00:00 This is Halley's Comet, one of our solar system's rarest sights.
00:08 It was last visible with the naked eye in 1986, and it won't be viewable without a
00:12 telescope again for nearly another 40 years.
00:15 However, at the moment, it's about to mark another important milestone in its journey,
00:20 as Halley's Comet has just reached its aphelion, or its furthest point from the sun.
00:24 The aphelion is the unofficial halfway-ish point in the comet's narrow parabolic orbit
00:28 through our star system.
00:30 It's now set to arc and come back towards the sun.
00:32 But at the moment, the comet is some 3.3 billion miles away, or around 35 times the distance
00:38 Earth is from our central star, meaning it's currently further than planet Neptune.
00:42 This change in direction also means the comet is traveling at its slowest speed during its
00:46 journey as well, moving at just 0.91 kilometers a second, or around 2,000 miles per hour.
00:52 Its great distance also means that our telescopes can't see it out there either.
00:56 In fact, the last time astronomers were able to zero in on it was way back in 2003.
01:01 So when can we expect the next flyby?
01:03 Well, don't hold your breath.
01:04 The next time Halley's Comet will be visible without a high-tech telescope will be summer
01:08 2061.
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