First sub-Earth mass moon of an extrasolar Gas Giant Found? |
First sub-Earth mass moon of an extrasolar Gas Giant Found? |
Dec 17 2013, 02:04 AM
Post
#1
|
|
Member Group: Members Posts: 723 Joined: 13-June 04 Member No.: 82 |
A Sub-Earth-Mass Moon Orbiting a Gas Giant Primary or a High Velocity Planetary System in the Galactic Bulge
QUOTE We present the first microlensing candidate for a free-floating exoplanet-exomoon system, MOA-2011-BLG-262, with a primary lens mass of M_host ~ 4 Jupiter masses hosting a sub-Earth mass moon. The data are well fit by this exomoon model, but an alternate star+planet model fits the data almost as well. Nevertheless, these results indicate the potential of microlensing to detect exomoons, albeit ones that are different from the giant planet moons in our solar system. The argument for an exomoon hinges on the system being relatively close to the Sun. The data constrain the product M pi_rel, where M is the lens system mass and pi_rel is the lens-source relative parallax. If the lens system is nearby (large pi_rel), then M is small (a few Jupiter masses) and the companion is a sub-Earth-mass exomoon. The best-fit solution has a large lens-source relative proper motion, mu_rel = 19.6 +- 1.6 mas/yr, which would rule out a distant lens system unless the source star has an unusually high proper motion. However, data from the OGLE collaboration nearly rule out a high source proper motion, so the exoplanet+exomoon model is the favored interpretation for the best fit model. However, the alternate solution has a lower proper motion, which is compatible with a distant (so stellar) host. A Bayesian analysis does not favor the exoplanet+exomoon interpretation, so Occam's razor favors a lens system in the bulge with host and companion masses of M_host = 0.12 (+0.19 -0.06) M_solar and m_comp = 18 (+28 -100 M_earth, at a projected separation of a_perp ~ 0.84 AU. The existence of this degeneracy is an unlucky accident, so current microlensing experiments are in principle sensitive to exomoons. In some circumstances, it will be possible to definitively establish the low mass of such lens systems through the microlensing parallax effect. Future experiments will be sensitive to less extreme exomoons. This is not a definitive detection; as they state, there is a degeneracy between an exoplanet-exomoon system and a star-exoplanet system. But it's still the first likely exomoon detected. QUOTE The "most likely" solution found by our Bayesian analysis for this fast solution ML = 3.2MJup orbited by a moon of mm = 0.47MEarth at a 3-d separation of a = 0.13AU, with the lens system at a distance of DL = 0:56 kpc. |
|
|
Dec 18 2013, 05:00 AM
Post
#2
|
|
Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Those are some rather large values. Were they able provide the error margins in the the statistical analysis?
Extremely interesting find if it's confirmed, though. -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
|
|
|
Dec 18 2013, 08:40 AM
Post
#3
|
|
Rover Driver Group: Members Posts: 1015 Joined: 4-March 04 Member No.: 47 |
The trouble with microlensing observations is that they're very hard to confirm. They tend to be one-off events. Free-floating planets at such a (relatively) large distance won't be visible in any other way any time soon.
|
|
|
Lo-Fi Version | Time is now: 1st May 2024 - 10:20 AM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |