When is the best time to observe Mahasim?

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

Where is Mahasim located in the sky?

Mahasim lies in the constellation Auriga at right ascension 05h 60m and declination +37° 13′.

What telescope do I need to split Mahasim?

Splitting Mahasim requires an aperture of roughly 100 mm or larger — the components are separated by about 3.7″ at magnitudes near 2.6. The companion is about 4.6 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Mahasim — Double Star in Auriga

Theta Aur

Observable Double Star Excellent (63/100)

Sep: 3.7", Companion: mag 7.2

Magnitude 2.6^m DoubleStar Auriga (Aur) Visible

Star Map + List + Plan

About Mahasim

Description

Theta Aurigae is a chemically peculiar white star of spectral type A0pSi at magnitude 2.62 in Auriga. Located about 166 light-years from Earth, it is an Alpha2 Canum Venaticorum variable — a magnetic star with silicon-rich patches that cause slight brightness variations as it rotates. It is a close binary system.

Observing Tips

Theta Aur lies in the southern part of the Auriga pentagon, between Capella and Elnath. It helps define the constellation's shape but is not one of the 'Kids' stars. Best observed November through April when Auriga is high in the winter sky.

History

Theta Aurigae has no widely used traditional name. Its magnetic and chemically peculiar nature makes it a member of the same stellar class as Alioth (Epsilon UMa) and Cor Caroli (Alpha CVn).

Fun Facts

Theta Aur's strong magnetic field concentrates silicon atoms into patches on its surface. As the star rotates, these patches move in and out of view, causing small brightness variations — a stellar version of starspots, but driven by magnetic chemistry rather than temperature.

Observe

1Physical Properties

Magnitude 2.62

Range 2.63 - 2.66

Period 3.6 days

Variable Type Alpha2 CVn (Magnetic Rotating)

Spectral Type B9IV subgiant

Star Color Blue-white (B-V -0.08)

Distance 166 ly

2Position & Identifiers

RA 05h 59m 43.3s

Dec +37° 12' 45.0"

Constellation Auriga (Aur)

HR 2095

HIP 28380

HD 40312

SAO 58636

Bayer Theta

Flamsteed 37 Aur

Variable ID The Aur

Double Cat 4566

SIMBAD Wikipedia

3How easy to split?

Primary 2.6 mag Companion 7.2 mag Separation 3.7″

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

5Light Curve

6Multiple Star System Quadruple C,D: optical

Components 4 (quadruple)

Component IDs AB

Separation 3.7″

Companion Mag 7.2

Position Angle 302°

Star Colors A: Blue-white B: Yellow

Discoverer STT 545

Notes

AB binary , combined mag., colors. B is 7.2v G2V. C, 11v at 49" optical.

Separation over time

Measured 1871 → 2022 (151 y)

Separation drift 2.1" → 3.7" (+1.60")

Rate +0.0106" / y

PA drift 7° → 302° (-65°, -0.430°/y)

Slow change over generations — observable in lifetime comparisons.

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.