Spectral type: M9 (Red dwarf, coolest)
Surface temperature in the range: 2,400–3,700 K
IR – Infrared wave source
Stars M class are most common. About 76% of the main sequence stars in the spectral band of the Sun (class G) are class M stars (red dwarfs), their brightness is so low, that it is impossible to see them with the naked eye, except under exceptional conditions.
The brightest known M class main sequence star is M0V Lacaille 8760, with magnitude 6.7 (the limiting magnitude for typical naked-eye visibility under good conditions is typically quoted as 6.5). So, it’s very unlikely that any brighter example of a class M star, will occurs anytime soon. But we can’t this completely ruled out.
As you can see in the example photo, with a telescope with a focal length of 420 [mm], brightness F2.8 and a sensitive RGB camera, by exposing a selected area of the sky long enough, you can register stars of the spectral type M (coolest red dwarfs) with very low brightness (15.35 mag) with a very clear presence in the entire frame.
It’s worth noting that red dwarfs burn out very slowly, which means they can be very, very old compared to other types of stars.
ASAS 053739-0146.3 / USNOA2 0825-01610019 – Gwiazda zmienna typu Mira Cet
Own study based on sources:
- Equipment: ATIK Horizon, Hypergraph TS 420mm f/2,8 OTA PH6, iOptron CEM25p with small self made tuning,
- Composition: APP,
- Processing: APP + RT + GIMP + add-ons (Linux),
- Lights: 170 x 60[s] (2h 50min.),
- Calibration frames: Flats, Bias, Darks