Meet the 'zombie star' that survived a supernova blast

Published on Jun 29, 2022 05:06 AM IST
The star at issue, observed with the Hubble Space Telescope, is a kind known as a white dwarf, an incredibly dense object with about the mass of the sun crammed into the size of Earth.
There are various types of supernovae depending on the size and composition of the star and the power of the blast.(REUTERS)
There are various types of supernovae depending on the size and composition of the star and the power of the blast.(REUTERS)
Reuters |

Astronomers have observed in a relatively nearby galaxy a star that not only survived what ordinarily should have been certain death - a stellar explosion called a supernova - but emerged from it brighter than before the blast.

Meet the "zombie star."

The star at issue, observed with the Hubble Space Telescope, is a kind known as a white dwarf, an incredibly dense object with about the mass of the sun crammed into the size of Earth. A white dwarf is the remaining core of a star that blew off a lot of its material at the end of its life cycle, as our sun is expected to do about 5 billion years from now.

This white dwarf is gravitationally locked in orbit with another star - a pairing called a binary system - and with its strong gravitational pull siphoned off and incorporated a good deal of material from this unfortunate companion.

That is where the trouble started. In doing so, the white dwarf reached a mass threshold - about 1.4 times that of the sun - that caused thermonuclear reactions in its core that made it detonate in a supernova, an event that should have killed it.

"We were quite surprised that the star itself had not been destroyed but had actually survived and is brighter than before it exploded," said Curtis McCully, a senior astrodata scientist at California-based Las Cumbres Observatory, lead author of the research published this month in the Astrophysical Journal.

"During the explosion, radioactive material was produced. This is what powers the brightness of the supernova. Some of this material was left over in the surviving remnant star and acted as fuel to heat the remnant," McCully added.

This white dwarf resides in a spiral galaxy called NGC 1309, about three quarters the size of our Milky Way. Like the Milky Way, NGC 1309 resembles a spinning pinwheel when viewed from above or below. The white dwarf is located 108 million light years from Earth. A light year is the distance light travels in a year - 5.9 trillion miles (9.5 trillion km).

There are various types of supernovae depending on the size and composition of the star and the power of the blast.

This star is helping scientists better understand what are called "type Iax" supernovae. In these, a white dwarf experiences runaway nuclear fusion of carbon and oxygen after gaining matter relatively quickly, as this one did by stealing from its companion. But the explosion does not destroy the white dwarf, leaving behind an "undead" remnant.

"We have called these objects 'zombie stars' for this very reason. They died but not quite. Early on, many of the simulations of supernovae performed by scientists fizzled out before they were able to blow up the whole white dwarf star. It's exciting to think that was telling us something about the actual physics of these supernovas," McCully said.

Scientists to date have detected about 50 of this type of supernova but until now were unable to pinpoint the surviving "zombie star" white dwarf.

Our sun is destined to become a white dwarf, the fate of about 97% of stars.

"At the end of a star's life - for stars like our sun or a little bigger - the star runs out of fuel in the core and begins to collapse to a white dwarf. During this process, the outer layers of the star are puffed off into a nebula. The leftover core of the star is the white dwarf," McCully said.

Our sun cannot become a zombie star, however, because it lacks the requisite companion star.

SHARE THIS ARTICLE ON
Close Story
QUICKREADS

Less time to read?

Try Quickreads

  • People get off a coach at an entrance of Atlantis Sanya resort in Sanya, Hainan province, in November. (REUTERS)

    China’s Hainan starts mass Covid testing, imposes more lockdowns

    China's southern island province of Hainan started mass Covid-19 testing on Sunday, locking down more parts of the province of over 10 million residents, as authorities scramble to contain multiple Omicron-driven outbreaks, including the worst in capital Sanya, often called “China's Hawaii”. The number of cases in the province, rapidly spreading across the island located on the South China Sea, has crossed the 1100-mark from August 1 until Sunday noon.

  • Chinese Foreign Minister Wang Yi, center left, and his Bangladeshi counterpart A.K. Abdul Momen applaud as both countries sign agreements in Dhaka, Bangladesh, Sunday. 

    Bangladesh seeks China's help to repatriate Rohingya refugees

    Bangladesh on Sunday sought cooperation from China to repatriate Rohingya refugees to Myanmar during a visit by Foreign Minister Wang Yi, who promised better trade ties, investment and support for infrastructure development in the South Asian nations. Yi arrived in Dhaka on Saturday evening and met with Prime Minister Sheikh Hasina and Foreign Minister A.K. Abdul Momen. Amid recent tensions between China and Taiwan, Bangladesh issued a statement reiterating its support for the “one-China” policy.

  •  Rishi Sunak (R) poses with his wife Akshata Murty.

    Rishi Sunak on secret of his marriage: I'm organised, Akshata spontaneous

    Britain's prime ministerial candidate, Rishi Sunak, has shared that there was “clearly something” when he met his now wife, Akshata Murty – the daughter of Infosys co-founder Narayana Murthy – at a university in the US. In an interview with 'The Sunday Times', the former Chancellor opened up about his family life as he reflected on one of the secrets behind his marriage being the fact that the couple are very different people.

  • A China's flag. (File image)

    China to conduct 'regular' military drills east of Taiwan Strait median line

    The Chinese military will from now on conduct "regular" drills on the eastern side of the median line of the Taiwan Strait, Chinese state television reported on Sunday, citing a commentator. The median line has never been legally recognised, and is an "imaginary" line drawn up by the U.S. military for their combat requirements in the previous century, according to the state television commentator.

  • Bangladeshis queue at a gas station in Dhaka after government has increased fuel oil price. (Photo by AFP)

    After Sri Lanka, massive protests erupt in Bangladesh over fuel price hike

    After Sri Lanka's devastating crisis, thousands of protesters took to streets in several cities in Bangladesh after the Sheikh Hasina government hiked fuel prices by nearly 52 per cent, the highest since the neighbouring country got its independence. The Bangladesh government has blamed the ongoing Russia-Ukraine war for the hike in fuel prices. Bangladesh raised fuel prices will trim the country's subsidy burden, the government expects.

SHARE
Story Saved
×
Saved Articles
Following
My Reads
Sign out
New Delhi 0C
Sunday, August 07, 2022
Start 15 Days Free Trial Subscribe Now