Cold Saturn-mass planet HD 38973 b found orbiting a Sun-like star

Star system: HD 38973 | Distance from the Sun: 93.6 light years

HD 38973 is a nearby star similar to the Sun. Astronomers have discovered a planet, HD 38973 b, orbiting this star with a long period of about 2733 days, or roughly 7.5 years. The planet’s mass is estimated to be about a quarter that of Jupiter, placing it in the category of cold Saturns—planets with similar mass and temperature to Saturn in our solar system. The discovery was made using precise measurements of the star’s motion, which revealed the gravitational pull of the planet.

To further constrain the planet’s properties, the team used data from the Hipparcos and Gaia space missions, which track the positions and movements of stars. Although they did not detect a direct astrometric signal from the planet, the lack of such a signal helped set an upper limit on the planet’s mass. By combining the radial velocity and astrometric data, the researchers ruled out the possibility that the planet is much more massive than Saturn.

This study shows that even when a planet’s influence on its star’s position is too small to detect directly, combining different types of observations can provide strong constraints on its mass. HD 38973 b is a valuable addition to the small group of known cold Saturns and helps scientists understand the diversity of planetary systems around Sun-like stars.

Key findings
- HD 38973 b is a cold Saturn-mass planet orbiting a Sun-like star every 2733 days.
- The planet’s mass is about 0.24 times that of Jupiter.
- No astrometric signal was detected, but this helps set an upper mass limit.
- Combining radial velocity and astrometry provides robust constraints on planet mass.
- The discovery adds to our knowledge of cold Saturns in other planetary systems.

Scientific study

HD 38973 b -- a cold Saturn orbiting a Sun-like star (external link)