NGC 4395

NGC 4395 is an unbarred spiral galaxy of some 55 thousand light-years across that lies around 15 million light-years away from Earth in the northern constellation of Canes Venatici, while it is receding from us at about 319 kilometers per second.

It is a chaotic, low surface brightness galaxy with a center of no more than two light-years across - less than half the distance from our Sun to the nearest star. The galaxy is dominated by several bright emission nebulae (HII regions) and has an active galactic nucleus, which gives off prodigious amounts of energy largely in the form of high-energy x-rays and gamma rays, which classifies NGC 4395 as a Seyfert galaxy.

The centers of Seyfert galaxies usually contain supermassive black holes with masses between 10 and 100 million solar masses.

However, NGC 4395 is notable for containing one of the smallest supermassive black holes ever discovered, with an accurately-determined mass. The central black hole has a mass of “only” 300,000 solar masses, which would make it a so-called “intermediate-mass black hole”.

While most galaxies are disk-shaped with a bulge in the middle, NGC 4395 is essentially flat; it has no central bulge. And this unusual shape may be linked to the size of the black hole: the current theory holds the black hole might have already “eaten” all the stars in the center of the galaxy. This would explain why the black hole doesn’t seem to be growing as well as the galaxy’s odd shape.

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