Researchers have found two objects that resemble stars that orbit one another very swiftly, with a full “year” lasting only 1.9 hours on Earth. The system, which goes by the catchy designation ZTF J2020+5033, is made up of two objects: one that is unquestionably a tiny star and another that lies somewhere between a star and a planet. Astronomers are learning more about how solar systems develop and evolve as a result of the two objects’ apparent age—they appear to be quite old.
A failed star lacking sufficient mass to ignite stellar fusion at its core is known as a Brown dwarf, and the planet-like object in the pair belongs to this category. However, because this specific object is so much fainter than its sibling, astronomers believe it to be a star rather than a brown dwarf because it lies on the cusp between the two.
The orbital period of the new brown dwarf is seven times faster than that of the old record-holder. It and its partner are so close together that they might easily revolve within our Sun. However, a report published this month contends that they didn’t form in this manner.
The scientists conclude that the orbit has drastically reduced because “both components must have been significantly larger when they were young than they are today.”
Uncovering some of the mysteries surrounding solar system creation requires an understanding of that procedure. They contend that magnetic braking is the main mechanism in operation.
Strong magnetic fields are present in stars. The material that is ejected from a star by solar flares, coronal mass ejections, and other solar wind-related phenomena is attracted by the magnetic fields. It is carried out far away from the star and eventually disappears. The substance, however, continues to spin alongside the star and its magnetic field before it leaves. This substance slows a star’s spin in a manner similar to a figure skater stretching out their arms to do so.
In a binary system, like two figure skaters holding hands with their arms outstretched, the magnetic fields of both stars cooperate to slow their orbital period around one another.
The stars lose mass over millennia, and they also circle closer and closer to one another.
Astronomers’ most recent models indicate that magnetic braking is most prominent in stars that are totally convective, meaning that their mass is such that their convection zone extends all the way inside of them.
But this binary pair is composed of two very tiny, partially convective stars.
Contrary to the assumption made by many binary evolution models, “this strongly suggests that magnetic braking remains efficient below the fully convective boundary in at least some stars.”
This suggests that our current conception of the development of binary pairings may need to be modified.
For instance, current estimates predict that ZTF J2020+5033 will surpass the Roche limit in 1.3 billion years. At that point, the gravity of its partner will be too near, tearing the brown dwarf apart. That timescale will arrive considerably sooner, in a matter of tens of millions of years, if magnetic braking is in fact present for these little stars.
It is obvious that the implications are important.
Astronomers must locate additional close-orbiting binary star-brown dwarf pairs to confirm that this isn’t just an anomaly in order to gain a clearer grasp of what is occurring. However, it’s simpler said than done. Brown dwarfs are thought to be widespread, but because they are so faint, it is difficult to discover them, leading to what astronomers refer to as a “brown dwarf desert” in their data sets.
The wide-field infrared transient explorer (WINTER) at Palomar Observatory, which started operations in 2021, the Vera Rubin Observatory, which is anticipated to start surveying in 2024, and the Nancy Grace Roman Space Telescope, which will launch in 2027, are fortunately three new instruments that will excel at finding precisely these objects.
More: Kareem El-Badry, Kevin B. Burdge, Jan van Roestel, and Antonio C. Rodriguez. “A transiting brown dwarf in a 2 hour orbit.” ArXiv Preprint.
