PZ Telescopii

PZ Telescopii, also known as HD 174429 or simply PZ Tel, is a young star in the constellation Telescopium. Based on parallax measurements, it is located at a distance of 154 light-years from the Sun. The star is drifting closer with a radial velocity of −4 km/s. It is too faint to be visible to the naked eye and is classified as a BY Draconis variable that ranges in apparent visual magnitude from 8.33 down to 8.63 over a period of 0.94088 days. It is one of the closest and hence brightest pre-main-sequence stars to Earth.

PZ Telescopii has an effective surface temperature of around 5,338 K (the Sun has an approximate surface temperature of 5,778 K), a mass around 1.13 times, and diameter 1.23 times that of the Sun. The star has a high rate of spin, showing a projected rotational velocity of 69 km/s and a rotation period of 0.943 days. It is radiating about the same luminosity as the Sun. PZ Telescopii was originally considered to be a member of the Beta Pictoris moving group; however in a 2012 paper, James Jenkins of Universidad de Chile and colleagues used three methods to calculate its age and came up with a figure of around 24 million years—significantly older than the 12 million years of the association.

This star has an orbiting debris disk calculated to span from a radius of 35 to 165 astronomical units (AU), as well as a substellar companion with about 36 times the mass of Jupiter orbiting at a distance of about 16 AU, discovered in 2009. The companion, currently known as PZ Tel B, is thought to be a brown dwarf; however it is possible (though very unlikely) that it is an extremely large Jupiter-like planet, in which case it would be PZ Tel b, and the first such planet to be directly imaged. Preliminary orbital elements from 2016 give a best fit orbital period of 622.2 years with an eccentricity of 0.755.

The mass and orbit of this companion were updated in 2023 based on Hipparcos and Gaia astrometry, finding a somewhat lower mass, and an edge-on orbit that is eccentric but less so than previous results. It is now included in the NASA Exoplanet Archive since its nominal mass of is below their upper limit of, although the margin of error is large enough that it is still possible that the mass exceeds.