* Astronomy

Halley's Comet or Comet Halley (officially designated 1P/Halley) is the most famous of the periodic comets, and is visible from Earth every 75 to 76 years. Many comets with long orbital periods may appear brighter and more spectacular, but Halley is the only short-period comet that is clearly visible to the naked eye, and thus, the only naked-eye comet that might appear twice in a human lifetime. During its returns to the inner solar system, it has been observed by astronomers since at least 240 BC, but it was only recognised as a periodic comet in the 18th century when its orbit was computed by English astronomer Edmond Halley, after whom it is named. Halley's Comet last appeared in the inner Solar System in 1986 and will next appear in mid-2061.

Is Halley's comet an alien interloper?

Our sun may have stolen the vast majority of its comets from other stars.
Hal Levison of the Southwest Research Institute in Boulder, Colorado, and his colleagues say many of the Oort-cloud objects may have been stolen from other stars born in the same stellar nursery as the sun. Most stars like the sun form in clusters of between 10 and 1000 members. According to the team's simulations, encounters between stars in this crowded environment tend to disturb their scattered discs and detach objects from them, creating a reservoir of free-floating comets.
When stars later leave the cluster, some of these objects move along with them, getting captured into wide, Oort cloud-like orbits.
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On this day in 240 BC the first perihelion passage of Halley's Comet was recorded.

May 19, 1910: Halley's Comet Brushes Earth With Its Tail
Earth passes through the tail of Halley's comet. The anticipation of its arrival creates quite a stir. In some circles, the comet's unusually close approach is seen as a sign of impending doom, a notion the down-market press does little to dispel.

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