Image of the Week

Figure 1. Table with Gaia DR3 sources with high proper motions (pm), complemented with Hipparcos (ESA 1997) data for alpha Cen A and B. A machine-readable (CSV) version of the table is available on Zenodo . Note: dots act as decimal separators while commas separate thousands. Credits: ESA/Gaia/DPAC - CC BY-SA 3.0 IGO.

Ever since Edmond Halley, more than 300 years ago, published his "considerations on the change of the latitudes of some of the principal fixt stars" (reprint), measuring the proper motion of stars has been a fruitful scientific area. Initially, stars with large proper motions, having an increased probability to be nearby, played an important role in the first measurement of the parallax of a star (61 Cyg). Later, boosted by ESA's Hipparcos mission and culminating with Gaia data (e.g., Gaia DR1 two million stars on the move or Gaia (E)DR3 star trails), proper motions have been used for numerous studies in diverse scientific topics, ranging from star cluster membership to galactic kinematics and extra-galactic studies.

Most famously, Barnard's Star (Gaia DR3 4472832130942575872) is the object with the highest (known) proper motion, swirling over the sky with a speed in excess of 10 arcseconds per year. Another interesting case, at the other extreme of the velocity spectrum, is the object Gliese 710 (Gaia DR3 4270814637616488064). With a tiny proper motion of a mere 0.4 milli-arcseconds per year but with a signifcant radial motion (−14.53 km/s) directed towards the Sun, this star will fly by our host star, some 1.29 Myr from now, at a distance of just 0.051 ± 0.003 pc (10,635 ± 500 AU). During this fly-by through the solar system, Gliese 710 will reach an apparent visual magnitude of −2.7 and will race across the sky with a proper motion exceeding 1 arcminute per year (6 times faster than Barnard's Star today), which will be noticeable over a human lifespan.

Figure 1 above shows the table with the highest proper motion sources combining Hipparcos (ESA 1997) and Gaia DR3 (Gaia Collaboration et al. 2023) data. It supersedes this Hipparcos top-20 table. The table contains 35 entries and shows, ordered on Gaia DR3 proper motion, all sources with a total proper motion exceeding 3 arcseconds per year (arcsec/yr), complemented with Hipparcos sources in case of missing Gaia data.

Notes and caveats:

• Two Hipparcos stars are missing in Gaia DR3: alpha Cen A and B. This is a known issue in Gaia DR3 (e.g., Section 4.3 in Gaia Collaboration et al. 2021), linked to their brightness.
• With Gaia DR3 hindsight, one Hipparcos measurement (for HIP 67593 = Gaia DR3 1251932290465669120) is spurious(*). This object has been retained in the table but has been "un-numbered" in the ranking.
• Washington 5583 and 5584 are not resolved by Simbad but these common names have been retained in this table for historical purposes (see, for instance, Luyten 1923, van Maanen 1943, and ESA 1997).
• The table refers to sources, not all of which are necessarily (single) stars:
  • Some sources are (unresolved) double or multiple stars (e.g., alpha Cen A is a spectroscopic binary system);
  • Some sources are brown dwarfs(**) (e.g., Gaia DR3 6412596012146801152 and Gaia DR3 6281432246412503424).

(**) Optically very faint brown dwarfs with infra-red astrometry exist that fit somewhere in the ranking but that have not been observed by Gaia and are therefore missing in the table. One example is WISEA J085510.74-071442.5, which has a proper motion of 8.152 arcsec/yr, which would make its rank #3 in the above table. Please consult the "living" UltracoolSheet  for the current status of such objects.

Acknowledgement: we thank Neal McBurnett for raising the issue of the spurious entry HIP 67594.

Credits: ESA/Gaia/DPAC, Jos de Bruijne.

[Published: 13/05/2025]