|
|
The Sun Spews X-rays
| Title |
The Sun Spews X-rays |
| Explanation |
Our Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ] is really very hot. The Sun's outer atmosphere is so hot that it emits much light in the X-ray [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#X-ray ] band, which was unexpected. X-rays are usually emitted from objects having a temperature in the millions of degrees, not the mere thousands of degrees of the Sun's surface. The above X-ray picture shows the Sun [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/sol.html ] one particularly active day in August of 1992. Evident are hot spots on the solar surface, showing that areas above the Sun [ http://www.hao.ucar.edu/public/slides/slides.html ]'s surface really do reach millions of degrees. But possibly more puzzling is the broader X-ray glow visible surrounding the Sun [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/sun.html ]. This glow is now attributed to the Sun's X-ray corona [ http://umbra.nascom.nasa.gov/spartan/the_corona.html ], the origin of which is currently a subject of much discussion and debate. The Sun [ http://spacelink.msfc.nasa.gov/Instructional.Materials/Curriculum.Materials/Sciences/Astronomy/Our.Solar.System/Our.Sun/The.Sun ] is one of the most photographed objects, with frequently updated pictures available [ http://umbra.nascom.nasa.gov/images/latest.html ] over the WWW. In fact, an X-ray picture from Yohkoh taken earlier today is usually available over the WWW. Compare it to the above picture! |
|
X-ray Transit Of Mercury
| Title |
X-ray Transit Of Mercury |
| Explanation |
This sequence of [ http://www.solar.isas.ac.jp/sxt_co/980626.html ] false color X-ray images captures a rare event - the passage [ http://www.arrakis.es/~xgarciaf/paso.htm ] or transit of [ http://www.dsellers.demon.co.uk/venus/ven_ch4.htm ] planet Mercury in front of the Sun. Mercury's small disk [ http://www.seds.org/nineplanets/nineplanets/mercury.html ] is silhouetted against the bright background of X-rays from the hot Solar Corona [ http://antwrp.gsfc.nasa.gov/apod/ap970217.html ]. It appears just to the right of center in the top frame and moves farther right as the sequence progresses toward the bottom. The dark notch is a coronal hole near the Solar South Pole [ http://ulysses.jpl.nasa.gov/ ], while a flaring coronal bright point can be seen to the left of the notch in the top frames. The frames were recorded [ http://www.lmsal.com/SXT/html2/Mercury_Transit_of_Solar_Corona.html ] on November 6, 1993 by the Soft X-ray Telescope [ http://www.lmsal.com/SXT/homepage.html ] on board the orbiting Yohkoh satellite [ http://www.lmsal.com/cgi-bin/yopos ]. Transits of Mercury (and Venus) were historically used to discover the geometry of the solar system [ http://beast.as.arizona.edu/textbook/text/CH03.html ] and to map planet Earth [ http://pacific.vita.org/pacific/cook/ ] itself. |
|
|
