Gliese 710

Gliese 710, or HIP 89825, is an orange star in the constellation Serpens Cauda. It is projected to pass near the Sun in about 1.29 million years at a predicted minimum distance of 0.051 parsecs—0.1663 ly (about 1.60 trillion km) – about 1/25th of the current distance to Proxima Centauri. Such a distance would make for a similar brightness to the brightest planets, optimally reaching an apparent visual magnitude of about −2.7. The star's proper motion will peak around one arcminute per year, a rate of apparent motion that would be noticeable over a human lifespan. This is a timeframe, based on data from Gaia DR3, well within the parameters of current models which cover the next 15 million years.

Description
Gliese 710 currently is 62.3 ly from Earth in the constellation Serpens and has a below naked-eye visual magnitude of 9.69. A stellar classification of K7 Vk means it is a small main-sequence star mostly generating energy through the thermonuclear fusion of hydrogen at its core. (The suffix 'k' indicates that the spectrum shows absorption lines from interstellar matter.) Stellar mass is about 57% of the Sun's mass with an estimated 58% of the Sun's radius. It is suspected to be a variable star that may vary in magnitude from 9.65 to 9.69. As of 2020, no planets have been detected orbiting it.

Computing and details of the closest approach
In their 2010 work, Bobylev et al. suggested that 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 AU respectively. The distance of closest approach of Gliese 710 is generally difficult to compute precisely as it depends sensitively on its current position and velocity; Bobylev et al. estimated that Gliese 710 would pass within $−14.53$ ($-0.414$) of the Sun. At the time, there was even a 1 in 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 would be significant.

Results from new calculations that include input data from Gaia DR3 indicate that the flyby of Gliese 710 to the Solar System will on average be closer at $-0.108$ ($6.42$) in $0.311 parsecs$ time, but with considerably less uncertainty. The effects of such an encounter on the orbit of the Pluto–Charon system (and therefore, on the classical trans-Neptunian belt) are negligible, but Gliese 710 will traverse the outer Oort cloud (inside 100,000 AU or 0.48 pc) and reach the outskirts of the inner Oort cloud (inward of 20,000 AU).

Gliese 710 has the potential to perturb the Oort cloud in the outer Solar System, exerting enough force to send showers of comets into the inner Solar System for millions of years, triggering visibility of about ten naked-eye comets per year, and possibly causing an impact event. According to Filip Berski and Piotr Dybczyński, this event will be "the strongest disrupting encounter in the future and history of the Solar System." Earlier dynamic models indicated that the net increase in cratering rate due to the passage of Gliese 710 would be no more than 5%. They had originally estimated that the closest approach would happen in 1,360,000 years when the star will approach within $1.014 light-years$ ($0.051 pc$) of the Sun. Gaia DR2 later found the minimum perihelion distance to be $10,635 au$ or 13,900 ± 3,200 AU about 1.281 million years from now.

Table of parameters of predictions of Gliese 710 encounter with Sun