Archive for August 24, 2020

08/24/2020 – Ephemeris – The Milky Way’s companion galaxies

August 24, 2020 Comments off

This is Bob Moler with Ephemeris for Monday, August 24th. Today the Sun will be up for 13 hours and 36 minutes, setting at 8:32, and it will rise tomorrow at 6:57. The Moon, 1 day before first quarter, will set at 11:51 this evening.

Not long after spiral nebulae were confirmed to be milky ways like ours or galaxies it was noticed that they were often found in bunches or clusters. One of the closest is the Virgo cluster seen in spring covering the constellation of Virgo and adjacent constellations. Our Milky Way Galaxy has two small satellite galaxies, the Clouds of Magellan first spotted by European eyes on his epic voyage, and belongs to a small cluster of galaxies along with the Great Andromeda galaxy. Perhaps 80 galaxies belong in all, most are small irregular dwarf galaxies, difficult to find and see. Our galaxy cluster is known simply as the Local Group. The galaxies of the Local Group interact gravitationally with each other.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


The Magellanic Clouds

The Small and Large Magellanic Clouds, these dwarf galaxies are seen best from the southern hemisphere. Credit: ESO S. Brunier.

The Great Andromeda Galaxy (M31). Image taken by Scott Anttila.

The Great Andromeda Galaxy (M31) is the largest member of the Local group with two of its satellite galaxies M32 to the left and M110 below-right. M31 can be spotted with the naked eye on fall and winter nights with the naked eye. Image taken by Scott Anttila.

M33, the Triangulum Galaxy

M33, the Triangulum Galaxy is the third largest galaxy in the Local Group after Andromeda and the Milky Way. It appears in the sky just east of the constellation of Andromeda in Triangulum the triangle. Though large it has a very low surface brightness making it hard to spot with binoculars or a telescope. Credit: Scott Anttila.

Virgo cluster

Some of the brighter members of the Virgo Cluster (of galaxies) as red ovals. The galaxies marked with an ‘M’ number are part of Charles Messier’s catalog. It took a telescope of 8 inch diameter for me to spot them. Someone with better vision, like Messier himself can spot them with a smaller telescope. Created using Cartes du Ciel (Sky Charts).