For the first time in many years, a bright naked-eye comet is gracing our skies: C/2020 F3 (NEOWISE). It's been up pre-sunrise for the past few weeks, but starting this week it starts to peek above the horizon after sunset, making it much easier on most people to see it. Over the next two weeks or so it'll be moving higher in the sky, and well placed for observing in the northern hemisphere.
It's difficult to predict how bright it will be, even over the coming few days. Comets are fickle! Until just a few days ago no one was sure if this one would even survive perihelion, its closest passage to the Sun — that occurred on 3 July, when it was 44 million kilometers from our star, about the same distance as Mercury from the Sun. Many small comets break up under the stress, but NEOWISE seems to have done very well, holding itself together and forming a very long tail that gives comets their iconic look (more on that in a sec).
Comet C/2020 F3 (NEOWISE) over St. Peter’s dome in Rome on 10 July 2020. Credit: Gianluca Masi/The Virtual Telescope Project
Right now its orbit is ...