Upsilon Andromedae

system

Upsilon Andromedae (Titawin) is a yellow-white star a little hotter and larger than the Sun, 44 light-years away in Andromeda, and a milestone of exoplanet science: in 1999 it became the first ordinary (main-sequence) star found to host more than one planet. Three giant planets are known, and their orbits are steeply tilted relative to one another — a fossil of a violent dynamical past.

Open in 3D viewSee Upsilon Andromedae in the live, interactive 3D map

Key facts

Type

Sun-hotter star + 3 planets

Distance

44.0 light-years

Confirmed planets

First

Multi-planet main-sequence system (1999)

Science

Classification

Type: Single main-sequence system (F8V)
Central star: Upsilon Andromedae / Titawin — F8V (~6157 K, 1.3 M☉)

Planets

Confirmed planets: 3 · b (hot Jupiter), c, d — all giants
Notable: Outer orbits steeply mutually inclined
Masses: b a minimum mass; c & d true masses (astrometry)

Distance

Distance: 44.0 light-years · naked-eye (V 4.1)

How we know

Note: Three confirmed planets (NASA Exoplanet Archive, checked 2026-07-05). Planet b's mass is a radial-velocity minimum; c and d have true masses from astrometry. None transits, so radii are model estimates and no density is quoted. Map distance is symbolic; the real gap is 44.0 light-years.

Discovery & history

Method: Naked-eye star
Name: IAU name Titawin (old name of Tetouan, Morocco); Upsilon Andromedae.

Its hot Jupiter was found in 1996 and two more giants in 1999 — the first multi-planet system around a main-sequence star.

Images

Where to find it — in Andromeda, the Chained Princess (IAU constellation chart). To the eye it is a single point of light; no telescope has imaged its surface. — IAU / Sky & Telescope, R. Sinnott & R. Fienberg (CC BY 3.0) · Wikimedia Commons

Images from open archives · credit shown per image