In news- A team of astronomers, using NASA’s Transiting Exoplanet Survey Satellite (TESS) have reported a unique phenomenon in a white dwarf about 1,400 light years from Earth. They saw the white dwarf lose its brightness in 30 minutes.
What is a pulsating white dwarf?
A pulsating white dwarf is a white dwarf star whose luminosity varies due to non-radial gravity wave pulsations within itself. Known types of pulsating white dwarfs include DAV, or ZZ Ceti, stars, with hydrogen-dominated atmospheres.
White dwarf and TW Pictoris-
- It is part of a binary system called TW Pictoris, located in the Pictoris constellation, and the binary system is about 1400 light years from us.
- TW Pictoris consists of a white dwarf that feeds from a surrounding accretion disk fuelled by hydrogen and helium from its smaller companion star.
- The two objects are so close to each other that the star transfers material to the white dwarf.
- As this material approaches the white dwarf it forms an accretion disk or a disk of gas, plasma, and other particles around it.
It’s switch on and off mode-
- As per scientists,in this system the donor star in orbit around the white dwarf keeps feeding the accretion disk.
- As the accretion disk material slowly sinks closer towards the white dwarf it generally becomes brighter(on mode).
- During the ‘on’ mode, when the brightness is high, the white dwarf feeds off the accretion disk as it normally would.
- Suddenly and abruptly the system turns ‘off’ and its brightness plummets.
- When this happens the magnetic field is spinning so rapidly that a centrifugal barrier stops the fuel from the accretion disk constantly falling on to the white dwarf.
The new discovery will help the astronomers understand the physics behind accretion – how black holes and neutron stars feed material from their nearby stars.
Transiting Exoplanet Survey Satellite (TESS)-
- TESS is a space telescope for NASA’s Explorers program, designed to search for exoplanets ( in orbit around the brightest dwarf stars in the sky) using the transit method in an area 400 times larger than that covered by the Kepler mission.
- It was launched in 2018 by Falcon rocket system.
- Using the Hubble Space telescope and TESS, astronomers have identified several white dwarfs over the years.