First Results from Kepler

[Netheralian]

Science again at its best.

Some early results from Kepler (sorry - its the only "official" link I can find at the moment with papers being released this month - i think) with 306 candidate planets and 400 more potentials already found in 43 days worth of data.

http://scienceblogs.com/startswitha...e.php?utm_source=readerspicks&utm_medium=link

If we assume that each one is a planet, that brings us to 706 planets around 100,000 stars. Since our galaxy has around 200 billion stars, we can figure out that there ought to be -- wait for it -- at least 1.4 billion planets in our galaxy!

Apparently up to 50% could be false positives, but if we consider the probability of a planet passing between our line of sight of a star (~0.5% for earth like planet at 1AU from a similar Sol like star) then there is likely to be a crap load of planets out there.

 

[SagansHeroes]

How does this account for planets that aren't big enough/close enough to the star to give a detectable "tug" in due to their common centre of gravity they rotate around, and how does it account for solar systems that are not side on to us? Like the planet does not pass between us and it's star?

Don't get me wrong, I'm as excited by the Kepler results as anyone, but I think it's PRETTY premature to be multiplying current ones with known stars and giving an estimate to how many stars there are...

 

[)O( Hytegia )O(]

How does this account for planets that aren't big enough/close enough to the star to give a detectable "tug" in due to their common centre of gravity they rotate around, and how does it account for solar systems that are not side on to us? Like the planet does not pass between us and it's star?

Don't get me wrong, I'm as excited by the Kepler results as anyone, but I think it's PRETTY premature to be multiplying current ones with known stars and giving an estimate to how many stars there are...

Buzzkill. xD

 

[Unwardil]

Honestly, I think the number can only go up. Seeing as they only call it a planet when they're absolutely certain that it has to be, I find it highly probable that there will turn out to be, on average, more planets than stars in the universe.

 

[ExplorerAtHeart]

How does this account for planets that aren't big enough/close enough to the star to give a detectable "tug" in due to their common centre of gravity they rotate around, and how does it account for solar systems that are not side on to us? Like the planet does not pass between us and it's star?

It doesn't. Those will have to wait to be detected by other means. There are trillions on top of trillions of planets in this galaxy alone =D All sorts of stuff wait to be discovered!

 

[SagansHeroes]

How does this account for planets that aren't big enough/close enough to the star to give a detectable "tug" in due to their common centre of gravity they rotate around, and how does it account for solar systems that are not side on to us? Like the planet does not pass between us and it's star?

Don't get me wrong, I'm as excited by the Kepler results as anyone, but I think it's PRETTY premature to be multiplying current ones with known stars and giving an estimate to how many stars there are...

Buzzkill. xD

I think it's the opposite of a buzzkill. It basically means that there should be many MORE planets. The math from the guy at that website is using what we have currently found as the basis for his "total number of planets in the galaxy", when in reality our mechanisms for finding/confirming planets are still in their infancy

It doesn't. Those will have to wait to be detected by other means. There are trillions on top of trillions of planets in this galaxy alone =D All sorts of stuff wait to be discovered!

Honestly, I think the number can only go up. Seeing as they only call it a planet when they're absolutely certain that it has to be, I find it highly probable that there will turn out to be, on average, more planets than stars in the universe

.

My point was exactly what Unwardil and ExploreratHeart said. Some of the first planets we found around a pulsar, where we were sure there would be none (pulsar = super nova remnant) and there were THREE planets around that. There shouldn't have been any, let alone one, or even multiple. I suspect there will be many many times the number of planets compared to stars.

 

[Nelson]

Don't get me wrong, I'm as excited by the Kepler results as anyone, but I think it's PRETTY premature to be multiplying current ones with known stars and giving an estimate to how many stars there are...

Yes, any of these numbers will likely be lower limits on the actual numbers that are out there. Kepler is also limited in what it can detect based on the distance of the planet from the host star and the mass of the planet. This graphic from the NASA website illustrates this detection range:

Original link: http://kepler.nasa.gov/Science/RelatedScience/capabilitiesOfVariousPlanetDetectionMethods/

The x-axis shows distance in Astronomical Units (distance between the Earth and the Sun), while the y-axis shows the mass of the planet in Earth masses. The legend shows the detection ranges of various methods that are discussed on the original page, as well as currently detected planets, and where the planets in our solar system would fall on the plot.

On top of this, planets will only be detected if the orbit happens to fall along our line of sight. The probability of which was correctly given by the original poster as 0.5% (assuming a random distribution of inclination angles). The rate of planets at different locations in the galaxy is likely also important (bulge, disk, halo). I don't think it is so obvious that this rate should be constant everywhere.

I guess my point is: there are many things that need to be understood before someone tries to come up with a reasonable estimate for the number of planets in the galaxy.

 

[AllMakesCombined]

*finally marks another value in the Drake equation*

 

[SagansHeroes]

*finally marks another value in the Drake equation*

We are far from getting an accurate representation of planets per star. You could probably put the currently proposed number in, I think they put about 1 billion in the initial equation anyway, but I can guarantee as our methods get better that number will rise. It would/should work out to be that planets > stars imo. I mean, we have 8 planets in our system (not including the dwarf planets 4-5 or so), some pulsar has 3.... Of others we've found, there are some with 2-4 around their stars. All it takes is 1/3rd -1/2 the stars to have planets and the ones with more than one planet will push planet population over star population.