Re: Possible image of an exoplanet next to Beta Pictoris

Lazarus · by Lazarus on Sun Nov 23, 2008 1:40 pm

Far as I know, initial conditions are a bit of an unknown. Probably going to be smaller and cooler than a more massive gas giant I'd guess.

One question that is slightly worrying about these evolutionary model predictions of masses is how much these planets are still getting hit by debris in the system. A post-collision object could masquerade as a higher-mass planet.

Sirius_Alpha · by Sirius_Alpha on Sun Nov 23, 2008 1:46 pm

Continued monitoring should help constrain the true nature of the object, right? If Beta Pictoris b fades away, then it was some, relatively, low-mass object getting whacked by a planetesimal, right? I'm sure this happens often in such protoplanetary systems, but what are the odds of it actually occurring when we're observing?

Edit: Here's the paper on arXiv.
http://arxiv.org/abs/0811.3583

Edasich · by Edasich on Mon Mar 09, 2009 6:00 am

Very intriguing.

Is Beta Pic b the transiting planet of November 1981?

In 1981, Beta Pictoris showed strong and rapid photometric variations that were attributed to the transit of a giant comet or a planet orbiting at several AUs (Lecavelier des Etangs et al. 1994, 1995, 1997; Lamers et al. 1997). Recently, a candidate planet has been identified by imagery in the circumstellar disk of Beta Pictoris (Lagrange et al. 2009). This planet, named Beta Pic b, is observed at a projected distance of 8AU from the central star. It is therefore a plausible candidate for the photometric event observed in 1981. The coincidence of the observed position of the planet in November 2003 and the calculated position assuming that the 1981 transit is due to a planet orbiting at 8 AU is intriguing. Assuming that the planet that is detected on the image is the same as the object transiting in November 1981, we estimate ranges of possible orbital distances and periods. In the favored scenario, the planet orbits at about 8 AU and was seen close to its quadrature position in the 2003 images. In this case, most of the uncertainties are related to error bars on the position in 2003. Uncertainties related to the stellar mass and orbital eccentricity are also discussed. We find a semi-major axis in the range [7.6-8.7] AU and an orbital period in the range [15.9-19.5] years. We give predictions for imaging observations at quadrature in the southwest branch of the disk in future years (2011-2015). We also estimate possible dates for the next transits and anti-transits.

According to their calculations, Beta Pictoris b's radius may span between 2.3-4 Jupiter radii. affraid

Sirius_Alpha · by Sirius_Alpha on Mon Mar 09, 2009 8:59 am

Very interesting indeed. It would make sense, with the disk being edge-on and all.
If indeed it's a transiting planet, it'll transit next between Sep 2013, and Dec 2020.
The paper writes that,

If future observations happen to confirm that Beta Pictoris b is a transiting planet, the planet would be extraordinary transiting planet because it is
1) A planet transiting in front of a 3.8 magnitude star. By comparison with what has been done in the case of planets transiting 7th magnitude stars (e.g. Charbonneau et al. 2002; Sing et al. 2008a, 2008b), the atmosphere of this planet could be probed with unprecedented detail for an extrasolar planet.
2) a young planet with circumplanetary material. Through detailed transit observations, this planet could give unique information on the planet environment including rings and satellites, at a stage when satellites are still forming or just formed.
3) a planet at 8 AU. This would give access to transit observations of a planet far from its parent star, a situation more like the giant planet of the solar system and different from the hot-Jupiters

Very interesting stuff.

Sirius_Alpha · by Sirius_Alpha on Mon Mar 09, 2009 12:19 pm

Would someone check my math?
Assuming Beta Pictoris has a radius of 1.8 solar radii, and that Bet Pic b is indeed a transiting planet,
if it has a radius of 2 R_j, could we expect a transit depth of ~0.0126%?
if it has a radius of 4 R_j, could we expect a transit depth of ~5%?

Lazarus · by Lazarus on Mon Mar 09, 2009 3:29 pm

Would be a fascinating result.

And would blast HD 80606b's record for the longest-period transiting planet completely out of the water.

Edasich · by Edasich on Mon Mar 09, 2009 4:35 pm

With a radius of 4 Rj, it would look as large as a M-dwarf star.
A very very bloated jovian. cyclops

Lazarus · by Lazarus on Mon Mar 09, 2009 6:20 pm

I get 1.3% and 5.2% for the 2 R_J case and 4 R_J case respectively.

Well it is a young system so the planet hasn't had much time to cool and contract. However as the paper says, the planet seems too large. For example, the paper referenced at the Brown Dwarf and Extra-Solar Giant Planet Calculator (R.I.P.) seems to predict a radius around 1.4 Jupiter radii for such an object.

From the paper...

The observations are more consistent with a circumplanetary (proto-satellite) dust disk or a ring system around the planet, as recently inferred for the planet Fomalhaut b in a similar young debris disk (Kalas et al. 2008).

So worlds like Beta Pictoris b and Fomalhaut b may provide windows into the formation of satellite systems around gas giants. Like the hunt for exoplanets, the first results of the search for exomoons are the discs from which these objects form...

Sirius_Alpha · by Sirius_Alpha on Mon Mar 09, 2009 7:40 pm

Lazarus wrote:I get 1.3% and 5.2% for the 2 R_J case and 4 R_J case respectively.

Ah, forgot to move decimal over. Mad

Lol thanks.
Do you think that if Bet Pic b transits, any hypothetical moons will be the first exomoons detected? Or do you think we might have found others by then?

marasama · by marasama on Tue Mar 10, 2009 2:01 pm

Could the dimming be cause by a moon or ring system instead of the large radius?

Sirius_Alpha · by Sirius_Alpha on Tue Mar 10, 2009 2:44 pm

Marasama wrote:Could the dimming be cause by a moon or ring system instead of the large radius?

That's what appears to be the case.

Lazarus wrote:From the paper...
The observations are more consistent with a circumplanetary (proto-satellite) dust disk or a ring system around the planet, as recently inferred for the planet Fomalhaut b in a similar young debris disk (Kalas et al. 2008).

Lazarus · by Lazarus on Sun Mar 15, 2009 3:43 pm

Interestingly enough, the detection of the possible transit event itself was made by looking through old data... here's the paper, published in 1997.

Lecavelier des Etangs, A. et al., 1997 A&A 328, 311: "Beta Pictoris light variations. I. The planetary hypothesis"

Seems like the possible transit was detected as a result of the star being extensively monitored as it was at the time used as a photometric reference star (this was also before the existence of the dust disk was known). When these variations were detected, Beta Pictoris was dropped as a reference star and it stopped being so extensively monitored. Rather unfortunate, no?

Sirius_Alpha · by Sirius_Alpha on Sun Mar 15, 2009 8:32 pm

That is indeed unfortunate, and ironic.

Sirius_Alpha · by Sirius_Alpha on Tue Mar 31, 2009 9:23 pm

Though a bit late, and lacking interesting details such as the colour change, the possibility of a circumplanetary disk and such, Newscientist is reporting on this.

http://www.newscientist.com/article/mg20127014.700-alien-world-created-stars-odd-twinkle.html

Sirius_Alpha · by Sirius_Alpha on Tue Jun 30, 2009 8:13 pm

Constraining the orbit of the possible companion to Beta Pictoris: New deep imaging observations
http://arxiv.org/abs/0906.5520

Abstract wrote:We recently reported on the detection of a possible planetary-mass companion to Beta Pictoris at a projected separation of 8 AU from the star, using data taken in November 2003 with NaCo, the adaptive-optics system installed on the Very Large Telescope UT4. Eventhough no second epoch detection was available, there are strong arguments to favor a gravitationally bound companion rather than a background object. If confirmed and located at a physical separation of 8 AU, this young (~1500 K) massive Jovian companion (~8 Mjup) would be the closest planet to its star ever imaged, could be formed via core-accretion, and could explain most of the dust disk properties. Our goal was to return to Beta Pic five years later to obtain a second-epoch observation of the companion or, in case of a non-detection, constrain its orbit. Deep adaptive-optics L'-band direct images of Beta Pic and Ks-band Four-Quadrant-Phase-Mask (4QPM) coronagraph images were recorded with NaCo in January and February 2009. We also use 4QPM data taken in November 2004. No point-like signal with the brightness of the companion candidate (apparent magnitudes L'=11.2 or Ks~12.5$) is detected at projected distances down to 6.5 AU from the star in the 2009 data. As expected, the non-detection does not allow to rule out a background object; however, we show that it is consistent with the orbital motion of a bound companion getting closer to the star between 2003 and 2009. We place strong constraints on the possible orbits of the companion and discuss future observing prospects.

Looking through the paper, it seems that this non-detection of Beta Pictoris b does not rule out a transit way-back-yonder in 1981.