JANUARY 2, 1998


While it is impossible to know what astronomical discoveries will be made during 1998, there are nevertheless many things to look forward to that will undoubtedly change our views of the solar system and beyond.

NASA's series of Discovery Missions continues with the launch of Lunar Prospector, scheduled for January 5th, at 8:31 p.m. EST. In less than a week, it will be in orbit around the Moon. And by next month, it will be sending back data from its five instruments. Lunar Prospector will spend at least one year surveying the Moon. One question that the spacecraft may finally answer is whether there is indeed water within the perpetually shadowed craters at the Moon's poles.

Later this month, the Near Earth Asteroid Rendezvous (NEAR) spacecraft returns to Earth for a gravity assist to redirect the spacecraft toward its final destination, minor planet 433 Eros, which it will reach this time next year.

Then, there's the total solar eclipse of the Sun on February 26th, which will be visible from the (hopefully) sunny Caribbean.

In April, the Saturnbound Cassini probe will make its first planetary flyby on its seven-year journey to the ringed planet. It will pass our neighbor planet Venus, taking that opportunity to test its cameras and other instruments.

July sees the inaugural launch in NASA's New Millennium program, which focuses mainly on tests of advanced technologies. The first probe, Deep Space 1 will fly on a new, lighter version of the Delta rocket using only three strap-on solid-fuel boosters and a smaller third stage. DS 1's key experiment is its propulsion system: solar-electric propulsion, or "ion drive." In 1999 DS 1 will fly past minor planet McAuliffe (named for teacher Christa McAuliffe, who died aboard Space Shuttle Challenger) on its way to visit Mars and Comet West-Kohoutek-Ikemura in the year 2000.

In August, NASA will launch the centerpiece of its 1998 space-astronomy program: AXAF, the Advanced X-ray Astrophysics Facility. This revolutionary orbiting telescope will join Hubble and Compton as the third of the agency's Great Observatories. AXAF should produce much sharper pictures than any previous X-ray mission, with resolution comparable to images obtained in visible light by ground-based telescopes. AXAF also carries gratings that disperse the X-rays into a spectrum; it will be the first mission to study the X-ray universe with both sharp images and high spectral resolution. The observatory will fly into orbit aboard the Space Shuttle Columbia, where it will be released into a circular 300-kilometer- high orbit. Then, two solid rockets will take AXAF 60,000 km from Earth. The satellite's own liquid rockets then take over, and after several days it will orbit Earth between 10,000 and 140,000 km.

In October, the Far Ultraviolet Spectroscopic Explorer (FUSE) will be launched aboard a Delta rocket. Its 64-cm telescope will direct light onto a very high resolution spectrograph to allow astronomers to study the precise composition and temperature of stars and gas clouds, as well as use Doppler shifts to measure line-of-sight velocities accurately.

In November, the Leonid meteor shower could bring us the "meteor storm" astronomers have been waiting three decades to see.

At year's end, the Mars Surveyor 1998 lander will be launched. It and a companion orbiter, will reach the red planet in 1999.


Some daily events in the changing sky, from the editors of SKY & TELESCOPE.


* Look for Saturn shining to the upper left of the Moon this evening.

* Earth is at perihelion at 4 p.m. Eastern Standard Time, 91,403,425 miles from the Sun -- its closest of the year. This is 3.3 percent closer than we are to the Sun at the aphelion of our orbit in July.

* Latest sunrise of the year (for people near 40 degrees north latitude).


* First-quarter Moon (exact at 9:18 a.m. EST).

* Saturn is to the Moon's lower right.


* Mercury is at greatest elongation in the dawn (23 degrees west of the Sun).


* Some doorstep astronomy: By 8 p.m. the bright constellation Orion is high in the southeast (well to the Moon's lower left this evening). Look for Orion's three-star Belt in the constellation's middle. The Belt points down nearly to bright Sirius in Canis Major, and up nearly to orange Aldebaran in Taurus.


* Aldebaran shines to the Moon's lower left in early evening, and directly left of it later.

* The 4th-magnitude star Gamma Tauri in the Hyades is occulted by the Moon tonight for locations in the northern U.S. and Canada. See the timetable in the January Sky & Telescope, page 97.

* The eclipsing variable star Algol in Perseus should be at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 1:10 a.m. Eastern Standard Time Friday morning. It takes several hours to fade and brighten. For a complete schedule of Algol's minima, go to

* Latest start of morning twilight of the year (for people near 40 degrees north latitude).


* To the upper right of the waxing gibbous Moon early this evening is orange Aldebaran. Farther below the Moon is brighter orange Betelgeuse.


* Mira, the prototype long-period variable star, should be at its maximum brightness, about magnitude 3.4. Mira should be easily visible to the unaided eye. It's in the constellation Cetus and is marked on most constellation charts (including the monthly fold-out chart in Sky & Telescope). A map of comparison stars for estimating its brightness is in the February 1997 Sky & Telescope, page 66.

* Saturn's brightest satellite, Titan, is 3 or 4 ring-lengths east of the planet tonight through Tuesday night. A small telescope will show it.


MERCURY shines low in the dawn. Look just above the southeast horizon as morning twilight begins to brighten. Don't confuse Mercury with Antares, well to its upper right.

VENUS is the bright light (magnitude -4.4) low in the west-southwest during twilight. It's dropping lower every day now. Don't confuse it with Jupiter to its upper left. Pick up Venus in a telescope around sunset and you can see its very thin crescent phase, waning day by day.

MARS, quite dim at magnitude +1.2, appears between Venus and Jupiter.

JUPITER shines brightly (magnitude -2.0) in the southwest at dusk, to the upper left of Venus. It sets around 7:30 p.m.

SATURN, in Pisces, glows at magnitude +0.7 high in the south to southwest during evening.

URANUS and NEPTUNE are hidden in the glow of sunset.

PLUTO is low in the southeast before dawn.

(All descriptions that relate to the horizon or zenith are written for the world's midnorthern latitudes. Descriptions that also depend on longitude are for North America. Eastern Standard Time, EST, equals Universal Time minus 5 hours.)

More details, sky maps, and news of other celestial events appear each month in SKY & TELESCOPE, the essential magazine of astronomy. See our ever-growing Web site at Clear skies!

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