HD 10180 - 6±1 planets

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Re: HD 10180 - 6±1 planets

Post by Borislav on 24th August 2010, 5:41 am

Interestingly, once the two planets in the system have a record low K

HD10180g T=602(11) days 21.3 MEarth K=1.55(0.22) m/s
HD10180b T=1.17 days 1.4(0.25) MEarth K=0.82(0.14) m/s (not confirmed)

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Re: HD 10180 - 6±1 planets

Post by Borislav on 24th August 2010, 6:03 am

Wow! Possible eighth habitable planet!

From this analysis (Fig. 12), one can see that stable orbits are possible beyond 6 AU (outside the outermost planet’s orbit). More interestingly, stability appears to be also possible around 1 AU, which corresponds to orbital periods within 300 − 350 days, between the orbits of planets f and g, exactly at the habitable zone of HD10180. Among the already known planets, this is the only zone where additional planetary mass companions can survive. With the current HARPS precision of ∼1 ms−1, we estimate that any objectwith a minimummass M > 10 M⊕ would already be visible in the data. Since this does not seem to be the case, if we assume that a planet exists in this stable zone, it should be at most an Earth-sized object.

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Re: HD 10180 - 6±1 planets

Post by Edasich on 24th August 2010, 9:43 am

Gosh. It would sound like quite an exotic system. A orde of Neptune mass worlds and and Earth-sized one in between?

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Re: HD 10180 - 6±1 planets

Post by Lazarus on 24th August 2010, 1:18 pm

So much for 55 Cancri... at least Sol is still safe.

Hmmm another "smallest planet" claim for something that's still far too massive. And PSR B1257+12 remains the only exoplanetary system that has a configuration looks remotely like our own inner solar system: a bunch of Neptunes within the ice line is definitely not what we've got here. Raises the question of whether any additional planets orbit beyond planet h, they mention they've ruled out Jupiters within 10 AU, but whether any more Neptunes/super-Earths exist would be an interesting question.

(Slightly weird that the least-secure planet is designated b, might be a bit awkward if it turns out to be a false detection. Wouldn't want to end up with two competing nomenclature systems as in the case of Mu Arae, surely?)

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Re: HD 10180 - 6±1 planets

Post by Stalker on 24th August 2010, 1:45 pm

Why HD 10180 is listed as a confirmed planet by EPE?

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Re: HD 10180 - 6±1 planets

Post by philw1776 on 24th August 2010, 3:40 pm

I found this ESO press release statement interesting...

"The newly discovered system of planets around HD 10180 is unique in several respects. First of all, with at least five Neptune-like planets lying within a distance equivalent to the orbit of Mars, this system is more populated than our Solar System in its inner region, and has many more massive planets there. Furthermore, the system probably has no Jupiter-like gas giant. In addition, all the planets seem to have almost circular orbits.

So far, astronomers know of fifteen systems with at least three planets. .
Using the new discovery as well as data for other planetary systems, the astronomers found an equivalent of the Titius–Bode law that exists in our Solar System: the distances of the planets from their star seem to follow a regular pattern. “This could be a signature of the formation process of these planetary systems,” says team member Michel Mayor.
"

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Re: HD 10180 - 6±1 planets

Post by Lazarus on 25th August 2010, 5:06 pm

Borislav wrote:Wow! Possible eighth habitable planet!

From this analysis (Fig. 12), one can see that stable orbits are possible beyond 6 AU (outside the outermost planet’s orbit). More interestingly, stability appears to be also possible around 1 AU, which corresponds to orbital periods within 300 − 350 days, between the orbits of planets f and g, exactly at the habitable zone of HD10180. Among the already known planets, this is the only zone where additional planetary mass companions can survive. With the current HARPS precision of ∼1 ms−1, we estimate that any objectwith a minimummass M > 10 M⊕ would already be visible in the data. Since this does not seem to be the case, if we assume that a planet exists in this stable zone, it should be at most an Earth-sized object.

I'm not entirely clear how they conclude that 1 AU is "exactly at the habitable zone" of a star with a luminosity (given in table 1) of 1.49 times solar... that would put a planet at that location closer to the star than several definitions of the habitable zone would allow.

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Re: HD 10180 - 6±1 planets

Post by tommi59 on 25th August 2010, 5:17 pm

HZ of star HD 10180 is 10-15 % further than sun.I mean HZ is from 0.85 AU with high albedo to 2.0 AU with low albedo,dense atmosphere.Our earth would be so far as 1.15 AU from this star placed in this system


Last edited by tommi59 on 26th August 2010, 7:29 am; edited 1 time in total

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Re: HD 10180 - 6±1 planets

Post by Sirius_Alpha on 25th August 2010, 8:03 pm

I was thinking about that, too. Considering the equilibrium temperature of Earth is just about at the freezing point of water, I guess the "HZ" would be closer to the star than we would expect based on the location of Earth.

Edit: Changed title.

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Re: HD 10180 - 6±1 planets

Post by Sirius_Alpha on 28th September 2010, 8:47 pm

Make of this what you will.


Pair-correlation analysis of HD 10180 reveals a possible planetary orbit at about 0.92 AU
http://arxiv.org/abs/1009.5507

The pair-correlations between the positions of the six known planets in the exoplanetary system HD 10180 are studied. There are six non-trivial and almost equally spaced peaks. This demonstrates longer-ranged positional order between the orbits and suggests a seventh orbit at 0.92 AU that is consistent with these correlations.

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Re: HD 10180 - 6±1 planets

Post by Lazarus on 29th September 2010, 2:57 am

As far as I can make out that is just numerology. They pull various quantities out of the air (e.g. taking sigma = 0.075, where do they get that from?). It's just Titius-Bode with fancier mathematics.

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Re: HD 10180 - 6±1 planets

Post by Sirius_Alpha on 5th April 2012, 8:37 pm

Lazarus wrote:More planets than any other known system... wait a second, eight is the number to beat, no?

Well...

Evidence for 9 planets in the HD 10180 system
http://arxiv.org/abs/1204.1254

We re-analyse the HARPS radial velocities of HD 10180 and calculate the probabilities of models with differing numbers of periodic signals in the data. We test the significance of the seven signals, corresponding to seven exoplanets orbiting the star, in the Bayesian framework and perform comparisons of models with up to nine periodicities. We use posterior samplings and Bayesian model probabilities in our analyses together with suitable prior probability densities and prior model probabilities to extract all the significant signals from the data and to receive reliable uncertainties for the orbital parameters of the six, possibly seven, known exoplanets in the system. According to our results, there is evidence for up to nine planets orbiting HD 10180, which would make this this star a record holder in having more planets in its orbits than there are in the Solar system. We revise the uncertainties of the previously reported six planets in the system, verify the existence of the seventh signal, and announce the detection of two additional statistically significant signals in the data. If of planetary origin, these two additional signals would correspond to planets with minimum masses of 5.1$^{+3.1}_{-3.2}$ and 1.9$^{+1.6}_{-1.8}$ M$_{\oplus}$ on orbits with 67.55$^{+0.68}_{-0.88}$ and 9.655$^{+0.022}_{-0.072}$ days periods (denoted using the 99% credibility intervals), respectively.

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Re: HD 10180 - 6±1 planets

Post by Daniel on 5th April 2012, 11:29 pm

So what is the Best solution the 6 planets or 9 planets? It's seems that both are 99% ok

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Re: HD 10180 - 6±1 planets

Post by tommi59 on 6th April 2012, 10:39 am

Periods close to 10 and 67 are significant very likely they are planets -nice Twisted Evil almost fell from chair

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Re: HD 10180 - 6±1 planets

Post by tommi59 on 6th April 2012, 5:24 pm

Maybe 10th planet in HZ ??Now time for new planets in 61 virginis

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Re: HD 10180 - 6±1 planets

Post by Sirius_Alpha on 19th August 2014, 8:44 pm

On the Inclination and Habitability of the HD 10180 System
http://arxiv.org/abs/1408.4150

There are numerous multi-planet systems that have now been detected via a variety of techniques. These systems exhibit a range of both planetary properties and orbital configurations. For those systems without detected planetary transits, a significant unknown factor is the orbital inclination. This produces an uncertainty in the mass of the planets and their related properties, such as atmospheric scale height. Here we investigate the HD~10180 system which was discovered using the radial velocity technique. We provide a new orbital solution for the system which allows for eccentric orbits for all planets. We show how the inclination of the system affects the mass/radius properties of the planets and how the detection of phase signatures may resolve the inclination ambiguity. We finally evaluate the Habitable Zone properties of the system and show that the g planet spends 100\% of an eccentric orbit within the Habitable Zone.

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Re: HD 10180 - 6±1 planets

Post by Shellface on 19th August 2014, 11:38 pm

I would make a comment on the interesting choice of title, but why do you imply 5 planets to be valid?

Anyway… to put my spin on this, the rotational inclination of the star is >~60°, and assuming system coplanarity that means M is no more than 1.15 times M sin i. Any inclination in that range has relatively little impact on the system's nature.

As for observing the system inclination, wouldn't, like… astrometry be better? I don't know the formulae, but I expect h's astrometric signal should be within the order of magnitude of detectability with modern levels of precision. Transits still haven't been invalidated yet, either, and the prior-adjusted transit probability for c is about 15%.

…Does anyone know the formulation for the HZ boundaries used here? I thought the method I was using was right, but the numbers don't agree. Though they don't seem to consider luminosity directly…?

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Re: HD 10180 - 6±1 planets

Post by Sirius_Alpha on 19th August 2014, 11:57 pm

At the time of the original announcement (and the creation of the thread) the b and h planets were described as "unconfrimed" or "uncertain."

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Re: HD 10180 - 6±1 planets

Post by Lazarus on 20th August 2014, 4:12 pm

The HZ calculations use Kopparapu et al. (2014).

Conservative = runaway greenhouse (1 Earth mass), maximum greenhouse
Optimistic = early Venus, early Mars

Personally I'm a bit disappointed they didn't address the non-detection of planet b in a bit more detail given that both previously-published solutions detected that orbital period.

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Re: HD 10180 - 6±1 planets

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