How many planets in how little space?

[Moontanman]

I have been a big follower of the efforts of finding planets and something has been bothering me for a while. How many planets can orbit a star close together?

 

Our inner solar system is quite barren compared to many of the stars we have found planets around. A few contain several earth sized or larger planets within what would be in our solar system the orbit of mercury.

 

Would it be possible to have several earth sized planets around a sun like star within the orbit of Mars? If not why not?

[Acme]

I have been a big follower of the efforts of finding planets and something has been bothering me for a while. How many planets can orbit a star close together?

 

Our inner solar system is quite barren compared to many of the stars we have found planets around. A few contain several earth sized or larger planets within what would be in our solar system the orbit of mercury.

 

Would it be possible to have several earth sized planets around a sun like star within the orbit of Mars? If not why not?

It all depends on the specifics. A fewer or more planets with a little more-or-less mass that are a little more-or-less close to a star means the difference between stable orbits, collisions, or ejections from the system. I think it was a recent blog entry that had a link to a cool little game where you can place different mass objects in different orbits & then run it for 500 years to watch what happens. Here's a link to the game. Now go crash some planets! http://www.stefanom.org/super-planet-crash/: >>

Edited May 2, 2014 by Acme

[Greg H.]

Neat game. I was able to eject the earth in less than 100 years.

[MigL]

Since planets are detected by perturbations of their parent star, they would, by necessity, have to be very massive or very close to their star in order for the perturbations to be detectable. Until methods become more refined, the vast majority of found extra-solar planets will have these characteristics.

[Acme]

Since planets are detected by perturbations of their parent star, they would, by necessity, have to be very massive or very close to their star in order for the perturbations to be detectable. Until methods become more refined, the vast majority of found extra-solar planets will have these characteristics.

I believe they are achieving detections of 'small' planets by measuring dimming as planets pass in front of stars from our viewpoint. Give me a few minutes to find a link...

 

http://en.wikipedia.org/wiki/Methods_of_detecting_extrasolar_planets#Orbital_brightness_modulations

 

Orbital brightness modulations

 

Orbital brightness modulations observe the apparent brightness of a host star changing caused by the planet orbiting around it.

...

Multiple methods given in the full article.

 

A Mercury size planet has been detected by the Kepler telescope.

source: >> http://www.universetoday.com/100122/smallest-exoplanet-yet-discovered-by-listening-to-a-sun-like-star/

Scientists have discovered a new planet orbiting a Sun-like star, and the exoplanet is the smallest yet found in data from the Kepler mission. The planet, Kepler-37b, is smaller than Mercury, but slightly larger than Earth’s Moon. The planet’s discovery came from a collaboration between Kepler scientists and a consortium of international researchers who employ asteroseismology — measuring oscillations in the star’s brightness caused by continuous star-quakes, and turning those tiny variations in the star’s light into sounds.

 

“That’s basically listening to the star by measuring sound waves,” said Steve Kawaler, from Iowa State University in the US, and a member of the research team. “The bigger the star, the lower the frequency, or ‘pitch’ of its song.”

 

The measurements made by the astroseismologists allowed the Kepler research team to more accurately measure the tiny Kepler-37b, as well as revealing two other planets in the same planetary system: one slightly smaller than Earth and one twice as large. ...

PS Exoplanet Encyclopedia >> http://exoplanet.eu/

 

Exoplanet Archive >> http://exoplanetarchive.ipac.caltech.edu/

 

New Worlds Atlas >> http://planetquest.jpl.nasa.gov/newworldsatlas

Edited May 2, 2014 by Acme

[Moontanman]

Since planets are detected by perturbations of their parent star, they would, by necessity, have to be very massive or very close to their star in order for the perturbations to be detectable. Until methods become more refined, the vast majority of found extra-solar planets will have these characteristics.

 

I understand that part but it seems in some systems the planets are far more crowded than ours, so how many planets could fit in the habitable zone of the sun is what I am getting at.

 

The game is cool btw...

[MigL]

I've heard about the new methods also, so maybe in time the results won't be as skewed towards larger/closer planets.

 

As to how many planets can share close orbits, it seems to be extremely large for small asteroid as in between Mars and Jupiter in our own system. However I suspect as the asteroids become larger approaching planetoid size, tidal forces would rip them apart as they pass close to each other in their close orbits.

Someone better at orbital mechanics than me would have to give you an approximate answer as I don't think an exact answer is possible.

[Acme]

I understand that part but it seems in some systems the planets are far more crowded than ours, so how many planets could fit in the habitable zone of the sun is what I am getting at.

 

The game is cool btw...

I know you responded to MigL, but as he is mistaken and I put up the game I will take the liberty of replying to you.

 

So again, MigL is mistaken about detection in perturbations being the sole method of detection, as well as being mistaken about the size of the planet detectable. Please see my edited post. Quoting from one of my sources and in reference to your 'how many in habitable zone' question.

 

source: >> http://www.universetoday.com/100122/smallest-exoplanet-yet-discovered-by-listening-to-a-sun-like-star/

...We uncovered a planet smaller than any in our solar system orbiting one of the few stars that is both bright and quiet, where signal detection was possible, said Thomas Barclay, lead author of Nature paper. This discovery shows close-in planets can be smaller, as well as much larger, than planets orbiting our sun.

 

And are there more small planets like this out there, just waiting to be found?

 

As the team wrote in their paper, While a sample of only one planet is too small to use for determination of occurrence rates it does lend weight to the belief that planet occurrence increases exponentially with decreasing planet size".

That is the end of the article, so you would miss it if you don't read the full article. As to a habitable zone, this is also determined by how big the star is and so it is variable.

 

Also from one of my links -the exoplanet archive- there is an ongoing list of newest discoveries.

source: >> http://exoplanetarchive.ipac.caltech.edu/

April 17, 2014: Today the archive has 10 new planets, including Kepler-186 f, an Earth-radius planet located within the habitable zone of the host star, as featured in today's press release and the published paper. The other planets are: CoRoT-25 b, CoRoT-26 b, WASP-95 b, WASP-96 b, WASP-97 b, WASP-98 b, WASP-99 b, WASP-100 b and WASP-101 b.

That little blurb has numerous links which you can find by visiting the page.

 

Also again, the 'how many' question depends on the parent star's mass and the specific masses of planets in the habitable zone and their relative motions. As the game will demonstrate you can jam quite a few planets of varying sizes in the habitable zone and have them remain stable. Happy hunting!!

[Moontanman]

My best so far http://www.stefanom.org/spc/?view=

Cool game, if you speed it up and can better see how the planets are affecting each other, this is my best now with no less than 4 planets in the habitable zone! http://www.stefanom.org/spc/?view=8382393

[Janus]

Using a program called Gravity Simulator, I placed Earth mass planets between Venus and Mars at .1 AU increments (Leaving Venus, Earth and Mars where they are.)

 

I ran it at a high speed for 100,000 yrs simulator time. Here's a screen capture of the Orbits at that time.

 

 

The blue circle is Earth,the red is Mars, and the outer white is Venus (Mercury is the inner white circle).

 

The interesting thing is that 100,000 years is not long, yet there was a great amount of orbital shifts. ( at this point Earth has moved out to 1.33 AU with an eccentricity of 0.1. ) Several planets now have crossing orbits, and while none have yet collided or been ejected, This rapid shift in orbits cannot bode well for livability.

[Moontanman]

I'll come clean here, I am working out a story about a system that has three stars, two g type orbiting within 5 million miles of each other with a m star orbiting those two at about 20 million miles, it should result in a very wide habitable zone, I'd like to put 3 to 5 more or less earth sized planets in that zone.

 

The main question is of course is would that habitable zone be stable enough to allow planets with three stars in the center of the system...

[Janus]

I'll come clean here, I am working out a story about a system that has three stars, two g type orbiting within 5 million miles of each other with a m star orbiting those two at about 20 million miles, it should result in a very wide habitable zone, I'd like to put 3 to 5 more or less earth sized planets in that zone.

 

The main question is of course is would that habitable zone be stable enough to allow planets with three stars in the center of the system...

I tried putting together a system like you describe in gravity simulator and it keeps falling apart fairly rapidly even with just three planets. The two G stars orbiting each other impart a considerable "wiggle" to the orbits of the planets, which combined with the slighter wiggle introduced by the M star and the perturbation from the other planets ends up blowing things up in short order.

[MigL]

You write sci-fi Moontanman ?

Amateur or professionally ?

And if professionally, anything we might have read?

[Moontanman]

I tried putting together a system like you describe in gravity simulator and it keeps falling apart fairly rapidly even with just three planets. The two G stars orbiting each other impart a considerable "wiggle" to the orbits of the planets, which combined with the slighter wiggle introduced by the M star and the perturbation from the other planets ends up blowing things up in short order.

 

 

Oh well, it's fiction, I always try to be reasonable accurate. Janus, can that sort of system be tweaked to allow the habitable zone to be stable? The idea of a very wide habitable zone around along lived star makes me break out in creative bumps... I know it has been reported in science literature lately that a multiple star systems have been found with planets and it was reported that if the stars orbited very close it wouldn't make planetary orbits unstable. I think they were double stars not triple but triple system with a red star appeals to me for some reason... So many hooks to hang a story on, flairs from the red star, multiple planets hmmmm.

 

You write sci-fi Moontanman ?

Amateur or professionally ?

And if professionally, anything we might have read?

 

 

No, just amateur but one of my stories is going to be animated by a professional animator...

You guys might find this interesting.

 

http://www.johnbray.org.uk/planetdesigner/

Edited May 3, 2014 by Moontanman

[Enthalpy]

Several Earth-sized planets within Mars' orbit is possible: Venus and Earth proove it.

 

About software, be very cautious: instability uses to result from the software rather than from celestial mechanics.

[Airbrush]

Would it be possible to have several earth sized planets around a sun like star within the orbit of Mars? If not why not?

 

Our solar system has most planets in nearly circular orbits. This regularity is unusual. After 4.5 Billion years our solar system seems very stable. So I think it would be unusual to find a sun-sized star with more planets within the orbit of Mars.

 

Red Dwarf stars are the vast majority of stars, so I think finding habitable planets should focus on Red Dwarfs primarily.

 

Even though Kepler is not working now, it has accumulated so much data that they will be reporting new planets for years from what Kepler already made available to us.