Caroline’s Cluster

NGC 2360 (Caroline's Cluster)

NGC 2360, Caroline’s Cluster (credit: Roberto Mura)

The constellation Canis Major, the Big Dog, contains a handful of splendid star clusters for observers with a small telescope. Messier 41 is the most famous and easiest to see. The lesser known NGC 2362 is fainter, but prettier. And the lovely star cluster NGC 2360 is always worth a careful gaze as it occupies a particularly rich section of the Milky Way. This open star cluster was first discovered by Caroline Herschel on February 26, 1783 using a small refractor. Her famous brother William Herschel included the cluster in a later catalog of 1000 deep-sky objects that he and his sister discovered. In her honor, the cluster is sometimes called “Caroline’s Cluster”.

Caroline’s Cluster is easy to find about 3.5º east of the blue-white star star γ Canis Majoris, sometimes called Muliphein, one of the three stars in the head of the Big Dog (see image below). At magnitude 7.2, the cluster is bright enough to spot in binoculars. It’s also compact, which means it has high surface brightness. So it’s easy to pick out even in moderately light-polluted skies.

Location of "Caroline's Cluster", NGC 2360, east of the head of Canis Major.

Location of “Caroline’s Cluster”, NGC 2360, east of the head of Canis Major.

In binoculars, NGC 2360 appears diffuse and unresolved and spans about half the size of the full Moon. The cluster lies embedded in a rich field of stars along the plane of the Milky Way. In a telescope, the cluster is cracked open into dozens of 9th to 12th magnitude stars that are centered around an elliptical core, which curved branches poking out to the east and west. About half a degree to the west lies a bright 5th-magnitude star which is not a member of the cluster.

The cluster is old for an open cluster, with an estimated age of about 2.2 billion years. So you see very few bright blue-white stars here. Such stars, which burn fast and die young, have long ago exploded or faded away.

NGC 2360 lies about 3,700 light years away.

 

Red Barns and the Physics of Dying Stars

The pigment in red paint is made from plentiful elements cooked inside dying stars (image credit: Ian Britton)

The pigment in red paint is made from plentiful elements cooked inside massive dying stars (image credit: Ian Britton)

Why are so many barns painted red? The answer to this seemingly simple question goes deep into the physics of massive stars at the end of their lives. In 2013, a Google employee named Yonatan Zunger posted a long explanation on his Google+ page.  Summarized here, Zunger explains that barns are painted red because red paint is cheap. And red paint is cheap because its made of Fe2O3 (red ochre) composed of iron and oxygen. And iron and oxygen are cheap because they are plentiful on Earth because they formed readily in the innards of massive stars when the end their lives as supernovae explosions.

[Read more…]

A Bright Nova in Sagittarius

Artist conception of a nova (NASA)

Artist conception of a nova (NASA)

A nova has flared up in the constellation Sagittarius, and it’s grown bright enough to see with the naked eye in the pre-dawn sky. As of this weekend, according to Sky and Telescope, the nova has reached an impressive magnitude 4.3 which is plenty bright enough to see without optical aid in clear sky. The flaring star has been officially named Nova Sagittarii 2015 No.2.

“Nova” is a pre-telescopic term which means “new star”, because a nova seems to appear in a place where no star appeared before.

[Read more…]

25th Anniversary of the ‘Pale Blue Dot’


In late 1980, the Voyager 1 spacecraft had completed its primary mission to explore Jupiter and Saturn and was continuing forward, heading out of the solar system towards interstellar space. Before it turned away from Earth forever, the astronomer Carl Sagan, sensing a unique opportunity, asked NASA to turn one of the spacecraft’s cameras towards Earth to take an image. NASA engineers refused. They were concerned an attempt to image Earth might damage the camera if it accidentally aimed at the Sun.

[Read more…]

Thor’s Helmet

Thors Helmet NGC2359-Quick-HancockThis blazing maelstrom is Thor’s Helmet, a cloud of interstellar gas and stellar entrails set alight by a hot, unstable star nearing the end of its days. In this image by astrophotographers Kim Quick and Terry Hancock, the color and structure of this emission nebula hint at its youth and unusual nature.

[Read more…]