Ring Galaxy AM 0644-741 from Hubble
Image Credit:
Hubble Heritage Team
(AURA /
STScI),
J. Higdon (Cornell)
ESA,
NASA
Explanation:
How could a galaxy become shaped like a ring? The rim of the blue galaxy
pictured on the right is an immense ring-like structure 150,000
light years in diameter composed of newly formed, extremely bright,
massive stars.
That galaxy,
AM 0644-741, is known as a
ring galaxy and was caused by an
immense galaxy collision.
When
galaxies collide,
they pass through each other -- their individual stars
rarely come into contact.
The
ring-like shape is the result of the
gravitational disruption
caused by an entire
small intruder galaxy passing through a large one.
When this happens, interstellar gas and
dust become condensed, causing a
wave of star formation
to move out from the impact point like a
ripple across the surface of a pond.
The intruder galaxy is just outside of the frame taken by the
Hubble Space Telescope.
This
featured image was taken to
commemorate the anniversary of
Hubble's launch
in 1990.
Ring galaxy AM 0644-741 lies about 300 million light years away.
Meteor in the Milky Way
Image Credit &
Copyright:
Marko Korosec
Explanation:
Earth's April showers include the
Lyrid Meteor Shower,
observed for more than 2,000 years
when the planet makes its annual passage
through the
dust stream of long-period Comet Thatcher.
A grain of that comet's dust, moving 48 kilometers per second
at an altitude of 100 kilometers or so,
is swept up in this night sky view from
the early hours of April 21.
Flashing toward the southeastern horizon,
the meteor's brilliant streak
crosses the central region of the rising Milky Way.
Its trail points back
toward the shower's radiant
in the constellation Lyra,
high in the northern springtime sky and off the top of the frame.
The yellowish hue of giant star Antares shines to
the right of the Milky Way's bulge.
Higher still is bright planet Saturn, near the right edge.
Seen from Istra, Croatia, the Lyrid meteor's
greenish glow reflects in the waters of the Adriatic Sea.
Colorful Star Clouds in Cygnus
Image Credit & Copyright:
André van der Hoeven
Explanation:
Stars can form in colorful surroundings.
Featured here
is a star forming region rich in glowing gas and dark dust toward the
constellation of the Swan (Cygnus), near the bright star Sadr.
This region,
which spans about 50 light years, is part of the
Gamma Cygni nebula which lies about 1,800 light years distant.
Toward the right of
the image is Barnard 344, a dark and twisted dust cloud rich in cool molecular gas.
A dramatic wall of dust and red-glowing
hydrogen gas forms a line down the picture center.
While the glowing red gas is indicative of small
emission nebulas, the blue tinted areas are
reflection nebulas --
starlight reflecting from usually dark dust grains.
The
Gamma Cygni nebula
will likely not last the next billion years, as most of the bright young
stars will
explode,
most of the dust will be destroyed,
and most of the gas will drift away.
Total Solar Eclipse over Svalbard
Image Credit & Copyright:
Thanakrit Santikunaporn
Explanation:
Going, going, gone.
That was the feeling in
Svalbard,
Norway
last month during a
total eclipse of the Sun by the Moon.
In the
featured image, the eclipse was captured every three minutes and then digitally merged with a foreground frame taken from the
same location.
Visible in the foreground are numerous gawking
eclipse seekers,
some deploying pretty sophisticated cameras.
As the Moon and Sun moved together across the sky --
nearly horizontally from this far north --
an increasing fraction of the Sun appears
covered by the Moon.
In the
central frame, the Moon's
complete blockage
of the disk of the Sun makes the immediate
surroundings appear like night during the day.
The exception is the Moon itself, which now appears surrounded by the
expansive corona
of the Sun.
Of course, about 2.5 minutes later, the surface of the Sun began to
reappear.
The next
total eclipse
of the Sun will occur in 2016 March and
be visible
from Southeast Asia.
The Great Crater Hokusai
Image Credit:
NASA,
Johns Hopkins Univ. APL,
Arizona State Univ., CIW
Explanation:
One of the largest young craters on Mercury,
114 kilometer (71 mile) diameter
Hokusai crater's bright
rays are known to extend across
much of the planet.
But this mosaic of oblique views focuses on Hokusai close up,
its sunlit
central peaks, terraced
crater walls, and
frozen sea of impact melt on the
crater's floor.
The images were captured by the MESSENGER spacecraft.
The first to orbit Mercury,
since 2011 MESSENGER has conducted
scientific explorations, including
extensive imaging of the
Solar System's innermost planet.
Now running out of propellant and unable to counter orbital
perturbations caused by the Sun's gravity,
MESSENGER is predicted to
impact
the surface of Mercury on April 30.
M46 Plus Two
Image Credit &
Copyright:
Denis Priou
Explanation:
Galactic or
open star clusters
are young.
These swarms of stars are born together near the plane of the Milky Way,
but their numbers steadily dwindle as cluster members are
ejected by galactic tides and gravitational interactions.
In fact,
this
bright open cluster, known as M46, is around 300 million years
young.
It still contains a few hundred stars within a span of
30 light-years or so.
Located about 5,000 light-years away toward the
constellation
Puppis, M46
also seems to contain contradictions to its youthful status.
In this pretty starscape,
the colorful, circular patch above and right of the center of M46
is the planetary nebula NGC 2438.
Fainter still, a second planetary nebula, PK231+4.1,
is identified
by the box at the right and enlarged in the inset.
Planetary nebulae are a brief, final phase in the life of a sun-like
star a
billion
years old or more,
whose central reservoir of hydrogen fuel has been exhausted.
NGC 2438
is estimated to be only 3,000 light-years distant, though, and
moves at a different speed than M46 cluster members.
Along with its fainter cohort, planetary nebula NGC 2438 is likely
only by chance
appearing near our line-of-sight to the young stars of M46.
One-Armed Spiral Galaxy NGC 4725
Image Credit &
Copyright:
Martin Pugh
Explanation:
While most spiral galaxies, including our
own Milky Way,
have two or more spiral arms, NGC 4725 has only one.
In this sharp color composite image,
the solo
spira mirabilis seems to wind
from a prominent ring of bluish, newborn star clusters and red
tinted star forming regions.
The odd galaxy also sports obscuring
dust lanes a yellowish central bar structure
composed of an older population of stars.
NGC 4725 is over 100 thousand light-years across and lies 41 million
light-years away in the well-groomed constellation
Coma
Berenices.
Computer
simulations
of the formation of single spiral
arms suggest that they can be either leading or trailing
arms with respect to a galaxy's
overall rotation.
Also included in the frame, sporting a noticably more traditional
spiral galaxy look, is a more distant background galaxy.
Mystic Mountain Dust Pillars
Image Credit:
Hubble Legacy Archive,
NASA,
ESA;
Processing & Copyright:
David Forteza
Explanation:
It's stars versus dust in the Carina Nebula and the stars are winning.
More precisely, the energetic light and winds from massive newly formed stars are evaporating and dispersing the
dusty stellar nurseries in which they formed.
Located in the
Carina Nebula and known informally as
Mystic Mountain,
these pillar's appearance is dominated by the dark dust
even though it is composed mostly of clear
hydrogen gas.
Dust pillars such as these are actually much thinner than air and only appear as
mountains due to relatively small amounts of
opaque interstellar
dust.
About 7,500 light-years distant, the featured image was taken with the
Hubble Space Telescope, digitally reprocessed by an industrious amateur, and highlights
an interior region of Carina which spans about three
light years.
Within a few million years, the stars will likely
win out completely and the entire dust
mountain will be destroyed.
Milky Way over Erupting Volcano
Image Credit & Copyright:
Sergio Montúfar
Explanation:
The view was worth the trip.
Battling
high winds,
cold temperatures, and
low oxygen, the
trek to
near the top of the volcano
Santa Maria in
Guatemala -- while carrying sensitive camera equipment -- was lonely and difficult.
Once set up, though, the camera captured
this breathtaking vista during the early morning hours of February 28.
Visible on the ground are six volcanoes of the
Central America Volcanic Arc, including
Fuego, the
Volcano of Fire, which is
seen erupting in the distance.
Visible in the sky, in separate exposures taken a few minutes later,
are many stars much further in the distance, as well as the
central band of our
Milky Way Galaxy situated horizontally overhead.
Sentinels of the Arctic
Image Credit & Copyright:
Niccolò Bonfadini
Explanation:
Who guards the north?
Judging from the above photograph, possibly giant trees covered in snow and ice.
The featured picture was taken a few winters ago in
Finnish Lapland
where weather can include sub-freezing temperatures and driving snow.
Surreal
landscapes sometimes result, where common trees become
cloaked in white and so appear, to some, as
watchful aliens.
Far in the distance, behind this uncommon
Earthly vista, is a more common sight -- a
Belt of Venus that divided a darkened from sunlit sky as the Sun rose behind the photographer.
Of course, in the spring, the trees thaw and
Lapland looks much
different.
NGC 2903: A Missing Jewel in Leo
Image Credit &
Copyright:
Tony Hallas
Explanation:
Barred spiral galaxy
NGC 2903 is
only some 20 million light-years distant.
Popular among amateur astronomers, it shines in the northern spring
constellation
Leo, near
the top of the lion's head.
That part of the constellation is sometimes seen as a
reversed question mark or sickle.
One of the brighter galaxies visible from the northern hemisphere,
NGC 2903 is surprisingly
missing
from Charles Messier's catalog of lustrous celestial
sights.
This
colorful image from a small ground-based telescope
shows off the galaxy's gorgeous spiral arms traced by young,
blue star clusters and pinkish star forming regions.
Included are intriguing details of
NGC 2903's bright core,
a remarkable mix
of old and young clusters with immense dust and gas clouds.
In fact,
NGC 2903 exhibits an exceptional rate of
star
formation activity near its center, also bright in radio,
infrared, ultraviolet, and x-ray
bands.
Just a little smaller than our own Milky Way,
NGC 2903 is about 80,000 light-years across.
Full Moon in Earth's Shadow
Image Credit &
Copyright:
Rolf Olsen
Explanation:
Last week the Full Moon was completely immersed in
Earth's dark
umbral shadow,
just briefly though.
The total phase of the
April 4, 2015
lunar eclipse lasted
less than 5 minutes, the shortest total
lunar
eclipse of the century.
In fact, sliding just within the Earth's umbral shadow's northern edge,
the lunar north stayed relatively bright, while a beautiful
range of blue and red hues emerged
across
the rest of the Moon's Earth-facing hemisphere.
The reddened light within the shadow that
reaches the lunar surface is filtered through the lower atmosphere.
Seen from a lunar perspective it comes from
all the sunsets and sunrises around the edges of the
silhouetted Earth.
Close to the shadow's edge, the bluer light is still
filtered through Earth's atmosphere, but
originates as rays of sunlight pass through layers high in
the upper stratosphere.
That light is colored by ozone that absorbs red light
and transmits bluer hues.
In this sharp telescopic view of totality from Auckland, New Zealand,
planet Earth, the Moon's north pole has been rotated to the
top of the frame.
Source -
NASA
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