# Gliese 710

Gliese 710
Observation data
Epoch J2000      Equinox J2000
Constellation Serpens
Right ascension 18h 19m 50.84215s[1]
Declination –01° 56′ 18.9841″[1]
9.69[2] (9.65–9.69)[3]
Characteristics
Spectral type K7 Vk[4]
U−B color index +1.23[2]
B−V color index +1.36[2]
Variable type Suspected[3]
Astrometry
Proper motion (μ) RA: +1.15[1] mas/yr
Dec.: +1.99[1] mas/yr
Parallax (π) 51.12 ± 1.63 mas
Distance 64 ± 2 ly
(19.6 ± 0.6 pc)
Absolute magnitude (MV) 8.23 (8.19-8.23)[note 1][citation needed]
Details
Mass 0.6[6] M
Luminosity (bolometric) 0.084[note 2][citation needed] L
Luminosity (visual, LV) 0.044[note 3] L
Temperature 4,250[6] K
Rotational velocity (v sin i) 6.42 ± 0.78[10] km/s
Other designations
Gliese 710, BD–01° 3474, HIP 89825, HD 168442, NSV 10635[2]
Database references
ARICNS data

Gliese 710 is a star in the constellation Serpens Cauda which is expected to pass through our Solar System's Oort cloud 1.35 million years from now. Its distance at closest approach is expected to be about 13000 astronomical units, or a mere 77 light days,[note 4] with an uncertainty of about 50%. For comparison, Proxima Centauri is more than 1500 light days away. "This event will be the strongest disrupting encounter in the future and history of the solar system" according to astronomers Filip Berski and Piotr Dybczyński.[11] At that close distance, it would be similar in brightness to a bright planet, at an apparent visual magnitude of about -2.7 (brighter than Mars), with a total proper motion around one arcminute per year.[12][13]

Gliese 710 currently is 63.8 light-years (19.6 parsecs) from Earth in the constellation Serpens and has a magnitude of 9.69. It has a stellar classification of K7 Vk,[4] which means it is a main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. (The suffix 'k' indicates that the spectrum shows absorption lines from interstellar matter.) The mass of this star is about 60%[6] of the Sun's mass and it has an estimated 67% of the Sun's radius.[7] It is a suspected variable star that may vary in magnitude from 9.65–9.69.

Earlier studies of its proper motion, distance, and radial velocity[14] indicated that its closest approach would be closer to one light year, based on less precise Hipparcos data.[5] The proper motion of Gliese 710 is currently very small for its distance, meaning it is traveling nearly directly in our line of sight.

In a time interval of ±10 million years from the present, Gliese 710 is the star whose combination of mass and close approach distance will cause the greatest gravitational perturbation of the Solar System.

## Computing and details of the closest approach

Gliese 710 has the potential to perturb the hypothetical Oort cloud enough to send a shower of comets into the inner Solar System for millions of years, triggering about 10 visible comets per year,[13] and possibly causing an impact event.

Earlier dynamic models by García-Sánchez, et al. in 1999 indicated that the net increase in cratering rate due to the passage of Gliese 710 would be no more than 5%.[6] They estimated that the closest approach will happen in 1,360,000 years when the star will approach within 0.337 ± 0.177 parsecs (1.100 ± 0.577 light years) of the Sun.[15]

An artist's rendering of the Oort cloud and the Kuiper belt (inset)

Later calculations by Bobylev in 2010 suggested Gliese 710 has an 86% chance of passing through the Oort cloud, assuming the Oort cloud to be a spheroid around the Sun with semiminor and semimajor axes of 80,000 and 100,000 astronomical units. The distance of closest approach of Gliese 710 is difficult to compute precisely as it depends sensitively on its current position and velocity; Bobylev estimated that it would pass within 0.311 ± 0.167 pc (1.014 ± 0.545 light years) of the Sun.[5] There is even a 1/10,000 chance of the star penetrating into the region (d < 1,000 AU) where the influence of the passing star on Kuiper belt objects is significant.[5] Gliese 710 would have an apparent magnitude at the time of its closest approach of about 0.5.

The star with the second greatest perturbational effect in the past or future 10 million years was Algol,[6] a triple star system that passed at at least 9.8 light years, 7.3 million years ago, but with a considerably larger total mass of 5.8 solar masses.

## Notes

1. ^ From apparent magnitude and parallax: ${\displaystyle \scriptstyle M_{V}=m_{V}-5\log _{10}\left({\frac {100}{\mathrm {parallax\ in\ milliarcseconds} }}\right)}$
2. ^ Using the absolute visual magnitude of Gliese 710 ${\displaystyle \scriptstyle M_{V_{\ast }}=8.23}$ with a bolometric correction of ${\displaystyle \scriptstyle BC=-0.814}$[8] the bolometric magnitude can be calculated as ${\displaystyle \scriptstyle M_{bol_{\ast }}=7.416}$, the bolometric magnitude of the Sun ${\displaystyle \scriptstyle M_{bol_{\odot }}=4.73}$,[9] therefore the bolometric luminosity can be calculated by ${\displaystyle \scriptstyle {\frac {L_{bol_{\ast }}}{L_{bol_{\odot }}}}=10^{0.4\left(M_{bol_{\odot }}-M_{bol_{\ast }}\right)}}$
3. ^ Using the absolute visual magnitude of Gliese 710 ${\displaystyle \scriptstyle M_{V_{\ast }}=8.23}$ and the absolute visual magnitude of the Sun ${\displaystyle \scriptstyle M_{V_{\odot }}=4.83}$, the visual luminosity can be calculated by ${\displaystyle \scriptstyle {\frac {L_{V_{\ast }}}{L_{V_{\odot }}}}=10^{0.4\left(M_{V_{\odot }}-M_{V_{\ast }}\right)}}$
4. ^ 77 light-days is roughly 1.9 trillion kilometers (or 1.2 trillion miles). This is about a fifth (0.2) of a light-year.

## References

1. ^ a b c d van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
2. ^ a b c d "Gliese 710". SIMBAD Astronomical Database. Centre de Données astronomiques de Strasbourg. Retrieved 2010-03-18.
3. ^ a b Kukarkin, B. V.; et al. (1971), "The third edition containing information on 20437 variable stars discovered and designated till 1968", General Catalogue of Variable Stars (3rd ed.), Bibcode:1971GCVS3.C......0K
4. ^ a b Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I". The Astronomical Journal. 132 (1): 161–170. arXiv:. Bibcode:2006AJ....132..161G. doi:10.1086/504637.
5. ^ a b c d Bobylev, Vadim V. (March 2010). "Searching for Stars Closely Encountering with the Solar System". Astronomy Letters. 36 (3): 220–226. arXiv:. Bibcode:2010AstL...36..220B. doi:10.1134/S1063773710030060.
6. García-Sánchez, Joan; et al. (February 1999). "Stellar Encounters with the Oort Cloud Based on HIPPARCOS Data". The Astronomical Journal. 117 (2): 1042–1055. Bibcode:1999AJ....117.1042G. doi:10.1086/300723.
7. ^ a b Johnson, H. M.; Wright, C. D. (November 1983). "Predicted infrared brightness of stars within 25 parsecs of the sun". The Astrophysical Journal Supplement Series. 53: 643–711. Bibcode:1983ApJS...53..643J. doi:10.1086/190905.
8. ^
9. ^ Torres, Guillermo (November 2010). "On the Use of Empirical Bolometric Corrections for Stars". The Astronomical Journal. 140 (5): 1158–1162. arXiv:. Bibcode:2010AJ....140.1158T. doi:10.1088/0004-6256/140/5/1158. Lay summary.
10. ^ López-Santiago, J.; et al. (May 2010), "A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age", Astronomy and Astrophysics, 514: A97, arXiv:, Bibcode:2010A&A...514A..97L, doi:10.1051/0004-6361/200913437
11. ^ Dvorsky, George. "Incoming Star Could Spawn Swarms of Comets When It Passes Our Sun". Gizmodo. Retrieved 2016-12-24.
12. ^ Berski, Filip; Dybczyński, Piotr A. (2016-11-01). "Gliese 710 will pass the Sun even closer". Astronomy & Astrophysics. 595. doi:10.1051/0004-6361/201629835. ISSN 0004-6361.
13. ^ a b Dorminey, Bruce. "Solar System's Next Close Encounter Will Be With Gliese 710, Say Astronomers". Forbes. Retrieved 2016-12-24.