Starship Asterisk*

Kepler's Suns and Planets

Explanation: Using the prolific planet hunting Kepler spacecraft, astronomers have discovered 1,235 candidate planets orbiting other suns since the Kepler mission's search for Earth-like worlds began in 2009. To find them, Kepler monitors a rich star field to identify planetary transits by the slight dimming of starlight caused by a planet crossing the face of its parent star. In this remarkable illustration, all of Kepler's planet candidates are shown in transit with their parent stars ordered by size from top left to bottom right. Stars and the silhouettes of transiting planets are all shown at the same relative scale, with saturated star colors. Of course, some stars show more than one planet in transit, but you may have to examine the picture at high resolution to spot them all. For reference, the Sun is shown at the same scale, by itself below the top row on the right. In silhouette against the Sun's disk, both Jupiter and Earth are in transit.

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I fear this image is going to generate a lot of confusion. It is easy to come away thinking that these are stellar images produced by Kepler. In reality, Kepler is unable to resolve any stars, and simply produces a curve of intensity versus time for each of its targets. This image was synthesized based on the known stellar characteristics and the measured transit characteristics of each target.

I like it. In particular, I like the size of the stars and their colors. It makes it easier to assess what kind of stars are likely to have planets. Of course, since small red (really yellow-orange) stars are by far the most numerous, it makes sense that Kepler should spot a particularly large number of planets transiting red dwarfs.

An interesting trend is that A-type stars seem to be good at making giant planets. Prominent A-type stars like Fomalhaut and Beta Pictoris have had their giant planets directly imaged by telescopes. Famous star Vega is surrounded by a large dusty disk. This makes me wonder if the small number of blue stars here are A-type stars.

Ann

Chris Peterson wrote:I fear this image is going to generate a lot of confusion. It is easy to come away thinking that these are stellar images produced by Kepler. In reality, Kepler is unable to resolve any stars, and simply produces a curve of intensity versus time for each of its targets. This image was synthesized based on the known stellar characteristics and the measured transit characteristics of each target.

Chris, thanks for starting the thread with a bit of clarity. Otherwise, I would've been one of the confused, thinking that those were indeed images of distant planets transitting suns.
Very interesting image, though.


And even in the high-res image, Earth is just about impossible to spot!

Looks like a collection of duck eggs.

What a wonderful visulization!

I noticed that there aren't a lot of blue stars in the mix... Is this likely because blue stars are in general younger, and the planets haven't formed yet?

-Noel

It's amazing however they do it. Thanks Jason Rowe and the Kepler crew.

Wow! I guess I'm behind in the count. Didn't realize we were over 1000 planets!

NoelC wrote:I noticed that there aren't a lot of blue stars in the mix... Is this likely because blue stars are in general younger, and the planets haven't formed yet?

I think the evidence generally supports the idea that planetary systems form very early. Most likely, any star that produces planets will have them in place once the dust has cleared.

Of course, we don't really understand the details of how planets form, or what kind of stars are most likely to have them. But I think Ann hits closest to the truth in this case: it's a simple matter of statistics. Blue stars make up less than 1% of the stellar population; yellow and orange stars make up more than 90%. So the latter make up most of the Kepler data set.

In College, back in 72-74, in a Science class, I did a presentation, or paper, (I forget which now), on how many planets could reasonably support life in the Galaxy. Even at something like .1% that is like 200,000,000 planets. At 200 billion stars. Even .001% is 2 million. I also thought back then that every system would have planets of some sort, of course not all would support life, and not all that once did support life, would still support it. Looks like I was ahead of my time...I don't think anybody believed me though, of course....oh yeah, I am just an unrealistic DREAMER!!!!

Well, we seem to be finding planets left and right now!!!

So they can CHOKE ON IT!!!! Who's laughing now???????

Oh, sorry, it's time for my medication.....

This is an amazing visualization. This is the kind of stuff I love to see. A tremendous amount of data is presented here in one quick view. I doubt it will create any more confusion than any other scientific presentation.

ddorn wrote:Wow! I guess I'm behind in the count. Didn't realize we were over 1000 planets!

Kepler's confirmed count is 15! http://www.kepler.arc.nasa.gov/Mission/discoveries/
I believe that the total count is somewhere in the 400 to 500 range! http://www.planetary.org/exoplanets/list.php
The 1225 are candidates!

orin stepanek wrote:... The 1225 are candidates!

Being in the early stages of an election here, I can affirm that all candidates think they're already elected.

But to a serious question: I assume Kepler has had a limited view so far of the cosmos. Can we say yet if the suns shown in this illustration -- in their number, size and colour -- are proportionally representative of the stellar population of the Milky Way? That would make it even more informative as a graphic.

Rob

As much as I love blue stars, I'm fascinated by the largest star here, and even more by its planet. The big star is a red giant, probably a modest one as red giants go. According to Professor Emeritus Jim Kaler the diameter of modest red giant Pollux is about 10 times solar, and the diameter of the biggest of the Kepler stars here appears to be less than that, or at least it looks like that to me.

All right, but now look at that star's planet! What a biggie! Compare it with the tiny dot of Jupiter that is seen transiting the Sun in today's APOD. Why is that planet so very big?

Rob wrote:

But to a serious question: I assume Kepler has had a limited view so far of the cosmos. Can we say yet if the suns shown in this illustration -- in their number, size and colour -- are proportionally representative of the stellar population of the Milky Way? That would make it even more informative as a graphic.

My guess is that it is fairly representative, but not perfectly representative. If anything, the small red dwarfs ought to have been even more numerous, and stars that are larger and brighter than the Sun should have been proportionally fewer. According to Ken Croswell's Planet Quest, red dwarfs make up 80% of all stars in our galaxy, K dwarfs make up 9%, white dwarfs make up 5%, G-type main sequence stars like the Sun make up 4%, and all other stars put together make up 2% of the stellar population of our galaxy. Judging from the size and color of the Kepler stars, it is quite possible that about 200 out of 1,235 would be brighter than the Sun, so about 16% of these stars may well be brighter than the Sun. I don't think that is really representative.

Ann

Boomer12k wrote:In College, back in 72-74, in a Science class, I did a presentation, or paper, (I forget which now), on how many planets could reasonably support life in the Galaxy. Even at something like .1% that is like 200,000,000 planets. At 200 billion stars. Even .001% is 2 million. I also thought back then that every system would have planets of some sort, of course not all would support life, and not all that once did support life, would still support it. Looks like I was ahead of my time...I don't think anybody believed me though, of course....oh yeah, I am just an unrealistic DREAMER!!!!

Well, we seem to be finding planets left and right now!!!

So they can CHOKE ON IT!!!! Who's laughing now???????

Oh, sorry, it's time for my medication.....

Just what kind of medication are you taking It may be beneficial to many people

Ann wrote: What a biggie!

NOW there's scientific speak that i can understand Atta Girl, Ann!!

Guest wrote:This is an amazing visualization. This is the kind of stuff I love to see. A tremendous amount of data is presented here in one quick view. I doubt it will create any more confusion than any other scientific presentation.

Please don't take my earlier comment as a criticism- I agree that the presentation of data here is superb, and I'm very much a fan of clever and efficient graphics like this.

To people who have a reasonable understanding of Kepler and how it works, there is nothing confusing. And if you read the APOD caption very carefully, you can probably figure out that this graphic isn't made from a bunch of photographs. But I still think that a lot of more casual viewers of APOD could easily misunderstand the image- which is why I made my earlier comments.

Well, this seems to confirm just how ‘average’ our star and our corner of the universe is. The size and color shown (assuming they are reasonably relative) for the Sun is just about in the middle of this collection of colossal gas bags.

How many other star systems were viewed at an angle whereby the planets would not cause any dimming, and thus be missed by Keppler? That should be considered when estimating the possible habitable systems.

Perhaps somebody can help...

The graphic portrays the smallest stars on the bottom-right to be smaller in diameter than the largest planet orbiting the largest star in the top-left. This seems to contradict the idea that any planet with a mass larger than Jupiter would not show an increase in size, just density. With brown dwarves in the 10-30 Jupiter-mass-range being the same size as (or even slightly smaller than) Jupiter, how should we interpret Kepler's finding of a planet with a diameter several times that of Jupiter? Bottom line: how can a body that large be considered a planet and not a stellar companion?

Joseph II said to Mozart, in Amadeus script, after listening to one of his operas:
- Too many notes.

[youtube]http://www.youtube.com/watch?v=IG3rgIaX ... ata_player[/youtube]


Surely if Joseph II saw this picture, he would say:
- Too many suns... and planets.
Greetings
César

beefcalf wrote:Perhaps somebody can help...

The graphic portrays the smallest stars on the bottom-right to be smaller in diameter than the largest planet orbiting the largest star in the top-left. This seems to contradict the idea that any planet with a mass larger than Jupiter would not show an increase in size, just density. With brown dwarves in the 10-30 Jupiter-mass-range being the same size as (or even slightly smaller than) Jupiter, how should we interpret Kepler's finding of a planet with a diameter several times that of Jupiter? Bottom line: how can a body that large be considered a planet and not a stellar companion?

One could argue that a planet of Jupiter's mass could be heated externally by its local sun to a size much larger than Jupiter.

On the other hand, Wikipedia claims that none of Kepler's planets are more than twice the size of Jupiter (in apparent contradiction with today's APOD).

http://en.wikipedia.org/wiki/Kepler_%28spacecraft%29 wrote:
<<On 2 February 2011, the Kepler team announced ... 1235 planetary candidates circling 997 host stars. (The numbers that follow assume the candidates are really planets, though the official papers call them only candidates. Independent analysis indicates that at least 90% of them are real planets and not false positives.) 68 planets were approximately Earth-size, 288 super-Earth-size, 662 Neptune-size, 165 Jupiter-size, and 19 up to twice the size of Jupiter.>>

Chris Peterson wrote:I fear this image is going to generate a lot of confusion. It is easy to come away thinking that these are stellar images produced by Kepler. In reality, Kepler is unable to resolve any stars, and simply produces a curve of intensity versus time for each of its targets. This image was synthesized based on the known stellar characteristics and the measured transit characteristics of each target.

Hi, thanks for this clarification. Makes me wonder though, this still seems to be incredible resolution of the instrument. The relative size of the "planet" against its sun is very small in many cases, what does that mean in terms of difference in light intensity Kepler is able to detect when the planet makes a transit?

How does Kepler tell if there are two planets transiting the star simultaneously?
John

bdsjake wrote:Hi, thanks for this clarification. Makes me wonder though, this still seems to be incredible resolution of the instrument. The relative size of the "planet" against its sun is very small in many cases, what does that mean in terms of difference in light intensity Kepler is able to detect when the planet makes a transit?

The camera is designed for a photometric precision of a few tens of ppm, which typically means millimagnitude resolution. That's sufficient to detect Earth sized planets around Sun-like stars, given enough absolute intensity.

JohnD wrote:How does Kepler tell if there are two planets transiting the star simultaneously?

You never have two planets with the same period. So if you have two planets, they will show up in the photometric record as intensity variations with two frequencies- something apparent with mathematical analysis (e.g. Fourier analysis) even if it isn't apparent visually.