There are an estimated 200 to 400 billion stars within the Milky Way, all of which orbit the center of our galaxy in a coordinated cosmic dance. As they orbit, stars in the galactic disk (where our sun is located) regularly shuffle and approach each other. Sometimes this can have drastic effects on the star, which is experiencing a close encounter, disrupting its systems and causing planets to be ejected.
Knowing when stars come close to our solar system and how it could shake up objects in it is therefore a concern of astronomers. Using the data collected by the Gaia Observatory, two researchers from the Russian Academy of Sciences (RAS) determined that a handful of stars will pass close to our solar system in the future, one of which will come pretty close!
The study was carried out by Vadim V. Bobylev and Anisa T. Bajkova, two researchers from the Laboratory for Galaxy Dynamics of the Pulkovo Observatory in St. Petersburg, Russia. As they had indicated, they relied on astrometric data from the Early Data Release 3 (EDR3) of the Gaia mission, which revealed kinematic properties of stars expected to be within 3.26 light years (1 parsec ) perish with the solar system.
Gaia maps the stars of the Milky Way. Credit: ESA / ATG medialab; Background: ESO / S. Brunier
To start it simply, our solar system is made up of eight designated planets and several small planets (also known as dwarf planets) orbiting our main sequence of the yellow-type G dwarf sun, surrounded by an outer ring of icy objects known as the Kuiper Belt . In addition, approximately light years from the Sun (0.5 parsecs) is a massive cloud of icy debris known as the Oort cloud, from which long-period comets originated.
These comets are generally the result of objects making close flybys with the solar system, throwing objects so far that they periodically fly through the solar system and around the sun before returning. The outer edge of the Oort cloud is estimated to be 0.5 parsecs (1.6 light years) from our Sun, making it particularly responsive to disturbances from a number of sources. As Dr. Bobylev Universe Today emailed:
“These disturbances include, on the one hand, the effects of the galaxy’s gravitational pull – the so-called galactic flood, and, on the other hand, the effects of huge molecular clouds – when the solar system flies at a sufficiently short distance from them, and on the other hand – the effect of approaching individual star fields.
“The approach of the solar system to individual stars in the field is a very rare occurrence. In addition, the impact depends (according to Newton’s law of attraction) both on the mass of the passing star and on the distance to which the approach is made. “
For astronomers, the process of finding stars that may have flown from our solar system in the past (and that could pass us in the future) began in the 1960s. Research has improved as more sophisticated instruments have become available, resulting in more detailed catalogs of nearby celestial objects. To know which stars will make a close encounter, you need to know their distance and their three speeds, Bobylev said.
This consists of the two properties of proper motion – right ascent, declination – and radial speed. Once you have all of that, you can do astrometry, which measures the positions and movements of stars and other celestial bodies accurately. To this end, ESA’s Hipparcos satellite (1989-1993) and the Gaia observatory (since 2013) were created.
Thanks to the precise data they have provided and updated catalogs of millions of stars and other celestial objects, astronomers can determine which of them are likely to have a close encounter in the future. For their study, Bobylev and Bajkova relied on the following three methods:
“The methods consist of constructing galactic orbits of the stars and the sun under study. Then, for each star, two main parameters of approach are determined – the minimum distance between the orbit of the solar system and the star and the moment of approach. The integration takes place in the interval of +/- 5 myr.
“That is why we used the simplest linear method in our work, on the one hand, and the integration of the movement into the axially symmetrical potential of the galaxy and, on the other, into the non-axially symmetrical potential of the galaxy, where the influence of the spiral structure on the movement of objects was taken into account . “
Gaia’s first sky map. Photo credit: ESA / Gaia / DPAC. Acknowledgments: A. Moitinho & M. Barros (CENTRA – University of Lisbon) on behalf of DPAC.
In the end, all three methods gave similar results: A star identified in the Gaia EDR3 database as 4270814637616488064 would make a particularly close encounter in just over a million years. Better known as Gliese 710 (HIP 89825), this variable orange-colored dwarf star of type K is about 60% as massive as our Sun and is located about 62 light-years from Earth in the Serpens constellation.
“The remarkable thing about it is that it is a candidate for very close approximation to the solar system in the future,” said Bobylev. “This candidate was first identified by Garcia-Sanchez et al., Astron. J. 117, 1042 (1999) in the analysis of stars from the Hipparcos catalog (1997). “
In particular, the simulations conducted by Bobylev and Bajkova showed that Gliese 710 would make its flyby in 1.32 million years and pass within 0.20 parsecs (0.65 light years) of our Sun. What this could mean for our solar system (and everything that lives here until then), Bobylev explained that extensive research had already been carried out on this and the signs were not so terrifying:
“A very interesting simulation of the close flight of the star Gliese 710 past the solar system was made by Berski, F. and Dybczy? Ski, P., A & A, v. 595, L10, 2016. They showed this after the approach from the outer boundaries of the Oort cloud towards the inner region of the solar system, a cometary shower occurs. True, the flux is small – about a dozen comets a year, and it will appear with a delay of 1 million years after the star’s flight. “
This artwork depicts a rocky planet being bombarded by comets. Photo credit: NASA / JPL-Caltech
Assuming humans (or their genetic descendants) will still be living in the solar system 2.32 million years from now, they will be treated with additional cometary activity. This could pose some dangers depending on the trajectory of these comets and the extent of the human infrastructure in space. Or it could just mean more options for backyard astronomy, or whatever the futuristic equivalent is!
In any case, it is always good to know when tremors will occur and how serious they will be. This is important in that this research removes much of the uncertainty surrounding near-star encounters and their effects. Said Bobylev:
The main meaning of our work is that we know for sure that there may be close encounters of stars with the solar system both in the past and in the future. There can be all sorts of surprises in the form of comets and asteroids appearing near Earth.
Our solar system has seen more than a few in the past, and these played a significant role in its development. It is entirely possible that life as we know it owes its existence to close encounters. So it’s best to keep track of all future events!
Further reading: arXiv