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.
Photo: Reuters
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 — 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 percent 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.
The canonical shot of an East Asian city is a night skyline studded with towering apartment and office buildings, bright with neon and plastic signage, a landscape of energy and modernity. Another classic image is the same city seen from above, in which identical apartment towers march across the city, spilling out over nearby geography, like stylized soldiers colonizing new territory in a board game. Densely populated dynamic conurbations of money, technological innovation and convenience, it is hard to see the cities of East Asia as what they truly are: necropolises. Why is this? The East Asian development model, with
June 16 to June 22 The following flyer appeared on the streets of Hsinchu on June 12, 1895: “Taipei has already fallen to the Japanese barbarians, who have brought great misery to our land and people. We heard that the Japanese occupiers will tax our gardens, our houses, our bodies, and even our chickens, dogs, cows and pigs. They wear their hair wild, carve their teeth, tattoo their foreheads, wear strange clothes and speak a strange language. How can we be ruled by such people?” Posted by civilian militia leader Wu Tang-hsing (吳湯興), it was a call to arms to retake
Desperate dads meet in car parks to exchange packets; exhausted parents slip it into their kids’ drinks; families wait months for prescriptions buy it “off label.” But is it worth the risk? “The first time I gave him a gummy, I thought, ‘Oh my God, have I killed him?’ He just passed out in front of the TV. That never happens.” Jen remembers giving her son, David, six, melatonin to help him sleep. She got them from a friend, a pediatrician who gave them to her own child. “It was sort of hilarious. She had half a tub of gummies,
The wide-screen spectacle of Formula One gets a gleaming, rip-roaring workout in Joseph Kosinski’s F1, a fine-tuned machine of a movie that, in its most riveting racing scenes, approaches a kind of high-speed splendor. Kosinski, who last endeavored to put moviegoers in the seat of a fighter jet in Top Gun: Maverick, has moved to the open cockpits of Formula One with much the same affection, if not outright need, for speed. A lot of the same team is back. Jerry Bruckheimer produces. Ehren Kruger, a co-writer on Maverick, takes sole credit here. Hans Zimmer, a co-composer previously, supplies the thumping
RSS