# Close encounters: the stars that pass nearest the Sun

> Gliese 710 will pass 0.17 light years from the Sun in 1.29 million years and outshine Sirius for 13,000 years. Our Sky Atlas finds it and other close passes, but sees only about one in twenty of the encounters that must happen.

- Publication: Global Systems Lab, Transmission Report No. R-2026-04
- Published: 2026-11-08 (updated 2026-11-08)
- Authors: Global Systems Lab
- URL: https://globalsystemslab.com/transmission/stellar-close-encounters
- Topics: Astronomy, Stars, Gaia, Solar System

**Notice.** This is experimental research by Global Systems Lab, provided as is and without warranty. It is not an official forecast, warning or statistic and must not be used for emergency, safety, planning, engineering, financial, legal or other professional decisions. Third-party data may be preliminary, delayed or revised, and their use does not imply endorsement by any agency. Full terms: https://globalsystemslab.com/disclaimer

## Abstract

Stars move, and every so often one passes close enough to the Sun to disturb the Oort cloud of comets at
the edge of the Solar System. We searched the 282,000 stars with full three-dimensional velocities in the
lab's Sky Atlas (the AT-HYG catalogue, built on Gaia DR3) for passes within 3 parsecs (9.8 light years) of
the Sun over the past and next six million years. The
closest is the orange dwarf Gliese 710, which will pass 0.051 parsecs (0.17 light years, about 10,600 times
the Earth–Sun distance) away in 1.29 million years, deep inside the Oort cloud. At its closest it will be
a magnitude −3.2 star, brighter than any star in today's sky. The second closest, HD 7977, passed 2.8 million
years ago. Our results agree with the leading published study to within about 1 % for most encounters,
but differ for the two closest, where small differences in the measurements matter most. The biggest limitation is completeness: we find
9 encounters within one parsec in ten million years, against about 200 expected.

## Key findings

1. Gliese 710 is the closest known future encounter: 0.051 pc (0.17 ly, about 10,600 au) in 1.29 million years at 14.4 km/s. The leading Gaia DR3 study puts it at 0.064 pc (90 % range 0.060–0.068 pc); another study using Gaia DR3 gets about 10,500 au, as we do.
2. At closest approach Gliese 710 will reach magnitude −3.2 in our sky, brighter than Sirius for about 13,000 years and visible to the naked eye for nearly half a million years.
3. HD 7977 passed 2.8 million years ago. We place it at 0.15 pc; the published estimate is 0.064 pc with a 90 % range of 0.019–0.117 pc. Encounters that long ago are the hardest to pin down.
4. For most encounters our distances agree with the published values to within 1 %: Ross 248 at 0.93 pc in 36,000 years and Gaia DR3 2926732831673735168 at 0.82–0.83 pc 1.66 million years ago.
5. The catalogue sees only about 5 % of the encounters that must occur. The missing ones are mostly faint red dwarfs without measured radial velocities, so every result here is a lower bound on how crowded the Sun's surroundings have been.

![Figure 1. When, and how close, each star in the Sky Atlas catalogue passes the Sun within 3 parsecs (9.8 light years), from 6 million years ago to 6 million years ahead. Larger dots are intrinsically brighter stars; red marks the passes within 1 parsec.](https://globalsystemslab.com/transmission/stellar-close-encounters/files/fig-encounters.png)

## Introduction

The Sun is not standing still among the stars. It moves at about 20 kilometres per second relative to its
neighbours, and they move too, so over thousands of years the nearest stars change. Alpha Centauri, the
closest star system today at 4.3 light years, is still approaching and will be nearest in about 28,000
years. Over millions of years, some stars come much closer than that.

Close passes matter because of the Oort cloud, the vast shell of icy bodies thought to surround the Solar
System out to around a light year or more. A star that passes through it can nudge some of those bodies
onto paths toward the inner Solar System. Bailer-Jones (2022) frames the stakes plainly: close encounters
could affect life on Earth through comets sent inward or through exposure to radiation. Kaib and Raymond
(2024) add a subtler effect: a close pass can slightly alter the orbits of the giant planets, and through
them the long-term history of Earth's orbit that geologists use to date ancient climate changes.

The best-known future encounter is Gliese 710, an orange dwarf about 62 light years away in the
constellation Serpens. Its close pass was first suspected decades ago, and each new release of data from
the European Space Agency's Gaia mission has pulled the estimate closer. The best-known past encounter is
Scholz's star, a dim red dwarf with a brown dwarf companion that passed about 0.8 light years from the Sun
70,000 years ago (Mamajek et al. 2015).

The Sky Atlas, the lab's new three-dimensional map of 327,702 stars, holds the positions and velocities
needed to look for these passes. This report asks three questions. Which stars come closest to the Sun
over the past and next six million years? How well do our answers match the published studies? And how
much of the true picture can a catalogue like ours see?

## Data

The Sky Atlas is built on AT-HYG version 3.2 (Nash), which combines the Tycho-2, Hipparcos, Yale
Bright Star and Gliese catalogues with distances and velocities from Gaia Data Release 3 (Gaia
Collaboration 2023). It contains every star brighter than visual magnitude 10, plus all known stars within
100 light years. Of its 327,702 stars, 282,304 have a full three-dimensional velocity: a measured motion
across the sky and a measured radial velocity, the speed toward or away from us. Only those stars can be
followed reliably through time.

We used the Sky Atlas to find every one of these stars that comes within 3 parsecs of the Sun between six
million years ago and six million years from now, how close it comes and when, and how bright it appears
from Earth along the way. We compare the results with Bailer-Jones (2022), the most detailed published study
of close encounters in Gaia DR3.

## Results


### Gliese 710 is the closest pass we know of

Of the 86 encounters within 3 parsecs that the catalogue reveals in the twelve million years examined (Figure 1),
one stands far apart. Gliese 710 will pass 0.051 parsecs from the Sun, or 0.17 light years, about 10,600
times the distance from the Earth to the Sun. It will do so in 1.29 million years, moving at 14.4
kilometres per second, slowly by the standards of passing stars. Slow passes are the most disruptive,
because the star spends longer near the comets it disturbs.

That distance lies well inside the Oort cloud. For comparison, Proxima Centauri, the nearest star today, is
about 25 times farther away than Gliese 710 will be at its closest.

The published value from Bailer-Jones (2022) is 0.0636 parsecs, about 13,100 times the Earth–Sun distance,
with a 90 % range of 0.0595 to 0.0678 parsecs, in 1.3 million years. Our value lies just below that range.
Another group working from Gaia DR3, Pilat-Lohinger and colleagues (2026, not yet peer reviewed), calculated
about 10,500 times the Earth–Sun distance at 1.294 million years, which matches ours closely. In their
simulation of 168 million comets disturbed by the pass, more than a thousand were sent to within roughly
Earth's distance of the Sun. Whichever value is right, Gliese 710 will pass through the comet cloud, not
merely near it.

### A new brightest star, for a while

![How bright Gliese 710 will look from Earth as it passes, from 1.0 to 1.6 million years from now. Lower magnitudes are brighter; dashed lines mark the naked-eye limit, Sirius (the brightest star in today's night sky) and Jupiter at its brightest.](https://globalsystemslab.com/transmission/stellar-close-encounters/files/fig-gliese710-brightness.png "Source: Global Systems Lab Sky Atlas (AT-HYG v3.2 / Gaia DR3), 8 Nov 2026")

Today Gliese 710 is a magnitude 9.7 star, invisible without a telescope. In our calculation it becomes
visible to the naked eye about 1.06 million years from now and stays visible for nearly half a million
years. For about 13,000 years around its closest approach it will outshine Sirius. At its peak it reaches
magnitude −3.2, brighter than Jupiter ever appears today and second only to Venus among the points of
light in the sky. It will also move quickly across the sky by stellar standards, crossing a large part of
it within a few thousand years either side of its closest pass.

### HD 7977, 2.8 million years ago

The second-closest encounter in the catalogue happened in the past. HD 7977, a Sun-like star now 247 light
years away in Cassiopeia, passed the Sun 2.77 million years ago. Bailer-Jones (2022) first identified it as
one of the closest known encounters, with a median distance of 0.064 parsecs and a one-in-three chance that
it came within 0.05 parsecs. We find 0.148 parsecs, about 30,000 times the Earth–Sun distance, which is
outside the published 90 % range of 0.019 to 0.117 parsecs.

![Closest distance to the Sun for four stars, from the Sky Atlas (diamonds) and from Bailer-Jones (2022) (circles, with 90 % ranges where wide enough to see).](https://globalsystemslab.com/transmission/stellar-close-encounters/files/fig-comparison.png "Source: Global Systems Lab Sky Atlas; Bailer-Jones (2022), ApJ Letters 935, L9")

The difference is instructive. For Ross 248, a red dwarf that will pass 0.93 parsecs from the Sun in
36,000 years, and for the star Gaia DR3 2926732831673735168, which passed 0.82 parsecs away 1.66 million
years ago, our values and the published ones agree to within about 1 %. Both encounters are either recent
or fast, which makes them easy to pin down. HD 7977 is the opposite case: a slow pass nearly three million
years ago, where a small change in the measured speed moves the closest point a long way. Kaib and
Raymond (2024) used a range of about 4,000 to 31,000 times the Earth–Sun distance for HD 7977; our value
sits at the far end of that range.

### Close neighbours, closer soon

The nearest encounters in time are also familiar names. Alpha Centauri A and B will be nearest in about
28,000 years at 2.9 light years, and Proxima Centauri at 3.1 light years about the same time. Barnard's
Star, the fastest-moving star across our sky, makes its closest pass in under 10,000 years at 3.8 light
years. Ross 248 passes at 3.0 light years in 36,000 years, and Gliese 445 at 3.3 light years in 44,000
years. For a few tens of thousands of years, the Sun's immediate neighbourhood will be noticeably more
crowded than it is now.

### What the catalogue cannot see

![Number of encounters within a given distance over ten million years (from 5 million years ago to 5 million years ahead): those found in the Sky Atlas catalogue, and those expected from the encounter rate of Bailer-Jones et al. (2018), corrected for missing stars.](https://globalsystemslab.com/transmission/stellar-close-encounters/files/fig-completeness.png "Source: Global Systems Lab Sky Atlas (AT-HYG v3.2 / Gaia DR3), 8 Nov 2026; Bailer-Jones et al. (2018)")

Correcting for the stars that surveys miss, Bailer-Jones and colleagues (2018) estimated that about 19.7
stars pass within one parsec of the Sun every million years, a figure that should rise with the square of
the distance. Over the ten million years from 5 million years ago to 5 million years ahead, that means
about 200 passes within one parsec and nearly 1,800 within three. The catalogue finds 9 and 86: about one
in twenty, at every distance.

The reason is clear from the stars it does find. Their median true brightness is close to the Sun's, and
only one in three is fainter than absolute magnitude 9. Yet in the catalogue's own census of stars within
33 light years, three in four are that faint, and the true share is higher still, since the faintest red
and brown dwarfs are missing even there. Most stars are small, dim red dwarfs, and dim stars rarely have
measured radial velocities. Scholz's star, the closest known pass in the recent past, is one of them: it is
too faint to be in this catalogue at all.

## Uncertainty and limitations

**Long time spans.** Encounters millions of years in the past or future are the least certain: the
Galaxy's gravity bends every star's path over that time, and small errors in measured speed grow. For the two
closest encounters our distances differ from the published study by 20 % for Gliese 710 and by more than a
factor of two for HD 7977. For long-ago encounters, the published ranges are the better guide.

**Measurement errors.** We report one best value for each encounter, without an uncertainty range. For a slow, distant star like HD 7977, a small error in radial velocity moves the
closest point by tens of thousands of times the Earth–Sun distance. The published ranges are the better
guide to how sure anyone can be.

**Input data.** AT-HYG gives the brightest stars, including Alpha Centauri, distances from Hipparcos rather
than Gaia, and its radial velocities may come from catalogues other than Gaia's. Some of our encounters
that are not in the published list may come from such differences or from binary stars whose measured
speeds reflect their orbits rather than their motion through space. Bailer-Jones (2022) judged that about
a third of the formal encounters within one parsec in Gaia DR3 are spurious or affected by binarity; the
same caution applies here.

**Completeness.** The catalogue sees about 5 % of the encounters that must occur. The list of named stars
here is therefore a list of the brighter visitors, not of all of them, and any rate or frequency read from
it would be far too low.

**What would change the conclusions.** The next Gaia release, Data Release 4, is due on 2 December 2026 and
covers 66 months of observations, nearly twice as many as DR3. Its improved distances and radial velocities
for many more faint stars should both refine the closest encounters and add new ones.

## Conclusions

Gliese 710 will pass through the Sun's comet cloud in about 1.29 million years, closer than any other star
known, and for a few thousand years it will be the brightest star in Earth's sky. Its exact distance, between
roughly 10,500 and 13,100 times the Earth–Sun distance depending on the study, matters for how many
comets it disturbs but not for the fact that it will disturb them. HD 7977 probably came almost as close
2.8 million years ago, though how close depends sensitively on details that current data cannot pin down.

The Sky Atlas recovers the well-known encounters and agrees closely with careful published work for most of
them. It also makes plain how much remains
unseen: about nineteen in twenty of the passes the Sun experiences involve stars too faint for their speeds
to be on record.

When Gaia DR4 is released next month, we will rebuild the Sky Atlas on it and repeat this search. Every star
in this report can be followed in the [Sky Atlas](https://globalsystemslab.com/sky-atlas/) today.

## References

1. Bailer-Jones, C. A. L. (2022). Stars that approach within one parsec of the Sun: new and more accurate encounters identified in Gaia Data Release 3. *The Astrophysical Journal Letters*, 935, L9. https://arxiv.org/abs/2207.06258
2. Bailer-Jones, C. A. L. (2022). Stellar encounters with the Sun in Gaia DR3: tables and plots. Max Planck Institute for Astronomy (accessed 8 November 2026). https://bailer-jones.www3.mpia.de/stellar_encounters_gdr3.html
3. Bailer-Jones, C. A. L. (2022). Stellar encounters with the Sun in Gaia DR3. Poster, Max Planck Institute for Astronomy, summarising the completeness-corrected encounter rate of Bailer-Jones et al. (2018), *The Astronomical Journal*, 156, 58. https://www.mpia.de/homes/calj/stellar_encounters_gdr3/stellar_encounters_gdr3_mpia_poster.pdf
4. Pilat-Lohinger, E., Zimmermann, M. and Loibnegger, B. (2026). Oort cloud comets: perturbations due to the passage of Gliese 710. Preprint, *Preprints.org*, doi:10.20944/preprints202604.2210.v1 (not peer reviewed). https://www.preprints.org/manuscript/202604.2210/v1
5. Kaib, N. A. and Raymond, S. N. (2024). Passing stars as an important driver of paleoclimate and the Solar System's orbital evolution. *The Astrophysical Journal Letters*. https://iopscience.iop.org/article/10.3847/2041-8213/ad24fb
6. Mamajek, E. E. et al. (2015). The closest known flyby of a star to the Solar System. *The Astrophysical Journal Letters*, 800, L17. https://doi.org/10.1088/2041-8205/800/1/L17
7. Nash, D. AT-HYG: Augmented Tycho + HYG stellar database, version 3.2. Astronexus, CC BY-SA 4.0 (accessed 7 November 2026). https://www.astronexus.com/projects/at-hyg
8. Gaia Collaboration, Vallenari, A. et al. (2023). Gaia Data Release 3: summary of the content and survey properties. *Astronomy & Astrophysics*, 674, A1. https://arxiv.org/abs/2208.00211

## Data availability

The figures cover every encounter within 3 parsecs found in the Sky Atlas catalogue, with its time,
closest distance, speed, distance source and Gaia DR3 number, and the four-star comparison against
Bailer-Jones (2022). The catalogue is AT-HYG v3.2 (subset to visual magnitude 10, plus
all stars within 100 light years), with Gaia DR3 distances and velocities, as loaded in the Sky Atlas on
8 November 2026. The catalogue is licensed CC BY-SA 4.0. You can follow any of these stars
yourself in the [Sky Atlas](/sky-atlas/): open the Encounters tab, or choose the tour "Gliese 710's close
pass by the Sun".

## How to cite

Global Systems Lab (2026). Close encounters: the stars that pass nearest the Sun. Global Systems Lab Transmission R-2026-04. https://globalsystemslab.com/transmission/stellar-close-encounters