NGC 4945

In the constellation of the Centaur we see NGC 4945 at a distance of only 17 million light years. Like our Milky Way, it has large swirling spiral arms and a bar-shaped central region. However, it differs as a so-called Seyfert galaxy. This is a special form of active galaxy:

In the core area there is a super-heavy black hole of many millions of solar masses. There are plenty of stars, gas and dust in its vicinity, which are extremely heated and therefore emit high-energy radiation. In
contrast to this, our Milky Way is currently a so-called “quiet galaxy”; its black hole simply has too little food.

NGC 4945 has another special feature: natural Wassetoff
masers have been discovered. A maser generates so-called coherent electromagnetic waves that cover a frequency range of 100 kHz to 100 GHz, corresponding to a wavelength range of kilometers to millimeters. Such devices were developed in the 1950s and 1960s, even before lasers, with the aim of being able to build noise-free amplifiers. And then a natural source of such a maser was discovered in NGC 4945.

The apparent extent of the galaxy in the image corresponds to about 2/3 of the full moon and it is easily recognizable with standard binoculars if you are in the southern hemisphere or at least no further north than 10° from the equator somewhere under a light-pollution-free
evening sky.

This photo was published as the “Astronomy Picture of the Day” by NASA.

Coordinates:
RA: 13h 05m 27,477s
DC: -49° 28′ 05,57″

Exposure time:
45 hours

Award:
NASA (APOD)