More cool work by my friend Chip Kobulnicky. Bow shock nebulae happen when outflow from a star (stellar winds usually) collide with the surrounding gas. If the star is moving in a particular direction, the wind-gas collision is stronger in the direction of motion, like the bow wave of a boat. Arcs like these can have other explanations (like asymmetric flows or non-uniform ambient gas) but most are likely “runaway” stars that are moving unusually fast.
OK…now I have to ask a really dumb question…how or why, did ‘they’ name them runaway stars? Obviously they know that an explosion of a supernova started them on their journey by the force from the Nova that is still pushing them. They won’t stop their flight until they collide with another object. Am I right or not? Thank you for showing us this wonderful sequence of the stars.
+Nancy E. Perrine That’s a great question, actually. We call any star with an unusually high speed relative to other stars a runaway. Some indeed are caused by asymmetric supernovae. But many (including most of these I’d wager) are caused by gravitational slingshotting in a star cluster — a chance close encounter between two or more stars ejects one out the cluster. Besides these bow shocks we can tell if a star is a runaway by measuring its speed toward/away from us via Doppler shift or measuring side-to-side motion by taking to images many years apart and seeing how much it moves. Combining these can give us a true 3-dimensional speed (if we also know the distance to the star)
Thanks Chris, I am so glad you guys and gals know and understand the heavens. I love the reflections you share with us. Thanks for sharing your work.
prayer is the best weapon that you can enter the heaven… mark my words…?
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