Looking For Jupiter-Class Planets Indicates Solar Systems Like Ours Are Rare (theconversation.com)

An anonymous reader writes: A high school senior from New York analyzed data for more than 1,100 stars and pinpointed the frequency of Jupiter analogs (planets with similar mass and orbital period to Jupiter) to 3%. He published his results in a paper for the Astrophysical Journal. The relative rarity of Jupiter-like planets indicates that true solar system analogs should themselves be rare. By extension, given the important role that Jupiter played at all stages of the formation of the solar system, Earth-like habitable planets with similar formation history to our solar system will be rare.

Comments

Young Man Given Undue Credit; news at 11

[Anonymous Coward]

From the article:

In a recent paper, Dominick Rowan, a high school senior from New York, and his coauthors (including astronomers from the University of Texas, the University of California at Santa Cruz and [me, a postdoctoral fellow at the University of Texas)...

Look, it's great that this kid is involved, but quit lying about his contribution; when surrounded by such co-authors, even a monkey could have participated successfully.

Re:Young Man Given Undue Credit; news at 11

[gordo3000]

or maybe he actually did the grunt work of digging through the data and running the numbers?

who knows, but lots of undergrads and even grad students get their first publication by basically doing really pedestrian grunt work for fully independent scientists. Even famous scientists usually start out that way. Why should it be any different for this kid?

We can only detect planets they pass their star

[BenJeremy]

It's rather premature to declare all those systems devoid of planets when our primary means for detecting possible planets is when they pass between our planet and their star at the same time we observe them. Jupiter takes 12 years to make an orbit. As a simple logic problem, that means that we have to one opportunity to observe Jupiter passing between Sol and some sort of earth-analog in another system.... and that makes the HUGE assumption that that earth-analog is aligned with the solar system's orbital plane. If the earth analog happens to be staring down north-south on Sol, it isn't going to detect any planets.

There are a few other ways to detect planets, but those are special cases, again, very rare, and detecting very unique planets.

Detecting Sol-like systems is still extremely difficult.

Re:We can only detect planets they pass their star

[wonkey_monkey]

We can only detect planets they pass their star

Wrong.

Re:We can only detect planets they pass their star

[Eloking]

It's rather premature to declare all those systems devoid of planets when our primary means for detecting possible planets is when they pass between our planet and their star at the same time we observe them. Jupiter takes 12 years to make an orbit. As a simple logic problem, that means that we have to one opportunity to observe Jupiter passing between Sol and some sort of earth-analog in another system.... and that makes the HUGE assumption that that earth-analog is aligned with the solar system's orbital plane. If the earth analog happens to be staring down north-south on Sol, it isn't going to detect any planets.

There are a few other ways to detect planets, but those are special cases, again, very rare, and detecting very unique planets.

Detecting Sol-like systems is still extremely difficult.

Well unless the scientist working on this are total moron, you can quite easily do some statistic analysis to guess the number of Jupiter-like planet in other planetary system even with those complication . Here's a quick example. Let's suppose the world is in 2D and make every orbit are perfectly round to simplify things. A planet have a 360 orbit and let's say we can only see the planet for 0.01 (so 1/36000) of their orbit with 100% accuracy. So if you scan 72000 star and find 4 planets, you can then make the assumption that there's 2 gas planet per planetary system on average.

Am I missing something?

Re:We can only detect planets they pass their star

[mcswell]

About the orbital plane of the other planetary systems: yes, it's a very low probability that any given star would have its planets' orbital planes appropriately aligned. However, the math is simple, allowing one to extrapolate from the small number of Solar-system like planetary systems that happen to be aligned, to the overall population of Solar system-like planetary systems. And one can also calculate the % of stars whose planetary orbits ought to be aligned vs. the number of systems we observe, to give the number of stars in the larger population that have planetary systems at all (or at least that have planetary systems that would be detectable if they were aligned; I suppose it's possible there might be planetary systems with only very small planets, which would not be detectable by this method even if aligned). And of course the chances that a planetary system will be aligned is arbitrary. Even if it weren't (if they tended to be aligned to the galactic plane, for instance), one could compute the probabilities by sampling in multiple directions.

Re:We can only detect planets they pass their star

[wonkey_monkey]

Furthermore:

https://en.wikipedia.org/wiki/...

So they are expecting to be able to detect planets via "perpendicular" observation (and may have already done so, but it's not been fully confirmed).

Too soon

[Kjella]

Jupiter has an orbital period of 12 years. From what I've understood it takes 3 passes to confirm an exoplanet, meaning 0-12 years to initial discovery + 2*12 = 24 years for a Jupiter-class planet. It's only been 23 years since the first exoplanet was discovered in 1992 and detection capability has improved much since then, so it's way too early to tell. Maybe you can start making semi-educated guesses from lack of candidates, but that too seems premature. In another 15-20 years, we'll have much better answers.

Re:Too soon

[CanadianMacFan]

That's if you are using the difference in light to detect the planets but there are other ways. If you use the wobble of the star caused by the pull of the gravity by the planet you don't have to wait for three rotations of the planet. It also allows you to examine star systems that have an orbital plane shared with Earth. If we look "down" on the system we would never see a planet move in front of the star but we would see the star move.

Re:Very rare indeed

[Kethinov]

The term star system is also misused a lot in the case when people mean planetary system. Generally star system refers to a system of stars, e.g. a binary star system.

For sufficiently small values of 'rare'

[Anonymous Coward]

At roughly 3%, that means about 100x as many Jupiter analogs in our galaxy as there is carbon dioxide in our atmosphere (by percentage).

At roughly 3%, that means there are only about 10 billion Jupiter analogs in our own galaxy of roughly 300 billion stars.

Yes, 'rare' is a relative word especially when you are dealing with numbers that seem to be beyond human comprehension.

Call 'em solar systems. Analogy: The Moon

[dwheeler]

There is a moon that orbits the Earth that English speakers normally just call "the Moon" (note the capital letter for a proper noun). That doesn't mean there aren't other moons (obviously). If we need to give it a name, I'd suggest the Latin name (Luna), but most people don't use that terminology. Similarly, we are in "the Solar System", but I don't see a problem calling other systems "solar systems"; they just aren't THE solar system.

Detection bias

[Tablizer]

Based on the plot, it looks like the type of planet/orbit detected is closely tied to the detection method. That implies we are not getting a full sample of actual planets.

Re:Very rare indeed

[spauldo]

I've heard that theory before, and I doubt its accuracy.

Life like ours, out on the surface, would have difficulty living without the magnetic field, but we evolved on this planet. Life that evolves in an ocean doesn't have to worry about radiation. Look at Europa, for instance - we think it's possible for life to evolve there, and it's in a much harsher environment than the Earth would be even without a magnetic field.

If life evolved in an ocean on a planet with a dead core, and eventually left the ocean to colonize land, it would evolve the capability of dealing with the environment. Perhaps it would have extra redundancy in its DNA analog, or maybe it would not even use a cell-based system like we do. Who knows?

That said, while life might be more common than you think, you might be right about intelligence - at least at our moment in time. I would be very surprised, however, if we were the first intelligent life in this galaxy.

Re:Very rare indeed

[Kethinov]

The astronomy community makes an exception to that pattern when you refer to a specific named star's system of planets by the star's proper noun name.

e.g. Sol is Solar System as Tau Ceti is to Tau Ceti system.