ดาวซิริอุส vs ดาวเวกา
Both are A-type stars, and both are close: Sirius at 8.60 light-years, Vega at 25.04. What distinguishes them in the sky is that factor of 2.9 in distance. Sirius shines at magnitude −1.44 and Vega at 0.03, a 1.47-magnitude gap worth about 3.9 times the light. Their absolute magnitudes tell a quieter story — +1.45 for Sirius against +0.60 for Vega — so Vega is in fact the more luminous of the pair by roughly a factor of two, and the brightest star in the sky owes its rank almost entirely to proximity. Vega's magnitude near zero is no coincidence: it long served as the reference point for the visual magnitude scale.
Property comparison
| Property | ดาวซิริอุส | ดาวเวกา |
|---|---|---|
| ชื่อเรียก | 9Alp CMa | 3Alp Lyr |
| กลุ่มดาว | Canis Major | Lyra |
| ประเภทสเปกตรัม | Class A — A-type (White) | Class A — A-type (White) |
| โชติมาตรปรากฏ | -1.44 | +0.03 |
| โชติมาตรสัมบูรณ์ | 1.45 | 0.60 |
| ระยะทาง | 8.6 ly | 25.0 ly |
| มวล | N/A | N/A |
| รัศมี | N/A | N/A |
| อุณหภูมิ | N/A | N/A |
| ความส่องสว่าง | N/A | N/A |
Full data for each star: ดาวซิริอุส · ดาวเวกา
Key differences
Key Differences
- ◆ Both are brilliant white A-type stars and among the most prominent in the northern sky.
- ◆ Sirius is the brightest star overall at magnitude −1.46; Vega is the fifth-brightest at magnitude 0.03.
- ◆ Sirius is 8.6 light-years away; Vega is 25 light-years from the Sun.
- ◆ Vega was the original zero-point for stellar magnitude; Sirius sets the scale of brightness.
- ◆ Sirius has a white dwarf companion; Vega has a prominent debris disk but no known companion.
When to Observe
ดาวซิริอุส
Sirius is a winter star, culminating at midnight around 1 January and best placed on evenings from January to March. Its declination of −16° keeps it low for northern observers but visible.
ดาวเวกา
Vega culminates at midnight at the end of June and rules the summer evening sky from June to September. At declination +38° it passes near the zenith across Europe and the northern United States, and is circumpolar above about 52°N.