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Faint, fuzzy object near Sirius is a star cluster


Tonight for January 9, 2015

A reader wrote: On November 4, I went to study the constellation Orion, but first I had to see the star Sirius. There was a glimmer below Sirius, and upon looking, it seemed to be a very nice comet. Has anyone else seen this? I am a newby … and would like someone to verify if they see this. I am quite up and excited.

It wasn’t a comet but very likely was a lovely star cluster called M41. It lies about four degrees almost exactly south of Sirius. So the identification as a comet was wrong, but it is a reasonable mistake. The nuclei of comets look like fuzzy patches, much like M41 in a small telescope.

The confusion with a comet and this cluster is not a new one. In the late 1700s, Charles Messier gave this object the number 41 on his list of “objects to avoid.” He was a comet hunter who wanted others to realize that this object, which looks like a comet, really isn’t.

Giovanni Batista Hodierna is said to have discovered M41 sometime before 1654, but it may have been known to individuals with particularly good vision throughout human history. The cluster – whose true diameter in space covers about 25 light-years – contains about 100 stars including several red giants. Like most open star clusters of this type, it is relatively young – probably between 190 and 240 million years old. By contrast, our sun is thought to be four-and-a-half billion years old.

At mid-northern latitudes, Sirius and M41 stay out till roughly 3 to 4 a.m. local time. If you’re an early riser, out and about during the predawn and dawn hours on Tuesday, January 8, 2013, look for the star Antares to light up the southeast sky. Antares, the brightest star in the constellation Scorpius, and the Scorpion never appear in the same sky with Orion. According to star lore, Orion and the Scorpion are archenemies, so the gods made sure to keep them at opposite ends of the sky.

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The bright star is Sirius in the constellation Canis Major, the Greater Dog. The star cluster M41 can be seen as a fuzzy object below right of Sirius. Photo by EarthSky Facebook friend Stacy Oliver Bryant. Thank you Stacy! View larger.

Meanwhile enjoy Orion, the star Sirius and M41 on these cold winter evenings. There are over 100 of the so-called Messier objects or M-objects known today. Today’s amateur astronomers consider them among the most prized objects to be viewed through binoculars and small telescopes. Here’s a list of M-objects. Advanced amateurs can observe them all and can earn a Messier certificate from the Astronomical League.

Bottom line: No matter where you are on Earth, look for the sky’s brightest star, Sirius, in the month of January. If your sky is dark enough, notice the faint fuzzy object near the bright star Sirius. This object is called M41, and it’s a distant cluster of stars.

Antares: Heart of the Scorpion