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The skywatching world is abuzz with news of a new visitor from very far away. It’s been designated Comet 2I/Borisov, but it’s not just any comet: it’s a comet that appears to have originated from outside our solar system — only the second such object ever discovered.
The comet was first observed at the end of August by Crimean amateur astronomer Gennady Borisov, and it has since been tracked by astronomers all over the world and photographed by the Hubble Space Telescope.
“NASA’s Hubble Space Telescope has given astronomers their best look yet at an interstellar visitor — comet 2I/Borisov — whose speed and trajectory indicate it has come from beyond our solar system.
“This Hubble image [above], taken on October 12, 2019, is the sharpest view of the comet to date. Hubble reveals a central concentration of dust around the nucleus (which is too small to be seen by Hubble).
“Comet 2I/Borisov is only the second such interstellar object known to have passed through the solar system. In 2017, the first identified interstellar visitor, an object officially named ‘Oumuamua, swung within 24 million miles of the Sun before racing out of the solar system. “Whereas ‘Oumuamua appeared to be a rock, Borisov is really active, more like a normal comet. It’s a puzzle why these two are so different,” said David Jewitt of the University of California, Los Angeles (UCLA), leader of the Hubble team who observed the comet.
“As the second known interstellar object found to enter our solar system, the comet provides invaluable clues to the chemical composition, structure, and dust characteristics of planetary building blocks presumably forged in an alien star system a long time ago and far away.“ (hubblesite.org)
How do we know it’s coming from outside our solar system? By taking a number of measurements of the comet’s position over a series of days, and then applying some math, it’s trajectory can be readily calculated. That trajectory shows it’s not orbiting the sun like the planets and like ordinary comets do. Instead, it’s approaching the plane of the solar system from a high angle and will shoot right through.
Comet Borisov is not expected to brighten enough to be visible to the naked eye, but comets can be unpredictable, so we’ll be keeping an eye on the interstellar news.
What celestial observations will you and your students be making in your homeschool this month? 🔭
❡ Watchers of the skies: This is one of our occasional Homeschool Astronomy posts. Add your name to our River Houses mailing list (riverhouses.org/newsletter) and get great homeschool teaching ideas delivered right to your mailbox every week. 😊