The Mysterious Explosion Called "The Cow"

On June 16, 2018 there was an unusual flash in the sky which puzzled astronomers around the world. The flash event was called AT2018cow and has been nicknamed “The Cow,” and scientists have been debating its source since then.

The site of the explosion was soon traced to a star-forming galaxy called CGCG 137-068, roughly 200 million light years away in the constellation Hercules.
It was an incredibly luminous event, brighter than almost any supernova we've ever seen before.
The event appeared and faded away very quickly, that existing supernova models can't properly explain it.
With the race on to determine exactly what sparked The Cow's intense flare, astronomers turned to other sources of data in an effort to analyse the glow of the explosion's aftermath.

Recently we come up with two competing theories of what caused it.

The first theory is that the flash came from a white dwarf being ripped apart by a black hole. A white dwarf could be pulled apart in a “tidal disruption event,” when it passes close enough to a black hole to be affected by its gravity, similar to the way that the Earth’s ocean tides are created by the gravity of the Moon.

The second theory is that the event was created by a supernova. When a star dies, it explodes in an event called a supernova and it leaves behind either a black hole or very dense core called a neutron star. The research team used high-energy X-ray data to show that the event had characteristics similar to a black hole or neutron star consuming material, and based on what we saw in other wavelengths, most probably this was a special case and that we may had seen for the first time the creation of a black hole in real time.

For now, debate will continue over which theory is correct.Ongoing and future observations may eventually be able to see what, if anything, remains from this mysterious explosion.

Phedias Hadjicharalambous.
Cyprus AstronomyOrganisation


"The Cow event" as seen in these three images.
Left: The Sloan Digital Sky Survey in New Mexico observed the host galaxy Z 137-068 in 2003, and the Cow nowhere in sight. (The green circle indicates the location where the Cow eventually appeared).

Center: The Liverpool Telescope in Spain's Canary Islands saw the Cow very close to the event's peak brightness on June 20, 2018, when it was much brighter than its host galaxy.

Right: The William Herschel Telescope, also in the Canary Islands, took a high-resolution image of the Cow nearly a month after it reached peak brightness, as it faded and the host galaxy came back into view