Like other amateurs, I observed the brightening of Comet Tempel 1 after it was hit by Deep Impact on July 4, 2005. Was this the most distant human-caused event that’s been easily verifiable with ordinary optics? (I used my 12-inch Dobsonian reflector.)

Comet Tempel 1
Comet 9P/Tempel 1 at 11th magnitude.
Johannes Schedler

Yes, we think so. The Deep Impact collision occurred 0.89 astronomical unit from Earth — more than 300 times the distance to the Moon.

When the Soviet rocket Lunik II struck the Moon south of the crater Autolycus on September 13, 1959, three Hungarian observers saw the expanding impact cloud with a 7-inch refractor (S&T: November 1960, page 265).

— Alan MacRobert

Tags

Asteroid Impacts Comets & Asteroids Perception Limits

About Alan MacRobert

Alan M. MacRobert became an avid Sky & Telescope subscriber in 1966 at age 14, joined the editorial staff in 1982, and is now a senior contributing editor, semi-retired. He played a role in practically every part of the magazine and the company's other products for more than a generation, both on the amateur-observing side and the science-reporting side. In 1994 a book collection of his observing how-tos and telescopic sky tours was published as Star Hopping for Backyard Astronomers. He has produced This Week's Sky at a Glance online every week since 1989.

Comments


You must be logged in to post a comment.