Telescopes Poised For View Of Halley`s

August 11, 1985|By Charlie Jean. Orlando Sentinel.

Halley`s comet, now just a faint blur among the stars, is accelerating in its dash to circle the sun and depart like a boomerang on its journey through space.

As the comet approaches, telescopes around the world are poised to record the visit of what 16th-Century theologian Martin Luther called this ``haughty and proud star.``

In history`s greatest assault on the mysteries of comets, the last of five spacecraft is scheduled for launch on Thursday. It joins four others in a mission to pry loose some of the ancient visitor`s secrets.

Obscured by the sun and its glare the last four months, Halley`s comet is steadily gaining speed and growing brighter as the sun`s gravity pulls it in. Before April, when it was lost from view, Halley`s comet could be seen only by the world`s largest telescopes, such as the one at Mt. Palomar Observatory near Pasadena, Calif., which first spotted its approach Oct. 16, 1982.

In April, because of the relative movements of Earth and comet, the sun cut off scientists` view of the comet. Now, because of the same relative movements, the comet is again visible as it appears to move away from the sun. Amateur astronomers now can join professionals in tracking and photographing the 100-billion-ton collection of celestial snow and rock.

Over the next two weeks, astronomers with detailed star charts and large telescopes (more than 10 inches in diameter) should begin picking up Halley`s faint glow.

The scientific dissection of Halley`s comet will be far more detailed this time than during its last pass in 1910.

Dr. Stephen Larson, planetary scientist at the University of Arizona, said all of the school`s astronomy resources will be used to gain new information about this and other comets.

The last of five spacecraft to be launched on a Halley`s inspection is Japan`s Planet-A, scheduled for liftoff on Thursday. It and another Japanese probe will study how the comet`s atmosphere and tail are influenced by solar wind, an electrically charged gas that bursts from the sun at almost 1 million miles an hour.

The other four craft will pass through the comet`s tail. They include the earlier Japanese probe, the Soviets` Vega-1 and Vega-2 and the European Space Agency`s Giotta. Guided by the Vegas, scientists hope to steer Giotta so that it can photograph Halley`s dark nucleus, the solid ice and dust that form its core, from 310 miles away.

``It`s going to be a very productive exploration of Comet Halley,`` said David Morrison, chairman of National Aeronautics and Space Administration`s

(NASA) Solar System Exploration Committee. ``Whenever you go someplace for the first time, that`s exceptionally exciting.``

To the chagrin of American scientists, the Jimmy Carter and Ronald Reagan administrations decided the United States could not afford to send a probe of its own. But NASA will study the comet from six U.S. satellites in orbits around Earth and Venus and in interplanetary space by using the space shuttle. Halley`s crossed Jupiter`s orbit in January and will move inside the orbit of Mars on Nov. 28. It will pick up speed until it careens around the sun at 122,000 m.p.h. at its closest approach Feb. 9.

In late October, with moonlight no longer interfering, smaller telescopes of 2 1/2 inches should be able to spot the speeding comet. In November, binoculars should do the job.

On the nights of Nov. 15 and 16, Sky & Telescope magazine says, Halley`s will pass just south of the Pleiades star clusters, the hazy ``Seven Sisters,`` which are easy to observe with the unaided eye in the evening eastern sky. On those two nights, it will appear to the right or lower right of Pleiades as a dim, fuzzy blob of light with no tail.

In December it will be barely visible to the naked eye under very dark conditions. It will be high in the southern sky.

In January, Halley`s brightens but falls lower and lower in the western sky until it`s lost from view.

It will reappear the last week in February in the east just before sunrise. It should have a bright head and possibly a long tail.

By March 20, it should sport a long tail in the southeastern sky just before dawn.

Halley`s comet should be at its best in April. Toward the end of the first week, when moonlight is no longer a problem, it will be as bright as it will get. It will be low in the southern sky and descend rapidly toward the horizon.

For the last half of April it returns to the evening sky after dusk, fading and shrinking. It will then begin its lonely journey back 3.2 billion miles from the sun to the far reaches of its orbit.

Halley`s comet can be followed with binoculars through May and with telescopes until early August, 1986.

After that, no one we know will set eyes upon it until 2061 or so.