time it is south of the ecliptic plane. The Kuiper Belt and Scattered Disk have a lot of objects inclined to the ecliptic, you can see a distribution here [0]. This [1] list has some even more inclined objects. [0] https://en.wikipedia.org/wiki/Scattered_disc#/media/File:TheKuiperBelt_Projections_100AU_Classical_SDO.svg https://en.wikipedia.org/wiki/Scattered_disc#/media/File:The... [1] https://en.wikipedia.org/wiki/List_of_exceptional_asteroids#Highly_inclined https://en.wikipedia.org/wiki/List_of_exceptional_asteroids#...
      - 6y ago
  - mturmon 6y ago
    Just to emphasize one point you made: It appears the first companion planet (160 AU) was originally detected using direct imaging last year (preprint [1] is dated Dec 2019, see sec. 4 for methods). And I guess the second one was announced in OP, making it a multi-planet system. The point of this comment is to note that these 2 planets were originally detected by direct imaging, not by other techniques. [1] https://arxiv.org/pdf/1912.04284.pdf https://arxiv.org/pdf/1912.04284.pdf

raducu 6y ago

300 AU? Isn't that exeedingly far? Like 10 times farther away from Pluto? Would we even be able to detect such a planet if it orbited the Sun?

vl 6y ago
In the article they say that these planets are young and hot and they detected them in infrared by blocking light from the host star using special device. We would easily detect such super-massive hot planet at 300 AU in the solar system, but there is no reason for them to exist here since solar system is much older.
- raducu 6y ago
  I was thinking that in out case hot or cold is not the main issue, but the area where to look. If you look at a star 300 light years away, you just have to search a couple of pixels away from the star. But if you searched for such a planet at 300 AU from out Sun, you would have a massive amount of space to search throug -- like a massive cilindrical wall of space around the Sun(if it was not exactly on our plane around the Sun). But in anycase, I was wondering if we had such a planet in our solar system, but obviously cold by now, could we detect it?
  - riidom 6y ago
    If it has a gravitational influence on other planets, then yes, same way as the discovery of Neptune. https://en.wikipedia.org/wiki/Discovery_of_Neptune https://en.wikipedia.org/wiki/Discovery_of_Neptune Now, 300 AU is far away, but then, 14 times the mass of jupiter is heavy. But I'm not knowledged enough to do the math here. On a 2nd thought, maybe not. How long would a year be for a planet that far outside? Maybe several hundred years? We'd need to be in the right window of time to spectate such effects in first place.
    - cgriswald 6y ago
      To be equivalent to the gravitational impact of Neptune the mass would have to be about 70,000 times the mass of Neptune. This is more equivalent to trying to find Planet Nine [0], which, although was also “discovered” through gravitational effects, those effects are much subtler and the planet might not exist and if it does, hasn’t been found. [0] - https://en.m.wikipedia.org/wiki/Planet_Nine https://en.m.wikipedia.org/wiki/Planet_Nine
  - nitrogen 6y ago
    (if it was not exactly on our plane around the Sun) On that matter, are there any significant objects (natural or artificial) orbiting way outside the plane of the solar system?
    - Cogito 6y ago
      Pluto is inclined at 17 degrees to the ecliptic plant. Haley's Comet is inclined at -18 degrees, and is highly elliptic which means that most of the time it is south of the ecliptic plane. The Kuiper Belt and Scattered Disk have a lot of objects inclined to the ecliptic, you can see a distribution here [0]. This [1] list has some even more inclined objects. [0] https://en.wikipedia.org/wiki/Scattered_disc#/media/File:TheKuiperBelt_Projections_100AU_Classical_SDO.svg https://en.wikipedia.org/wiki/Scattered_disc#/media/File:The... [1] https://en.wikipedia.org/wiki/List_of_exceptional_asteroids#Highly_inclined https://en.wikipedia.org/wiki/List_of_exceptional_asteroids#...
    - 6y ago
- mturmon 6y ago
  Just to emphasize one point you made: It appears the first companion planet (160 AU) was originally detected using direct imaging last year (preprint [1] is dated Dec 2019, see sec. 4 for methods). And I guess the second one was announced in OP, making it a multi-planet system. The point of this comment is to note that these 2 planets were originally detected by direct imaging, not by other techniques. [1] https://arxiv.org/pdf/1912.04284.pdf https://arxiv.org/pdf/1912.04284.pdf