When is the best time to observe Gomeisa?

Gomeisa is best observed from December through February, with peak visibility during January when it transits around midnight in the Northern Hemisphere.

Where is Gomeisa located in the sky?

Gomeisa lies in the constellation Canis Minor at right ascension 07h 27m and declination +08° 17′.

What telescope do I need to split Gomeisa?

Splitting Gomeisa requires an aperture of roughly 60 mm or larger — the components are separated by about 138.6″ at magnitudes near 2.9. The companion is about 8.7 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Gomeisa — Double Star in Canis Minor

HIP 36188; Beta Canis Minoris; 3 Canis Minoris

DoubleStar Canis Minor (CMi) Visible

Star Map + List + Plan

About Gomeisa

Description

Gomeisa is a blue-white main-sequence star of spectral type B8Ve at magnitude 2.90, the second brightest star in Canis Minor. Located about 162 light-years from Earth, it has a luminosity of roughly 250 times solar. It is a Be star, rapidly rotating and occasionally ejecting gas into a circumstellar disk.

Observing Tips

Gomeisa lies about 4 degrees northwest of brilliant Procyon in the small constellation Canis Minor. It is a blue-white star providing a color contrast with the yellow-white Procyon. Canis Minor contains only these two bright stars. Best observed January through April.

History

The name Gomeisa comes from the Arabic 'al-ghumaisa,' meaning 'the bleary-eyed one.' In Arabic tradition, Gomeisa and Procyon were 'the two sisters' who wept for their brother (Sirius) who had crossed the Milky Way.

Fun Facts

Canis Minor is one of the smallest constellations, and essentially consists of just Procyon and Gomeisa — a contrast between a nearby yellow-white star and a distant hot blue star that happen to lie in almost the same direction from Earth.

Observe

1Physical Properties

Magnitude 2.90

Range 2.89 - 2.9

Period 7.4 hours

Variable Type Slowly Pulsating Be Star

Spectral Type B8Ve

Star Color Blue-white (B-V -0.09)

Distance 162 ly

2Position & Identifiers

RA 07h 27m 09.0s

Dec +08° 17' 22.0"

Constellation Canis Minor (CMi)

HR 2845

HIP 36188

HD 58715

Bayer Beta

Flamsteed 3 CMi

Variable ID Bet CMi

SIMBAD Wikipedia

3How easy to split?

Primary 2.9 mag Companion 11.6 mag Separation 138.6″

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Hard	V. hard+	V. hard
150 mm Newton 150mm Newt.	Medium	Medium	Hard+
Celestron C8 (203 mm SCT) C8 203mm	Medium+	Medium	Medium

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

Set a location in User Settings to see visibility data.

Best season Dec – Feb (peak: Jan)

5Light Curve

6Multiple Star System Quintuple E,I,J: optical

Components 5 (quintuple)

Component IDs AE

Separation 138.6″

Companion Mag 11.6

Position Angle 315°

Star Colors A: Blue-white

Discoverer BUP 101

Separation over time

Measured 1879 → 2013 (134 y)

Separation drift 139.0" → 138.6" (-0.40")

Rate -0.0030" / y

PA drift 310° → 315° (+5°, +0.037°/y)

Essentially fixed on human timescales — the same view your grandchildren will see.

Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.