December 19, 2024: The Andromeda Galaxy is excessive within the southern sky as twilight ends. Before dawn search for the moon close to the Sickel of Leo.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 7:14 a.m. CDT; Sunset, 4:22 p.m. CST. Check native sources for dawn and sundown instances. Times are calculated by the US Naval Observatory’s MICA laptop program.
Andromeda Galaxy
At this season on the finish of night twilight, the Great Andromeda Galaxy, cataloged as Messier 31 or M 31, is excessive within the southern sky. With vacation journey occurring, sky watchers could also be touring to or a minimum of by means of areas with decreased outside lighting then they could have at their properties. An alternative to see the galaxy is at hand.
This spectacular spiral galaxy could be very massive, a lot that it spills exterior even a decrease energy telescopic eyepiece. It is finest considered from a area with out outside gentle with out an optical help or up shut by means of a binocular.
The century mark of the announcement that the Andromeda Galaxy is a separate island of stars within the universe happens at yr’s finish. Before that, astronomers weren’t certain what the 1000’s of spiral nebulae represented – gasoline clouds in spiral patterns contained in the Milky Way or separate amalgamations of stars like our own residence galaxy.
Galactic Dimensions
Edwin Hubble discovered a particular class of stars in two spiral nebula that diverse in brightness in a rhythmic sample generally known as Cepheid variables.
These stars had been discovered within the Magellanic Clouds – now generally known as the Milky Way’s companion galaxies seen within the southern hemisphere – by Henrietta Levitt early within the final century. Since the celebs had been about the identical distance, their durations that had been longest had the best intrinsic brightness. Levitt’s detailed monitoring of those stars, yielded the period-luminosity relationship, now elementary to figuring out distances to close by galaxies.
E.E. Hertsprung calibrated Levitt’s idea to those Cepheid variables – named for the prototype Delta in Cepheus – to the close by variables within the Milky Way.
The precept was used to find out distances to stars within the galaxy and people globular clusters that revolve across the galactic middle exterior the galactic airplane.
Century after Announcement
Hubble discovered Cepheids in Andromeda and one other galaxy cataloged as M 33. His preliminary calculations confirmed that Andromeda was a minimum of 975,000 gentle years away, far past the identified edges of the Milky Way. While he was cautious to announce these measurements made in 1923, Hubble was satisfied to announce this distance at an astronomy convention that started on December 30, 1924. Refined observations positioned it round 2.2 million gentle years.
The Andromeda galaxy might be discovered throughout late autumn and early winter excessive within the southern sky. Look for the Great Square of Pegasus, 4 stars that make a big field. Apheratz, on the northeast nook of the sq., belongs to Andromeda, a constellation of two strains of stars extending from this nook.
Find Mirach, about 15° northeast (to the higher left) of Alpheratz. The galaxy is 7.7° west of that star. Place the star on the middle of the binocular subject and transfer it to the higher proper. A big fuzzy glob of sunshine strikes into the sphere – the Andromeda Galaxy!
Gibbous Moon, Sickle of Leo
An hour earlier than dawn this morning, the gibbous moon, 81% illuminated, is over midway up within the southwest and 10.9° to the suitable of Regulus, Leo’s brightest star. While the moon is vivid, search for the Sickle of Leo, a backwards query mark that outlines Leo’s head. The haunches and tail, marked by Denebola are to the east of the sickle.
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