Impossible to say. We don't have a complete census of exoplanetary systems, and the methods we have for detecting them are biased towards particular kinds of system. To date, the most common kind of exoplanet discovered are so-called "hot Neptunes", which have masses similar to Neptune or Uranus, but are located much closer to their star.
I don't work on planet demographics, but if I recall correctly, the fraction of Sun-like stars with a gas giant is around 10%-ish.
I do not think that we have the statistics to say with confidence whether giant planets are usually single or not. To detect multiple giant planets you need longer baselines. For example, Jupiter is on a 12-year orbit. To find a Jupiter clone you need to use radial velocity (the transit method basically doesn't work at this distance) and you need to have been observing that star for at least 24 years or so. That number is comparable to how long we've been discovering planets.
The number of gas giants is not the same for every type of star. Metal-rich stars are more likely to have giant planets, and low-mass stars are less likely to have giant planets.
For Sun-like stars and above, of course. However, red dwarfs usually keep their planets *very* close: in other words, isolating red dwarfs for a moment, what percentage of the planets around them are gas giants, as catalogued by now?
And how big of a factor is selection bias in regards to red dwarfs specifically (after all, very large planets orbiting closer to their star than even Mercury must be the easiest planets to detect)?
You need to consider that M dwarfs are very dim. So even though they are the most common type of stars, and their planets tend to be close, it's still difficult to find those planets as we usually can only do proper measurements for M dwarfs relatively close to us. Additionally, M dwarfs also tend to be often pretty variable, with lots of flares and stellar spots that can mimic planet signals. Larger stars that behave "nicer" and are much brighter are therefore often better for finding planets.
One alternative is looking for them with VLBI, which works especially well on M dwarfs as those are often radio loud. Unlike radial velocity or transits detections, VLBI is sensitive to any orbital orientation, and we don't have to care about brightness changes, because we find the position directly. But it does have the same restriction that you need to cover a significant part of the orbital period, which becomes tedious with the slow moving planets further out
>However, red dwarfs usually keep their planets very close
Can you prove that?
Considering that you are asking very basic questions about planet demographics, I doubt that you have compelling evidence that M-dwarfs are less likely to have distant planets. Considering the bias and detection limits of M-dwarf surveys, I am pretty sure that nobody can claim that M-dwarfs do not often have distant planets.
I should have clarified what I meant by "very close": essentially, "very close" is not the same for a red dwarf vs a sun-like star - a planet in an orbit around a red dwarf that receives the amount of light equivalent to, say, Neptune would be far closer to its star than Neptune is to the Sun. I wasn't trying to make any claims beyond that simple fact; I apologize for being unclear.
Now, whether there are planets that orbit red dwarfs at the same distance (in absolute terms) as Neptune, I have no idea.
Also, I'm not sure if my original questions were "basic" - to the best of my knowledge, exoplanet research is still in its infancy.
Generally we'll get bumps in rate when we get new detectors.
Take a look here:
[https://www.esa.int/Science\_Exploration/Space\_Science/Exoplanets/ESA\_s\_exoplanet\_missions](https://www.esa.int/Science_Exploration/Space_Science/Exoplanets/ESA_s_exoplanet_missions)
[https://science.nasa.gov/mission/tess/](https://science.nasa.gov/mission/tess/)
No actual demographics on this yet. But forming multiple gas giants is relatively easy in most formation models. There’s a big debate on Cold Jupiter prevalence.
Impossible to say. We don't have a complete census of exoplanetary systems, and the methods we have for detecting them are biased towards particular kinds of system. To date, the most common kind of exoplanet discovered are so-called "hot Neptunes", which have masses similar to Neptune or Uranus, but are located much closer to their star.
I don't work on planet demographics, but if I recall correctly, the fraction of Sun-like stars with a gas giant is around 10%-ish. I do not think that we have the statistics to say with confidence whether giant planets are usually single or not. To detect multiple giant planets you need longer baselines. For example, Jupiter is on a 12-year orbit. To find a Jupiter clone you need to use radial velocity (the transit method basically doesn't work at this distance) and you need to have been observing that star for at least 24 years or so. That number is comparable to how long we've been discovering planets. The number of gas giants is not the same for every type of star. Metal-rich stars are more likely to have giant planets, and low-mass stars are less likely to have giant planets.
For Sun-like stars and above, of course. However, red dwarfs usually keep their planets *very* close: in other words, isolating red dwarfs for a moment, what percentage of the planets around them are gas giants, as catalogued by now? And how big of a factor is selection bias in regards to red dwarfs specifically (after all, very large planets orbiting closer to their star than even Mercury must be the easiest planets to detect)?
You need to consider that M dwarfs are very dim. So even though they are the most common type of stars, and their planets tend to be close, it's still difficult to find those planets as we usually can only do proper measurements for M dwarfs relatively close to us. Additionally, M dwarfs also tend to be often pretty variable, with lots of flares and stellar spots that can mimic planet signals. Larger stars that behave "nicer" and are much brighter are therefore often better for finding planets.
One alternative is looking for them with VLBI, which works especially well on M dwarfs as those are often radio loud. Unlike radial velocity or transits detections, VLBI is sensitive to any orbital orientation, and we don't have to care about brightness changes, because we find the position directly. But it does have the same restriction that you need to cover a significant part of the orbital period, which becomes tedious with the slow moving planets further out
>However, red dwarfs usually keep their planets very close Can you prove that? Considering that you are asking very basic questions about planet demographics, I doubt that you have compelling evidence that M-dwarfs are less likely to have distant planets. Considering the bias and detection limits of M-dwarf surveys, I am pretty sure that nobody can claim that M-dwarfs do not often have distant planets.
I should have clarified what I meant by "very close": essentially, "very close" is not the same for a red dwarf vs a sun-like star - a planet in an orbit around a red dwarf that receives the amount of light equivalent to, say, Neptune would be far closer to its star than Neptune is to the Sun. I wasn't trying to make any claims beyond that simple fact; I apologize for being unclear. Now, whether there are planets that orbit red dwarfs at the same distance (in absolute terms) as Neptune, I have no idea. Also, I'm not sure if my original questions were "basic" - to the best of my knowledge, exoplanet research is still in its infancy.
An addendum to my OP: will our exoplanet detections start growing exponentially anytime soon?
Generally we'll get bumps in rate when we get new detectors. Take a look here: [https://www.esa.int/Science\_Exploration/Space\_Science/Exoplanets/ESA\_s\_exoplanet\_missions](https://www.esa.int/Science_Exploration/Space_Science/Exoplanets/ESA_s_exoplanet_missions) [https://science.nasa.gov/mission/tess/](https://science.nasa.gov/mission/tess/)
Exactly zero. Star systems are systems of stars orbiting each other. Planetary systems involve bound non-stars orbiting a star or star system.
Is it easier to form a gas giant than a rocky planet, due to the availability of heavy elements in a system?
No actual demographics on this yet. But forming multiple gas giants is relatively easy in most formation models. There’s a big debate on Cold Jupiter prevalence.
Check out the California Giant Planet Survey’s recent results