Astronomy Picture of the Day |
APOD: 2005 February 7 - A Telescope Laser Creates an Artificial Star
Explanation:
What do you get when you combine one of the world's most
powerful telescopes
with a powerful laser?
An artificial star.
Monitoring fluctuations
in brightness of a genuine bright star can indicate how the
Earth's atmosphere is changing,
but many times no bright star exists in the direction where
atmospheric information is needed.
Therefore, astronomers have developed the ability to create an
artificial star where they need it -- with a
laser.
Subsequent observations of the
artificial laser guide star can reveal information so
detailed about the blurring effects of the Earth's atmosphere
that much of this blurring can be removed by rapidly flexing the mirror.
Such adaptive optic techniques allow high-resolution
ground-based observations of
real stars,
planets,
nebulae,
and the early universe.
Above, a laser
beam shoots out of the
Keck II 10-meter telescope on Mauna Kea in
Hawaii
in 2002, creating an artificial star.
APOD: 2006 May 14 - The Very Large Array of Radio Telescopes
Explanation:
The most photogenic array of
radio telescopes in the world has also
been one of the most productive.
Each of the 27
radio telescopes in the
Very Large Array (VLA) is the size of a
house and can be moved on train tracks.
The above pictured
VLA, inaugurated in
1980 is situated in
New Mexico,
USA.
The VLA has been used to discover
water on planet Mercury,
radio-bright coronae around ordinary stars,
micro-quasars in our Galaxy,
gravitationally-induced Einstein rings around distant galaxies, and
radio counterparts to cosmologically distant gamma-ray bursts.
The vast size of the
VLA has allowed astronomers to study the
details of super-fast cosmic jets, and even
map the center of our Galaxy.
An upgrade of the VLA is
being planned.
APOD: 1999 February 1 - The Subaru Telescope
Explanation:
Last week, Japan's new
Subaru Telescope
made its first observations of the sky.
The gray building housing Subaru is visible just left of the white
Keck domes near the photo's center.
Subaru is the latest in the
class of optical telescopes
using a mirror with a diameter greater than 8 meters.
Subaru's 8.3-meter primary is the
largest single-piece optical telescope mirror yet made,
and is so thin that its precise shape can be monitored and adjusted.
Subaru will be owned and operated by
Japan
but located at the top of
Hawaii's
Mauna Kea,
a dormant volcano famous for housing several of the
world's
leading telescopes.
APOD: 2003 September 9 - A Gemini Sky
Explanation:
Where will Gemini take us tonight?
It is dusk and Gemini North,
one of the largest telescopes on
planet Earth,
prepares to peer into the distant universe.
Gemini's flexible 8.1-mirror
has taken already effectively taken humanity to
distant stars,
nebulas,
galaxies, and
quasars, telling us about the geometry,
composition, and evolution of our universe.
The above picture is actually a composite of over
40 images taken while the Gemini dome rotated,
later adding an image of the star field taken
from the same location.
The Gemini dome is not transparent -- it only appears so
because it rotated during the exposures of this image.
The constellations of
Scorpius and Sagittarius can be seen above the dome, as well as the
sweeping band of our
Milky Way Galaxy,
including the direction toward the
Galactic center.
Gemini North's twin,
Gemini South,
resides in Cerro Pachn,
Chile.
This night, 2003 August 19,
Gemini North
took us only into the outer
Solar System,
observing
Pluto
in an effort to better determine the composition of its
thin atmosphere.
APOD: 2002 August 19 - Roque de los Muchachos Observatory
Explanation:
Above the clouds, atop an island off the coast of Africa,
a group of cutting-edge telescopes inspects the universe.
Pictured above are telescopes at
Roque de los Muchachos
Observatory on La Palma, one of the
Canary Islands,
Spain.
The site is one of the premier observing locations on Earth.
The telescopes pictured are, from left to right, the
Carlsberg Meridian Telescope, the 4.2-meter
William Herschel Telescope, the
Dutch Open Telescope, the
Swedish Solar Tower, the 2.5-meter
Isaac Newton Telescope, and the 1.0-meter
Jacobus Kapteyn Telescope.
Pioneering observations made recently by these telescopes include
stars and galaxies forming early
in our universe, comets breaking up,
and evidence for planets around
Sun-like stars.
APOD: 2000 October 30 - A Step Toward Gravitational Wave Detection
Explanation:
Accelerate a charge and you'll get
electromagnetic radiation: light.
But accelerate any mass and you'll get
gravitational radiation.
Light is seen all the time, but, so far,
a confirmed direct detection of
gravitational radiation has
yet to be made.
When absorbed,
gravitational waves (GWs) create a
tiny symmetric jiggle similar to squashing a
rubber ball and letting go quickly.
Separated detectors can be used to discern
GWs from everyday bumps.
Powerful astronomical GW sources would coincidentally
jiggle even detectors on opposite ends of the Earth.
Pictured above are the two-kilometer-long arms
of one such detector: the
LIGO Hanford Observatory in
Washington,
which recently achieved a
phase-lock milestone to future GW detection.
When it and its
sister interferometer in
Louisiana
come online in 2002, they may see a
GW sky so
strange it won't be immediately understood.
APOD mourns the recent passing of
Joseph Weber, a visionary thinker and pioneer in
gravitational wave detection.
APOD: 2000 August 17 - Mount Megantic Magnetic Storm
Explanation:
Plasma from the Sun and debris from a comet both
collided with planet Earth last Saturday morning triggering
magnetic storms
and a meteor shower in a
dazzling atmospheric spectacle.
The debris stream from comet Swift-Tuttle is
anticipated yearly, and
many skygazers
already planned to watch the peak of the
annual Perseids meteor shower in the
dark hours of August 11/12.
But the simultaneous,
widely reported
auroras were triggered by the chance arrival of
something much less predictable -- a solar
coronal mass ejection.
This massive bubble of energetic plasma was seen leaving
the active Sun's surface on August 9,
just in time to travel to Earth and disrupt the
planet's magnetic field triggering
extensive auroras during
the meteor shower's peak!
Inspired by the cosmic light show,
Sebastien Gauthier
photographed the
colorful auroral displays above the dramatic dome of the
Mount-Megantic
Popular Observatory
in southern Quebec, Canada.
Bright Jupiter and giant star Aldebaran can be seen
peering through
the shimmering northern lights at the upper right.
APOD: 2000 July 15 - Star Trails in Southern Skies
Explanation:
As the Earth spins on its axis, the stars seem
to
rotate around us.
This motion produces the beautiful concentric arcs traced out by the
stars in
this time exposure of the southern hemisphere night sky.
In the foreground is the dome of the
Anglo-Australian Telescope
in central New South Wales, Australia.
In the middle of the picture is the South
Celestial Pole, the projection of
Earth's axis of rotation into the southern sky.
While the bright star
Polaris lies conveniently close to the
North Celestial Pole, no bright star similarly marks
the pole in the south.
Still, the South Celestial Pole is easily identified in the picture
as the point in the sky
at the center of all the
star trail arcs.
APOD: 2000 April 10 - Aurora in Red and Yellow
Explanation:
The past week brought some spectacular aurora to northern skies.
These
aurorae were caused by a large interplanetary shock wave that
exploded from the Sun on April 4.
When the shock wave reached the Earth on April 6,
the resulting aurora
could be seen in clear skies as far south as
North Carolina.
As the
aurorae occurred high in the
Earth's atmosphere,
they were accompanied by an
unusual alignment of planets
far in the background.
Pictured above that night, an unusual
multicolored auroral display
graced the skies above the domes of the
Brno Observatory in the
Czech Republic.
APOD: 1998 November 24 - Seven Leonids Over Wise Observatory
Explanation:
More
Leonids
were visible at some places than others.
In Israel, early in the morning of 17 November,
it rained meteors though a clear sky.
Observers there reported a peak rate for the 1998 Leonid Meteor Shower
of about 600 meteors per hour.
Visible in the
above picture are no fewer than seven
Leonid meteors
occurring over just a few minutes.
(Can you find them all?)
The dome of the
Wise Observatory is visible on the right.
The Earth's rotation causes stars to
appear as arcs.
The
1998 Leonids might be remembered not for their numbers,
however, but for the unusually high fraction of
bright fireballs.
Another eventful
Leonid Meteor Shower is
forecast for the same time next year.
APOD: 1997 December 27 - Keck: The Largest Optical Telescopes
Explanation:
In buildings eight stories tall rest mirrors ten meters across that are
slowly allowing humanity to map the universe. Alone, each is the
world's
largest optical telescope: Keck.
Together, the twin Keck telescopes have the
resolving power of a single telescope 90-meter in diameter, able to discern
sources just milliarcseconds apart. Since
opening in 1992, the real power of Keck I (left) has been in its
enormous light-gathering ability - allowing
astronomers to study faint and
distant objects in
our Galaxy and the universe.
Keck II, completed last year, and its twin are located on the dormant volcano
Mauna
Kea,
Hawaii,
USA. In the distance is Maui's volcano Haleakala. One reason Keck was built was because of the
difficulty for astronomers to get funding for a smaller telescope.
APOD: 2000 July 7 - Sirius, Sun, Moon, and Southern Cross
Explanation:
>From left to right are the enclosures of
Yepun (ye-poon; Sirius),
Antu (an-too; Sun),
Kueyen (qua-yen; Moon),
and Melipal (me-li-pal; Southern Cross),
pictured here as
night falls at Paranal Observatory
in northern Chile.
These are the four 8.2 meter wide telescope units of the
European Southern Observatory's
Very Large Telescope (VLT).
ESO astronomers and engineers plan to
combine the light of
the individual units, achieving an equivalent
aperture
of 16.4 meters which will,
for a while,
constitue
the biggest telescope on
planet Earth.
Of course,
the individual telescopes also function independently.
Antu, Kueyen, and Melipal have already achieved first light with
Yepun expected to operate in 2001.
The telescope
names
come from the Mapuche
language.
They were unanimously chosen based on
the winning "name-the-telescopes" essay by 17-year old
Jorssy Albanez Castilla from
Chuquicamata near the city of Calama.
APOD: 2001 July 10 - Sudbury Indicates Nonstandard Particle Model
Explanation:
The Sudbury Neutrino Observatory (SNO) has
been detecting so few
neutrinos from the
Sun
that the
Standard Model of
fundamental particles in the universe may have to be revised.
Pictured above is the SNO as it was being built.
Now operating, this large sphere beneath
Canada is detecting nearly invisible particles called
neutrinos being emitted from the
center of the Sun.
SNO appears to be
measuring a rate expected for
all types of neutrinos combined but a decided
deficit for the
electron neutrino.
The results are being interpreted as bolstering
previous evidence
that different types of neutrinos are changing into each other.
The most popular model for
fundamental particles, known as the
Standard Model, did not predict such
schizophrenic neutrinos.
Implications include that
neutrinos have mass and therefore comprise some of the
dark matter in the universe,
although probably not a cosmologically significant amount.
APOD: 2003 June 23 - KamLAND Verifies the Sun
Explanation:
A large sphere beneath Japan has helped
verify humanity's understanding of the
inner workings of the Sun.
The KamLAND sphere, shown above
during construction in 2001, fails to
detect
fundamental particles called
anti-neutrinos that are known to be emitted by nearby nuclear
reactors around
Japan.
This triumphant failure can best be explained by
neutrinos oscillating between different types.
KamLAND's results bolster previous
neutrino oscillation claims including that from the
Sudbury detector, a similar
large sphere beneath
Canada designed to detect all
types of neutrinos from the
Sun.
Thus, leading astrophysicists now consider the long standing
solar neutrino deficit problem as finally solved.
A new mystery that replaces it is to find a new
Standard Model for
particle physics that fully explains
neutrino oscillations.
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.