Starship Asterisk*

Craig Willford wrote:It seems to me that if you compress all those planets inside the orbit of one AU, then the big ones (the ones the size of Jupiter and Saturn) would fling out of their orbits the other smaller ones. Since they are all in (relative) close proximity, it doesn't seem as though stable orbits for so many members in so small a volume would be possible.

MarkBour wrote:As I look at the chart for the Kepler-90 system here, it strikes me as a truncated version of our own planetary set. And it makes sense that the observations from transit photometry will be biased, at least at first. It will more easily find large planets and short orbits. So, if Kepler-90 actually has a planetary system that has peak masses in the "middle distance", then we have not (yet) been able to observe the smaller effects of a set of outer planets that might taper off in mass. They would have much longer orbits and much smaller occultation effects, so would be harder to detect. Indeed, we have enough trouble detecting outer planets in our own system, let alone by looking for a glimmer in a star that is about 2545 light years away.

The radial velocity detection technique would be biased in about the same way as the star dimming technique.

FLPhotoCatcher wrote:... I notice the Kepler-90 planets are all labeled, but 'our' planets are not. I guess we can all remember our planets by the silly sentence, "My Very Enthusiastic Mother Just Served Us Noodles!" Kepler-90's planets? Hmmm...

Craig Willford wrote:It seems to me that if you compress all those planets inside the orbit of one AU, then the big ones (the ones the size of Jupiter and Saturn) would fling out of their orbits the other smaller ones. Since they are all in (relative) close proximity, it doesn't seem as though stable orbits for so many members in so small a volume would be possible.

Wikipedia Kepler-90 wrote:The Kepler-90 system is the only eight-planet candidate system from Kepler, and the second to be discovered after the Solar System. It was also the only seven-planet candidate system from Kepler before the eighth was discovered in 2017, and one of two total seven-planet systems, along with TRAPPIST-1. Additionally, the inner six planets range in size from that of Earth to smaller than Neptune, and the outer two planets are the size of gas giants. All of the eight known planet candidates orbit within 1 AU from Kepler-90. A Hill stability test and an orbital integration of the system show that it is stable.

MarkBour wrote:As I look at the chart for the Kepler-90 system here, it strikes me as a truncated version of our own planetary set. And it makes sense that the observations from transit photometry will be biased, at least at first. It will more easily find large planets and short orbits. So, if Kepler-90 actually has a planetary system that has peak masses in the "middle distance", then we have not (yet) been able to observe the smaller effects of a set of outer planets that might taper off in mass. They would have much longer orbits and much smaller occultation effects, so would be harder to detect. Indeed, we have enough trouble detecting outer planets in our own system, let alone by looking for a glimmer in a star that is about 2545 light years away.

The radial velocity detection technique would be biased in about the same way as the star dimming technique.

Of course, this is very speculative, but it would be my personal guess that Kepler 90 probably has more than 8 planets.

FLPhotoCatcher wrote:It seems the only habitable place is likely to be on any moons around the outer two planets.

I notice the Kepler-90 planets are all labeled, but 'our' planets are not. I guess we can all remember our planets by the silly sentence, "My Very Enthusiastic Mother Just Served Us Noodles!" Kepler-90's planets? Hmmm...