A cataclysmic pair of stars with the shortest orbit ever seen

A cataclysmic pair of stars with the shortest orbit ever seen

A group of researchers at the Massachusetts Institute of Technology discovered a binary system of stars with an ultra-short orbit of only 51 minutes, which would be a cataclysmic variable, a rare class of binary systems.

If half the stars in the Milky Way

This system seems to belong to a rare class of cataclysmic variables in which a star like our sun revolves around a white dwarf.

Astronomers discovered a new system in a large catalogue of stars developed at the centre of Zwicky Transient Facilitation. The study uses a camera attached to the telescope at the Palomar Observatory in California to take pictures of a large area of high resolution sky. The study took over 1,000 pictures of each of the more than 1 billion stars in the sky and recorded a change in the brightness of each star for days, months and years.

Kevin Berge, a physicist at the Pappalardo Department of Physics at the Massachusetts Institute of Technology and lead author, studied the ZTF catalogue in search of signals from ultra-short orbit systems whose dynamics can be so extreme that they emit sharp bursts of light and gravity waves. In particular, Burge examined ZTF data for stars:

  • Who blinked several times. With a period of less than one hour.

Using the algorithm, researchers sifted about 1 million stars that seemed to blink every hour or so. Among them, Burge sought signals of particular interest and found J1813+4251, which he again observed with the WM Keck observatory in Hawaii and the Gran Telescopio Canarias in Spain, and found that they could clearly see how the light of the system was changing with each eclipse. By this clarity, they were able to accurately measure the mass and radius of each object, as well as their orbital period.

Characteristics of a cataclysmic couple

The first object is probably a white dwarf the size of 1/100 of our Sun and about half of its mass. The second object is a dying star, but similar to the Sun, with a tenth of its size and mass, or the size of Jupiter.

It seemed like stars rotated around each other every 51 minutes, and to explain that, they turned to a study by the Massachusetts Institute of Technology about 30 years ago, where scientists predicted that ultra-short-orbiting systems must exist as cataclysmic variables.

The cataclysmic variable occurs when two stars come together in billions of years, and as a result, the white dwarf begins to accumulate or devour the material of a partner star, and this process can produce huge, variable flashes of light that astronomers thought centuries ago to be the result of an unknown cataclysm, hence their name.

Cataclysmic variable with very short orbit

The detected system is a cataclysmic variable with the shortest orbit detected to date. With data available, researchers have modelled what the system is probably doing today and how it should evolve over the next few hundred million years.

As a result, Burge and his colleagues assumed that the stars were currently in a state of transition and that a star like the Sun had given most of its hydrogen atmosphere to a white dwarf, the first of which would eventually be reduced to a predominantly dense, helium-rich core; after 70 million years, the stars would be ever closer, their ultra-short orbit would be only 18 minutes, then they would begin to expand and remove.