Messier 44. The Beehive Cluster.



ABOUT
The Beehive Cluster, also known as Praesepe (Latin for "manger"), M44, NGC 2632, or Cr 189, is an open
cluster in the constellation Cancer. It is one of the nearest open clusters to the Solar System, and
it contains a larger star population than most other nearby clusters. Under dark skies the Beehive
Cluster looks like a nebulous object to the naked eye; thus it has been known since ancient times. The
classical astronomer Ptolemy called it "the nebulous mass in the breast of Cancer," and it was among
the first objects that Galileo studied with his telescope.

The cluster's age and proper motion coincide with those of the Hyades open cluster, suggesting that
both share a similar origin.[3][4] Both clusters also contain red giants and white dwarfs, which
represent later stages of stellar evolution, along with main sequence stars of spectral classes A, F,
G, K, and M.

The cluster's distance is often cited to lie between 160 to 187 parsecs (520-610 light years). The
2009 catalog of revised Hipparcos parallaxes for Praesepe members and the latest iteration of color-
magnitude diagram fitting in the infrared favor an analogous distance near 182 pc. There is better
agreement on its age, at about 600 million years. This is equivalent to the age of the Hyades (~625
million years). The bright central core of the cluster has a diameter of about 7 parsecs (22.8 light
years).

The Beehive is most easily observed when Cancer is high in the sky; in northern latitudes this occurs
during the evening from February to May. At 95 arcminutes across, the cluster fits well in the field
of view of a pair of binoculars or a telescope of low power.


History
Galileo was the first to observe the Beehive in a telescope, in 1609, and was able to resolve it into
40 stars. Charles Messier added it to his famous catalog in 1769 after precisely measuring its
position in the sky. Along with the Orion Nebula and the Pleiades cluster, Messier's inclusion of the
Beehive has been noted as curious, as most of Messier's objects were much fainter and more easily
confused with comets. One possibility is that Messier simply wanted to have a larger catalog than his
scientific rival Lacaille, whose 1755 catalog contained 42 objects, and so he added some bright,
well-known objects to boost his list.

Ancient Greeks and Romans saw this object as a manger from which two donkeys, the adjacent stars
Asellus Borealis and Asellus Australis, are eating; these are the donkeys that Dionysos and Silenus
rode into battle against the Titans. Philosopher Aratos of Soli (c310-c245 BC), in his poem
Phainomaina, called the cluster "the little mist"

This perceived nebulous object is the main celestial object in the 23rd lunar mansion (Hsiu Kuei or
Xiu Gui) of ancient Chinese astrology. Ancient Chinese skywatchers saw this as a ghost or demon riding
in a carriage and likened its appearance to a "cloud of pollen blown from willow catkins." It was also
known by the somewhat less romantic name of Tseih She Ke or "Exhalation of Piled-up Corpses".


Morphology and composition
Like many star clusters of all kinds, Praesepe has experienced mass segregation. This means that
bright, massive stars are concentrated in the cluster's core, while dimmer, less massive stars
populate its halo (sometimes called the corona). The cluster's core radius is estimated at 3.5 parsecs
(11.4 light years); its half-mass radius is about 3.9 parsecs (12.7 light years); and its tidal radius
is about 12 parsecs (39 light years). However, the tidal radius also includes many stars that are
merely "passing through" and not bona fide cluster members.

Altogether, the cluster contains at least 1000 gravitationally bound stars, for a total mass of about
500-600 Solar masses. A recent survey counts 1010 high-probability members, of which 68% are M dwarfs,
30% are Sun-like stars of spectral classes F, G, and K, and about 2% are bright stars of spectral
class A. Also present are five giant stars, four of which have spectral class K0 III and the fifth G0
III.

So far, eleven white dwarfs have been identified, representing the final evolutionary phase of the
cluster's most massive stars, which originally belonged to spectral type B. Brown dwarfs, however, are
extremely rare in this cluster, probably because they have been lost by tidal stripping from the halo.

The cluster has a visual brightness of magnitude 3.7. Its brightest stars are blue-white and of
magnitude 6 to 6.5. 42 Cancri is a confirmed member.


Planets
In September, 2012 two planets which orbit separate stars were discovered in the Beehive Cluster. The
finding was significant for being the first planets detected orbiting stars like Earth's Sun that were
situated in stellar clusters. Planets had previously been detected in such clusters, but not orbiting
stars like the Sun.

The planets have been designated Pr0201b and Pr0211b. The 'b' at the end of their names indicates that
the bodies are planets. The discoveries are what have been termed Hot Jupiters, massive gas giants
that, unlike the planet Jupiter, orbit very close to their parent stars.

The announcement describing the planetary finds, written by Sam Quinn as the lead author, was
published in the Astrophysical Journal Letters. Quinn's team worked with David Latham of the Harvard-
Smithsonian Center for Astrophysics, utilizing the Smithsonian Astrophysical Observatory's Fred
Lawrence Whipple Observatory.

 

Processing
CCD Stack and CS6

Exposure
Lum: 5x5min
RGB: 5x5

Calibration
Darks, bias and flats.

Filters
Astrodon LRGB E-series

Cooling temp
-20´ C

Mean FWHM
3.50"

SQM-L value
18.2

Date
March 2013

Location
Krigslida, Stockholm, Sweden.
N59 06 52.4    E 18 03 54.5

Image aqusition
CCD AutoPilot 5

Scope control
Sky X Pro Native drv, and Maxim DL with Astro-Physics V2 drv.

Telescope
TEC APO 140

Mount
Astro-Physics Mach 1 GTO

Camera
QSI 583 WSG-8

Guiding
OAG guiding with Lodestar Guider

Focus system
Starlight Micro Touch and Focus MAX.