04 June 2017

Astronomy & Astrophysics: “Gliese 710 will pass the Sun even closer”

Using data from the Gaia mission we obtained results that are ten times more accurate than from HIP2 catalogue, and the closest approaching clone passes the Sun at a distance as close as 2702 AU. 90% of clones will pass the Sun between 8250 and 19038 AU from the Sun. The estimated most probable minimum distance is more than four times smaller than for nominal solution based on HIP2 data. Figure 2 shows how the diameter of the clone cloud has changed due to Gaia data. The new radius represents less then 10% of the old one based on HIP2. This shows the precision of Gaia observations. If we look at uncertainties of astrometric parameters, we see that they are 5 to 20 per cent of those from Hipparcos, and we must remember that they are from only one year of Gaia observations.

Much closer star passage described in this paper results in an observable comet stream containing 35 times the number of comets in comparison to results derived from Hipparcos data (after population rescaling). When we take into account the expected real population of the Oort Cloud (1011) this means that Gliese 710 will trigger an observable cometary shower with a mean density of approximately ten comets per year, lasting for 3−4 Myr. Moreover, comets arriving during the first 0.6 Myr after the stellar passage (those triggered directly towards the Sun) will be concentrated near the star anti-perihelion direction (black dots and black part of the histogram). The remainder of observable comets will be highly dispersed over large regions of the celestial sphere.

Filip Berski & Piotr A. Dybczyński

A million and a half years from now, the Solar System will experience an extremely close encounter with another star, Gliese 710. Assuming there will still be some form of consciousness around here to witness the event, it should be quite a show – and also increased collision danger for every object in the system for the next couple of million years. It would be a good opportunity to study another star in detail, to send probes to orbit it, and maybe even a ‘human’ colony. If interstellar travel is as taxing at it currently appears, I could imagine a very long-lived civilization taking advantage of close stellar passages to establish outposts around other stars and spread throughout the galaxy, albeit at a glacial pace.

Structure of the observable comet swarm triggered by Gliese 710
Structure of the observable comet swarm triggered by Gliese 710. The initial parameters of the star are presented in the upper left corner while the parameters of the simulation are shown in the lower right one. The DLDW model (Dones et al. 1998) of the cloud was used. The projection of the GJ 710 heliocentric orbit is marked by a dashed line. The stellar perihelion (the position at the proximity) is shown as a big, black dot, while the small open circle denotes its anti-perihelion direction. The observable comet influx begins shortly after the star passage and gains its maximum 1 Myr later.

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