Pyxis

What is Pyxis?

Constellations· Spring evenings · three faint stars at the edge of the Milky Way. A mariner's compass that Lacaille placed near the mast of the old ship Argo. It has no bright star, but its three stars line up neatly, and the recurrent nova T Pyxidis is its best-known object. Look low in the south on a spring evening in the Sky view.

Where Pyxis is in your sky right now: https://nowsky.org/solar/sky?sel=con:Pyxis — location and time set automatically, no login.

Stars of the figure

The 1 brightest of the 2 stars used in the figure (1 lines). Lower magnitude means brighter.

Constellation basics

Figures are representative approximations. Source: compiled from NASA and IAU public data.

Frequently asked

When can I see Pyxis?

Mar–Apr evenings, low in the south; visible from Korea.

How do I find Pyxis?

just east of Puppis, a short line of stars south of Hydra's head.

What is the brightest star in Pyxis?

Alpha Pyxidis, magnitude 3.7.

Where is Pyxis in the sky right now?

Open the sky view for your location and time and it shows the position in the sky right now.

The compass that was nearly a mast

When Lacaille drew a compass here in the 1750s he meant to set a navigational instrument beside the neighbouring ship Argo. In 1844, however, John Herschel proposed making these stars the ship's mast instead, a constellation called Malus, on the grounds that a ship without a mast was odd. The proposal appeared briefly on charts, was not adopted, and in 1930 the International Astronomical Union confirmed Lacaille's compass as it was.

So the Argo is divided into keel, stern and sail with no mast, and in its place stands an instrument unrelated to the ship. The stars of Pyxis also received their own Bayer letters alpha, beta and gamma, unlike the other three pieces, which share the letters of the old Argo Navis. The short line of three stars low in the southern sky on spring evenings is a small example of how constellation names are decided and dropped.

The constellation in depth

Pyxis is one of fourteen constellations that Lacaille invented in the 1750s to honour the instruments of science. It occupies the spot that was once the mast of the ship Argo, so he chose a fitting object: a mariner's compass. Its shape is modest — alpha, beta and gamma Pyxidis in an almost straight line.

Its most famous object is the recurrent nova T Pyxidis, a white dwarf that pulls gas from a companion until the surface detonates. It has flared six times between 1890 and 2011. When the next outburst will come, and whether the star will eventually end as a supernova, are open questions. Its three main stars are all of the fourth magnitude and lie roughly 200 to 900 light-years away.

At a declination near −30° it is visible from Korea, low in the south on March and April evenings. Move east from Sirius, or south from the head of Hydra, and you reach a short row of faint stars. In the Sky view, set Seoul on a March night and look south to confirm its place. Turn on the constellation lines and the short row stands out at once. The whole figure fits in one binocular field.

Related

Figures are representative approximations. Simulated positions use J2000 mean elements.