The Big Dipper in Spectroscopy - My First Steps in Spectroscopy

The project had tempted me for a long time!...
Through the AAVSO, I had acquired an SA-200 filter and had already started some experiments…

But a real project beckoned… A rumor had it that some of the seven stars of the Big Dipper originated from the same nebula.
There must therefore be similarities between them.

This well-known circumpolar constellation, shaped like a saucepan, primarily comprises seven stars:  Dubhe (α UMa), Merak (β UMa), Phecda (γ UMa), Megrez (δ UMa), Alioth (ε UMa), Mizar (ζ UMa) et Alkaid (η UMa).

Photo OMSJ

Other names:
Eta Ursae Majoris, Eta of the Great Bear,
Benetnash, 85 Ursae Majoris, HD 120315,
H.R. 5191.

AD: 13h 48m 15s
DEC: +49° 13' 27"
Circumpolar object
Type V, therefore from the main series
101 al
Type Spectral BS: B3V

MIZAR

Other names:
Zeta Ursae Majoris, 79 Ursae Majoris,
HD 116656, HR 5054.

AD: 13h 24m 39s
DEC: +54° 49' 55"
Circumpolar object
Type V, therefore from the main series
79 al
Multiple Star
Spectral type: A1VpSrSi

Mizar... I find this star fascinating...
It even serves as a visual test.
For most eyes, we only see a single
star. But as we magnify, either with binoculars or a telescope, we see three stars, then
four and five stars.

During data acquisition with the SA-200,
since this filter doesn't have a high resolving power, it's clear that Mizar dominated with its magnitude of 3.85. Alcor is also an A-type star. To go further, the experiment will need to be repeated with a slit spectroscope with higher resolution.

 Photo OMSJ  

Alioth

Other names:
epsilon Ursae Majoris, 77 Ursae Majori,
HD 112185, HR 4905

AD: 12h 54m 49s
DEC: +55° 51' 45"
Circumpolar object
81 al

*Variable
Spectral Type: A0pCr – A1IV

* From Wikipedia: Alpha2 Canum Venaticorum Variable Star

(Redirected from Alpha2 Canum Venaticorum Variable)

In astronomy, an Alpha2 Canum Venaticorum variable star is a main-sequence variable star of spectral type B8p to A7p that exhibits a strong magnetic field and spectral lines in silicon, strontium, and chromium.
Its luminosity typically varies between 0.01 and 0.1 magnitudes over a period of 0.5 to 160 days.

The prototype and best-known of these variables is Cor Caroli (α² CVn), which fluctuates by 0.1 magnitudes over a period of 5.47 days.

(https://fr.wikipedia.org/wiki/%C3%89toile_variable_de_type_Alpha2_Canum_Venaticorum)

*However, the star Alioth is not registered as a variable star in the AAVSO database.

Megrez (Kaffa)

Other names:
delta Ursae Majoris, 69 Ursae Majoris
HD 106591, HR 4660

AD: 12h 16m 18s
DEC: +56° 55' 58"
Circumpolar object
Type V, therefore from the main series
81 al
*Multiple Star
Spectral BS type: A3V – A2Vn

*https://fr.wikipedia.org/wiki/Gamma_Ursae_Majoris

Phecda

Other names:
Gamma Ursae Majoris, 64 Ursae Majoris
HD 103287, HR 4554

AD: 11h 54m 46s
DEC: +53° 35' 41"
Circumpolar object
Type V, therefore from the main series
85 al
BS Spectral Type: A0Ve, A1IV

Dubhe

Other names:
Alpha Ursae Majoris, 50 Ursae Majoris
HD 95689, HR 4301

AD: 11h 04m 50s
DEC: +61° 39' 13"
Circumpolar object
Type IIIa,
so in the series of giant stars
125 al
8Multiple Star
Spectral type BS: K0IIIa

It is a multiple star; Dubhe A has evolved into a helium-burning star, Dubhe B, a main-sequence star, orbits at a distance of 20 AU, and Dubhe C, at a distance of 8000 AU.
* (https://fr.wikipedia.org/wiki/Alpha_Ursae_Majoris)

Merak

Other names:
Beta Ursae Majoris, 48 ​​Ursae Majoris
HD 95418, HR 4295

AD: 11h 02m 55s
DEC: +56° 17' 08"
Circumpolar object - Transit: 05h42m
Type V, therefore from the main series
79 al
BS spectral type: A1V, A1IVspSr

So we have five stars that are relatively close together and two that are further apart.

Here's the plan :

* Plan derived from « Petit guide du ciel » de Bernard Pellequer – Édition du Seuil - 1990