Explanation:
Why does Enceladus have ice plumes?
The discovery of jets spewing water vapor and ice was
detected by the Saturn-orbiting
Cassini spacecraft in 2005.
The origin of the water feeding the jets, however, remained a
topic of research.
A leading hypothesis held that the source might originate
from a deep underground sea,
but another hypothesis indicated that it might just be ice melted off walls of deep rifts by the moon's
tidal flexing and heating.
Pictured above,
the textured surface of Enceladus is visible in the foreground,
while rows of plumes rise from ice fractures in the distance.
These jets are made more visible by the
Sun angle and the encroaching shadow of night.
Recent study of over a hundred images like this -- of geysers crossing
Enceladus' South Pole, together with regional heat maps,
indicate that
these plumes likely originate from a hidden sea,
incresaing the chance that this frosty globe might be
harboring life.
Explanation:
No place on Earth was safe.
Four billion years ago, during the
Hadean eon,
our Solar System was a dangerous shooting gallery of large and dangerous rocks and ice chunks.
Recent examination
of lunar and Earth bombardment data indicate that the entire surface of
the Earth underwent piecemeal upheavals, hiding our globe's ancient geologic history, and creating a battered world with no remaining familiar land masses.
The rain of devastation made it difficult for any life to survive, although
bacteria that could endure high temperatures had the best chance.
Oceans thought to have formed during this epoch would boil away after particularly heavy impacts, only to reform again.
The above artist's illustration depicts how Earth might have looked during this epoch, with
circular impact features
dotting the daylight side, and
hot lava flows visible in the night.
One billion years later, in a calmer Solar System, Earth's first
supercontinent formed.
Explanation:
These clouds of interstellar dust and gas
have blossomed 1,300 light-years away in the fertile
star fields of the
constellation
Cepheus.
Sometimes called the Iris Nebula,
NGC 7023
is not the only nebula in the
sky to evoke the imagery of flowers, though.
Still, this
deep telescopic view
shows off the Iris Nebula's range of
colors and symmetries in impressive detail.
Within
the Iris, dusty nebular material surrounds a hot,
young star.
The dominant color of the brighter reflection nebula is blue,
characteristic
of dust grains reflecting starlight.
Central
filaments of the dusty clouds glow with a faint reddish
photoluminesence as some dust grains
effectively
convert the star's invisible
ultraviolet
radiation to visible red light.
Infrared observations
indicate that this nebula may contain
complex carbon molecules known as
PAHs.
The pretty blue petals of the Iris Nebula span about six light-years.
Explanation:
Andromeda is the nearest major
galaxy to our own
Milky Way Galaxy.
Our Galaxy is thought to look much like
Andromeda.
Together these two galaxies dominate the
Local Group of galaxies.
The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it.
The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is frequently referred to as
M31
since it is the 31st object on
Messier's
list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there.
Although visible without aid, the
above image of M31 was taken with a standard camera
through a small telescope.
Much about M31
remains unknown, including how it acquired
its unusual
double-peaked center.
Explanation:
The Crab Pulsar, a city-sized, magnetized
neutron star
spinning 30 times a second,
lies at the center of this tantalizing wide-field image of the
Crab Nebula.
A spectacular picture of one of
our Milky Way's supernova remnants, it
combines optical survey data with X-ray data from the orbiting
Chandra Observatory.
The composite was created as part of a celebration of
Chandra's 15
year long exploration of the
high energy cosmos.
Like a
cosmic
dynamo
the pulsar powers
the X-ray and optical emission from the nebula,
accelerating charged particles to extreme energies to
produce the jets and rings glowing in X-rays.
The innermost ring structure is about a light-year across.
With more mass than the Sun and the density of an
atomic nucleus, the spinning pulsar is the collapsed core of the
massive star that exploded, while the nebula is the
expanding remnant of the star's outer layers.
The supernova explosion was witnessed in
the year
1054.
Explanation:
Shiny NGC 253
is one of the brightest spiral galaxies visible,
and also one of the dustiest.
Some call it the Silver Dollar Galaxy for its appearance in small
telescopes, or just the Sculptor Galaxy for its location within
the boundaries of the southern constellation Sculptor.
First swept up in 1783 by mathematician
and astronomer
Caroline Herschel,
the dusty island universe lies a mere 10 million light-years away.
About 70 thousand light-years across, NGC 253 is the largest member of
the Sculptor
Group of Galaxies, the nearest to our own
Local Group of Galaxies.
In addition to its spiral dust lanes, tendrils of dust seem to be
rising from a galactic disk
laced with young star clusters and star forming regions in
this
sharp color image.
The high dust content accompanies frantic star formation,
earning
NGC 253 the designation of a
starburst galaxy.
NGC 253 is also known
to be a strong source of high-energy
x-rays and gamma rays, likely due to massive black holes near
the galaxy's center.
A Sky Portal in New Zealand
Image Credit & Copyright: Petr Horálek
Image Credit & Copyright: Petr Horálek
Explanation:
To some, it may look like a portal into the distant universe.
To others, it may appear as the eye of a giant.
Given poetic license, both are correct.
Pictured above is a standard
fisheye view of the
sky -- but with an unusual projection.
The view is from a
perch in
New Zealand called
Te Mata Peak, a name that translates from the
Maori language
as "Sleeping Giant".
The wondrous panorama shows the
band of our
Milky Way Galaxy
right down the center of the sky, with the
Large and Small Magellanic Clouds visible to the right.
The red hue is atmospheric
airglow
that surprised the photographer as it was better captured by the camera than the eye.
The above image was taken two weeks ago as the photographer's sister, on the left, and an acquaintance
peered into the
sky portal.
The Horsehead Nebula from Blue to Infrared
Image Credit & Copyright: Optical: Aldo Mottino & Carlos Colazo, OAC, Córdoba; Infrared: Hubble Legacy Archive
Image Credit & Copyright: Optical: Aldo Mottino & Carlos Colazo, OAC, Córdoba; Infrared: Hubble Legacy Archive
Explanation:
One of the most identifiable nebulae in the sky,
the Horsehead Nebula in Orion, is part of a large, dark,
molecular cloud.
Also known as Barnard 33, the unusual shape was first
discovered on a
photographic plate in the late 1800s.
The red glow originates from
hydrogen
gas predominantly behind the nebula, ionized by the nearby bright star
Sigma Orionis.
The darkness of the
Horsehead is caused mostly by thick
dust,
although the lower part of the
Horsehead's neck casts a shadow to the left.
Streams of gas leaving
the nebula are funneled by a strong
magnetic field.
Bright spots in the
Horsehead Nebula's base are
young stars just in the process of forming.
Light takes about 1,500 years to reach us from the
Horsehead Nebula.
The above image is a digital combination of images taken in blue, green, red, and
hydrogen-alpha light from the
Argentina, and an
image taken in
infrared light by the orbiting
Hubble Space Telescope.
Source - NASA
