Type Ia supernova observed in ultraviolet light

Chuck Bednar for redOrbit.com – @BednarChuck

Astrophysicists refer to Type Ia supernovae as “standard candles” because they are used to measure distances of objects throughout the universe, but are they really all the same? That’s what the authors of a new Nature study wanted to find out.

Researchers from the California Institute of Technology (Caltech) and the Weizmann Institute of Science joined forces recently to study more about these supernovae using a robotic telescope array located to observe a star just four days into an explosion.

Using instruments at the Palomar Transient Factory, they spotted the young supernova, and used NASA’s Swift Space Telescope to observe the blast in the invisible ultraviolet range. Thanks to these observations, the researchers were able to detect a brief but never-before-seen spike in the high-energy radiation early on in the supernova process.

UV observations shed new light on how supernovae happen

According to Professor Avishay Gal-Yam from the Weizmann Institute’s Particle Physics and Astrophysics Department, this increase fits with a model in which a dwarf star has a companion. The white dwarf, the professor explained, “is the mass of the Sun packed into a sphere the size of the Earth, while its companion is around 50-100 times bigger around than the Sun.”

The researchers explained that material flowed from the diffuse star to the denser one until the pressure from the added mass eventually caused the smaller of the two stars to detonate. They added that the radiation spike was caused by the initial material ejected during the blast hitting the companion star.

The findings demonstrate the importance of the ultraviolet-range observations of the exploding star. Gal-Yam said he is hopeful that the ULTRASAT mini-satellite currently in the works at the Weizmann Institute, the Israeli Space Agency, and NASA, can used observations in the UV range to determine if this process is common amongst type Ia supernovae.

“Ultraviolet is crucial, because initially, supernova blasts are so energetic that the most important information can only be gathered in short wavelengths. And it can only be seen from a space telescope, because the ultraviolet wavelengths are filtered out in the Earth’s atmosphere,” added Gal-Yam.


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