Supermassive black hole just turned towards Earth: Should we be scared?

By Girish Linganna | First Published Apr 4, 2023, 12:47 PM IST

While it is highly unlikely that a black hole could directly affect Earth, its gravitational pull could indirectly impact our planet. Defence and Aerospace Analyst Girish Linganna analyses the space phenomenon

On March 30, social media and news websites were abuzz with the news that astronomers had observed a supermassive black hole deep inside a distant galaxy which had turned its gaze -- a beam of charged particles -- directly towards Earth. So, how scared should we be lest we get swallowed and 'spaghettified' by this giant black hole as so many stars that dared to venture close to such phenomena earlier?

A paper published recently in the monthly notices of the Royal Astronomical Society said an international team of astronomers investigating the galaxy PBC J2333.9-2343, located roughly 650 million light-years away, realized that it had experienced a spurt in growth since the last time they had observed it.

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Earlier, this distant galaxy had been classified as a 'radio galaxy' because of regions of radio emissions that extended well beyond the galaxy’s visible structure. The recent observations, however, showed that it was a totally different sort of galaxy, compelling astronomers to reclassify it as a 'giant radio galaxy'.

Researchers at Yale University used 1.3m-SMARTS optical telescope at the Penn State Neil Gehrels Swift Observatory and the German 100m-Radio Telescope Effelsberg at the Max Planck Institute for Radio Astronomy. They pointed infrared, optical, radio, X-ray, UV and Gamma-ray instruments to gather as much data from every spectrum of the galaxy as possible.

The astronomers' observations corroborated the belief that the black hole's orientation had changed to 90 degrees. Earlier, it had pointed into the plane of the sky, perpendicular to Earth. But now, it is like a spotlight glaring directly at us.

Earlier radio lobes, too, were not being fed by the black hole any longer but were visible as yet-luminous regions left over from past activity. That is consonant with jet direction change. But this black hole, in comparison with other radio galaxies, is super bright -- like staring into a galactic headlight.

As a result, the black hole received a new nomenclature: blazar -- a subgroup of black holes in the centre of a galaxy with a relativistic jet pointed directly at the astronomers behind the telescope. This is known as the active galactic nucleus (AGN). There’s nothing intrinsically different between blazars and other AGNs, except that they are better visible as they point our way.

The direction of the jet changed the classification of the galaxy, as well. As the beam is pointed our way, radio emissions are strongly accentuated from our standpoint. The radio flares burn more intensely -- strong enough to engulf emissions from the rest of the galaxy and outshine every other radio galaxy in proximity.

What Exactly is a Black Hole?

The name, 'Black', comes from the fact that nothing -- not even light -- can escape its gravity. They are massive in size, so they have very strong gravitational, attractive forces. Things with mass attract each other. And the more mass, the more gravity! Even though light travels fast, it is not fast enough to outpace the gravitational pull of a black hole.

But why are they called 'holes'? The term is, in reality, misleading! Although they may seem like holes in the sky as they do not produce light, a black hole is not empty. It is actually a huge amount of matter condensed into a single point -- known as a 'singularity'.

So, how do we get such a huge mass to come together at one point in space? Imagine a large star. Big stars burn up their fuel really fast because they have more gravity, which makes their centres hotter and denser. They can go through a lot more nuclear reactions and burn it all up really fast.

Jeremy Schnittman, a research astrophysicist at NASA, says, "They build up a big pile of ashes in the centre of the star. Those ashes are actually iron, which doesn’t facilitate nuclear burning. So, it doesn’t give off extra heat. It just sits there and gets bigger and bigger. Now, these two forces battle each other. One force is caused by whatever fuel is left to be burned, and another from the gravity of the iron pulling everything inward.

"Ultimately, that star runs out of heat and this pressure that holds up its centre. The gravity just grows bigger, the pressure stays… Until, finally, gravity wins out and everything just starts collapsing! At that moment, two things happen: Some portion of the star is ejected into space causing light shows that we call supernovae. The rest condenses into one point—the singularity."

How will Earth be impacted?

While it is highly unlikely that a black hole could directly affect Earth, its gravitational pull could indirectly impact our planet. The most-likely scenario for this to occur would be if a black hole were to move close to our solar system.

This could disrupt the orbits of planets and alter the gravitational pull of our Sun, potentially leading to changes in Earth’s orbit or rotation.

Another theoretical possibility is that a black hole could pass close enough to our solar system to cause intense cosmic radiation to bombard Earth. While this would cause widespread damage to the planet’s atmosphere and biosphere, it is highly unlikely that such an event could occur within the foreseeable future.

Are Black Holes necessary?

Despite the potential risks, black holes are also essential to the universe's functioning. They play a vital role in galaxy formation and help regulate the movement of matter in space. Without them, galaxies would not be able to form and the universe, as we know it, would not exist.

Researching black holes is essential for scientists seeking to better understand the universe’s fundamental workings. With newer technologies and telescopes available, we are now able to observe these mysterious objects in more detail than ever before, providing insights into their properties and behaviour.

In conclusion, while black holes are incredible and fascinating objects, they are highly unlikely to directly impact Earth due to their vast distances that separate us. However, it is vital to continue studying them to better understand their impact on the universe and our place in it.

It is a misconception that black holes consume celestial bodies such as stars, moons, and planets by moving around in space. The likelihood of Earth being pulled into a black hole is next to impossible as there are no black holes in close proximity to the solar system.

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