October 18
Orange and Blue
Sun Position
The Sun is in Libra near -12° declination. Autumn is now established across the Northern Hemisphere temperate zones; spring is fully underway in the Southern Hemisphere.
Sky Highlight
October evenings provide a good opportunity for double-star observing generally, as seeing conditions in autumn often improve compared to the turbulent summer air. Almach in Andromeda is among the finest color-contrast doubles visible in any small telescope and is well-placed on October evenings.
Deep Sky Object
M110 (NGC 205), a dwarf elliptical galaxy about 2.7 million light-years away. M110 is a satellite galaxy of M31, and unlike the compact M32 it is large, diffuse, and shows traces of recent star formation (unusual for a dwarf elliptical) hinting that its interaction with Andromeda has stirred up fresh stellar activity. Shares M31's October visibility window; best from Northern Hemisphere, accessible but low from southern mid-latitudes.
Featured Star
Almach (γ And) is an orange giant and blue main-sequence pair (K3IIb + B9.5V) about 355 light-years away, and the color contrast between the two visible components is among the sharpest of any named double star in the sky. The system is at minimum quadruple: the blue star has at least two additional spectroscopic companions orbiting it. Almach, orange and blue at Andromeda's foot, a quadruple star disguised.
Around This Date
- October 18, 1963France launched the cat Félicette on a suborbital space mission, making her the first and only feline in space; she was recovered successfully after the capsule parachuted down.
- October 20, 1968Apollo 7 splashed down in the Atlantic after eleven days in orbit, completing NASA's first crewed Apollo mission and certifying the command module for lunar missions.
Almach rewards looking twice, once to see it, and again with a telescope to see what once looked like one point of light is actually four.