Mu2 Octantis

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title: "Mu2 Octantis" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["planetary-systems-with-two-confirmed-planets", "binary-stars", "octans", "durchmusterung-objects", "bright-star-catalogue-objects", "henry-draper-catalogue-objects", "hipparcos-objects", "bayer-objects", "g-type-main-sequence-stars", "population-i-stars"] description: "Binary star system in the constellation Octans" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/Mu2_Octantis" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Binary star system in the constellation Octans ::

| name = Mu2 Octantis | image = |image=Octans constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=Mu2 Octantis |x=692|y=285 | caption = Location of μ2 Octantis (circled in red) | epoch = J2000.0 | constell = Octans | component1 = μ2 Oct A | ra1 = | dec1 = | appmag_v1 = | component2 = μ2 Oct B | ra2 = | dec2 = | appmag_v2 = | component1 = μ2 Oct A | class = G1V | b-v = +0.62 | u-b = +0.26 | component2 = μ2 Oct B | class2 = G1V | component1 =μ2 Oct A | radial_v = | prop_mo_ra = 156.404 | prop_mo_dec = −162.214 | pm_footnote = | parallax = 25.0327 | p_error = 0.0205 | parallax_footnote = | absmag_v = 3.28 | component2 =μ2 Oct B | radial_v2 = | prop_mo_ra2 = +163.531 | prop_mo_dec2 = | pm_footnote2 = | parallax2 = 25.0379 | p_error2 = 0.0167 | parallax_footnote2 = | reference = | axis_unitless = 932 AU | source = | component1 =μ2 Oct A | mass = | radius = | luminosity = | gravity = | temperature = | metal_fe = | rotation = days | rotational_velocity = 1.45 | age_gyr = | component2 = μ2 Oct B | mass2 = | radius2 = | temperature2 = | metal_fe2 = | age_gyr2 = | names = μ2 Oct, CCDM J20417-7521 | component1 = μ2 Oct A | names1 = | component2 = μ2 Oct B | names2 = | Simbad = HD+196067 |sn=A | Simbad2 = HD+196068 |sn2=B | NSTED = HD 196067 | EPE = HD+196067 Mu2 Octantis (μ2 Oct) is a binary star system in the constellation Octans, whose primary and secondary stars have apparent magnitudes of +6.481 and 7.153, respectively. Based on parallax measurements, it lies 130.3 light-years away.

The two stars, HD 196067 and HD 196068 (also named μ2 Oct A and μ2 Oct B), are separated at in the sky, corresponding to 740 astronomical units (AU). The semimajor axis of the stars' orbit is 932 AU.

Component A is a G-dwarf star with 1.33 and 1.73 times of the Sun's mass and radius, respectively. Component B also a G-type main-sequence star with a radius 1.19 times larger than the Sun. Their effective temperatures are similar. HD 196068 has a higher metallicity than its companion, the reasons for this are uncertain.

Planetary system

From 1998 to 2012, the system was observed using the CORALIE instrument, at the ESO's La Silla Observatory.

In November 2012, a long-period, wide-orbiting planet was deduced by radial velocity around HD 196067. The planet has been pulled to an eccentric orbit by the B star HD 196068. The planet's true mass, as measured by astrometry, is , placing it right on the traditionally adopted boundary between planets and brown dwarfs.

A second, innermost planet was detected using radial velocity observations with the CORALIE, HARPS, and ESPRESSO observatories. Despite its small orbit, it does not transit the host star.

| name = μ2 Oct A | table_ref = | period_unit = day | exoplanet = c | semimajor = | eccentricity = | period = | mass_earth = | inclination = | exoplanet = b | semimajor = | eccentricity = | period = | mass = | inclination =

References

References

1. {{cite Gaia DR3. 6369544118965772416
2. {{cite Gaia DR3. 6369544118966055296
3. (2013). "The CORALIE survey for southern extrasolar planets XVII. New and updated long period and massive planets". Astronomy and Astrophysics.
4. (2025-09-30). "Architecture of planetary systems with and without outer giant planets I. Inner planet detections around HD 23079, HD 196067, and HD 86226". [[Astronomy & Astrophysics]].
5. Paunzen, E.. (2015-08-01). "A new catalogue of Strömgren-Crawford uvbyβ photometry". Astronomy and Astrophysics.
6. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data.
7. (2023-12-06). "Elemental abundance differences in the massive planet-hosting wide binary HD 196067−68". Monthly Notices of the Royal Astronomical Society.
8. Gray, R. O.. (2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc—The Southern Sample". [[The Astronomical Journal]].
9. (2021). "Precise Masses and Orbits for Nine Radial-velocity Exoplanets". The Astronomical Journal.

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