Celestial Spectacle
As Comet Hale-Bopp blazes its way across the sky as possibly the brightest comet of the 20th century, sky watchers can catch a glimpse of cosmic history right from their backyards. It can be seen with the naked eye, but is most dramatically viewed through binoculars or a small telescope. Getting away from city lights allows for viewing of the full length of the comet’s streaming tail.
But catch Hale-Bopp now, because it won’t return until the year 4357. It has been traveling in the nether reaches of the solar system and was last seen about 2200 B.C. The comet was discovered in July 1995, when it was beyond the orbit of Jupiter, by two astronomers who were stargazing 400 miles apart. Professional astronomer Alan Hale in New Mexico and amateur astronomer Thomas Bopp in Arizona are credited with discovering C/1995 O1, Hale-Bopp’s formal title.
As it makes its way through the solar system, Hale-Bopp will speed toward the sun and away again. Along the way, it will provide scientists with rare insight into the solar system’s origins. “All this material [that makes up the comet] was present when the solar system was forming,” said Griffith Park astronomer Patrick So. “Finding out what comets are made of gives astronomers some idea of what formed the solar system 4.5 billion years ago.”
Composition of a Comet
Nucleus: A comet’s nucleus, often referred to as a “dirty snowball,” is a mix of ice, silicate dust and sometimes frozen carbon dioxide and carbon monoxide. The nucleus usually measures 5 to 10 miles across, but Hale-Bopp’s is much larger, an estimated 25 miles in diameter.
Makeup of nucleus
Gases and water: 70-80%
Meteroic particles: 20-30%
Coma: As a comet nears the sun, heat causes the outer layers of icy nucleus to evaporate. A fuzzy cloud of dust and gas is formed and can measure a million miles across.
Gas tail: Solar wind blows coma material back behind the nucleus, creating a tail. Coma material becomes electrically charged as the sun’s heat breaks down gas molecules from the nucleus into ions. Solar wind repels the ions away from the sun.
Hale-Bopp’s Orbit
Unlike the more circular orbit of a planet, a comet’s orbit around the sun is a long and narrow ellipse. Some comets orbit in periods of less than seven years. Others, like Hale-Bopp, pass the sun only once in thousands of years. Hale-Bopp’s orbit is extremely long--about 10 times the distance between Pluto and the sun.
COMET FACTS
Why It Gets Brighter: The point in the comet’s orbit when it’s closest to the sun is called perihelion. Hale-Bopp will reach perihelion on Tuesday, when it will be 85 million miles from the sun. It will probably be at its most active on this date, as more gas and dust are driven off the nucleus.
Comet Rotation: Hale-Bopp is on about an 11-hour rotation. It is spinning faster than most comets, which usually take a few days to make a complete rotation. In addition, scientists are noticing a dramatic spiral pattern of gas radiating from the nucleus.
How to View It
The best time to see the comet from now through May is early evening, above the northwest horizon. Shown below is its position about a hour and a half after sunset. Sun sets today at 6:13 p.m. in Los Angeles County.
Where to See It
Griffith Observatory: Public viewing each evening from one hour after sunset until the comet becomes too low to see (about an hour), through the 12-inch Zeiss refractor telescope on the observatory roof and through portable telescopes set up on the lawn. Call (213) 664-1181.
Valley College: “Star party” Saturday at a location east of Lancaster, free and open to the public. Call 781-1200, Ext. 335.
Los Angeles Sidewalk Astronomers: “Star party” Saturday at dusk at a location in Canyon Country. Call 841-0548.
Griffith Observatory Site: https://www.GriffithObs.org.
Hale-Bopp Comet Site: https://www.halebop.com
Jet Propulsion Laboratory Site: https://www.jpl.nasa.gov/comet/
Great Comets
Halley’s Comet
First recorded sighting: 1682
Period of orbit in years: 76
*
1910-I Comet
First recorded sighting: 1910
Period of orbit in years: 4 million
*
Comet Mrkos
First recorded sighting: 1957
Period of orbit in years: 13,200
*
Comet Ikeya-Seki
First recorded sighting: 1965
Period of orbit in years: 880
*
Comet Bennett
First recorded sighting: 1969
Period of orbit in years: 1,680
*
Comet West
First recorded sighting: 1976
Period of orbit in years: 500,000
*
Comet Hale-Bopp
First recorded sighting: 1995
Period of orbit in years: 2,380
*
Comet Hyakutake
First recorded sighting: 1995
Period of orbit in years: 14,000
Sources: Griffith Observatory; World Book Encyclopedia.
Researched by JULIE SHEER / Los Angeles Times
