Of spiral galaxies, star formation and supernovae

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Image: APOD NGC 2841 is a type of galaxy called a flocculent spiral, which features short spiral arms rather than prominent and well-defined galactic limbs. Credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: M. Crockett and S. Kaviraj (Oxford University, UK), R. O’Connell (University of Virginia), B. Whitmore (STScI) and the WFC3 Scientific Oversight Committee. The details of star formation in rare spirals such as NGC 2841 are difficult:

There is still much that astronomers don’t understand, such as how do the properties of stellar nurseries vary according to the composition and density of the gas present, and what triggers star formation in the first place? The driving force behind star formation is particularly unclear for a type of galaxy called a flocculent spiral, such as NGC 2841.

Because of the short-lived nature of massive stars, supernovae and star formation are inextricably linked, with the effects of shock waves either triggering or inhibiting star formation, as the shocks interact with the gas. Two recent papers have investigated supernovae in distant galaxies which appear unexpectedly luminous. The first gives an alternative to the pair instability route for the most massive stars, postulating supernovae driven in part at least by draining energy from the magnetar remnant. The second points to the origin of type Ib supernovae in the helium-rich, stripped cores of Wolf-Rayet stars.

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Dust in the edge-on spiral galaxy NGC 891, courtesy APOD

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