Richest Planetary System Found

[astroron (Ron)]

Just received this post from ESO,
http://www.eso.org/public/news/eso1035/

[Zubenel (Wes)]

Thx for posting the article Ron. I Wouldn't want to call this one home. 1.4 times that of the Earth. "It is very close to its host star, at just 2 percent of the Earth–Sun distance. One “year” on this planet would last only 1.18 Earth-days."

[DavidU (Dave)]

Nice article thanks Ron.

[CraigS]

Interesting (Thanks Ron);

It seems they're hypothesising that the planet exists in the first place:
“We also have good reasons to believe that two other planets are present, says Lovis".

I guess they can deduce its mass from the "wobble of only 3 km/hour", (if they can measure that), but they kind of skimmed over the bit on how they came to the conclusion that this planet is "a hot, rocky planet, similar to Corot-7b".

There was a stage when they were looking for the atmosphere trails left behind these exoplanets, to work out their chemical composition. I wonder whether they've used this technique on any of these discoveries ?

Have to see if we can get the paper & have a read.
Interesting ... thanks again.

Cheers

[michaellxv (Michael)]

Very interesting article and research.

I wonder what was the 'popular' area of research 100 years ago? The area that the general public would have an interest in and understand.

[renormalised (Carl)]

Originally Posted by CraigS

Interesting (Thanks Ron);

It seems they're hypothesising that the planet exists in the first place:
“We also have good reasons to believe that two other planets are present, says Lovis".

I guess they can deduce its mass from the "wobble of only 3 km/hour", (if they can measure that), but they kind of skimmed over the bit on how they came to the conclusion that this planet is "a hot, rocky planet, similar to Corot-7b".

There was a stage when they were looking for the atmosphere trails left behind these exoplanets, to work out their chemical composition. I wonder whether they've used this technique on any of these discoveries ?

Have to see if we can get the paper & have a read.
Interesting ... thanks again.

Cheers

A 3kmh radial velocity difference in the spectral lines is hard to detect but it is detectable.

It's most likely a rocky planet....why....because of its orbital position. A giant planet wouldn't form where the planet is simply because it would've been too hot for any gases like hydrogen and such to accumulate in any sort of amount to create a giant planet. The only material that is robust enough to withstand the temps that would've been present in the inner part of the protoplanetary accretion disk around the star are refractory elements such as iron and other metals, silicates and such. So, any planets that form in these regions are more than likely small terrestrial planets made out of these materials.

Yes, they still look at the atmospheres that are being ablated off from the hot giant planets by their parent stars. I don't think any of these planets are close enough to be undergoing atmospheric ablation. Corot 7b is one of these planets....Chthonic planets....which are basically completely ablated away gas giants. All that's left of the planet is the core, after all of the atmosphere and liquid body of the planet has been evapourated off.

[glenc (Glen)]

The mag 7.3 star HD 10180 is about 3.25 degrees south of Achernar.
Here is the BBC article http://www.bbc.co.uk/news/science-environment-11070991
"The researchers said the system around HD 10180 as unique in several respects.
It has at least five "Neptune-like planets" lying within a distance equivalent to the orbit of Mars, making it more populated than our own Solar System in its inner region. And all the planets seem to have almost circular orbits."

[CraigS]

Some interesting quotes from the paper ...

i) on the precision of the measurements:
"Long-term radial velocity monitoring at 1 m s−1 precision was necessary to detect the low RV amplitudes of these planets".
...
"Following 400 stars to search for radial velocity signals at the m s−1 level requires a lot of telescope time, and this survey is by construction a long-term project".

I'll bet it is ... oops .. not allowed to mention the 'b*t' word. Sorry.

ii) on atmosphere detection:
"The characterization of a significant sample of low-mass objects, through their mean density and some basic atmospheric properties, is also at hand and will bring much desired insights into their composition and the physical processes at play during planet formation".

Overall, it seems like they're trying to probe (establish?) the relationship between metallicity of the star and the planetary system mass. Pretty tenuous relationship at this stage, too - lots more data/discoveries required, I think. (Ie: from the graphs presented in the conclusion section).

Cheers

[renormalised (Carl)]

Originally Posted by CraigS

Some interesting quotes from the paper ...

i) on the precision of the measurements:
"Long-term radial velocity monitoring at 1 m s−1 precision was necessary to detect the low RV amplitudes of these planets".
...
"Following 400 stars to search for radial velocity signals at the m s−1 level requires a lot of telescope time, and this survey is by construction a long-term project".

I'll bet it is ... oops .. not allowed to mention the 'b*t' word. Sorry.

ii) on atmosphere detection:
"The characterization of a significant sample of low-mass objects, through their mean density and some basic atmospheric properties, is also at hand and will bring much desired insights into their composition and the physical processes at play during planet formation".

Overall, it seems like they're trying to probe (establish?) the relationship between metallicity of the star and the planetary system mass. Pretty tenuous relationship at this stage, too - lots more data/discoveries required, I think. (Ie: from the graphs presented in the conclusion section).

Cheers

There's been dozens of surveys done over a period of 15-20 years or more. They use the data from all of them. However, there's not been a single multi-decade continuous survey undertaken yet. That's why they should build a few large scopes dedicated to such a project.

There is a relationship between metallicity and the planets that form around these stars. The higher the star's metallicity, it seems, the more likely the planets forming around it will be giant planets and the higher the Fe/H ratio, the heavier the planets are. Conversely, the less metallicity, the smaller the planets or even no planets at all. The metallicity determines the size and the make up of the protoplanetary disks around the stars. High metallicity means more material, especially refractory elements...low metallicity means less material and mostly gases and ices.

[CraigS]

Pretty tenuous relationship at this stage, too - lots more data/discoveries required, I think.

Originally Posted by renormalised

There is a relationship between metallicity and the planets that form around these stars. The higher the star's metallicity, it seems, the more likely the planets forming around it will be giant planets and the higher the Fe/H ratio, the heavier the planets are. Conversely, the less metallicity, the smaller the planets or even no planets at all. The metallicity determines the size and the make up of the protoplanetary disks around the stars. High metallicity means more material, especially refractory elements...low metallicity means less material and mostly gases and ices.

Yep. Not questioning the rationale - it makes sense.
They need more data. So far, they've got 15 datapoints.

Cheers

[renormalised (Carl)]

That's this research specifically only has 15 data points...not enough.

From the Doppler shift spectral line surveys they've done and the measurements of stellar metallicity of Sun-like stars they've taken, it appears only around 5% of all Sun-like stars have these large, close in gas giants* (hot Jupiters and the like). All those stars have higher metallicities than the Sun.

*(That's Saturn sized planets and larger within the equivalent orbit of Mercury about their parent stars.)