View source for MOA-2009-BLG-387Lb

{{Short description|Extrasolar planet in the constellation Sagittarius}}
{{good article}}
{{Infobox planet
| name                     = MOA-2009-BLG-387Lb
| image                    =
| caption                  = Artistic simulation of the dim exoplanet MOA-2009-BLG-387Lb. The [[Milky Way Galaxy|Milky Way]] bulge is visible in the background.
<!-- DISCOVERY           -->
| discoverer               = Virginie Batista ''et al.'' <ref name="Batista2011"/>
| discovery_site           = [[South African Astronomical Observatory|SAAO]]/[[Perth Observatory|Perth]]/[[Canopus Hill Observatory|Canopus]]<br />[[Auckland Observatory|AO]]/[[Farm Cove Observatory|FCO]]/[[Wise Observatory|Wise]]/[[Haleakala Observatory|HO]]/[[Siding Spring Observatory|SSO]]/[[La Silla Observatory|LSO]]/[[Roque de los Muchachos Observatory|ORM]]<ref name="Batista2011"/>
| discovered               = Published February 21, 2011 <ref name="Batista2011"/>
| discovery_method         = [[Gravitational microlensing]]
<!-- DESIGNATIONS        -->
<!-- ORBITAL             --> 
| apsis                    = astron
| semimajor                = 1.8 {{±|0.9|0.7}}<ref name=EPE /> [[astronomical unit|AU]]
| period                   = 1970 {{±|2.2|1.6}}<ref name=EPE /> [[day|d]]<br>5.4 <ref name="Batista2011"/> [[year|y]]
| star                     = [[MOA-2009-BLG-387L]]
<!-- PHYS CHARS          --> 
| mass                     = 2.6 {{±|4.1|1.6}}<ref name=EPE /> {{Jupiter mass|link=y}}
<!-- ATMOSPHERE          --> 
<!-- NOTES               --> 
}}
'''MOA-2009-BLG-387Lb''' is an [[exoplanet]] in the orbit of the red dwarf [[MOA-2009-BLG-387L]]. Its discovery was announced on February 21, 2011, making it the eleventh planet discovered using [[gravitational microlensing]]. The planet is thought to be over twice the mass of Jupiter and to have an orbit 80 percent larger than that of Earth's, lasting approximately 1,970 days. However, its exact characteristics are difficult to constrain because the characteristics of the host star are not well known.

==Characteristics==
===Mass and orbit===
MOA-2009-BLG-387Lb is a [[gas giant]], with an estimated [[Jupiter mass|mass]] 2.6 times that of Jupiter's and a radius of 1.75 times that of Jupiter and an estimated [[semimajor axis|mean distance]] of 1.8 [[astronomical unit|AU]] from its host star. It has an [[orbital period]] of approximately 1970 days.<ref name=EPE /> Although the mass and mean distance of MOA-2009-BLG-387Lb is estimated, the [[confidence interval]]s are very large, indicating that there is a large uncertainty present. These uncertainties are largely due to how the exact parameters of the host star are not known.<ref name="Batista2011"/>

===Host star===
{{main|MOA-2009-BLG-387L}}
The planet is the only one known to be in the orbit of the star [[MOA-2009-BLG-387L]], which is an [[stellar classification#Class M|M-type]] dwarf star that has a [[solar mass|mass]] that is approximately 0.19 times that of the Sun. The star is located at an estimated 5700 [[parsec]]s (18,591 [[light year]]s) from the Earth.<ref name=EPE /> The star is named for the [[Microlensing Observations in Astrophysics]] group, which saw the star as a [[gravitational microlensing]] event in 2009 and combed the data in hope of discovering a planet.<ref name="Batista2011"/>

==Discovery==
MOA-2009-BLG-387 was a [[gravitational microlensing]] event detected by the [[Microlensing Observations in Astrophysics]] collaboration on July 24, 2009, which searches and documents chance and brief alignments of stars with other stars or objects; such alignments cause a [[gravitational lens]] effect, which bends light and causes distorted, but magnified, images that can be interpreted. The detection of two [[caustic (optics)|caustics]] were logged over the next few days by the [[South African Astronomical Observatory]], the [[Perth Observatory]], and the [[Canopus Hill Observatory]] in Tasmania, with a separation of about seven days between caustic events.<ref name="Batista2011"/>

On June 7, 2010, long after the microlensing event had subsided, the science teams studying the star used the [[Very Large Telescope#Instruments|NACO]] [[adaptive optics]] facility at the [[Very Large Telescope]] in Chile to determine the actual [[apparent magnitude]] of the star that microlensed its background star, hoping to compare it to the magnitude of the star measured during the microlensing event. A discrepancy was found, a discrepancy that may have been a result of either error or of a planetary body. Interpretation of follow-up observations led to the planet's confirmation. The ratio between the planet's mass and its host star's mass is well-constrained, but a large interval of uncertainty exists because the host star's mass is known within a large [[confidence interval]] that spans the mass of all [[red dwarf]] stars.<ref name="Batista2011"/>

The discovery of the planet MOA-2009-BLG-387Lb was published on February 21, 2011 in the journal ''[[Astronomy and Astrophysics]]'' by the [[European Southern Observatory]].<ref name="Batista2011"/>

==References==
{{reflist|refs=
<ref name=EPE>{{cite web |url=http://www.exoplanet.eu/star.php?st=MOA-2009-BLG-387L |archive-url=https://web.archive.org/web/20110505022638/http://exoplanet.eu/star.php?st=MOA-2009-BLG-387L |url-status=dead |archive-date=May 5, 2011 |title=Notes for star MOA-2009-BLG-387L |author=Jean Schneider |date=2011 |work=[[Extrasolar Planets Encyclopaedia]] |access-date=13 May 2011}}</ref>

<ref name="Batista2011">{{cite journal | title=MOA-2009-BLG-387Lb: A massive planet orbiting an M dwarf | last1=Batista | first1=Virginie | last2=Gould | first2=A. | last3=Dieters | first3=S. | last4=Dong | first4=Subo | last5=Bond | first5=I. | last6=Beaulieu | first6=J.P. | last7=Maoz | first7=D. | last8=Monard | first8=B. | last9=Christie | first9=G.W. | display-authors=1 | journal=Astronomy and Astrophysics | date=2011 | volume=529 | pages=A102 | doi= 10.1051/0004-6361/201016111 | arxiv=1102.0558 | bibcode=2011A&A...529A.102B | s2cid=20954769 }} Data catalog: {{bibcode|2011yCat..35299102B}}</ref>

}}

{{2011 in space}}{{Sagittarius (constellation)}}{{DEFAULTSORT:MOA-2009-BLG-387Lb}}
[[Category:Sagittarius (constellation)]]
[[Category:Giant planets]]
[[Category:Exoplanets discovered in 2011]]
[[Category:Exoplanets detected by microlensing]]