Janus white dwarf star: Astronomers found a white dwarf star with two sides. White dwarfs form when a star like our sun exhausts its fuel, swells into a red giant, and sheds its outer layers, leaving a brilliant, white-hot core.
This recently discovered white dwarf, named “Janus” after the Roman god of transitions, has two sides, one rich in hydrogen and the other in helium. The groundbreaking Nature study on this unusual finding has piqued scientific interest.
“The surface of the white dwarf completely changes from one side to the other,” said lead study author Ilaria Caiazzo, a postdoctoral scholar research associate in astronomy at Caltech. People are astonished by my observations.”
White dwarfs have the mass of the sun in a planetary body. During a star’s death, gravitational forces cause heavier elements to sink toward the center and lighter elements like hydrogen and helium to rise. As white dwarfs cool, their atmospheres change from hydrogen to helium.
However, Caltech’s Palomar Observatory’s Zwicky Transient Facility found an unusual remnant. Researchers noticed Janus’s rapid brightness change during a magnetized white dwarf survey.
Palomar’s CHIMERA, Gran Telescopio Canarias’ HiPERCAM, and Hawaii’s W.M. Keck Observatory confirmed Janus’ dual-faced composition. Astronomers used a spectrometer to identify hydrogen and helium in the star’s light.
Janus, at 62,540 degrees Fahrenheit (34,726 degrees Celsius), is a mystery. Researchers think the star is evolving differently. “Not all, but some white dwarfs transition from being hydrogen- to helium-dominated on their surface,” Caiazzo said. We may have caught one such white dwarf.
Magnetic fields may explain Janus’ unusual appearance. Strong and asymmetric magnetic fields may prevent atmospheric material mixing, creating the unique composition.
“The magnetic fields may lead to lower gas pressures in the atmosphere, and this may allow a hydrogen ‘ocean’ to form where the magnetic fields are strongest,” said study coauthor and Caltech theoretical astrophysics professor James Fuller. We don’t know which theory is right, but magnetic fields are the only way to explain the asymmetric sides.”
Janus advances our knowledge of white dwarfs. The Zwicky Transient Facility helps astronomers find mysterious stellar remnants.
Our Reader’s Queries
What is the two-faced star Janus?
Dubbed Janus after the Roman god of transition, the recently unearthed white dwarf was first spotted by the Zwicky Transient Facility (ZTF), a tool that surveys the night sky from Caltech’s Palomar Observatory near San Diego.
What is the star named Janus?
Astronomers have spotted Janus, a white dwarf star, which is one of the most compact objects in the universe. It’s unique because it’s made of hydrogen on one side and helium on the other, earning it the nickname Janus.
What is the two-faced dwarf star?
Janus, the binary-hued, extinguished remnant of a star, used to bear a resemblance to our sun. This white dwarf exists roughly 1,300 light-years distant in the Cygnus constellation.
What is the hottest white dwarf star?
Title: Extreme Stars
Hottest Star: RX J0439.8?6809250
Surface Temperature: 250,000 K (250,000 °C; 450,000 °F)
Coolest Star: LSPM J1403+4533
Surface Temperature: 2,670 K (2,400 °C; 4,350 °F)
Brightest Star: Z Andromedae B
Luminosity: 1,500 – 9,800 L?
Dimmest Star: PSR J2222-0137 B
Luminosity: too dim to observe