WASHINGTON: A reddish-colored cigar-shaped interstellar object called Oumuamua that is tumbling through our solar system may be wreckage from a planet ripped apart when it roamed too close to the faraway star it once orbited, according to researchers.

Scientists have been puzzled by the origin and nature of Oumuamua since its discovery in 2017, with some even proposing it may be an alien spacecraft. Astronomers Yun Zhang and Doug Lin, in research published this week, said computer simulations indicated it was a remnant of a planet or planetary building block annihilated by a star’s “tidal forces.”

Oumuamua, the first object from another star system found passing through our solar system, is about a quarter-mile (400 meters) long. Its elongated shape, curious motion and dry appearance — for instance, lacking a tail of dust and gases — indicated it is not an ordinary comet or asteroid.

When a smaller body passes near a much bigger one, tidal forces exerted by the larger body can shred the smaller one. This is what happened when a comet called Shoem­akerLevy 9 journeyed too close to Jupiter in 1992.

Biggest explosion

Scientists have observed the biggest stellar explosion ever detected, the violent death of a huge star up to 100 times more massive than our sun in a faraway galaxy.

The supernova, releasing twice as much energy as any other stellar explosion observed to date, occurred about 4.6 billion light years from Earth in a relatively small galaxy, scientists said. A light year is the distance light travels in a year, which is about 9.5 trillion kilometres.

It might represent, they added, a type of supernova that until now has only been theorised.

Astrophysicist Matt Nicholl of the University of Birmingham, England, said two very massive stars — each about 50 times the sun’s mass — may have merged to make one extremely massive star roughly 1,000 years before the explosion. They had been part of what is called a binary system with two stars gravitationally bound to each other.

The merged star exploded in a supernova, formally named SN2016aps, inside a very dense and hydrogen-rich envelope.

“We found that the supernova was able to become so bright because of a powerful collision between the debris ejected by the explosion and a shell of gas shaken off by the star a few years earlier,” said Nicholl, lead author of the study published this week in the journal Nature Astronomy.

Stars die in different ways depending on their size and other properties. When a massive star — more than eight times the mass of our sun — uses up its fuel, it cools off and its core collapses, triggering shock waves that cause its outer layer to explode so violently that it can outshine entire galaxies.

The researchers, who observed the explosion for two years until it diminished to one percent of its maximum brightness, said it may have been an example of an extremely rare “pulsational pair-instability” supernova.

“Pulsational pair-instability is when very massive stars undergo pulsations which eject material away from the star,” said study co-author Peter Blanchard, a postdoctoral fellow in astrophysics at Northwestern University in Illinois. “This discovery shows that there are many exciting and new phenomena left to be uncovered in the universe,” Blanchard added.

Very massive stars like this one were probably more common early in the universe’s history, Nicholl said.

Published in Dawn, April 15th, 2020