Planetary bodies observed for the first time in dead star’s habitable zone – Taking it slow?
According to a new study led by UCL researchers, a moon-sized ring of planetary debris has been observed orbiting close to a white dwarf star, suggestive of a new moon. nearby planets in the “habitable zone”, where water and life could exist.
UNIVERSITY OF LONDON
Planetary objects observed for the first time in the habitable zone of a dead star
According to a new study led by UCL researchers, a moon-sized ring of planetary debris has been observed orbiting close to a white dwarf star, suggestive of a new moon. nearby planets in the “habitable zone”, where water and life could exist.
White dwarfs are embers glowing stars that have burned off all of their hydrogen fuel. Nearly all stars, including the Sun, will eventually become white dwarfs, but very little is known about their planetary systems.
In the study, published in Monthly Notice of the Royal Astronomical SocietyAn international team of researchers has measured the light from a white dwarf star in the Milky Way called WD1054–226, using data from ground- and space-based telescopes.
To their surprise, they discovered distinct streaks of light corresponding to 65 evenly spaced clouds of planetary debris that orbit the star every 25 hours. The researchers concluded that the precise regularity of the transition structures – which dim the star’s light every 23 minutes – suggests that they are kept in such a precise arrangement by a nearby planet. there.
Lead author Professor Jay Farihi (UCL Physics & Astronomy) said: “This is the first time that astronomers have detected any kind of planetary body in the habitable zone of a white dwarf.
“The moon-sized structures we have observed are irregular and dusty (like comets, for example) rather than solid, spherical objects. Their sheer regularity, one every 23 minutes passing in front of the star, is a mystery we cannot yet explain.
“An interesting possibility is that these objects are kept in such equidistant orbits because of the gravitational influence of a nearby planet. Without this effect, friction and collision would cause the structures to scatter, losing the exact regularity observed. A precedent for this ‘herding’ is how the gravitational pull of the moons around Neptune and Saturn helps create stable ring structures orbiting these planets.
“The possibility of a planet in the habitable zone is both exciting and surprising; We were not looking for this. However, it’s important to keep in mind that more evidence is needed to confirm the presence of a planet. We cannot observe the planet directly, so confirmation can be made by comparing computer models with further observations of the star and orbiting debris.”
It is thought that the orbit around this white dwarf was wiped out during the giant stellar phase of its life, and that any planet that could potentially contain water and thus life would be a major step forward. recently developed. The area will be habitable for at least two billion years, including at least a billion years into the future.
More than 95% of all stars will eventually become white dwarfs. The exceptions are the most massive stars that explode and become black holes or neutron stars.
Professor Farihi added: “As our Sun will become a white dwarf in a few billion years, our study provides a glimpse into the future of our own solar system.”
As stars begin to run out of hydrogen, they expand and cool, becoming red giants. The Sun will enter this phase in 4 to 5 billion years, swallowing Mercury, Venus, and possibly Earth. Once the outer matter is gently blown away and the hydrogen is exhausted, the star’s hot core remains, slowly cooling over billions of years – this is the star’s white dwarf phase.
Planets orbiting white dwarfs are challenging for astronomers to detect because these stars are much dimmer than main sequence stars (such as the Sun). So far, astronomers have found only tentative evidence of a gas giant (like Jupiter) orbiting a white dwarf star.
For the new study, the researchers observed WD1054–226, a white dwarf star 117 light-years away, recording changes in its light over 18 nights using a high-speed camera ULTRACAM altitude attached to the ESO 3.5m New Technology Telescope (NTT) at La Silla Observatory in Chile. To better explain the changes in light, the researchers also looked at data from NASA’s Transiting Exoplanet Survey Satellite (TESS), which allows researchers to confirm planetary structures. has a 25 hour orbit.
They found that light from WD1054–226 is always partially obscured by massive clouds of orbiting matter that pass in front of it, suggesting a ring of planetary debris orbiting the star.
The habitable zone, sometimes called the Goldilocks zone, is the region where the temperature theoretically allows liquid water to exist on the surface of a planet. Compared to a star like the Sun, the habitable region of a white dwarf will be smaller and closer to the star because the white dwarf emits less light and therefore heat.
The structures observed in the study orbit in an area that would have been surrounded by the star when it was a red giant, and therefore likely formed or arrived relatively recently, rather than after the birth of the star and its planetary system.
The study received funding from the UK Science and Technology Facility Council (STFC) and involved a team of researchers from six countries, including Boston University, the University of Warwick, the University of Lund University, Cambridge University, St Andrews University, Wesleyan University, La Laguna University, Naresuan University, University of Sheffield, and the Instituto de Astrofísica de Canarias.
JOURNEYS
Monthly Notice of the Royal Astronomical Society
DOI
RESEARCH METHODS
Data analysis / statistics
ARTICLE TITLE
Continuous and complex transition from planetary debris disk’
ARTICLE PUBLICATION DATE
February 11, 2022
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