Upsilon Andromedae - Non-coplanar multi-planet system

I'm somewhat surprised this one hasn't been posted here yet...

Always Pulkovo observers once in 2004 inferred again the existence of a substellar object at 61 Cygni A. Period 6.9 years (I think), 14 Jupiter masses and e=0.4.

I don't know if trustworthy but thanks for the information

Lazarus wrote:

I'm somewhat surprised this one hasn't been posted here yet...

Maybe this is the proposed planet "outtathere."

(quick explanation: Ups And's planets got the unofficial names of Dinky, Twopiter, and Fourpiter, with a proposed ejected planet "outtathere" to explain d's eccentricity)

Sirius_Alpha wrote:

(quick explanation: Ups And's planets got the unofficial names of Dinky, Twopiter, and Fourpiter, with a proposed ejected planet "outtathere" to explain d's eccentricity)

Don't know about anyone else here, but I never liked those names...

Eh, I thought they were cute but unnecessary.

I would have such cool names for those planets, but let's not turn offtopic

Can't help but wonder if the delay in the astrometric analysis of Upsilon Andromedae is due to trying to characterise the fourth planet...

That would make sense. Perhaps d isn't actually inclined 30° to the rest of the system after all.

Why "Dinky"???

Because despite being a huge Jupiter-class planet, it is less massive than the other two. Of course the names for "c" and "d" will turn out to be even sillier if 1/sin(i) is significantly larger than 1...

Indeed. Perhaps b and c should be called "twoseineyepiter" and "fourseineyepiter", respectively. Dinky may retain its name ; ).

Excuse me, I'm not sure: has it been discovered and awaiting for publication or is it only putative?

About name, no please. Dinky as official name would be ludicrous. Funny nickname, uhm, so so...though I don't get the sense.

Classical mythology fits well with relevant planetary systems

The planet hasn't been ruled out, but it hasn't been confirmed either. It's very unconstrained. According to the abstract, only a lower limit on the orbital period could be placed.

They also mention the need for further monitoring to ensure the signature is indeed planetary in nature.

But it should not be included in discoveries yet. Am I too rigid?

Nah you're right. Not a discovery yet.

We have used high-cadence radial velocity measurements from the
Hobby-Eberly Telescope with existing velocities from the Lick, Elodie,
Harlan J. Smith and Whipple 60” telescopes combined with astrometric
data from the Hubble Space Telescope Fine Guidance Sensors to refine the
orbital parameters and determine the orbital inclinations and position
angles of the ascending node of components υ And A c and d. With these
inclinations and using M = 1.31M⊙ as a primary mass we determine the
actual masses of two of the companions: υ And A c is13.98+2.3 Mjup, and υ
And A d is 10.25+0.7 Mjup. These measurements represent the first
astrometric determination of mutual inclination between objects in an
extrasolar planetary system. The combined radial velocity measurements
also reveal a long period trend indicating a fourth planet in the
system. We investigate the dynamic stability of this system and analyze
regions of stability, which suggest a probable mass of υ And A b.
Finally, our parallaxes confirm that υ And B is a stellar companion of υ
And A

Awesome. How about a reference?

If this is true, then the inclinations for Ups And c and d are ~8° and ~24°, respectively. And from Spitzer, we're told the inclination of b is "> 30°"

Thanks, Edasich.

Impressive. If confirmed these are really hefty worlds. It will be interesting to see the stability analysis. Also the non-planarity of the orbits is very interesting.

Well that makes things interesting: reversing the mass hierarchy between υ And Ac and υ And Ad, and resulting in an object above the deuterium fusion limit (though probably too old to actually be fusing deuterium any more) being sandwiched between two planetary-mass objects. Another piece of evidence against deuterium fusion being a useful dividing line between planets and brown dwarfs.

Wonder what that does for the prediction that υ And Ad has water clouds - I suspect the internal heating in a 10 Jupiter-mass planet might be sufficient to push the temperature of this object too high for clouds to form.

(Also as an added bonus the names Twopiter and Fourpiter turn out to be woefully inadequate... though if it is true that sin(i_b) > 30°, then "Dinky" certainly looks a lot dinkier)

Incidentally, this astrometic value for the mass of planet υ And Ad is very close to the preliminary Hipparcos mass in Han, Black & Gatewood (2001), who derived an inclination of 155.5 degrees and a true mass of 10.4 Jupiter masses (apparently the table in the article has dropped a decimal point). Mazeh & Zucker (1999) also obtained a similar value from the Hipparcos data.

So two low-mass brown dwarfs or superplanets? Dilemma.
Sadly we should revisit Whatmough's suggestive artistic rendering, after official paper release. I don't trust teasers.

And still this fourth hidden planet...

Interesting about the Hipparcos data. Perhaps it may be more accurate than we had believed, if only for high mass/low inclination planets.

Fourpiter could have very massive and why not habitable moons!!!

Depends on where the outer boundary of the HZ is I suppose.

The other question is how this affects the result that the eccentricity of the middle planet's orbit returns to zero every few thousand years, particularly as a result of the altered mass hierarchy between υ And Ac and υ And Ad.