9 ms·

Our Galaxy Has at Least 100 Billion Planets, Study Shows

96 points by jfoucher 15y ago

julian37 15y ago
This is very exciting. On a related note, the number put forth by the study (at least one planet per star, on average) is roughly consistent with Drake's 1961 estimate that half of all stars will have planets, and stars with planets will have 2 planets capable of developing life. Except, of course, that Drake estimated an average of >=1 habitable planets per star. Still, it's good to see one of his estimates being corroborated. http://en.wikipedia.org/wiki/Drake_equation http://en.wikipedia.org/wiki/Drake_equation
- microarchitect 15y ago
  Drake just pulled a bunch of numbers out of a hat and multiplied them. This is a much more serious scholarly effort.
  - demallien 15y ago
    Drake did no such thing. The Drake equation was not designed to give us an answer as to the number of civilisations out there, but to show us which questions needed to be answered to help us identify candidate search locations. As an example, the Kepler mission is a direct result of the Drake equation, designed to resolve the first two parameters - fp and ne.
bitops 15y ago
Eric Idle already told us that quite a long time ago.
- arethuza 15y ago
  http://www.youtube.com/watch?v=buqtdpuZxvk http://www.youtube.com/watch?v=buqtdpuZxvk
- brudgers 15y ago
  ...and also that there is an infinity of worlds Giordano Bruno beat him to the punch by four centuries (if of course one accepts 100,000,000,000 as a reasonable approximation of infinity). http://www.positiveatheism.org/hist/brunoiuw0.htm#IUWTOC http://www.positiveatheism.org/hist/brunoiuw0.htm#IUWTOC
- huxley 15y ago
  The "Galaxy Song" only specifies that there are a 100 billion stars :-) For some serious geeky pedantry, it's hard to beat the Wikipedia entry for the song (especially the section entitled "Accuracy of figures quoted in the lyrics"): http://en.wikipedia.org/wiki/Galaxy_Song#Accuracy_of_figures_quoted_in_the_lyrics http://en.wikipedia.org/wiki/Galaxy_Song#Accuracy_of_figures...
pessimist 15y ago
Hmm, "Our Milky Way galaxy contains a minimum of 100 billion planets according to a detailed statistical study based on the detection of three extrasolar planets by an observational technique called microlensing." So we looked in 3 places, found 3 planets and are extrapolating to 100 billion? Surely I would wait for a few more examples? Edit: Reading the full story, "Of the approximately 40 microlensing events closely monitored, three showed evidence for exoplanets. Using a statistical analysis, the team found that one in six stars hosts a Jupiter-mass planet. What's more, half of the stars have Neptune-mass planets, and two-thirds of the stars have Earth-mass planets. Therefore, low-mass planets are more abundant than their massive counterparts." I dont get it. Any explanation?
- mturmon 15y ago
  The reason it's OK to extrapolate in this way would appear to be in this fact (from TFA): "Unlike other prominent planet-detection techniques, which measure the shadows of planets passing in front of their stars (transit) or measure the wobble of a star due to the gravitational tug of a planet (radial velocity and astrometry), the gravitational-lensing technique is unbiased in the selection of the host star." To know more, we have to read the story in Nature, which is here: http://www.nature.com/nature/journal/v481/n7380/full/nature10684.html http://www.nature.com/nature/journal/v481/n7380/full/nature1... Look at the error bars on their percentages. Super-earths (planets of 5-10x earth mass) are present on "62 +35 -37"% of systems. So, your intuition that the extrapolation was shaky is correct.
  - Retric 15y ago
    Assuming the title and your numbers are correct they basically said. 'We estimate that there is a 95% chance that there are 250Billion stars +/- 60% which means there is a 97.5% chance that there are at least 100billion planets.' However, the actual study costs US$32 so I am not buying it so somewhere in the game of telephone that we just played information could have mutated.
    - mchouza 15y ago
      The paper can be found here: http://www.eso.org/public/archives/releases/sciencepapers/eso1204/eso1204.pdf http://www.eso.org/public/archives/releases/sciencepapers/es...
rokhayakebe 15y ago
I cannot even start to grasp the meaning of 100B planets. I read that if the "Milky Way" was the size of China, then the the sun and 6 closest planets around together would be the size of one quarter.
- InclinedPlane 15y ago
  I just did the math on that, it's about right. It's closer to a dime though.
  - thret 15y ago
    If you really did the math, I love you.
    - InclinedPlane 15y ago
      It's straightforward math, the hardest part is coming up with a width for China (I ended up using an approximation of 5,000 km), all of the other figures are on wikipedia (radius of Saturn's orbit, size of the milky way). Also, if you want to be super lazy you can get google to convert units for you: https://www.google.com/search?ie=UTF-8&q=2.87+billion+km+%2F+100%2C000+ly+*+5%2C000+km#sclient=psy-ab&hl=en&source=hp&q=2.87+billion+km+%2F+100%2C000+light+years+*+5%2C000+km&pbx=1&oq=2.87+billion+km+%2F+100%2C000+light+years+*+5%2C000+km&aq=f&aqi=&aql=&gs_sm=e https://www.google.com/search?ie=UTF-8&q=2.87+billion+km...
cvg 15y ago
that's about one for every person that's ever lived.
- karamazov 15y ago
  very appropriate 2001 reference.
JeffL 15y ago
Sounds a little more lonely when you read "it's likely there are a minimum of 1,500 planets within just 50 light-years of Earth." 1,500 isn't that many, and 50 light-years is a really long distance.
- michaelcampbell 15y ago
  > 50 light-years is a really long distance. Compared to what we can wrap our brains around generally, sure, but in the scheme of the universe, not so much.
  - meepmorp 15y ago
    What about in comparison to a distance we'd be likely to reach before we annihilate ourselves?
    - alexkcd 15y ago
      I keep hearing this argument. But physically traveling there is pretty stupid if you think about it. It's much simpler to set up a communication channel. Sure it'll have a 50 year latency, but we could easily stream all of youtube (or the entire internet really) to them, and so could they. Assuming they're more advanced and their cameras capture the environment in spherical 3D, we could recreate what it's like to stand on their soil pretty accurately from home. Besides just browsing their extranet would be amazing in itself.
      - sien 15y ago
        So we discover another civilization and send them 4chan? Mind you, seeing another species' civilization's sense of humor would be pretty amazing.
      - dolbz 15y ago
        > Sure it'll have a 50 year latency, but we could easily stream all of youtube (or the entire internet really) to them Well Eric Schmidt who's probably in a better position to estimate than most, said that Google estimates the internet is made up of 5 million terabytes. 5 million terabytes / 10gbps = 126.8 years and I very much doubt 10gbps is even remotely achievable over interstellar distances. I don't what kind of data rates are achievable but I would expect it to be extremely slow relative to Gigabit speeds.
shaggyfrog 15y ago
The headline reads even better if you imagine Carl Sagan saying "billion".
rbanffy 15y ago
So, where are the other kids? We want to play.
johnnyg 15y ago
Now all we need to do is get each of them to send us $150. US debt crisis solved.
- eru 15y ago
  Where should they take the money from? You print all the dollars. Unless there's been trade with aliens, they won't have any earthling money.
Joakal 15y ago
I believe there are much more planets because not every planet has a star: http://www.dailygalaxy.com/my_weblog/2011/09/billions-of-dark-planets-roam-the-milky-way.html http://www.dailygalaxy.com/my_weblog/2011/09/billions-of-dar...
ifearthenight 15y ago
Now I feel a bit of a loser for only having visited one so far.

96 points by jfoucher 15y ago

This is very exciting. On a related note, the number put forth by the study (at least one planet per star, on average) is roughly consistent with Drake's 1961 estimate that half of all stars will have planets, and stars with planets will have 2 planets capable of developing life. Except, of course, that Drake estimated an average of >=1 habitable planets per star. Still, it's good to see one of his estimates being corroborated. http://en.wikipedia.org/wiki/Drake_equation http://en.wikipedia.org/wiki/Drake_equation

microarchitect 15y ago
Drake just pulled a bunch of numbers out of a hat and multiplied them. This is a much more serious scholarly effort.
- demallien 15y ago
  Drake did no such thing. The Drake equation was not designed to give us an answer as to the number of civilisations out there, but to show us which questions needed to be answered to help us identify candidate search locations. As an example, the Kepler mission is a direct result of the Drake equation, designed to resolve the first two parameters - fp and ne.

bitops 15y ago

Eric Idle already told us that quite a long time ago.

arethuza 15y ago
http://www.youtube.com/watch?v=buqtdpuZxvk http://www.youtube.com/watch?v=buqtdpuZxvk
brudgers 15y ago
...and also that there is an infinity of worlds Giordano Bruno beat him to the punch by four centuries (if of course one accepts 100,000,000,000 as a reasonable approximation of infinity). http://www.positiveatheism.org/hist/brunoiuw0.htm#IUWTOC http://www.positiveatheism.org/hist/brunoiuw0.htm#IUWTOC
huxley 15y ago
The "Galaxy Song" only specifies that there are a 100 billion stars :-) For some serious geeky pedantry, it's hard to beat the Wikipedia entry for the song (especially the section entitled "Accuracy of figures quoted in the lyrics"): http://en.wikipedia.org/wiki/Galaxy_Song#Accuracy_of_figures_quoted_in_the_lyrics http://en.wikipedia.org/wiki/Galaxy_Song#Accuracy_of_figures...

pessimist 15y ago

Hmm, "Our Milky Way galaxy contains a minimum of 100 billion planets according to a detailed statistical study based on the detection of three extrasolar planets by an observational technique called microlensing." So we looked in 3 places, found 3 planets and are extrapolating to 100 billion? Surely I would wait for a few more examples? Edit: Reading the full story, "Of the approximately 40 microlensing events closely monitored, three showed evidence for exoplanets. Using a statistical analysis, the team found that one in six stars hosts a Jupiter-mass planet. What's more, half of the stars have Neptune-mass planets, and two-thirds of the stars have Earth-mass planets. Therefore, low-mass planets are more abundant than their massive counterparts." I dont get it. Any explanation?

mturmon 15y ago
The reason it's OK to extrapolate in this way would appear to be in this fact (from TFA): "Unlike other prominent planet-detection techniques, which measure the shadows of planets passing in front of their stars (transit) or measure the wobble of a star due to the gravitational tug of a planet (radial velocity and astrometry), the gravitational-lensing technique is unbiased in the selection of the host star." To know more, we have to read the story in Nature, which is here: http://www.nature.com/nature/journal/v481/n7380/full/nature10684.html http://www.nature.com/nature/journal/v481/n7380/full/nature1... Look at the error bars on their percentages. Super-earths (planets of 5-10x earth mass) are present on "62 +35 -37"% of systems. So, your intuition that the extrapolation was shaky is correct.
- Retric 15y ago
  Assuming the title and your numbers are correct they basically said. 'We estimate that there is a 95% chance that there are 250Billion stars +/- 60% which means there is a 97.5% chance that there are at least 100billion planets.' However, the actual study costs US$32 so I am not buying it so somewhere in the game of telephone that we just played information could have mutated.
  - mchouza 15y ago
    The paper can be found here: http://www.eso.org/public/archives/releases/sciencepapers/eso1204/eso1204.pdf http://www.eso.org/public/archives/releases/sciencepapers/es...

rokhayakebe 15y ago

I cannot even start to grasp the meaning of 100B planets. I read that if the "Milky Way" was the size of China, then the the sun and 6 closest planets around together would be the size of one quarter.

InclinedPlane 15y ago
I just did the math on that, it's about right. It's closer to a dime though.
- thret 15y ago
  If you really did the math, I love you.
  - InclinedPlane 15y ago
    It's straightforward math, the hardest part is coming up with a width for China (I ended up using an approximation of 5,000 km), all of the other figures are on wikipedia (radius of Saturn's orbit, size of the milky way). Also, if you want to be super lazy you can get google to convert units for you: https://www.google.com/search?ie=UTF-8&q=2.87+billion+km+%2F+100%2C000+ly+*+5%2C000+km#sclient=psy-ab&hl=en&source=hp&q=2.87+billion+km+%2F+100%2C000+light+years+*+5%2C000+km&pbx=1&oq=2.87+billion+km+%2F+100%2C000+light+years+*+5%2C000+km&aq=f&aqi=&aql=&gs_sm=e https://www.google.com/search?ie=UTF-8&q=2.87+billion+km...

cvg 15y ago

that's about one for every person that's ever lived.

karamazov 15y ago
very appropriate 2001 reference.

JeffL 15y ago

Sounds a little more lonely when you read "it's likely there are a minimum of 1,500 planets within just 50 light-years of Earth." 1,500 isn't that many, and 50 light-years is a really long distance.

michaelcampbell 15y ago
> 50 light-years is a really long distance. Compared to what we can wrap our brains around generally, sure, but in the scheme of the universe, not so much.
- meepmorp 15y ago
  What about in comparison to a distance we'd be likely to reach before we annihilate ourselves?
  - alexkcd 15y ago
    I keep hearing this argument. But physically traveling there is pretty stupid if you think about it. It's much simpler to set up a communication channel. Sure it'll have a 50 year latency, but we could easily stream all of youtube (or the entire internet really) to them, and so could they. Assuming they're more advanced and their cameras capture the environment in spherical 3D, we could recreate what it's like to stand on their soil pretty accurately from home. Besides just browsing their extranet would be amazing in itself.
    - sien 15y ago
      So we discover another civilization and send them 4chan? Mind you, seeing another species' civilization's sense of humor would be pretty amazing.
    - dolbz 15y ago
      > Sure it'll have a 50 year latency, but we could easily stream all of youtube (or the entire internet really) to them Well Eric Schmidt who's probably in a better position to estimate than most, said that Google estimates the internet is made up of 5 million terabytes. 5 million terabytes / 10gbps = 126.8 years and I very much doubt 10gbps is even remotely achievable over interstellar distances. I don't what kind of data rates are achievable but I would expect it to be extremely slow relative to Gigabit speeds.

shaggyfrog 15y ago

The headline reads even better if you imagine Carl Sagan saying "billion".

rbanffy 15y ago

So, where are the other kids? We want to play.

johnnyg 15y ago

Now all we need to do is get each of them to send us $150. US debt crisis solved.

eru 15y ago
Where should they take the money from? You print all the dollars. Unless there's been trade with aliens, they won't have any earthling money.

Joakal 15y ago

I believe there are much more planets because not every planet has a star: http://www.dailygalaxy.com/my_weblog/2011/09/billions-of-dark-planets-roam-the-milky-way.html http://www.dailygalaxy.com/my_weblog/2011/09/billions-of-dar...

ifearthenight 15y ago

Now I feel a bit of a loser for only having visited one so far.