HIP 85605

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HIP 85605
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 17h 29m 36.25s[1]
Declination +24° 39′ 14.12″
Apparent magnitude (V) 11.03[1]
Spectral type K4V
M dwarf?[2]
B−V color index 1.1[1][2]
Radial velocity (Rv)−21.363 ± 0.323[1] km/s
Proper motion (μ) RA: 4.751 ± 0.031 mas/yr
Dec.: -8.628 ± 0.043 mas/yr
Parallax (π)1.822 ± 0.0265 mas
Distance1,790 ± 30 ly
(549 ± 8 pc)
Absolute magnitude (MV)11.8?[2][a]
Luminosity0.001?[a] L
Temperature4700?[3] K
Other designations
2MASS J17293627+2439111, TYC 2079-1800-1, WDS J17296+2439B[1]
Database references

HIP 85605 is a star in the constellation Hercules with a visual apparent magnitude of 11.03.[1] It was thought to be a M dwarf or K-type main-sequence star potentially 18–28 light-years (5.6–8.5 parsecs) from the Sun[2][3] and possibly a companion of the brighter star HIP 85607,[b] but they are now known to be an optical double. (HIP 85605 is 1,790 ± 30 light years away, and HIP 85607 is 1,323 ± 13 light years away)

The original Hipparcos parallax measurement in 1997 was 202 mas, which would place it 16.1 light-years from the Solar System.[1] In 2007, van Leeuwen revised the number to 147 mas, or 22.2 light-years.[1] With a parallax of 147 mas (0.147 arcseconds), HIP 85605 is unlikely to be one of the 100 closest star systems to the Sun.[4] In 2014, it was estimated that HIP 85605 could approach to about 0.13 to 0.65 light-years (0.04 to 0.2 pc) from the Sun within 240,000 to 470,000 years, assuming the then-known parallax and distance measurements to the object were correct.[2][5][6] In that case its gravitational influence could have disrupted the orbits of comets in the Oort cloud and caused some of them to enter the inner Solar System.

With the release of Gaia DR2, it was determined that HIP 85605 is actually a much more distant 1790 ± 30 light-years away, and as such will not be passing remotely close to the Sun at any point in time.

See also[edit]


  1. ^ a b Assuming a distance of ~22.2 light-years based on van Leeuwen's parallax of 147mas: (3.26ly/0.147arcsecond=22.2)
  2. ^ Optical companion HIP 85607 could be a K0III orange giant ~1200 light-years from the Sun based on a small parallax of 2.72mas.


  1. ^ a b c d e f g h "HIP 85605". Strasbourg astronomical Data Center. Retrieved Jan 3, 2015.
  2. ^ a b c d e Coryn A.L. Bailer-Jones (Dec 11, 2014). "Close encounters of the stellar kind". Astronomy & Astrophysics. arXiv:1412.3648. Bibcode:2014yCat..35750035B. doi:10.1051/0004-6361/201425221.
  3. ^ a b Mamajek, Eric (2015-01-03). "Reason to Doubt the Hipparcos Distance and the Close Flyby Scenario for the "Rogue Star" HIP 85605". doi:10.6084/m9.figshare.1284334. Retrieved 2015-01-04.
  4. ^ "THE ONE HUNDRED NEAREST STAR SYSTEMS". RECONS (Research Consortium On Nearby Stars). Retrieved 2015-01-12.
  5. ^ Mamajek, Eric E.; Barenfeld, Scott A.; Ivanov, Valentin D. (2015). "The Closest Known Flyby of a Star to the Solar System". The Astrophysical Journal. 800 (1). arXiv:1502.04655. Bibcode:2015ApJ...800L..17M. doi:10.1088/2041-8205/800/1/L17.
  6. ^ Coryn Bailer-Jones (2015-01-01). "The closest encounter is Hip 85605. How reliable is this?". Retrieved 2015-01-05.

External links[edit]