Spacecraft Rosetta Shows Comet has Two Components
Image Credit:
ESA/Rosetta/MPS
for OSIRIS Team;
MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Explanation:
Why does this comet's nucleus have two components?
The
surprising discovery that
Comet 67P/Churyumov–Gerasimenko has a double nucleus came
late last week as
ESA's robotic interplanetary spacecraft
Rosetta continued
its approach toward the ancient comet's core.
Speculative ideas on how the double core was created include, currently, that
Comet Churyumov–Gerasimenko is actually the result of the merger of two comets, that
the comet is a
loose pile of rubble pulled apart by
tidal forces,
that ice evaporation on the comet has been asymmetric,
or that the comet has undergone some sort of explosive event.
Pictured above,
the comet's unusual 5-km sized comet nucleus is seen rotating over the
course of a few hours, with each frame taken 20-minutes apart.
Better images -- and hopefully more refined theories -- are expected as
Rosetta
is on track to enter orbit around
Comet Churyumov–Gerasimenko's nucleus early next month,
and by the end of the year, if possible,
land a probe on it.
The Moon Eclipses Saturn
Image Credit & Copyright:
Carlos Di Nallo
Explanation:
What happened to half of Saturn?
Nothing other than Earth's Moon getting in the way.
As pictured above on the far right,
Saturn is partly eclipsed by a dark edge of a Moon itself only
partly illuminated by the Sun.
This year the orbits of the
Moon and Saturn have led to an
unusually high number of alignments of the ringed giant behind Earth's largest satellite.
Technically termed an
occultation, the
above image captured one such
photogenic juxtaposition from
Buenos Aires,
Argentina that occurred early last week.
Visible to the
unaided eye
but best viewed with binoculars, there are still four
more eclipses of Saturn by our Moon left in 2014.
The next one will be on August 4 and
visible from Australia,
while the one after will occur on
August 31 and be visible from western Africa at night but
simultaneously from much of eastern North America during the day.
Manhattanhenge: A New York City Sunset
Image Credit & Copyright:
Neil deGrasse
Tyson
(AMNH)
Explanation:
This coming Saturday, if it is clear, well placed New Yorkers can
go outside at sunset and watch their city act like a modern version of
Stonehenge.
Manhattan's streets will flood dramatically with
sunlight just as the Sun sets precisely at each street's western end.
Usually, the
tall buildings
that line the gridded streets of
New York City's tallest borough will hide the setting Sun.
This effect makes
Manhattan
a type of modern
Stonehenge,
although only aligned to about 30
degrees east of north.
Were
Manhattan's road grid perfectly aligned to east and west,
today's effect would occur on the
Vernal and
Autumnal Equinox,
March 21 and September 21, the only two days that the
Sun rises and sets due east and west.
Pictured above in this horizontally stretched image,
the Sun sets down
34th Street as
viewed from
Park Avenue.
If Saturday's sunset is hidden by clouds
do not despair -- the same thing happens twice each year:
in late May and mid July.
On none of these occasions, however, should you ever
look directly at the Sun.
Spotty Sunrise over Brisbane
Image Credit &
Copyright:
Stephen Mudge
Explanation:
In this composite cityscape,
dawn's
first colors backdrop the
lights along Brisbane's skyline
at the southeastern corner of Queensland, Australia,
planet Earth.
Using a solar filter, additional exposures made every 3.5 minutes
follow the winter sunrise on July 8 as
planet-sized
sunspots cross the
visible solar disk.
The sunspots mark
solar active regions with convoluted
magnetic fields.
Even as the maximum in the
solar
activity cycle begins to fade, the active regions produce intense
solar
flares and eruptions launching coronal mass ejections (CMEs),
enormous clouds of energetic particles, into
our fair solar system.
SN 1006 Supernova Remnant
Image Credit:
NASA,
ESA,
Zolt Levay (STScI)
Explanation:
A new star, likely the brightest supernova
in recorded human history, lit up
planet Earth's sky in the year 1006 AD.
The expanding debris cloud from the stellar explosion,
found in the southerly constellation
of
Lupus,
still puts on a cosmic light show across the
electromagnetic spectrum.
In fact,
this
composite view includes
X-ray data in blue from the
Chandra Observatory,
optical data in
yellowish hues, and radio image data in red.
Now known as the SN 1006
supernova remnant, the debris cloud
appears to be about 60 light-years across and is understood
to represent the remains of a white dwarf star.
Part of a
binary star system,
the compact white dwarf gradually
captured material from its companion star.
The buildup in mass finally triggered a
thermonuclear
explosion that destroyed the dwarf star.
Because the distance to the supernova remnant is about 7,000
light-years, that explosion actually
happened 7,000 years before the light reached Earth in 1006.
Shockwaves in the remnant
accelerate
particles to extreme energies and are
thought to be a source of the mysterious
cosmic rays.
M106 Across the Spectrum
Image Credit:
X-ray -
NASA / CXC / Caltech /
P.Ogle et al.,
Optical - NASA/STScI,
IR - NASA/JPL-Caltech,
Radio - NSF/NRAO/VLA
Explanation:
The spiral arms of bright, active galaxy M106 sprawl through this
remarkable
multiwavelength portrait, composed of image data
from radio to X-rays,
across
the electromagnetic spectrum.
Also known as NGC 4258,
M106 can be found
toward the northern constellation
Canes
Venatici.
The
well-measured
distance to M106 is 23.5 million light-years, making this cosmic scene
about 60,000 light-years across.
Typical in grand spiral galaxies, dark dust lanes,
youthful star clusters, and star forming
regions
trace spiral arms
that converge on a bright nucleus.
But this composite highlights
two anomalous arms in radio (purple)
and X-ray (blue) that seem to arise in the
central region of M106,
evidence
of energetic jets of material blasting into the galaxy's disk.
The jets are likely powered by matter falling into a
massive
central black hole.
NGC 4651: The Umbrella Galaxy
Image Credit &
Copyright:
R Jay Gabany
(Blackbird Observatories)
Collaboration:
C.Foster (Australian Astronomical Obs.),
H.Lux (U. Nottingham, Oxford),
A.Romanowsky (San Jose State, UCO),
D.Martínez-Delgado (Heidelberg),
et al.
Explanation:
Spiral galaxy NGC 4651 is a mere 62 million light-years distant,
toward the well-groomed northern constellation
Coma
Berenices.
About the size of our Milky Way, this island universe is seen to have
a faint umbrella-shaped structure that
seems to extend (left) some 100 thousand light-years
beyond the bright galactic disk.
The
giant cosmic umbrella is now known to be composed of
tidal star streams -
extensive trails of stars
gravitationally
stripped
from a smaller satellite galaxy.
The small galaxy was eventually
torn apart in repeated encounters as
it swept back and forth on eccentric orbits through NGC 4651.
In fact,
the picture insert zooms in on the smaller galaxy's remnant core,
identified in an extensive
exploration
of the system,
using data from the large Subaru and Keck telescopes
on Mauna Kea.
Work begun by a remarkable collaboration of amateur and professional
astronomers to image faint structures around bright galaxies
suggests that
even in nearby galaxies,
tidal star streams are common markers of
such galactic mergers.
The result is
explained by models
of galaxy formation that also apply to
our own
Milky Way.
Auroras over Northern Canada
Image Credit &
Copyright:
Kwon, O Chul
(TWAN)
Explanation:
Gusting
solar winds
and
blasts of charged particles from the Sun
resulted in several rewarding nights last December for those anticipating
auroras.
The
above image
captured dramatic auroras stretching across a sky near the town of
Yellowknife in
northern
Canada.
The
auroras
were so bright that they not only
inspired awe,
but were easily visible on an image exposure of only 1.3 seconds.
A
video taken concurrently shows the dancing sky lights evolving in real time as tourists, many there just to see
auroras, respond with cheers.
The
conical dwellings
on the image right are
teepees,
while far in the background, near the image center, is the
constellation of Orion.
The Moon Eclipses Saturn
Image Credit & Copyright:
Carlos Di Nallo
Explanation:
What happened to half of Saturn?
Nothing other than Earth's Moon getting in the way.
As pictured above on the far right,
Saturn is partly eclipsed by a dark edge of a Moon itself only
partly illuminated by the Sun.
This year the orbits of the
Moon and Saturn have led to an
unusually high number of alignments of the ringed giant behind Earth's largest satellite.
Technically termed an
occultation, the
above image captured one such
photogenic juxtaposition from
Buenos Aires,
Argentina that occurred early last week.
Visible to the
unaided eye
but best viewed with binoculars, there are still four
more eclipses of Saturn by our Moon left in 2014.
The next one will be on August 4 and
visible from Australia,
while the one after will occur on
August 31 and be visible from western Africa at night but
simultaneously from much of eastern North America during the day.
Alicante Beach Moonrise
Image Credit &
Copyright:
José Carlos González
Explanation:
In this beach and skyscape from Alicante, Spain,
July's Full Moon shines in the dark blue twilight,
its reflection coloring the
Mediterranean waters.
Near the horizon, the moonlight is reddened by
its long path through the atmosphere, but this
Full Moon was also near perigee, the closest point to
Earth along
the Moon's elliptical orbit.
That made it a Supermoon,
a mighty 14% larger and 30% brighter
than a Full Moon at apogee, the Moon's farthest orbital swing.
Of course, most warm summer nights are a good time
to enjoy a family meal oceanside,
but what fish do you catch on the night
of a Supermoon?
They must be Moon breams.
A Solar Filament Erupts
Image Credit:
NASA's
GSFC,
SDO AIA Team
Explanation:
What's happened to our Sun?
Nothing very unusual -- it just
threw a filament.
Toward the middle of 2012, a long standing
solar filament
suddenly erupted into space producing an energetic Coronal Mass Ejection (CME).
The filament had been held up for days by the Sun's ever changing
magnetic field
and the timing of the eruption was unexpected.
Watched closely by the Sun-orbiting Solar Dynamics Observatory, the resulting
explosion
shot electrons and ions into the Solar System, some of which arrived at Earth three days later and impacted Earth's
magnetosphere, causing visible
aurorae.
Loops of plasma surrounding an
active region can be seen above the erupting filament in
the ultraviolet image.
Over the past week the number of sunspots visible on the Sun unexpectedly
dropped to zero, causing speculation that
the Sun
has now passed a very
unusual
solar maximum,
the time in the
Sun's 11-year cycle
when it is most active.
Source - NASA
