When is the best time to observe Adara?

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

Where is Adara located in the sky?

Adara lies in the constellation Canis Major at right ascension 06h 59m and declination -28° 58′.

What telescope do I need to split Adara?

Splitting Adara requires an aperture of roughly 80 mm or larger — the components are separated by about 7.9″ at magnitudes near 1.5. The companion is about 6.0 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Adara — Double Star in Canis Major

HIP 33579; Epsilon Canis Majoris; 21 Canis Majoris

Magnitude 1.5^m DoubleStar Canis Major (CMa) Visible

Star Map + List + Plan

About Adara

Description

Adara (Epsilon Canis Majoris) is the second brightest star in Canis Major at magnitude 1.50, located about 430 light-years from Earth. It is a blue giant of spectral type B2Iab, about 11 times the mass of the Sun and roughly 38,000 times more luminous. Adara is one of the strongest sources of extreme ultraviolet radiation in the sky as seen from Earth.

Observing Tips

Adara sits at the hindquarters of Canis Major, forming part of the distinctive triangle of stars south of Sirius. Its blue-white color is evident through binoculars. Adara has a faint companion (magnitude 7.5) at about 7.5 arcseconds separation, resolvable in a small telescope. The star is visible from both hemispheres. Best observed from January through March.

History

The name Adara comes from the Arabic 'al-Adhara' meaning 'the maidens' or 'the virgins.' About 4.7 million years ago, Adara was the brightest star in Earth's sky, shining at magnitude -3.99 when it was only about 34 light-years away. Since then, its proper motion has carried it much farther from the Sun.

Fun Facts

Adara was once the brightest star in Earth's sky — it holds the record for the brightest apparent magnitude ever achieved by any star other than the Sun as seen from Earth's position, reaching nearly magnitude -4 about 4.7 million years ago. It is the strongest source of photons in the extreme ultraviolet range (504-912 Å) in the sky.

Observe

1Physical Properties

Magnitude 1.50

Spectral Type B1III giant

Star Color Blue (B-V -0.21)

Distance 405 ly

2Position & Identifiers

RA 06h 58m 37.5s

Dec -28° 58' 20.0"

Constellation Canis Major (CMa)

HR 2618

HIP 33579

HD 52089

SAO 172676

Bayer Epsilon

Flamsteed 21 CMa

Double Cat 5654

SIMBAD Wikipedia

3How easy to split?

Primary 1.5 mag Companion 7.5 mag Separation 7.9″

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Hard	Hard	Hard
150 mm Newton 150mm Newt.	Medium	Medium	Medium
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 Nov – Jan (peak: Dec)

5Multiple Star System

Separation 7.9″

Companion Mag 7.5

Position Angle 162°

Star Colors A: Blue

Discoverer CPO 7

Notes

Fixed sep.

Separation over time

Measured 1850 → 2008 (158 y)

Separation drift 7.7" → 7.9" (+0.20")

Rate +0.0013" / y

PA drift 161° → 162° (+1°, +0.006°/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.