Phy55

Homepage Image Archives

Week of Jan 7

This space image, taken by Michael Jäger in Austria in October, 2007
shows comet Holmes, the surprising “star” of our fall skies.
The comet, with a period of some six years, unexpectedly brightened by
a factor of 400,000 in October, going from an obscure object visible
only through powerful telescopes to a “naked eye” object, brighter
than most of the stars in the sky.
You can read more about the image here
and more about comet Holmes on Wikipedia.

Week of Jan. 14

This image of Mercury was taken by the
Messenger spacecraft, launched August 3, 2004.
Messenger is headed for Mercury and will
make its first flyby of the planet this Monday,
January 14. During our lecture (around 2pm)
Messenger will whiz a mere 200 miles from the planet's
surface. It will be the first spacecraft to visit Mercury
since 1975.

Week of Jan. 21

These are two of six or seven known multiexposures exhibiting the Analemma.  Both were produced by
exposing a camera at a fixed position at the same time of day throughout a year.   At a fixed time of
day the Sun will appear higher in the summer and lower in the winter as discussed in class. In
addition, since Solar days vary in length over the course of the year, the Sun also moves to
the right or left.  The image on the left was taken in the morning, the one on the right in the
afternoon.  A wonderful set of notes and animations explaining this phenomenon is
on the Analemma page.  A neat description of the production of the seventh analemma
(not shown here) by an amateur is here.

Week of Feb. 4

Have you ever seen the planet Mercury? Because Mercury orbits so close to the Sun,
it never wanders far from the Sun in Earth's sky. If trailing the Sun,
Mercury will be visible low on the horizon for only a short while after sunset.
If leading the Sun, Mercury will be visible only shortly before sunrise.
So at certain times of the year an informed skygazer with a little determination
can usually pick Mercury out from a site with an unobscured horizon.
Above, a lot of determination has been combined with a little digital trickery
to show Mercury's successive positions during March of 2000.
Each picture was taken from the same location in Spain when the Sun itself
was 10 degrees below the horizon and superposed on the single most photogenic sunset.

Like many of my favorite astronomical images, this appeared as the
Astronomy Picture of thDay for January 27, 2008.

Week of Feb. 11

This pretty collection of images of the Sun and the eight planets of
our Solar system has the nine largest bodies represented approximately
to scale. The images themselves were produced by various
space missions.

The compilation is due to Calvin J. Hamilton and may be
found, along with a lot of useful Solar System material
and other striking images, on his web page.

Week of Feb 18

These two images come from the announcement
February 15 of the discovery of the fourth and fifth exoplanets
discovered using the technique of gravitational lensing,
in which the presence of planets is inferred from the
effects of their gravitational attraction on the light from a
more distant star. The two newly discovered planets orbit a
smallish star about 5000 light-years from Earth.
The planets found form the first multiplanet system found
this way, and while both are gas giants about one-half
the size of Jupiter and Saturn, respectively, their orbits
lie far enough from the star that astronomers can
speculate about the existence of Earthlike planets in
closer orbits.

The image on the left is the data. This is a light-curve, plotting
the observed intensity of the more-distant star as a function of time
(measured horizontally in days). The increased intensity due to
lensing by the foreground star is evident. The details of the shape
of the curve reflect the presence of planets. Note the large number of
different observers (colors) from all over the world
who contributed to the curve. Many ofthese are amateur astronomers.
Why do the contributions for New Mexico and Auckland not overlap?

On the right is the speculation – an artist's conception of the
planetary system

Week of Feb 25

Eclipsed Moonlight
Credit & Copyright: Jerry Lodriguss (Catching the Light)

Explanation: Moon watchers blessed with clear skies over the Americas, Europe,
Africa and western Asia enjoyed a total lunar eclipse this week.
Catching eclipsed moonlight, astroimager Jerry Lodriguss offers this view
of the inspiring celestial event with the shadowed Moon accompanied by
wandering planet Saturn at the left, and bright Regulus, alpha star of the constellation Leo, above.
The engaging composite picture was made by combining a filtered, telephoto image of the Moon
and surrounding starfield with a telescopic exposure.
The combination dramatizes the reddened moonlight while clearly showing
the variation of brightness and color in Earth's not-so-dark shadow across the lunar surface.

Our skies were not as favorable as those shown here but those
inclined to look could still enjoy glimpses of the total lunar eclipse
of last Wednesday between the clouds. For those who did not,
this beautiful shot from the Asronomy Picture of the Day
archives will have to do for a while. Our next total lunar
eclipse will be in late 2010.

Week of Mar. 3

In this image from the TRACE satellite  taken in ultraviolet
light we see coronal matter lifted high above the
Sun by magnetic field lines.  The gas glows at
temperatures up to millions of degrees K.

Week of Mar. 14

This time-lapse image shows the rotation of the pinwheel nebula
WR104 over a period of eight months. The images were produced in
the near infrared by the Keck telescope on Mauna Kea. Hawaii.
The spiral is produced
by the colliding stellar wind from the two large, hot stars
that form this close binary. The collision leads to matter
being ejected along an axis rotating with the binary
system; the spiral structure forms much as does the
spiral plume of water from a rotating sprinkler.
The spiral structure shown extends about 200 AU from the
unresolved binary star.

The two members of the system are a type O star and a Wolf-Rayet
star. Both will end as supernovae; the WR star may produce a
Gamma Ray Burst. If directed along the axis of rotation of the
system, the effects on Earth at a distance of some 8000 ly
could be cataclysmic.

More information from the authors of the paper available .here

Week of Mar. 21

Molecular Cloud Barnard 68
Credit: FORS Team, 8.2-meter VLT Antu, ESO

Explanation: Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. It is possible to look right through the cloud in infrared light.

Once more, I found our weekly image as the March 23

installment of Astronomy Picture of the Day

Week of Mar 28

Across the Universe
Credit: NASA Swift Team, Stefan Immler (GSFC) et al.

Explanation: How far can you see? Even the faintest stars visible to the eye are merely hundreds or thousands of light-years distant,
all well within our own Milky Way Galaxy. Of course, if you know where to look you can also spot the Andromeda Galaxy as a pale,
fuzzy cloud, around 2.5 million light-years away. But staring toward the northern constellation Bootes on March 19th, even
without binoculars or telescope you still could have witnessed a faint, brief, flash of light from a gamma-ray burst.
The source of that burst has been discovered to lie over halfway across the Universe at a distance of about 7.5 billion light-years.
Now holding the distinction of the most distant object that could be seen by the unaided eye and the intrinsically brightest
object ever detected, the cosmic explosion is estimated to have been over 2.5 million times more luminous than
the brightest known supernova. The monster burst was identified and located by the orbiting Swift satellite,
enabling rapid distance measurements and follow-up observations by large ground-based telescopes.
The fading afterglow of the gamma-ray burster, cataloged as GRB080319B, is shown in these two
panels in X-rays (left) and ultraviolet light (right).

Once more, I found our weekly image as the March 28

installment of Astronomy Picture of the Day