October 3
The Ghost in the Glare
Sun Position
The Sun is in Libra near -4.5° declination. Equal-day regions are now a memory; the Northern Hemisphere is losing roughly two minutes of daylight each evening, while the Southern Hemisphere gains the same.
Sky Highlight
The Andromeda Galaxy (M31) reaches a favorable evening position in October, high enough for dark-sky observers to trace its full extent with the naked eye. Its satellite galaxies M32 and M110 are also well-placed. Northern Hemisphere observers have the best angle; from southern mid-latitudes it is visible but lower.
Deep Sky Object
M31 (Andromeda Galaxy), a spiral galaxy about 2.5 million light-years away. M31 is the nearest large spiral galaxy and the most distant object visible to the naked eye under dark skies, its light set out before our species existed, crossing 2.5 million light-years to arrive at your eye tonight. Best viewed from Northern Hemisphere and low northern latitudes in autumn; southern observers can see it but it transits low.
Featured Star
Mirach (β And) is a red giant (M0IIIab) roughly 197 light-years away, and it serves a practical navigational role: star-hop from Mirach perpendicularly to find M31, the Andromeda Galaxy, and M33 in Triangulum. Lurking close to Mirach in images is a background galaxy called Mirach's Ghost, nearly hidden in the star's scattered light. Mirach, the guide to Andromeda's galaxy, haunted by a ghost in its glare.
Around This Date
- October 3, 1942Germany conducted the first successful launch of an A-4 ballistic missile (later called the V-2) from Peenemünde, the first human-made object to reach the boundary of space.
- October 5, 1923Edwin Hubble photographed the Andromeda Nebula on a plate that he later marked 'VAR!', identifying a Cepheid variable that would prove it was a separate galaxy far outside the Milky Way.
Mirach is one of those stars that earns its place not by brilliance alone, but by where it points.