Polaris vs sao Chức Nữ
Precession has handed the role of pole star back and forth between these two. Polaris holds it now, sitting at declination +89°, within a degree of the north celestial pole; Vega occupied the position some twelve thousand years ago and will do so again. In brightness they are not close. Vega shines at magnitude 0.03 against 1.97 for Polaris, near six times the light, largely because Vega lies 25.04 light-years away and Polaris 432.57 — a factor of seventeen. Intrinsically the order flips hard: Polaris carries an absolute magnitude of −3.64 to Vega's +0.60, making the F-type supergiant something like fifty times the more luminous star.
Property comparison
| Property | Polaris | sao Chức Nữ |
|---|---|---|
| Ký Hiệu | 1Alp UMi | 3Alp Lyr |
| Chòm Sao | N/A | Lyra |
| Phân Loại Quang Phổ | Class F — F-type (Yellow-White) | Class A — A-type (White) |
| Cấp Sao Biểu Kiến | +1.97 | +0.03 |
| Cấp Sao Tuyệt Đối | -3.64 | 0.60 |
| Khoảng Cách | 433 ly | 25.0 ly |
| Khối Lượng | N/A | N/A |
| Bán Kính | N/A | N/A |
| Nhiệt Độ | N/A | N/A |
| Độ Sáng | N/A | N/A |
Full data for each star: Polaris · sao Chức Nữ
Key differences
Key Differences
- ◆ Polaris is an F-type Cepheid variable supergiant; Vega is a stable A-type main-sequence star.
- ◆ Polaris is 431 light-years away; Vega is much closer at 25 light-years.
- ◆ Polaris sits near the north celestial pole and has guided navigators for centuries; Vega was the pole star ~14,000 years ago.
- ◆ Vega served as the original zero-magnitude reference for the photometric system.
- ◆ Polaris pulsates in brightness; Vega has a debris disk suggesting a forming planetary system.
When to Observe
Polaris
Polaris never sets from the northern hemisphere. At declination +89° it is circumpolar for every northern latitude, holding an almost fixed altitude equal to the observer's latitude, and it is invisible south of the equator.
sao Chức Nữ
Vega culminates at midnight in late June and dominates summer evenings. Its declination of +38° makes it circumpolar above about 52°N and still accessible from the northern tropics of the southern hemisphere.