Scientists discover ultra-massive white dwarf star formed after a white dwarf merged with another star
Cover illustration: A white dwarf star merging into a red giant star. A bow shock forms as the dwarf plunges through the star’s outer atmosphere. The passage strips down the white dwarf’s outer layers, exposing an interior carbon core. Artwork: NASA, ESA, STScI, Ralf Crawford (STScI)
On August 13, an international team of astronomers announced their discovery of a cosmic rarity: an ultra-massive white dwarf star resulting from a white dwarf merging with another star, rather than through the evolution of a single star. This discovery, made by NASA’s Hubble Space Telescope’s sensitive ultraviolet observations, suggests these rare white dwarfs may be more common than previously suspected. It is noteworthy to state that theHubble Space Telescope has been operating for more than 30 years and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe.
“It’s a discovery that underlines things may be different from what they appear to us at first glance,” said the principal investigator of the Hubble program, Boris Gaensicke, of the University of Warwick in the United Kingdom. “Until now, this appeared as a normal white dwarf, but Hubble’s ultraviolet vision revealed that it had a very different history from what we would have guessed.”
A white dwarf is a dense object with the same diameter as Earth and represents the end state for stars that are not massive enough to explode as core-collapse supernovae. Our Sun will become a white dwarf in about 5 billion years.
Theoretically, a white dwarf can have a mass of up to 1.4 times that of the Sun, but white dwarfs heavier than the Sun are rare. These objects, which astronomers call ultra-massive white dwarfs, can form either through the evolution of a single massive star or through the merger of a white dwarf with another star, such as a binary companion.
This new discovery, published in the journal Nature Astronomy, marks the first time that a white dwarf born from colliding stars has been identified by its ultraviolet spectrum. Astronomers used Hubble’s Cosmic Origins Spectrograph to investigate a white dwarf called WD 0525+526. Located 128 light-years away, it is 20% more massive than the Sun.
In visible light, the spectrum of WD 0525+526’s atmosphere resembled that of a typical white dwarf. However, Hubble’s ultraviolet spectrum revealed something unusual: evidence of carbon in the white dwarf’s atmosphere. Because WD 0525+526’s origin was revealed only once astronomers glimpsed its ultraviolet spectrum, it’s likely that other seemingly “normal” white dwarfs are actually the result of cosmic collisions — a possibility the team is excited to explore in the future.
.
(Source: NASA)
Posted by Richard Webster, Ace News Today
Follow Richard on Facebook, Twitter & Instagram
