Current Events in Astronomy

Week of November 28-December 4, 2000

Mars in the predawn sky Mars appears in the southeastern sky before dawn this week. View from Toronto, Ontario, about an hour before dawn on Thursday, December 7. Image created with Starry Night Backyardtm.

The Sky After Dark

A New Star in the Sky. NASA Science News; December 1, 2000. Space Shuttle Endeavour lifted off November 30, bearing a cargo of solar arrays to provide electrical power for the International Space Station. When deployed, the arrays will make the Space Station bigger and easier to see from Earth. Related story, more information:

Information about celestial events for the coming week can be found at the sites listed below.

(Universe 5th edition, Chapter 2, "Knowing the Heavens." Discovering the Universe 5th edition, Chapter 1, "Discovering the Night Sky.")

Earth's north magnetic pole, The arrow points to the current location of the Earth's magnetic North Pole, near Ellef Ringnes Island, Canada. NOAA.

Earth's North Magnetic Pole. Astronomy Picture of the Day; December 3, 2000. As you may know, your pocket compass doesn't actually point toward the true or geographic North Pole of the Earth (where Earth's rotation axis passes through the surface). Instead, it points to Earth's magnetic North Pole, which is offset about 11 degrees from the true North Pole. The magnetic pole wanders over an elliptical path, moving more than 40 meters northward each day. In fact, it has wandered over much of the Earth's surface in the 4.5 billion years since our planet formed. The aurora borealis (northern lights), caused by the solar wind striking Earth's magnetic field, is centered around the magnetic North Pole. Similarly, the aurora australis (southern lights) are centered around the magnetic South Pole. More information:

(Universe 5th edition, Chapter 8, "Our Living Earth," pages 208-211. Discovering the Universe 5th edition, Chapter 5, "Earth and Moon," pages 129-131.)

Layers of sedimentary rock in western Arabia Terra, Mars Layered sedimentary rock in Candor Chasma, Mars Global Surveyor images of evidence for flowing water on Mars in the distant past. Left: Hundreds of layers of sedimentary rock exposed by erosion on the floor of a 64-km-wide meteor crater in western Arabia Terra, Mars, attest to a dynamic early history for the red planet. Right: Layered sedimentary rock in Candor Chasma. These patterns could very well indicate that the materials were deposited in a lake or shallow sea. NASA-JPL/Malin Space Science Systems.

Evidence of Martian Land of Lakes Discovered. NASA-JPL; December 4, 2000. In what ultimately may be their most significant discovery yet, Mars scientists say high-resolution pictures showing layers of sedimentary rock paint a portrait of an ancient Mars that long ago may have featured numerous lakes and shallow seas. "We see distinct, thick layers of rock within craters and other depressions for which a number of lines of evidence indicate that they may have formed in lakes or shallow seas. We have never before had this type of irrefutable evidence that sedimentary rocks are widespread on Mars," said Dr. Michael Malin, principal investigator for the Mars Orbiter Camera on NASA's Mars Global Surveyor spacecraft. "These images tell us that early Mars was very dynamic and may have been a lot more like Earth than many of us had been thinking." Such layered rock structures where there were once lakes are common on Earth. The pancakelike layers of sediment compressed and cemented to form a rock record of the planet's history. The regions of sedimentary layers on Mars are spread out and scattered around the planet. They are most common within impact craters of Western Arabia Terra, the intercrater plains of northern Terra Meridiani, the chasms of the Valles Marineris, and parts of northeastern Hellas Basin rim. The scientists compare the rock layers on Mars to features seen in the American Southwest, such as the Grand Canyon and the Painted Desert of Arizona. Related stories, more information:

(Universe 5th edition, Chapter 12, "Red Planet Mars," pages 286-289. Discovering the Universe 5th edition, Chapter 6, "The Other Terrestrial Planets," pages 163-164.)

Trans-Neptunian object 2000 WR106 Trans-Neptunian object 2000 WR106. University of Arizona/Lunar and Planetary Laboratory.

Brightest Trans-Neptunian Object Discovered. University of Arizona; December 1, 2000. The  Spacewatch Project at the University of Arizona has discovered a minor planet in the outer reaches of the solar system that appears to be the brightest known such object other than Pluto. During routine scanning with the Spacewatch 0.9-meter telescope on November 28, observer R. S. McMillan was manually blinking the displayed scans in real time and noticed a relatively slow-moving object. The target, designated 2000 WR106, was then observed by J. A. Larsen, whose observing shift followed McMillan's. With their 12 observations spanning 3 nights, the Minor Planet Center determined a preliminary orbit by assuming the orbit is circular. As of December 1, the orbit suggests that this object is 43 AU from the Sun and 42 AU from Earth. With an apparent magnitude of 20 at those distances, the object would be the brightest known trans-Neptunian object (TNO) other than Pluto. Further observations of the object's position will be made in the coming weeks to allow the orbital parameters to be refined. was discovered in a moderately rich star field, closer to the galactic equator than where most TNOs are deliberately sought. Related stories, more information:

(Universe 5th edition, Chapter 16, "The Outer Worlds," pages 384-385. Discovering the Universe 5th edition, Chapter 7, "The Outer Planets," pages 196-199.)

Images of dark matter measurements
Mapping of the dark mass distribution in one of the 50 sky fields observed with the Very Large Telescope (VLT). Left: The original near-infrared mage. Right: The reconstructed map of the mass ("mass photo"), based on an analysis of the measured elongations and directions of the axes of the galaxy images in this field. The brighter areas indicate the directions in which there is most mass along the line of sight. The circle in the left photo surrounds the images of a distant galaxy cluster. The corresponding concentration of mass in the mass photo is the mass of that cluster. The mass photo shows the (mostly) dark matter responsible for the cosmic shear measured with the VLT. European Southern Observatory.

The VLT Weighs the Invisible Matter in the Universe. European Southern Observatory; December 1, 2000. An international team of astronomers has succeeded in mapping the dark matter in the universe, as seen in 50 different directions from Earth. They found that, within the uncertainty limits of the data, it is unlikely that mass alone would stop the current expansion of the universe. This fundamental result is based on the powerful, but challenging, method of "cosmic shear," which depends on very accurate measurements of the apparent weak distortion and preferential orientation of images of distant galaxies. This effect is caused by deflection of the light from those galaxies by the large mass concentrations in the universe it encounters on its way to us. The larger these masses are, the larger the apparent image distortions and the more pronounced the alignments of neighboring galaxy images. Related story, more information:

(Universe 5th edition, Chapter 25, "Our Galaxy," pages 625-628; Chapter 26, "Galaxies," pages 659-662; Chapter 28, "Cosmology: The Creation and Fate of the Universe," pages 712-715. Discovering the Universe 5th edition, Chapter 14, "The Milky Way Galaxy," pages 355, 356; Chapter 15, "Galaxies," page 375; Chapter 17, "Cosmology," pages 411-413.)

Quasar SDSS 1044-1025 XMM-Newton image of quasar SDSS 1044-1025, the most distant known quasar, with a redshift of 5.80. European Space Agency.

XMM-Newton Views the Remotest Quasar. European Space Agency; December 1, 2000. Quasars, the most luminous known objects in the universe, can emit 1000 times the energy of our entire galaxy, and this prodigious luminosity originates from objects only the size of our solar system. XMM-Newton has detected the X rays of the most distant known quasar, providing a view of the universe when it was less than 1 billion years old. The observation of this quasar is part of a project to determine the X-ray properties of the quasars with the highest redshift (and therefore the most distant and the "youngest"). The project hopes to learn whether these quasars are different from quasars in the local universe. Researchers also will learn more about the early hot universe. More information:

(Universe 5th edition, Chapter 27, "Quasars, Blazars, and Active Galaxies," pages 672-681. Discovering the Universe 5th edition, Chapter 16, "Quasars and Active Galaxies, pages 384-387.)

Circinus active galaxy Hubble image of the black-hole-powered core of a nearby active galaxy. The galaxy lies 13 million light-years away in the southern constellation Circinus. NASA/STScI.

Hubble Captures an Extraordinary and Powerful Active Galaxy. Space Telescope Science Institute; November 30, 2000. The Hubble telescope has taken a snapshot of a nearby active galaxy known as Circinus. This active galaxy belongs to a class of mostly spiral galaxies called Seyferts, which have compact centers and are believed to contain massive black holes. Seyfert galaxies are themselves part of a larger class of objects called Active Galactic Nuclei or AGNs. AGNs have the ability to remove gas from the centers of their galaxies by blowing it out into space at phenomenal speeds. Astronomers studying the Circinus galaxy are seeing evidence of a powerful AGN at its center. Much of the gas in the disk of the Circinus spiral is concentrated in two specific rings: a larger one with a diameter of 1300 light-years, and a previously unseen ring with a diameter of 260 light-years. In the Hubble image, the smaller inner ring is located on the inside of the green disk. The larger outer ring extends off the image and is in the plane of the galaxy's disk. Both rings are home to large amounts of gas and dust as well as areas of major "starburst" activity, where new stars are rapidly forming. At the center of the starburst rings is the Seyfert nucleus, believed to be the signature of a supermassive black hole that is accreting surrounding gas and dust. The black hole and its accretion disk are expelling gas out of the galaxy's disk and into its halo (the region above and below the disk). The detailed structure of this gas is seen as magenta-colored streamers extending toward the top of the image. Related stories: 

(Universe 5th edition, Chapter 27, "Quasars, Blazars, and Active Galaxies," pages 686-692. Discovering the Universe 5th edition, Chapter 16, "Quasars and Active Galaxies, pages 390-394.)