NGC 4845: Hubble Space Telescope Sees Large Spiral Galaxy

NGC 4845, otherwise known as LEDA 44392 or UGC 8078, is an 11th magnitude spiral galaxy in the constellation of Virgo. It is 58.8 million light-years away from us. The galaxy was originally discovered by the German-born British astronomer William Herschel in 1786.

According to astronomers, NGC 4845 hosts a supermassive black hole in its center. The presence of a black hole in a distant galaxy like this one can be inferred from its effect on the galaxy’s innermost stars; these stars experience a strong gravitational pull from the black hole and whizz around the galaxy’s center much faster than otherwise.

image_3542e-NGC-4845

From investigating the motion of these central stars, astronomers can estimate the mass of the central black hole – for NGC 4845 this is estimated to be hundreds of thousands times heavier than the Sun. This same technique was also used to discover the supermassive black hole at the center of our own Milky Way Galaxy – Sagittarius A* – which hits some 4 million solar masses.

In 2013 European astronomers were observing another galaxy when they noticed an energetic flare from the NGC 4845’s core. The flare came from the supermassive black hole tearing up and feeding off an object of 14 – 30 Jupiter masses. A brown dwarf or a so-called super-Jupiter exoplanet simply strayed too close and was devoured by the hungry black hole.

“The observation was completely unexpected, from a galaxy that has been quiet for at least 20-30 years,” the astronomers said.

This image includes optical and infrared observations from Hubble’s Wide Field Planetary Camera 2 (WFPC2).

 

Five Supermassive Black Holes discovered

Astronomers have found evidence for a large population of hidden supermassive black holes in the Universe.

Using NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) satellite observatory, the team of international scientists detected the high energy X-rays from five supermassive black holes previously clouded from direct view by dust and gas.


 

x-default

“An illustration of the NuSTAR satellite observatory in orbit. The unique 10 metre long mast allows NuSTAR to focus high energy X-rays. Credit: NASA/JPL-Caltech.”


 

The research, led by astronomers at Durham University, UK, supports the theory that potentially millions more supermassive black holes exist in the Universe, but are hidden from view.

The findings were presented today at the Royal Astronomical Society’s National Astronomy Meeting, at Venue Cymru, in Llandudno, Wales (Monday 6 July).

The scientists pointed NuSTAR at nine candidate hidden supermassive black holes that were thought to be extremely active at the centre of galaxies, but where the full extent of this activity was potentially obscured from view.

High-energy x-rays found for five of the black holes confirmed that they had been hidden by dust and gas. The five were much brighter and more active than previously thought as they rapidly feasted on surrounding material and emitted large amounts of radiation.

Such observations were not possible before NuSTAR, which launched in 2012 and is able to detect much higher energy x-rays than previous satellite observatories.


 

Hubble_NuSTAR_Durham_small

“A Hubble Space Telescope colour image of one of the nine galaxies targeted by NuSTAR. The high energy X-rays detected by NuSTAR revealed the presence of an extremely active supermassive black hole at the galaxy centre, deeply buried under a blanket of gas and dust. Credit: Hubble Legacy Archive, NASA, ESA.”


 

 Lead author George Lansbury, a postgraduate student in the Centre for Extragalactic Astronomy, at Durham University, said: “For a long time we have known about supermassive black holes that are not obscured by dust and gas, but we suspected that many more were hidden from our view.

“Thanks to NuSTAR for the first time we have been able to clearly see these hidden monsters that are predicted to be there, but have previously been elusive because of their ‘buried’ state.

“Although we have only detected five of these hidden supermassive black holes, when we extrapolate our results across the whole Universe then the predicted numbers are huge and in agreement with what we would expect to see.”

Daniel Stern, the project scientist for NuSTAR at NASA’s Jet Propulsion Laboratory in Pasadena, California, added: “High-energy X-rays are more penetrating than low-energy X-rays, so we can see deeper into the gas burying the black holes. NuSTAR allows us to see how big the hidden monsters are and is helping us learn why only some black holes appear obscured.”

The research was funded by the Science and Technology Facilities Council (STFC) and has been accepted for publication in The Astrophysical Journal.


 

AGN_artist_Durham_small

“An artist’s illustration of a supermassive black hole, actively feasting on its surroundings. The central black hole is hidden from direct view by a thick layer of encircling gas and dust. Credit: NASA/ESA.”


Credits: Earthsky.org & ras.org.uk