Vulpecula com Ansere
is the name given by the
Polish astronomer Hevelius for this Little Fox with the Goose,
a constellation he invented in the seventeenth century. The sky
map seen here was published in 1690 in Uranographia, just
after the death of Johann Hevelius in 1687. Six other constellations
made their appearance with this book, too. They are Canes Venatici,
the hunting dogs, Lacerta, the lizard, Leo Minor, the lion cub,
Lynx, the lynx, Sextans Uraniae, the sextant of Urania, and Scutum
Sobieskii, the shield of the Polish hero-king, John Sobieski.
You can see that several of these names have been shortened in
modern use.
Vulpecula is a star group without any stories, because it was
made up to fill an otherwise vacant part of the sky. Hevelius
is reported to have said, “I wished to place a fox and a
goose in the space of the sky well fitted to it; because such
an animal is very cunning, voracious and fierce. Aquila and Vultur
are of the same nature, rapacious and greedy.”
When the Summer Triangle is high in the sky, you
can discover the fox by looking about halfway between Vega and Altair. But use
binoculars, because even the brightest star in Vulpecula—a red giant that’s
more than 200 light-years from Earth—is visible to the unaided eye only
if you’re watching the sky from a dark location. The constellation is broad,
25° from east to west, but narrow, 10° from north to south. It lies
to the north of Sagitta and Delphinus, south of Cygnus. Its brightest star is
only of magnitude 4.4, but since the plane of the Milky Way passes through,
there are a number of star fields that make it worth having a look.
The most interesting object is M27, the Dumbbell Nebula, which
can be caught in 7 × 50 binoculars as a fuzzy star. With
a small telescope it is a real gem.
The
first hint of what will become of our Sun was discovered inadvertently
in 1764. The 27th object on Messier's list, now known as M27 or
the Dumbbell Nebula, is a planetary nebula, the type of nebula
our Sun will produce when nuclear fusion stops in its core. M27
is one of the brightest planetary nebulae on the sky, and can
be seen in the constellation Vulpecula with binoculars. It takes
light about 1000 years to reach us from M27. Understanding the
physics and significance of M27 was well beyond 18th century science.
Even today, many things remain mysterious about bipolar planetary
nebula like M27, including the physical mechanism that expels
a low-mass star's gaseous outer-envelope, leaving an X-ray hot
white dwarf.
This vast cloud is a shell
of gas that was expelled from a dying star. It formed when a star
similar to our own Sun entered the late stages of its life. The
star first ballooned into a red giant—a cool star that’s
hundreds of times its previous size. The star then kicked its
outer layers into space. What remains of the star is extremely
hot, so it produces lots of energy—enough to make the expanding
shell of gas glow like a neon sign. The same fate awaits our own
Sun—about five billion years from now.
About ten years ago, a Japanese astronomy satellite recorded a
bright burst of X-rays from Vulpecula. From this research two
teams of astronomers reported a “new” star, now called
QZ Vulpeculae. Actually two stars bound together by mutual gravitational
pull, they’re about 14,000 light-years from Earth, and no
one had seen the system until 1988. One of the stars is massive
but dark. The other contains less mass, but it is barely visible
to large ground-based telescopes. Later, it was found that the
two stars orbit each other once every eight hours, which means
that they’re very close together.
And recently, two teams of astronomers independently measured
the speed of the visible star. The information suggests that the
dark companion is at least five times the mass of our Sun and
probably more, which means it’s almost certainly one of the
best black-hole candidates yet discovered.
The X-ray outburst ten years ago probably took place when the
black hole pulled matter from its companion. The matter formed
a disk around the black hole, which became hotter and hotter until
it exploded—heralding the presence of a black hole.
Fox, you have stolen the goose, give it back again!
Otherwise the hunters will get you with the shooting gun!
German nursery rhyme