NASA Hubble Space Telescope Maps Explosive Nova During Stellar Outburst

Novae can be explosive, spewing material into space as they erupt. Now, astronomers have used NASA's Hubble Space Telescope to observe the light emitted by the close double-star system T Pyxidis during its latest stellar outburst and create a 3D map.

A nova erupts when a white dwarf, the burned-out core of a sun-like star, has siphoned off enough hydrogen from a companion star in order to trigger a thermonuclear runaway. As hydrogen builds up on the surface of the white dwarf, it becomes hotter and denser. Eventually, the star detonates like a colossal hydrogen bomb, creating a brilliant explosion that leads to a 10,000-fold increase in brightness.

T Pyxidis, also known as T Pyx, actually undergoes this type of eruption every 12 to 50 years. The last explosion was seen in 1966, though others were recorded in 1944, 1920, 1902 and 1890. The recurring explosions have allowed astronomers to take advantage of the resulting light. Using Hubble's Wide Field Camera 3, the researchers examined T Pyx while it was erupting. The light lit up a disk of material surrounding the nova from previous ejecta. The disk was so vast, in fact, that the nova's light couldn't illuminate all of the material at once. Instead, the light swept across the debris, sequentially illuminating parts of the disk; this particular phenomenon is called a light echo.

By studying this light echo, the researchers were able to see which parts of the disk were nearer to Earth and which sections were farther away. By tracing the light, they were also able to assemble a 3D map of the structure around the nova.

After assembling the map, the astronomers found that it was likely that material continues expanding outward along the star system's orbital plane. However, the material doesn't escape the system.

"We fully expected this to be a spherical shell," said Arlin Crotts of Columbia University in a news release. "This observation shows it is a disk, and it is populated with fast-moving ejecta from previous outbursts."

The findings have allowed the astronomers to refine estimates of the nova's distance from Earth. While previous estimates were between 6,500 and 16,000 light-years, the new distance is now 15,600 light-years. In addition, the research shows a little bit more about novae in general and will help researchers in future studies. Currently, the team plans to continue to analyze the Hubble data to develop an outflow model.

The findings are published in the Astrophysical Journal Letters.