Next week’s night sky:
At the end of March we receive another opportunity to view the Zodiacal Light – if you live in a location where the sky is free of light pollution. After the evening twilight has disappeared, you’ll have about half an hour to check the western sky for a broad wedge of faint light extending upwards from the horizon and centered on the ecliptic (i.e., below Mars). The viewing period will end with the new moon on April 11.
A new picture of a black hole!
The elliptical galaxy M87 sits 55 million light-years away, at the heart of the nearby Virgo Cluster. Deep inside this galaxy lurks a supermassive black hole that weighs 6.5 billion times the mass of our Sun. That black hole instantly became famous in 2019 when the Event Horizon Telescope (EHT) collaboration released its portrait — the first ever direct image of the shadow of a black hole.
Now, the EHT collaboration has released updated views of M87 that offer an unprecedented look at the light streaming from just outside its black hole. These pictures reveal the complex structure of a powerful magnetic field that astronomers believe is responsible for shooting a 5,000 light-year-long jet from the black hole at nearly the speed of light.
To learn more, go here: Polarimetric properties of Event Horizon Telescope targets from ALMA
Supernovae Simulations
Astronomers are now in a better position to interpret observations of supernova remnants thanks to computer simulations of these cataclysmic events by RIKEN astrophysicists.
When certain types of stars die, they go out in a blaze of glory—an incredibly powerful explosion known as a supernova. One of the most common forms of supernova, type Ia, starts with a dense white dwarf star that has burned up its hydrogen fuel. Matter flowing from a companion star can jump-start a runaway nuclear fusion reaction in the dwarf, triggering a massive conflagration that creates many of the heavier elements in the Universe. These are hurled outward in a luminous cloud known as a remnant, which bears an imprint of the explosion.
Researchers have been developing three-dimensional computer simulations that recreate supernovae. Their simulations involve two steps: the first one models the supernova explosion itself, while the second one uses that as the input for a model of the supernova remnant. Their goal is to explore how different explosion conditions produce remnants with characteristic shapes and compositions, similar to those we observe in our galaxy.
Their latest simulations focus on two aspects of supernovae: how the explosion ignites inside a white dwarf, and how combustion rips through the star. Ignition can start at just a few places inside the white dwarf, or it can be triggered at many points simultaneously. Meanwhile, the combustion might be a deflagration—a turbulent fire that moves slower than the local speed of sound—or it may involve deflagration followed by supersonic detonation.
By putting these options together in different ways, the researchers produced four models of supernova remnant. Each model has its distinctive properties. For example, a supernova with few ignition points and a deflagration explosion produced a remnant with a symmetric shell that was offset from the center of the explosion. In contrast, a simulation involving few ignition points and a detonation produced a remnant in which half of the outer shell was twice as thick as the other half. Remnants from the deflagration simulations also featured unexpected ‘seams’ of denser material.
These results suggest that the best time to see a supernova’s imprint on its remnant is within roughly 100–300 years after the explosion. This imprint is visible for longer in supernovae with fewer ignition points, and all the remnants in the simulations became spherical overall within 500 years. These results will guide astronomers as they interpret observations of supernova remnants.
Do you have any cool astronomy research news from this week? Share it in the comments below!