Transcript X-ray Astronomy

X-ray Astronomy
The astmosphere is opaque to Xrays (good thing, too!)
This ROSAT PSPC falsecolor image is of a
portion of a nearby
stellar wind superbubble
(the Orion-Eridanus
Bubble) stretching
across Eridanus and
Orion.
• Soft X-rays are emitted by hot gas (T ~ 2-3 MK) in the interior of the
superbubble. This bright object forms the background for the "shadow"
of a filament of gas and dust. The filament is shown by the overlaid
contours, which represent 100 micron emission from dust at a
temperature of about 30 K as measured by IRAS. Here the filament
absorbs soft X-rays between 100 and 300 eV, indicating that the hot gas
is located behind the filament. This filament may be part of a shell of
neutral gas that surrounds the hot bubble. Its interior is energized by UV
light and stellar winds from hot stars in the Orion OB1 association.
These stars energize a superbubble about 1200 lys across which is
observed in the optical (Hα) and X-ray portions of the spectrum.
Chandra Xray
Observatory
inside the
Space Shuttle
payload bay
Three structures around Eta Carinae are thought to
represent shock waves produced by matter rushing
away from the superstar at supersonic speeds.
• The temperature of the shock-heated gas ranges from 60 MK in the
central regions to 3 MK on the horseshoe-shaped outer structure. "The
Chandra image contains some puzzles for existing ideas of how a star
can produce such hot and intense X-rays," says Prof. Kris Davidson of
the University of Minnesota.[21] Davidson is principal investigator for the
Eta Carina observations by Hubble. "In the most popular theory, X-rays
are made by colliding gas streams from two stars so close together that
they'd look like a point source to us. But what happens to gas streams
that escape to farther distances? The extended hot stuff in the middle of
the new image gives demanding new conditions for any theory to meet."
Appropriately
famous for its
broad ring of
obscuring dust and
hat-like
appearance, the
Sombrero Galaxy
(aka spiral galaxy
M104) is featured
in this unique
composite view
that spans the
electromagnetic
spectrum, from
three major spacebased
observatories.
•
Exploring the Sombrero's high-energy x-ray emission (blue), the Chandra contribution highlights
the pervasive, tenuous, hot gas that extends some 60,000 light-years from the galaxy's center.
Hubble's optical view (green) shows the more familiar emission from the Sombrero's population
of stars, seen from a nearly edge-on perspective and noticeably bulging at the galaxy's bright
core. The broad ring of dust that blocks light in other bands, glows in the infrared contribution
(red) from the Spitzer Space Telescope. The Sombrero Galaxy is about 28 million light-years
away, near the southern edge of the extensive Virgo cluster of galaxies.
X-ray Mirror
Major questions in X-ray
astronomy
• Stellar magnetic fields
• Extrasolar X-ray source astrometry
• Solar X-ray astronomy:
– Coronal heating problem
– Coronal mass ejection
X-rays can also be used for
spectroscopy:
What are the atoms ?
• X-rays penetrate, and are much smaller than light
• New instruments called "micro calorimeters" are being
developed which will be able to resolve individual lines
which make up a single peak with today's spectrometers.
With this higher spectral resolution, the strengths of lines
that are much closer together in wavelength will be able
to be used to compute conditions in the remnant such as
temperature and density. With the help of these new
instruments we will be able to say with greater
confidence what the progenitor stars were made of and
what the conditions of the remnant are like now.