Image: The lenticular galaxy NGC 404, also known as Mirach’s Ghost, as imaged with FT North – note the severe “light pollution” caused by the nearby very bright star Mirach.

Imaging by Pete Williamson:

“NGC 404 is a lenticular galaxy (which means it is disk shaped like a spiral galaxy, but does not have spiral arms) at a distance of 10 million light years. It has always been a very challenging object to observe, hence the name of Mirach’s Ghost, as it lies very close to the 2nd magnitude star Mirach in Andromeda, a target of mine since I was a teenage observational astronomer.

One of my main interests in visual astronomy was to observe as many faint difficult objects and record them as I well as I could. I first saw it from Whittington Shropshire using a 14” Dobsonian in very dark skies – this was the last time I saw it visually as the skies deteriorated due to light pollution, plus I downsized the telescope.

In this image I used the Faulkes Telescope North 2m telescope at the Halaekala Observatory to take 60 second exposures in the B, V and R filters. Much of the star light was processed out using the Pixinsight software, to reveal the galaxy NGC404 and other faint background galaxies.”

The research angle:

Mirach’s Ghost has recently become an area of intense interest for astronomers, and a research team led by Cardiff University scientists say they are closer to understanding how a supermassive black hole (SMBH) is born thanks to a new technique that has enabled them to zoom in on one of these enigmatic cosmic objects in unprecedented detail.

In a study published recently, the Cardiff-led team has pushed the boundaries, revealing one of the lowest-mass SMBHs ever observed at the centre of a nearby galaxy, weighing less than one million times the mass of our sun.

The SMBH lives in “Mirach’s Ghost”, and the findings were made using a new technique with the Atacama Large Millimeter/submillimeter Array (ALMA), a state-of-the-art telescope situated high on the Chajnantor plateau in the Chilean Andes that is used to study light from some of the coldest objects in the Universe.

“The SMBH in Mirach’s Ghost appears to have a mass within the range predicted by ‘direct collapse’ models,” said Dr Tim Davis from Cardiff University’s School of Physics and Astronomy.

“We know it is currently active and swallowing gas, so some of the more extreme ‘direct collapse’ models that only make very massive SMBHs cannot be true.”
An SMBH is the largest type of black hole that can be hundreds of thousands, if not billions, of times the mass of the Sun.

It is believed that nearly all large galaxies, such as our own Milky Way, contain an SMBH located at its centre.

“SMBHs have also been found in very distant galaxies as they appeared just a few hundred million years after the big bang”, said Dr Marc Sarzi, a member of Dr. Davis’ team from the Armagh Observatory & Planetarium.

“This suggest that at least some SMBHs could have grown very massive in a very short time, which is hard to explain according to models for the formation and evolution of galaxies.”

“All black holes grow as they swallow gas clouds and disrupt stars that venture too close to them, but some have more active lives than others.”

“Looking for the smallest SMBHs in nearby galaxies could therefore help us reveal how SMBHs start off,” continued Dr. Sarzi.

In their study, the international team used brand new techniques to zoom further into the heart of a small nearby galaxy, called NGC404, than ever before, allowing them to observe the swirling gas clouds that surrounded the SMBH at its centre.

The ALMA telescope enabled the team to resolve the gas clouds in the heart of the galaxy, revealing details only 1.5 light years across, making this one of the highest resolution maps of gas ever made of another galaxy.

Being able to observe this galaxy with such high resolution enabled the team to overcome a decade’s worth of conflicting results and reveal the true nature of the SMBH at the galaxy’s centre.

“Our study demonstrates that with this new technique we can really begin to explore both the properties and origins of these mysterious objects,” continued Dr Davis.

“If there is a minimum mass for a supermassive black hole, we haven’t found it yet.”