Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://www.sai.msu.su/apod/open_clusters.html
Дата изменения: Unknown Дата индексирования: Sat Dec 22 01:31:27 2007 Кодировка: Поисковые слова: hst |
![]() |
Astronomy Picture of the Day |
APOD: 2006 January 9 - M45: The Pleiades Star Cluster
Explanation:
Perhaps the most famous star cluster on the sky, the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open clusters.
The Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the
above
photograph are the blue reflection nebulae
that surround the brighter cluster
stars.
Low mass, faint, brown dwarfs have also
been found in
the
Pleiades.
(Editors' note: The prominent
diffraction spikes are caused by the telescope itself and may be either distracting or provide aesthetic enhancement, depending on your point of view.)
APOD: 1997 January 28 - Open Cluster M50
Explanation:
Many stars form in clusters. Two types of
star clusters are visible in our Milky Way Galaxy:
open clusters and globular clusters.
Open clusters like M50, shown above,
typically contain hundreds of stars,
many of which are bright, young, and blue. In fact, most of the
bright blue stars in the above picture belong to M50,
but most of the dimmer, red stars do not. M50 lies about 3000
light-years from Earth and is about
20 light years across. Open clusters
tend to have irregular shapes and are mostly found in the plane of our Galaxy.
APOD: 2005 August 4 - Stars Young and Old
Explanation:
Galactic or
open star
clusters are relatively young
swarms of bright stars
born
together near the plane of our Milky Way Galaxy.
Separated by about a degree on the sky, two
nice
examples are M46
(upper left) 5,400 light-years in the distance
and M47
(lower right) only 1,600 light-years away toward
the nautical constellation
Puppis.
Around 300 million years
young M46
contains a few hundred stars in a region about 30 light-years
across.
Aged 80 million years,
M47 is a
smaller but looser cluster
of about 50 stars spanning 10 light-years.
But
this
portrait of stellar youth also contains
an ancient interloper.
The small, colorful patch of glowing gas in M46 is actually
the planetary nebula NGC 2438 - the
final phase in the life of a sun-like star billions
of years old.
NGC
2438 is estimated to be only 3,000 light-years distant
and likely represents a foreground object, only by chance appearing
along our line of sight to youthful M46.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings, and
Disclaimers
NASA Official: Jay Norris.
Specific rights apply.
A service of:
EUD at
NASA /
GSFC
& Michigan Tech. U.