NGC 404

'NGC 404' is a small galaxy visible in amateur telescopes near the star Mirach in the constellation Andromeda. It was discovered by William Herschel in 1784.
The galaxy is small lenticular galaxy. It is located around 10,300,000 light-years away, just outside the Local Group but does not appear gravitationally bound to it. It is notable for being within 7 arc-minutes to Mirach in the night sky, making it very difficult to observe or photograph, granting it the nickname "Mirach's Ghost".

Contents

LINER emission

Distance measurements

External links

Notes

References

LINER emission

NGC 404 contains a low-ionization nuclear emission-line region (LINER), a type of region that is characterized by spectral line emission from weakly ionized atoms.^[1]

Distance measurements

At least two techniques have been used to measure distances to NGC 404. The infrared surface brightness fluctuations distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of their bulges. The distance measured to NGC 404 using this technique in 2003 is 9.9 ± 0.5 Mly (3.03 ± 0.15 Mpc).
However, NGC 404 is close enough that red supergiants can be imaged as individual stars. The light from these stars and knowledge of how they should compare to nearby stars within the Milky Way galaxy allows for direct measurement of the distance to the galaxy. This method is referred to as the tip of the red giant branch (TRGB) method. The estimated distance to NGC 404 using this technique is 10.0 ± 1.2 Mly (3.1 ± 0.4 Mpc). Averaged together, these distance measurements give a distance estimate of 10.0 ± 0.7 Mly (3.07 ± 0.21 Mpc).

External links

★ Encyclopedia of Astrobiology, Astronomy & Spaceflight Entry

★ Curdridge Observatory article

Notes

1. average(3.03 ± 0.15, 3.1 ± 0.4) = ((3.03 + 3.1) / 2) ± ((0.15² + 0.4²)^0.5 / 2) = 3.07 ± 0.21

References

1.