A busy news week: a Nobel prize, another chance of auroras, and… a comet. It’s probably not the comet of the century, but comets like this one show up only about once every ten years. This one has already been visible in early morning skies. This week it enters our evening skies, and will likely be a lovely sight after dark for the rest of October.
Thursday, Friday and Saturday this week, immediately after sunset and just to the right and above the Sun, comet A3 MAY be at its most spectacular. BE READY! You will need a low and rather flat horizon, and you have less than an hour to see it before it sets, too.
Later in the month it will be visible longer into the evening, but much less bright.
What is a comet? Its core (or “nucleus”) is a large ball of ice and dust, perhaps 20 miles [40 kilometers] across, traveling on an orbit of the Sun and moving through the solar system among the planets. That core is far too small and far away to see. But when the comet approaches the Sun, the Sun heats the core, which throws off dust and gas that is blown by the solar wind into a big cloud around the core and into huge trails that stretch tens of millions of miles [km]. These trails reflect sunlight, and can be seen from Earth despite being millions of miles [km] away.
Please do not confuse this comet with Earth’s temporary second moon, which has gotten a ridiculous amount of overheated press, causing both distraction and confusion. Here’s how this itty-bitty “moonlet” compares with comet A3.
- Moonlet temporarily orbits Earth; comet A3 orbits the Sun
- Moonlet is a rock the size of a bus; comet A3’s core is the size of a big city, and its tails are tens of millions of miles long
- Moonlet at its closest will be tens of thousands of miles [km] away; comet A3 at its closest will be 44 million miles [71 million km] away
- Moonlet can only be seen with powerful professional telescopes; comet A3’s head and tails may be dramatic to the naked eye and may even be visible, for a few days, during daylight
The last bullet point is the most important. Moonlet is of intellectual interest only; there’s absolutely nothing to see, despite the crazed news stories in the media. Comet A3 might turn out to be one of the better celestial objects to see in a lifetime. Get the word out!
