Luhman 16

WISE 1049-5319 AB

The WISE 1049-5319 binary brown dwarf is the yellow disc at the center of this January 7 2010 WISE image. The individual brown dwarfs are not resolved.
Observation data Epoch J2000      Equinox J2000
Constellation	Template:Constel
Right ascension	10h 49m 18.723s
Declination	−53° 19′ 09.86″
Characteristics
Spectral type	A: L7.5 B: T0.5
Apparent magnitude (i (DENIS filter system))	14.94 ± 0.03
Apparent magnitude (J (2MASS filter system))	10.73 ± 0.03
Apparent magnitude (J (DENIS filter system))	10.68 ± 0.05
Apparent magnitude (H (2MASS filter system))	9.56 ± 0.03
Apparent magnitude (KS (2MASS filter system))	8.84 ± 0.02
Apparent magnitude (KS (DENIS filter system))	8.87 ± 0.08
Astrometry
Proper motion (μ)	RA: −2759 ± 6 mas/yr Dec.: 354 ± 6 mas/yr
Parallax (π)	496 ± 37 mas
Distance	6.6 ± 0.5 ly (2.0 ± 0.2 pc)
Orbit
Primary	A
Companion	B
Period (P)	~ 25 yr
Position (relative to A)
Component	B
Angular distance	1.5″
Projected separation	3 AU
Other designations
Whole system: Luhman 16, LUH 16, Luhman-WISE 1, WISE J104915.57-531906.1, WISE J104915.57-531906, WISE J1049-5319, WISE 1049-5319, WISE 1049-53, WISE J1049, WISE 1049, IRAS Z10473-5303, AKARI J1049166-531907, GSC2.2 S11132026703, GSC2.3 S4BM006703 Component A: Luhman 16A Component B: Luhman 16B

WISE 1049-5319 (short for WISE J104915.57-531906.1), also known as Luhman 16, is a binary brown dwarf located in the southern constellation Vela at 6.6 light-years from the Sun, making these the nearest known brown dwarfs to the Solar System, and the closest system discovered since Barnard's Star in 1916. The primary has a stellar classification of L8 ± 1, and the secondary is probably near the L/T transition. The pair orbit each other at a distance of about 3 AU with an orbital period of about 25 years.

Discovery

The brown dwarfs were discovered by Kevin Luhman, astronomer from Pennsylvania State University, from images made by the Wide-field Infrared Survey Explorer (WISE) Earth-orbiting satellite — NASA infrared-wavelength 40 cm (16 in) space telescope, which mission lasted from December 2009 to February 2011; the discovery images were taken from January 2010 to January 2011, and the discovery was announced in 2013 (the pair is only two objects announced in the discovery paper). The system was found by comparing WISE images at different epochs to reveal objects that have high proper motions.

WISE 1049-5319 appears in the sky close to the galactic plane which is densely populated by stars; the abundance of light sources makes it difficult to spot faint objects. This explains why an object so near to the Sun was not discovered in earlier searches.

Resolved.

Discovery of companion

The second component of the system was discovered also by Luhman in 2013, and was announced in the same article as the primary. Its discovery image in the i-band was taken on the night of 23 February 2013 with the Gemini Multi-Object Spectrograph (GMOS) at the Gemini South telescope, Chile. The components of the system were resolved with an angular distance of 1.5 arcsecond, corresponding to a projected separation of 3 AU; and magnitude difference of 0.45 mag.

Precovery

Although the system was first found on images taken by WISE in 2010—2011, afterwards it was precovered (i.e. was found on earlier images): Digitized Sky Survey (DSS) (1978 (IR), 1992 (red)), Infrared Astronomical Satellite (IRAS) (1983), ESO Schmidt (Red), 1984), Guide Star Catalog (GCS) (1995), Deep Near-Infrared Survey of the Southern Sky (DENIS) (1999), Two Micron All-Sky Survey (2MASS) (1999), AKARI satellite (2007).

Precovery of companion

On the ESO Schmidt Telescope image, taken in 1984, the source looks elongated with position angle 138°. The similarity of this position angle with that of the resolved pair in the GMOS image (epoch 2013) in Fig. 1 of Luhman (2013) may suggest that the time period between 1984 and 2013 may be close to the orbital period of the system (not far from original orbital period estimate by Luhman (2013)).

Discoverer

Kevin Luhman is an astronomer from Pennsylvania State University and is a researcher in Penn State's Center for Exoplanets and Habitable Worlds.

Name

Eric E. Mamajek proposed the name Luhman 16 for the system, hence the components could be called Luhman 16A and Luhman 16B. The name originates from the frequently updated Washington Double Star Catalog (WDS): Luhman has already published several new binary star discoveries which are compiled in WDS with discovery identifier "LUH". The WDS catalog now lists this system with the identifier 10493-5319 and discoverer designation LUH 16.

The rationale is: "more memorable than WISE J104915.57-531906 and any shorthand variant", and "this pair of objects is special, and it seems silly to call this object by a 22-character name (space included)".

As a binary object it is also called Luhman 16AB.

Distance

Trigonometric parallax of WISE 1049-5319, published in 2013 in its discovery paper, is 0.496 ± 0.037 arcsec, corresponding to a distance 2.02^+0.16
_−0.14 pc, or 6.58^+0.53
_−0.46 ly.

WISE 1049-5319 distance estimates

Source	Parallax, mas	Distance, pc	Distance, ly	Ref.
Luhman (2013)	496 ± 37	2.02+0.16 −0.14	6.58+0.53 −0.46

The best estimate is marked in bold.

Proximity

Currently WISE 1049-5319 is the third closest known star/brown-dwarf system to the Sun after triple system Alpha Centauri (4.37 ly) and Barnard's Star (5.98 ly), pushing Wolf 359 (7.78 ly) into fourth place. Also it holds several records: the nearest brown dwarf, the nearest L-type dwarf, and possibly the nearest T-type dwarf (if component B is of T-type).

Proximity to Alpha Centauri

WISE 1049-5319 is also the nearest known star/brown-dwarf system to Alpha Centauri, located 3.63 ly from it. This is due to both systems being located in neighboring constellations, in the same part of the sky as seen from Earth but WISE 1049-5319 is a bit further away. Before the discovery of WISE 1049-5319, the Solar System was the nearest known system to Alpha Centauri.

Space motion

WISE 1049-5319 has a large proper motion of about 2782 milliarcseconds per year.

WISE 1049-5319 proper motion estimates

Source	μ, mas/yr	P. A., °	μRA, mas/yr	μDEC, mas/yr	Ref.
Luhman (2013)	2782	277	−2759 ± 6	354 ± 6

The most accurate estimates are marked in bold.

Further reading

• Characterization of the Nearby L/T Binary Brown Dwarf WISE J104915.57-531906.1 at 2 Parsecs from the Sun, 28 Mar 2013, A. Y. Kniazev, P. Vaisanen, K. Muzic, A. Mehner, H. M. J. Boffin, R. Kurtev, C. Melo, V. D. Ivanov, J. Girard, D. Mawet, L. Schmidtobreick, N. Huelamo, J. Borissova, D. Minniti, K. Ishibashi, S. B. Potter, Y. Beletsky, D. A. H. Buckley, S. Crawford, A. A. S. Gulbis, P. Kotze, B. Miszalski, T. E. Pickering, E. Romero Colmenero, T. B. Williams

• Fast-evolving weather for the coolest of our two new substellar neighbours, 5 Apr 2013, M. Gillon, A. H. M. J. Triaud, E. Jehin, L. Delrez, C. Opitom, P. Magain , M. Lendl, D. Queloz

• X-ray non-detection of the nearest brown dwarf binary WISE 1049--5319, 26 Apr 2013, P. Gandhi, C. Done, V. D. Ivanov, N. Huelamo

• Luhman 16AB: A Remarkable, Variable L/T Transition Binary 2 pc from the Sun, 26 jul 2013, A. J. Burgasser (UCSD), J. Faherty (U. de Chile), Y. Beletsky (Las Campanas Observatory), P. Plavchan (Caltech/IPAC), M. Gillon (U. Liege), J. Radigan (STScI), E. Jehin (U. Liege), L. Delrez (U. Liege), C. Opitom (U. Liege), N. Morrell (Las Campanas Observatory), R. Osten (STScI), R. Street (Las Cumbres Observatory), C. Melis (UCSD), A. Triaud (MIT), R. Simcoe (MIT)

• Slides for Luhman 16AB: A Remarkable, Variable, L/T Transition Binary at 2 pc, Adam J. Burgasser

External links

• WISE Nabs the Closest Brown Dwarfs Yet Discovered (Universe Today March 13, 2013)
• The closest star system found in a century (phys.org March 11, 2013)
• WISE 1049-5319 ab (Solstation.com)
• Checking Out Our New Neighbors, astrobites.org, April 5, 2013