Two young protostars in a cosmic tango that brings them within 10 stellar radii every two weeks. This artist’s illustration of the DQ Tau system shows the intense fireworks that occur every fortnight as these two swiftly moving stars are ever, ever getting back together. Image credit: NASA/JPL-Caltech/R. Hurt (IPAC).
DQ Tau is a unique binary system. Approximately 650 light-years away in the Taurus constellation, DQ Tau consists of two young stars still in the process of forming. The protostars have not yet ignited hydrogen burning in their cores (the fusion process that heats mature stars). Instead, they are glowing as they evolve from their natal form (diffuse clouds of gas) and are heated by this gravitational collapse. Each is half the mass of the Sun and currently twice its radius, dancing in a highly elongated orbit which has them plunging in towards each other every 15.8 days. At closest approach in this violent cosmic tango, the separation between the two stars is exceptionally small, only 8-10 stellar radii. Characteristic of this early phase, the protostars in DQ Tau harbor strong magnetic fields on their surfaces. Also, like most protostars, the DQ Tau system is surrounded by a disk in which planets are also forming. Understanding planet formation, including how the intense flares characteristic of protostars affect disk heating and chemistry, are areas of active research.
DQ Tau provides an exceptional laboratory for such studies. Like clockwork, the DQ Tau system brightens at closest approach. While large X-ray flares in young stars are generally rare and unpredictable (as on our own star, the Sun), the presence of the predictable X-ray super-flares and outbursts in DQ Tau enables synchronized studies of these cosmic fireworks. Like tourists at Yellowstone National Park timing their visit to Old Faithful Geyser, astronomers can plan ahead, coordinating telescopes to jointly investigate these intense flares and understand how they affect the protoplanetary disk. X-ray flares come as the protostar magnetospheres collide, while the lower energy optical and ultraviolet flares also come from accretion of material onto the young stars. Infrared and radio studies probe the changing temperature and chemistry of the protoplanetary disk.
In a recent paper published in the Astrophysical Journal, scientists led by Konstantin Getman at Pennsylvania State University report on new observations of a single orbit of DQ Tau in July and August 2022 using the NuSTAR, Swift, and Chandra X-ray telescopes. NuSTAR accesses higher energy X-rays, while Swift and Chandra access lower energy X-rays. The observations indicate that most of the X-ray emission is from interactions of the magnetospheres of these young stars at closest approach. In a process similar to what is seen on our own Sun, magnetic field collisions and reconnections produce strong high-energy X-ray emission. This heats the surrounding region to high temperature, detectable as thermal emission in the lower energy X-rays. Notably, however, flares on our Sun occur among coronal magnetic loops much smaller than the star, with sizes of 1000 to 10,000 km. In contrast, the DQ Tau super-flares occur on spatial scales a thousand times larger, corresponding to approximately 10 million km or tens of stellar radii. The current study is part of a broader campaign using additional ground-based telescopes to investigate the influence of DQ Tau’s stellar radiation on the chemistry within its surrounding disk.
DQ Tau is a unique binary system. Approximately 650 light-years away in the Taurus constellation, DQ Tau consists of two young stars still in the process of forming. The protostars have not yet ignited hydrogen burning in their cores (the fusion process that heats mature stars). Instead, they are glowing as they evolve from their natal form (diffuse clouds of gas) and are heated by this gravitational collapse. Each is half the mass of the Sun and currently twice its radius, dancing in a highly elongated orbit which has them plunging in towards each other every 15.8 days. At closest approach in this violent cosmic tango, the separation between the two stars is exceptionally small, only 8-10 stellar radii. Characteristic of this early phase, the protostars in DQ Tau harbor strong magnetic fields on their surfaces. Also, like most protostars, the DQ Tau system is surrounded by a disk in which planets are also forming. Understanding planet formation, including how the intense flares characteristic of protostars affect disk heating and chemistry, are areas of active research.
DQ Tau provides an exceptional laboratory for such studies. Like clockwork, the DQ Tau system brightens at closest approach. While large X-ray flares in young stars are generally rare and unpredictable (as on our own star, the Sun), the presence of the predictable X-ray super-flares and outbursts in DQ Tau enables synchronized studies of these cosmic fireworks. Like tourists at Yellowstone National Park timing their visit to Old Faithful Geyser, astronomers can plan ahead, coordinating telescopes to jointly investigate these intense flares and understand how they affect the protoplanetary disk. X-ray flares come as the protostar magnetospheres collide, while the lower energy optical and ultraviolet flares also come from accretion of material onto the young stars. Infrared and radio studies probe the changing temperature and chemistry of the protoplanetary disk.
In a recent paper published in the Astrophysical Journal, scientists led by Konstantin Getman at Pennsylvania State University report on new observations of a single orbit of DQ Tau in July and August 2022 using the NuSTAR, Swift, and Chandra X-ray telescopes. NuSTAR accesses higher energy X-rays, while Swift and Chandra access lower energy X-rays. The observations indicate that most of the X-ray emission is from interactions of the magnetospheres of these young stars at closest approach. In a process similar to what is seen on our own Sun, magnetic field collisions and reconnections produce strong high-energy X-ray emission. This heats the surrounding region to high temperature, detectable as thermal emission in the lower energy X-rays. Notably, however, flares on our Sun occur among coronal magnetic loops much smaller than the star, with sizes of 1000 to 10,000 km. In contrast, the DQ Tau super-flares occur on spatial scales a thousand times larger, corresponding to approximately 10 million km or tens of stellar radii. The current study is part of a broader campaign using additional ground-based telescopes to investigate the influence of DQ Tau’s stellar radiation on the chemistry within its surrounding disk.
